PRODUCER-GAS
It may here be not amiss to point out the differences between
illuminating gas and those gases which are called in English "producer"
gases, and in French "poor" gases, because of their low calorific value.
=Street-Gas.=--This gas, the composition of which varies with different
localities, has a calorific value, which is a function of its
composition, and which varies from 5,000 to 5,600 calories per cubic
meter (19,841 to 24,896 B.T.U. per 35.31 cubic feet) measured at
constant pressure and corrected to 0 degrees C. (32 degrees F.) at a
pressure of 760 millimeters (29.9 inches of mercury, or atmospheric
pressure), not including the latent heat of the water of condensation.
The following table gives the average volumetric composition of
illuminating gas in various cities:
____________________________________________________________________
|
| Cities.
|______________________________________________
| | | | |
| | Manches- | New | |
| London. | ter. | York. | Paris. | Berlin.
_____________________|_________|__________|_______|________|________
| | | | |
Hydrogen | 48 | 46 | 40 | 52 | 50
Carbon monoxide | 4 | 7 | 4 | 6 | 9
Methane | 38 | 35 | 37 | 32 | 33
Various hydrocarbons | 4 | 6 | 7 | 6 | 5
Carbon dioxide | | 4 | 3 | | 2
Nitrogen | 5 | 2 | 8 | 4 | 1
Oxygen | 1 | ... | 1 | ... | ...
|_________|__________|_______|________|________
| | | | |
| 100 | 100 | 100 | 100 | 100
_____________________|_________|__________|_______|________|________
Furthermore, these constituents vary within certain limits. This is also
true of the calorific value. Experiments made by the author have
demonstrated that in the same place at an interval of a few hours,
variations of approximately ten per cent. occur.
=Composition of Producer-Gases.=--The average chemical composition of
producer-gases varies with the conditions under which they are generated
and the nature of the fuel. The following are the proportions of its
constituents expressed volumetrically:
Table Headings--
A: Blast Furnace.
B: Producer.
C: Mond.
D: Mixed (Fichet).
E: Water (Stache).
F: Wood (Riche).
________________________________________________________________________
|
| Gas.
|_________________________________________________
| | | | | |
| A. | B. | C. | D. | E. | F.
______________________|_______|_______|_______|________|________|_______
| | | | | |
Nitrogen and oxygen | 60 | 59 | 42 | 50 | 5 | 1
Carbon monoxide | 24 | 25 | 11 | 20 | 40 | 29
Carbon dioxide | 12 | 5 | 16 | 7 | 4 | 11
Hydrocarbons | 2 | 2 | 2 | 3 | 1 | 15
Hydrogen | 2 | 9 | 29 | 20 | 50 | 44
|_______|_______|_______|________|________|_______
| | | | | |
| 100 | 100 | 100 | 100 | 100 | 100
|_______|_______|_______|________|________|_______
Calorific value | | | | | |
in calories. | 950 | 1,100 | 1,400 | 1,300 | 2,400 | 2,960
Average weight of a | | | | | |
cubic meter in kilos| 1.30 | 1.1 | 1.02 | 1.05 | 0.680 | 0.824
Or of a cubic foot | | | | | |
in pounds | 0.008 | 0.007 | 0.006 | 0.0068 | 0.0042 | 0.0051
______________________|_______|_______|_______|________|________|_______
Blast-furnace gas has been used for generating power by means of
gas-engines for about ten years. At the present time it is used in
engines of very high power, a discussion of which engines more properly
belongs to a work on metallurgy, and has no place, therefore, in a
manual such as this.
Producer-gas, in the true sense of the term, is generated in special
apparatus either under pressure or by suction in a manner to be
described in the following chapters.
Mond gas is produced in generators of the blowing or pressure type from
bituminous coal, necessitating the employment of special purifiers and
permitting the collection of the by-products of the fractional
distillation of the coal. Mond gas plants are, therefore, rather
complicated and can be advantageously utilized only for large engines.
More exhaustive information can be obtained from the descriptions
published by the builders of Mond gas generators.
Mixed gas is generated in apparatus arranged so that the retort is kept
at a high temperature, thereby producing a gas richer in hydrogen than
that made by producers. It should be observed that in practice the
generators at present used yield a producer-gas, the calorific value of
which fluctuates between 1,000 and 1,400 calories per cubic meter (3,968
to 5,158 B.T.U. per 35.31 cubic feet); and the composition varies
accordingly, in the manner that has already been indicated in the tables
for producer-gas and mixed gas. There is no necessity, therefore, for
drawing a distinction between these two qualities of gas.
Water-gas should theoretically be composed of 50 per cent. carbon
monoxide and 50 per cent. hydrogen, resulting from the decomposition of
steam by incandescent coal. In practice, however, it contains a little
nitrogen and carbon dioxide. The gas is obtained from generators in
which air is alternately blown in to fan the fire and then steam to
produce gas. Water-gas is employed in soldering on account of its
reducing properties and of the high temperature of its flame. The great
quantity of carbon monoxide which it contains renders it very poisonous
and exceedingly dangerous, because it is generated under pressure. From
the economical standpoint, its generation is more expensive than that of
producer-gas, for which reason its employment in gas-engines is hardly
of much value.
Wood-gas, the composition of which has already been given, is generated
in apparatus of the Riche type, the principle of which consists in
heating a cast retort charged with any kind of fuel, namely wood, and
vertically mounted on a masonry base.
This apparatus should be of particular interest to the proprietors of
sawmills, furniture factories, and the like, since it offers a means of
using the waste products of their plants.
The relatively high proportion of carbon monoxide in producer-gas is
objectionable from a hygienic standpoint, so much so, indeed, that it
has attracted the attention of manufacturers. Carbon monoxide, the
specific gravity of which is 0.967, is a gas peculiarly poisonous and
dangerous. It cannot be breathed without baneful effects, and is even
more dangerous than carbonic-acid gas, which eventually causes
asphyxiation by reducing the quantity of oxygen in the air. For this
reason, it is necessary to take the utmost precaution in efficiently and
continuously ventilating the rooms in which the gas-generators and their
accessories are installed. This suggestion should be followed, above
all, when the apparatus in question are installed in cellars and
basements. As a further precaution, where the plant is rather large a
workman should not be allowed to enter the generator room alone.
Blowing-generators, or those in which the gas is produced under
pressure, are more dangerous than suction-generators. In the former a
leaky joint may cause the vitiation of the surrounding air as the
producer-gas escapes; in the suction apparatus the same fault simply
causes more air to be drawn in.
Dr. Melotte recommends the following procedure in cases of carbon
monoxide asphyxiation:
CARBON MONOXIDE ASPHYXIATION
Cases of poisoning by carbon monoxide are both frequent and dangerous.
The gas is extremely poisonous, and all the more dangerous because it is
odorless, colorless and tasteless. When it comes into contact with the
blood, it forms a combination so stable that it is reacted upon by the
oxygen of the air only with difficulty. It follows, therefore, that with
each respiration of air charged with carbon monoxide, a certain quantity
of blood is poisoned. In consequence of this, there is a possibility of
poisoning in open air.
=Symptoms.=--The symptoms observed will vary with the manner in which
the blood has been poisoned. There are two ways in which this poisoning
can occur. The one depends upon whether the atmosphere contains an
excess of carbon monoxide; the other whether the air breathed contains
only traces of the gas.
=Gradual, Rapid Asphyxiation.=--At first a vague sickness is felt,
rapidly followed by violent headaches, vertigo, anxiety, oppression,
dimness of vision, beating of the pulse at the temples, hallucinations,
and an irresistible desire to sleep. If at this stage the patient has a
sufficient idea of danger to prompt him to open a window or door, he
will escape death.
In the second stage, the victim's legs are paralyzed, but he can still
move his arms and his head. The mind still preserves its clearness, and
in a measure assists the further process of asphyxiation because of its
impotency. Then follow coma and death.
=Slow, Chronic Asphyxiation.=--Slow, chronic asphyxiation is not
infrequent. Its symptoms are often difficult to detect. Poisoning is
manifested by weakness, cephalalgia, vomiting, pallor, general anemia,
lassitude, and local paralysis. If any of these symptoms appear in the
men who work in the vicinity of the producers, immediate steps should be
taken to prevent the possibility of carbon monoxide asphyxiation.
FIRST AID IN CASES OF CARBON MONOXIDE POISONING
It has already been stated that the oxygen of the air has no oxidizing
effect upon blood contaminated by carbon monoxide. Only a liberal
current of pure oxygen can oxidize the combination formed and render
hematosis possible. This liberal current can be obtained from an oxygen
tank of the portable variety, provided with a tube carrying at its free
end a mask which is held over the mouth and the nostrils. The
absorption of gas takes place by artificial respiration, which is
effected in several ways. The most practical of these are the Sylvester
and Pacini methods.
=Sylvester Method.=--The patient is laid on his back. His arms are
raised over his head and then brought back on each side of the body.
This operation is repeated fifteen times per minute approximately. The
method is very frequently employed and is excellent in its results.
=The Pacini Method.=--Four fingers are placed in the pit of the arm,
with the thumb on the shoulder. The shoulder is then alternately raised
and lowered, producing a marked expansion of the chest. This method is
the more effective of the two. The movements described are repeated
fifteen to twenty times each minute very rhythmically.
One or the other of these two methods of treatment should be immediately
applied in serious cases. Certain preliminary precautions should be
taken in all cases, however. The patient should be carried to a
well-ventilated and moderately heated room, stripped of his clothes, and
warmed by water-bottles and heated linen. Reflex action should be
excited, the peripheral nervous system stimulated in order to contract
the heart and the respiratory muscles, and the precordial region
cauterized. In addition to this treatment, the region of the diaphragm
should be rubbed and pinched, the skin rubbed, cold showers given,
flagellations administered, urtications (whipping with nettles)
undertaken, the skin and the mucous membranes excited, the mucous
membrane of the nose and of the pharynx titillated with a feather dipped
in ammonia, alcohol, vinegar, or lemon juice. Rhythmic traction of the
tongue is effective when carried out as follows: The tongue is seized
with a forceps and kept extended by means of a coarse thread. It is then
pulled out from the mouth sharply and allowed to reenter after each
traction. These movements should be rhythmic and should be repeated
fifteen to twenty times a minute.
All these efforts should be continued for several hours. When the
patient has finally been revived, he should be placed in a warm bed.
Stimulants such as wine, coffee, and the like should be administered. If
the head should be congested, local blood-letting should be resorted to
and four or six leeches applied behind the ears. It should be borne in
mind that the various steps enumerated are to be taken pending the
arrival of a physician.
IMPURITIES OF THE GASES
Most of the coal used in generating producer-gas contains sulphur.
Sulphuretted hydrogen is thus produced, which mixes with the gas and
imparts to it its characteristic odor. In some gas-generators, purifiers
are employed in which sawdust mixed with iron salts is utilized, with
the result that a combination is formed with the sulphuretted hydrogen,
thereby removing it from the producer-gas. In other forms of generators
a more summary method of purification is adopted, so that traces of
sulphuretted hydrogen still remain. Since this gas attacks copper, the
employment of this metal is not advisable for the following apparatus:
Generator (openings, cock for testing the gas); piping (gas-pressure
cocks, drain and pet cocks); engine (gas-admission cock, lubricating
joint in the cylinder, valves and cocks of the compressed-air
starting-pipe).
The distillation of coal in generators results in the formation of
ammonia gas. This also has a corrosive action on copper and its alloys;
but owing to its great solubility, it is eliminated by the waters of the
"scrubber" and does not reach the engine.
PRODUCTION AND CONSUMPTION
The quantity of gas produced in most generators varies from 6.4 to 8.2
pounds per cubic foot of raw coal burnt in the generator. The engine
consumes per horse-power per hour 70 to 115 cubic feet of gas, depending
upon its richness.