Improvements in the Extraction of Cyanogen Compounds from Coal and Coke Oven Gas.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Extraction of Cyanogen Compounds from Coal
and Coke Oven Gas.
We, WILLIAM JAMES FARMER, of Eastcheap Buildings, Eastcheap, in the City of
London, Merchant, and JOHN MURRAY SOMERVILLE, of The Cottage, Farnborough,
in the County of Kent, Engineer, do hereby declare the nature of this invention
to be as follows:
In processes hitherto employed for the recovery or extraction of cyanogen com-
pounds existing in gases obtained by the destructive distillation of coal or slack,
it has been the practice to effect such recovery or extraction after the extraction
of the tar, ammonia, and other' products. The improvements herein set forth
are specially designed for the purpose of enabling the extraction of the cyanogen
compounds to precede that of the tar, ammonia and benzine compounds, without
the removal in any appreciable quantities of the hydrocarbon and ammonia gases
existing in the crude product of the retorts or ovens.
For this purpose the invention herein disclosed consists in the use of a ferrous
hydrate salt in a fine state of division mixed by a suitable mechanical agency with
carbonate of soda in the commercial form of soda ash in the proportion by weight
The solution
of 1 parts of iron salt to 1 part of soda ash and 14 parts of water.
of suspended salt is worked up in a mixing tank heated by a steam jacket or other
suitable agency, the apparatus being designed with a view to the rapid removal of
any large or coarse sediment contained in either of the materials and for the
efficient decanting of the solution into the mechanical extractor, which is preferably
arranged as part of the said mixing tank. Two types of extractors are used one
in which the gas is compelled to churn the solution in its passage through the
apparatus, thus preventing the suspended salt from settling, and the second type
allowing the gas a very free passage in order to relieve the retorts or ovens of
pressure by the circulation of the liquor over a considerable surface, over which the
gas is compelled to travel.
The first mentioned type of extractor consists of a series of trays containing
the solution or mixture to such a depth as to seal the perforated sides of an inner
chamber arranged as an inverted trough with perforated sides and concave top.
The sides of the trays are curved, and the gas passing into the interior of the
inverted trough forces the solution within to the outside in order to escape through
the perforations, and in so doing creates a churning action and produces foam. In
order to promote the continuity of this action, pipes are led downwards at certain
points in the hollow cover of the trough, and the liquid thrown upon the cover
through the churning action, is thus conveyed to the interior. Provision is made
for running the suspended solution from an upper chamber to one below.
The second type of extractor herein before referred to consists of a large exposed
surface over which the suspended solution runs in a constant stream, to the action
of the gas. This is done in a horizontal chamber having a series of upright louvre

page_text: frames. The louvres are of iron bars crossing the width of the chamber and con-
nected with each other by perforated sheeting. The solution containing the sus-
pended matter is run into the chamber and by an arrangement of tunnels conveyed
to the top of every louvre frame inside and allowed to flow down the superficial
area thus provided, in several streams spaced equidistant along the width. The
solution is decanted from the mixing tank by gravity and after falling down the
frames collects in a tank below the extractor. It is then pumped into the mixing
tank again for the purpose of keeping a constant circulation.
In both forms of apparatus suitable means are provided for raising and retaining
the temperature of the solution at about 140 degrees Fahrenheit. It is found that
at such a temperature ammonium salts do not form in the presence of carbonate
of soda, that the absorption of sulphuretted hydrogen by liquor heated to such a
degree is considerably diminished and that the hydrocarbon compounds are to a
great extent unaltered.
When the liquor has absorbed cyanogen compounds in sufficient quantity, it is
run off to a settling tank and, after being filtered, evaporated down to one-third
of its bulk; it is allowed to cool in suitable vessels when crystals of ferro-cyanide
of sodium settle out and are deposited.
By this process of extraction the cyanogen compounds before instead of after the
gas is subjected to the ordinary absorbing operations of washing and scrubbing for
the removal of tar and ammonia in the gas works plant, a larger quantity is
obtained without diminishing the quantities of the other bye products to an
appreciable extent.
Dated this 22nd day of February 1898
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.
Improvements in the Extraction of Cyanogen Compounds from Coal
and Coke Oven Gas.
We, WILLIAM JAMES FARMER, of Eastcheap Buildings, Eastcheap, in the City of
London, Merchant, and JOHN MURRAY SOMERVILLE, of The Cottage, Farnborough,
in the County of Kent, Engineer, 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 processes hitherto employed for the recovery or extraction of cyanogen com-
pounds existing in gases obtained by the destructive distillation of coal and slack,
it has been the practice to effect such recovery or extraction after the extraction
of the tar, ammonia, and other products. The improvements herein set forth
are specially designed for the purpose of enabling the extraction of the cyanogen
compounds to precede that of the tar, ammonia and benzine compounds, without
the removal in any appreciable quantities of the hydrocarbon and ammonia gases
existing in the crude products of the retorts or ovens.
For this purpose the invention herein disclosed consists in the use of a ferrous
hydrate salt in a fine state of division mixed by a suitable mechanical agency with
carbonate of soda in the commercial form of soda ash in the proportion by weight
of 1 parts of iron salt to 1 part of soda ash and 14 parts of water. The solution
of suspended salt is worked up in a mixing tank heated by a steam jacket or other
suitable agency, the apparatus being designed with a view to the rapid removal of
any large or coarse sediment contained in either of the materials and for the

page_text: efficient decanting of the solution into the mechanical extractor, which is preferably
arranged as part of the mixing tank. The gas is compelled to churn the solution
in its passage through the apparatus, thus preventing the suspended salt from
settling.
The accompanying drawing shows a vertical section of an extractor apparatus
constructed according to this invention.
The extractor comprises a series of trays a containing the solution or mixture to
such a depth as to seal the perforations b in the sides of an inner chamber or dome c
arranged as an inverted trough with concave top d. The sides e of the trays are
curved, and the gas passing into the interior of the inverted trough forces the
solution within to the outside in order to escape through the perforations, and in
so doing creates a churning action and produces foani. In order to promote the
continuity of this action, pipes f are led downwards at certain points in the hollow
cover of the trough c, and the liquid thrown upon the concave top d of the cover,
through the churning action, is thus conveyed to the interior.
The trays a are jointed together and to a base chamber g containing the gas
inlet orifice h and steam pipe i connected to any source of steam supply and are
surmounted by the mixing chamber containing the salt solution which is agitated
to prevent the deposit of the suspended matter by any suitable means. The mixing
chamber 9 and the trays a are connected together by means of pipes m provided
with regulating cocks n. The spent solution is drawn off through a pipe o.
Steam and gas having been adimitted through the pipe i and orifice h pass through
the curved centre e of the bottom tray down beneath dome c and through the
solution and so on through the remaining trays and through outlet p.
Suitable means are provided for raising and retaining the temperature of the
solution at about 140 degrees Fahrenheit. It is found that at such a temperature
ammonium salts do not form in the presence of carbonate of soda, that the absorp-
tion of sulphuretted hydrogen by liquor heated to such a degree is considerably
diminished and that the hydrocarbon compounds are to a great extent unaltered.
When the liquor has absorbed cyanogen compounds in sufficient quantity it is
run off to a settling tank and, after being filtered, evaporated down to one-third
of its bulk; it is allowed to cool in suitable vessels when crystals of ferro-cyanide
of sodium settle out and are deposited.
By this process of extracting the cyanogen compounds before instead of after the
gas is subjected to the ordinary absorbing operations of washing and scrubbing
for the removal of tar and ammonia in the gas works plant, a larger quantity is
obtained without diminishing the quantities of the other bye products to an
appreciable extent.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
1. Extracting the cyanogen compounds from crude gas before it enters the wash-
ing apparatus substantially in the manner described.
2. Extracting the cyanogen compounds without appreciable loss of ammonia and
sulphuretted hydrogen gases substantially as described.
3. The arrangement and construction of apparatus for extracting cyanogen com-
pounds comprising essentially a mixing chamber and a series of trays provided with
domes or inverted troughs connected to each other and to the said mixing chamber
and to a gas and steam supply the whole substantially as described and shown.
Dated this 22nd day of November 1898.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.