Year: 1886

page_text: I, 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 18SI, 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
improvements 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 utilization 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 lar. 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 washed substantially in the manner described by
Hills (No. 510, 1870) with previously purified and concentrated ammoniacal liquor as
hereinafter described.
Any suitable apparatus may be employed. It is advantageous to use for the
purpose scrubbers packed with pieces of porous substance such as broken ganister
brick. In hereinafter further describing my invention I will assure such to be used.
Into one of these scrubbers, say the third, the purified and concentrated ammonia
liquor is introduced. It travels through this and the succeeding scrubbers in the
direction opposite to that taken by the gas and combines with and removes the
impurities contained in the gas. Into the last scrubber, cooled spent liquor from
the still is introduced in the manner hereinafter described for the purpose of washing
out the ammonia remaining in the gas. This liquor subsequently mixes in the third
scrubber with the purified and concentrated ammonia liquor. The introduction of
ammonia 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 much sulphide and bisulphide of
ammonium and the liquor 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. If the scrubbers contain enough amnionia as they will if the
directions given in the following part of this specification 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 introduced into the scrubbers 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, 1 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 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 consequently for the
time being uniform) quantity of purified ammonia liquor will be generated and
supplied to the scrubber or apparatus in which it is first exposed to the coal gas. 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 apart from
the purified ammonia liquor used in washing the gas.
Its volume is constantly
The
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 the system.
removal of the surplus spent liquor can be effected by well-known automatic con-
trivances. 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 an uniform
circulation of liquor throughout the system of scrubbers and towers can be maintained
and therefore an uniform addition of ammonia to the gas because the quantity of
caustic ammonia 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 caustic ammonia 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 he 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 to some extent upon their
dimensions but good results may be obtained with a series of seven. I do not confine

page_text: myself to this number but for the sake of illustration I will here assume that seven
are used, and will refer to them hereinafter as towers 1 to 7. 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, 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 Hill's. 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." 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. 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 methods described in the specification of my application
for Letters Patent bearing even date herewith and Nod. 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
ammonium.
From the heating towers in which the liquor is treated as herein before described
the liquor, which after such treatment contains little beside 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 herein before 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 towers may be described as
Nos. 6 and 7 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 ammonia and all ammonia present as carbonate or sulphide.

page_text: 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 sulphocyanide is the most important.
The spent liquor is then cooled and carried to the scrubbers as hereinbefore described.
The hot vapours from the still (No. 6) are cooled in suitable apparatus and the
resulting liquor is conveyed to the scrubber in which it is to be exposed to the action
of the coal gas. For the sake of economy the exhaust steam of the engine required
for pumping and other work may be utilized 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.
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 purified
and concentrated ammonia liquor and previously referred to as Nos. 1 to 7- may be
one fourth of the dimensions 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.
W. LLOYD WISE.
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.

page_text: I, 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 28th June 1881, and
No. 4644 dated 29th 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 separa-
tion and utilization 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
utilization 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 far. 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 washed substantially in the manner described by
Hills (No. 510 of 1870) with previously purified and concentrated ammoniacal liquor
as hereinafter described.
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
drawings annexed, which in Figs. 1 to 3 inclusive illustrate, as far as necessary, an
arrangement of plant I have found suitable 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 seven towers for
regeneration of caustic ammonia.
Fig. 2 is a vertical section of the condenser for obtaining the concentrated ammon-
iacal liquor.
Fig. 3 is a plan of the same. The passage of the various fluids are indicated in
the drawings by arrows of different forms thus;-coal gas O→→%3B ammonia gas o;
sulphuretted hydrogen and carbonic acid >1; liquors >H; steam
Into one of these scrubbers, say the third, (C), the purified and concentrated ammonia

page_text: liquor is introduced. It travels through this and the succeeding scrubbers (B and A)
in the direction opposite to that taken by the gas and combines with and removes the
impurities contained in the gas. Into the last scrubber (E) cooled spent liquor from
the still 6 and 7 is introduced in the manner hereinafter described for the purpose of
washing out the ammonia remaining in the gas. This liquor subsequently mixes in
the third scrubber (C) with the purified and concentrated ammonia liquor. The intro-
duction of ammonia 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 second scrubber contains little carbonate and much sulphide and bi-sulphide of
ammonium and is then suitablefor the removalof bi-sulphide 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. If the scrubbers
contain enough ammonia as they will if the directions given in the following part of
this specification 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 introduced into the scrubbers 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. It is, however,
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 bythe ammonia in the scrubbers, I provide(1) for the supply to such coal
gas of a stream of ammonia sufficient to combinewith the impuritiesto be removed from
the gas tobe purified, the stream of ammonia being practically uniformand bearing asfar
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 orthe impuritiesto be removed fromthe
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 finallyof spent liquor from thedistilling 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 purified ammonia liquor will be generated and
supplied to the scrubber or apparatus in which it is first exposed to the coal gas.
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 utilized. The
cooled spent liquor is the only liquor apart from the purified ammonia liquor used in
washing the gas. Its volume is constantly increased by the steam condensed in the
distilling apparatus, and the surplus is removed andcarried to a reservoirfor subsequent
treatment, so that practically the same volume of liquor always remains in circulation
through the 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 reservoirhigher than the scrubber which is to receive it, and inwhich
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 caustic ammonia 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 caustic ammonia
will be regulated by the quantity of liquor that is set in circulation through the system,
and this can easily be controlled.
The
Inthe abovedescribed method ofpurification it will be understood that a considerable
quantity of ammonia in the free or caustic state will always be present in the scrubbers

page_text: being retained in the porous material they contain. This will assist automatic purifi-
cation, 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 hereinbefore described, the liquor falling through
each. The exact number of towers required depends to some extent upon their
dimensions, but good results may be obtained with a series of seven. I do not confine
myself to this number, but for the sake of illustration I will here assume that seven
are used as in the arrangement of plant represented in the annexed illustrated
drawings, and will refer to them hereinafter as towers 1 to 7 as they are marked in
the drawings. No. 1 is a washing tower filled with porous material such as coke or
broken gamister 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 steam. These trays are nearly as large in length and
breadth as the tower. Steam is admitted to the trays (if jacketied) or coils (through
a reducing valve, if the steam pressure is subject to considerable variation), 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. 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 wafer 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 à 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 methods described in the specification of my application for Letters
Patent bearing even date herewith and Nod. 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,

page_text: the liquor, which after such treatment contains little beside 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 herein before referred to as No. 1 tower
filled with suitable porous substance such as broken ganister brick or coke. In the
series herein before adopted by way of illustration, the distilling towers may be
described as Nos. 6 and 7 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. 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 herein before described. The hot vapours from the still (No. 6) are
cooled in suitable apparatus and the resulting liquor is conveyed to the scrubber in
which it is to be exposed to the action of the coal gas. Apparatus suitable for the
preparation of concentrated ammoniacal liquor as that marked 8 in Fig. 1 is illustrated
at Figs. 2 and on the accompanying drawings. For the sake of economy the
exhaust steam of the engine required for pumping and other work may be utilized in
the towers. The scrubbers 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 carbonized in twenty four hours. However, where it is desired to
remove bisulphide of carbon to a greater extent, 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 purified and
concentrated ammonia liquor and previously referred to as Nos. 1 to 7 may be ono
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. 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
top of C. 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. Il 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 condenser
No. VIII in which the hot vapours are cooled and condensed into a liquid.
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 50 and 100 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

page_text: 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 fifty to one hundred gallons per
ton of coal carbonized.
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 hereinabove described modification of the combined and continuous process of
purifying coal gas claimed in the specification of my application for Letters Patent
No. 7580 of 1SSG.
Dated this 4th day of March 1887.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.