there in Part Applicable for the Preparation of Caustic Ammonia Solutions.
Year: 1885

page_text: therefor, the same being in Part Applicable for the Preparation
of Caustic Ammonia Solutions.
I, WILLIAM YOUNG of Priorsford in the Town and County of Peebles, North
Britain, Chemical Engineer, do hereby declare the nature of this invention for
IMPROVEMENTS IN THE PURIFICATION OF COAL GAS AND IN APPARATUS THEREFOR
THE SAME BEING IN PART APPLICABLE FOR THE PREPARATION OF CAUSTIC AMMONIA
SOLUTIONS, to be as follows:-
This Invention relates to the purification of coal gas from carbonic acid and
sulphuretted bydrogen and other impurities by means of ammonia and it consists
of simple and improved arrangements whereby the ordinary ammoniacal liquors
produced during the carbonization of coals can be made more perfectly and
economically available for that purpose. It is also applicable in part for the
preparation of caustic ammonia.
It is well known that when crude ammoniacal liquor such as that produced in
the carbonization of coal for the production of illuminating gas and which contains
in solution carbonate and sulphides of ammonia, is heated up to temperatures
somewhat under the boiling point of water, a considerable part of the carbonic
acid and sulphuretted hydrogen is liberated in the elementary or gaseous state, and
the ammonia is left in solution in the water in the free or caustic state and that
when this caustic ammonia is cooled and brought in contact with the crude gas, it
combines with and removes an equivalent of carbonic acid and sulphuretted
bydrogen gases cyanogen and other impurities.
Processes embodying the above principle have already been in use for the purifi-
cation of coal gas such as are described in the specification of Hills No. 1369
A.D. 1868 and 510 A.D. 1870 in the Specification of myself, the said William
Young, No. 1587 A.D. 1881 and in the specifications of Claus No. 2838 A.D. 1881
and No. 4644 A.D. 1882.
By all of these processes however the dissociation of this carbonic acid and
sulphuretted hydrogen from the ammonia is effected at, or very little over atmo-
spheric pressure, and consequently between the temperatures of the dissociation of

page_text: the carbonates and sulphides of ammonia and the boiling point of water, (212°
Fht.) and as the solvent power of water for ammonia at those temperatures under
ordinary atmospheric pressure is small and the available range of temperature
limited, the processes had to be conducted slowly in large vessels and only weak
solutions of carbonate and sulphides of ammonia could be thus rendered caustic and
suitable for purifying the coal gas. When these weak liquors were concentrated
by distillation and condensation and the solution of ammonia in water so obtained
was used to remove the acid gases from the coal gas, it was made to flow through
scrubbers against the current of coal gas.-When thus used, the caustic ammonia
solution on coming into contact with the comparatively pure gas leaving the
scrubber, parts with much of its ammonia which entailed washing out with large
quantities of water, and by the time the strong solution reached the end of the
scrubber and was saturated with acid gases it became comparatively weak.
According to my invention the process of dissociating the carbonate and sulphides
of ammonia in the ammoniacal liquor is effected whilst under considerable pressure
in excess of the atmosphere.
The excess of pressure has the effect of increasing the quantity of caustic or free
ammonia that can be held in solution by the water whilst not materially increasing
the solubility of the carbonic acid and sulphuretted hydrogen gases in the water,
or yet effecting the dissociating of the carbonate and sulphides of ammonia and
therefore enables higher temperature and stronger solution of the carbonate and
sulphides of ammonia being employed without losing ammonia gas.
The pressure in excess of the atmosphere required depends upon the strength of
the solution of ammonia salts to be dissociated, and upon the rate at which the
operation has to be conducted. The stronger the solution of ammonia salts and
the more rapid the process of dissociation has to be conducted in a given size of
apparatus, the higher must be the pressure employed, from 30 to 50 lbs. per square
inch in excess of the atmosphere is sufficient under ordinary circumstances.
The apparatus employed in the process for the dissociating of the solutions of the
carbonate and sulphides of ammonia, may be of any of the well known forms such
as those described in the Specifications herein before referred to. They must
however be made strong to resist the extra pressure, and be provided with pumps
to force the solution into them and have safety regulating valves on the pipes for
the outflow of the dissociating gases and for the caustic ammonia liquors.
I prefer however to modify these processes, so that the interchange of beat
between the inflowing solution of ammonia salts and the outflowing caustic
ammonia solution will take place after the inflowing solution has been used to
absorb the ammonia accompanying the escaping acid gases. This I accomplish by
inserting a heat interchange coil or its equivalent in the decomposing column or
still, or by drawing off the liquors from the side of the decomposing column into a
separate heat interchanging arrangement and returning the hot liquor back into
the next division in the decomposing column or still.
The preparation of solution of caustic ammonia herein before described may be
applied for the purification of the coal gas or for the preparation of the caustic
ammonia either in the state of solution or in the gaseous state and in the manner
described in the Specifications already hereinbefore referred to. When however the
caustic ammonia is applied to the gas just before entering the scrubbing or washing
stage, I prefer to reverse the method hitherto in use, that is to say instead of
making the ammoniacal solution flow or fall against the current of coal gas, I make
the coal gas and solution of ammonia flow or travel together. This method may
be carried out in the ordinary scrubber or washer in use, in the case of vertical
scrubbers by making the gas pass downwards instead of upwards, and with
horizontal scrubbers by reversing the flow of the solution of ammonia, that is, make
it enter when the coal gas enters and be drawn off at the opposite end when the
coal gas leaves. When thus applied the strong ammoniacal solution or ammonia
gas is at once brought into contact with the crude gas and carbonate and sulphides

page_text: of ammonia are at once formed. The solution of those salts is not so volatile as
the ammonia in the caustic or free state and any free ammonia in excess of that
necessary to combine with the acid gases then present, are held in solution by the
solution of the carbonate and sulphides of ammonia till overtaken by gas con-
taining acid gases when combination ensues and the solutions of ammonia are thus
kept in a concentrated state.
Any free ammonia which may be carried away in diffusion in the coal gas is
absorbed in scrubbing with water in the ordinary well known manner.
J. H. JOHNSON, DAY & JOHNSON,
Petitioner's Agents,
115, St. Vincent Street, Glasgow.

page_text: Improvements in the Purification of Coal Gas, and in Apparatus
therefor, the same being in Part Applicable for the Preparation
of Caustic Ammonia Solutions.
I, WILLIAM YOUNG of Priorsford, in the Town and County of Peebles, North
Britain, Chemical Engineer do hereby declare the nature of my invention for
IMPROVEMENTS IN THE PURIFICATION OF COAL GAS, AND IN APPARATUS THEREFOR,
THE SAME BEING IN PART APPLICABLE FOR THE PREPARATION OF CAUSTIC AMMONIA
SOLUTIONS and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
My Invention relates to the purification or separation from coal gas, of carbonic
acid, sulphuretted hydrogen and other impurities, by means of ammonia.
My Invention consists of improved arrangements of working whereby the
ordinary ammoniacal liquors produced during the carbonization of coals can be
made more perfectly and economically available for that purpose.
My Invention is also applicable in part for the preparation of caustic ammonia..
It is well-known that when crude ammoniacal liquor such as that produced in the
carbonization of coal for the production of illuminating gas (and which contains in
solution carbonate and sulphides of ammonia) is heated to temperatures somewhat
under the boiling point of water, a considerable part of the carbonic acid and sul-
phuretted hydrogen is liberated in the gaseous state, and the ammonia is left in
solution in the water in the free or caustic state. It is also well known that when
this caustic ammonia is cooled and brought into contact with crude coal gas, it com-
bines with and removes an equivalent of carbonic acid and sulphuretted hydrogen
gases, cyanogen, and other impurities.
Processes embodying the above principle have already been used for the purifica-
tion of coal gas such as are described in the Specifications of Hill No. 1369 A.D.
1868 and No. 510 A.D. 1870; in the Specification of myself, the said William
Young No. 1587 A.D. 1881; also in the Specifications of Claus No. 2838 A.D. 1881
and No. 4644 A.D. 1882.
By all of these processes, however, the dissociation of the carbonic acid and sul-
phuretted hydrogen from crude ammoniacal liquors is effected at, or very little over
atmospheric pressure, and consequently between the temperatures at which dissocia-
tion of the carbonates and sulphides of ammonia commence and the boiling point
of water, (212° Fahrenheit); and as the solvent power of water for ammonia at
those temperatures under ordinary atmospheric pressure is small and the available
range of temperature limited, the aforesaid processes have had to be conducted
slowly, in large vessels, and thus only weak solutions of carbonate and sulphides of
ammonia could be by these processes rendered caustic and suitable for purifying the
coal gas.
When these weak liquors have been concentrated by distillation and condensa-
tion and the solution of ammonia in water so obtained has been used to remove the
acid gases from the coal gas, the solution has been made to flow through scrubbers
against the current or direction of flow of the coal gas and when thus used, the

page_text: caustic ammonia solution on coming into contact with the comparatively pure gas
leaving the scrubber, parted with much of its ammonia, thus entailing washing the
ammonia out from the gas with large quantities of water, so that by the time the
solution reached the end of the scrubber and was saturated with acid gases it
became comparatively weak in ammonia.
Now according to my Invention the process of dissociating the carbonate and
sulphide of ammonia in the ammoniacal liquor is effected whilst under considerable
pressure in excess of the atmosphere.
The excess of pressure has the effect of increasing the quantity of caustic or free
ammonia that can be held in solution by the water, whilst not materially increasing
the solubility of the carbonic acid and sulphuretted hydrogen gases in the water, or
yet materially interfering with or modifying the dissociating of the carbonate and
sulphides of ammonia. This higher pressure therefore enables higher temperatures
and stronger solutions of the carbonate and sulphides of ammonia being employed
without losing ammonia gases.
The pressure in excess of the atmosphere required, depends upon the strength of
the solution of ammonia salts to be dissociated and upon the rate at which the
operation has to be conducted. The stronger the solution of ammonia salts and the
more rapidly the process of dissociation has to be conducted in a given size of
apparatus, the higher must be the pressure employed. From about 30 to 50 lbs.
pressure per square inch in excess of the atmosphere is sufficient under ordinary
circumstances.
The apparatus employed in the process for the dissociating of the solutions of
the carbonate and sulphides of ammonia, may be of any of the well known forms,
such for example as those described in the Specifications herein before referred to,
other forms of washers or scrubbers such as are used in gas works may be
employed. They must, however, be made strong to resist the additional pressure,
and be provided with pumps to force the solution into and through them, also with
safety and regulating valves on the pipes for the outflow of the dissociated gases
and for the caustic ammonia liquors. I prefer, however, to so arrange the apparatus
that interchange of heat between the inflowing solution of ammonia salts, and the
outflowing caustic ammonia solution, will take place after the inflowing solution
has been used to absorb the ammonia accompanying the escaping acid gases.
This I accomplish by inserting a heat interchange or regenerating coil or its
equivalent in the decomposing column or still, or by drawing off the liquors from
the side of the decomposing column into a separate heat interchanging or regen-
erating arrangement, and returning the hot liquor back into the next division in
the decomposing column or still.
The preparation of solution of caustic ammonia herein before described may be
applied to the production of concentrated caustic ammonia solution, by distillation
in any of the well known methods or it may be applied for the purification of the
coal gas either in the state of solution or in the gaseous state and in the manner
described in the Specifications already hereinbefore referred to. When, however,
the caustic ammonia is applied to the gas just before entering the scrubbing or
washing stage, I prefer to reverse the method hitherto in use, that is to say, instead
of making the ammoniacal solution flow or fall against the current of coal gas,
I make the coal gas and solution of ammonia to flow or travel together, or in the
same direction. This method may be carried out in the ordinary vertical or hori-
zontal scrubbers or washers in common use; in the case of vertical scrubbers by
causing the gas to pass downwards instead of upwards, and in the case of hori-
zontal scrubbers by reversing the flow of the solution of ammonia, that is, by
causing it to enter the scrubber where the coal gas enters and to be drawn off at the
opposite end of the scrubber where the coal gas leaves it. When thus applied the
strong ammoniacal solution or ammonia gas is at once brought into contact with
the crude gas, and carbonate and sulphides of ammonia are at once formed. The
solution of those salts is not so volatile as the ammonia in the caustic or free state
and any free ammonia in excess of that necessary to combine with the acid gases
:

page_text: then present, is held in solution by the solution of the carbonate and sulphides of
ammonia until overtaken by gas containing acid gases, when combination ensues
and the solutions of ammonia are thus kept in a concentrated state.
Any free ammonia which may be carried away in diffusion in the coal gas is
absorbed in scrubbing with water in the ordinary well known manner.
In order that my Invention may be properly understood and readily carried into
effect, I will now proceed to describe the drawings hereunto annexed.
Figures 1 and 2 (sheet 1) of the accompanying drawings are respectively a side
elevation and a plan, shewing the general arrangement of apparatus I find suitable
for carrying my said Invention into practice.
The vessel A, is that wherein the dissociation of the ammoniacal solutions of
carbonate and sulphide of ammonia takes place. In the vessel or still B, the
concentration of the solution of caustic ammonia is effected.
In the washer or purifier C, the caustic ammonia solution is brought into contact
with the crude coal gas, and in the scrubber washer D, the removal of any traces
of ammonia, which may accompany the gas leaving the washer or purifier C, is
effected.
The details of the interior construction of apparatus, such as I use for working
my Invention, are shewn in the enlarged drawings on sheets 2, 3, 4 and 5. Figure 1
(sheet 2) is a vertical section of the dissociating vessel A, shewing the concentrating
still B, in elevation.
The dissociating vessel A, is by preference built together of steel plates. The
lower part of this vessel is jacketed so as to enable the ammoniacal liquors
contained therein to be heated by steain admitted into the jacketed space by the
pipe a. The lower and upper parts of the dissociating vessel A, are provided with
shelves m, m2, m, which are perforated such perforations having a short nozzle m',
projecting upwards as shewn, and covering each such nozzle is a small inverted
cup m². The middle portion of the dissociating vessel A, is provided with other
shelves m', to m₁, having circular and annular openings e, and f, respectively, in
and around the said shelves, that is to say, alternately at the centre and around the
serial shelves, as shewn at Figure 1 (sheet 2) and in these shelves are placed the
coils of pipes p. The construction of these shelves and the arrangement of their
fittings are shewn more clearly in the separate and enlarged Figures 2, 3, 4, 5
and 6 respectively (sheet 2) of the annexed drawings.
Figures 1 and 2 (sheet 3) and the Figure on sheet 4 of the annexed drawings are
respectively a side elevation, partly in longitudinal section; a plan partly in hori-
zontal section; and an end elevation partly in transverse section, of a washer or
purifier of a construction which I find convenient to use in the practical working of
my Invention.
This part of the apparatus consists of a large rectangular chamber built up of
cast iron plates in sections and bolted together so as to form a series of horizontal
troughs h, situated within the chamber and one above another as shewn. Each
trough h, contains the purifying solution of ammonia, and the troughs communicate
with each other by the flat tubular openings i. Each tube i, is serrated and per-
forated at the bottom as shewn at Figures 1 and 3 (sheets 3 and 4) respectively,
for the purpose of causing the gas as it descends through the washer to be broken
up into small divisions or streams in passing through the layers of ammonia
solution in the successive troughs h. The base of the washer constitutes a cistern
to receive the solutions of caustic ammonia after it has become charged with
sulphuretted hydrogen, carbonic acid, and other impurities which it has separated
from the crude coal gas, as the latter descends through the caustic ammonia
solutions in the washer.
The upper part of the washer constitutes a water tank wherein is placed a coil
of pipes for cooling the causticised solution of ammonia when on its way from the
dissociating vessel A, and still B, to the washer C.
Figures 1, 2 and 3 (sheet 5) of the annexed drawings are respectively side and
end elevations, and a plan, all partly in section for the purpose of shewing the

page_text: interior structure of the scrubber. This is also built up of cast iron plates bolted
together so as to constitute a series of superimposed horizontal troughs, the bottoms
of which are perforated, each perforation being formed into a vertical nozzle and
covered by a light sheet iron cap or cover, whose edge, which is or inay be serrated
or perforated, dips into the liquid in the troughs, and each of which are kept in
their proper position over each nozzle by means of a central wire passing down
through the hole in the nozzle as shewn, and as is well understood. The base of
the scrubber constitutes a tank for receiving the solutions of ammonia formed
therein.
Having now pointed out the construction and arrangement of the apparatus
shewn on the annexed drawings, I proceed to explain how I combine them
together as shewn in the elevations and plans Figures 1 and 2 on sheet 1 of the
drawings for the purpose of practising my Invention.
A suppy of ammoniacal liquor such as that obtained by condensation in the
ordinary manner from coal gas, and rendered as free as possible from tar, is
contained in any suitable receptacle, not shewn in the drawings. From such
source the liquor is drawn through the pipe j, and forced through the vertical
pipe k, by the pump 1, into the top of the dissociating vessel A. The liquor as it
passes to the interior of the dissociating vessel A, falls upon the dash plate n, by
which it is spread over the first shelf m, fitted with nozzles m', and light caps m³.
The level of the liquor rises in the first shelf m, until it reaches the height of the
overflow pipe m³, when it trickles down this pipe m³, to the next shelf m*,
escaping through serrations and perforations formed in the bottom of the pipe m³,
as shewn. The liquor then collects on the next shelf m, until its level rises to the
top of the overflow pipe m³, through which it again passes downwards to the third
shelf me, into which it flows, again through serrated openings and perforations in
the bottom of the overflow pipe m³, and in this manner the liquor passes by
successive stages to the lowest of the shelves mo, in the upper part of the dis-
sociating vessel. It is here explained that at about the central part of the height
of the dissociating vessel, the structure thereof is for reasons hereinafter explained
altered into a series of circular troughs respectively marked m³, m³, m³, m10, m",
and m". In the upper of these troughs m7, the descending ammoniacal liquor
collects until it overflows round the lip forming the side thereof, and falling from
which it is caught in the next circular trough m³, until it reaches the height of the
lip surrounding the central opening thereof, when it again overflows through the
said central opening and collects in the next trough m³, and so on the liquid thus
flowing from centre to side and from side to centre of the series of troughs m²,
to m, when falling from which it is caught in the uppermost trough marked m¹³,
Figure 1 (sheet 2) of construction like to those contained in the upper part of the
dissociating vessel, and in passing through the lower series of such troughs it
reaches the lower chamber q, which is surrounded by the jacketed space r, into
which steam is admitted by the pipe a. This steam soon heats the ammoniacal
solution to the point at which dissociation of the carbonic acid, sulphuretted
hydrogen, and ammonia takes place. The ammonia for the most part remains in
solution in the liquor collecting in the bottom chamber q, whilst the sulphuretted
hydrogen and carbonic acid gases pass off upwards from the liquor accompanied
by only a small portion of ammonia, but which is washed out from the ascending
gases as they pass up through the nozzles and under the lips of the cups which
cover the nozzles on each of the troughs or shelves. In this way escaping upwards
and being washed by the ammoniacal liquors descending through the dissociating
vessel, the ammonia contained in the ascending gases, is continuously washed out
of them and carried down again to the lower chamber q. As the outlet pipes for
the passing off of the acid gases is provided with a regulating valve t, Figure 1,
which is loaded, these gases can only escape when they have acquired a tension
corresponding to the pressure at which the regulating or escape valve t, is loaded
to work. The pressure in the dissociating vessel A, increases until that point of
tension is reached. For the purpose of preventing injury to the apparatus by the

page_text: accidental increase of pressure in the dissociating vessel, through the regulating
valve becoming stuck or from other causes such as a choking of the pipe leading to
the regulating valve t, the vessel is provided with a safety valve 8, which is loaded
to a higher pressure than that of the regulating valve, say for example 10 lbs.
pressure per square inch above the pressure per square inch on the regulating
valve t. Thus, should the regulating valve cease to open or the pipe become
choked then the safety valve s, would open and allow the acid gases to escape
before the pressure in the dissociating vessel could accumulate to a dangerous
point.
So soon as the solution of ammonia has accumulated in the lower part of the
dissociating vessel that it appears in the glass tube of the water-gauge u, the
pump L, is stopped and the heating continued until a sample of the liquor drawn
off through a cock of the water-gauge shows that the ammonia has become rendered
caustic or nearly so. The pump l, is then again started, which by forcing a further
supply of ammoniacal liquor through the pipe k, into the upper part of the
dissociating vessel A, soon raises the liquor in the lower chamber to a level that it
is caused to flow over by the pipe ¹, into the trap arrangement V, which is of
a well-known construction and whose interior is shewn by the diagram Figure 6ª
on sheet 2. The action of this trap is as follows. When the liquor flows into the
trap V, it collects both in the external vessel v³, as well as in the internal vessel v²,
which internal vessel being provided with a closed bottom, the internal vessel v²,
remains sunk in the liquor resting against the bottom of the external vessel, so
long as liquid continues to flow over from the dissociating vessel A. If at any
time, however, liquid should cease to come over by the level of the liquor in the
dissociating vessel falling below the pipe k', steam then would flow into the trap
by the pipe, the first effect of which would be to force the liquor in the internal
vessel, up into the pipe w, whilst at the same time that the vessel v², is being
thus emptied, it gradually rises or floats in the liquor contained in the external
vessel, until the valve v', in its bottom closes the orifice of the ascending pipe w.
So long as the valve v, is open the causticised ammoniacal liquor flows off by the
pipe w, whilst the steam is prevented from escaping. The hot caustic ammoniacal
liquor passing away from the dissociating vessel A, by the pipe w, is caused to flow
in two directions. One part of it (on the cock 3, being opened) flows upwards
through the coils of tubes p, carried in the shelves m¹ to m7, wherein it gives up
its heat to the liquor descending through the dissociating vessel A. Thus whilst
heating the descending liquor the caustic ammoniacal liquor becomes cooled in its
ascent through the several coils of pipe p, on the several shelves m¹ to m7. On
passing out from the uppermost of these coils the liquor escapes by the pipe x, to
the cooling coil ¹, placed on the top of the washer C, where being completely
cooled it enters the washer by the pipe y, (Figure 1, sheet 3). The other part of
the hot caustic ammoniacal liquor passes by the pipe, into the top of the
ammonia still B, wherein it descends over a series of shelves similar to those
herein before described and shewn as contained within the upper and lower parts of
the dissociating vessel A. As the ammoniacal liquor descends through the still B,
it meets the steam ascending therein from the steam pipe i¹, leading from the main
steam pipe Y, connected to the steam boiler Z. This steam liberates the ammonia
in the gaseous state which passes away together with a small quantity of steam by
the pipe 1 into the cooling coil ¹, on the top of the washer wherein the gaseous
ammonia is condensed and commingles with the other coil, caustic ammonia
solution flowing therefrom into the washer.
The relative quantities of caustic ammonia solutions passed direct through the
cooling coils into the washer C, and distilled by passing through the still B, must
be regulated to the strength of the solution of ammonia with which it is desired to
work. The more solution distilled the stronger will be the liquor discharged into
the washer C. The relative quantities are regulated by the valves and cocks 2
and 3 and the strength of the solution is ascertained by drawing off a portion from
the washer C, by the test cock 4.

page_text: The spent ammoniacal water in the still passes therefrom through the trap 5,
and coils 6 to the pump 7 (all shewn at Figure 2, sheet 1 of the annexed drawings)
and which pump passes it through the pipe 8 into the upper part of the scrubber D.
When by the process now described any number, say half of the troughs h, into
the washer C, are charged with caustic ammoniacal solution and the perforated
shelves 9, in this scrubber D, are charged with spent ammoniacal water the crude
coal gas to be purified is then passed through the pipe 10, into the upper chamber
of the washer and down through the tubes i, into and through the solution of
caustic ammonia in the first trough and thence by the serrated edges and
perforations at the bottom thereof into and through the liquor contained in the
next trough h, on escaping from which it passes through the next series of tubes i,
and escapes through the serrations and perforations in the lower part of these
tubes into and through the caustic ammoniacal liquor in the next trough and so on
until it reaches the bottom part or compartment of the washer C.
The carbonic acid, sulphuretted hydrogen and other impurities being removed
by the caustic ammoniacal solutions, the gas itself passes away by the pipe 11, to
the scrubber D, ascending up through the perforated nozzles in the several layers
or shelves therein in its ascent lifting the caps which cover the nozzles and
bubbling through the spent ammoniacal liquor on the shelves, which removes any
traces of ammonia which may be diffused through the gas. The purified gas
passes away by the pipe 12.
So soon as the washer C, and tank underneath it are charged with ammoniacal
solution of the desired strength and the scrubber D, contains a supply of spent
ammoniacal water, the supply from the condenser on the top of the washer C, may
be stopped by shutting the valve 13, which being done the concentrated solution
of ammonia in the tank 22 beneath the washer is brought into circulation through
the apparatus by opening the valve 14, on the pipe 15, when the pump l, is again
set in motion from the engine 16, which actuates the driving pulley 16*, a crank
pin on the shaft carrying which is connected to the pump 1, by a connecting rod.
The
In order to prevent the loss of ammonia when using such strong solutions
thereof it is necessary that the pressure in the dissociating vessel A, be increased
by adjusting the weights on the regulating valve t, and on the safety valve s.
increased tension of the carbonic acid and sulphuretted hydrogen thus produced'
may be caused to do useful work by actuating the engine 16, which drives the
pumps, and 7. To enable the engine 16, to be driven by the carbonic acid and
sulphuretted hydrogen gases, the steam admission valve 17, is closed and the gas
admission valve 19, is opened thus admitting the gases into the valve chest of the
engine, at the same time closing the steam exhaust valve 18, and opening the
exhaust valve 20. The acid gases from the exhaust valve 20, and those passing off
from the dissociating vessel by the pipe 50, meet and commingle in the pipe 21.
Any traces of ammonia which may accompany these gases in the pipe 21, can be
arrested by washing them with water or solution of sulphuric acid, and the
sulphur recovered from the sulphuretted hydrogen by any of the well-known
methods.
The process as conducted by the strong solutions of ammonia obtained in the
nanner herein before described is as follows:-
The strong solution of carbonate and sulphide of ammonia is drawn from the
tank 22 through the pipe 15, by the pump 1, and forced thence through the pipe k,
into the top of the dissociating vessel A, descending therethrough in the manner
herein before described. Whilst descending, this strong solution meets the ascending
current of acid gases which has been disengaged by heat from the strong solution
in the lower part of the dissociating vessel and absorbs from these gases any
ammonia which may accompany them, the solution in the middle part of its descent
through the dissociating vessel passes as aforesaid over the coils of pipes p, on the
shelves m7, to m¹, where it becomes heated by the out and up-flowing caustic
ammonia solutions in the coils of pipe p. The solution next descends through the
lower series of perforated shelves in the dissociating vessel A, where being further

page_text: heated by, steam from the lower chamber the hot disengaged gases undergo
dissociation, the acid gases in great part escaping. The liquor is then still further
heated and the dissociation rendered more complete in the lower chamber q, of the
dissociating vessel. The solution is then forced out by the pressure of the dis-
engaged acid gases through the trap V, thence by the pipe w, through the coils p,
whence it passes by the pipe x, through the condensing coil ³, on the top of the
washer C, and then enters the washer by the pipe y, when it comes into contact
with the crude gas entering by the pipe 10. The solution of caustic ammonia is
caused to flow from the pipe y, through which it enters along the top shelf or
trough h, until it reaches the overflow pipe i, which is the last of the series of
pipes i, in the upper shelf or trough and which being of a less height than any of
the other pipes i, the whole of the liquor is thus caused to flow from end to end
of the upper trough and on reaching the second trough h, flows back in the
opposite direction to the overflow pipe 2, at the opposite end of the second
trough h. In this way the liquor in descending the washer is caused to flow longi-
tudinally from one end of a trough to the opposite end alternately in opposite
directions as it descends from one trough to another. In this manner the solution
is caused to remain as long as possible in contact with the gas as the gas descends
through the pipes i, in one trough and escapes through the serrations and per-
forations at the lower end of each pipe i, dipping into the caustic ammonia solution
. in the trough below each such pipe.
The solution of caustic ammonia becomes saturated as it descends and as the
saturated solution of salts of ammonia is less volatile than the caustic solution
thereof it follows that not only is the solution not volatilized itself but acts as a
solvent for any ammoniacal gas that may be volatilized in the upper part of
the washer.
The saturated or nearly saturated solution of salts pass from the lower trough of
the washer C, into the tank 22, through the pipe 40, Figure 1, (sheet 3) ready to be
again pumped out therefrom through the pipe 15 as hereinbefore described.
The gas leaving the washer by the pipe 11, contains small quantities or traces of
ammonia. These are removed by the spent ammoniacal liquor in the scrubber D,
and the gas passes away purified from the scrubber by the pipe 12. When the
strength of solution of ammonia in the washer diminishes by reason of part of the
ammonia being carried forward by the gas into the scrubber D, its strength is
brought up to the desired point by either taking back part of the solution of spent
ammoniacal liquor from the cistern 23, under the scrubber D, into circulation
through the apparatus and concentrating it by means of the still B, as herein before
described, but as the liquor in the tank 23 contains fixed salts of ammonia it is
preferred that a fresh supply of liquor be again pumped from a source of ammo-
niacal liquor through the pipe j, the cock or valve 13, for that purpose being opened
and the fresh supply of liquor passed through the dissociating vessel and ammonia
still into the cooler or condenser on the top of the washer C. When this is done
the spent ammoniacal liquor solution contained in the tank 23, beneath the scrubber
is not again utilized in the apparatus but may be disposed of for the manufacture
of sulphate of ammonia or for other suitable purpose.
The sides of the washer C, as well as of the scrubber D, are provided with man-
hole doors 51, for enabling access to be had to the different shelves or troughs of
the washer or scrubber by removing any of such manhole doors.
The relative quantity of caustic ammonia solution to the quantity of gas to be
purified is regulated by the rate at which the pump 7, is driven and the quantity
of steam necessary to effect the dissociation of the solution is regulated by the
valve 24.
It is to be understood that my Invention may be worked by or with a great
variety of apparatus which in its several parts may be of different construction to
the parts herein before described so long as they are so combined together that the
functions of the several parts are maintained. For example in place of constructing.
the dissociating vessel with the three parts or sections thereof forming one con-
-

page_text: tinuous tower the three parts or sections thereof may each be made a separate
vessel and connected together by pipes to allow the flow of liquid and gases
through them in opposite directions as hereinbefore described, but this arrange-
ment is not so convenient as having them placed one above the other in a
continuous tower as I have shewn and set forth.
In place of the regulating valve t, or as an adjunct thereto a series of tall water-
luted vertical pipes may be employed for the escape and washing during their
escape of the carbonic acid, sulphuretted hydrogen and other impurities, these
succession or series of waterlutes being sufficient (when a valve t, is not used) for
regulating the working pressure in the dissociating vessel A.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what
I claim is
First. The system or process of effecting the dissociation of solutions of
carbonates and sulphides of ammonia (such as those produced in gas works) by
subjecting the said solutions to pressure whilst under the influence of heat so that
the resulting caustic ammonia may be used for the purification or separation from
coal gas of carbonic acid and sulphuretted bydrogen, as well as for the manu-
facture of concentrated solution of caustic ammonia substantially as herein before
described.
Second. Utilizing ammoniacal liquor containing in solution carbonates and
sulphides of ammonia, first to absorb ammonia from the liberated carbonic acid
and sulphuretted hydrogen in the dissociating vessel and thereafter lowering the
temperature of the outflowing caustic ammonia solutions by absorbing the heat
thereof substantially in the manner and for the purposes herein before described.
Third. The so utilizing solutions of caustic ammonia for the purification of coal
gas by causing the solutions and coal gas to travel in the same direction through
the washer or equivalent apparatus and by which similarity of direction of flow
the solution of salts of ammonia are caused to absorb any previously volatilized
ammonia and to hold the caustic ammonia in solution substantially as hereinbefore
described.
Fourth. The general arrangement of apparatus as hereinbefore described and
shewn upon the annexed sheet of drawings or other equivalent apparatus so com-
bined as to work in a like connection or combination for the purposes of practising
my Invention substantially as hereinbefore described.
1000