AN IMPROVED PROCESS FOR THE PURIFICATION OF COAL GAS AND OBTAINING AMMONIA AND AMMONIACAL AND OTHER COMPOUNDS THEREFROM "
Year: 1882

page_text: LETTERS PATENT to Carl Friedrich Claus, of Mark Lane, in the City of
London, Chemist, for an Invention of "AN IMPROVED PROCESS FOR THE
PURIFICATION OF COAL GAS AND OBTAINING AMMONIA AND AMMONIACAL
AND OTHER COMPOUNDS THEREFROM
"
PROVISIONAL SPECIFICATION left by the said Carl Friedrich Claus at
the Office of the Commissioners of Patents on the 29th September 1882.
}
CARL FRIEDRICH CLAUS, of Mark Lane, in the City of London, Chemist,
"AN IMPROVED PROCESS FOR THE PURIFICATION OF COAL GAS AND OBTAINING
AMMONIA AND AMMONIACAL AND OTHER COMPOUNDS THEREFROM
دو
My Invention relates to the purification- of coal gas by a process in which I
obtain ammonia, ammoniacal compounds and other products to be used in such
process or removed to be otherwise utilized.
In the Specification of my foriner Letters Patent No. 2838 A.D. 1881, I described
a process whereby gaseous ammonia may be obtained for the purpose of purifying
coal gas therewith. By the process thus described I distil gas liquor purified by
Hill's process in a still the vapours from the still passing through a series of
Woolf's bottles or like apparatus, or a series of Coffey's stills or towers, or scrubbers,
whilst the "purified" gas liquor passes through the same in an opposite direction;
the result being that the aqueous vapours accompanying the ammonia are con-
densed, and the ammonia escapes in a gaseous condition from the last of the
Woolf's bottles or towers and may be conducted into the coal-gas for the purpose of
purifying the same from carbonic acid and sulphide of hydrogen. The said former
specification also states that the last of these towers or other apparatus might be
fitted externally or internally with water coolers such as jackets or pipes through
which cold water circulates.
But according to my present improvements instead of cooling these Woolf's
bottles or towers I prefer to have a sufficiently great number of the same, so that
the larger quantity of purified liquor circulating through them will have the same
effect as the external cooling, that is to say, it will condense the aqueous vapours in

page_text: "
the last towers if the same are kept at a temperature below 160 or 190 degrees
Fahrenheit and thus permit only gaseous ammonia to depart from the last tower.
And I prefer to coat all the towers with non-conducting materials to keep in the
heat. I ani thus enabled to provide for circulating a larger quantity of " purified'
liquor through the apparatus with the consumption of a smaller quantity of steam
for vaporizing the ammonia and the ammoniacal compounds from the liquor,
obtaining at the same time still only gaseous ammonia from the last tower.
In my said specification I also describe the use of a still, (in which the "purified"
gas liquor is to be distilled) as a special part of the apparatus or plant. According
to my present improvements I find that a tower such as is commonly termed a
coke tower is the best form of still which can be used. Steam preferably super-
heated is passed into the bottom of the tower and travels upwards whilst the
liquor from the preceding tower is showered from the top downward in a finely
divided state.
I also use as the best form of condenser coke towers or apparatus equivalent
thereto.
When "purified" liquor is distilled in one or a series of these and the flow of
liquor at one end .and the quantity of steam at the other end are carefully
regulated, the liquor leaves the first of these towers (or other stills and condensers)
free from alkalinity, but it still contains fixed salts of ammonia, especially sulpho-
cyanide of ammonium. I prefer now to use the spent purified liquor when cooled
instead of water for washing down the scrubbers of the gas works. By doing this
repeatedly: I gradually accumulate the sulphocyanide of ammonium in the liquor.
When sufficiently enriched by these means with the said sulphocyanide I utilize
it for the production of commercial sulphocyanides, such as sulphocyanide of
barium.
66
I also stated in my said former specification that "the ammonia will pass in a
gaseous form, accompanied by some carbonate and sulphide of ammonium vapours
"out of the last condenser practically free from aqueous vapour" and that it might
be admitted in that condition to the coal gas for the purpose of purifying the
same. According to my present improvements I pass it first through a series
of large dry condensing chambers before admitting it into the coal gas. By these
means most of the carbonate of ammonia and sulphide of ammonium will be
deposited on the walls of these chambers in a crystalline or semi-crystalline
condition and may be used in this condition or may be dissolved in water and
gaseous caustic ammonia only passes forward into the coal gas.
According to Hill's said process of purifying crude gas liquor, the said liquor is
heated to a temperature of about 180° Fahrenheit whereby a large proportion of
the carbonic acid and sulphide of hydrogen contained in the gas liquor in com-
bination with ammonia becomes disassociated from the ammonia and escapes in
the free state.
According to my improvements I pass carbonic acid gas through the crude gas
liquor before heating the same as stated to 180° Fahrenheit or thereabouts.
By this treatment I convert the sulphide of ammonium contained in the gas
liquor into carbonate of ammonia whilst sulphide of hydrogen passes off in a free
state. When such carbonated gas liquor is now heated to say 180° Fahrenheit
carbonic acid gas only passes off from the gas liquor and such carbonic acid gas I
use for the aforementioned treatment of crude gas liquor.
The heating of the carbonated liquor to say 160° to 190° Fahrenheit or
thereabout may be carried out in a closed boiler or it may be effected by
showering the liquor down a coke tower and passing up steam from the bottom of
the tower in the opposite direction. To bring the carbonic acid liberated from the
carbonated and heated gas liquor into intimate contact with the crude gas liquor,
the latter may be showered down one or more towers (filled with coke or other
porous material or otherwise arranged to bring about a finely divided condition of
the crude gas liquor) whilst at the same time the said carbonic acid gas passes
through the tower or towers in the opposite direction. If the crude gas liquor

page_text: travels a sufficiently long distance in contact with carbonic acid, all sulphide of
ammonium in the same will be converted into carbonate of ammonia. On the
other hand sulphide of hydrogen escapes in the free state and passes in that
condition out of the last tower accompanied by a surplus of carbonic acid beyond
that required for the decomposition of the sulphide of ammonium present in the
crude gas liquor. The quantity or amount of such surplus or excess of carbonic
acid can be easily determined and is allowed to escape from that part of the apparatus
(that is to say, in the heating apparatus or near it) in which it is still
uncontaminated with sulphide of hydrogen.
The carbonic acid thus withdrawn from the apparatus need not be wasted but
may be employed for further carbonating the ammoniacal salts deposited in the
aforesaid dry condensing chambers in order to remove any sulphide present or to
convert the carbonate into bicarbonate.. When carbonated and. afterwards
'purified" liquor is distilled the product of the dry condensing chambers is of
course carbonate or sesquicarbonate of ammonia only and unmixed with sulphide of
ammonium.
"
By withdrawing as described the surplus of carbonic acid the gas escaping from
the last tower. becomes nearly pure sulphide of hydrogen.
1
The object of the process herein lastly described is partly to obtain the escaping
sulphide of hydrogen as free of other gases as possible, so that it may be more
advantageously utilized for the production of sulphur or sulphurous acid from the
same either by the process described in my specification filed July 29th 1882
N° 3608 or by any other known process.
It is obvious that the ammonia or ammoniacal compounds or other substances
obtained in or resulting from the above described process may be used therein or
for other purposes as may be desired.
"

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Carl Friedrich Claus in the Great Seal Patent Office on the
29th March 1883.
CARL FRIEDRICH CLAUS, of Mark Lane, in the City of London, Chemist
"AN IMPROVED PROCESS FOR THE PURIFICATION OF COAL-GAS AND OBTAINING
AMMONIA AND AMMONIACAL AND OTHER COMPOUNDS THEREFROM"
My invention relates to the purification of coal-gas by a process in which I obtain
ammonia, ammoniacal compounds and other products to be used in such process or
removed to be otherwise utilized.
In the Specification of my former Letters Patent N° 2838 A.D. 1881 I described a
process whereby gaseous ammonia may be obtained for the purpose of purifying
coal-gas. By the process therein described I distil gas liquor purified by "Hill's'
process in a still the vapours from the still passing through a series of Woolf's
bottles or like apparatus or through a series of Coffey's stills, or towers.or
scrubbers, whilst the "purified" gas liquor passes through the same in an opposite
direction; the result being that the aqueous vapours accompanying the ammonia
are.condensed and the ammonia escapes in a gaseous condition from the last of the
Woolf's bottles or towers and may be conducted into the coal gas for the purpose
of purifying the same from carbonic acid and sulphide of hydrogen. The said
former specification further states that the last of these towers or other apparatus
might be fitted externally or internally with water coolers such as jackets or pipes
through which cold water circulates.
But according to my present improvements instead of so cooling these Woolf's
bottles or towers I make the same of sufficient capacity or to use a sufficiently
great number of them to permit the circulation through them of a sufficiently
large quantity of purified liquor to have the same effect as the external cooling,
that is to say, it will condense the aqueous vapours in the last towers if the
same are kept at a temperature below 160 or 190 degrees Fahrenheit and
thus permit only gaseous ammonia accompanied by the vapours of the carbonate
and sulphide of ammonium to depart from the last tower. I prefer to coat
all or some of the towers with non-conducting materials to keep in the heat.
I am thus enabled to provide for the circulation of a larger quantity of "purified
liquor through the apparatus with the consumption of a comparatively small
quantity of steam for vaporizing the ammonia and the ammoniacal compounds
from the liquor obtaining at the same time still only gaseous ammonia and vapours
of ammoniacal compounds from the last tower.
86
In my said specification I also describe the use of a still. (in which the
purified" gas liquor is. to be distilled) as a special part of the apparatus or plant.
According to my present improvements I find that a tower such as is commonly
termed a coke tower is the best form of still which can be used. Steam preferably
superheated is passed into the bottom of this tower and travels upward whilst the
liquor from the preceding tower is showered from the top downwards in a finely
divided state. I also use as the best form of condenser coke towers or similar
apparatus.
When "purified" liquor is distilled in one or a series of these and the flow of
liquor at one end and the quantity of steam at the other end are carefully regulated,
the liquor leaves the first of these towers (or other stills and condensers) free from
alkalinity, but it still contains fixed salts of ammonia especially sulphocyanide of

page_text: ammonium. I prefer now to use the spent purified liquor when cooled instead of
water for washing down the scrubbers of the gas-works. By doing this repeatedly
I gradually accumulate the sulphocyanide of ammonium in the liquor. When
sufficiently enriched by these means with the said sulphocyanide I utilize the
liquor for the production of commercial sulphocyanides such as sulphocyanide of
barium.
Having as above specified substituted coke towers, Coffey's stills or apparatus
equivalent thereto for other forms of stills and condensers as described in the
specification of my said former Letters Patent and having abandoned as stated
the process of cooling the vapours emanating from the stills by means of
refrigerating appliances as therein set forth, my present mode of distilling the
'purified" liquors is carried on in the following manner viz. I use one or more
towers or apparatus similar to scrubbers or Coffey's stills closed on the top. The
tower is supplied at or near its top with any of the well known appliances for
equally distributing and showering down liquids in a finely divided state.
"
The body of the tower is filled in the well known manner with coke or other
porous material or with angle iron bars or any such appliances which will expose
a large surface of the liquid.
The "purified" liquor is pumped in a continuous or uninterrupted and measured
or regulated stream into the distributing apparatus at the top of the tower and is.
caused to trickle through the mass of coke or other material with which the tower
is filled. Steam, preferably superheated is blown in at the bottom of this tower
and ascends the same while travelling in the opposite direction to that in which
the purified liquor travels through the series of towers. The supply of steam is so
regulated that the liquor arriving at the bottom of the tower is free from
alkalinity.
After this operation has been carried on for some time and when it has assumed
its regular or normal working condition the temperature of the liquid in the upper
part of the tower should not exceed about 120 to 150° F. The supply of purified
liquor and of steam to the apparatus must therefore be so regulated that these
conditions may be maintained. The ammonia and ammoniacal compounds vaporised
by the action of the steam adınitted into the bottom of the tower rise to the upper
and colder part of the same and there become condensed in the liquid until such
liquid is so charged with ammonia and ammoniacal compounds that it is no longer
capable of taking up any more; consequently the said ammonia and vapours of
ammoniacal compounds pass out by an exit pipe at the upper part of the tower,
leaving most of the aqueous vapour behind them.
It will thus be seen, that the said tower acts in its lower part as a still, whilst
its upper part forms a condenser and that in it the purified liquor yields on the one
hand a continuous stream of gaseous ammonia (accompanied by vapours of ammoniacal
compounds) and on the other hand a regular continuous stream of liquid exhausted
of all volatile ammoniacal vapour and compounds. The quantity of purified gas
liquor to be distilled and consequently the size and dimensions of the tower must
be determined according to the quantity of gas to be purified with the ammonia
3 produced by the same. As about 300 gallons of purified liquor (containing about
two and a half per cent of ammonia) are required to be distilled for every ten
thousand (10,000) cubic feet of gas to be purified and as I have found that such a
quantity of purified liquor can be distilled conveniently in about thirty (30) cubió
feet of tower space the towers should be constructed with reference to these or
O somewhat similar proportions.
For small gas works one such tower might be found sufficient, but for large gas
works one tower of the relative proportionate dimensions would be unwieldy and
impracticable. I therefore employ two or more towers and pass the purified liquor
from the bottom of one to the top of the next and so on through the whole series of
the same whilst the steam, the ammonia and the vaporized compounds of ammonia
travel in an opposite direction.

page_text: ☐ To economise steam the tower or towers should be covered thickly with non-
conductors of heat. The towers may be of round or square section, but I prefer
such as have been described in the specification of Letters Patent dated January 20
A.D. 1877 N° 272.
The ammonia passes away in a gaseous form accompanied by some carbonate and
sulphide of ammonium vapours from the top of the towers or from the top of the
last of two or more towers being now practically free from aqueous vapour and this
ammonia instead of being at once admitted into the coal gas (for the purpose of
purifying the same as stated in the aforesaid specification of Letters Patent
N° 2838 A.D. 1881) is according to my present improvements first passed into one
or more condensing chambers before admitting it into the coal gas.
A chamber of about double the capacity of the distilling tower, that is to say a
chamber containing about sixty (60) cubic feet of space for every ten thousand
(10,000) cubic feet of gas subdivided into a number of compartments (or not so
subdivided) may be employed for the above purpose. In such a chamber most of
the carbonate of ammonia and sulphide of ammonium accompanying the gaseous
ammonia will become deposited on its walls and may be used in the condition.in
which it is thus found or may be first dissolved in water. The gaseous ammonia
thus more or less freed from the said ammoniacal compounds is allowed to pass
from the exit pipe of this condensing chamber into the coal-gas.
⚫ According to "Hills" well-known process of purifying crude gas liquor the said
liquor is heated to a temperature of about 180° to 200° Fahrenheit whereby a
large proportion of the carbonic acid and sulphide of hydrogen contained in the gas
liquor in combination with ammonia become disassociated from the ammonia and
escape in the free state.
According to my improvements I pass carbonic acid gas obtained from any source.
through the crude gas liquor before heating the same as stated to 180° Fahrenheit
or thereabouts.
-
By this treatment I convert the sulphide of ammonium contained in the gas
liquor into carbonate of ammonia whilst sulphide of hydrogen passes off in a free
state. When such carbonated gas liquor is now heated to say 180° to 200°
Fahrenheit carbonic acid gas only passes off from the gas liquor and I prefer to use
this carbonic acid gas for the aforementioned treatment of crude gas liquor.
The heating of the carbonated liquor to say 170° to 200° Fahrenheit or
thereabouts may be carried on in a closed boiler; or it may be effected by
showering the liquor down a coke tower and passing up steam from the bottom of
the tower in the opposite direction.
To bring the carbonic acid liberated from the carbonated and beated gas liquor.
into intimate contact with the crude gas liquor the latter may be showered down
one or more towers (filled with coke or other porous material or otherwise arranged
to bring about a finely divided condition of the crude gas liquor) whilst at the
same time the said carbonic acid gas passes through the tower or towers in the
opposite direction. If the crude gas liquor travels a sufficiently long distance in
contact with carbonic acid all sulphide of ammonium in the same will be converted
into carbonate of ammonia. On the other hand sulphide of hydrogen escapes in
the free state and passes in that condition out of the last tower accompanied
by a surplus quantity of carbonic acid that is to say a quantity in excess of that
required for the decomposition of the sulphide of ammonium present in the crude
gas. liquor. The quantity or amount of such surplus or excess of carbonic acid
can be easily determined and is allowed to escape from that part of the apparatus
(in the heating apparatus or near it) in which it is still uncontaminated with
sulphide of hydrogen.
The carbonic acid thus withdrawn from the said apparatus need not be wasted
but may be employed for further carbonating tlie ammoniacal salts deposited in
the aforesaid dry condensing chambers in order to remove any sulphide present
or to convert the carbonate into bicarbonate. When carbonated and afterwards

page_text: "purified" liquor is distilled the product of the dry condensing chambers is of
course carbonate or sesqui-carbonate of ammonia unmixed with sulphide of
ammonium. By withdrawing as described the surplus carbonic acid the gas
escaping from the last tower becomes nearly pure sulphide of hydrogen.
The object of the process herein lastly described is partly to obtain the escaping
sulphide of hydrogen as free of other gases as possible so that it may be more
advantageously utilized for the production of sulphur or sulphurous acid from
the same either by the process described in the specification of my Letters Patent
dated July 29th 1882 No. 3608' or by any other known process.
It is obvious that the ammonia or ammoniacal compounds or other substances
obtained in or resulting from the above described process may be used therein or
for other purposes as may be desired.
It has been shown by the above description that in the operations of distilling
the purified gas liquor and condensing the ammonia therefrom the operations of
saturating the crude gas liquor with carbonic acid gas and of heating the carbonated
gas liquor to 180° or 200° F (which operation has been termed "purifying") the
apparatus which I use is in all cases substantially the same in construction and is
worked in a similar manner, the only difference being one of dimensions. The
carbonating towers should be of about double or treble the capacity and the
heating towers of about twice the capacity of the distilling towers. I prefer to
increase the dimensions of the towers in the direction of the height of the column
rather than in a lateral direction
:
In order to explain how the operations of the process described in my above
cited previous specifications are modified by my present improvements I will now
describe the working of my process of gas purification by gaseous ammonia taken
as a whole and as I now practise it referring at the same time to the drawing
which illustrates a convenient arrangement of the apparatus which I employ
therefor.
Gaseous ammonia is admitted into the coal gas (after the latter leaves the con-
densers) in quantity equivalent to the quantity of carbonic acid and sulphide of
hydrogen present in the coal gas as impurities.. To insure a thorough mixing of
the ammoniacal gas with the coal gas, the mixture of gases is allowed to remain in
a large mixing chamber M for from 3 to 5 minutes.
From this mixing chamber the gaseous mixture passes into the scrubbers of the
ordinary gas plant. In these scrubbers the products of combination of the carbonic
acid and sulphide of hydrogen of the coal gas are absorbed into water, forming a
solution of these substances containing about eight or ten per cent of ammonia.
The scrubbers are indicated by S¹ S' S³ S. Water runs into S, when it reaches
the bottom of S4 it is raised by the pump P4 to the top of S³ from the bottom
of S³ it is raised by the pump P³ to the top of S² and so on until it reaches the
bottom of S¹.
The solution of carbonate of ammonia and sulphide of ammonium (commonly
called crude gas liquor) is now removed by pumps from the bottom of the scrubbers
and transferred to the plant or apparatus (extraneous and additional to the gas
plant) designed for the separation of ammonia from the impurities which have
been removed by the ammonia from the coal gas in the process of purification and
for the separation of carbonic acid from the sulphide of hydrogen with a view to
the conversion of such sulphide of hydrogen into commercial sulphur.
The said apparatus comprises a row of towers a¹ to a. The said towers have at
the bottom an inlet pipe and an outlet pipe. Immediately above these pipes there is
a grating or false bottom. In the body of each tower and resting upon the said false
bottom I place coke, broken bricks, angle iron bars, gratings or any other suitable
materials, or objects which will expose a large surface of any liquid, which may be
showered down upon it from above. Near the top of the towers and above the
coke or other materials with which they are filled are the upper ends of the outlet

page_text: pipes p to p. Immediately above these outlet pipes there is a contrivance for
producing a fine division of the liquid so that it may be equally distributed in the
form of rain or spray upon the coke or other material in the said towers. The
towers are closed at the top but inlet pipes o to o pass through their tops or covers
and by means of these pipes the liquids are supplied to the liquid distributing
appliances.
The crude gas liquor is raised by the pump u' and pipe 8' to the distributing
apparatus at the top of tower a¹ whence it is showered down upon the coke or
other material in the said tower and it passes through the mass of this material
until it reaches the bottom of tower a'. From the bottom of tower al it is then
raised by pump u² and pipe s² to the distributing apparatus of tower a²; it then
passes down through the body of tower a² to the bottom of the same and is raised
by the pumps us and pipe 83 to the top of tower a³ and so forth until the same
liquor has traversed the whole series of towers.
Into the bottom of the tower a steam (preferably superheated) is admitted by
the steam pipe q; the quantity of steam is so regulated that the liquor when it
reaches the bottom of this tower is free from alkalinity.
Steam is also admitted into tower a by the pipe q', but its admission is so
regulated that the liquor arriving at the bottom of this tower never has a higher
temperature than 190° to 200° Fahrenheit, which temperature must be carefully
and constantly maintained.
The crude gas liquor consisting of a solution of sulphide of ammonium, of
carbonate of ammonia and of a small quantity of sulpho-cyanide of ammonium as
it leaves the scrubbers contains as above stated about eight or ten per cent of
ammonia. This proportion is reduced by the addition of water (from tower a) as
hereinafter explained to such an extent that it only contains about two or two and
a half per cent of ammonia.
.
For reasons also hereinafter explained such diluted liquor after it has travelled
through towers a³, a² a³, a, to say tower as has lost the sulphide of hydrogen it
originally contained and has become a solution principally of carbonate of ammonia
or rather of sesqui carbonate and bicarbonate of ammonia.
When this liquor is now heated to 180° Fahrenheit the carbonic acid combined
with the ammonia begins to rapidly leave the ammonia and to volatilise the
ammonia not being volatilised. When the liquid is heated still further to 200° F the
practical maximum loss of carbonic acid has occurred that is to say if the heating
be continued beyond this point the ammonia would become volatilised a result
which is most undesirable.
:
The carbonic acid liberated as described rises in the tower a meeting the current
of gas liquor coming in the opposite direction. It passes from the top of the
tower a by the pipe 206 and enters the bottom of tower a³; thence it rises to the
top of tower as always meeting the descending gas liquor travelling in the opposite
direction it passes by the pipe p³ to tower a¹ and so on until it reaches the top of
tower a. The action of the carbonic acid upon the sulphide of ammonium
contained in the gas liquor, during this long passage and contact with the gas,
liquor in such a finely divided state, is to decompose the same thus liberating
sulphide of hydrogen which escapes and ultimately issues from the pipe p to be
disposed of as will be subsequently explained. The carbonic acid having taken the
place of the sulphide of hydrogen, forms with the ammonia, carbonate and sesqui-
carbonate and. ultimately as the liquor approaches the towers a³, a¹ and a³
bicarbonate of ammonia which meeting the steam in tower a³ becomes decomposed
as above.
a
As there is more carbonic acid in the crude gas liquor than is necessary to
decompose the sulphide of ammonium contained in the same and as there exists a
large store of carbonic acid in the form of carbonites of ammonia in the various
towers the surplus of this substance when once its quantity has been determined, 5
is drawn off from the towers a³ or at where it is still uncontaminated with.

page_text: sulphide of Hydrogen. If this is done the sulphide of hydrogen which passes out
of tower a by the pipe p is almost pure sulphide of hydrogen very little
contaminated with carbonic acid gas.
To insure that the sulphide of hydrogen escaping by pipe p shall not carry off
any ammonia with the sulphide of hydrogen the washing tower a is used as a
"catch tower" for the same..
:
:
Water is run down this tower in considerable quantities and when it reaches the
bottom of the same it is used for the aforementioned purpose of diluting the crude gas
liquor from the scrubbers to the strength required for the proper working of this
process. A part of the aforementioned spent liquor from tower a after having
been cooled, to the temperature of the atmosphere may be employed instead of
water in this washing tower if desired. The sulphide of hydrogen after leaving
the washing tower a is mixed with the required quantity of air, and allowed to
pass into the vessel or apparatus F where it is converted into sulphur according
to the process described in the Specification of the said former Letters Patent
N° 3608.
Returning now to tower a the liquor which arrives at the bottom of the same
(after having lost most of the carbonic acid which it contained when leaving tower
a and a now contains only caustic ammonia mixed with that quantity of carbonate
of ammonia about to of the quantity it contained). which was left unacted upon
by the process of heating the same to 180° to 200° Fahrenheit.
From this liquor the ammonia is distilled off in a gaseous form for the purpose of
purifying fresh quantities of coal gas. It is for this purpose raised by pump u to
the top of tower a7 and allowed to trickle down this tower and when it arrives at the
bottom thereof it is raised by pump us to the top of tower a³ and from tower as to
a descending in the latter and meeting on its way the steam which as above
described passes from the bottom toward the top of tower a³. It drives before it
the ammonia contained in the liquor on entering the tower a³. This ammonia
passes off by the pipe p8 to the bottom of tower a.
The liquor leaving the bottom of tower a³ is as above stated free from alkalinity
and the ammonia. it originally contained travels in the direction of tower a³ in
which the temperature is lower than in tower a³ and lowest at the top. In this
colder liquid the ammonia becomes absorbed until the liquid.is completely saturated
with ammonia and can take up no more. The ammonia consequently escapes by
pipe p' accompanied by vapour of carbonate of ammonia. To prevent the passing
away of any steam by the pipe p7 the temperature of the liquor at the top of
tower a should never be allowed to exceed 150° to 170° Fahrenheit. For this
reason the gas liquor which leaves the bottom of tower a and which has a tempera-
ture of about 200° F is cooled in the cooling worm W to about 120° F before it is
pumped into tower a. The mixture of gaseous ammonia and vapour of carbonate
of ainmonia is now carried into a chamber or vessel C in which the carbonate of
ammonia is deposited as a crystalline mass, whilst the gaseous ammonia is allowed
to pass by pipes into the mixing chamber M wherein it is mixed with the crude
coal gas for purifying the same (as described at the commencement of this
description) the cycle of operations being thus completed.
Having thus fully described my said invention and the manner of performing the
same I wish it understood that I do not claim any of the hereinbefore described
chemical reactions separately or apart from their use and application in the process
herein before described, but I claim.
The improved process in the purification of coal gas for the production of a
continuous and regular stream of gaseous ammonia as herein before described and
for the purposes set forth.
And I claim in the above described process
Treating crude gas liquor (obtained in the purification of coal gas by means of
gaseous ammonia) with carbonic acid gas for the purposes of decomposing the
sulphide of ammonium therein and converting the same into a source of sulphide of.

page_text: hydrogen and of carbonic acid practically unmixed with sulphide of hydrogen as
herein described.
Also, The separation from carbonated gas liquor of carbonic acid contained in
the same in the manner and for the purposes above described.
Also, Distilling gas liquor in a series of stills or towers which will produce gaseous
ammonia accompanied by vapours of carbonate of ammonia at one part or end of
the plant whilst a liquid free from alkalinity passes away from the other end thereof
as above described and for the purposes specified.
Also Freeing the gaseous ammonia from the carbonate of ammonia accompanying
the same by passing both through condensing chambers before admitting the gaseous
ammonia into the coal gas plant for the purpose of purifying the coal gas.
In witness whereof I the said Carl Frederich Claus have hereunto set my
hand and seal this twenty eighth day of March in the year of our Lord One
thousand eight hundred and eighty three.