LARD, COMPOUND AND GREASES
HISTORICAL -- QUANTITY AND QUALITY -- NEUTRAL LARD -- KETTLE RENDERED
LARD -- PRIME STEAM LARD -- REFINED LARD -- BLEACHING LARD -- FILTER
PRESS -- LARD ROLL -- LARD PACKING -- COMPOUND LARD -- COTTONSEED
OIL -- REFINING CRUDE OIL -- DEODORIZING COTTONSEED OIL -- PRESSING
TEMPERATURES -- LARD OIL -- TREATMENT FOR LARD GREASE.
=Historical.=--The refining of lard in packing houses is comparatively
recent, and many people will be surprised to know that even the largest
packers only added lard refining to their business within the past
twenty-five to thirty years. Previous to that time lard refineries
were operated by independent firms, who bought their supply of prime
“steam” lard, converting it into the different grades in their own
establishments. In the natural evolution of the business this branch
was taken up by the packers.
Before the advent of present methods, lard refining consisted in
pressing from the lard about 30 to 40 per cent lard oil, sold for
lubricating and lighting purposes, etc., and mixing the stearine with
straight lard, making a high grade pure lard. At this time the method
of bleaching in all lard refineries was accomplished by the use of
caustic soda, pearl ash, lime, alum, or other substances, the principal
ingredient, being caustic soda. The underlying principle is that
alkali, used in proper proportion, saponified the acid in the lard.
This process, however, is a thing of the past.
=Quantity and Quality.=--As shown in a previous chapter from thirteen
to fifteen percent of the live weight of the hog is fresh lard,
consequently where large numbers of hogs are killed the manufacture of
lard is an important factor in the packing business. The principal
grades are known as neutral lard, kettle rendered lard, prime steam
lard, refined lard and compound lard.
Tallow and stearine also enter into the manufacture of refined and
compound lards.
=Neutral Lard.=--When oleomargarine was first manufactured it was
considered necessary to use natural butter in the mixture in order to
give it the proper consistency, as the oleo oil was grainy and coarse,
therefore sufficient natural butter was added to change that condition.
Some one conceived the idea of using neutral lard made from leaf lard
in place of natural butter in oleomargarine. When this was worked out
successfully the term oleomargarine practically disappeared and the
term “butterine” was substituted. In most of the butterine made today
no natural butter is used.
The conditions in making oleo oil and tallows have their parallel in
neutral lard and kettle rendered lard. When leaf lard is cooked for
kettle rendered lard, if a temperature of from 250° to 260° F. is
obtained the tissues of the lard are burned or partially consumed, this
heat giving it a flavor which is called “high kettle rendered” flavor.
When it is made into neutral this condition is reversed, the lard being
melted at a temperature of from 126° to 128° F. At this temperature no
burning of tissues is possible, hence the oil extract is neutral in
every sense of the word, in color, flavor and smell. With these three
essential points the material readily forms the chief substance for
butterine by adding milk or cream and oleo oil and cotton seed oil, as
desired.
=Manufacture of Neutral.=--The following steps define the process of
manufacture necessary to produce neutral:
_Chilling._--The leaves as pulled from the hogs are rapidly sent to a
cooling room to be thoroughly chilled. The leaves are spread separately
in flat sheets on metal supports, which are preferable to wood. If it
is chilled too slowly a strong “hoggy” flavor is developed, which it is
impossible to eradicate from the fresh product. The leaf lard should be
chilled for twenty-four hours in a temperature of 32° to 34° F.
_Melting._--It is put through a hasher of the Enterprise type to an
open top water jacketed kettle, similar in type to an oleo kettle.
Frequently the melting kettle is a wooden vat with a galvanized iron
kettle inside, the space between the wooden vat and the galvanized
kettle being filled with water which is heated to the desired
temperature for melting the product. It is not practicable to use a
steam jacket as the heat would be excessive and it would be difficult
to control. This kettle properly is water jacketed and open top so no
pressure is generated.
In a kettle holding 4,000 to 5,000 pounds, water should be warmed in
the jacket before lard is put in, the agitator started slowly, not
to exceed 10 to 12 revolutions per minute, and the heat should be
regulated so as to have the lard all melted and ready to drop in one
and one-half hours from the time of starting to hash. By the time the
lard is thoroughly melted the temperature should be 126° to 128° F.
_Settling._--As soon as the lard is melted it should be drawn off with
a siphon into receiving kettles, which are also jacketed and held at
practically the same temperature. When dropped it should be salted with
one-half to one per cent of fine salt, letting it stand from fifteen to
thirty minutes. In drawing off it should be siphoned through several
layers of cheese cloth, forming a strainer, into receiving tanks,
where it should settle four hours. It is drawn into tierces through a
pipe raised from the bottom to leave one and one-half to two inches of
lard in the tank, care being taken that no “bottoms” are drawn into
the tierce, as these contain tissues which are, for the most part,
undiscernible; also moisture. These ingredients in neutral, being only
partially cooked, immediately begin to decompose. It is a delicate
article to handle and the settling of all impurities is important. The
neutral, when drawn into tierces, should be at a temperature of from
115° to 118° F.
_Storage._--The tierced lard should be kept at a temperature of about
75° F. for about ten or fifteen hours, and then put into a cooler
with a temperature of from 45° to 50° F. The tierces should be filled
through the bilge and not closed when stored in the first mentioned
temperature, the bungs being left out, while the heat is permitted
to escape, thus carrying with it considerable flavor, and making the
material more neutral than if the tierces were closed as soon as
filled.
=No. 2 Neutral Lard.=--This is a neutral lard made from back fat. At
times it is profitable to make this product into No. 2 neutral instead
of steam lard, for when the market for No. 1 neutral is extremely high
there is demand for a good No. 2. When making this, the rind should
be skinned off from the back fat, leaving clear back fat to be hashed
for neutral. If the rinds are put in, it gives the product a “hoggy”
flavor, which makes it undesirable. It is hashed and melted the same
as No. 1 neutral, except as to temperature, the melting point for this
being 132° to 134° F., method and apparatus as described for the making
of No. 1 neutral, being applicable to this.
_Test--Pure Steam Lard vs. Neutral._--Below is a test on raw leaf lard
rendered into neutral, showing yield, and percentage of the neutral
lard produced; the scrap and bottoms from the kettle being run into
kettle rendered lard.
TEST ON LEAF LARD RENDERED INTO NEUTRAL.
Raw leaves 8,958 pounds at $0.08¹⁄₈ per pound = $727.84
Salt for settling 35 pounds at 4.90 per ton = .09
-------
$727.93
_Production:_
Neutral lard 7,880 pounds at $0.09125 per pound = $718.96
Neutral bottoms 1,055 pounds
(Run under forty pounds pressure two and one-half
hours.)
Prime steam lard 497 pounds at 0.082 per pound = 40.75
Tankage 56 pounds at 18.00 per ton = .45
------- $760.16
-------
Gain on production $ 32.23
Gain per 100 pounds on raw weight, $0.036.
_Percentage Production:_
Neutral lard to raw weight 87.97
Neutral bottoms to raw weight 11.78
Prime steam lard to raw weight 5.55
Tankage to raw weight .63
Prime steam lard to weight of bottoms 47.11
Tankage to weight of bottoms 5.31
Total production of lards 93.52
Total production of raw weights 94.15
_Tanking Leaf Lard:_
Raw leaves 1,000 pounds at $ 0.08125 per pound = $81.25
Prime steam lard 929 pounds at 0.0825 per pound = 76.18
Tankage 5 pounds at 18.00 per ton
------
Loss on production $ 5.07
Loss per pound on raw weight .0051
Prime steam lard to raw weight, per cent, 92.9.
_Test--Chilling and Tanking._--
TEST ON CHILLED LEAF LARD TO DETERMINE VALUE AND YIELD.
Warm leaf lard to cooler 1,000 lbs.
Chilled leaf lard 986 lbs.
Shrinkage, 1.4 per cent 14 lbs.
Weight to test tank, 986 pounds; value per cwt., $7,556.
Yield prime steam lard 94.12 per cent; 928 lbs. at $8.025 per
cwt. $74.47
Yield tankage (pressed) .81 per cent; 8 lbs. at 9.89 per
ton .04
------
Total $74.51
_Test._--Showing manipulation of 5,000 pounds of back fat to make
neutral, kettle rendered lard and pure steamed lard:
TEST ON 5,000 POUNDS OF BACK FAT CONVERTED TO NO. 2 NEUTRAL KETTLE
RENDERED LARD AND PRIME STEAM LARD.
Net wt. Per
lbs. cent.
Back fat 5,000
Less skins removed 586 = 11.72
-----
Skinned back fat rendered to No. 2 neutral 4,414
Production No. 2 neutral 1,846 = 41.82
Bottoms left in kettle 2,568
=====
Bottoms from No. 2 neutral rendered to kettle rendered
lard 2,568
Stearine added 270 = 10.51
-----
Total 2,838
Production of kettle rendered lard from above 1,940 = 68.36
-----
Bottoms from No. 2 neutrals 898
Kettle rendered bottoms 673
-----
Loss on production 225
=====
Bottoms from kettle rendered to prime steam lard to tank 673
Production of prime steam lard 307 = 45.62
-----
Skins from back fat rendered to prime steam lard 586
Production of prime steam lard 192 = 32.76
RECAPITULATION.
Net wt.
lbs.
Rendering back fat 5,000
Oleo stearine added 270
-----
Total 5,270
Production No. 2 neutral lard 1,846 pounds
Production kettle rendered lard 1,940 pounds
Production prime steam lard 499 pounds 4,285
-------------------
Waste 985
=Kettle Rendered Lard.=--Kettle rendered lard is the purest and best
lard made in packing houses and consists of leaf lard and back fat, the
proportions varying according to the value of the raw product, usually
on a basis of about 60 per cent back fat and 40 per cent leaf. While
kettle rendered lard is sold under the label of “pure leaf lard” there
is little leaf used, as this part is worth more as a neutral lard than
when made into kettle rendered. A very acceptable formula for kettle
rendered lard, if handled properly, is as follows:
70 per cent back fat;
15 per cent leaf scraped lard, which is pieces of leaf, scraped out of
the hog after the leaf lard has been pulled, and thoroughly
chilled;
15 per cent lard stearine.
Where neutral lard and kettle rendered lard are made together a nice
flavor may be imparted to the kettle rendered lard by using the bottoms
of neutral lard when cooking it, as the scrap from the neutral when
brought to the high temperature of kettle rendered lard imparts a rich
flavor.
_Process for Kettle Rendered Lard._--The raw product is put through a
hasher which cuts the fat tissues, so that when the heat is applied the
oil readily separates. The kettle generally used for this purpose is
about five feet in diameter and from five to seven feet deep, made of
wrought iron, jacketed for steam, with an agitator to keep the product
agitated while cooking. The jacket should be kept heated until through
hashing, then increased until the temperature of the lard reaches 255°
to 260° F., when the pressure should be shut off for one and one-half
hours at least--one and one-half hours should be taken to reach this
period. If lard stearine is used it should be added at this time,
using about 15 per cent for the summer formula. After this period of
shut-off, again turn on the steam, holding temperature, allowing the
contents to cook until dry, or until no further steam arises, which
will consume probably from thirty to forty-five minutes. Stop agitating
and add twenty pounds of salt, let stand to settle one hour, then lower
into the kettle below, strain through a cloth sieve, the lard being
taken off the scrap with a siphon. The scrap will remain in the bottom
of the cooking kettle; if handled carefully, very little will pass
through the pipe. The lard, when being drawn into the kettle below,
should be passed through several thicknesses of cheese cloth in order
to catch any small pieces of scrap or tissue.
_Settling._--After the lard is lowered into the settling kettle,
allow it to stand two to three hours, then siphon to a third kettle,
as considerable scrap will have gone through into the lard from the
cooking kettle, strain it through a double thickness of cheese cloth
stretched over a frame. In the third kettle a scum will arise on it,
which should be immediately skimmed off, and about ten pounds of fine
salt added to a 5,000-pound batch, to aid in settling. If convenient,
it is advisable to allow the lard to settle in this kettle for twelve
hours before drawing it off, although this length of time is not
necessary, but a perfect settlement of the impurities is necessary to
make the best lard.
_Scrap._--After the lard is drawn from the cooking kettle, the scrap
should be drawn from the bottom. This scrap is used in the prime steam
lard tank. If, however, there is no other provision for handling the
scrap, it should be put into a hoop press (Fig. 150), and pressure
applied, thereby liberating all the oil left in the residue, the scrap
then being used as “pressed scrap.”
_Packing and Cooling._--Kettle rendered lard is usually sold and used
more extensively during the cooler weather. It is very desirable that
there should be a light, fluffy top. This is only possible when the
lard is drawn hot in a cool room; chilling the lard rapidly causes this
appearance at the top, which is always looked upon by the trade as a
mark of excellence. When the lard is drawn off into small packages they
are placed one on top of the other, covering the top with paper. The
cover should not be put on the package until it is chilled, otherwise
the fluffy appearance is lost.
[Illustration: FIG. 150.--HOOP PRESS.]
_Drawing Temperatures._--When drawn into wooden packages, such as ten,
twenty or fifty pound pails, lard should be drawn at 150° F. If drawn
into tins it should be drawn off at 175° to 180° F.; when drawn into
tierces, barrels or half barrels it should be drawn at about 130° F.
When drawing lard into wooden packages they should be silicated the day
before, giving them ample time to dry, as this prevents the packages
from soaking up the lard and also prevents excessive shrinkage of the
package.
=Refining Prime Steam Lard.=--Refined prime steam lard is made into two
products, pure refined lard and lard with beef fat added.
=Pure Refined Lard.=--Pure refined lard consists of prime steam lard
with lard stearine added. This is a product resulting when prime steam
lard is pressed to obtain lard oil, a process described later; however,
the quantity available is quite limited. Descriptions will be confined
to the making of lard with beef fat added.
[Illustration: FIG. 151.--SECTION THROUGH TANK FOR MIXING FULLERS EARTH
AND LARD.]
=Fullers Earth.=--About thirty years ago the method of refining
lard with fullers earth was first inaugurated, and for years only
imported earth from England was thought suitable for this purpose.
Deposits of fullers earth, of fair quality, have been discovered in
the United States and American fullers earth is today used in some
lard refineries. Indications are that with improvements in mining and
methods of grinding, and possibly also in the discovery of better beds
or layers of this substance, manufacturers will not continue to go
abroad for supplies of fullers earth.
An explanation of how fullers earth bleaches lard and its kindred fats
would be interesting, if anyone knew the exact explanation, but so
far there has been no scientific reason given that accounts for this
property of this material, therefore no chemical test can be applied
to different samples of fullers earth to determine whether they are
suitable for refining or not. The only safe test is the practical one
of heating a sample together with lard and watching the result of the
bleach.
Fullers earth is used for bleaching cotton seed oil and other greases
and fats which are subjected to the bleaching process. In improving
the color of lard it is done at the expense of flavor, and a wholesome
odor, which is natural to the lard, is sacrificed in a greater or
lesser degree to the advantage of color. The tendency is to make lard
white, even though it loses in odor and taste. In compounding lard this
is intensified by the general use of tallow.
[Illustration: FIG. 152.--FULLERS EARTH KETTLE FOR SMALL HOUSES.]
=Bleaching Kettle.=--This can be of a predominant size dependent
upon the volume of business. For a moderate business the most
suitable dimensions are about six feet in diameter and four feet
deep. A sectional view of such a kettle is shown in Fig. 151 and a
smaller kettle is illustrated in Fig. 152. It was the practice to use
compressed air for agitation so as to mix the fullers earth with the
lard. This has been discontinued in the best refineries, as it was
found that agitation with air had a tendency to make the lard turn
rancid more readily than if agitated by mechanical device.
The kettle is supplied with a vertical shaft, to the bottom of which
is attached a propellor about fourteen inches in diameter. Around this
is fitted a wire screen about thirty inches high made of galvanized
wire, ³⁄₁₆-inch mesh, this screen clearing the blades of the fan about
an inch. On top of this screen is fixed an iron pipe approaching to
within about eighteen inches of the surface of the lard when the kettle
is filled. A kettle of this size will hold about 5,000 pounds of lard
for treatment. The agitating blade should revolve at a speed of from
125 to 175 revolutions per minute. This has the effect of producing a
miniature whirlpool in the body of lard by driving the lard through the
screen against the sides of the kettle, where it rises to the surface
and goes down through the funnel-shaped tube to be again driven through
the screen. In this way the fullers earth is thoroughly mixed in and if
there is a tendency to “lump” the lumps are readily broken up by impact.
=Bleaching Lard.=--If cold lard is used it should be melted and any
sediment or moisture which settles should be drawn off. It is best not
to draw off too close to the bottom so as to avoid any moisture.
The temperature at which lard should be bleached is an important matter
to be determined. If the lard has been heavily cooked and has a strong
steam flavor, a temperature of 180° F. is correct. If the lard has
not been well cooked a somewhat lower temperature is necessary. As a
rule the lower the temperature at which bleaching is done, the more
fullers earth is required to get the proper bleach and at the same
time as little earth flavor as possible is a point for careful and
intelligent consideration. The best way to determine, where there are
large quantities of lard, is to take a small sample and make tests in
the laboratory. The point to be obtained is to get the bleach with as
little of the flavor of the earth as possible. Generally speaking, from
three-fourths to one and one-half per cent of fullers earth will get
the desired result.
When the lard is brought to the proper temperature, fullers earth is
put in the kettle, when it is agitated from eight to twelve minutes,
then pumped through the filter press as rapidly as possible. It takes a
certain length of time for fullers earth to do its work properly, and a
strong agitation of from eight to twelve minutes appears to be the best
method to adopt in order to obtain the full effect of the earth.
=Refining Tallow Separately.=--Where tallow is used in lard, it is
always advisable to bleach the tallow separately. This is done in the
same manner as described for lard, with the exception that about three
per cent of fullers earth is used, after which it is pumped through the
filter press and into the receiving tanks.
[Illustration: FIG. 153.--FILTER PRESS.]
When it is compounded with the lard, the desired amount should be put
into the kettle with the lard after it is treated. The same is true
of oleo-stearine, except that in the bleaching of this article from
one-half to one and one-half per cent of fuller earth is sufficient.
Measures must be taken to see that ingredients are intimately mixed
before passing the product to the rolls.
The use of tallow or stearine is for the purpose of cheapening the
product, as well as hardening it, the formula for same being made
according to the values and conditions under which the lard is to
be sold. For instance lard going south, or into a warm climate,
is made much harder than lard for a temperate climate; hence lard
formulas, generally speaking, are worthless for general use, the
different formulas being made to suit widely different conditions, and
their availability also depends to a considerable extent upon the
fluctuation of values.
=Filter Press.=--After the contents of the kettle have been pumped
through the filter air pressure should be turned into the filter press
in order to blow out all the lard possible. After this live steam
should be turned on, expelling the balance of the lard from the pipe. A
large portion of this latter lard, however, is unfit to be used again,
as it contains sediment and fullers earth combined, having a rank,
strong odor, and can be used only for grease.
[Illustration: FIG. 154.--LARD COOLING CYLINDER.]
=Lard Roll.=--This is a device provided for cooling lard in a film
so as to bring plenty of air in contact with the surface during the
congealing. After the lard has been put through the filtering press it
goes to a receiving tank and is next passed over rollers for chilling.
(Fig. 154.) These are cast iron cylinders containing refrigerated
brine. The cylinders revolve at from ten to fourteen revolutions per
minute, the lard being congealed on the outer surface. Fixed against
the side of the cylinder is the edge of a steel knife which scrapes
close to its surface. The lard, in contact with the cool surface of
the cylinders, congeals and as it passes to the knife it is removed
and drops into the trough. Here it is thoroughly beaten by a revolving
shaft with pickers on it, so that all lumps are broken and the grain
is of a smooth, even consistency. Pure lard passes to an agitator,
which is a jacketed kettle, where it is given a thorough agitation
and drawn off cool as possible, the object being to have the different
ingredients thoroughly mixed at a low temperature.
At times rolls are used in tandem. When a bountiful supply of cold
water, say at 60° F., is available, the saving in refrigeration
justifies the use of tandem rolls. In this instance the first roll is
elevated so as to gravitate the lard to the feed of the second.
WEIGHT OF LARD PACKAGES.
=====================+================+=========
| Weight | Avg.
Weight packages | material | weight
---------------------+----------------+---------
3-POUND PAILS: | |
100 pails | 43 lbs., 7 oz.| 6.95 oz.
100 bails | 5 lbs., 4 oz.| .84 oz.
100 covers | 9 lbs., 7 oz.| 1.51 oz.
100 summer covers | 6 lbs., 3 oz.| .99 oz.
---------------------+----------------+---------
Average weight each| ... |10.29 oz.
| |
5-POUND PAILS: | |
100 pails | 58 lbs., 12 oz.| 9.40 oz.
100 bails | 5 lbs., 15 oz.| .95 oz.
100 covers | 13 lbs. | 2.08 oz.
100 summer covers | 8 lbs., 10 oz.| 1.38 oz.
---------------------+----------------+---------
Average weight each| ... |13.81 oz.
| |
10-POUND PAILS: | |
100 pails | 92 lbs., 14 oz.|14.86 oz.
100 bails | 7 lbs., 12 oz.| 1.24 oz.
100 covers | 19 lbs., 5 oz.| 3.09 oz.
100 summer covers | 13 lbs., 10 oz.| 2.18 oz.
---------------------+----------------+---------
Average weight each| ... |21.37 oz.
| |
20-POUND PAILS: | |
100 pails |144 lbs., 15 oz.|23.19 oz.
100 bails | 10 lbs., 9 oz.| 1.69 oz.
100 covers | 34 lbs. | 5.44 oz.
100 summer covers | 22 lbs., 4 oz.| 3.56 oz.
---------------------+----------------+---------
Average weight each| ... |33.88 oz.
| |
40-POUND SQUARE CANS:| |
100 cans |268 lbs., 8 oz.|42.96 oz.
100 caps | 2 lbs., 8 oz.| .40 oz.
---------------------+----------------+---------
Average weight each| ... |43.36 oz.
| |
50-POUND ROUND CANS:| |
100 cans |270 lbs., 10 oz.|43.30 oz.
100 covers | 50 lbs., 2 oz.| 8.02 oz.
100 summer covers | 38 lbs., 12 oz.| 6.20 oz.
---------------------+----------------+---------
Average weight each| ... |57.52 oz.
---------------------+----------------+---------
=Lard Packing.=--Refined lard is not usually drawn in a cooler. In most
climates the non-refrigerated rooms will suffice. It is packed in tubs,
barrels or tierces of wood. The lard, when available, in the picker
trough, is usually chilled and stiff. The use of a pump is made to
withdraw and force it through a strainer in an enlarged section of the
pipe, so as to effectually break all lumps. A relief valve should be
placed on the line to spill into the picker in case the draw cocks are
all suddenly closed.
=Lard Packages.=--In wooden packages tare is deducted. The table on
preceding page shows the actual weight of the different packages which
are usually made from an X L grade of tin. Inasmuch as lard sells at
more per pound than the tin costs, there is always an endeavor to get
the packages as heavy as consistent.
=Country Style Lard.=--Many moderate sized plants that do not cater
to a trade accustomed to highly refined lard, prefer to make kettle
rendered lard as most of their output, using leaf, back fat and
trimmings, adding the complimentary proportion of killing lard and
agitating the whole in a water jacketed agitator. All implements used
are similar to those described previously, also the method of drawing
from the agitator to packages is the same. Beef fat can be rendered in
the same way when oleo departments are not operated, and it can thus be
used to good advantage.
=Compound--What it is.=--Compound is a substitute for lard and is
made of cotton seed oil and oleo stearine, or tallow, or both. The
formula on this article varies according to the relative values of the
ingredients. The generally accepted formula is 80 per cent cotton seed
oil, and 20 per cent oleo stearine.
If the market price of oleo stearine is high, a formula may be
substituted as follows: 75 per cent cotton seed oil, 7¹⁄₂ percent
tallow, 17¹⁄₂ per cent oleo stearine. In cold weather even a smaller
amount of stearine may be used and a proportionately larger amount of
tallow.
=Cottonseed Oil.=--This is a product derived from cotton seed. Before
the manufacture of cotton seed oil, the cotton seed, removed from the
cotton, was thrown in large compost heaps and after decomposition, was
used sparingly as a fertilizer. An idea of its value may be gained from
the following table. From one ton of seed, by average, is obtained:
270 pounds or 36 gallons of oil at 28c per gallon $10.08
750 pounds cotton seed meal at 90c per 100 pounds 6.75
850 pounds hulls at 15c per 100 pounds 1.27
30 pounds lint at 3¹⁄₂c 1.05
------
Total value $19.15
100 pounds waste and dirt.
The oil when extracted from the seed is termed “crude oil.” In refining
this oil the loss varies from 7 per cent to 12 per cent, on an average
about 9¹⁄₄ per cent.
=Refining Crude Oil.=--The crude oil is purchased by refiners and
treated to produce “yellow oil.” In this process it is put into a tank
(it is generally considered profitable to refine cotton seed oil only
in large quantities) supplied with a revolving agitator. Into the
tank is put a solution of eighteen to twenty per cent caustic soda.
The quantity and strength of the solution necessary is determined
by treating a small sample. To a small sample of oil add the soda
solution, stirring continuously, having it heated to a temperature of
160° to 180° F. When sufficient soda lye has been added a floculent
precipitation will be noticed. This indicates a “breaking” of the oil.
By calculation of the relative amount the comparative quantities can be
arrived at.
An excessive amount of lye will saponify its equivalent in good oil,
therefore care must be exercised to see that only the proper amount
is used. In a practical way the soda is introduced in the crude oil
solution and agitation is started to insure the thorough mixing of
the caustic soda and the oil. The floculent substance appearing, the
agitation is stopped and the oil allowed to settle, the sediment and
substance other than oil collecting at the bottom of the tank. A small
quantity (about one-quarter of one per cent by weight) of fullers
earth is added and the oil removed by pumping through a filter press
producing what is known to the trade as “yellow oil.”
The sediment, known as “foots” is collected in kettles and treated with
additional lye, boiled and settled with salt; water added, settled and
drawn. This treatment is duplicated as many times as necessary, until
the soap stock will separate from impurities. When thoroughly settled
draw the soap stock into packages for the soap trade. The finished
“foots” contains about 33 to 40 per cent of moisture and a small
percentage of lye.
=Deodorizing Cotton Seed Oil.=--The “yellow oil” of trade has a
decided flavor which it is desirable to remove, and this process is
accomplished by deodorizing. (See Fig. 155.)
_Treating Tank._--This tank is equipped for heating the oil to a
very high temperature by the introduction of a large coil surface,
preferably rings, one within the other and arranged so that each ring
is accessible. The kettle coils, etc., should be made extra heavy. The
top of the kettle must also be hooded and as the oil boils violently
the steam must be given free opportunity to escape. The escape pipe
should be at least sixteen to twenty inches in diameter in a tank six
feet in diameter, and should be provided with a goose neck, so that the
steam rising which condenses, does not drip back into the tank. Fig.
155 show the construction of an oil treating tank.
The exhaust pipe extends into the atmosphere a short distance above the
deodorizing tanks. On account of the extreme agitation caused by the
heat, the oil is likely to boil over and waste. Special attention is
called to the crook or neck in the exhaust pipe with two-inch outlet at
the lowest point. This is done so that the condensation will not run
back into the oil, but can be taken out at this point.
=Process For Oil.=--The tank is filled with oil to about half its
capacity. The oil is then heated to a temperature of 320° to 360° F.
After being held at this temperature for an hour to an hour and a
half, it is ready for the washing process. This is done by means of a
two-inch perforated pipe at the top of the kettle, through which is
sprinkled cold water on the oil. The extreme temperature evaporates the
water very rapidly and at the same time causes a precipitation. The
water should be allowed to run for five minutes, and then the body of
oil should stand for from one to two hours. The cone, or bottom of the
kettle, will be found to have a sediment which has been precipitated
from the oil. This “bottom” should be drawn off, and the steam again
turned on the coils.
[Illustration: FIG. 155.--DEODORIZING TANK FOR COTTON SEED OILS.]
_Blowing._--The oil is heated to the original temperature and steam
of high pressure and temperature introduced into the body of the oil.
The length of time required for treating the oil depends largely upon
its nature, some oils being more neutral and more nearly odorless than
others, consequently no exact rule can be laid down that would fit all
cases; it must be left to the judgment of the person handling the oil.
_Pressure and Temperature._--To obtain the temperature above mentioned
a pressure of 150 pounds should be carried, and late practice
introduces a superheater for reheating the steam to insure high
temperature by adding 100° to 150° F. to the steam temperature.
[Illustration: FIG. 156.--SECTION OF BOTTOM OF DEODORIZING TANK.]
_Bleaching Process._--As soon as the oil is deodorized it is drawn off
and allowed to cool. It is pumped into the treating kettle, or what is
known in refineries as the “dirt” kettle. There it is brought up to
a temperature of 160° F., when the fullers earth is added, generally
using from one to two percent of earth with this bleach, following an
agitation of about ten minutes. It should then be pumped through the
filter press into the receiving tank, where it is held until used.
After going through this process the oil is known to the trade as
“water white.”
[Illustration: FIG. 157.--SECTION THROUGH EXHAUST HOOD OF DEODORIZING
TANK.]
_Mixing._--Refined tallow or oleo stearine melted and clarified by
pumping through a filter press without the use of fullers earth is
added to the cotton seed oil so prepared, and the mixed substance,
containing proportions previously described, are ready for passing over
the cooling roll.
_Filter Press._--The filter press (Fig. 158) should not be used more
than two or three times until it is taken apart, all the sediment and
dirt removed and clean cloths substituted. Continued use of filter
cloths, without proper cleaning, has a deteriorating effect upon the
material pumped through the presses, and different kinds of products
should not be passed through the same press.
_Color and Roll Treatment._--Color is an important feature of compound,
when an odorless oil has been produced. The mixture passed to the rolls
is usually at a temperature of 120° F. and this heated body of material
amounting to 4000 pounds per hour on an eight foot roll requires a very
large capacity of refrigerating equipment.
It is desirable to maintain a brine temperature in the shell of from
zero to five degrees above. A fifty-ton refrigerating equipment of
commercial rating is inadequate for this duty. Consequently compound
manufacturers must have ample refrigerating machine capacity.
The lard roll is preferably of the size noted and should operate at not
to exceed seven revolutions per minute, provided brine of the above
temperature is supplied; fewer revolutions if temperature is higher,
which naturally reduces the capacity.
The lard roll, pump, and strainer equipment is the same as described
for lard, except that the lard is packed directly from the picker
trough without the use of an additional agitator.
=Hydrogenation of Oils.=--A new process has been devised whereby soft
oils, such as cotton seed oil, can be hardened so as to make a purer
vegetable product. The substance has quite a large field but it is not
intimately connected with the packing business.
=Cotton Seed Stearine.=--This is a purchasable product and is used at
times as a substitute for oleo stearine.
=Lard Oil.=--The production of lard oil used in compounding
lubricating oils and illuminating oils is still carried on to some
extent. The process consists of graining the oils in graining tanks or
in seeding trucks similar to oleo oil graining trucks.
_Pressing._--The lard cooled to a temperature of 40° F. is placed in
cloth wrapper arranged so that all oil is strained through the wrapper.
The solid substance contained in the wrapper is lard stearine used to
harden pure lard.
[Illustration: FIG. 158.--FILTER PRESS FOR LARD OR OLEO OIL.]
_Graining._--After the fats have been washed they should be drawn into
trucks or tierces and placed in a room where there is good ventilation,
and kept there for about two days, giving the acid fumes an opportunity
to pass off; the fat will then be found to be lowered to about 80°
F. and should then be removed to a room that is refrigerated. After
remaining in this temperature three or four days the fats will be found
to be crystallized, or grained, and of about the temperature of the
rooms. It is then ready to go to press.
=Pressing Temperatures.=--The usual pressing temperatures for the
several kinds of commodities pressed are as follows:
Tallow 58° to 65° F.
Prime steam lard 48° to 50° F.
Neatsfoot oil 45° to 48° F.
These and the temperature of the room, however, are subject to
variations.
=No. 2 Lard Oil.=--A lower quality of lard oil is made from hog
greases. These are made from condemned hogs, catch basin skimmings and
similar sources. The methods are similar to those used for No. 1 lard
oil, except that the former is treated as an edible product and the
latter as inedible.
The extracted stearine is sold or used for soap purposes.
=Cold Test-Oil.=--It is not customary to speak of any particular cold
test of cotton or grease oils; however, in case of pure lard oil,
pressed, it would have a cold test of about 42° F. Pure neatsfoot
would have a cold test of about 45° F. In case colder degree oils are
desired, either pure lard or neatsfoot, it would be necessary to make
the lard colder than above; as to neatsfoot oil, if it is desired to
make a 30° F. test, it would be best to make two pressings. First chill
stock to a temperature of 42° F., pressing it in a room at 45° F. and
then take the oil that is made in this way, refrigerating it in a room
at 32° F. and pressing it at a temperature of 32° F.
=Treatment for Lard Grease.=--Before pressing the low grade greases it
is necessary to wash with sulphuric acid to eliminate the impurities,
such as water, lime soaps, albuminous matters and ordinary dirt.
Shallow wooden vats are ordinarily used for this purpose, the vats
being of greater width than depth, as the acid water settles best in
a shallow receptacle. Where a comparatively small amount of work is
to be done an ordinary wooden vat made out of good sound pine, with
three-inch staves and well bolted together, is all that is necessary,
but where the work is continuous these wooden vats should be lined with
ten-ounce lead, as the acid very soon destroys the vats.
_Washing Methods._--The method of washing with the sulphuric acid
is as follows: Into the wooden or lead-lined vat run clear water to
the amount of about 10 to 15 per cent of the weight of the grease to
be treated, and when the water is in, add one per cent of sulphuric
acid to the fat to be washed, the acid to be 66-degree density. It is
important that the water be put in first, for if the acid is put into
the tank first and the water afterwards run in, an explosion is liable
to occur on account of the intense heat generated by the absorption of
the water by the acid. In case of an explosion the acid is liable to be
thrown on the attendants. After the water and acid have been mixed, add
grease, turn on steam and boil until the fat and acid show clear; at
first it will be muddy or cloudy. Usually a boiling of twenty to thirty
minutes is sufficient. This work should be done on the top floor of the
building, or some place where there is ample room for the escape of the
vapor, as the fumes of the acid are very strong and are injurious to
the building. After the boiling is finished, allow the tank to settle
ten to twelve hours, draw off the acid water from the bottom, and if
the same is clear and clean it shows that the fat had little foreign
substance and the solution can be used over again. If it shows a great
deal of foreign matter in the solution it should be run away.
All pipes leading from such treating vats should be of lead. It is also
necessary that the pipes in the vats be of perforated lead coils, as
iron pipes would very soon be destroyed.
_Filtration._--At times, for bleaching purposes, and especially on low
grade greases, it is usual to refine and bleach the oil. The amount of
fullers earth to be used in filtering depends upon the condition of
the oil to be filtered. With prime steam lard no fullers earth should
be used; it is simply filtered through clean press cloths. In the case
of lard oils and tallow oils, the color of the oil desired must also
determine the amount of fullers earth to be used, no set rule as to the
amount to be used in every case being practicable.
Every manufacturer of these different grades of oils has his own grades
and standards established, to which the lard refiners usually work, and
the amount of bleaching, etc., which is necessary for each individual
lot should be governed by the knowledge of the operator, rather than by
any set rules.
In the pressing of these articles the oils generally run from 40 to 52
per cent of stock, the balance being stearine, the percentage of oil
obtained varying according to the temperature at which it is pressed,
and according to the relative market prices for oils and stearines.