The equipment for this work consists of a single gas generator, rated at
150 h.p., and a three-cylinder, vertical gas engine of the same
capacity. The producer is a Loomis-Pettibone, down-draft, made by the
Power and Mining Machinery Company, of Cudahy, Wis., and is known as its
“Type C” plant. The gas generator consists of a cylindrical shell, 6 ft.
in diameter, carefully lined with fire-brick, and having an internal
diameter of approximately 4 ft. Near the bottom of the generator there
is a fire-brick grate, on which the fuel bed rests. The fuel is charged
at the top of the producer through a door (Fig. 1, Plate XX), which may
be left open a considerable time without affecting the operation of the
producer, thus enabling the operator to watch and control the fuel bed
with little inconvenience. As the gas is generated, it passes downward
through the hot fuel bed and through the fire-brick grate. This
down-draft feature “fixes,” or makes into permanent gases, the tarry
vapors which are distilled from bituminous coal when it is first charged
into the producer. A motor-driven exhauster with a capacity of 375 cu.
ft. per min., draws the hot gas from the base of the producer through an
economizer, where the sensible heat of the gas is used to pre-heat the
air and to form the water vapor necessary for the operation of the
producer. The pre-heated air and vapor leave the economizer and enter
the producer through a passageway near the top and above the fuel bed.
From the economizer the gas is drawn through a wet scrubber where it
undergoes a further cooling and is cleansed of dirt and dust. After
passing the wet scrubber, the gas, under a light pressure, is forced, by
the exhauster, through a dry scrubber to a gas-holder with a capacity of
about 1,000 cu. ft.
All the fuel used is carefully weighed on scales which are checked from
time to time by standard weights; and, as the fuel is charged into the
producer, a sample is taken for chemical analysis and for the
determination of its calorific power. The water required for the
generation of the vapor is supplied from a small tank carefully
graduated to pounds; this observation is made and recorded every hour.
All the water used in the wet scrubber is measured by passing it through
a piston-type water meter, which is calibrated from time to time to
insure a fair degree of accuracy in the measurement. Provision is made
for observing the pressure and temperature of the gas at various points;
these are observed and recorded every hour.
From the holder the gas passes through a large meter to the vertical
three-cylinder Westinghouse engine, which is connected by a belt to a
175-kw., direct-current generator. The load on the generator is measured
by carefully calibrated switch-board instruments, and is regulated by a
specially constructed water rheostat which stands in front of the
building.
Careful notes are kept of the engine operation; the gas consumption and
the load on the engine are observed and recorded every 20 min.; the
quantity of jacket water used on the gas engine, and also its
temperature entering and leaving the engine jackets, are recorded every
hour. Indicator cards are taken every 2 hours. The work is continuous,
and each day is divided into three shifts of 8 hours each; the length of
a test, however, is determined very largely by the character and
behavior of the fuel used.
A preliminary study of the relative efficiency of the coals found in
different portions of the United States, as producers of illuminating
gas, has been nearly completed under the direction of Mr. Alfred H.
White, and a bulletin setting forth the results is in press.[23]
_Tests of Liquid Fuels._--Tests of liquid fuels in internal-combustion
engines, in charge of Mr. R. M. Strong, are conducted in the engine-room
of Building No. 13.
The various liquid hydro-carbon fuels used in internal-combustion
engines for producing power, range from the light refined oils, such as
naphtha, to the crude petroleums, and have a correspondingly wide
variation of physical and chemical properties.
The most satisfactory of the liquid fuels for use in internal-combustion
engines, are alcohol and the light refined hydro-carbon oils, such as
gasoline. These fuels, however, are the most expensive in commercial
use, even when consumed with the highest practical efficiency, which, it
is thought, has already been attained, as far as present types of
engines are concerned.
At present little is known as to how far many of the very cheap
distillates and crude petroleums can be used as fuel for
internal-combustion engines. It is difficult to use them at all,
regardless of efficiency.
Gasoline is comparatively constant in quality, and can be used with
equal efficiency in any gasoline engine of the better grade. There are
many makes of high-grade gasoline engines, tests on any of which may be
taken as representative of the performance and action of gasoline in an
internal-combustion engine, if the conditions under which the tests were
made are clearly stated and are similar.
Kerosene varies widely in quality, and requires special devices for its
use, but is a little cheaper than gasoline. It is possible that the
kerosene engine may be developed so as to permit it to take the place of
the smaller stationary and marine gasoline engines. This would mean
considerable saving in fuel cost to the small power user, who now finds
the liquid-fuel internal-combustion engine of commercial advantage. A
number of engines at present on the market use kerosene; some use only
the lighter grades and are at best comparatively less efficient than
gasoline engines. All these engines have to be adjusted to the grade of
oil to be used in order to get the best results.
Kerosene engines are of two general types: the external-vaporizer type,
in which the fuel is vaporized and mixed with air before or as it is
taken into the cylinder; and the internal-vaporizer type, in which the
liquid fuel is forced into the cylinder and vaporized by contact with
the hot gases or heated walls of a combustion chamber at the head of the
cylinder. A number of special devices for vaporizing kerosene and the
lighter distillates have been tried and used with some success. Heat is
necessary to vaporize the kerosene as quickly as it is required, and the
degree of heat must be held between the temperature of vaporization and
that at which the oil will be carbonized. The vapor must also be
thoroughly and uniformly mixed with air in order to obtain complete
combustion. As yet, no reliable data on these limiting temperatures for
kerosene and similar oils have been obtained. No investigation has ever
been made of possible methods for preventing the oils from carbonizing
at the higher temperatures, and the properties of explosive mixtures of
oil vapors and air have not been studied. This field of engineering
laboratory research is of vital importance to the solution of the
kerosene-engine problem.
Distillates or fuel oils and the crude oils are much the cheapest of the
liquid fuels, and if used efficiently in internal-combustion engines
would be by far the cheapest fuels available in many large districts.
Several engine builders are developing kerosene vaporizers, which are
built as a part of the engine, or are adapted to each different engine,
as required to obtain the best results. Most of these vaporizers use the
heat and the exhaust gases to vaporize the fuel, but they differ greatly
in construction; some are of the retort type, and others are of the
float-feed carburetter type. To what extent the lower-grade fuel oils
can be used with these vaporizers is yet to be determined.
There are only a few successful oil engines on the American market. The
most prominent of these represent specific applications of the principal
methods of internal vaporization, and all except one are of the hot-bulb
ignition type. It will probably be found that no one of the 4-stroke
cycle, or 2-stroke cycle, engines is best for all grades of oil, but
rather that each is best for some one grade. The Diesel engine is in a
class by itself, its cycle and method of control being somewhat
different from the others.
An investigation of the comparative adaptability of gasoline and alcohol
to use in internal-combustion engines, consisting of more than 2,000
tests, was made at the temporary fuel-testing plant of the Geological
Survey, at Norfolk, Va., in 1907. A detailed report of these tests is in
preparation.[24] A similar investigation of the comparative adaptability
of kerosenes has been commenced, with a view to obtaining data on their
economical use, leading up to the investigation of the comparative fuel
values of the cheaper distillates and crude petroleum, as before
discussed.
_Washing and Coking Tests._--The investigations relating to the
preparation of low-grade coals, such as those high in ash or sulphur, by
processes that will give them a higher market value or increase their
efficiency in use, are in charge of Mr. A. W. Belden. They include the
washing and coking tests of coals, and the briquetting of slack and
low-grade coal and culm-bank refuse so as to adapt these fuels for
combustion in furnaces, etc.
This work has been conducted in the washery and coking plant temporarily
located at Denver, Colo., and in Building No. 32 at the Pittsburg
testing station, where briquetting is in progress. The details of these
tests are set forth in the various bulletins issued by the Geological
Survey.[25]
The washing tests are carried out in the following manner: As the raw
coal is received at the plant, it is shoveled from the railroad cars to
the hopper scale, and weighed. It then passes through the tooth-roll
crusher, where the lumps are broken down to a maximum size of 2½ in. An
apron conveyor delivers the coal to an elevator which raises it to one
of the storage bins. As the coal is being elevated, an average sample
representing the whole shipment is taken. An analysis is made of this
sample of raw coal and float-and-sink tests are run to determine the
size to which it is necessary to crush before washing, and the
percentage of refuse with the best separation. From the data thus
obtained, the washing machines are adjusted so that the washing test is
made with full knowledge of the separations possible under varying
percentages of refuse. The raw coal is drawn from the bin and delivered
to a corrugated-roll disintegrator, where it is crushed to the size
found most suitable, and is then delivered by the raw-coal elevator to
another storage bin. The arrangement of the plant is such that the coal
may be first washed on a Stewart jig, and the refuse then delivered to
and re-washed on a special jig, or the refuse may be re-crushed and then
re-washed.
When the coal is to be washed, it drops to the sluice box, where it is
mixed with the water and sluiced to the jigs. In drawing off the washed
coal, or when the uncrushed raw coal is to be drawn from a bin and
crushed for the washing tests, however, a gate just below the coal-flow
regulating gate is thrown in, and the coal falls into a central hopper
instead of into the sluice box. Ordinarily, this gate forms one side of
the vertical chute. The coal in this central hopper is carried by a
chute to the apron conveyor, and thence to the roll disintegrator, or,
in case it is washed coal, to a swing-hammer crusher. It will be noted
that coal, in this manner, can be drawn from a bin at the same time that
coal is being taken from another bin, and sluiced to the jigs for
washing, the two operations not interfering in the least.
The washed coal, after being crushed and elevated to the top of the
building, is conveyed by a chute to the coke-oven larry, and is weighed
on the track scale, after which it is charged to the oven. The refuse is
sampled and weighed as it is wheeled to the dump pile, and from this
sample the analysis is made and a float-and-sink test run to determine
the “loss of good coal” in the refuse and to show the efficiency of the
washing test.
The coking tests have been conducted in a battery of two beehive ovens,
one 7 ft. high and 12 ft. in diameter, the other, 6¼ ft. high and
12 ft. in diameter. A standard larry with a capacity of 8 tons, and
the necessary scales for weighing accurately the coal charged and coke
produced, complete the equipment. The coal is usually run through a roll
crusher which breaks it to about ½-in. size, or through a Pennsylvania
hammer crusher. The fineness of the coals put through the hammer crusher
varies somewhat, but the average, taken from a large number of samples,
is as follows: Through ⅛-in. mesh, 100%; over 10-mesh, 31.43%; over
20-mesh, 24.29%; over 40-mesh, 22.86%; over 60-mesh, 10 per cent. The
results of the coking tests are set forth in detail in the various
publications issued on this subject.[26]
Tests of coke produced in the illuminating-gas investigations before
referred to, and a study of commercial coking and by-product plants, are
included in these investigations.
_Briquetting Investigations._--These investigations are in charge of Mr.
C. L. Wright, and are conducted in Building No. 32, which is of
fire-proof construction, having a steel-skeleton frame work,
reinforced-concrete floors, and 2-in. cement curtain walls, plastered on
expanded-metal laths. In this building two briquetting machines are
installed, one an English machine of the Johnson type, and the other a
German lignite machine of very powerful construction.
The investigations include the possibility of making satisfactory
commercial fuels from lignite or low-grade coals which do not stand
shipment well, the benefiting of culm or slack coals which are wasted or
sold at unremunerative prices, and the possibility of improving the
efficiency of good coals. Some of the various forms of commercial
briquettes, American and foreign, are shown in Fig. 2, Plate XX. After
undergoing chemical analysis, the coal is elevated and fed to a storage
bin, whence it is drawn through a chute to a hopper on the weighing
scales. There it is mixed with varying percentages of different kinds of
binding material, and the tests are conducted so as to ascertain the
most suitable binder for each kind of fuel, which will produce the most
durable and weather-proof briquette at least cost, and the minimum
quantity necessary to produce a good, firm briquette. After weighing,
the materials to be tested are run through the necessary grinding and
pulverizing machines and are fed into the briquetting machines, whence
the manufactured briquettes are delivered for loading or storage. The
materials to be used in the German machine are also dried and cooled
again.
[Illustration: PLATE XXI.
Fig. 1.--Hand Briquetting Press.