AN IMPROVED APPARATUS AND PROCESS FOR MANUFACTURING ILLUMINATING GAS
Year: 1878

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
A
County of Middlesex, Patent Agent, for the Invention of "AN IMPROVED
APPARATUS AND PROCESS FOR MANUFACTURING ILLUMINATING GAS."
communication from abroad by Henry Wright Adams, M.D., A.M., of the City.
and County of Philadelphia, State of Pennsylvania, United States of America.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 24th May 1878.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "AN IMPROVED APPARATUS AND PROCESS FOR MANUFACTURING
ILLUMINATING GAS." [A communication from abroad by Henry Wright Adams,
M.D., A.M., of the City and County of Philadelphia, State of Pennsylvania, United
States of America.]
The object of this Invention is to make a larger quantity of gas from coal and
other similar materials than has heretofore been done, and to increase and cheapen
this production still further by the use of gas generated from water or steam, and
enriched by oil or other oleaginous matter. To do this I subject gas-yielding coal,
wood, peat, turf, or any other suitable gas-making and coke-producing materials, to,
destructive distillation in close retorts, in such a manner as to make no tar nor
ammoniacal liquor, as is now the case, or at least so trifling a quantity as practically
to amount to none, and by this means to increase very largely the production of
gas from coal, wood, peat, turf, or any other similar bodies capable of being resolved
into gas, tar, and coke.
The retorts now in common use are open at one end and closed at the other. The
stand pipe for the escape of the gas from the retorts is placed on its upper side near
its open end, which projects from the front side of the bench by means of a cast-iron
neck secured to the retort proper by a flange and bolts. When a charge of gas coal

page_text: is put in, the retort is usually at a cherry-red heat while the coal is cold. The first
effect is that the coal is heated up to the temperature of boiling water, which causes
a distillation of the water or moisture in the coal. As the heat of the coal is not
sufficient to decompose the steam thus generated into oxygen and hydrogen gases,
it escapes directly by the cool stand and condenses in the hydraulic main and cooler.
When the heat is sufficient some nitrogen unites with hydrogen and forms ammonia,
which is dissolved in the water and ammoniacal liquor is produced.
When the coal rises to a heat sufficient to distill off its bitumen, but not to
decompose it to permanent gas, this vapor of gas tar passes directly out of the retort
through a cool stand pipe, and condenses also in the hydraulic main and cooler. 1
This process of making tar and ammoniacal liquor from a fresh charge of coal
undergoing destructive distillation in the common coal gas retorts, goes on until tho
coal in the retort is raised to a red heat, when the bituminous matter in it is decom-
posed and converted into several fixed gases, which, when purified, are stored in
gasometers for illuminating purposes.
Each of the aforesaid.secondary products amounts to twelve gallons of tar, and
twelve gallons of ammoniacal water, or more, to the ton of coal.
The average production of gas from a ton of coal is not far from four and one
quarter feet to the pound, of coal, or eight thousand five hundred feet to twenty
hundred pounds.
The large amount of ammoniacal liquor over twelve gallons to the ton of coal,
consisting of nearly all water, is capable of being decomposed into oxygen and
hydrogen gases. The oxygen combines with the carbon of the red hot coal, and
produces carbonic acid and carbonic oxyd gases, the latter of which, with the
hydrogen generated, produces a very large volume of combustible gas, but poor in
illuminating quality.
The tar, the richest product of carbonaceous matter yielded by the coal, and the
most valuable part for gas making, is capable of being decomposed and converted
into a beautiful gas, excessively rich in carbon and possessing a very high degree of
illuminating power. When the former poor gas and the latter rich gas are made in
the same retort and at the same time, they unite in a nascent state and compose a
fixed gas of excellent quality. The quantity of gas is thus very largely increased
from the same charge of coal. This increase amounts to about one-third of the
present volume of gas obtained from a given charge of coal distilled in the ordinary
coal gas retorts having stand pipes on their front ends.
To effect an object so desirable I locate the coal to be distilled in the distilling
apparatus, so that the first vapors of tar and moisture which start out of the first
charge of coal at too low a heat to be decomposed shall be compelled to pass over
and through a considerable body of red hot coke or partially distilled coal, or other
decomposing surfaces, for a considerable distance before they reach the stand pipes,
and thus be converted entirely into fixed gas. This I do most effectually by the
means herein-after more fully described.
Having discovered the proper method of decomposing all the tar and ammoniacal
water which usually flow from a charge of coal in the ordinary destructive distilla-
tion of coal in the ordinary coal gas retorts, having the stand pipes on their front
ends, and consequently, having discovered the certain process of increasing very
largely the production of gas from a given weight of coal, wood, peat, turf, and
other similar substances.
Another object of my Invention is to take advantage of the red hot surfaces of
the coals or other coke-yielding substances undergoing destructive distillation in iny
retorts, to decompose oil, petroleum, naphtha, or any other suitable oleaginous
matter, and conjunctively therewith to decompose water, preferably superheated
steam, in order to increase the quantity and diminish the cost without impoverishing
the quality of coal gas produced from a given charge of coal or other similar
material.
During the latter part of the period of distillation the gas from the coal undergoing
such distillation grows poorer in carbon and richer in hydrogen. Its illuminating

page_text: power is thus lessened, and moreover its quantity is very considerably diminished
below the amount yielded during the first period of distillation.
By supplying a stream of oil, petroleum, naphtha, or other oleaginous body to the
rotort whose charge of coal has been partially distilled and converted into red hot
coke, in conjunction with superheated steam, the yield of gas from the coal is rein-
forced by the large volumes now generated in the same retort, and by means of the
same heat, and in the same time, from the oil and steam of superior brilliancy, with
no other cost or trouble except the expense incurred for the fluid gas-yielding
mattor, and the steam, now so abundant and cheap. A coal gas retort is thus
made to perform a triple duty, and produce a product novel in quantity and
economy.
In making gas from water, in conjunction with oil, petroleum, naphtha, or other
similar gas-yielding fluid and oleaginous materials, and with partially distilled
charges of coal in the same retort and by means of the same heat, I prefer to use
superheated steam, so as not to cool the retort by feeding into it water, or even
common wet steam.
It is better to convert the water into steam in a boiler, in the ordinary manner,
and then to superheat it by any of the known methods before it is admitted to the
retort charged with partially distilled coal or other similar body, into which oil and
other similar fluid inatters are fed at the same time. Then the process goes on
rapidly and beautifully without detriment to the proper decomposing heat of the
retort. The rich oil gas and the poor water gases mingle together in a nascent state,
and with the coal gas still being generated from the coal, unite together and compose.
a good fixed gas of excellent illuminating power.
Having stated the objects of the Invention, I will now show how the same may
be fully realised in practice.
Suppose a bench of four gas retorts set in a furnace and provided with all the
connections for operating them in the common method. The retorts are connected
together by cross pipes, so as to be operated in reciprocating pairs for generating
coal, oil, and water gas in conjunction in each retort. These pipes are also used for
mixing together the tarry and aqueous vapors and gases coming from a fresh charge
of coal or other gas-making and coke-yielding material in one retort, with oil,
petroleum, naphtha, or other suitable fluid matter and steam, and delivering them in
a mingled and heated condition into the other retort when charged with red hot
coke or partially distilled coal, or its equivalent, to be fully decomposed and recom-
posed into a fixed illuminating gas. In these two cross pipes are placed near their
opposite ends steam nozzles or toes looking towards each other, and being intended
to deliver jets of steam from steam pipes in connection with superheaters, composed
of cast-iron pipes about a foot in diameter and about eight feet long, placed in the
lower flues of the furnace, through which all its utilised gases are discharged into.
the stack. Here they get red hot without robbing the retorts of their needful heat.
Both ends of these superheaters are closed. A steam pipe, about half an inch in
diameter, more or less, enters such superheater at its outer end, which projects from
the front of the furnace and passes through its interior in a parallel direction, and to
within a few inches of its rear end. Its end is open, so as to deliver steam from a steam
boiler, with which this pipe is supposed to be connected, into the rear of the super-
heater, in order that it may have to travel back to the front end and be superheated
by contact with the interior sides of the red hot pipe. Cocks are placed on the
steam pipes to let steam into them from the boiler and to shut it off, and also to let
steain on to or shut it off from the retorts.
The cross pipes are about six inches in diameter, and are provided with valves
which are round and bevelled, so that they will pass through and wedge in a ring of
metal cast in the inside of the cross pipes, which ring is smaller in diameter than
the interior of the said pipes. These valves pushed into their seats or pulled out
from them, either close the communication between the retorts, or open it, as the
case inay be. The object of these valves is to shut the connection between the
retorts when charging one, so as not to lose the gas from the other.
•

page_text: Above the retorts is placed a reservoir of any desired size, for holding oil, petro-
leum, naphtha, or any fluid gas-yielding material. It should be made of boiler iron
and be perfectly tight, and is provided with a pipe for filling it by means of a pump
with a Boat, for indicating the quantity of oil in the reservoir, and with a safety
tube for allowing any vapor to escape, made long enough to pass up through the
roof of the retort house, and which may have a light safety valve at top. The oil
is drawn out of the reservoir through pipes at the under side, provided with valves
for opening and shutting said pipes, and is thence conducted to the cross pipes and
retorts through other pipes provided with bends about one foot long, in the form of
the letter U, for the purpose of preventing the gas in the retorts from blowing out.
These bent pipes are also provided with valves situated on one of the legs of the
respective bends, and with funnels for receiving the oil, petroleum, naphtha, or other
similar fluid which is to be fed into the cross pipes.
The stream of oil or other fluid gas-producing material when flowing through
these pipes falls through the cross pipes mixed with and heated by the superheated
steam and by the hot vapors coming from the fresh charged retort into the retorts,
and what is not vaporized or blown forward on to the red-hot coals by the steam
jets falls on to an inclined apron or gutter, which is placed in the mouth of each
retort when charged with coal or other similar body for the purpose of causing any
such liquid to flow back into the hotter part of the retort, and be delivered on to
the red-hot and partially distilled coal, and be converted to gas. This apron is
made of sheet iron, and has a hole punched through one end, so that a hook can be
run into it to pull it out of the retorts easily and quickly when the doors are
removed for the purpose of charging them.
Connected with the four retorts at their rear ends are four stand pipes, one foot
in internal diameter, so that they may not be liable to choke up with carbon. The
back ends of the retorts are always red hot, while their front ends are never so.
It is better therefore to allow the gas to escape from the back ends of the retorts,
which are always the hot ends, and which will cause a much more effectual decom-
position of the tar vapors in the gas than to take it from the cold ends in front, as
is the case with ordinary coal gas works. Besides, in all such works the tar-charged
vapors and moisture distilled from the front ends of their charges, lacking the
proper heat to decompose them to gas, pass directly into the cooler necks of the
retorts in front, and ascend the still cooler stand pipes, and condense abundantly in
the hydraulic main, and cause a great loss of heat.
By compelling the gas tar and aqueous vapors now formed in the front end of
the charges to pass through the red-hot ends of the retorts, and escape from red-hot
stand pipes, much less tar and much more gas can be made from a given charge of
coal. It is for this reason that the stand pipes are placed in the rear ends of the
retorts, and are made very large in diameter to protect them from filling up with
carbon.
Only a small quantity will form in their mouths, and to prevent the accumulation
of this I employ a tubular cutter having nearly the same diameter as the stand
pipes, and operated by an attached rod passing through a slot in the flanges or plugs
at their tops. These slots are oblong, so as to allow lugs on the rods of the cutters
to pass through them and rest on the top of the flanges, and so hold up the cutters
in the tops of the stand pipes when not in use. The joints are made sufficiently
tight by stiff pug or putty.
At any time when desired the engineer can go to the tops of the stand pipes and
turn the rods one-quarter round, so that the lugs on the rods will pass through
the oblong slots in the flanges, and thrust the cutters down the stand pipes and
into the retorts, and assure himself that they are open. This is a very great con-
venience.
The large diameters of these pipes and the tubular cutters with which they are
provided give ample security to the gas engineer that these important and most
exposed pipes will occasion no trouble. The outsides of these cutters are armed
with teeth or spiral cutting edges, so as to aid in removing any hard deposit which

page_text: may from time to time accumulate from neglect on the insides of these pipes near
and round their mouths and junctions with the retorts.
By putting the cross pipes on the front ends of the retorts outside of the furnace,
so that their valves and pipes cannot be harmed by the fire, and so that they can
be easily got at and opened and repaired, and by keeping forcible jets of steam
shooting through them, so that they cannot choke up, and by compelling the gas to
escape from the red-hot ends of the retorts in the rear and through red-hot stand
pipes, by which means the tar and aqueous vapor, hitherto so imperfectly distilled
and decomposed, which are discharged from the coal in the front ends of the retorts
are much more effectually and thoroughly converted into gas, I believe I have
effected a decided improvement in the destructive distillation of coal for illuminating
purposes.
Gas as it issues from the retort is always loaded with fine particles of carbon
which it is necessary to remove. This is now done by causing the gas to bubble
through the tar which seals the dip pipes in the hydraulic main; but the gas
escapes from the lower ends of the dip pipes in such large volumes as to prevent
proper contact with the sealing tar, and the result is that much of the fine carbon
is carried by the gas into the coolers, lime purifiers, and gas holders; in fact, any
one can notice it burning in every gas light in little sparks just above the tops of
the burners. To cause therefore a more thorough cleaning of the gas from this fine
carbon in the hydraulic main I bore a ring of holes about three-fourths of an inch
in diameter, and about half an inch apart, round and through the dip pipes, about
one inch above their bottom ends. I then fill the hydraulic main with a fluid here-
after to be described, so that these holes in the dip pipes shall be one inch, more or
less, below the level of the fluid in the hydraulic main, and their bottom ends be
two and three-quarter inches below the top surface of the sealing fluid. The effect
is that the gas generated in the retorts presses the fluid, whether it be tar or any
other proper liquid, down in the dip pipes until it comes to the ring of three-quarter
inch holes bored through their sides, and then escapes in divided and horizontal
streams shooting out in a ring of jets, presenting more gaseous surface to the fluid,
going further and remaining longer in it, and being more effectually stripped and
washed from its fine carbonaceous impurities.
The buckets under the dip pipe in the hydraulic main are fifteen inches in
internal diameter; they rest on the bottom of the main. Their tops are just high
enough to be on a horizontal line with the lower sides of the rings of holes per-
forated through the dip pipes one inch above their bottom ends. The effect of this
arrangement is that the dip pipes extend down into the buckets one inch. The
buckets cannot therefore get out of position, as they rest on the bottom of the main,
while their tops, being one and three-quarter inches below the surface of the fluid
in the main, allow the gas to shoot out through the ring of holes in the dip pipes,
and pass over the tops of the buckets and through the superincumbent fluid. By
raising them until their bottoms touch the bottoms of the dip pipes, or until the
seal is deep enough, the fluid which they carry up in them seals the holes in their
sides still deeper. This device enables me to turn the gas generated in one of the
reciprocating retorts into the other, as will hereafter be shewn. To operate these
buckets iron rods three-fourths of an inch in diameter are made fast to their
bottoms, and extending up centrally through the dip pipes, and pass through the
flanges and stuffing boxes on their tops. To the tops of these rods levers provided
with fulcrums are attached.
By elevating or lowering the long arms of the levers the buckets are raised or
lowered accordingly.
The hydraulic main is provided with an overflow pipe, which carries off the gas
and also the liquid accumulations. The level of the fluid in the main is flush with
the bottom side of this discharge pipe. Pipes are also provided for pumping any
liquid into the main and for drawing off its contents. Steam from a steam boiler
is also delivered in a forcible jet into the overflow pipe for the purpose of making

page_text: an exhauster to pump the gas from the retorts, and to prevent the damaging effect
of pressure of gas in them.
In the ordinary process of manufacturing coal gas from coal such a large quantity
of tar and ammonical water are made that the constant overflow of these products
from the discharge pipe attached to the hydraulic main carries off with it the fine
carbon mixed with the tar, and thus keeps the main free from its accumulations.
This is not the case with the present process. If I commence to inako gas with the
main filled with tar or some other fluid, in a few days the liquid in the main will
become so thick and viscid with the admixture of fine carbon injected into it by
the gas from the retorts that the flow of gas through the dip pipes is obstructed,
until finally the main has to be cleaned out and refilled. Nor can pure water be
used in the hydraulic main in place of tar, because the dry and hot lampblack or
Ininutely divided carbon which the gas brings abundantly out of the retorts in all
gasworks flies through the water without being moistened by it and penetrated, and
"consequently without being entangled in it and held back by it.
To provide
against this contingency I therefore mix water with soap, gelatine, gum, alkali, or
"other similar matters by which an emulsion, or a gelatinous, or mucilaginous, or
soapy fluid is prepared, in which pulverised charcoal will readily mix, and pump
this into the main as occasion requires, to keep it free from obstructions from this
source, and to wash the gas from this impurity. In preparing this fluid to fill the
main the rule to go by is this:-Take a given quantity of water, and mix with it
enough soap, gelatino, glue, gum, soda, potash, or oil, tar, or heavy petroleum, in
'which enough soda or potash has been mixed to form an emulsion with water, and
prepare a liquid with which pulverised charcoal will readily mix into a wet and
pasty mass. Such a fluid will answer well for the hydraulic main of any gasworks,
and will cleanse the gas from its lampblack in a satisfactory manner.
Having thus described the objects of this Invention, and one form of apparatus
for the accomplishment of these objects, I will now show what I deem to be the
best method of operating it, it being understood that these observations refer to a
bench of four retorts, as described in this Specification.
In the first place, I fill the hydraulic main, with a fluid prepared as before
described, up to a level with the discharge pipe, and kindle a fire in the furnace
under the retorts, and heat them up to a high cherry-red heat. I then take off the
doors of one of each pair of retorts, and charge then in the first instance with coke.
I then shut them up, and wait about one hour and a half, to let the coke in the
retorts become red hot, in order to be in a suitable condition to decompose the tarry
and aqueous vapors from the gas coal with which the corresponding retorts of each
part are to be charged.
It is understood that all the valves between the retorts and the hydraulic main
are now open. I now charge these last-mentioned retorts with two hundred pounds
of gas coal in each, and draw out the valve in the cross pipe, so as to open a com-
munication between the upper and lower reciprocating retorts. I also pull down
'the levers, which raise the buckets and seal the dip pipes, which communicate with
the gas coal retorts so deeply that the gas coming off from the two fresh charges
'put into them passes into the cross pipes, and through them into the two retorts
which are charged with red-hot coke. By passing over and through it the tarry
and aqueous vapours which are expelled from the coal in the other two retorts while
it is heating up to a red heat are decomposed into fixed gas. The tar gas and the
water gas from the coal being generated" together recombine in a nascent state,
and compose an illuminating gas of rare brilliancy. The gas passes in to the stand
pipes, and through the saddle pipes and dip pipes, which are in communication with
the coke retorts, and escapes through holes in the said dip pipes, whose buckets
are down, and whose rings of holes therefore have a less seal than the rings of holes
in the two dip pipes whose buckets are up. At the same time I open the oil valves
in the feed pipes which enter the cross pipes over the coke retorts. I also open the
two valves in the pipes on the oil reservoir, so as to cause oil, petroleum, naphtha,
or any other fluid gas-yielding material to descend into the two retorts charged

page_text: with red-hot coke, and to fall into the inclined aprons, which conduct it back into
the red-hot coke, where it is vaporised and decomposed into gas during its passage
through those retorts. I then admit jets of superheated steam into the cross pipes,
which, shooting from the nozzles therein, expand and make a pump in the mixing
pipes, and draw out the tarry and aqueous vapors and gases from the fresh charges
of coal in the retorts, and mix with them and with the streams of oil falling into
the pipes, and inject them together into the retorts charged with red-hot coke,
which are now in a suitable condition to receive theso mixod products and decom-
pose them, and recombine them into a fixed gas of extraordinary illuminating
power.
The steam is also admitted to make a pump in the overflow pipe and remove the
pressure from the hydraulic main, and draw the gas out of the retorts as soon as it
is generated. The retorts are to be kept up to a very high red heat, verging into
an incipient white. By giving them constant supplies of gas-yielding material a
higher degree of heat may be carried on the retorts, and gas be generated more
abundantly than with a low heat. This operation goes on steadily for two hours,
more or less, or until the charges of coal in the retorts have been distilled for one
half the period of time allotted to their distillation.
The gas is cooled, purified by lime, measured, and stored in gas holders in the
usual way.
At this period I prepare to draw the coke in the other retorts, and
to charge them with gas coal, by first closing the communication between each pair
of retorts, so as to prevent the gas escaping while the retorts are being charged;
the doors on the retorts are then loosened, and the oscaping gas fired to prevent a
"rap;" the aprons are drawn out and plunged into water to cool them, and the
coke is drawn from these retorts, which are then charged with about' two hundred
pounds of gas coal in each, the aprons put in, and the doors closed. Streams of
oil, petroleum, naphtha, or any other oleaginous fluid which may be employed are
then caused to fall into the mixing pipes, and jets of superheated steam aro
directed from the nozzles towards these streams of oil, which steam jets also in-
pinge against the interior sides of the pipes and tend to create a vacuum in the
rear of these points of impingement, and therefore to draw, by suction, the tarry
and aqueous vapors and gases from the fresh charges of coal in the retorts into
the mixing pipes, and inject them with the oil streams into the two other retorts
to be dispersed through and over their red-hot charges of partially distilled coal
and to bo decomposed conjunctively with the steam, and their elements, together
with the gas still being generated from the partially distilled charges of coal in.
theso retorts, recombined in their nascent state into a fixed gas of high illuminating
power, and passed through the red-hot stand pipes of these retorts into the
hydraulic main.
It is to be here observed that the course of the gas is now reversed. I wish
it also to be distinctly understood that the great novelty and utility of the In-
vention are now here completely unfolded and shown in this operation as dis-
tinguished from all processes of gas making hitherto known by me, viz., that the
fixed gas thus manufactured is a combination in one retort, at the same time and
by means of the same heat, of the gaseous elements derived from four distinct and
separate sources, viz., from the tarry and aqueous vapors and gases coming from
the fresh charges of coal in the reciprocating retorts, from the superheated steam
jets escaping from the nozzles, from the streams of oil, petroleum, naphtha, or any
other suitable oleaginous matter, and from the gas generated from the partially
distilled charges of coal in the retorts.
The poor gases generated from the steam combine in a nascent state with enough
of the excessively rich carbonaceous matter of the oil, petroleum, naphtha, or other
similar body, to make a good compound illuminating gas; while the coal, tar, and
ammoniacal water, now secondary and unutilised products in the ordinary coal gas
works, being decomposed together by this process so recombine as to produce a rich
and permanent gas.
So effectually do I decompose this coal, tar, and ammoniacal water, that I do

page_text: not make one drop of either when proper care is taken to maintain the heat of the
retorts at the proper degree. When it is considered that a ton of gas coal distilled
in the method now commonly practised produces not generally less than twelve
gallons of coal tar, and often more than this quantity of ammoniacal water, thus
making together twenty-four gallons or more of liquid gas-yielding products, which
when decomposed in conjunction and combined together, make a good fixed illumi-
nating gas, there can bo no good ground left for marvel at the assertion which I here
make, that this process of distilling coal produces at least one-third more gas from
a ton of coal of superior quality than the mode in common use by coal gas
companies. I do not get tar enough to seal the dip pipes in the hydraulic main,
and to meet this deficiency I am obliged to prepare water, as heretofore explained,
to seal them. Besides, by supplying oil and steam to the retorts in graduated and
constant streams during the latter part of the period of distillation, when their
charges of coal are red hot and are partially converted to coke, and in a suitable
condition to receive a reinforcement of gas-yiolding material, I keep up a flow of
gas from the retorts, uniform in quantity and quality, to the very end of the period
of distillation. By this means I confidently assert that I get as much gas and as
good gas out of one retort, and by the same heat, as can be obtained from two
retorts charged with coal alone and distilled for the same length of time. This
fact developes another economical value of the Invention. Only about one-half the
number of retorts are required to manufacture a given quantity of gas by this
process, compared with the number needed to produce an equal amount of gas by
the process now universally in use by coal gas companies. The expenses for labor
and material are correspondingly reduced.
The operations are to be continued as stated, charging each retort every four
hours, and reversing the gas, and the oil and steam feed, into the reciprocating
retort at the same time, and charging each retort two hours apart. This process
requires that the charge of coal, wood, peat, turf, or any other gas-yielding and coke-
producing material, shall be distilled for two hours in one retort before the products
of the other retort, together with the oil and steam, are turned into it and the
course of the gas reversed. This course is to be pursued when the period of
distillation of each charge of coal, or other similar materials, is limited to four
hours. But a longer or shorter period may be practised, provided that the middle
of the period of distillation, or thereabouts, of one retort shall be the time when the
other reciprocating retort shall be charged, and the course of the gas be reversed,
and the products of the fresh charge, together with the oil and steam feed, be turned
into the retort, whoso charge is red hot and partially distilled.
i
The forcible jets of steam, shooting first in one direction and then in the opposite
direction from the steam nozzles, perforin four different functions; they keep the
pipes clean by preventing in them the deposition or accumulation of tar or hard
carbon; they make a pump to draw out the tarry and aqueous vapors and gases
from the retorts when freshly charged, and inject them into the reciprocating retorts;
they act as carriers and force pumps to push and disperse the oil vapors and gases
through these last retorts, and discharge the gas finally from them; they furnish,
by decomposition, large volumes of gas to combine with the richer carbonaceous
vapors and gases, and to increase the production of good illuminating gas.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
23rd November 1878.
ALEXANDER MELVILLE Clark, of 53, Chancery Lanc, in the County of Middlesex,
Patent Agent.
AN IMPROVED APPARATUS AND PROCESS FOR MANUFACTURING
ILLUMINATING GAS." A. communication from abroad by Henry Wright Adams,
M.D., A.M., of the City and County of Philadelphia, State of Pennsylvania, United
States of America.
The object of this Invention is to make a larger quantity of gas from coal and
other similar materials than has heretofore been done, and to increase and cheapen
this production still further by the use of gas generated from water or steam, and
enriched by oil or other oleaginous matter. To do this I subject gas-yielding coal,
wood, peat, turf, or any other suitable gas-making and coke-producing materials to
destructive distillation in close retorts in such a manner as to make no tar nor
ammoniacal liquor as is now the case, or at least so trifling a quantity as practically
to amount to nono, and by this means to increase very largely the production of
gas from coal, wood, peat, turf, or any other similar bodies capable of being resolved
into gas, tar, and coke.
The retorts now in common use are open at one end and closed at the other. The
stand pipe for the escape of the gas from the retort is placed on its upper side neai
its open end, which projects from the front side of the bench by means of a cast-
iron neck, secured to the retort proper by a flange and bolts. When a charge of
gas coal is put in the retort is usually at a cherry-red heat, while the coal is cold.
The first effect is that the coal is heated up to the temperature of boiling water,
which causes a distillation of the water or moisture in the coal: As the heat of
the coal is not sufficient to decompose the steam thus generated into oxygen and
hydrogen gases it escapes directly by the cool stand pipe and condenses in the
hydraulic main and cooler. When the heat is sufficient some nitrogen unites with
hydrogen and forms ammonia, which is dissolved in the water, and ammoniacal
liquor is produced.
When the coal rises to a heat sufficient to distil off its bitumen but not to
decompose it to permanent gas this vapor of gas tar passes directly out of the retort
through a cool stand pipe and condenses also in the hydraulic main and cooler.
This process of making tar and ammoniacal liquor from a fresh charge of coal under-
going destructive distillation in the common coal gas retorts goes on until the coal
in the retort is raised to a red heat, when the bituminous matter in it is decomposed
and converted into several fixed gases, which when purified are stored in gasometers
for illuminating purposes.
Each of the aforesaid secondary products amounts to twelve gallons of tar and
twelve gallons of ammoniacal water, or more, to the ton of coal.
The average production of gas from a ton of coal is not far from four and onė
quarter feet to the pound of coal, or eight thousand five hundred feet to twenty
hundred pounds.
The large amount of ammoniacal liquor, over twelve gallons to the ton of coal,
consisting of nearly all water, is capable of being decomposed into oxygen and
hydrogen gases. The oxygen combines with the carbon of the red-hot coal, and
produces carbonic acid and carbonic oxide gases, the latter of which with the
hydrogen generated produces a very large volume of combustible gas, but poor in
illuminating quality.
The tar, the richest product of carbonaceous matter yielded by the coal, and the
most valuable part for gas making, is capable of being decomposed and converted
into a beautiful gas, excessively rich in carbon, and possessing a very high degree of
illuminating power. When the former poor gas and the latter rich gas are made in
the same retort, and at the same time, they unite in a nascent state and compose à

page_text: fixed gas of excellent quality. The quantity of gas is thus very largely increased
from the same charge of coal. This increase amounts to about one-third of the
present volume of gas obtained from a given charge of coal distilled in the ordinary
coal gas retorts having stand pipes on their front ends.
To effect an object so desirable I locate the coal to be distilled in the distilling
apparatus so that the first vapours of tar and moisture which start out of the first
charge of coal at too low a heat to be decomposed shall be compelled to pass over
and through a considerable body of red-hot coke, or partially distilled coal, or other
decomposing surfaces for a considerable distance before they reach the stand pipes,
and thus be converted entirely into fixed gas. This I do most effectually by the
means herein-after more fully described.
Having discovered the proper method of decomposing all the tar and ammoniacal
water which usually flow from a charge of coal in the ordinary destructive distilla-
tion of coal in the ordinary coal gas retorts, having the stand pipes on their front
ends, and consequently having discovered the certain process of increasing very
largely the production of gas from a given weight of coal, wood, peat, turf, and
other similar substances.
Another object of the Invention is to take advantage of the red-hot surfaces of
the coals or other coke-yielding substances undergoing destructive distillation in the
retorts to decompose oil, petroleum, naphtha, or any other suitable oleaginous matter,
and conjunctively therewith to decompose water, preferably superheated steam, in
order to increase the quantity and diminish the cost without impovershing the
quality of coal gas produced from a given charge of coal or other similar material.
During the latter part of the period of distillation the gas from the coal under-
going such distillation grows poorer in carbon and richer in hydrogen. Its illu-
minating power is thus lessened, and moreover its quantity is very considerably
diminished below the amount yielded during the first period of distillation.
By supplying a stream of oil, petroleum, naphtha, or other oleaginous body to the
retort whose charge of coal has been partially distilled and converted into red-hot coke
in conjunction with superheated steam the yield of gas from the coal is reinforced by
the large volumes now generated in the same retort, and by means of the same heat
and in the same time from the oil and steam of superior brilliancy with no other
cost or trouble except the expense incurred for the fluid gas-yielding matter and
the steam, now so abundant and cheap. A coal gas retort is thus made to perform
a triple duty and produce a product novel in quantity and economy.
In making gas from water in conjunction with oil, petroleum, naphtha, or other
similar gas-yielding fluid and oleaginous materials, and with partially distilled
charges of coal in the same retort, and by means of the same heat, I prefer to use
superheated steam so as not to cool the retort, by feeding into it water, or even
common wet steam.
It is better to convert the water into steam in a boiler in the ordinary manner,
and then to superheat it by any of the known methods before it is admitted to the
retort, charged with partially distilled coal, or other similar body into which oil and
other similar fluid matters are fed at the same time. Then the process goes on
rapidly and beautifully without detriment to the proper decomposing heat of the
retort. The rich oil gas and the poor water gases mingle together in a nascent
state, and with the coal gas still being generated from the coal, unite together and
compose a good fixed gas of excellent illuminating power.
Having stated the object of the Invention, I will now show how the same may
be fully realized in practice.
The Drawings which accompany this Specification, and which are made a part of
it, show one mode of carrying out the Invention.
Similar letters with similar primes, represent similar parts in all the Figures.
Figure 1 represents a working bench of four retorts coupled together in recipro-
cating pairs, with all their connections in perspective.
Figure 2 is a vertical section through the line x, x, Figure 3, showing a front
elevation of the hanch

page_text: Figure 3 is a vertical section on the line y, y, Figure 2, showing a section of one
retort and its various connections.
Figure 4 is a section through the hydraulic main, showing a section of the dip
pipes provided with a ring of holes above their lower ends, for causing the gas to
shoot through them into the fluid which seals them in horizontal jets, and to be
washed from lamp black; also showing the sealing buckets in relation theroto,
drawn through the line z, z, Figure 3.
Figure 5 is an elarged vertical section drawn through the line x, x, Figure 3,
showing the method of introducing steam and petroleum or other oil into a mixing
pipe. and pumping the tarry and aqueous vapors and gas from a reciprocating
retort, and mixing all these products together, namely, the tarry and aqueous vapors
and gases coming from a retort containing a fresh charge of coal or other similar
material, together with a streain of oil, petroleum, naphtha, or any other suitable
gas-making fluid and steam, and injecting them together in a mingled and heated
condition into a retort charged with rel-hot coke or partially distilled coal or other
equivalent material, and dispersing them through the same, to be decomposed and
recomposed into fixed illuminating gas.
Figure 6 is a perspective view of the inclined apron or oil gutter placed in the
mouths of all the retorts when charged with coal to receive the inflowing stream of
oil, petroleum, naphtha, or other fluid oleaginous matter, and conduct them back
into the interior of the retort and on to the red-hot coke or partially distilled coal,
and provent them from forming a puddle in the cooler necks of the retorts.
Figure 7 is an enlarged section on the line y, y, Figure 2, showing a tubular
cutter in all the stand pipes for keeping them clear of any disposition of carbon.
The following letters represent the following parts of the Invention:-
A shows a bench of four gas retorts set in a furnace, and provided with all tho
connections for operating them. They are set in reciprocating pairs. B, C, D, E, are
four retorts set in a furnace in the common method, and are connected together so
as to be operated in reciprocating pairs for generating coal, oil, and wator gas in
conjunction in each retort. F shows a pipe connecting together the retorts B, C,
and G shows a pipe connecting together the two retorts D, E. These pipes are also
used for mixing together the tarry and aqueous vapors and gasos coming from a
fresh charge of coal or other gas-making and coke-yielding material in one retort,
with oil, petroleum, naphtha, or other suitable fluid matter and steam, and delivering
them in a mingled and heated condition into the other retort, when charged with
red-hot coke or partially distilled coal or its equivalent, to be fully decomposed and
recomposed into a fixed illuminating gas. In these two cross pipes F and Garo
placed near their opposite ends steam nozzles or tees looking towards each other,
and being intended to deliver jets of steam. These nozzles in F are shown by H, I,
and in G by J, K. They are respectively connected to the steam pipes L, M, and
branches N, O, which steam pipes are also connected with the superheaters P, Q.
These are cast-iron pipes about a foot in diameter and about eight feet long, and
are placed in the lower flues of the furnace through which the furnace discharges all
its utilized gases into the stack. Here they get red hot without robbing the retorts
of their needful heat. Both ends of these superheaters are closed. R is a steam
pipe about half an inch in diameter, more or less, which enters the superheater P at
its outer end, which projects from the front of the furnace and passes through its
interior in a parallel direction, and to within a few inches of its rear end. Its end
is open so as to deliver steam from a steam boiler with which this pipe is supposed
to be connected into the rear of P, in order that it may have to travel back to the
front end, and be superlicated by contact with the interior sides of the red-hot pipe
P. S is a similar steam pipe, and similarly situated in the superheater Q, and is
intended to fulfil a similar office. T, U, are cocks on R, S, to let steam into them
from the boiler, and to shut it off. V is a cock on the steam pipe L to let steam
on to, or shut it off from the retort C; and W is a cock on M to let steam on to or
shut it off from the retort B. X is a cock on the steam pipe N, to let on steam of

page_text: shut it off from the retort E; and Y is a cock on the branch pipe O, to let on steam
or shut it off from the retort D. Z shows a valve in the cross pipe F. A' is its
seat; B' is the handle; C' is the stuffing box on F, through which the handle B'
works. D¹ is a similar valve on the pipe G; E¹ is its seat; F' is its handle working
through the stuffing box G¹. These rods are one inch and a quarter in diameter,
and are provided with auger handles on their ends, for pulling them out or pushing
them in.
The cross pipes F and G are about six inches in diameter. The valves Z and D'
are round and beveled, so that they will pass through and wedge in a ring of metal,
cast in the inside of the cross pipes F and G, which ring is smaller in diameter than
the interior of the said pipes. These valves pushed into their seats or pulled out
from them, either close the communication between the retorts B and C, and between
D and E, or open it, as the case may be.
The object of these valves is to shut the connection between the retorts when
charging one so as not to lose the gas from the other. H' is a reservoir for holding
oil, petroleum, naphtha, or any fluid gas-yielding material. It may be of any
desired size. It should be made of boiler iron, and be perfectly tight. I¹ is a pipe
for filling it by means of a pump. J' is a float for indicating the quantity of oil in
the reservoir. K' is a safety tube for allowing any vapor to escape. It should be
long enough to pass up through the roof of the retort house. Its top may have a
light safety valve. L, M, N, O, are pipes which enter the under side of H' for
the purpose of drawing oil out of it. P, Q, R, S', are valves for opening and
shutting these pipes. T, U, V, W', are four pipes for conducting oil, petroleum,
naphtha, or any other oleaginous matter to the cross pipes F and G, and from thence
to the retorts B, C, D, E. These pipes are provided with bends about one foot
long, in the form of the letter U, for the purpose of preventing the gas in the
retorts from blowing out. They are also provided with valves X, Y, Z, A",
situated on one of the legs of the respective bends. They are also provided with
funnels B, C, D, E, for receiving the oil, petroleum, naphtha, or other
similar fluid which is to be fed into the cross pipes F and G.
The stream of oil or other fluid gas-producing material when flowing through
these pipes falls through the cross pipes F and G mixed with and heated by the
superheated steam and by the hot vapors coming from the frosh charged retort into
the retorts B, C, D, E; and what is not vaporized and blown forward on to the
red-hot coals by the steam jets falls on to an inclined apron or gutter which is
placed in the mouth of each retort when charged with coal or other similar body,
for the purpose of causing any such liquid to flow back into the hotter part of the
retort and be delivered on to the red-hot and partially distilled coal and be converted
to gas. This apron is represented by B", Figure 6. It is made of sheet iron. A
hole is punched through one end, so that a hook can be run into it to pull it out of
the retorts easily and quickly when the doors are removed for the purpose of
charging them.
CC, CC, represent the four stand pipes, which are connected with the
four retorts B, C, D, E, at their rear ends. These stand pipes are one foot in
internal diameter, so that they may not be liable to choke up with carbon. The
back ends of the retorts are always red-hot while their front onds are never so. It
is better therefore to allow the gas to escape from the back ends of the retorts,
which are always the hot ends, and which will cause a much more effectual decom-
position of the tar vapors in the gas than to take it from the cold ends in front, as
is the case with ordinary coal gasworks. Besides, in all such works the tar-charged
vapors and moisture distilled from the front ends of their charges lacking the
proper heat to decompose them to gas pass directly into the cooler necks of the
retorts in front, and ascend the still cooler stand pipes, and condense abundantly in
the hydraulic main, and cause a great loss of gas.
By compelling the gas, tar, and aqueous vapors now formed in the front ends of
the charges to pass through the red-hot ends of the retorts, and escape from red-hot

page_text: stand pipes, much less tar and much more gas can be made from a given charge of
coal. This is the reason why I place the stand pipes in the rear ends of the retorts.
I make them very large in diameter to protect them from filling up with carbon.
Only a small quantity will form in their mouths, and to prevent the accumulation
of this I employ a tubular cutter having nearly the same diameter as the stand
pipes, and operated by an attached rod passing through a slot in the flanges or plugs
at their tops. These slots are oblong, so as to allow lugs on the rods of the cutters
to pass through them and rost on the tops of the flanges, and so hold up the cutters
in the tops of the stand pipes when not in use. The joints are made sufficiently
tight by stiff pug or putty. This cutter is shown by D", and the rod by E", and
the lug by Fi
At any time, when desired, the enginer can go to the tops of the stand pipes
and turn the rods one-quarter round, so that the lugs on the rods will pass through
the oblong slots in the flanges and thrust the cutters down the stand pipes and
into the retorts, and assure himself that they are open. This is a very great con-
venience.
The large diameters of these pipes and the tubular cutters with which they are
provided give ample security to the gas engineer that these important and most
exposed pipes will occasion no trouble. The outsides of these cutters are armed
with teeth or spiral cutting edges, so to aid in removing any hard deposit which
may from time to time accumulate from neglect on the insides of these pipes near
and round their mouths and junctions with the retorts. G¹¹, Figure 7, shows these
teeth or spiral cutting edges.
By putting the cross pipes F and G on the front ends of the retorts outside of the
furnace, so that their valves and pipes cannot be harıned by the fire, and so that they
can be easily got at and opened and repaired; and by keeping forcible jets of steam
shooting through them, so that they cannot choke up, and by compelling the gas to
escape from the red-hot ends of the retorts in the rear and through red-hot stand
pipes, by which means the tar and aqueous vapor hitherto so imperfectly distilled
and decomposed which are discharged from the coal in the front ends of the retorts,
are much more effectually and thoroughly converted into gas, I believe I have
effected a decided improvement in the destructive distillation of coal for illuminating
purposes.
Ê¹¹‚¤¹‚Œ¹¹‚Œ¹¹, show the four saddle pipes provided with steam pipes J", J",
J, J, attached to their upper ends for the purpose of blowing steam through
them to clean them. K", L, M, N₁, show the four dip pipes. Both the saddle
pipes and dip pipes are twelve inches in internal diameter, as by this process gas is
made so fast that the common sizes of these pipes are not sufficient.
Gas as it issues from the retort is always loaded with fine particles of carbon
which it is necessary to remove. This is done by causing the gas to bubble
through the tar which seals the dip pipes in the hydraulic main. But the gas
escapes from the lower onds of the dip pipes in such large volumes as to prevent
proper contact with the sealing tar, and the result is that much of the fine carbon is
carried by the gas into the coolers, lime purifiers, and gas holders; in fact any one
can notice it burning in every gas light in little sparks just above the tops of the
burners. To cause therefore a more thorough cleaning of the gas from this fine
carbon in the hydraulic main, I bore a ring of holes about three fourths of an inch
in diameter and about half an inch apart, round and through the dip pipes, about
one inch above their bottom ends. I then fill the hydraulic main with a fluid,
hereafter to be described, so that these holes in the dip pipes shall be one inch,
more or less, below the level of the fluid in the hydraulic main, and their bottom
ends be two and three quarter inches below the top surface of the sealing fluid.
The effect is that the gas generated in the retorts presses the fluid, whether it be
tar or any other proper liquid, down in the dip pipes until it comes to the ring of
three quarter inch holes bored through their sides, and then escapes in divided and
horizontal streains, shooting out in a ring of jets, presenting more gaseous surface
to the fluid, going further and remaining longer in it, and being more effectually.

page_text: stripped and washed from its fine carbonaceous impurities. I", I", I¹¹, I¹¹, show
these holes, as before described, through the sides and one inch above the bottom
ends of the dip pipes K", L", M", N".
The buckets under the dip pipes in the hydraulic main are fifteen inches in
internal diameter. They rest on the bottom of the main. Their tops are just
high enough to be on a horizontal line with the lower sides of the rings of holes
perforated through the dip pipes one inch above their bottom ends. The effect of
this arrangement is that the dip pipes extend down into the buckets one inch.
The buckets cannot therefore get out of position as they rest on the bottom of the
main, while their tops, being one and three quarter inches below the surface of the
fluid in the main, allow the gas to shoot out through the ring of holes in the dip
pipes and pass over the tops of the buckets and through the superincumbent fluid.
These buckets are indicated by K, L, M, N" By raising them until their
bottoms touch the bottoms of the dip pipes, or until the seal is deep enough, the
fluid which they carry up in them seals the holes in their sides still deeper. This
device enables ine to turn the gas generated in one of the reciprocating retorts into
the other, as will hereafter be shown. To operate these buckets, iron rods, three-
fourths of an inch in diameter, are made fast to their bottoms, and extend up
centrally through the dip pipes, and pass through the flanges and stuffing boxes on
their tops. These rods are indicated by O", 0, 0¹¹, O. To the tops of these
rods the levers P¹, Q", R¹, S", provided with fulcrums T", T", T, T¹¹, are
attached.
By elevating or lowering the long arms of the levers the buckets are raised or
lowered accordingly.
The hydraulic main is shown by U", and V" is an overflow pipe which carries
off the gas and also the liquid accumulations. The level of the fluid in the main is
flush with the bottom side of this discharge pipe. W" is a pipe for pumping any
liquid into the main; X1 shows a pipe for drawing off the contents of the main;
Y is a steam pipe through which steam from a steam boiler is delivered in a
forcible jet into the pipe V, for the purpose of making an exhauster to pump the
gas from the retorts, and to prevent the damaging effect of pressure of gas in them.
In the ordinary process of manufacturing coal gas from coal, such a large quantity
of tar and ammoniacal water are made, that the constant overflow of these products
from the discharge pipe attached to the hydraulic main carries off with it the fine
carbon mixed with the tar and thus keeps the main free from its accumulations.
This is not the case with the present process. If I commence to make gas with the
main filled with tar or some other fluid, in a few days the liquid in the main will
become so thick and viscid with the admixture of fine carbon injected into it by the
gas from the retorts, that the flow of gas through the dip pipes is obstructed, until
finally the main has to be cleaned out and re-filled. Nor can pure water be used in the
hydraulic main in place of tar, because dry and hot lampblack or minutely divided
carbon, which the gas brings abundantly out of the retorts in all gasworks, flies
through the water without being moistened by it, and penetrated, and consequently
without being entangled in it and held back by it. To provide against this con-
tingency, I therefore mix water with soap, gelatine, gum, alkali, or some similar
matters, by which an emulsion, or a gelatinous, or mucilaginous, or soapy fluid is
prepared, in which pulverized charcoal will readily mix, and pump this into the
main, as occasion requires, to keep it free from obstructions from this source and to
wash the gas from this impurity. In preparing this fluid to fill the main, the rule
to go by is this:-Take a given quantity of water and mix with it enough soap,
gelatine, glue, gum, soda, potash, or oil, or heavy petroleum, in which enough soda
or potash has been mixed to form an emulsion with water, and prepare a liquid
with which pulverized charcoal will readily mix into a wet and pasty mass.
Such
a fluid will answer well for the hydraulic main of any gasworks, and will cleanse
the gas from its lampblack in a satisfactory manner.
Having described the objects of the Invention and one form of apparatus for the
accomplishment of these objects, I-will-now show what I deem to be the est

page_text: method of operating it. It is understood that these observations now refer to a
bench of four retorts, as shown in the Drawings, and described in this Specification.
In the first place, I fill the hydraulic main with a fluid prepared as before-
described up to a level with the discharge pipe V. I then kindle a fire in the
furnace under the retorts B, C, D, and E and heat them up to a high cherry-red
heat. I then take off the doors of the retorts B and D and charge them, in the
first instance, with coke. I then shut them up and wait about an hour and a half
to let the coke in the retorts become rod hot, in order to be in a suitable condition
to decompose the tarry and aqueous vapours from the charge of gas coal with which
the reciprocating retorts C and E are to be charged.
It is understood that all the valves between the retorts and the hydraulic main
are now open. I now charge these last-mentioned rotorts with two hundred pounds
of gas coal in each; I draw out the valvo Z by the handle B¹ in the cross pipe F,
which opens a communication between the retorts B and C; I also draw out the
valve D by the handle F¹ in the cross pipe G, which opens a communication
between the retorts D and E; I also pull down the levers R, S", which raises the
buckets M, N, and seals the dip pipes M", N", which communicate with the
retorts C and E so deeply that the gas coming off from the two fresh charges put
into them passes into the cross pipes F and G, and through them into the two
retorts B and D, which are charged with retort hot coke. By passing over and
through it, the tarry and aqueous vapors, which are expelled from the coal C and E
while it is heating up to a red heat, are decomposed into fixed gas. The tar gas
and the water gas from the coal boing generated together recombine in a nascent
state, and compose an illuminating gas of rare brilliancy. The gas passes into the
stand pipes and through the saddle pipes and dip pipes K", L", which are in
communication with the retorts B and D, and escapes through holes in the said dip
pipes, whose buckets K, L, are down, and whose rings of holes therefore
have a less seal than the rings of holes in the two dip pipes M, N, whose
buckets M, N111, are up. At the same time I open the oil valves X¹, Y', in the
feed pipes T, U, which enter the cross pipes F and G over the retorts B and D ;
I also open the two valves P¹, Q1, in the pipes L, M¹; this causes oil, petroleum,
naphtha, or any other fluid gas-yielding material to descend into the two rotorts B, D,
charged with red-hot coke, and to fall on to the inclined aprons B", B", which
conduct it back into the red-hot coke, where it is vaporised and decomposed into
gas during its passage through those retorts. At the same time I open the
steam valve U and let steam from the boiler into the pipe S in the superheater Q;
I then open the steam valve W in the steam pipe M and the valve Y in the branch
steam pipe 0; this lets jets of superheated steam oscape from the nozzles or
tees I, K, in the cross pipes F and G. The superheated steam jets shooting from
these nozzles expand and make a pump in the mixing pipes F, G, and draw out the
tarry and aqueous vapours and gases from the fresh charges of coal in the
retorts C and E, and mix with them and with the streams of oil falling into the
pipes F, G, from the pipes T', U', and inject them together into the retorts B and D.
These retorts, charged with red-hot coke, are now in a suitable condition to receive
these mixed products and decompose. them, and recombine them into a fixed gas of
extraordinary illuminating power. The steam is also let into the pipe Y" to make
a pump in the overflow pipe V" and remove the pressure from the hydraulic main,
and draw the gas out of the retorts as soon as it is generated. The retorts are to
be kept up to a very high red heat, verging into an incipient white. By giving
them constant supplies of gas-yielding material a higher degree of heat may be
carried on the retorts, and gas be generated more abundantly than with a low heat.
This operation goes on steadily for two hours, more or less, or until the charges of
coal in the retorts C and E have been distilled for one-half the period of time
allotted to their distillation.
The gas is cooled, purified by lime, measured, and stored in gas holders in the
usual way. At this period I begin to prepare to draw the coke in the retorts B and D,
and to charge them with gas coal. I first shut the valves P¹, Q¹, in the oil

page_text: pipe L', M, and the valves X, Y, in the siphon feed pipes T', U¹; I then shut the
steam valves Y and W and push up the levers R and S", which lowers the
buckets M¹ and N and diminishes the seal of the dip pipes M" and N"; I then
pull down the levers P and Q, which lifts up the buckets K and L¹¹ and
increases the seal of the dip pipes K" and L"; after this I shut the valves Z and D¹;
this closes the communication between the retorts B and C and between D and E,
and prevents the gas escaping from C and E while B and D are being charged. I
now loosen the doors on the retorts B and D and set fire to the escaping gas, to
prevent a "rap" I then pull out the aprons B, B", and plunge them into the
water to cool them; I then draw the coke from these retorts and charge them with
about two hundred pounds of gas coal in each, put in the aprons B", B, and close
the doors; I then immediately open the two valves Z and D¹ and the steam
valve T, and let steam from the boiler into the pipe R in the superheater P; I then
open the two steam valves V and X in the steam pipe L and the oil valves R', S',
and Z, A". This causes streams of oil, petroleum, naphtha, or any other oleaginous
fluid which may be employed, to fall into the mixing pipes F and G, and also jets
of superheated steam to shoot from the nozzles H and J, directed towards these
streams of oil and heating them, which steam jets also expand and impinge against
the interior sides of F and G, and tend to create a vacuum in the rear of these
points of impingement, and therefore to draw by suction the tarry and aqueous
vapors and gases from the fresh charges of coal in the retorts B and D into the
mixing pipes F and G, and inject them, with the oil streams, into the retorts C and E,
to be dispersed through and over their red-hot charges of partially distilled coal,
and to be decomposed conjunctively with the steam and their elements, together
with the gas still being generated from the partially-distilled charges of coal in
these retorts recombined in their nascent state into a fixed gas of high illuminating
power, and passed through the red-hot stand pipes of these retorts into the
hydraulic main.
It is to be here observed that the course of the gas is now reversed. I wish it
also to be distinctly understood that the great novelty and utility of the Invention
are now and here completely unfolded and shown in this operation, as distinguished
from all processes of gas making hitherto known by me, and as constituting the life
of the Invention, namely, that the fixed gas thus manufactured is a combination in
one retort, at the same time and by means of the same heat, of the gaseous
elements derived from four distinct and separate sources, namely, from the tarry and
aqueous vapors and gases coming from the fresh charges of coal in the reciprocating
retorts B, D, and the superheated steam jets escaping from the nozzles H and J, and
the streams of oil, petroleum, naphtha, or any other suitable oleaginous matter
from the pipes V, W₁, and the gas generated from the partially-distilled charges of
coal in the retorts C and E.
The poor gases generated from the steam, combine in a nascent state with enough
of the excessively rich carbonaceous matter of the oil, petroleum, naphtha, or other
similar body, to make a good compound illuminating gas; while the coal tar and
ammoniacal water, now secondary and unutilized products in the ordinary coal gas
works, being decomposed together by this process so recombine as to produce a rich
and permanent gas.
So effectually do I decompose this coal tar and ammoniacal water that I do not
make one drop of either, when proper care is taken to maintain the heat of the
retorts at the proper degree. When it is considered that a ton of gas coal distilled
in the method now commonly practiced produces not generally less than twelve
gallons of coal tar, and often more than this quantity of ammoniacal water, thus
making together twenty-four gallons or more of liquid gas-yielding products, which,
when decomposed in conjunction and combined together, make a good fixed
illuminating gas, there can be no good ground left for marvel at the assertion which
I here make, that this process of distilling coal produces at least one-third more
gas from a ton of coal of superior quality than the mode in common use by coal
gas companies. I do not get tar enough to seal the dip pipes in the hydraulic main;

page_text: and to meet this deficiency, I am obliged to prepare water, as heretofore explained,
to seal them. Besides, by supplying oil and steam to the retorts in graduated and
constant streams during the latter part of the period of distillation, when the
charges of coal are red hot, and aro partially converted to coke, and in a suitable
condition to receive a reinforcement of gas-yielding material, I keep up a flow of
gas from the retorts, uniform in quantity and quality to the very end of the period
of distillation. By this means I confidently assert that I get as much gas, and as
good gas out of one retort, and by the same heat, as can be obtained from two
rotorts charged with coal alone, and distilled for the same length of time. This
fact developes another economical value of the Invention. Only about one-half the
number of retorts are required to manufacture a given quantity of gas by this
process, compared with the number needed to produce an equal amount of gas by
the process now universally in use by coal gas companies. The expenses for labor
and material are correspondingly reduced.
I have shown one form of apparatus for carrying out the Invention. Other
plans may be devised to do the same thing, and, therefore, I shall claim broadly,
independently of any apparatus, the process of making fixed gas for illuminating
and heating purposes, substantially as herein-before set forth.
I have shown how the reciprocating retorts are charged and operated. These
operations are to be continued as stated, charging each retort every four hours, and
reversing the gas, and the oil, and steam feed, into the reciprocating retort at the
same time, and charging each retort two hours apart. This process requires that
the charge of coal, wood, peat, turf, or any other gas-yielding and coke-producing
material, shall be distilled for two hours in one retort before the products of the
other retort, together with the oil and steam, are turned into it and the course of
the gas reversed. This course is to be pursued when the period of distillation of
each charge of coal, or other. similar materials, is limited to four hours. But a
longer or shorter period may be practiced, provided that the middle of the period
of distillation, or thereabouts, of one retort, shall be the time when the other
reciprocating retort shall be charged, and the course of the gas be reversed, and the
products of the fresh charge, together with the oil and steam feed, be turned into
the retort, whose charge is red hot and partially distilled.
The forcible jets of steam, shooting first in one direction and then in the opposito
direction, from the steam nozzles H, I, in F, and from J, K, in G, perform four
different functions; they keep the pipes F and G clean by preventing in them the
deposition or accumulation of tar or hard carbon; they make a pump to draw out
the tarry and aqueous vapors and gases from the retorts when freshly charged, and
inject them into the reciprocating retorts; they act as carriers and force pumps to
push and disperse the oil, vapors, and gases through these last retorts, and dis-
charge the gas finally from them; they furnish by decomposition large volumes of
gas to combine with the richer carbonaceous vapors and gases, and to increase the
production of good illuminating gas.
Having thus described the nature of the Invention and one method of carrying
the same into effect, I declare that what I claim as the Invention to be protected
by the herein-before in part recited Letters Patent is,―
I. A bench of gas retorts A, connected together in reciprocating pairs as B, C,
and D, E, by the cross pipes F and G placed on their front ends, which project out-
side of the furnace, and which pipes are provided with valves Z and D', steam
connections L, M, N, O, and nozzles H, I, and J, K, and pipes T, U, V, W', for
feeding oil into them; the said retorts having their stand pipes placed on their rear
ends and within the furnace, substantially in the manner and for the purposes
shown and described.
II. The aprons B¹¹, B¹¹, B¹, B", in combination with gas retorts, as B, C, D, E,
having pipes T, U, V, WI, for feeding oil into them, substantially in the manner
and for the purpose set forth.
III. The nozzles H, I, and J, K, in combination with the pipes F and G, and the

page_text: retorts B, C, and D; E, substantially in the manner and for the purposes indicated
'and described.
IV. The arrangement of gas retorts in a furnace, with jets of steam discharging
into them alternately and in opposite directions, as vehicles to carry the products
of a freshly charged retort into a reciprocating one whose charge is red hot, and
partially or wholly distilled, and in which they shall be decomposed into fixed
gas.
V. The steam pipes L, M, in combination with the superheaters P and Q, and
with the nozzles H, 1, in the pipe F, and tho branch, steam pipes N, O, in com-
bination with the nozzles J, K, in the pipe G, all provided with valves V, W, X, Y,
substantially in the manner and for the purposes described.
VI. The superheated steam pipes P and Q arranged in the lower flues of a bench
of retorts B, C, D, and E, which lead the gases of the furnace to the stack under-
neath the lower retorts D and E, for the purpose of superheating steam during its
passage through them from the boiler to the retorts through the pipes L and M by
means of the spent heat of the furnace, substantially in the manner and for the
purpose set forth.
VII. The steam pipes R and S, with valves T and U, in combination with the
superheaters P and Q, substantially as set forth.
VIII. The oil reservoir H', provided with the pipe I' for filling it, the float J¹
for indicating the quantity of oil in it, the safety pipe K' and the attached feed
pipes L, M, N, O¹, and valves P¹, Q, R, S, arranged substantially in the manner
and for the purposes indicated.
IX. The siphon feed pipes T, U, V, W, provided with funnels B, C,
D, E, and valves X, Y, Z, A¹¹, in combination with the cross pipes F and G,
and retorts B, C, D, E, for supplying them with oil or other oleaginous matter,
substantially in the nanner and for the purpose set forth.
X. The stand pipes C, C, C¹¹, C", in combination with the rear ends of the
retorts B, C, D, and E, for the purpose of causing the gas generated in them, and
impregnated with any tarry vapors, to escape through red-hot exit pipes and to
effect a more perfect decomposition of the tarry vapors, instead of allowing it to
escape as is now done from their front ends, which are outside of the furnaco and
are never hot, and to carry off with it a large amount of tar and ammoniacal water
as secondary products, and lessen the quantity of gas, substantially as described.
XI. The dip pipes K, L, M, N", having a series of holes I, I, I, I", about
three-fourths of an inch in diameter and half an inch apart, drilled or cast in their
sides about one inch above their lower and open ends, for the purpose of causing
the gas to escape from them in small and divided streams, and shoot horizontally
in a ring of jets into the fluid which seals their lower ends, and to be more perfectly
washed from the fine carbon with which it is so abundantly charged, substantially
as shown and described.
XII. The dip pipes K", L", M", N", with discharge holes I", 1", 1", 1", in com-
bination with the hydraulic main U", having an overflow pipe V, whose lowest
interior side is higher than the said holes in the dip pipes, so that they shall be
constantly sealed by the fluid which fills the main U", and overflows through the
pipe V, in order that the gas coming from the retorts may force the fluid in the
dip pipes down to the holes 11, I", 1", 1", and escape through them in a ring of
horizontal jets into the outside fluid and be more thoroughly washed, substantially
in the manner and for the purposes herein set forth.
XIII. The buckets K, L, M, N, resting on the bottom of the hydraulic
main U under the dip pipes K, L, M, N, and provided with attached rods
01, 0, 0, 0, which pass up centrally through said pipes and through the
flanges on their tops, and connected with the levers P, Q, R, S", and the
fulcrums T, T, T₁₁, T", so as to raise and lower the said buckets at pleasure, in
combination with the said dip pipes, in such manner that when the said buckets
rest on the bottom of the main their tops shall be flush with the lower sides of

page_text: the holes I, I, I", I", I", and allow the gas to shoot over them and into the
superincumbent fluid which surrounds them externally; and when the long arms of
the levers are pulled down that the buckets shall be so far elevated as to submergo
the said holes in the dip pipes deeply in the fluid which they contain as to reverse
the course of the gas and turn it into the reciprocating retort, and cause it to
enter the hydraulic main through the holes of its dip pipe which are less deeply
sealed, substantially as described.
XIV. The hydraulic main Ull and the dip pipes K", L", M", N", in combination
with a sealing fluid prepared, substantially in the manner and for the purpose
herein-before explained.
XV. The tubular cutters D", D", D", D", provided with external teeth or spiral
cutting edges G" and attached rods E", E", E", E", having lugs on them FF",
F, F, to hold them up in the tops of the stand pipes when not in use, by resting
on the tops of their flanges through which they are passed by means of oblong
holes, in combination with the stand pipes C, C, C, C", substantially in the
manner and for the purpose set forth.
XVI. The combination of the steam pipes J", J", J, J", with the saddle pipes
H, H, H, H, for the purpose of injecting into them jets of steam to clean them,
substantially as shown and described.
XVII. A process of manufacturing illuminating gas, which consists in passing
the tarry and aqueous vapors and gases dsstilled from a fresh charge of coal, wood,
peat, turf, or other similar materials undergoing destructive distillation in one
retort, in conjunction with oil, petroleum, naphtha, or any suitable oleaginous
matter, together with steam (preferably superheated) as an injecting, carrying, and
gas-yielding agent into a reciprocating retort charged with red-hot coke, or partially
distilled coal, wood, peat, turf, or other suitable substance to be decomposed
conjunctively in the same into fixed gas, and continuing this operation until the
said fresh charge is partially distilled, and then shutting off the oil and steam feed
and drawing the spent charge from this rotort and charging it with a fresh charge
of coal, wood, peat, turf, or other similar material, and reversing the course of gas,
and turning it from the retort last charged, with its tarry and aqueous vapors and
gases, in conjunction with a stream of oil, petroleum, naphtha, or any other
oleaginous matter, together with steam, as an injecting, carrying, and gas-yielding
agent into the other reciprocating retort, whose charge is now red hot and partially
distilled, to be decomposed together in the same into fixed gas, and continuing this
operation until the last fresh charge is partially distilled, and then shutting off the
oil and steam feed, and drawing and charging this last retort again, and reversing
the gas as before, and turning its tarry and aqueous vapors and gases with the
oil and steam feed into the other retort, and so continuing this alternating process,
thus generating, mixing, and combining the gaseous elements of coal or any similar
material, petroleum, or any fluid carbonaceous matter, and water, or steam in the
same retort, in a nascent state, and during the usual period of distillation, into a
fixed gas of superior illuminating power with novel rapidity and economy.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set my
hand and seal, this Twenty-second day of November, in the year of our
Lord One thousand eight hundred and seventy-eight.