166

THE COLLIERY GUARDIAN.

January 28, 1916.

(500 b.h.p.) that the plain steel plate was found to be
unworkable, and the outcome was the introduction of
the water-cooled sliding plate. In the 250 b.h.p. pro-
ducer a single water-colled plate is used, and in the
500 b.h.p. size two water-cooled plates are employed,
both plates working towards the centre of the fire. The
single water-cooled plate has holes of a certain diameter
distributed over the surface of the plate to. admit the
air and steam to the fire, whilst the plate is in position
and supporting the fuel column while charging.

The double water-cooled plates of the 500 b.h.p. size
have no holes, the air and steam being drawn through
the pre-determined space which intervenes when the
plates are in position and supporting the fuel above.

Another and more troublesome effect showed itself in
the largest size (500 b.h.p.) with regard to the water-
cooled plate, which was not experienced in the other
sizes having the single water-cooled plate, the speed of
the. double plate (38 in. per minute) being much too high
when the plates are being withdrawn after charging, as
it causes disturbance of the fuel: This creates a
large quantity of dust, which the cooler has to remove
from the gas, and at the same time the fuel bed becomes
much too open. A larger area of fresh coal comes into
contact with the incandescent fuel, and the hydrocarbons
of the bituminous coal are liberated much too quickly.
This not only tends to render the gas too rich, but
should the temperature be at all low, the lighter hydro-
carbons might escape through the fuel bod, and produce
tar, or, otherwise, should the temperature be too high,
a great quantity of soot would be present in the gas.

To overcome this apparent defect, a suitable resist-
ance is fitted in the main drum controller, which regu-
lates the speed of the motor in such a way that the
plates are withdrawn only at a reduced speed, allowing
the three other operations, viz., the inward travel of
the plate and the raising and lowering of the grate, to
remain the same as in the other sizes.

The following are representative analyses of samples
of gas taken under varying conditions :—

Table III.

Carbon mon-	1.	2.	3.	4.	5.	6.	7.
oxide 		10’9..	. 19’0..	. 18’0 .	. 15’3..	.15’4	18’4..	. 23’2
Hydrogen 		13’2..	. 10’7..	. 10’0..	. 10’2..	. 9’5..	. 11’4..	. 14’2
Methane		6'3..	. 4’8..	. 5’8..	. 6T..	. 5’4..	. 4’8..	. 2’3
Carbon dioxide	5’2..	. 4 8..	. 8’5..	. 7'3..	. 7’8..	. 7’4..	. 4’8
Oxygen 		0'2..	. 0'0..	. 0’0..	. 0’0..	. 0’0..	. 0’4..	. 0’0
Nitrogen		64'2..	. 60’7..	. 57’7..	. 61’1..	. 61’9..	. 57’6..	. 55’5
Calculated	100 ..	.100 ..	.100 ..	100 ..	.100 ..	.100 ..	.100
heat value*...	138'2..	.143-7..	.146’2..	.141’5..	.142’9..	.149’1..	151’4
* In B.T.U. per cu. ft. (higher value).							

The percentage of hydrogen is lower than usually met
with in gas from producers using anthracite coal, not-
withstanding the fact that the supply of steam was
increased above the normal. As much as 2*25 lb. of
water were vaporised to 1 lb. of coal gasified at various
times, as against the normal quantity of about 1*3 lb.
per lb. of coal gasified.

From 25 samples the average hydrogen content was
only 10-29 per cent., but the average calorific value of the
same 25 samples was 143’16 British thermal units per
cubic foot higher value.

As this producer is essentially of the high temperature
type, a high percentage of hydrogen would be expected
to be present in the gas, provided enough steam was
supplied, but this does not appear to be the case.
Undoubtedly a considerable quantity of steam is con-
densed due to its coming into contact with the fresh
fuel until this same fuel reaches an incandescent state,
but samples taken immediately after charging and just
before charging, and carefully analysed, show almost
identical results in the composition of the constituents
of the gases.

The percentage of methane is very high, about four
times the quantity usually met with in gas produced
from anthracite or coke. This high percentage brings
up the heating value of the gas which would be other-,
wise very low, owing to the low hydrogen content. This
relative proportion is very important in connection with
the gas engine itself. If the hydrogen could be still
farther decreased, still greater advantages would .be
obtained. One of the most important advantages would
be the compression of the gaseous mixture in the
cylinder, which could be increased considerably with
safety without increasing the risk of premature ignition,
and this would result in a higher thermal efficiency of
the engine being obtained.

Only two samples out of 35 taken show any trace. of
oxygen in the gas. This is accounted for by the density
of the fuel bed which is being subjected to the con-
tinual upward pressure of the rising grate. The only
samples containing traces of oxygen were always
obtained when the producer was newly started after a
complete clean out, i.c., when the producer was working
and producing gas from the coke charge prior to the first
charge of bituminous coal.

Various classes of bituminous coal are being gasified
most successfully by this produce]-, caking and non-
caking coals being found to be equally suitable. The
upward pressure of the rising grate causing the fuel to
become thoroughly homogeneous renders caking coal
just as suitable as' the non-caking variety. Small coal
has been found more suitable than large coal; but large
coal could be easily broken as required. Coal containing
a high percentage of ash curtails the period that the pro-
ducer can work without a complete clean out.

The approximate analysis of the coal used to produce
the gas, as shown in Table III., is as follows :—

Table IV.—Analyses of Dry Sample.

	Per c.	Per c.
Volatile matter, gas, tar,	, etc... 33’22	
Sulphur			 0’59	
	—	33’81
Fixed carbon 			 60’05	
Sulphur			 1’09	
Ash			 5’05	
		66’19
Moisture 			7 65
Specific gravity			1’304
Heat value per lb				13,790

Cost per ton delivered in works 13/3 (Lancashire) 1914.

The most important feature of the producer is the
entire absence of cleaning plant of any description, the
only auxiliary chamber to the producer itself being the
cooler, the general arrangement of which is shown in
fig. 3. The chief function of this chamber is to cool
the gas, which leaves the producer at a somewhat high
temperature.

Though the temperature of the gas before entering the
cooler is high, it is absolutely free of any tarry matter,
and when the gas leaves the cooler it is at atmospheric
temperature and ready for use in the engine.

In this cooler the soot, if present, is prevented from
reaching the gas main leading to the engine. Gas enters
the cooler at the base, the branch of which lias an expan-
sion joint fitted to prevent any fracture occurring on the
steam raiser pipe itself. The gas, after leaving the
coke or the lower half of the chamber, comes into con-
tact with a very fine gauze screen, which can be rotated
from the outside by means of a chain and pulley. This
screen prevents any soot leaving the chamber, as the
jets of water play on to the upper surface of the gauze,

1
J;

Fig. 3.—Sectional Elevation of Cooler.

and drive the soot downwards into the coke immediately
below. The coke itself has a separately controlled
water supply.

When the producer is started from cold, the gas is
produced from coke only, and if this gas coke is not
properly carbonised in the gas works, the gas may con-
tain a trace of the lighter hydrocarbons, which will
cause the fine mesh of the gauze screen to be slightly
coated with tarry matter if the screen is in the hori-

zontal position. To prevent this, the.screen is always
put into the upright position, and brought into circuit
as soon as the first charge of bituminous coal is fed into

the producer. By the time this is done, the coke has
become hot enough to have distilled off any tarry matter
which may have been present in the first charge of coke.

The introduction of a very fine gauze, having a mesh
of 80 divisions to the sq.in., is unique for freeing pro-
ducer gas from the various impurities met with; but
should the gas contain the smallest percentage of tarry
matter, this gauze would quickly become useless, and
the stoppage of the gas flow would result. A screen of
this kind is still working which has not been removed

from the cooler for over a year, and the mesh is as
clear as when first fitted.

Referring now to the flexibility of this bituminous pro-
ducer, bituminous coal again seems to play a very impor-
tant part by rendering the fuel bed capable of meeting
any sudden demand for an increased supply of gas when
the engine is working on very intermittent loads.

Anthracite is very difficult to ignite, and, likewise,
very quickly loses its temperature when the supplv of
air is curtailed. This is why a producer gasifying
anthracite is unable to supplv a sufficient volume of gas
quick enough to carry an increased load if suddenly

applied. Bituminous coal, which is rich in volatile
matter, is,' on the other hand, very ready to ignite, and
also maintains its temperature much longer than anthra-
cite, owing, no doubt, to the high percentage of oxygen,
ranging from 8 to 15 per cent., while anthracite very
seldom contains more than 3 per cent. This fact has a
great bearing upon the flexibility question.

Many experiments have been carried out on this
bituminous producer to ascertain exactly how long the
producer would be capable of retaining its temperature
while the engine was running entirely free, and yet be
high enough to produce gas in sufficient quantity and
quality to enable the engine to carry full load. One
of the smallest sizes, that is, of 100 b.h.p. capacity, has
often been called upon to run absolutely free for an
hour or more, and yet has developed full load in 70
seconds from the time of its application.

A more useful, and at the same time, more con-
vincing method of demonstrating the flexibility of the
producer, and its adaptability to work on very inter-
mittent loads, is the fact that a battery of these pro-
ducers of 250 b.h.p. is now producing gas on the suction
system from bituminous coal for driving gas engines
of 850 b.h.p. This installation generates current for a
series of very large cranes employed in the unloading
of coal from ships moored alongside a large wharf.

No extravagant claims are made with reference to
the coal consumption per b.h.p. The actual consump-
tion of 1-5 lb. per b.h.p., including all stand-by and
starting losses, is recorded during an ordinary week’s
work extending over several weeks on a fairly
constant load, with a load factor of about 68 per
cent. It is not possible to have clinker and ash
containing a large amount of partially burnt fuel in
this producer, as it is always run out entirely after the
completed period of running. No charge of bituminous
coal is ever introduced during the last 10 or 12 hours
of the completed run. This procedure is entirely
reversed when anthracite producers are shut down for
cleaning purposes, it being always necessary to keep
charging .the producer within one or two hours of closing
down, and when the producer is cleaned out completely,
it naturally follows that a large amount of unburnt fuel
is withdrawn, from the producer, together with the
clinker and ash, and it is nearly impossible to separate
it.

Though it is possible to obtain the extremely low fuel
consumption of 0-8 lb. of anthracite per b.h.p. hour on
a short forced trial, the fuel consumption distributed
over a period of, say, three months must be much higher,
due to the method of cleaning the plant, and also to the
higher stand-by losses caused by the increased supply
of air rendered necessary to retain the temperature of
the fire for easy restarting after the producer has been
standing idle for a time.

Careful consumption tests with bituminous coal
gasified in the producer show a net fuel consumption
of 1'47 lb. per b.h.p., including all losses week in and
week out. That is, igniting the fire on the Sunday after-
noon and running for 12 hours a day for five days, and
74 on the Saturday.

Russia’s Coal and Coke Imports.—According to the Custom
House report, Petrograd, for the first nine months of the year
1915 the quantity of coal imported amounted to 4,354,000
poods, value 953,000 roubles. This compares with 271,595,000
poods, value 42,726,000 roubles, and 314,016,000 poods, value
50,637,000 roubles, in the corresponding periods of 1914 and
1913 respectively. The corresponding figures for coke were
163,000 poods, value 57,000 roubles, compared with 32.503,000
poods, value 6,128,000 roubles, and 42,757,000 poods, value
8,182,000 roubles, again for 1914 and 1913 respectively.

The second of a series of lectures on “ Coal ” was delivered
by Dr. Marie Stopes, D.Sc., Ph.D., at University College,
on January 25. The lecturer dealt at some length with the
interesting recent work of David White on the subject of
the presence of lump-resin, which is frequent in tertiary
and mesozoic coals, and is generally supposed to separate
them from the carboniferous coals. This author records
lump resin in several American coals of carboniferous age,
and also resin threads in peculiarly preserved medullosean
petioles. Some years ago, also, Mr. John Smith recorded
amber-like lumps in a Scottish carboniferous coal. It is to
be noted that in all these cases the coal is a low grade
one. David White considers that in coals with 65 per cent,
and more fixed carbon the resin has become too blackened
and altered for recognition microscopically. The presence
of plant debris of various kinds still recognisable in coal
was then dealt with. The remarkable “ paper ” coal of
Russia, which consists entirely of cuticles—chiefly of
Bothrodendron—was described as an extreme case of the
decomposition of all the plant substance except the most
tenacious cuticles. The presence of wood tissue, bark, roots,
leaves, and fructifications in the actual coal substance was
described and illustrated both by lantern slides and the actual
sections. Of these, some lantern slides of Dr. Hickling’s,
and some microscopic sections cut by Prof. Jeffrey, of
Harvard, were of particular interest as showing the tissue-
cells filled wnth the same clear substance as forms the
“ coal magma ” surrounding the cells. The full considera-
tion of this significant fact was deferred till other data
have been brought forward. “ Mother of coal ” was
described, the lecturer pointing out how7 extremely bad and
misleading this name is for the substance in question.
Mother of coal is really the carbonised remains of W'ood,
often in small chips or fragments like charcoal, but it is
very unlikely to have ever been formed by ancient forest
fires, as has often been supposed. It appears to be due
to exposure to the Mr during accumulation, so that the tissue-
wnalls were carbonised and the lumina left empty, instead
of being permeated by the decomposing, semi-fluid mass
of the true coal-forming magma. The next lecture will be
on Tuesday, February 1, and will deal wuth bogheads, algal
coals, etc. (Note : The course of lectures is open free to
those interested in mining, etc.)