_Growth, Manufacture and Distribution_
WHAT SUGAR IS
Among the many varieties of sugar the most important are the sucroses
and the glucoses. They form a natural group of substances, chiefly of
vegetable origin. Chemically considered, all sugars are carbohydrates,
that is to say, bodies composed of three elements: carbon, hydrogen and
oxygen. Sucrose contains twelve atoms of carbon, twenty-two atoms of
hydrogen and eleven atoms of oxygen.
Apart from sucrose, which is usually cane and beet sugar, the variety
most generally met with is dextrose—one of the glucoses. It possesses
less sweetness than sucrose and differs from the latter in chemical
composition. As an example: dextrose is found in the raisin in small
grains. It also occurs in other fruits and is the result of the inversion
of sucrose.
Glucose enters largely into the manufacture of candy, being particularly
necessary in the preparation of soft filling for creams, as a certain
amount of it added to cane-sugar syrup prevents crystallization.
Sucrose is derived from sugar cane, maple sap, sorghum and the sugar
beet. It is a solid, crystallizing in the form of monoclinic prisms,
generally with hemihedral faces, which are colorless, transparent, have a
sweet taste, a specific gravity of 1.6 and a melting point of about 320
degrees Fahrenheit. It is soluble in about one-half its weight in cold
water, and in boiling water in almost all proportions. It is practically
insoluble in alcohol, turpentine, ether, chloroform and similar fluids.
The crop of 1914-15 showed a world’s production of 18,409,016 long tons
of sugar, and in the chapters relating to the history of sugar will be
found a statement setting forth the amount produced by each country.
The total was derived about one-half from cane and one-half from beets,
produced as follows:
CANE BEET
Total in America 5,017,375 660,236
” Asia 4,268,618
” Australia and Polynesia 348,408
” Africa 523,788
” Europe 7,376[4] 7,583,215
---------- ---------
10,165,565 8,243,451
Sugar cane, described in botany as _Saccharum officinarum_, is a
giant-stemmed perennial grass that grows from eight to twenty-four feet
long. When ripe it produces at the top of its stalk a large feathery
plume of flowers of a gray inflorescence called the “tassel,” which is
from two to four feet in length.
There are many kinds of cane, all of which are regarded as varieties of
one species, although some botanists have raised a few to the rank of
distinct species. The cultivated types are distinguished by the color
of the internodes, yellow, red, purple or striped, and by other general
characteristics.
[Illustration: SUGAR CANE—SHOWING EYES OR BUDS]
The stem of the cane is solid, with joints at intervals of three to six
inches. In diameter it ranges from one to two and a half inches, and is
unbranched, bearing in its upper part numerous long, narrow grass-like
leaves, arranged in two rows. The leaves spring from large sheaths
around the joints, and have a more or less spreading blade from three to
five feet in length and two inches or more in width. The pith, of open
cellular structure, contains the sugary juice. The tops, which contain
but little sugar, are not crushed, but are used for seed, as the plant
germinates from the eyes, or buds, which grow on the stem around the
joints. Practically no cultivated cane is propagated from its seed.
The roots that remain in the ground after the cane is harvested throw
up fresh canes or ratoons for many seasons, after which replanting is
necessary. Hawaiian growers do not count on ratoons for more than a few
crops, whereas in Cuba this process can be repeated for many years.
As a rule, sugar cane consists of about eighty-eight per cent of juice
and twelve per cent of fiber, the juice content varying from time to
time, both as regards quality and amount. The quantity of the juice
pressed from the cane determines the efficiency of the extraction, while
quality is the main factor when the result of subsequent manufacture is
under analysis.
It is difficult to arrive at a fair average of the composition of the
juice of the cane, as it varies in different countries, on different
plantations in the same country, and at different periods in any one
year. The following is an approximation:
Water 80.8 per cent
Sugar 16.4 ”
Invert sugar 1.98 ”
Organic non-sugar .54 ”
Ash (mineral matter) .28 ”
THE GROWING OF SUGAR CANE
Sugar cane grows almost exclusively in the tropical belt, extending from
twenty-two degrees north to twenty-two degrees south latitude, where
the three essentials for its successful culture, viz., fertile soil,
hot sunshine and plenty of moisture, are present. It flourishes in the
islands of the Pacific ocean, particularly in the Hawaiian group, in
Cuba, Mexico, Central America, the islands of the East and West Indies,
Australia, China, India, along the shores of the China sea and the Indian
ocean, and in certain parts of Africa and South America. In the low
latitudes of the temperate zone it is grown with only fair success.
Owing to peculiar climatic conditions, sugar cane has been raised in
southern Spain for generations, notwithstanding the fact that the
provinces in which the sugar cane is grown lie, roughly speaking, between
thirty-six degrees and thirty-eight degrees north latitude. The Gulf
Stream is no doubt largely responsible for this phenomenon. The quantity
of sugar produced in Spain, however, is small, the crop of 1914-15
amounting to less than 8000 tons.
Sugar cane thrives best in a moist, warm climate, with moderate intervals
of dry, hot weather, and plenty of water for irrigation. It requires
marly soil, free from saline ingredients. As a rule, it is raised on the
lowlands, where the temperature is highest and where it is easy to bring
water for irrigation. In Hawaii it takes eighteen months to ripen, and
“tasseling” occurs about thirty days before it is ready to be cut. In
Louisiana and Texas, because of the short seasons, cane is harvested in
from nine to ten months from the time of sprouting, and, consequently,
before it has attained maturity. In Cuba it is cut in twelve months,
whether it is ripe or not.
[Illustration: ROOTS OF SUGAR CANE]
[Illustration: JUNGLE-LIKE VEGETATION OF CANE FIELD]
As the scientific culture and manufacture of sugar is probably further
advanced in the Hawaiian islands than in any other part of the world, a
description of the industry as carried on there will serve to illustrate
the intensive cultivation and scientific methods of the present day.
The Hawaiian islands are situated in the Pacific ocean, in latitude
nineteen degrees to twenty-two degrees north and in longitude one hundred
and fifty-four degrees to one hundred and sixty-one degrees west, and are
free from the destructive hurricanes of the East and West Indies. They
are of volcanic formation and, as a rule, their centers are mountainous,
in some instances reaching an elevation of nearly fourteen thousand feet.
During the ages, torrential rains carried volcanic ash from the mountains
toward the sea, near which it was deposited, thus forming alluvial areas
of vast richness around the circumference of the islands. Parts of
some of the islands are fringed with coral reefs, barriers that retain
the washings from the mountains. In these low-lying areas the soil is
extraordinarily fertile, and it is on such ground that the most generous
crops are raised.
The soft, warm trade winds that blow from the northeast become laden
with moisture as they sweep over the ocean; when they strike the cold
mountain peaks the moisture condenses immediately into copious rains.
The precipitation in some places reaches the astounding total of three
hundred inches per annum. The rain water is conserved and, when needed,
is carried to the various plantations by immense irrigation ditches.
In this tropical region there is an abundance of sunshine, accompanied
by humid heat, exactly the conditions needed. It required only man’s
ingenuity to utilize what nature so lavishly provided.
The commercial cultivation of sugar cane in these islands began about
1850, when a few hundred tons of raw sugar were produced, but the methods
of husbandry and manufacture were crude. Time and experience worked great
changes, until in 1914-15 the crop of raw sugar totaled 646,448 tons of
2000 pounds each.
For many years past the sugar planters have maintained in Honolulu an
experimental station that is the marvel of the agricultural world. The
bulletins issued by it are recognized as authoritative, and are read with
interest in every sugar-producing country.
The most important features of the work carried on at this station are:
1. SOIL ANALYSIS
Skilled chemists examine the soils of the various plantations and, when
occasion demands, advise the planter what necessary element is lacking,
as well as how to obtain and apply it. A few years ago this branch
of the work was considered highly important. Recently, however, the
agriculturists have been depending more upon well-defined systems of
experimentation. Each plantation has on its own lands plots of ground on
which different methods of culture are tried and on which various kinds
of fertilizer are used. Experiments are also made to determine the exact
amount of water needed for irrigation. Particular attention is paid to
seed cane, and a number of types of it are planted in order to obtain
seed that will produce stalks that grow rapidly, yield a large tonnage
per acre, contain a maximum amount of sugar, and have a high resistant
power against disease and insect pests. The success attending this
practical experimental work is such that soil analysis is being relegated
to second place.
2. ENTOMOLOGY
A staff of trained experts assiduously study the insect life and eagerly
watch for harmful, troublesome pests, which in the past have wrought
great damage. It is their duty to find the means of eliminating these
pests, and this they usually accomplish through the skillful use of
insect parasites.
3. PATHOLOGY
The pathologists attached to the station supplement the scientific labors
of the chemists and the entomologists by prescribing for any disease that
may attack the cane. Plant life is subject to as many ills as the human
family, and the work of these specialists in restoring health to ailing
cane is of the highest importance.
To fully illustrate the character and scope of their work, a particular
instance for each department may be cited:
A certain planter found that the amount of sugar obtained from his cane
was decreasing yearly, though he could see no good reason for it. The
land looked right; he ploughed deeply, harrowed well, kept the weeds
down, gave the cane plenty of water, could find no reason to complain
of climatic conditions, but still did not get satisfactory results.
Finally the head of the experimental station was consulted and an
agricultural chemist was sent to the plantation. This chemist, after
careful investigation, took samples of the soil from various parts of
the land; these were analyzed and the source of the trouble was found to
be the lack of potash. Just here it may be explained that when the same
crop is taken from the land many years in succession, without adequate
fertilization, some of the essential properties of the soil become
exhausted. Speaking generally, these are lime, soda, potash, phosphates
and nitrogen. In this particular instance, as has been said, the land
had been gradually drained of its potash. The experimental station
recommended the planter to scatter a certain fertilizer over his fields.
This advice was followed and the next crop showed remarkable improvement,
the yield of cane and sugar per acre being greater than ever before.
At one time the sugar industry of the Hawaiian islands was threatened
with annihilation by a little insect called the “leaf-hopper.” The harm
done by this pest was so enormous that one plantation having an average
yearly crop of 19,000 tons was so severely affected that the yield
dropped from 19,000 to 12,000, and then to 3000 tons in three successive
crops. All the plantations on the islands suffered to a greater or lesser
extent, and the entire sugar industry of Hawaii was jeopardized.
The hoppers punctured the stalks and leaves of the young cane, and in the
holes thus formed laid their eggs by thousands. When the young hoppers
hatched out, they fed on the juices in the stalk and in the leaves,
thus destroying the leaves and depriving the cane of its protection and
principal means of absorbing nourishment from the air.
As soon as the leaf-hopper by its ravages made itself known in the
islands, the entomologists were consulted, and they were confronted
with the task of studying the life and habits of the hopper for the
purpose of finding, if possible, some other insects that would attack
and exterminate it. It is well known to entomologists that every insect
pest has natural enemies; the vital question in this case was—what were
the natural enemies of the leaf-hopper and where were they to be found?
Obviously, too, the problem was to discover insectivorous enemies that
would not themselves attack the cane after they had destroyed the hopper.
After careful investigation it was concluded that the leaf-hopper had
been introduced in Hawaii in new varieties of seed cane imported from
Australia, and, as the hopper was not doing material damage on the
plantations in Australia, the inference was that it must be controlled
there by its natural enemy. The chief of the Department of Entomology
was sent to London. There in the archives of the British Museum he found
a full description of the leaf-hopper and that its native habitat was
Queensland, Australia. On his return to Hawaii, entomologists were sent
to Australia and the search for the enemy of the hopper began.
[Illustration: LEAF-HOPPER (GREATLY MAGNIFIED)]
[Illustration: SUGAR CANE]
For weeks the entomologists virtually lived in the cane fields,
undergoing extreme privations, but at last their faithfulness was crowned
with success. Several species of parasites that kept the Queensland
leaf-hopper in check were discovered, and later on more were found in the
islands of Fiji. These tiny creatures as a rule were invisible to the
naked eye and could only be seen with the aid of a powerful magnifying
glass. All of these insects were parasites either of the leaf-hopper or
its eggs. Two of them were particularly efficacious. One, quicker in
movement than the hopper, caught it unawares and attached itself to the
hopper’s body much in the same way that a mosquito does to a human being.
After catching it, the parasite would sting the hopper and lay an egg in
its body. In a few days a young parasite was hatched from the egg, and
so ravenous was this young insect that it devoured the hopper in a short
time and then sought a fresh victim in which to lay its eggs.
The other insect was even more effective. It liked the hoppers’ eggs and
for a long time found plenty in Hawaii to stay its appetite. As soon as
the leaf-hopper laid its eggs in the cane, this particular insect would
appear and lay its eggs in the eggs of the leaf-hopper. When the little
enemies hatched out, they fed on the hoppers’ eggs and in turn laid
their eggs in the eggs of the hopper. It came to pass that the hoppers,
attacked by the parasite on the one hand and by the enemy on the other,
rapidly dwindled in number until only a few remained, and these not
enough to do material damage. As the hoppers and their eggs diminished,
so did the parasite and the enemy, for the latter could live on insect
food only.
How the scientists collected these tiny animalcules, kept them alive,
transported them thousands of miles across the ocean, bred them in
Hawaii and saved the Hawaiian sugar industry, reads like a romance.
The study of entomology is extremely interesting and the every-day
business man rarely understands its importance. The finding, breeding
and distribution of parasites of insect pests vitally affects the
world’s food supply. The entomological name of the leaf-hopper family is
_Hemiptera_, and Dr. Sharp, an authority on the subject, has said: “There
is probably no order of insects that is so directly connected with the
welfare of the human race as the hemiptera; indeed if anything were to
exterminate the enemies of hemiptera, we ourselves should probably be
starved in the course of a few months.”
It has been estimated by competent authority that the damage done in
the world each year by the hemiptera, in spite of all their parasites,
is conservatively $600,000,000. Were it not for the parasites, it would
only be a year or two at most before every green leaf and spear of grass
would disappear from the face of the earth. The direct influence of the
practical application of this science to the production of sugar is
readily apparent.
Pathology is almost equally important. In former years when cane failed
to grow strong and sturdy and did not yield much sugar, the planter
usually attributed the difficulty either to lack of water, poor soil,
cool weather, too much rain or insufficient cultivation of the field by
his manager, when in fact the trouble was due to none of these causes. He
would personally oversee the operations of the following year, but with
no better results.
[Illustration: EXPERIMENT STATION]
[Illustration: PLANTATION SCENE IN HAWAII—LIGHT-COLORED FOLIAGE IS SUGAR
CANE]
When the roots of the cane became matted, stuck together and turned
black, when a thick gum exuded from the stalk and leaves, preventing the
plant from drawing proper nourishment from the air, it was thought that
these troubles arose from climatic or local conditions, while in reality
the plant was sick and needed a doctor. Today, under the new régime,
whenever the plant shows any symptoms of ill-health, the pathologists
are called in to eradicate the disease by scientific treatment.
Insect pests and plant diseases are generally brought into a country
through planters sending to other cane-raising countries for new
varieties of cane for seeding purposes that they think may produce more
sugar than their own. Great trouble and heavy loss have been occasioned
in this way and, as a consequence, the United States government has
established a strict quarantine, allowing plant life to be landed only
after rigid examination and when it is clear that no danger exists.
Another example of the work of the entomologists may be of interest:
During the visit of a well-known Hawaiian to Mexico many years ago, his
attention was attracted by a beautiful shrub that he thought would make
a splendid hedge around his home. It grew about five feet in height and
its foliage was of a rich green, with a brown, red and yellow flower.
The slips he brought to Honolulu thrived wonderfully and cuttings of
the plant were taken to the other islands for a like purpose. Wherever
planted it grew amazingly fast. It quickly spread over the hillsides and
became so dense that cattle could not penetrate the thickets formed by
it. It made valueless large areas of land that formerly had been used for
the pasturing of cattle and plantation stock, and reduced the grazing
area at an alarming rate. Land that adjoined the plantations and that
in the course of time became needed for plantation purposes was also
over-run by it.
The curtailment of the grazing lands and the increased cost of clearing
were so great that the entomologists were finally sent for and asked if
they could not eradicate the trouble. After a careful investigation they
went to Mexico, whence the lantana, as the shrub is called, had come. On
their return journey they brought back with them a fly. The fly laid its
eggs in the bud of the lantana, and when the young flies were hatched
they fed upon the lantana seeds. The flies multiplied rapidly and soon
made away with the seeds, thus preventing the shrub from spreading any
further. When it was once cleared from the land or the plantation it did
not reappear.
These illustrations demonstrate the fact that the culture of sugar cane
involves a constant struggle between science and unrestrained nature.
As a rule, Hawaiian sugar plantations are located close to the seacoast,
between it and the base of the mountains. The lands slope gently toward
the sea, thus insuring good drainage and easy application of water for
irrigation. Most of the cane is grown on land less than five hundred feet
above sea-level, although in a few rare instances it is cultivated at
an elevation as great as three thousand feet. Parts of the leeward side
of the islands, where it is extremely dry and hot, and where the cane
thrives best, depend entirely on irrigation, the water being brought to
the plantations by ditches or pumped from wells. On the windward side
of the island of Hawaii, where the rainfall is abundant, irrigation is
unnecessary except during very dry periods.
In cultivating, the ground is turned with steam ploughs to depths up to
twenty-four inches. These ploughs are operated by powerful engines that
work in pairs, one on each side of a field, usually from one thousand
to fifteen hundred feet apart. One engine pulls a gang-plough across
the field and the other draws it back. By this method the rich soil is
thoroughly loosened and a wonderful vegetable growth results. Ordinarily
in California the farmer ploughs only from four to six inches deep.
[Illustration: STEAM PLOUGH]
[Illustration: PLANTING CANE]
After the lands are ploughed and harrowed and all the weeds turned
under, double mould-board ploughs are used to make the furrows in which
the seed is planted. The furrows are not like those made for planting
potatoes, but are about five feet apart and eighteen inches deep, each
furrow and hill being symmetrical. They follow the contour of the land
so that the irrigation water will fill the furrow and remain there until
it is absorbed by the soil and penetrates to the cane roots. At regular
intervals of about thirty-five feet, lateral ditches are cut, from which
there is an entrance into every furrow. These lateral ditches deliver the
water from the main ditches to the various parts of the fields. The land
is now ready for the seed.
Meanwhile, the harvesting of the ripened cane in other fields is going
on. As the laborers cut the cane, they top it, that is to say, they cut
off about twelve inches of the upper part of the solid stalk. Sugar cane
resembles bamboo, in that it is cylindrical in shape and divided every
few inches into sections by rings or joints. In every joint there is a
bud or eye, from which a shoot of cane will sprout, if properly planted
in the ground and watered.
These tops, always cut from untasseled cane, contain very little sugar.
They are carried to the newly prepared field and placed in rows in the
furrows, end to end, lengthwise, the ends overlapping a trifle in order
to guard against blank spaces in the growing cane. They are then covered,
according to the season, with one to one and a half inches of earth,
and the water is turned in until the furrow contains from three to four
inches of water. Between six and ten days afterward, the little green
cane shoots appear above the ground. From this time forward continuous
irrigation and cultivation, together with proper fertilization, are
required until the cane matures.
Planting usually begins in March and continues until September, sometimes
later, and the cane ripens one year from the following December.
Growing cane should be watered every seven days, and the amount of water
used for this purpose is enormous. For example: a plantation producing
thirty-five thousand tons of sugar per annum needs twice as much water
per day as the city of San Francisco.
The appearance of growing cane is much like that of Indian corn. The
whole field area is covered with a dense, jungle-like vegetation of
brilliant green. The leaves are long and narrow and hang in graceful
curves. The cane grows so thick that it is almost impossible to crawl
through it, and so seldom do the sun’s rays penetrate to the ground that
rapid evaporation of the irrigation water cannot take place, hence the
cane gets the full benefit of the moisture.
In certain varieties of cane, the great weight of the juice in the stalks
causes them to bend, droop and take fantastic shapes. Sometimes they lie
on the ground with the ends turned upward, and in fields where the stalks
grow to a length of twenty-four feet, the average height of the tops
above the ground is not over twelve feet. In other kinds the stalks stand
straight up to a height of from eight to fourteen feet.
The production of cane per acre varies in different countries and in
different parts of the same country, according to the character of the
soil, climatic conditions, care and attention, use of fertilizer and
amount of rainfall or irrigation. In Hawaii it ranges from twenty to
eighty-five tons, and the amount of sugar obtained per acre runs from two
and one-half tons to twelve tons, the average being about five tons.
Broadly speaking, lack of a normal amount of cane per acre, lack of
sugar in the cane, or the prevalence of disease, is primarily due to
an unsanitary or unsuitable condition of the soil. This can usually be
corrected by proper cultural methods, such as adequate aeration of the
soil, the turning under of the cane tops and leaves, application of lime
and suitable combinations of fertilizing ingredients. Fundamentally,
cane requires a well-aerated, moist, alkaline soil and a fertilizer
in which the nitrogen content is high and in excess of the potash and
phosphoric acid. It is found that nitrate of soda, when applied alone or
in combination with potash and phosphoric acid, produces a very strong
growth. The proper sanitation of the soil tends to promote the beneficial
bacterial action so essential to the growth of the cane.
[Illustration: IRRIGATION DITCH—SHOWING TUNNEL]
[Illustration: IRRIGATION DITCH]
In December and January the cane tassels or flowers, which indicates that
it has about reached maturity and is ready for cutting. Thenceforward
very little irrigating is done, as additional water applied at this time
might retard ripening, which would mean a reduced amount of sugar stored
up in the cane.
It is interesting to note that while the cane is growing and in an unripe
state, there is no discernible sucrose or pure sugar in it. As the
ripening process goes on, the content of the cane juice is changed by
the action of the sun’s rays, and the amount of sucrose as determined by
polariscopic test shows when the time for harvesting is at hand. Nature’s
operation in thus changing glucose or invert sugar into sucrose or pure
sugar cannot be accomplished by any human means.
The harvesting then begins and continues until the end of July or August.
Usually the field is set on fire before cutting. On account of the great
amount of moisture or juice in the cane, the stalks do not burn, but the
leaves are thoroughly consumed. This operation eliminates a good deal of
leaf material that is not only useless, but which, if sent to the mill,
would increase the cost of crushing, besides absorbing a certain quantity
of the juice expressed from the cane.
Formerly men stripped the leaves from the cane in the fields, but it was
a difficult matter to accomplish such work, and the cost was heavy. An
accident changed the method of doing this work. A field took fire and it
was found that while all the leaves were consumed, little or no damage
was done to the stalks provided they were cut promptly and sent to the
mill to be crushed. The practice of burning has since become general,
although the advisability of continuing it is now being given very
careful study.
Burning eliminates the arduous labor of stripping, and no doubt does away
with many harmful insects and fungi, but at the same time it destroys the
enemies and parasites of these insects and this loss is severely felt.
Another disadvantage of burning is that the nitrogen contained in the
cane leaves is liberated and not returned to the soil as would be the
case if the leaves were stripped and ploughed under. In the latter case
the leaves rot rapidly, add humus to the soil, help aeration, and improve
the sanitary condition, all of which tends to increase the yield of cane
per acre. From recent experience it is not improbable that burning will
be discontinued in the near future.
As soon as the field is ready, whether burned or not, the laborers go in
to cut the cane. A long, heavy knife is used. The cutter grasps the stalk
and drives the knife into it, severing it just at the ground. He then
tops it, that is, he cuts off the upper part that contains no sugar, and,
to aid in subsequent handling, the long stalks are cut into convenient
lengths.
As the burning destroys the eyes or buds, certain fields are cut and
topped for seed before the burning takes place.
There are two general methods of transporting the cane to the mills.
One is by rail and the other by flumes. On the irrigated plantations
where water is never overplentiful, railroad tracks and locomotives are
invariably employed, while on the non-irrigated plantations, located
in districts where there are copious annual rains, V-shaped flumes are
extensively used. In some cases a combination of both systems is adopted
to advantage. From the upper lands where it is difficult to construct
railroads, the cane is flumed to a convenient point on the railroad
system, at a lower elevation, and delivered into cars, while the water is
conducted into ditches and used for irrigating the lower cane lands.
[Illustration: YOUNG SUGAR CANE]
[Illustration: RIPE SUGAR CANE—SHOWING TASSELS]
In the case of rail transportation, paths one hundred and fifty feet
apart are cut through the fields so that temporary railroad tracks may
be laid and cars run in and loaded on these tracks. The whole field is
then cut in the same way and the work continued until the entire crop is
harvested.
The loaders follow up the cutters. These men lay a strap on the ground
and pile the stalks on the strap until they have a bundle of cane
weighing from seventy-five to one hundred pounds. With a dexterity born
of long practice, they sling a bundle upon their shoulders and carry
it up an inclined runway to a railroad car not over seventy-five feet
away and dump it on the car. The cutting and loading are usually done by
contract, at so much per ton, and it is remarkable how proficient the men
become.
When flumes are used exclusively, much the same methods are adopted.
Paths are cut through the fields and in these paths are placed the flumes
which, like the temporary railroad tracks, are moved from time to time
as necessity demands. The mill is located at the lowest point on the
plantation and the flumes are placed so as to insure a good grade from
the cane fields on the uplands to the mill below. The flumes are either
carried on low trestles or run along the ground, but always at a height
which enables the laborers to throw the cane into them conveniently.
Water is turned into the upper end of the flume and, rushing rapidly
down, carries or floats the cane to the mill. Cane is flumed in this way
for distances up to seven miles at low cost and with satisfactory results.
The cars when loaded in the fields are made up into trains and hauled by
locomotives to the mill, which is generally located about the center of
the plantation, or at a point where most of the cane can be delivered on
a downward grade. Each car is carefully weighed on a track scale and the
exact quantity of its load of cane is ascertained and recorded.
For years past the planters have been offering large rewards for the
invention of a machine to cut and load the cane, but the old hand method
is still employed, although some experimental loading machines are
meeting with more or less success, but none are in common use.
The problems involved in cutting cane by machinery seem insurmountable,
and, while many devices have been tried, not one has proved successful.
After the cane is cut the first time, ploughs are sent through the fields
and a furrow is ploughed along each side of the stubs of the cane which
are left in place. This ploughing opens up the ground, aerates the soil,
and affords the irrigating or rain water a means of easy access to the
cane roots. The water tenders follow up the ploughs and the furrows are
filled with water, which is gradually absorbed by the old cane roots left
in the ground. In time new sprouts spring up from buds on the old stalks
of the cane and another growth begins. The second crop is called “first
ratoons” and, when cultivated for a single year only, it is designated
“short ratoons.” As a rule it does not yield as much sugar as plant cane,
but the saving in seed, in the preparation of the fields and in other
labor frequently makes up for the reduced amount of sugar. If allowed to
grow for two years, as is generally the case, it is called “long ratoons”
and produces proportionately more sugar. In the past a very large
percentage of the Hawaiian crop was planted with fresh seed every year
and but a small percentage ratooned. Nowadays, however, the tendency is
to ratoon the crop as long as the yield justifies, which in many cases is
from three to four times. In Cuba the cane when once planted is ratooned
for many years.
There have been specific instances in Hawaii where ratoons that have been
allowed to grow for two years (long ratoons) have shown a better yield
than the first planting. According to the best information, this is due
to the presence of poisonous matter in the ground, turned up for the
first time at the first planting.
[Illustration: CUTTING CANE]
[Illustration: LOADING CANE]
The object of all the ploughing, weeding, cultivating, fertilizing and
irrigating, is to produce a large number of strong, sturdy stalks of
cane, yielding a maximum amount of sugar. The sugar is contained in
solution in the sap or juice and the amount can be materially increased
by due care and attention.
As some of the elements which form the plant are absorbed from the air
through the leaves, favorable climatic conditions are essential to its
full growth and development. Proper fertilizers must be added to the
soil, and water applied regularly and in sufficient quantity.
Commercial fertilizers are used in Hawaii probably to a greater
extent than in any other country in the world. It is quite common for
plantations to use half a ton of fertilizer per acre per crop, and at
times as much as two thousand pounds per acre. The yearly fertilizer cost
per acre will probably average twenty-five dollars.
As it takes eighteen months for a crop to mature in Hawaii, it will
readily be seen that the plantation area must be at least double that
used for any one crop. While one crop is being harvested, another crop
is in the ground growing. As soon as the cane is cut, the lands are
immediately prepared for replanting or ratooning, as the case may be.
During certain periods each year, usually in June and July, a visitor on
an Hawaiian plantation can see one crop growing, one being harvested and
one being planted.
From the foregoing it will be seen that the harvesting begins in December
and ends in July or August. The planting begins from March to June and
usually ends in September, according to plantation conditions and whether
or not the land is irrigated.
THE MANUFACTURE OF RAW SUGAR
The details of the manufacture of raw sugar from cane and of sugar from
beet roots differ, but there are several processes common to both. The
operations necessary for making raw cane sugar are as follows:
1. The extraction of the juice.
2. The purification of the juice.
3. The evaporation of the juice to syrup point.
4. The concentration and crystallization of the syrup.
5. The preparation of the crystals or grains for the market by
separating them from the molasses.
Every mill has an extensive laboratory where skilled chemists are
constantly engaged in sampling and analyzing cane, raw juices, syrups,
sugars and molasses. In fact the chemical work is a most important
feature in the raw-sugar house, beet-sugar factory or refinery. The
superintendent should be an expert chemist, as the proper recovery of
the sugar from the cane and beet juices is wholly dependent upon the
technical control of manufacturing processes.
EXTRACTION
After passing the scales, the cars containing the cane are switched
alongside the carrier which feeds the cane into the mills. Before the
cane is unloaded, however, samples are taken from each car and sent to
the laboratory, where they are carefully analyzed. The amount of sugar
present is ascertained, as well as the quantity and quality of the juice
in the cane. It is, however, impossible to get a fair average sample of
the cane in this way, and therefore the efficiency of the mill work is
determined on the basis of an analysis of the juice and the fiber after
it has passed through the crushers.
[Illustration: TRAIN-LOAD OF CANE READY FOR THE MILL]
[Illustration: A MODERN MILL]
The carrier just referred to is a wide slat conveyor, running alongside
the railroad tracks in the yards to a point directly over the first set
of crushers. The cane is taken from the cars by a mechanical unloader,
the arms of which reach out and with distended fingers pull the cane
stalks off and land them on the slow-moving carrier, which takes them
onward and upward to the crusher.
The crusher consists of two large rolls, with immense interlocking,
corrugated teeth on the circumference of each. These rolls are set close
together, and the cane passing through is broken into short pieces and
matted to an even layer. The juice squeezed out by this preliminary
crushing runs through a metal trough into a large receptacle known as the
juice tank.
From the crusher the mat of cane passes to the mills proper. These mills
consist of from nine to eighteen rolls, about thirty-four inches in
diameter and seventy-eight inches long, arranged in groups of three, set
in the form of an isosceles triangle, one above and two below, one set
following the other in a direct line. The lower rolls are parted enough
to allow the expressed juice to fall through them, while the half-crushed
cane is carried over by means of an iron bar called the returner. The
faces of the rolls are more or less roughened, or grooved, so as to draw
the cane through and give a better crushing action. They are turned
slowly by powerful engines, which transmit the power to each set of rolls
through a system of gears. The rolls are forced together by hydraulic
rams exerting a pressure of from four hundred to six hundred tons. It is
this tremendous pressure that squeezes the sugar-bearing juice out of the
cane.
From the crusher the matted cane passes through the first set of rolls,
where a large percentage of the remaining juice is liberated. This is
caught in a metal trough and, after passing over a fine screen to remove
the small pieces of cane, runs to the juice tank. The cane passes through
the second set of rolls, thence to the third set, and so on to the end
of the mill. In front of the last set of rolls, hot water is sprayed on
the cane to soften the fiber and dilute the remaining juice, thus aiding
the final extraction. The adding of hot water is termed _maceration_.
By the time the cane has passed through the last set of rolls, all the
economically recoverable juice is out of it and delivered into the juice
tank, with the exception of the juice and maceration water from the last
set of rolls, which is always returned to the preceding set of rolls for
maceration purposes. The juice or maceration water coming from the last
set of rolls contains very little sugar, and the object is to secure
greater concentration by using it for double maceration instead of adding
that much additional water which would have to be evaporated later on in
the process.
In well-designed, modern mills, with cane carrying not over twelve per
cent of fiber, more than ninety-eight per cent of the sugar in the cane
is extracted, the remainder being left in the fiber. This is almost
perfection today. What it will be tomorrow no one can say.
The fibrous, woody part of the cane, or bagasse as it is called, is
comparatively dry as it leaves the last rolls. It is conveyed from the
mills to the boiler house on a wide slat conveyor, and fed directly into
the furnaces under the boilers that generate the steam for power and
boiling purposes. A modern raw-sugar mill requires practically no other
fuel than that obtained as a by-product from the crushing of the cane.
The boiler plant is usually of large capacity, as a great deal of steam
is required to drive the engines that run the crusher, the rolls, the
electric lighting system, the pumps and other machinery. Besides, a large
amount is needed to evaporate the water in the juice and to boil and dry
the sugar. The ashes from the furnaces are returned to the fields as
fertilizer, so that very little is lost.
[Illustration: CANE CARRIER AND MECHANICAL UNLOADER]
[Illustration: ANOTHER TYPE OF CANE UNLOADER]
PURIFICATION
The juice as it comes from the mills contains impurities such as dirt
from the fields, small pieces of cane stalks and other foreign matter,
besides salts, gum, wax and albumen. It is necessary to remove as many of
these substances as possible, and this is where the chemist’s work begins.
So long as the juice is confined in the living cells of the cane it does
not quickly ferment, but when liberated it rapidly undergoes such change.
Therefore no time is lost in arresting this action. The juice is pumped
to the top floor of the mill and there a solution of milk of lime is
added in sufficient proportions to neutralize the acidity. The mixture is
then heated in closed tanks under pressure to 215 degrees Fahrenheit. The
heat causes the lime to combine rapidly with the gums and salts in the
juice, and the albumen to coagulate.
The hot juice is then run into large settling tanks, where the insoluble
solids and the albumen sink to the bottom, carrying with them vegetable
and other matter suspended in the juice. Certain foreign substances of
light specific gravity float to the surface in the form of scum.
After settling for a time the clear juice is drawn off and the scum, mud
and cloudy liquor left in the tank. As a vast amount of liquor must be
handled every hour, it is not practicable to have tank capacity great
enough to admit of the liquor standing a sufficient length of time for
every particle of foreign matter to settle, so as an adjunct to the
settling tank, filters are used. These are cylindrical iron tanks, packed
tightly with ordinary wood fiber, known as excelsior. The juice is
conducted to these filters, and as it percolates through the excelsior,
practically all of the remaining foreign matter is caught and retained
in the fiber. The clear juice is then run to the receiving tanks for
the evaporators and the mud and scum that remain are drawn off into mud
tanks, where more lime is added and the mass stirred up. Finally it is
delivered to the filter presses, where the mud and other impurities
are taken out and the clear liquor containing sugar is sent to the
evaporators.
Another method for cleaning, called “precipitation in motion,” is to
carefully lime the juice and then heat it in closed vessels and under
sufficient pressure to carry it through a pipe to large insulated
settling tanks.
These settling tanks, usually of sheet steel, are made in the form of
truncated cones with conical bottoms, the small diameter of the tank
being at the top. Suspended in the center is a vertical cylinder somewhat
less in diameter than the upper part of the tank. This cylinder extends
downward about eight feet to a point opposite the largest diameter, which
makes the area between the circumference of the suspended cylinder and
the tank at that point very much greater than the area of the cylinder
itself. This difference in area is necessary to retard the flow of the
juice and allow the sediment, mud and insoluble solids to be deposited at
the bottom of the tank.
The juice is delivered by a pipe into the top of the cylinder which
projects a few inches above the edge of the surrounding settling tank. It
passes slowly down the central passageway, turns at the bottom, where its
speed is materially slackened, and goes out through a pipe line connected
to the side of the tank just below the upper edge.
There are several other methods in general use, but in all of them the
principle of settling, upon which the separation or cleaning depends,
is the difference in specific gravity between the juice and the dirt. A
high and even temperature should be maintained by preventing radiation,
as lowering the temperature would increase the specific gravity and
viscosity of the juice without increasing that of the dirt in equal
proportion.
[Illustration: TWELVE-ROLLER MILL]
[Illustration: MODERN CRUSHING PLANT—TWO FIFTEEN-ROLLER MILLS AND
CRUSHERS. CAPACITY, ONE HUNDRED AND FIVE TONS PER HOUR]
There are many different types of filter presses, but those at present in
general use are long, oblong machines, set horizontally on the floors,
with layers of corrugated iron plates, covered with canvas sheets,
between which are hollow frames so arranged that the juice will pass from
the hollow frames through the canvas to the corrugations in the plates.
In passing through the presses under pressure the sediment, scum and
other impurities are caught on the canvas sheets and the clear juice
passes through the canvas, down the corrugations and out through small
holes in the plates controlled by valves on the outside of the presses,
from whence it runs to the evaporator tanks. The sugar in the mud caught
in the hollow frames is washed out of the mud with water and is sent to
the evaporator, while the mud itself is finally returned to the field, to
be used as a fertilizer.
The clarified juice from the settling tanks, filters or presses, is
light brown in color, but is thin and watery, and must now be reduced to
syrup point. All the suspended impurities have been removed, but some
impurities in solution and the original coloring matter still remain.
Some of these foreign substances are subsequently eliminated during the
process of crystallization in the vacuum pans described later on.
The object to be attained in a raw-sugar house is the production of a
sugar containing ninety-six per cent of sucrose, and there is little or
nothing to be gained by carrying the process of manufacture beyond the
stage that insures such result.
The final extraction of all the impurities and the conversion of the
impure raw into pure white granulated sugar is the work of the refiner,
which is dealt with in a subsequent chapter.
From the time the juice leaves the cane until it is crystallized it is
kept at a high temperature, as cold juices or syrups are viscous and run
slowly. High temperatures kill germs, prevent fermentation and expedite
manipulation.
EVAPORATION
Under ordinary atmospheric pressure at sea-level, water boils at a
temperature of 212 degrees Fahrenheit and sugar juice at a few degrees
higher, according to its density. This temperature if long applied to
sugar juice would tend to burn and destroy the sugar, but the juice can
be heated to 250 degrees for a short time without deterioration.
The clarified juice contains about eighty-five per cent of water and
fifteen per cent of solid matter. A large proportion of the water must
be removed by evaporation. To accomplish this under ordinary atmospheric
conditions would require heat increasing from 212 degrees Fahrenheit,
as the solution increased in specific gravity above the standard of
pure water. This would require a large amount of fuel, and the juice
would also be more or less adversely affected by long maintenance of
comparatively high temperature.
To obviate these conditions the juice is boiled in a multiple evaporator,
the invention of Norberto Rillieux, whose first construction in New
Orleans in 1840 was a double effect horizontal submerged tube apparatus
which has since undergone many changes and improvements. The theory
of evaporation _in vacuo_ was extended to two or more cells or vacuum
bodies, using the steam or vapor from the first to heat the juice or
syrup in the second and so on. At the present time the quadruple effect,
or four-cell evaporator, is most commonly in use, although sextuple
effects are not rare. The ordinary practice is as follows:
The juice enters cell No. 1 and covers the heating tubes, to which is
admitted sufficient steam—generally exhaust from the engines—to cause the
liquid to boil. The steam or vapor liberated from this first boiling is
conducted through the vapor pipe directly into the heating tubes of cell
No. 2, while the juice from cell No. 1 is passed into the second, or cell
No. 2, and surrounds the heating surfaces which contain the hot vapor
given off from the same juice in cell No. 1.
[Illustration: DELIVERING BAGASSE TO FIRE-ROOM]
[Illustration: GENERAL INTERIOR VIEW OF MODERN RAW-SUGAR MILL]
As there is little or no pressure above the liquid in the first cell, the
juice boils at from 215 degrees to 220 degrees Fahrenheit. By maintaining
a vacuum of five inches in the second cell, the temperature at which the
liquid will boil is reduced to 203 degrees, and the vapor from cell No.
1 is hot enough to boil the juice in cell No. 2 without any addition of
heat. The vapor from cell No. 2 in the same way enters the heating tubes
of cell No. 3, while the juice entering this cell is exposed to a vacuum
of fifteen inches, which reduces the boiling temperature to 180 degrees,
so that the difference of 23 degrees between the conditions of cell No.
2 and cell No. 3 causes a third boiling and evaporation without any
additional steam being added.
A vacuum of twenty-six inches in the last cell, No. 4, brings the final
boiling temperature down to about 150 degrees. The vapor from this last
cell enters a condenser, where it is exposed to a spray of cold water,
is condensed and passes down a pipe not less than thirty-four feet long,
terminating in a water seal, and called the Torricellian tube, after
Torricelli, who discovered that mercury would rise thirty inches in a
tube while water would rise thirty-four feet with a perfect vacuum.
The juice in passing through these evaporating cells is boiled to a syrup
containing about thirty-five per cent of water and sixty-five per cent of
solid matter. It is pumped out of the fourth cell into the receiving tank
for the vacuum pan.
This quadruple system of boiling only requires about one-fourth the
amount of heat that would be necessary to do the same work in a single
vessel. As the evaporators operate continuously, a constant level of the
boiling liquid is maintained in each cell, the juice being drawn from one
to the other by increasing vacuum and controlled or regulated by means of
valves.
A powerful vacuum pump draws the air and other incondensable gases from
the condenser and maintains the vacuum, which is applied to the necessary
extent in each cell. The heating tubes are connected to drain pipes,
which remove the condensed vapors.
Vacuum, simply and concisely stated, is the absence of air or gas. It
is usually obtained by pumps which suck the air or gas out of closed
containers or pipes. No doubt many of the readers in their younger days
have sucked on the end of a bottle and were amused to find the bottle
hanging on the end of the tongue. It was the vacuum, or lack of air
in the bottle, which caused it to hang thus. The outside atmospheric
pressure (which at sea-level is fifteen pounds per square inch) was doing
its best to gain an entrance through the tongue into the bottle from
which the air had been extracted.
The pumps simply suck the air out of the containers or pipes and
discharge it through valves, in much the same way that the air was sucked
out of the bottle. It must be remembered, however, that in boiling water
or juice, the vacuum is being continually broken or reduced by the
liberation of air and gases from the juice, steam and condensing water.
This action must be overcome by the constant work of the vacuum pump.
To determine the amount of vacuum carried in any container, a small
mechanical contrivance, known as a vacuum gauge, is used. This, in its
simplest form, is a bowl of mercury with a long glass tube leading from
it. If the upper end of the glass tube is attached to the container
from which the air is to be drawn, the mercury in the tube will rise in
proportion to the amount of air extracted. When an absolute vacuum has
been formed, the mercury in the glass will stand at a height of thirty
inches.
[Illustration: FILTER PRESSES]
[Illustration: SET OF QUADRUPLE EVAPORATORS]
In commercial operations a vacuum greater than twenty-eight inches is
seldom required, as this is sufficient for all practical purposes. The
degree of vacuum for any container can be varied easily by mechanical
manipulation, so that a vacuum anywhere from one to twenty-eight inches
may be maintained.
CONCENTRATION AND CRYSTALLIZATION
From the receiving tanks the syrup is drawn into the pans by a vacuum
ranging between twenty-five and twenty-seven inches. The pans are
large cast-iron or copper cylinders, standing in a vertical position,
with dome-like tops and conical bottoms, almost spherical in shape.
Leading from the top is a large pipe through which the vapors from the
boiling are drawn off and condensed. On the conical bottom is a large
valve, which may be opened when the boiling is finished to allow the
_massecuite_ (a French term meaning cooked mass) to drop out.
At regular intervals in the height of the pan there is a series of copper
coils, connected with a steam line at one end and a drain line at the
other.
The general principle involved in boiling sugar is the separation of
the sucrose contained in a solution from the impurities present in that
solution, and this is accomplished by evaporation and concentration
through the agency of heat. After the sugar is once formed in definite
crystals these crystals attract and appropriate the sucrose in solution
in the process of building up the crystal structure, while repelling or
excluding the impurities, so that, as a consequence, the latter remain
in solution. The crystals thus formed are subsequently removed from the
solution by means of centrifugal machines. Crystallization, whether in
a pure or impure solution, will proceed to only a certain extent, and
will only partially remove the sucrose from the solution in one boiling,
the limit of crystallization being governed by the amount and nature of
impurities present.
The process of boiling is begun by drawing some of the concentrated juice
into the pan and turning steam into the coils, which starts the boiling.
This is continued until the supersaturation is such that minute crystals
of sugar form or “grain out.” By properly timed admissions of fresh
concentrated juice, drawn into the pan by vacuum as before, the crystals
grow in size and at last the pan becomes filled with a mass of sugar
crystals of regular shape and size, immersed in a thick “mother liquor”
containing sugar and the impurities that were not removed by the filters
or settling tanks.
The size of the grain may be varied at will by the operator in charge,
who is known as the sugar boiler. After the grains are once formed, their
number (if the sugar boiler is an expert) does not increase, but the size
does, as the original grain continually builds up on itself from the
outside.
The question may be asked, why is all the moisture not boiled out in
the pan and the sugar dropped in a dry, crystallized state? There are
several reasons why such a course is impracticable; first, because the
impurities, which must be eliminated by crystallization and which are
carried off in the mother-liquor, would be boiled into the sugar and
make it unsalable; second, because to aid crystallization and prevent
scorching or burning on the hot steam coils the mass must be kept in
active circulation during the boiling process, or, long before all the
moisture could be driven off, a large part of the contents of the pan
would be burned on the coils; and third, even if it were practicable to
boil the contents down to a solid state, the grains would stick to each
other and become one solid mass, which would have to be removed from
the pan with bars, picks or chisels. Enough moisture, or rather liquor,
is left in the mass to enable it to flow from the pan by gravity. This
liquor, with the impurities it carries, is subsequently removed from the
sugar by a drying or separating process which will be explained later on.
Massecuite is a viscous, sticky, semi-fluid mass of the consistency of
half-formed ice.
[Illustration: VACUUM PANS]
[Illustration: CENTRIFUGAL MACHINES]
The reason sugar “grains” is because the water in the juice has the power
to hold in solution only so much sugar. As it goes into the pan, the
juice is almost a saturated solution, and as the water is driven off by
evaporation, the solids that up to this point have been in solution must
of necessity crystallize.
When the sugar boiler decides that the “strike,” that is, the massecuite
contained in the pan at one boiling, is satisfactorily grained, he breaks
the vacuum by opening a valve on the top of the pan, thus allowing the
air to enter. He then opens the valve at the bottom of the pan and the
mass drops into a long tank with a rounded bottom, called the mixer, in
which a shaft, equipped with paddles, is revolving. The paddles are for
the purpose of keeping the mass agitated and in an even condition. The
agitation prevents the grains from dropping to the bottom of the tank and
forming a solid block, called concrete.
PREPARATION OF CRYSTALS FOR THE MARKET
From the mixer the massecuite runs through spouts into the centrifugal
machines. Centrifugal machines are cylindrical-shaped, perforated brass
baskets, usually forty inches in diameter and twenty-four inches deep,
hung on a central shaft suspended from beams overhead, and surrounded by
a solid outside curb or casing.
On the shaft is a pulley, which is driven by a belt connected with an
engine or an electric motor. The inside of the basket is lined with a
fine-meshed brass screen, which retains the grains of sugar, but allows
the liquor to escape freely into the outer casing.
As soon as the centrifugal machine is filled with massecuite from the
mixer above, the power is turned on and the machine begins to spin around
at an increasing speed until a velocity of one thousand revolutions per
minute is reached. The centrifugal action forces practically all the
liquor out through the screen and leaves in the machine all the grains
of sugar that were formed in the pan. A little dry steam is sometimes
turned in to assist in reducing the moisture in the sugar.
The centrifugal is then stopped, a valve in the bottom is opened, and the
nearly dry crystallized raw sugar is dropped into bins. From the bins
it is drawn off through spouts and packed in sacks containing about one
hundred and twenty-five pounds each.
It has been demonstrated that raw sugar containing a large amount
of moisture inverts or deteriorates more rapidly than that with a
low-moisture content. It is apparent that as moisture adds to the weight,
the transportation charges, which are based on tonnage, are greater in
the case of wet sugar than in the case of dry. In many of the modern
mills, therefore, a further treatment is given the sugar to reduce loss
by inversion and lessen freight charges.
From the bins last mentioned the sugar is dropped into revolving drums
six feet in diameter and twenty-six feet long, set at an incline so that
as the drum revolves the sugar is carried round to the highest point on
the circumference of the drum and dropped to the lower side, at the same
time traveling from the receiving to the discharging end. The shape,
motion and inclined position of the drum cause a perfect shower of sugar
in the drum for its entire length and breadth. While it is revolving a
current of hot, dry air is drawn through the drum by means of suction
fans, and as a result the moisture in the sugar is absorbed by the air
and carried out of the building. At this stage the product has a good
hard grain of a yellowish-brown color; contains from ninety-six to
ninety-seven per cent of pure sugar and about one-half of one per cent of
moisture.
[Illustration: FILLING, WEIGHING AND SEWING SACKS]
[Illustration: TRAIN-LOAD OF RAW SUGAR LEAVING MILL]
From the end of the revolving drum the sugar is drawn off into sacks
holding about one hundred and twenty-five pounds each. These sacks are
sewed by machinery and put into railroad cars to be hauled to the docks
at the shipping port, where the cars are switched under huge hoisting
cranes or alongside speedy conveyors which carry the sugar into large
seagoing steamers especially built for the trade. Some of these ships
have a cargo capacity of two hundred and twenty thousand sacks, and they
transport the sugar to the buyers on the mainland in San Francisco, New
York or Philadelphia, as the planter directs.
The liquor thrown off by the centrifugals is not lost; it is taken back
to the pans and reboiled. After this has been done several times and
most of the sugar extracted, the purity is so low and the sugar content
so small that it does not pay commercially to reboil further, and the
residue is sold as molasses. It contains about thirty-five per cent of
sugar and from twelve to fourteen per cent of invert sugar, or glucose,
as it is generally called.
Some of the waste molasses is mixed with fodder and tender cane tops and
fed to cattle and plantation stock, the sugar content proving of great
value as a fattening agent and energy builder. Part of the molasses is
sprayed on the bagasse as it leaves the crushers and serves, first, as a
fuel under the boilers, and, second, as a fertilizing agent in the form
of ashes after it has been burned. During the past few years much of
it has been shipped in tank steamers to the mainland, where it is used
for the manufacture of spirits and vinegar, and also as the principal
ingredient in prepared stock foods which are much in demand today.
Every bag of sugar shipped from the plantation is marked to indicate
the plantation from which it came. The net weight of the sugar in each
bag is recorded, a sample of the sugar taken and its sucrose content
ascertained, for it is on the basis of weight and sucrose content that
raw sugar is bought and sold.
From the beginning to the end of the process of manufacture, chemists
are vigilantly alert sampling, testing, analyzing and supervising the
operations. Records are made of all analyses, temperatures, purities,
densities, extractions, etc., and the results tabulated for future
reference.
The average cost in Hawaii of preparing the fields, planting, irrigating,
fertilizing, cultivating and cutting the cane, manufacturing the sugar
and delivering it in the New York market, is about $56.00 per ton of two
thousand pounds.
TRANSPORTATION AND DELIVERY OF RAW SUGAR
It has been explained that in Hawaii sugar is packed in
one-hundred-and-twenty-five-pound sacks. Methods and customs vary in
different countries. For instance, in Cuba it is put up in large gunny
bags, each holding an average of three hundred and twenty-five pounds.
The same custom prevails in Porto Rico. In Peru, and to a limited extent
in Java, sacks containing two hundred and twenty-four pounds are used.
A large part of the sugar in Java, however, is put up in bamboo baskets
of native make, containing from five hundred to eight hundred pounds.
They are about thirty inches in diameter, from thirty-six to forty-eight
inches high, and are lined with coarse leaves to prevent the sugar from
sifting out between the weavings of the bamboo. Philippine sugar is
packed in leaf-lined mats of tough vegetable fiber, each holding about
seventy pounds.
These various styles of containers necessitate different methods of
handling to and from the ships and by the buyers, but Hawaii will again
serve as an example of efficient, modern practice. Outside of what is
consumed locally, all Hawaiian sugars are shipped to the mainland of the
United States by steamers or sailing vessels to San Francisco, or by
steamers to New York or Philadelphia, via the Panama canal.
As sailing vessels are rapidly disappearing from the seas so far as the
sugar trade is concerned, reference will be made to steamer traffic only.
The steamers are specially built for carrying sugar, having a cargo
capacity of from five thousand to thirteen thousand tons, and the best
loading and discharging facilities.
When loading in Honolulu, the steamers usually lie alongside wharves
covered with immense warehouses, where rapid-speed conveyors carry the
sacks of sugar to a point above the ship’s hatches and drop them into
chutes which guide them down into the hold of the ship, where they are
compactly stowed. On the off-shore side of the vessel small steamers from
other island ports lie alongside and hoist the sacks by means of steam
winches to a point over the hatch and deposit them in similar chutes.
When steamers are loaded from both sides in this manner, as much as three
thousand tons, or forty-eight thousand sacks, can be loaded in nine hours.
After a vessel is completely loaded and gets her clearance from the
custom house, she departs for San Francisco, twenty-one hundred miles
away, or for the Atlantic seaboard, via Panama, as the planter may direct.
The voyage ended, and the quarantine and health regulations complied
with, she proceeds to the dock of the buyer, usually a sugar refiner.
The Hawaiian planter invariably sells his sugar under contract prior to
arrival of the vessel at destination.
Planters in other countries operate differently. Occasionally sugar is
sold on the plantation at an agreed price, and the buyer arranges his
own transportation. The planter sometimes ships his sugar unsold and
negotiates its sale while it is en route. If so sold, it is delivered
directly to the buyer on arrival; if not, it must be stored in a
warehouse at the planter’s expense pending sale.
The practice of the Hawaiian planter is to sell his sugar to refineries
in San Francisco, New York or Philadelphia, under contracts extending
over a term of years. It is agreed that the sugar shall be shipped as
soon as made and that the refiner will receive it immediately on arrival,
the price for each cargo being that quoted in the open New York market
for ninety-six-degree centrifugal sugar on the day preceding its arrival.
[Illustration: STEAMER LOADING SUGAR ALONGSIDE DOCK]
[Illustration: LOADING SUGAR AT AN OUTPORT IN HAWAII]
The value of raw sugar, like that of other staples, is based on supply
and demand, and the price fluctuates from day to day according to the
requirements of the refiners or the necessities of the sellers.
There are certain rules or trade conditions governing all sales, so
that when one man buys and another sells at an agreed price, each knows
what he is bargaining for. For instance, raw sugar is bought on the
ninety-six-degree centrifugal basis, that is, the price agreed to be paid
is for centrifugal sugar containing ninety-six per cent of sucrose. If
it contains more sucrose, a higher price is paid; if it contains less, a
lower price is paid; all according to an established scale of additions
and deductions. Then again, the time of payment for the sugar is well
understood. It is usually ten days after the sugar has been finally
discharged from the ship, as this allows a sufficient period in which to
determine the exact weight of the sugar and the percentage of sucrose it
contains. An instrument called a polariscope is invariably employed to
determine the amount of sucrose present and the results obtained from
its use are absolutely accurate. A description of the operation will
undoubtedly prove interesting.
POLARIZATION
The practical working of the polariscope is based upon the property of
sucrose to rotate a ray of polarized light to the right.
Ordinary light is the effect on the eye of vibrations of the ether. These
vibrations occur in all directions, but by certain optical devices they
may be confined to a single plane, and light thus confined is called
polarized. If rays of polarized light pass through a layer of certain
bodies, _e. g._, quartz, sugar and many others, the plane in which the
vibrations occur is rotated, and the polariscope has been devised for the
purpose of measuring the rotation of the plane of polarization.
Polarized light, as used in the polariscope, is obtained from the Nicol
prism or some development of it. Ordinary light passing through crystals
of certain bodies, of which Iceland spar is an example, is split into
two rays, one of which is known as the ordinary and the other as the
extraordinary ray. A Nicol prism is made of two wedge-shaped pieces of
Iceland spar, cemented together with a film of Canada balsam.
The accompanying sketch gives a good idea of the arrangement of an
ordinary polariscope.
[Illustration: POLARISCOPE]
A strong white light, _e_, enters the instrument through a lens at _f_,
to the Nicol prism _b_, by which it is polarized. The ordinary ray is
dispersed, while the extraordinary or polarized ray passes straight
through and enters the sugar solution contained in the tube _c_, which
has glass ends. In passing through this solution it is given a rotary
motion to the right or to the left, according as the sugar in the
solution is sucrose or levulose. When it emerges from the tube containing
the sugar solution, the now rotated polarized ray encounters a second
Nicol prism, of which one of the wedges is fixed and the other movable.
This prism is called the analyzer. A pointer, controlled by a thumb
screw, is attached to it, and when the correction of the polarized ray’s
rotation has been made with precision by adjustment of the wedges, the
pointer will indicate directly and accurately on a scale the amount of
sucrose in the solution under test, because the polarized ray was rotated
in exact proportion to the amount of sucrose contained in the solution
through which it passed.
The polariscope is made and set so that a standard weight of pure sugar
(C₁₂H₂₂O₁₁), dissolved in a standard quantity of pure water, and placed
in a tube of given length, will rotate the ray of polarized light in
passing through, to a point on the scale marked one hundred degrees, the
equivalent of per cent. Also, that by using the same quantity of water,
but twenty-five per cent, fifty per cent, or seventy-five per cent less
weight of sugar, the rotation will show seventy-five degrees, fifty
degrees or twenty-five degrees of pure sugar, as the case may be.
A sample is drawn from each bag of sugar and all of these go to make up
a general average sample. The standard quantity is carefully weighed,
dissolved with the standard amount of water, clarified, filtered and
poured into a tube with glass ends, which is then inserted in the
polariscope between the eye of the operator and a strong artificial
light. When the operator making the test applies his eye to the
instrument, he sees a distinct shadow on a lens in the line of vision,
one side being light and the other dark. He then turns the thumb screw
which adjusts the analyzer until the whole field of vision is neutral,
which indicates that the rotation of the polarized ray has been
corrected. The pointer on the scale now shows the exact percentage of
sucrose present in the raw sugar, ninety-four, ninety-five, ninety-six
degrees, or whatever it may be. This test determines the real value of
the sugar, based on the market quotation for ninety-six-degree sugar. If
the polarization should show exactly ninety-six degrees, the price to be
paid for the sugar and the market quotation will be identical.
In most sugar-producing countries the government imposes an import tax
on all foreign sugars, in order to obtain revenue to defray governmental
expenses and to protect the domestic industry, if any, against
competition with other countries in which cost of materials and labor
may be lower. Commodities produced in a country naturally add to its
development and wealth, and this explains the fostering of the sugar
industry by various governments.
The United States duty on foreign sugar is at present $1.256 per one
hundred pounds of ninety-six-degree raw sugar. On account of our treaties
with Cuba, the Cuban planter is allowed a deduction of twenty per cent,
and, therefore, pays a duty of $1.0048 per hundred pounds, which, owing
to trade conditions, is the duty effective today in the United States.
Sugars produced in the insular possessions, Porto Rico and the Philippine
islands, are admitted free of duty.
In 1898, the Hawaiian islands, through annexation, became a part of the
United States, consequently no duty is assessed on sugar or any other
Hawaiian product.
Every vessel coming into a port of the United States must be entered at
the custom house, where a record is kept of the port whence she came and
of what her cargo consists. If from a domestic port, she is permitted
to discharge her cargo without delay; if from a foreign one, customs
officials are immediately sent on board to watch the cargo as it is
discharged and supervise the tallying, checking or weighing, according
to the class of merchandise. Besides being weighed, sugar is carefully
sampled and the percentage of sucrose ascertained by the polariscope, for
the customs duty is based upon the purity of the sugar, all raws testing
not above seventy-five degrees polarization paying .71 cent per pound and
.026 cent per pound for each additional degree. This is equivalent to
1.256 cents per pound for ninety-six-degree sugar.
The people of the United States used 4,257,714 short tons of sugar in
the year 1915. It was nearly all produced within the United States or in
countries enjoying tariff concessions, as follows:
SHORT TONS
Hawaiian islands (Cane) 570,375, U. S. territory.
Louisiana (Cane) 251,740, U. S. territory.
Domestic production (Beet) 861,568, U. S. territory.
” ” (Maple) 17,248, U. S. territory.
Porto Rico (Cane) 336,347, insular possession.
Philippine islands (Cane) 134,626, insular possession.
Cuba (Cane) 2,062,594, reciprocity treaty.
Foreign sugar (Cane) 23,216, full duty-paying.
----------
4,257,714
Aside from the small amount of full-duty-paying foreign sugar imported,
the only sugar in the above list that paid duty came from Cuba. It is
evident, therefore, that under ordinary conditions an increase in the
crops of any of the places mentioned would result in a surplus of sugar
in the American market. In 1916, with the beet production of Continental
Europe locked up by the war, Cuba’s increased output has been absorbed by
Great Britain, France, Italy and Greece.
Steamers from Hawaiian ports, after arriving and entering at the custom
house and passing quarantine and health officers, proceed immediately to
refinery docks to discharge cargo.
REFINING OF RAW SUGAR
Cane-sugar refineries are always located in great seaport towns for the
reason that, as practically all cane sugar is grown in the tropics, it
must be transported by water to the world’s markets.
The refining operation is by no means as simple as may at first appear.
It is essential that the finished product be almost chemically pure (99.8
per cent), and the greatest care must be exercised to obtain a perfectly
white color, as well as a hard, lustrous grain.
The question naturally arises, why do not the planters of Hawaii,
Cuba, Java and other raw-sugar-producing countries carry their process
a few steps further and make a pure white sugar as the refiners do?
This has been attempted many times, but has almost always been found
impracticable, notwithstanding the fact that there is no mechanical or
chemical reason why.
Among the arguments in favor of a mainland seaport site, the following
may be mentioned:
1. The producing centers are generally far distant from consuming
markets. Refineries located in the tropics would be under unusual expense
for transporting and selling the refined article.
2. A refinery in the tropics would be out of direct and prompt touch with
the individual requirements of the buyers.
3. Refined sugar should be moved and sold as soon as possible after its
manufacture, so there follows the necessity for adequate dock and rail
facilities as means of quick communication with the market.
4. An abundant supply of pure, soft water for refining purposes, and
salt or fresh water for condensing, as well as fuel for the generating
of steam, must be readily available. Another most important requisite is
skilled labor, which is more easily obtained in populous seaport cities
than in the small, isolated towns of the tropics.
5. There are many commodities used in the refining of sugar and in
packing it for shipment that can be purchased more advantageously, both
as regards price and promptness of delivery, in the great commercial
ports than in the sugar-growing districts. Among these are bone-char,
lime, acids, cotton filter-bags, burlap, cotton cloth, boxes, barrels,
cartons, iron, steel and machinery of all kinds.
6. A sugar refinery is operated the entire twelve months of the year,
while a raw-sugar mill must of necessity take care of the crop of
cane in about eight months. To refine sugar where it is grown would
require refining machinery capable of handling the entire output in the
eight-month period, and during the remaining four months the plant would
remain idle. This would mean a larger investment proportionately than
that made in a refinery in a consuming center, running steadily the year
round.
7. Refined sugar very rapidly absorbs moisture, and while in transit
from the tropic to the temperate zone it is very apt to become lumpy or
caked, which would involve reprocessing at great expense at the point
of consumption. The unavoidable damage to the packages in loading and
discharging results in heavy expense, as all packages must be delivered
to the buyer in first-class condition. To avoid hardening, refined sugar
should never be piled very high, and it is an unsolved problem whether
refined sugar will stand long ocean transportation in cargo lots without
caking and damage by breaking of the inside cotton sacks. If shipped in
barrels, the freight rate is proportionately higher.
8. Larger capital would also be required, as refined sugar must be
carried on hand and must await the consumer’s demand, while raw sugar
generally has a prompt and ready market and can be quickly converted into
cash.
With these difficulties presenting themselves to a prospective sugar
refiner in a raw-sugar-producing country, the shipping of raw sugar to
refineries at great distances does not seem at all unreasonable.
Raw sugars show considerable variance in their component parts, and so it
follows that some are less easily refined than others. Such differences
are generally due to diverse methods of culture, amount of fertilizer
used, the processes of manufacture and the efficiency of extraction. If
the extraction be high, a large percentage of the salts in the cane is
taken up, and these salts prevent or retard the complete crystallization
of the pure sugar in refining. One part of ash prevents several times its
own weight of sugar from crystallizing, hence it is readily seen that raw
sugars with a low ash content are preferred by refiners.
[Illustration: A MODERN REFINERY—SHOWING WATER AND RAIL TRANSPORTATION
FACILITIES]
[Illustration: PLAN ELEVATION OF A MODERN REFINERY]
Sugar refining is the production of pure white sugar in granular form,
after the removal of the impurities from the raw product. Nine operations
are necessary to bring about this result:
1. _Washing_:
Removal of superfluous impurities.
2. _Melting_:
Changing the solid raw sugar into liquid form by melting with
water.
3. _Defecation_:
Precipitation of suspended and insoluble impurities.
4. _Bag and Bone-char Filtration_:
Removal of suspended impurities, color and soluble impurities.
5. _Crystallization_:
Production of crystals by concentration.
6. _Partial Drying_:
Purging crystals from syrup in centrifugals.
7. _Final Drying_:
The driving off of all remaining moisture.
8. _Sorting of Crystals_:
Sorting of grains according to size to meet market demands.
9. _Packing_:
Putting in various forms of containers.
A refinery consists of a group of buildings, each of which has been
constructed for a special purpose and for convenience and economy in
operation. They are as follows:
1. The melt or wash house.
2. The char house.
3. The pan house.
4. The packing house.
5. The boiler house.
6. The pump and power house.
In addition there are offices, shops, laboratories, and last, but by no
means least, very extensive warehouses.
To begin at the beginning it will be necessary to start with the steamer
laden with raw sugar and made fast to the wharf in front of the warehouse
that forms part of the refining plant.
The sugar is hoisted out of the ships in sling-loads by powerful winches,
and landed on a platform on the dock alongside the ship. Each sling-load
consists of from twelve to twenty sacks, or the equivalent weight in
baskets or mats, as the case may be. As soon as the sacks are landed,
they are sorted according to mark, put on trucks to be run over a scale
set in the floor, and their gross weight recorded.
As the truck leaves the scale, the samplers take a sample from each
sack. This is done with a tryer, a long, hollow steel tube, open on one
side and sharp at one end, with a handle on the other for the sampler to
grasp when forcing the tryer into the sack. The individual sample from
each sack of each different mark is deposited in large closed cans until
the cargo is completely discharged, when an average sample of all the
individual samples of each mark is made up and used in the laboratory
to determine the polarization or sucrose content of the various lots
comprising the entire cargo. The value of the sugar is fixed by this
polarization.
The weights of the various truck-loads of sugar passing over the scales
are totaled and the weight of the sacks, baskets or mats deducted, giving
the net weight of the sugar.
Hawaiian sacks weigh exactly one pound; Cuban, Javan and Peruvian sacks
about three and one-half pounds. Javan baskets weigh from twelve to
fifteen pounds, and Philippine mats about four pounds.
In order to facilitate the weighing and simplify the calculations, in
cases where the exact weight of the sacks is known, every truck is made
to weigh the same by ascertaining the weight of the heaviest and then
putting small iron nuts or washers on the rods of the other trucks until
each of them exactly counterbalances the heaviest. One truck is then
placed on the scale and the scale is brought to a perfect balance, just
as though there were no truck on it. In this way the weight of the truck
is never recorded, which greatly simplifies the entire weighing operation.
One crew of men will discharge from 1300 to 1500 sacks of sugar per hour
from each hatch of a steamer, or a minimum of 731 tons per day of nine
hours. As three hatches are usually worked at the same time, it will be
seen that from 2200 to 2500 short tons are taken out every day.
[Illustration: STEAMER DISCHARGING RAW SUGAR AT REFINERY DOCK]
[Illustration: SUGAR STORED IN WAREHOUSE—TWENTY-FIVE THOUSAND TONS SHOWN
IN THIS PICTURE]
From the scales the sugar is deposited on a depressed conveyor in the
floor and carried directly into the melt house of the refinery, except
the sugar that must of necessity be stored in the warehouse for future
use, in which case it is dumped from the trucks on piling machines that
elevate it to any height desired, and it is arranged neatly and compactly
by the piling crew.
The wharves and docks of a sugar refinery are, as a rule, scenes of
unusual activity and interest. Besides the large number of men engaged in
hoisting, trucking, weighing, sampling and piling the sugar, there are
the sailors, whose calling always possesses a certain fascination for the
landsman. A motley crew they are, bronzed by wind and sun, gathered from
all countries and climes. There is the simple, kindly native of Hawaii,
gentle-eyed, soft of speech and born with a love for the sea; he prides
himself upon his skill in swimming and diving, and when the day’s work is
done, entertains his shipmates by singing the plaintive melodies of his
native land, accompanying himself on the ukulele, the stringed instrument
of the South Seas. Should there be a number of his fellow islanders
among the crew, the evening’s program is almost certain to be varied
by the native hula hula dance, which generally brings marked applause
from the onlookers. Presiding over the galley, or ship’s kitchen, is
the almond-eyed Chinaman, now shorn of his queue; an excellent cook
who loves to gamble after his pots and pans are washed and put away in
place; a shrewd gamester, but scrupulously honest. Beside him stands a
fierce-looking Malay, sullen, morose and taciturn, whose sharp, white
teeth carry a sinister suggestion of the good old days of cannibalism.
His neighbor is a Filipino, short in stature, keen-eyed and alert, while
in the background are one or two individuals who from their appearance
might be direct descendants of the buccaneers who ravaged the Spanish
Main in Sir Henry Morgan’s time.
The average sailor is fond of pets, and here there is no lack of them,
parrots and monkeys for the most part, and the sayings of the former
clearly indicate a total absence of Sunday-school training.
Sugar ships bring rare fruits and vegetables from the tropics, and the
employés of the refinery have plenty of opportunities to enjoy such
luxuries as fresh pineapples, bananas, guavas, papaias, alligator pears,
breadfruit and mangoes.
A visit to the docks of a sugar refinery during the time vessels from
foreign ports are lying there is well worth while, although in these days
of steam, the picturesque features are not so pronounced as they were
before the passing of the sailing vessel.
WASHING
REMOVAL OF SUPERFICIAL IMPURITIES
As a starting point in the refining process the melt house will be first
considered. It is so called because it is there that the raw sugar enters
the refining process by being melted or dissolved in water.
The conveyor, upon which the bags were deposited in the warehouse,
delivers them on a platform on the top floor of the building. As they
come to this platform from the conveyor, workmen with keen-edged knives
seize them and, with a deft, swift slash, cut the twine sewing at the top
of the bag without injuring the burlap fabric. The bag is then pulled
off the platform, mouth downward, so that the sugar falls out and passes
through an iron grating into a large bin beneath. If the sugar should
happen to be caked or lumpy, it is sent through crushers and broken up.
[Illustration: CUT-IN STATION—SHOWING SUGAR FIRST ENTERING THE REFINING
PROCESS]
[Illustration: CENTRIFUGAL MACHINE—MOTOR DRIVEN]
As a certain amount of sugar adheres to the inside of the bags, they
are washed in large revolving machines and in this operation the sugar
dissolves in the water (called sweet water), from which it is extracted
later. They are then partially dried in centrifugal machines and hung
on hooks on a traveling chain conveyor that passes through the upper
part of the boiler house, where the waste heat thoroughly dries them. In
returning, the conveyor passes through the bag room and, by means of an
automatic device, the bags are dropped alongside the printing presses.
Here the name of the refinery, the kind of sugar and the net weight they
are to contain are printed upon them. These burlap bags are then lined
with a white cotton bag, after which they are made into bundles and sent
to the packing room to be filled with sugar. It will be seen, therefore,
that the bags from Hawaii in which the raw sugar is received are put to
good use. This, however, does not apply to those that come from Cuba or
Java; they are too large to serve as containers for the refined product,
and after being washed and dried are sold for what they will bring.
The white cotton bags are made at the refinery, and a plant turning out
one thousand tons of sugar each twenty-four hours will use twenty-five
thousand yards of cotton sheeting per day if all the output is packed in
one-hundred-pound bags.
The bin into which the raw sugar is dumped holds enough sugar to keep
the refinery supplied during the twenty-four hours run, but the entire
quantity is “cut in” during the day. The advantages of this arrangement
are that it avoids any delay in operation due to mechanical troubles
with conveyors and because more efficient work is accomplished during
the daylight hours. The employés prefer to work on the day shift and,
wherever possible, night work is avoided.
From the bottom of the bin the sugar falls into a mixing machine, called
the mingler. This is an oblong tank with a semi-cylindrical bottom, near
which is a revolving horizontal shaft, with arms or paddles attached
which thoroughly stir and mix the sugar with syrup that is added at this
point. The reason for using syrup instead of water is that the former,
being a saturated sugar solution, does not melt the sugar as water would.
The resultant mixture, called magma, looks a good deal like a soft,
brown mortar. It is, in fact, raw-sugar crystals swimming in syrup.
This consistency is needed to allow the magma to work freely in the
centrifugals, the next operation. Most of the impurities contained in raw
sugar are superficial, that is, adhering to the outside of the grain.
They may be more or less readily removed by washing the surfaces of the
crystals with water.
From the mingler the magma drops to the floor below into centrifugal
machines running at the rate of 1100 revolutions per minute. A “charge”
consists of about nine hundred pounds of magma. As the machine fills, the
centrifugal force causes the magma to rise in a vertical wall around the
inside circumference of the basket, at the same time throwing off the
syrup that was added on the floor above, and leaving in the machine about
five hundred pounds of the raw sugar as it came from the plantation.
Water is then sprayed into the machine under high pressure, through a
nozzle which divides it into very fine particles and throws it against
the wall of sugar in the machine. The water, passing through the sugar
by the centrifugal force, washes each face of each crystal and carries
off the impurities, together with a certain amount of sugar. The quantity
of water used per machine in each filling is from one to two and a half
gallons, depending upon the quality of the sugar.
This water, now a syrup, with the impurities and sugar it contains, is
drawn from the machine, part of it being pumped to the floor above to mix
with new raw sugar coming in. The remainder is treated, filtered, boiled
and made into raw sugar, which, in turn, goes direct to the melt or
through the washing process again. The result of this washing is that the
purity of Hawaiian raw sugar is raised from about 97.2 to 99.2 per cent,
and there now remains but 0.8 per cent of impurities to be removed.
The washed sugar is dropped from the centrifugal basket through a large
opening in the bottom of the machine with the aid of a mechanical device
called a discharger, which greatly reduces the manual labor.
Until very recently the sugar was discharged from the centrifugals
by hand, the men digging it out with wooden paddles in a difficult,
laborious way. One day, a few years ago, a clear-brained, observant
American lad working in a beet-sugar factory, conceived the idea that
a centrifugal could be emptied by mechanical means. He worked long and
assiduously upon the problem, and after much experimenting and many
trials and disappointments was granted a patent by the United States
government. Full of hope and confidence, he had several machines
constructed and took them to a sugar refiner, sure of being favorably
received. He met with rebuff and ridicule. The refinery engineer was
too busy with other matters to examine or give any attention to the
appliance. The next man to whom he presented it was even more indifferent
than the first; he coldly informed the patentee that he had been in the
sugar business for thirty years, that no such machine would work, and
that the only way to take sugar out of a centrifugal was by hand.
After months of effort and repeated failures, he induced the
superintendent of a beet-sugar factory to allow him to install and test
the device at his own expense. It was thrown out after a few days’ trial,
and the inventor became well-nigh desperate, although still positive as
to the merits of his discharger.
Finally he succeeded in gaining the ear of the manager of a large
refinery, who, after listening attentively to his earnest argument, at
length became convinced by it. As a result of the interview, it was
arranged between them that the machines rejected by the beet-sugar
factory should be installed in the refinery and operated for a period of
thirty days, under the direct supervision of the inventor. The test was
successful in every particular and conclusively proved the efficiency of
the discharger.
The refiner was gratified because on account of the saving in time the
capacity of the centrifugals was materially increased; the men operating
the centrifugals were hugely pleased, as the arduous work of emptying
by hand was entirely eliminated, and the inventor was happy, for he had
vindicated himself.
An order for a large number of the machines was placed at once and
every centrifugal in the refinery was equipped with one. Today they are
installed in nearly every refinery and factory in the United States, and
in many raw-sugar plantation mills as well.
MELTING
CHANGING THE SOLID RAW SUGAR INTO LIQUID FORM
From the centrifugals the washed sugar drops to the melter pan on the
floor below. This is a cylindrical tank in the center of which is a
revolving vertical shaft, to which are attached horizontal paddles that
serve to facilitate the dissolving of the sugar with the hot water that
is now added. Only enough water is added to bring the resultant liquor to
a density of 58.6 per cent of solid matter.
The raw sugar having been washed and, to use a technical term, _melted_,
leaves the melt house at this point.
DEFECATION
PRECIPITATION OF SUSPENDED AND INSOLUBLE IMPURITIES
From the “melt” the liquor is pumped to the top floor of the char house,
which is usually a structure of from twelve to fourteen stories high. The
reason for building to such a height is the advantage gained by utilizing
the force of gravity and by this means handling the liquors and bone-char
from floor to floor without mechanical aid.
The liquor is delivered into a number of cylindrical tanks equipped with
a coil of pipe through which steam is passed for heating the liquor, each
tank being capable of holding 25,000 pounds of liquor. Around the bottoms
of the tanks are perforated pipes through which compressed air is forced
to agitate and thoroughly mix the solution. On account of this air being
blown in, these tanks are called blow-ups. By means of the steam coil the
temperature of the liquor is kept at 190 degrees, which makes it less
viscous than cold liquor, thus facilitating subsequent filtration and
hastening the reaction of the lime and acid added at this point.
As the liquor comes into the blow-ups it varies in color from a straw
yellow to a dark brown, and contains a considerable amount of suspended
and insoluble impurities which must be removed. Some of these impurities
are present in the raw sugar, and others, such as pieces of twine,
lint from the bags, fine particles of leaves from the Java baskets and
Philippine mats, are traceable to the opening of the containers in the
melt house.
The process of removal is called defecation. In former years this was
accomplished by adding bullocks’ blood to the raw-sugar liquor in the
blow-ups and heating the mixture until the scum which rose to the surface
cracked, when the solution below was found perfectly clear, or, in the
language of the refinery man, _bright_. Today, however, chemicals are
the defecating agents, those most commonly used being phosphoric acid
and lime. Phosphoric acid, neutralized with lime, throws down a heavy,
flocculent precipitate which, as it settles, sweeps the solution and
drags down all the suspended matter, gums, etc., leaving the liquor above
clear and transparent.
The precipitate must now be removed, and this is accomplished by running
the liquor through the bag filters on the floor below. These filters are
tight iron boxes, about sixteen feet long, six feet wide and seven feet
high. The top of the box is depressed about eight inches below the sides
and ends, thus forming a tank. This top is perforated with five hundred
holes, one and one-half inches in diameter. From the bottom of the iron
box is an outlet pipe leading into tanks below.
In each of the holes on the inside top of the box is screwed a so-called
“brass bottle,” conical in shape, to which is securely attached a
closely-woven cotton filter bag, about twenty-four inches wide and
seventy inches long. This filter bag is encased in a heavier and stronger
cotton sheath, or sleeve, about eight inches wide, which adds strength
and keeps the twenty-four-inch bag in folds so as to give an effect
similar to that of a folded paper filter, frequently seen in drug stores.
Each bag filter contains five hundred of these bags, suspended vertically
from the top.
Before any liquor is run on the filters, the bags and the iron box are
heated by means of steam to bring the apparatus to a temperature of
about 190 degrees Fahrenheit. This prevents the chilling of the sugar
liquor by cold bags, which would cause the bags to become “blocked,” as
it is technically called. The liquor from the blow-ups, at 190 degrees
temperature, is now turned into the depressed tank on the top of the
filter and flows through the perforations into the bags attached on the
inside, down through the bags, and finds an exit through the bottom of
the filter into the tanks below.
As the first liquor comes through the bags, it is a little cloudy, but
in a few minutes, as the pores of the bags fill with the insoluble
substances, it becomes perfectly bright, all the suspended and insoluble
impurities remaining in the bags, together with the precipitates
drawn over from the blow-ups. The cloudy liquor is pumped to the top
of the filter and clarified by being run through a second time. It
is interesting to know that it is not really the bag that does the
filtering, but the thin layer of sediment that is deposited from the
liquor itself on the inner surface of the bag. The cotton bags are made
in a particular manner, and from a fabric especially adapted to catch
the sediment and to form, in conjunction with it, an excellent filtering
medium.
[Illustration: BAG FILTERS—SHOWING BAGS IN PLACE]
[Illustration: FILTER PRESSES]
The liquor, as it runs into the tanks, must be carefully watched, for
sometimes a bag inside the filter breaks, which causes cloudy liquor by
allowing the precipitates to gain entrance into the clear liquor. As soon
as this is noticed, samples are taken from the outlet of each filter and
the defective one found and investigated.
When a bag is torn, or develops a hole, the liquor runs through the
opening on the top of the filter so fast that it forms a little
whirlpool, which shows the bag that is broken. A wooden plug is
immediately driven into the opening and that particular bag cut out. The
men on the bag filters soon become so expert that they detect broken bags
and plug them before the cloudy liquor gets to the inspection station.
It is essential that the liquor be freed from all suspended impurities
at this station before the next step is taken, hence great care and
watchfulness must be exercised.
In time the coating of sediment, gums and precipitates on the inside of
the bag becomes so thick that the liquor runs very slowly and finally
stops. The refinery term for this condition is “stuck-up.” Depending on
the impurities in the original liquor, the bag filters will continue to
filter the liquor for from twelve to twenty hours and sometimes longer.
After the bags are “stuck-up,” the liquor remaining in them is sucked out
by means of vacuum through a small pipe attached to a long rubber hose
and inserted in the bags through the holes in the top of the filter. The
liquor thus sucked out of the “stuck-up” bags is sent to the blow-ups and
reprocessed with new liquor, thus beginning its journey anew.
As soon as the liquor is sucked out, hot water is run through to reduce
the sugar contents of the filter. This water is saved and the sugar it
takes up is subsequently recovered. The filter is then opened by means
of an electric hoist traveling on an overhead track immediately above
the filters. Chains are attached to the top of the filter and the hoist
elevates top, bags and all, to a point sufficiently high for the bags
attached to the top to clear the adjoining filters. The top and bags are
then moved along the track to the washing station. Meanwhile another
hoist has delivered a duplicate top, with fresh bags attached, to the
filter, where it is lowered into place. In this way the filter is again
in operation within five minutes. At the washing station the bags just
taken from the filter are detached from the top for washing, and the top
is sent to a point where clean bags are again attached. It is then ready
to go into another filter.
At the washing station the dirty bags are pulled out of the sheaths and
turned inside out in tanks containing water, thus releasing a large
quantity of the impurities. The bags and sheaths are then thrown into
washing machines, where all the remaining impurities and sugar are washed
out of them. From the washers the bags are put into centrifugal machines,
or through powerful wringers, and dried sufficiently to permit being
rehandled. They are then resheathed and made ready to be attached to
another top.
The water from the washers contains a large amount of sugar and is
conducted to a tank similar to one of the blow-ups, where it is treated
with lime and diluted with water at 190 degrees Fahrenheit until it
contains only from ten to twelve per cent of solid matter. This liquid is
then pumped through filter presses and the impurities removed. The “sweet
water,” as it is termed, which now contains practically all the sugar, is
collected in tanks and the sugar is ultimately extracted by evaporation,
filtration and boiling to grain.
[Illustration: MAKING NEW BAGS AND LINING THE WASHED BAGS]
[Illustration: PRINTING THE EMPTY RAW-SUGAR BAGS]
The impurities removed by the filter presses consist of sand, portions
of bags and baskets, phosphates, hair, lime, salts and gums, in fact
every kind of foreign matter that finds its way into raw sugar either in
the process of manufacture or in transportation. A small amount of sugar
accompanies this refuse, but as its recovery would cost more than it is
worth, it is allowed to run to waste. The filter-press cake, as it is
called, contains valuable fertilizing agents, and when conditions permit
it is used for fertilizing purposes, otherwise it is run to waste.
BONE-CHAR FILTRATION
REMOVAL OF COLOR
To resume the course of the bag-filtered liquor, from which the
superficial, the suspended and insoluble impurities have been removed
and which is now the color of clear amber, the next step is bone-char
filtration.
Bone-char, bone-coal or bone-black, as it is variously called, is made
from the bones of animals. After the fat and glue are removed, the
bones are subjected to a dry distillation which carbonizes them. These
charred bones are then broken into very small pieces, or until they will
pass through a ten-mesh screen and remain on a thirty-mesh screen; in
other words, the size of the grains used in a sugar refinery vary from
one-tenth to one-thirtieth of an inch. If properly manufactured, the
grains are hard, porous, and have a great affinity for moisture.
Bone-char has the peculiar property of removing from the sugar liquor,
in some unknown mechanical way, not only the soluble salts but the
coloring matter as well. The elimination of the salts and coloring matter
facilitates the subsequent crystallization.
The char house is, therefore, by far the most important station in a
refinery, for failure in the char house means failure throughout.
Contrary to the general practice in Europe, beet-sugar factories in the
United States do not use bone-char, and consequently do not take all the
coloring matter and salts out of the liquor. They secure a white sugar
by other methods, which will be explained later on. In a cane-sugar
refinery, however, the coloring matter and impurities are entirely
eliminated, and the product is invariably pure and white.