MOTIVE POWERS PRODUCED WITH NEW ECONOMY--_Continued_. HEATING SERVICES
Producer gas . . . Mond gas . . . Blast furnace gases . . . Gas
engines . . . Steam and gas engines compared . . . Diesel oil engine
best of all . . . Gasoline motors . . . Alcohol engines . . . Steam
and gas motors united . . . Heat and power production combined . . .
District steam heating . . . Isolated plants . . . Electric traction
and other great services . . . Gas for a service of heat, light and
power.
Gas-Power.
Steam as motive power finds its most formidable rival in cheap gases,
whose familiar varieties have been long used for illumination. A simple
experiment shows with what ease gas can be made, which, duly cooled, may
be carried long distances without the condensation which subtracts from
the value of steam. Take a narrow tube of metal or Jena glass, open at
both ends: put one end near the wick of a burning candle, at the other
end apply a lighted match, and at once a flame bursts forth. Here is a
miniature gas-works; close to the wick inflammable gases are generated
by the heat, before they have time to burn they are conveyed through the
tube to a point a foot distant where, on ignition, they yield a
brilliant flame. Enlarge this operation so that instead of an ounce of
wax you distill tons of coal from hundreds of big retorts; set up a
gas-holder as huge as the dome of the Capitol at Washington; instead of
short tube lay miles of pipe through the avenues and streets of a city,
and a trivial experiment widens into lighting a hundred thousand homes.
So much for dividing combustion in halves, by conducting gasification in
one place on a vast scale, and burning the produced gas whenever and
wherever you please. One supreme advantage of the process is that coal,
wood and other sources of gas much cheaper than wax or oil can be
employed. Alongside the retorts which gasify coal or wood are built
scrubbers which remove substances undesired in the gas,--tar, sulphur,
and so on,--all salable at good prices. It was in 1792 that William
Murdock, an assistant to James Watt at the Soho Works near Birmingham,
there originated gas-lighting. His enterprise was a seed-plot for a
variety of industries which have reached commanding importance, and are
to-day expanding faster than ever before. Illuminating gas from its
first introduction has on occasion wrought disaster; when it leaks
through a joint into a room it rapidly unites with air; instantly on the
intrusion of a flame there is a violent explosion, that is, an abrupt
output of enormous energy set free under circumstances which do only
harm. Can the energy, as in the case of blasting, be usefully directed?
[Illustration: Combustible gas from a candle is taken through a tube to
a distance and there burnt.]
Yes, as long ago as 1794, Robert Street designed a pump driven by the
explosion of turpentine vapor below the motor piston. He was followed by
inventors who used illuminating gas as their propelling agent; among
these, in 1860, was Lenoir of Paris, who built a double-acting engine
with a jump-spark electric igniter such as to-day is in general use. His
engine consumed 95 feet of gas per hour for each horse-power, which
meant that commercially the engine was a failure. Lenoir’s design has
been so much improved that now large gas engines yield in motive power
one fifth of the whole value of their fuel, an efficiency twice that of
the best steam engines or turbines, and five-fold better than that of
Lenoir’s apparatus.
Producer Gas.
How this remarkable result has been attained we shall consider a little
further on, as we briefly examine the construction of a typical gas
engine. At this point let us note how a gas, suitable for an engine, is
manufactured at least cost, the outlay being much less than in the case
of illuminating gas which represents but one third of the coal placed in
the distilling retorts. Instead of this process of distillation,
“producer” gas is due to a modified combustion which gasifies all the
fuel. In a producer of standard type, atmospheric oxygen comes into
contact with the glowing carbon of the coal or wood, forming carbon
dioxide, CO². The heat generated by this union is taken up by the carbon
dioxide and the nitrogen of the supplied air. These gases as they rise
through the fuel bring it to incandescence so that the carbon dioxide
takes up another atom of carbon, becoming carbon monoxide, CO, a highly
combustible gas. Were there no impurities in the fuel, were the entering
air quite free from moisture, the gases would be in volume 34.7 per
cent. carbon monoxide and 65.3 per cent. nitrogen, with a heating value
per cubic foot of about 118 British thermal units, a unit being the heat
needed to raise a pound of water to 40° Fahr. from 39°, where its
density is at the maximum. Gas thus produced is intensely hot; and as
usually it contains sulphur, dust, dirt, and other admixtures, their
removal by water in a scrubber would involve a waste of about 30 per
cent. of the fuel heat. This loss is much diminished by sending into the
producer not only air but steam, to be decomposed into oxygen and
hydrogen; the oxygen combines with carbon to form more carbon monoxide,
while the hydrogen is the most valuable heating ingredient in the
emitted stream of gases. Were only air sent through the producer, the
outflowing gases would contain nitrogen to the extent of 65 per cent.;
with a charge in part air and in part steam, this percentage falls to
52; as nitrogen is useless and wastefully absorbs heat, this reduction
of its quantity is gainful. By a duly regulated admission of steam, a
producer is kept at a temperature high enough to decompose steam, but
not so high as to send forth gases unduly hot to the purifier.
For water-gas the method is to blow steam into the fuel until
decomposition ceases; the steam is then shut off, the fire allowed to
recover intense heat, when more steam is injected, and so on
intermittently.
[Illustration: Taylor gas-producer.
R. D. Wood & Co., Philadelphia.]
A Gas Producer.
Producer gas is in more extensive use than water-gas. It is evolved in
apparatus of many good designs: let us glance at the Taylor gas producer
built by R. D. Wood & Company, Philadelphia. Its fuel enters in a steady
stream, in controlled quantity, through a Bildt automatic feed which has
a constantly rotating distributor with deflecting surfaces. The
incandescent fuel is carried on a bed of ashes several feet thick, so
that the coal gradually burns out and cools before its ashes are
discharged. Through a conduit an airblast is carried up through this
layer of ashes to where the fuel is aglow; united with this airblast is
a pipe admitting steam; the united air and steam are emitted radially.
In the producer walls are sight or test holes so placed that the line
dividing ashes from glowing fuel may at any time be observed. When this
line becomes higher on one side than the other, scrapers, duly arranged,
are used. At the bottom of the producer is a Taylor rotative table which
grinds out the ashes as fast as they rise above the desired depth, say
every six to twenty-four hours, according to the rate of working. In
large producers the ash bed is kept about three and a half feet deep, so
that any coal that may pass the point of air admission has ample time to
burn entirely out: in a producer with an ordinary grate such coal would
fall wastefully into the ashpit. As the Taylor ash table turns it grinds
the lower part of the fuel bed, closing any channels formed by the
airblast, and restraining the formation of carbon dioxide, a useless
product, to a minimum. A few impulses of the crank at frequent
intervals maintain the fuel in solid condition, reducing the need of
poking from above.
Other American producers differ from the Wood apparatus in details of
design and operation; in principle all are much alike. Any good producer
works well with cheap fuels, bituminous coals of inferior quality, culm,
lignite, wood, peat, tanbark, and even straw from the thresher. With
each of these there must be due modification of mechanism, together with
means of forcing air and steam into the fire. A suction plant may be
employed when superior fuels are burned, coke, anthracite, or charcoal;
with currents of air and steam automatically drawn into the producer,
the surrounding room is not likely to be filled with the harmful gases
which may be occasionally ejected by a pressure plant.
Mond Gas.
England has gas-power installations much larger and more elaborate than
those of America. Of these the most extensive have been built by the
Power-gas Corporation in London, under the patents of Mond, Duff and
Talbot. A Mond plant yields a gas having 84 per cent. of the calorific
value of the coal consumed, which may be slack at six shillings, $1.46,
per ton. Where more than thirty tons of coal per day are used, it is
worth while intercepting the sulphate of ammonia, amounting to 90 pounds
per ton of coal, which in small producers cannot readily be seized. Mond
gas is free from tar, is cleansed of soot and dust, and holds less
sulphur than ordinary producer gas. Operation is simple enough: first of
all the slack is brought into hoppers above the producers. From these it
is fed in charges, of from 300 to 1,000 pounds, into the producer bell,
where the first heating takes place: the products of distillation pass
downward into the hot zone of fuel before joining the bulk of gas
leaving the producer. This converts the tar into a fixed gas, and
prepares the slack for descent into the body of the producer, where it
is acted upon by an airblast saturated with steam at 185° Fahr., and
superheated before coming into contact with the fuel. The stream of hot
gases from the producer now traverses a washer, a rectangular iron
chamber with side lutes, where a water spray thrown by revolving dashers
brings down the temperature of the gases to about 194° Fahr. In plants
which recover the ammonia sulphate, the gas takes its way through a
lead-lined tower, filled with tiles of large surface, where it meets a
downward flow of acid liquor, circulated by pumps, containing ammonia
sulphate with about 4 per cent. excess of free sulphuric acid.
Combination of the ammonia with this free acid ensues, yielding still
more ammonia sulphate. The gases, freed from their ammonia, are
conducted into a cooling tower, where they meet a descending shower of
cold water effecting a further cleansing before the gases enter the main
pipe for delivery to consumers. In its general plan, a Mond plant
resembles an illuminating gas works, especially in its seizure of
profitable by-products. A ton of slack costing in England $1.46 yields
90 pounds of ammonia sulphate worth $1.92 or thereabout.[40]
[40] “Producer-gas and Gas-producers,” by Samuel S. Wyer, is a
treatise of value, fully illustrated. New York, Engineering and
Mining Journal, 1906. $4.00.
Blast Furnace Gases.
For many years flames from blast furnaces and coke ovens testified to
the waste of valuable gases, in especial the combustible carbon monoxide
which is the main ingredient in producer gas. When we learn that coal or
coke in iron-smelting parts with but three per cent. of its heat to the
ore, we begin to see how grievous was the waste so long endured. For a
few years past the gases sent forth from blast furnaces have been
employed to heat the incoming air for the blowers, and to raise steam
for engines. With twice the efficiency of steam motors the gas engine
renders it well worth while to rid furnace gases of their dust and dirt
so that they may not injure the mechanism they impel. An effective
cleanser acts by separating the gases from their admixtures by
centrifugal force. At the Lackawanna Steel Works, Buffalo, N. Y., eight
gas-engines, each of 1,000 horse-power, are run on blast furnace gases.
It may well prove that installations of this kind will bring other blast
furnaces into cities where the sale of electricity will form a large
item in the profits.
[Illustration: Four-cycle gas engine. I, admission valve. O, exhaust
valve.]
Gas Engines.
The first gas engines used gas and air at ordinary atmospheric pressure;
at due intervals the charge was exploded by a glowing hot tube exposed
by a slide-valve, or, according to the practice now general, by an
electric spark of the jump variety. In 1862 De Rochas patented, and in
1876 Otto built, an engine on a model still in favor. Its cardinal
feature is the compression of each charge. In the field of steam
practice, we know how great economy is realized by beginning work with
high pressures. A similar gain attends the compression of gases in a
cylinder before explosion; whatever their pressure before ignition, it
is trebled or quadrupled by ignition, returning a handsome profit on the
work of compression, The four-cycle operation devised by De Rochas
proceeds thus:--First, by drawing in a mixture of gas and air in due
percentages during an outward stroke of the piston. Second, this charge
is compressed by an inward piston stroke. Third, the compression charge
is ignited, preferably by an electric spark, when the piston moves
outward by virtue of a pressure initially extreme. Fourth, the exhaust
valve opens and the spent gases are ejected as the piston returns to
complete its cycle. As but one of the four piston journeys is a working
stroke, it is necessary to employ a heavy flywheel to equalize the
motion of the engine. When two or more engines are united, their piston
rods are so connected to a common shaft as to distribute the working
strokes with the best balancing effect. With four engines their piston
rods may be arranged at distances apart of 90 degrees, so that one
working stroke is always being exerted. This plan is adopted for the
gasoline engines of automobiles so that they are served by fly-wheels
comparatively small.
In his work on the gas engine, Professor F. R. Hutton discusses the
advantages and disadvantages of that motor.[41] By his kind permission
his main conclusions may be thus summarized, first as to advantages:--
[41] “The Gas-engine: a treatise on the internal-combustion engine
using gas, gasoline, kerosene, or other hydro-carbon as source of
energy.” By F. R. Hutton, professor of mechanical engineering in
Columbia University. New York, John Wiley & Sons. $5.00.
The heat energy acts directly upon the piston, without intervening
appliances. Fuel economy is greater than with steam, because there is no
furnace or chimney to waste any heat. No fuel is wasted in starting the
motor, or after the engine stops. The bulk, weight and cost of a furnace
and boiler are eliminated, as well as their losses by radiation. A gas
motor has a portability which lends itself to important industries, as
logging and lumbering. It may be started at once, with no delay as in
getting up a fire under a boiler; when the fuel-supply is cut off, the
motor stops and needs no attention: these are important in automobile
practice. Gas engines are gainfully united to systems of gas storage so
that a producer may be run at high efficiency when convenient, and its
gas held in holders till needed: this is helpful when a plant is worked
overtime, or is liable to stresses of extreme demand at certain hours of
the day. Incident to this is the advantage of subdividing power units in
a large plant: each motor may receive its gas in pipes without loss, to
be operated at will. The rapidity of flame propagation renders possible
a high number of shaft rotations per minute, so that a multi-cylinder
engine weighs little in comparison with its power. There is no liability
to boiler explosion, or trouble from impurities deposited by water in a
boiler. There is no exposed flame or fuel-bed requiring attention. The
mechanism of the motor is simple, and its moving parts are few. A gas or
oil engine furthermore enjoys a combustion which is smokeless. The fuel
requires no diluting excess of air, with its cooling effect and
incidental waste of energy. Dust, sparks and ashes are avoided, with
diminished risk of fire. Liquid or gaseous fuel can be served by pumps
or blowers so that the cost of handling is avoided.
As to disadvantages:--In a four-cycle engine there is but one working
stroke in four piston traverses. In a two-cycle engine there is one
working stroke in two traverses. For a given mean pressure the cylinder
of a gas engine must be larger than a double acting steam cylinder. In
single cylinder gas engines the crank effort is irregular; hence a heavy
fly-wheel is required, or, a number of cylinders must be joined
together, adding much weight. The motor does not start by the simple
motion of a lever or valve. It has to be started by an auxiliary
apparatus stored with energy enough to cause one working stroke. A steam
engine may be overloaded to meet brief demands for extra power: not so
with a gas engine. The extreme temperatures of the cylinder require
cooling systems by air or water, adding weight and involving waste of
energy; these temperatures furthermore may seriously distort the
mechanism while rendering lubrication difficult and uncertain.
Explosions of some violence may occur in exhaust pipes and passages,
unless the engine is carefully adjusted and operated. Imperfect
combustion clogs the working parts with soot or lampblack, especially
injuring the ignition appliances. Initial pressures are so high as to
cause vibration and jar. Governing is not easy, since explosion is all
but instantaneous. The normal motor runs at maximum efficiency only when
running at a certain speed. To vary that speed is much more troublesome
and wasteful of energy than with the steam engine.
Gas engines united to gas producers have been employed with success on
shipboard. This field, with its high premium on fuel reduction, which
means more space for cargo, is likely to be largely developed in the
near future. Soon, also, we may expect locomotives to exhibit a like
combination with profitable results.
Steam and Gas Engines Compared.
During 1904 and 1905 the U. S. Geological Survey compared at St. Louis a
steam engine with a gas engine, each of 250 horse-power, using 24
varieties of lignites and bituminous coals. The steam engine was of a
simple, non-condensing, unjacketed Corliss type, from the Allis-Chalmers
Company, Milwaukee. The gas engine was a three-cylinder, vertical model
from the Westinghouse Machine Company, Pittsburg. Its gas was supplied
by a Taylor gas producer furnished by R. D. Wood & Company,
Philadelphia, of the design illustrated on page 460.
The official report in three parts, fully illustrated, presenting the
tests in detail, was published by the Survey early in 1906. On page 978,
of the second part, 14 comparative tests are summarized. They show that
in the gas plant on an average 1.70 pounds of fuel were consumed in
producing for one hour one electrical horse-power; in the steam plant
the consumption was 4.29 pounds, two and a half times as much. With
apparatus adapted to a particular fuel, with larger and more economical
engines, better results would have been shown both by steam and gas. Yet
competent critics believe that the ratio of net results would have
remained much the same. The most important fact brought out in the tests
is that some fuels, lignites from North Dakota for example, have little
worth in raising steam, and high value in producing gas; their moisture
is a detriment under a boiler, it is an advantage in a gas producer. The
cost of this investigation is likely to be repaid many thousand-fold in
pointing out the best way to use fuels which abound in the Western and
Northwestern States and in Canada. See note, page 241.
Oil Engines.
In some cases petroleum is the best available fuel for an engine,
essentially much the same as a gas motor. A carburetor, or atomizer,
blows the oil into a fine mist almost as inflammable as gas. In small
sizes for launches, threshing machines, or work-shops of limited area,
the petroleum engine is a capital servant. In sizes of 75 horse-power
and upward the Diesel engine is not only the best oil engine but the
most efficient heat-motor ever invented. It involves a principle as
important as that of Watt’s separate condenser for the steam from his
cylinder.
[Illustration: Fire Syringe.]
To understand the Diesel principle let us begin by remembering that to
the compression of a charge in a gas engine there is a moderate limit;
if this be exceeded the heat of compression prematurely ignites the
gases, so as to prevent due action. The air in a bicycle tire is
compressed but moderately, and yet every man who has worked a bicycle
air-pump with energy knows that soon its cylinder grows warm to the
touch. On this very principle, that mechanical work is convertible into
heat, our grandfathers had an ingenious mode of producing fire. In a
syringe with a glass barrel they placed a piston fitting snugly. In a
cavity of this piston they fastened a bit of cotton wool soaked in
bisulphide of carbon. On forcing the piston suddenly into the cylinder,
the air, quickly compressed, became hot enough to set the cotton wool on
fire. The heat evolved in the compression of air is turned to account in
the Diesel oil engine so as to make it the most economical converter of
heat into work ever devised. First the mechanism compresses air alone to
500 pounds per square inch, then and then only the oil for combustion is
injected, to take fire instantly from the heat of the compressed air. A
governor regulates the period of burning; this is usually during one
tenth part of the stroke, the expansion of the burned products
completing the stroke. Because 500 pounds is a pressure out of the
question for the compression of the mixed charge of air and combustible
gas in an ordinary gas cylinder, the Diesel engine excels in economy any
gas engine thus far built. At Ghent in 1903 a Diesel engine developed
165 brake horse-power from crude Texas oil with the extraordinary net
efficiency of 32.3 per cent. At the St. Louis Exposition, 1904, three
Diesel engines, using oil costing three cents per gallon, delivered for
seven months, during eleven hours each day, at half-load, an average of
250 kilowatts at an expense for fuel of but three tenths of one cent per
kilowatt hour on the switchboard, including all generator and line
losses. Engineers of the first rank are convinced that the Diesel
principle may be successfully embodied in gas engines. That done, with a
success approaching the effectiveness of Diesel’s oil motor, we may
expect steam engines and turbines to be largely dismissed from service.
Gasoline Engines.
Gasoline, although higher in price than petroleum, is commonly used in
automobiles and launches. It can be atomized more quickly and fully, and
without heat. To equalize motion, minimize jars, and reduce the weight
of its fly-wheel, an automobile of high power has usually four cylinders
with cranks set at an angle of 90 degrees with each other. The inlet
valve is operated positively and, as a rule, is interchangeable with the
exhaust valve. The ignition spark is furnished by a motor-driven
magneto, or by a battery operating an induction coil; the lubricant is
distributed by a sight-feed system, hand regulated. Cooling is effected
by water circulated by a pump through jackets surrounding all cylinders
and valves, each jacket having a surface of the utmost extent upon which
a swiftly rotated fan drives a stream of air.
Alcohol Engines.
For some years France and Germany have used alcohol as a fuel in
engines, no excise tax being imposed on alcohol employed for industrial
purposes. On January 1, 1907, this will also be the case in the United
States, so that we may expect alcohol to take a leading place as fuel in
motors. “It has,” says Professor Elihu Thomson, “gallon for gallon less
heating power than gasoline, but equal efficiency in an internal
combustion engine, because it throws away less heat in waste gases and
in the water jacket. A mixture of alcohol vapor with air stands a much
higher compression than does a mixture of gasoline and air without
premature explosion. . . . There is now beginning an application of the
internal combustion engine for railroad cars on short lines which are
feeders to main lines. The growth of this business may be hampered in
the near future by the cost of gasoline. In this case alcohol,
producible in unlimited amount, could be substituted.”
An important advantage in using alcohol is its comparative safety. In
case of fire oils and gasolines float on the water intended to quench a
blaze; alcohol blends with that water and the flame is subdued.
Whether oil, gasoline or alcohol be their fuel, internal combustion
motors gain steadily in public acceptance. On the farm they are
gradually displacing the horse. An engine, which costs nothing when it
is idle, shells corn, saws wood, cuts fodder, grinds feed, separates and
churns cream, drives a thrasher, turns a mill, lifts water, and performs
a hundred other chores quickly, simply and cheaply.
Steam and Gas Motors United.
Mr. Henry G. Stott, chief engineer of the Interborough Rapid Transit
Company, New York, has recently discussed power plant economies in so
thorough and suggestive a manner as to elicit the interest of engineers
the world over.[42] Basing his remarks on the records of the huge plant
of his Company at 74th Street and the East River, New York, he presents
this table of the average losses in converting the heat from one pound
of coal into electricity:--
[42] Before the American Institute of Electrical Engineers, New
York, January 26, 1906.
Heat of the coal as burned, 14,150 British thermal units 100.0%
Returned by feed water heater 3.1
„ „ economizer 6.8
------
109.9
Loss in ashes 2.4%
Loss to stack 22.7
Loss in boiler radiation and leakage 8.0
Loss in pipe radiation 0.2
Delivered to circulator 1.6
„ „ feed pump 1.4
Loss in leakage and high pressure drips 1.1
Delivered to small auxiliaries 0.4
Heating 0.2
Loss in engine friction 0.8
Electrical losses 0.3
Engine radiation losses 0.2
Rejected to condenser 60.1
To house auxiliaries 0.2 99.6
------------
Delivered to bus-bar 10.3%
Carbon dioxide (CO²) is absorbed by a solution of caustic potash. The
Ados recorder based upon this absorption has enabled Mr. Stott to learn
the proportion of carbon dioxide in the gases passing to the stack, the
higher that proportion, the more thorough the combustion. He finds first
as an element of economy careful firing, so as to avoid “holes” or thin
places in a fire, through which air wastefully pours, chilling the
furnace. Next in importance is adapting draft to fuel: small anthracite
requires a draft of 1.5 inches of water; with a draft of but .2 inch of
water one pound of dry bituminous coal has evaporated 10.6 pounds of
water, with a draft of 1 inch this fell to 8.7 pounds. Mr. Stott
estimates that scientific methods of firing can reduce losses to the
stack to 12.7 per cent., and possibly to 10 per cent.
Respecting the loss of 8 per cent. in boiler radiation and leakage, he
maintains that this is largely due to the inefficient setting of brick
which, besides permitting radiation, admits much air by infiltration.
The remedy is to employ the best methods of boiler setting, such as an
iron-plate air-tight case enclosing a carbonate of magnesia lining
outside the brickwork.
Regarding the main loss, that of 60.1 per cent. to the condenser, Mr.
Stott points out that superheating could reduce this by 6 per cent. He
observes that in the higher pressures of a steam cycle a reciprocating
engine has an advantage, while in the lower pressures a steam turbine is
more efficient. Combine them, he remarks, and use each where it is the
more profitable. But in his view for the utmost economy a new type of
plant should unite both steam and gas driven units.
“Over a year ago,” he says, “while watching the effect of putting a
large steam turbine having a sensitive governor in connection with
reciprocating engine-driven units having sluggish governors, it occurred
to me that here was the solution of the gas engine problem; for the
turbine immediately proceeded to act like an ideal storage battery;
that is, a storage battery whose potential will not fall at the moment
of taking up load, for all the load fluctuations of the plant were taken
up by the steam turbine, and the reciprocating engines went on carrying
almost constant loads, whilst the turbine load fluctuated between
nothing and 8,000 kilowatts in periods of less than ten seconds.
“The combination of gas engines and steam turbines in a single plant
promises improved efficiency whilst removing the objection to the gas
engine, namely, its inability to carry heavy overloads. A steam turbine
can easily be designed to take care of 100 per cent. overload for a few
seconds; and as the load fluctuation in any plant will probably not
average more than 25 per cent. with a maximum of 50 per cent. for a few
seconds, it would seem that if a plant were designed to operate normally
with one half its capacity in gas engines and one half in steam
turbines, any fluctuations of load likely to arise in practice could be
taken care of.”
Discussing in detail the performance of such a plant, Mr. Stott
concludes that its average total thermal efficiency would be 24.5 per
cent., as against 10.3 per cent. in the plant whose record he had
presented.
Heating and Power Production United.
In the bill of particulars drawn up by Mr. Stott it was shown that no
less than 60.1 per cent. of the total heat from his fuel had gone into
the condenser where, joined to the stream of the East River, it had been
wasted. Had he used non-condensing motors the loss in exhausts would
have been larger, and yet when a non-condensing motor is joined to a
heating plant the whole investment may be much more profitable than
where condensing motors throw away all the heat of their exhausts. Long
ago some pioneer of unrecorded name, using a non-condensing steam
engine, warmed his factory or mill with its exhaust steam. In summer
that steam sped idly into the air, in winter it saved him so much coal
that his motive power cost him almost nothing. By thus uniting the
production of power and heat he showed, as few men have shown, how a
great waste may be exchanged for a large profit. In the Northern States
and in Canada the main use for fuel is for heating not only dwellings,
but the furnaces that pour out iron and steel, the ovens that bake
pottery, tiles, and so on. When but moderate temperatures are desired,
as in warming a house, exhaust steam serves admirably, and so might the
exhausts from gas engines. Indeed we here strike the key-note of modern
fuel economy which is that wherever possible fuel should first deliver
all the motive power that can be squeezed out of it, when and only when
the remainder of its heat, much the larger part of the whole, should be
used for warming.[43] This plan, already adopted in a good many cases,
can be vastly extended with profit. In blast furnaces the first task of
the fuel is performed at an extreme temperature; that work completed the
gases of combustion may be purified and sent into gas engines to produce
motive power at little cost.
[43] An excellent work, “The Heating and Ventilating of Buildings,”
by Rolla C. Carpenter, professor of experimental engineering,
Cornell University, is published by John Wiley & Sons, New York.
Fourth edition, largely rewritten and fully illustrated. 1902,
$4.00. It incidentally describes the best methods of heating with
exhaust steam.
Heating and Ventilating by Fans.
A word was said on page 380 regarding the method now growing in favor
for heating machine-shops by sending warmed air where it is needed, and
not allowing it to go where it would proceed of itself and be wasted.
Two illustrations show a Sturtevant ventilating fan-wheel, without its
casing, and a Monogram exhauster and solid base heater, as used in many
modern installations. The net gain in sending warmed air just where it
does most good is comparable with the profit in mechanical draft for a
furnace as compared with natural draft. Either live or exhaust steam may
be used in the heating coils through which the air is forced by the fan.
See also illustration on page 380.
[Illustration: Sturtevant fan-wheel, without its casing.]
Steam plants which furnish both heat and electricity are being rapidly
multiplied throughout America. In many cases these plants supply a
single large hotel, or office building. The installation at the Mutual
Life Building, New York, is of 2400 horse-power, vying in dimensions
with many a central plant. In Fostoria and Springfield, Ohio, in
Milwaukee, Atlanta and other large cities, a central station provides
heat and light and motive power to a considerable district.
[Illustration: Sturtevant Monogram exhauster and solid base heater.]
District Steam Heating.
At Lockport, New York, a city of about 20,000 population, more than 350
dwellings and business premises are heated by the American District
Steam Company, a concern which has installed more than 250 similar
plants throughout the Union. The advantages of this system are
plain:--cleanliness is promoted; customers handle no coal or ashes, tend
no fires or boilers; the heat is more steadily and equably supplied than
if it came from individual boilers; heat is ready day or night during
the heating season; the hazard from fire is lowered and the risk of
boiler explosion is abolished; water may be heated for laundries,
bath-rooms and kitchens. Cheap fuel may be used, and stoked by
machinery. An individual boiler in a building has to be large enough for
its heaviest duty; in many cases it is called upon for but one tenth to
one fifth of its full power, with much incidental waste. At a central
station only as many boilers of a group are employed at a time as may be
worked to their full capacity, responding to the demands of the weather.
At Lockport the steam-pipes are of wrought iron covered with sheet
asbestos and enclosed in a round tin-lined wood casing, having a shell 4
inches thick, with a dead air space of about one inch between the tin
and the asbestos. In its largest size this pipe has shown a total loss
by radiation and conduction of but one part in four hundred in one mile;
for the same distance the smallest pipe has suffered a loss of six per
cent. Live steam is used at Lockport, but as a rule heating plants are
supplied with exhaust steam. When intensely cold weather prevails this
may be supplemented by boilers in reserve which supply live steam.
It is worth while to remark the tendency to unify, on lines of the best
economy, a service of both heat and electricity. In Atlanta there were
recently in operation twenty-two isolated electric plants. The central
station installed a steam heating system, and as a result in less than a
year all but two of the isolated plants went out of business.
Isolated Plants.
The success of the central station at Atlanta is due to the moderate
scale of its charges. In the past there has been some complaint of the
rates levied by central stations. In the future this complaint is likely
to diminish, because an isolated plant for the production of heat and
electricity was never before so low in cost, so efficient in working, as
to-day. Well managed central stations broaden their market by putting a
premium upon the utmost possible use of electricity. In Brooklyn, for
example, the Edison Electric Company charges 10 cents per horse-power
hour to customers using 100 to 250 horse-power hours per month; as
consumption increases so do discounts until the customer who buys 5,000
horse-power hours pays 4 cents. The demand for current in all its
diverse applications is stimulated with energy and address. A house or
apartment of seven rooms is wired for twelve lights, with all fixtures
complete, for $95. Signs for advertising purposes are provided _gratis_,
on condition that they be lighted by the Company. The economy of a small
ice machine or a refrigerator is pointed out all summer long, while in
winter the comfort and convenience of electric heat is as plainly kept
before the public. Such a policy as this takes account of the
irrepressible facts of present day competition. When gas was the sole
illuminant, producible only on a vast scale, served by an elaborate
scheme of piping that from the nature of the case fell into a single
hand, there was a liability to extortion. To-day in towns and cities
electricity, the chief source of light, can be ground out anywhere
simply, cheaply and without offence, incidentally affording when desired
almost as much heat as if the fuel had been burnt to produce nothing
else. Among the gifts bestowed by the electrician not the least is this
conferring at the lowest price two prime necessities of life. But
however liberal the management of a central station, many a fat plum
will remain outside its pudding. A huge hotel, an office-building,
factory, or department store, is best served by a plant of its own
designed to furnish both heat and electricity, in which case the
electric current will cost much less than if bought from a central
station.
On occasion an isolated plant supplies a neighborhood, and at prices
lower than those of a large central station which may be at a
considerable distance. At Newark in the New Jersey Freie Zeitung
building a 400 kilowatt plant is installed which supplies the neighbors
in two blocks with electricity at 6 to 8 cents per kilowatt hour,
according to the extent of their consumption. A necessary conduit
crosses Campbell Street in this service. It seems likely that small
power-centres of this kind, requiring no franchise, may be common in the
near future, especially if united with heating systems. An inviting
field for such installations is in the new residential quarters of our
cities and towns, where in many cases a whole block might be cheaply and
effectively served from a single plant.
Gas for Heat, Light and Power.
Heat, light and motive power may be provided either by steam or by gas.
Modern industry does not tie itself to any particular servant, but
chooses in turn whichever, under the circumstances of a case, will serve
it well at least cost. Where natural gas is to be had at a low price it
holds the field. But the area thus favored is small, so that producer
gas is employed on a much larger scale. We have already seen (page 461)
how coal may be gasified, valuable by-products seized, and a cheap gas
be piped for miles with no liability to the condensation which befalls
steam, while available for heating and for motive power. When this gas
burns at a fairly high temperature, as does Dowson gas, it gives with
thorium mantles a good light, so as to be an all round rival of
electricity. Producer gas is preferable to solid coal because perfectly
clean; it banishes the smoke nuisance, and is regulated by a touch. Mr.
F. W. Harbord in his work on Steel (see page 177), says:--
“The ease with which perfect combustion of a gas can be obtained by
regulating the supply of gas and air, the readiness with which it can be
conducted to any required point, superheated or burned under pressure,
made to give an oxidizing or a reducing flame at pleasure, and the
general control that can be exercised over the size and temperature of
the flame, in most cases more than compensate for the reduction in heat
units due to gasification. . . . The necessity for superheating the
fuel, and for keeping solid fuel out of contact with the bath of metal,
make gaseous fuel indispensable in the open hearth furnace, and until
Siemens solved the problem of cheap gasification of coal, this process
of steel-making was impossible.”
Gaseous fuels are employed not only in steel making but in the
manufacture of glass, pottery, chemicals, and much else.
When gas is used in gas engines to produce motive power, the exhausts
having high temperatures may be profitably applied to heating water, or
raising steam, for warming purposes.
Whether central stations employ steam or gas, or unite both, it is
certain that a unification of the service of heat, light, and motive
power including that required for traction, would in all our towns and
cities be attended by great economy, by the abolition of much discomfort
and unnecessary drudgery. A large city, such as New York or Chicago,
could be supplied with these three cardinal necessities from
comparatively few centres.
[Illustration: NEW YORK CENTRAL R. R. ELECTRIC LOCOMOTIVE WITH FIVE-CAR
TRAIN.]
Electric Traction.
Such centres may, before many years elapse, be found stretching out into
the distant suburbs of cities, and linking town to town. This chiefly
because electricity has become a formidable rival to steam in interurban
locomotion. By the time this page is printed, the New York Central &
Hudson River Railroad will have begun operating its suburban trains from
New York by electricity. For this service locomotives built by the
General Electric Company, Schenectady, New York, will be in commission.
Each will develop 2,200 to 3,000 horse-power. In careful tests a
locomotive of this kind reached a speed of fifty miles an hour in 127
seconds, whereas a “Pacific” steam locomotive required 203 seconds;
an important difference, especially where stops are frequent. Each
locomotive, with its train of cars, weighed 513 tons. The steam
locomotive with its tender weighed 171 tons; its electric rival weighed
but 100 tons. So much for the gain in leaving both furnace and boiler at
home, while their power is received through a special rail at rest.