Year: 1886

page_text: Date of Application, 5th June, 1886.
Complete Left, 5th Mar., 1887.
Complete Accepted, 24th May, 1887.
1, CARL FRIEDRICH CLAUS, of Merton Road, South Wimbledon, in the county of
Surrey, Chemist, do hereby declare the nature of this invention to be as follows:-
In the specifications of previous patents No. 2838 dated 28 June 1881 and No. 4644
dated 29 September 1882, I have described methods for the purification of coal
gas by means of ammonia derived from the coal gas itself and for the separation and
utilization of bye-products, and my present invention has reference to certain improve-
ments whereby I am enabled to purify the gas automatically and almost completely in
close vessels by ammonia only, without lime or other chemicals, and with better utiliza-
tion of bye-products than heretofore. In order to a clear understanding of the nature
of my invention I will describe the whole cycle of operations which take part in it.
Crude coal gas from retorts is first cooled and freed from tar. This may be effected
by ordinary methods. It is advantageous to remove the tar as completely as possible
to obviate fouling of the apparatus hereinafter referred to as the scrubbers.
The gas when freed from tar is caused to pass through or in contact with ammoniacal
liquor (which has been partially saturated as will hereinafter appear) and thereafter
is mixed with ammonia gas. Any suitable apparatus may be employed. It is
advantageous to use for the purpose scrubbers packed with pieces of porous substances
such as broken ganister brick.
In hereinafter further describing my invention I will assume such to be used.
Liquor is supplied to the top of each of these scrubbers and meets the gas which rises
through them. After passing through say two of these scrubbers the gas is intimately
mixed with a suitable quantity of ammonia gas which is evolved from distilling
apparatus forming part of the purifying or regenerating plant hereinafter described.
This can be conveniently effected by allowing the ammonia gas to meet the coal gas
at the top of the pipe which carries the coal gas from the second to the third scrubber,
or it can be effected by leaving an empty space at the top of the second scrubber and
allowing the ammonia gas to enter and mix with the coal gas there. The introduction
of ammonia gas at the stage above indicated is advantageous inasmuch as in the first
scrubber the greater part of the carbonic acid is removed, therefore the liquor in the

page_text: second scrubber contains little carbonate and some sulphide and bisulphide of
ammonium and as little water enters with the ammonia the liquid after passing the
first scrubber is suitable for the removal of bisulphide of carbon which is effected by
exposing the gas to the action of the said liquor; this can be done conveniently by
pumping such liquor forward through one or more scrubbers. The coal gas, after
mixture with ammonia gas, is passed through the other scrubbers and in the last is
washed with spent liquor from the distilling apparatus as will hereinafter appear.
the scrubbers contain enough ammonia, as they will if the directions given hereinafter
are carried out, the gas leaving the last scrubber will be practically free from carbonic
acid, sulphuretted hydrogen and ammonia and deprived of a considerable part of its
bisulphide of carbon and cyanogen compounds.
If
The quantity of ammonia gas added to the coal gas should not be less than will be
equivalent to the impurities to be removed. It is however desirable to keep the
quantity as low as practicable in order that the ammonia shall do its maximum work
of purification. In order to effect the automatic purification of the coal gas by the
ammonia in the scrubbers, I provide (1) for the supply to such coal gas of a practically
uniform stream of ammonia sufficient to combine with the impurities to be removed
from the gas to be purified, and (2) for temporary variations of the volume of the gas
to be purified or the impurities to be removed from the gas to be purified. To fulfil
the first of these conditions the liquor is caused to circulate through the series of
apparatus by any suitable means (it may be by pumps) that will give an uniform
supply which can be regulated in accordance with the quantity of gas that is for the
time being required to be passed through the apparatus. In this way there is a
practically uniformi transfer of liquor from scrubber to scrubber of the gas purifying
apparatus and from them to the ammonia plant hereinafter described and from tower
to tower in the ammonia plant and finally of spent liquor from the distilling apparatus,
back to the last scrubber, that is, the scrubber through which the coal gas last passes.
It results with such an arrangement that a proportionate (and consequently for the
time being uniform) quantity of ammonia gas will be generated and supplied to the
scrubber or apparatus in which its admixture with coal gas is to take place. The
spent liquor is cooled before it goes to the scrubbers and the water used for cooling
may be fed into a steam boiler. The cooled spent liquor is the only liquor used in
washing the gas. Its volume is constantly increased by the steam condenser in the
distilling apparatus and the surplus is removed and carried to a reservoir for subse-
quent treatment, so that practically the same volume of liquor always remains in
circulation through this system. The removal of the surplus spent liquor can be effected
by well known automatic contrivances. For example it may be effected by carrying
the waste liquor to a tank or reservoir higher than the scrubber which is to receive it,
and in which the liquor is maintained at a constant level. By this or by some equivalent
means a uniform circulation of liquor throughout the system of scrubbers and towers
can be maintained and therefore a uniform addition of ammonia to the gas, because
the quantity of ammonia gas generated depends on the quantity of liquor which passes
through the ammonia plant. As long as the temperature of the heating and of the dis-
tilling apparatus is kept practically constant the generation of ammonia gas will be
regulated by the quantity of liquor that is set in circulation through the system, and
this can easily be controlled.
In the above described method of purification it will be understood that a con-
siderable quantity of ammonia in the free or caustic state will always be present in the
scrubbers being retained in the porous material they contain. This will assist
automatic purification because when there is any temporary increase in the volume of
crude coal gas, or in the quantity of impurity which it contains there will always be
enough free ammonia in the scrubbers to purify it for a considerable time.
For purifying or regenerating the ammonia for re-use in gas purification the plant
employed is a modification of that described in the specification of my patent No. 4644,
A.D. 1882. It consists of a series of towers through which liquor is pumped con
tinuously and in uniform quantity as herein before described, the liquor falling through
each. The exact number of towers required depends to some extent upon their

page_text: dimensions but good results may be obtained with a series of eight. I do not confine
myself to this number but for the sake of illustration I will here assume that eight
are used, and will refer to them hereinafter as towers 1. to S. No. 1. is a washing
tower filled with porous material such as coke or broken ganister brick. It is suppliod
with cooled waste liquor from the distilling tower No. 7. and its use is to prevent
any loss of ammonia. Nos. 2. and 3. towers are similar to No. 1. No. 2. tower
receives the gas liquor which is pumped to it as before described. The liquor which
is pumped to this tower is (1) the whole of the strong liquor from the first scrubber,
that is, the scrubber in which the gas first enters, and (2) the liquor from the
preceding wash tower. From tower No. 2. the liquor is pumped to tower No. 3.
from this to No. 4. and from this to No. 5. Nos. 4. and 5. towers are heating or
decomposing towers in which the liquor is exposed to a carefully regulated
temperature which should not exceed 200° F. as in the well known method of Hills'.
The heating towers Nos. 4. and 5. contain no ganister or other porous material but
instead a series of horizontal jacketed iron trays or coils lying in trays heated by close
steam. These trays are nearly as large in length and breadth as the tower. Steam is
admitted to the trays or coils through a reducing valve and it is thus easy by
regulating the valve to keep the temperature of the liquor at the desired point or
sufficiently near it. The liquor falls down from tray to tray and is thereby exposed
to the regulated heating for a considerable time. The liquor that enters the heating
tower No. 4. consists partly of liquor from the preceding tower No. 3. and partly of
liquor from the final tower of the system No. 8. Instead of having two heating
towers one of suitable dimensions may be used. By the above described treatment
the greater part of the carbonic acid and sulphuretted hydrogen are, as is well known,
expelled. These gases with vapour of water and some ammonia travel upward
through the towers through which the liquor is flowing to the heating towers; so
that as the liquor travels from No. 2. to No. 3. from No. 3. to No. 4. and from No. 4.
to No. 5. towers, the gases and vapours expelled from it travel from No. 5. to No. 4.
from No. 4. to No. 3. from No. 3. to No. 2. and finally pass through the wash tower
No. 1 where all remaining ammonia is removed. Carbonic acid and sulphuretted
hydrogen then escape in a nearly pure state and are carried to sulphur recovering
plant. The recovery of the sulphur can be effected as described in the specification of
my previous patent No. 3608 of 1882. As a precaution against possible loss of
ammonia a sulphuric acid catch tower or towers may be substituted for the washing
tower No. 1, herein before described. For this purpose a lead lined tower or towers
filled with pebbles or other suitable material may be used and the gases and vapours
from tower No. 2. may be passed through them. In the above described system of
purification by ammonia the ammonia naturally contained in the crude gas condenses
in the scrubbers together with that added for the purpose of removing impurities. A
quantity approximately equal to that contained in the crude gas is continuously or
periodically removed either in the form of ordinary gas liquor or by the methods
described in the specification of my application for Letters Patent bearing even date
herewith and numbered 7582. In this manner the total amount of ammonia
circulating in the plant remains unvaried and the purification is carried on
continuously by the same stock of ammonia. From the heating towers in which the
liquor is treated as hereinbefore described, the liquor, which after such treatment
contains little besides caustic ammonia some carbonate of ammonia and the fixed salts
of ammonia is pumped to the distilling towers. Any description of ammonia still
may be used but I prefer scrubber towers resembling in construction the wash tower
hereinbefore referred to as No. 1. tower filled with suitable porous substance such as
broken ganister brick. In the series herein before adopted by way of illustration the
distilling and condensing towers may be described as Nos. 6. 7. and 8. towers. The
liquor from the heating tower No. 5. falls through No. 6. Here it meets with the
hot ammoniacal vapours coming from the following tower No. 7. It is then pumped
to the top of No. 7. tower in which the distillation is completed. At the bottom of
this tower the liquor comes in contact with naked steam which is conveniently
supplied through a reducing valve. The steam of course expels from it all free

page_text: ammonia and all ammonia present as carbonate or sulphide. The spent liquor which
flows from the bottom of this No. 7. tower contains a certain quantity of fixed salts of
ammonia of which the sulpho-cyanide is the most important. The spent liquor is
then cooled and carried to the scrubbers as herein before described. The hot vapours
from the still (No. 6.) are carried to the final tower, No. 8, into which no liquor is
pumped. This is a condensing tower and very strong ammoniacal liquor, chiefly
carbonate of ammonia, accumulates in it, the excess being disposed of in any
convenient way, it may be by restoring it to the heating tower (No. 4.). From the
top of condensing tower No. 8. ammonia gas mixed with some vapour of water and
carbonic acid is transmitted to the scrubbers for the purpose of purification in
the manner herein before described. For the sake of economy the exhaust steam of
the engine required for pumping and other work may be utilized in the towers.
The scrubber required for the process of gas purification herein before described
should be of somewhat larger total cubic capacity than those usually employed, but
the combined dimensions need not exceed one hundred cubic feet for every ton of
coal carbonised in 24 hours. I do not confine myself to any precise number of
scrubbers, but good results may be obtained with a series of five. The towers used
in the preparation of the ammonia gas and previously referred to as Nos. 1 to 7 may
be one-fourth of the dimension of one of the scrubbers.
Before the complete purification of coal gas by the system herein before described
can be effected a sufficient quantity of ammonia must be in circulation through the
scrubbers and towers. The quantity employed may vary to a considerable extent,
but good results are obtained if the weight of ammonia in circulation through the
system varies between 50 and 100 lbs. for every ton of coal carbonized. The
quantity of spent liquor used as wash water in the last scrubber, which determines
the circulation throughout the system must be sufficient to yield at the base of the
first scrubber, that is the scrubber where the gas first enters, a liquor not weaker
than 10 ounce strength. This quantity is generally from 40. to 80. gallons per ton of
coal carbonized.
Dator this 4th day of Tune 1000
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Purification of Coal Gas.
1, CARL FRIEDRICH CLAUS, of Merton Road, South Wimbledon, in the County
of Surrey, Chemist, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-
In the specifications of previous Patents No. 2838 dated 28 June 1881 and
No. 4644 dated 29 September 1882, I have described methods for the purification of
coal gas by means of ammonia derived from the coal gas itself and for the separation
and utilisation of bye-products, and my present invention has reference to certain
improvements whereby I am enabled to purify the gas almost completely in close
vessels by ammonia (and water) only, without lime or other chemicals, and with
better utilisation of bye-products than heretofore. In order to a clear understanding
of the nature of my invention, I will describe the whole cycle of the operations which
take part in it. Crude coal gas from retorts is first cooled and freed from tar. This
may be effected by ordinary methods. It is advantageous to remove the tar as
completely as possible to obviate fouling of the apparatus hereinafter referred to as
the scrubbers.
The gas when freed from tar is caused to pass through or in contact with
ammoniacal liquor (which has been partially saturated as will hereinafter appear) and
thereafter is mixed with ammonia gas. Any suitable apparatus may be employed.
It is advantageous to use for the purpose scrubbers packed with pieces of porous
substance such as coke or broken ganister brick.
In hereinafter further describing my invention I will assume such to be used, and
for the purpose of making the invention clearly understood I will refer to tho
drawings annexed, which in Figs. 1 to 3 inclusive illustrate, so far as necessary, an
arrangement of plant I have found to answer well in practice, for the purification of
about 250,000 cubic feet of gas per day, but which may be varied as will be evident
and as hereinafter appears.
Fig. 1 is a block plan of plant comprising five scrubbers and eight towers for
regeneration of caustic ammonia.
Fig. 2 is a vertical section of one of the heating towers.
Fig. 3 is a plan of one of the trays of the heating towers with coil. The passage of
the various fluids are indicated in the drawings by arrows of different forms thus:-
coal gas ammonia gas C→; sulphuretted hydrogen and carbonic acid >→;
liquors steam
→.
Liquor is supplied to the top of each of the scrubbers and meets the gas which rises
through them. After passing though one or two of these scrubbers, the gas is
intimately mixed with a suitable quantity of ammonia gas which is evolved from
distilling apparatus (6 and 7) forming part of the purifying or regenerating plant
hereinafter described. This can be conveniently effected by allowing the ammonia
gas to meet the coal gas at the top of the pipe which carries the coal gas from the

page_text: second scrubber (B) to the third scrubber (C), or it can be effected by leaving an
empty space at the top of the second scrubber (B) and allowing the ammonia gas to
enter and mix with the coal gas there. Or they may meet at the inlet of the second
scrubber (B.) The introduction of ammonia gas at the stage above indicated is
advantageous, inasmuch as in the first scrubber (A) the greater part of the carbonic
acid is removed, therefore the liquor in the second scrubber (B) contains little
carbonate and some sulphide and bisulphide of ammonium, and as little water enters
with the ammonia, the liquor after passing the second scrubber (B) is suitable for the
removal of bisulphide of carbon, which is effected by exposing the gas to the action of
the said liquor; this can be done conveniently by pumping such liquor forward
through one or more scrubbers (say C and D). The coal gas, after mixture with
ammonia gas, is passed through the other scrubbers (say C, D, E,) and in the last (E)
is washed with spent liqifor from the distilling apparatus as will hereinafter appear.
If the scrubbers contain enough ammonia, as they will if the directions given herein-
after are carried out, the gas leaving the last scrubber will be practically free from
carbonic acid, sulphuretted hydrogen and ammonia, and deprived of a considerable
part of its bisulphide of carbon and cyanogen compounds.
The quantity of ammonia gas added to the coal gas should not be less than will be
equivalent to the impurities to be removed, by which I mean sufficient to take up and
form chemical combinations with the whole of such impurities. Whilst fulfilling this
condition, it is on the other hand desirable to keep the quantity as low as practicable
in order (inter alia) that the ammonia shall do its maximum work of purification.
In order to effect the purification of the coal gas by the ammonia in the scrubbers,
I provide (1) for the supply to such coal gas of a stream of ammonia sufficient to
combine with the impurities to be removed from the gas to be purified, the stream of
ammonia being practically uniform, and bearing as far as practical a constant
proportion to the impurities to be removed, and (2) for temporary variations of the
volume of the gas to be purified or the impurities to be removed from the gas to be
purified. To fulfil the first of these conditions, the liquor is caused to circulate
through the series of apparatus by any suitable means (pumps) that will give a
uniform supply which can be regulated in accordance with the quantity of gas that is
for the time being required to be passed through the apparatus. In this way there is
a practically uniform transfer of liquor from scrubber to scrubber of the gas purifying
apparatus, and from them to the ammonia plant hereinafter described, and from tower
to tower in the ammonia plant, and finally of spent liquor from the distilling
apparatus, back to the last scrubber, that is, the scrubber through which the coal gas
last passes. It results with such an arrangement that a proportionate (and con-
sequently for the time being uniform) quantity of ammonia gas will be generated and
supplied to the scrubber or apparatus in which its admixture with coal gas is to take
place. The spent liquor is cooled before it goes to the scrubbers, and the water used
for cooling may be fed into a steam boiler, or its contained heat may be otherwise
utilised.
The cooled spent liquor is the only liquor used in washing the gas. Its volume is
constantly increased by the steam condensed in the distilling apparatus and the
surplus is removed and carried to a reservoir for subsequent treatment, so that
practically the same volume of liquor always remains in circulation through this
system. The removal of the surplus spent liquor can be effected by well-known
automatic contrivances. For example, it may be effected by carrying the waste
liquor to a tank or reservoir higher than the scrubber which is to receive it, and in
which the liquor is maintained at a constant level. By this or by some equivalent
means a uniform circulation of liquor throughout the system of scrubbers and towers
can be maintained and therefore a uniform addition of ammonia to the gas, because
the quantity of ammonia gas generated depends on the quantity of liquor which
passes through the ammonia plant.
As long as the temperature of the heating and of the distilling apparatus is kept
practically constant, the generation of ammonia gas will be regulated by the quantity

page_text: of liquor that is set in circulation through the system, and this can casily be
controlled.
In the above described method of purification, it will be understood that a con-
siderable quantity of ammonia in the free or caustic state will always be present in
the scrubbers, being retained in the porous material they contain. This will assist
automatic purification, because when there is any temporary increase in the volume
of crude coal gas, or in the quantity of impurity which it contains, there will always
be enough free ammonia in the scrubbers to purify it for a considerable time.
For purifying or regenerating the ammonia for re-use in gas purification, the plant
employed is a modification of that described in the specification of my Patent
No. 4644, A.D. 1882. It consists of a series of towers through which liquor is
pumped continuously and in uniform quantity as herein before described, the liquor
falling through each. The exact number of towers required depends upon their
dimensions, but good results may be obtained with a series of eight.
confine myself to this number, but for the sake of illustration I will here assume that
eight are used as in the arrangement of plant represented in the annexed illustrative
drawings, and will refer to them hereinafter as towers 1 to 8 as they are marked in
the drawings. No. 1 is a washing tower filled with porous material such as coke or
broken ganister brick. It is supplied with cooled waste liquor from the distilling
tower No. 7, and its use is to prevent any loss of ammonia. Nos. 2 and 3 towers are
similar to No. 1. No. 2 tower receives the gas liquor which is pumped to it as
before described. The liquor which is pumped to this tower is (1) the whole of the
strong liquor from the first scrubber (A), that is, the scrubber in which the gas first
enters, and (2) the liquor from the preceding wash tower (No. 1). From tower No. 2
the liquor is pumped to tower No. 3, from this to No. 4, and from this to No. 5.
Nos. 4 and 5 towers are heating or decomposing towers in which the liquor is exposed
to a carefully regulated temperature which should not exceed 200° F. as in the well-
known method of Hills. The heating towers Nos. 4 and 5 contain no ganister or
other porous material, but instead a series of horizontal jacketted iron trays or coils
lying in trays heated by close sicam. The last mentioned arrangement is the one
illustrated in the drawings Figs. 2 and 3. These trays are nearly as large in
length and breadth as the tower. Steam is admitted to the trays (if jacketted) or
(in the arrangement shown) to the coils (through reducing valve if the steam
pressure is subject to considerable variation) and it is thus casy by regulating the
valve to keep the temperature of the liquor at the desired point, or sufficiently near
it. The liquor falls down from tray to tray, and is thereby exposed to the regulated
heating for a considerable time. The liquor that enters the heating tower No. 4
consists partly of liquor from the preceding tower No. 3 and partly of liquor from the
final tower of the system No. 8. Instead of having two heating towers, one of
suitable dimensions may be used. By the above described treatment, the greater
part of the carbonic acid and sulphuretted hydrogen are, as is well-known, expelled.
These gases with vapour of water and some ammonia travel upward through the
towers through which the liquor is flowing to the heating apparatus; so that as the
liquor travels from No. 2 to No. 3, from No. 3 to No. 4, and from No. 4 to No. 5
towers, the gases and vapours expelled from it travel from No. 5 to No. 4, from No. 4
to No. 3, from No. 3 to No. 2, and finally pass through the wash tower No. 1, where
all remaining ammonia is removed. Carbonic acid and sulphuretted hydrogen then
escape in a nearly pure state, and are carried to sulphur recovery plant. The recovery
of the sulphur can be effected as described in the specification of my previous Patent
No. 3608 of 1882. As a precaution against possible loss of ammonia, a sulphuric
acid catch tower or towers may be substituted for the washing tower No. 1 herein-
before described. For this purpose a lead lined tower or towers filled with pebbles or
other suitable material may be used, and the gases and vapours from tower No. 2
may be passed through them. In the above described system of purification by
ammonia, the ammonia naturally contained in the crude gas condenses in the
scrubbers together with that added for the purpose of removing impurities.
quantity approximately equal to that contained in the crude gas is continuously or
A

page_text: periodically removed either in the form of ordinary gas liquor, or by the methods
described in the specification of my application for Letters Patent bearing even date
herewith and numbered 7582. In this manner the total amount of ammonia circulating
in the plant remains practically constant, and the purification is carried on continuously
by the same stock of ammonia. From the heating towers in which the liquor is treated
as hereinbefore described, the liquor, which after such treatment, contains little
besides caustic ammonia, some carbonate of ammonia, and the fixed salts of
ammonia, is pumped to the distilling towers. Any description of ammonia still may
be used, but I prefer a scrubber tower resembling in construction the wash tover herein-
before referred to as No. 1 tower filled with suitable porous substance such as broken
ganister brick or coke. In the series hereinbefore adopted by way of illustration, the
distilling and condensing towers may be described as Nos. 6, 7, and 8. The liquor
from the heating tower No. 5 falls through No. 6. Here it meets with the hot
ammoniacal vapours coming from the following tower No. 7. It is then pumped to
the top of No. 7 tower in which the distillation is completed. At the bottom of this
tower the liquor comes in contact with naked steam. The steam of course expels from
it all free ammonia and all ammonia present as carbonate or sulphide. The spent
liquor which flows from the bottom of this No. 7 tower contains a certain quantity of
fixed salts of ammonia, including the sulpho-cyanide. The spent liquor is then cooled
and carried to the scrubbers as hereinbefore described. The hot vapours from the still
(No. 6) are carried to the final tower, No. 8, into which no liquor is pumped. This is
a condensing tower, and ammoniacal liquor, chiefly carbonate of ammonia, accumulates
in it, the excess Being disposed of in any convenient it
way, may be by restoring it to
the heating tower, (No. 4.) From the top of condensing tower No. 8, ammonia gas
mixed with some vapour of water and carbonic acid is transmitted to the scrubbers
for the purpose of purification in the manner hereinbefore described. For the sake of
economy the exhaust steam of the engine required for pumping and other work may be
utilised in the towers.
The scrubbers required for the process of gas purification hereinbefore described
should be of somewhat larger total cubic capacity than those usually employed, but the
combined dimensions need not exceed one hundred cubic feet for every ton of coal
carbonised in 24 hours. However where it is desired to remove bisulphide of carbon
according to the process described in my specification No. 7585 of 1886, scrubbers of
greater capacity may advantageously be employed, or the number may be increased.
I do not confine myself to any precise number of scrubbers, but good results may be
obtained with a series of five. The towers used in the preparation of the ammonia gas
and previously referred to as Nos. 1 to 7, may be one-half of the dimensions of one of
the scrubbers. Where a more compact plant is preferred, an arrangement may be
employed such as represented in Figs. 4 to 6 of the drawings.
Fig. 4 is a block plan.
Fig. 5 is a vertical section of the heating apparatus ; and
Fig. 6 is a plan of one of the trays of the heating apparatus.
In this modification, A, B, C, D, E, are five scrubbers of ordinary pattern, connected
and worked like those described with reference to the preceding arrangement of plant.
The crude coal gas enters at the bottom of A, and the ammonia for purification at the
bottom of B. In the plant for the regeneration of caustic ammonia, No. I is the
catch tower supplied with spent liquor from the distilling tower No. VI (corresponding
to Nos. 6 and 7 in the preceding arrangement) or with acid. No. II is a scrubber
tower (corresponding and worked similarly to the towers Nos. 2 and 3 in the preceding
arrangement). It receives the gas liquor from the scrubber A, and also the liquor from
No. I when spent liquor is used in this tower. From tower No. II the liquor is
pumped to the heating apparatus No. IV (corresponding to Nos. 4 and 5 in the
preceding arrangement) and overflows from tray to tray, being heated by steam
admitted underneath each liquor tray as shown in the drawings Figs. 5 and 6. The
purified liquor from No. IV is pumped to the ammonia distilling tower No. VI. The
ammonia and steam pass from the top of the distilling tower No. VI to a tubular
condenser No. VIII (corresponding to No. 8 in the preceding arrangement) supplied

page_text: with cold water. In this the excess of water is condensed, and from it the ammonia
passes to the scrubber B.
Before the complete purification of coal-gas by the system hereinbefore described
can be effected, a sufficient quantity of ammonia must be in circulation through the
scrubbers and towers. The quantity employed may vary to a considerable extent, but
good results are obtained if the weight of ammonia in circulation through the system
varies between fifty and one hundred lbs. for every ton of coal carbonised in 24 hours.
The quantity of spent liquor used as wash water in the last scrubber, which determines
the circulation throughout the system, must be sufficient to yield at the base of the
first scrubber, that is, the scrubber where the gas first enters, a liquor not weaker than
ten ounce strength. This quantity is generally from forty to eighty gallons per ton of
coal carbonised.
Having now particularly described and ascertained the nature of the said invention,
and in what manner it is to be performed, I declare that what I claim is :-
The combined and continuous method or process of purifying coal gas substantially
as above described.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.