Improved Means for Recovering Cyanides from Waste Products in Gas, Chemical, and Iron Works,
Year: 1896

page_text: Date of Application, 7th Mar., 1896
Complete Specification Left, 4th Dec., 1896-Accepted, 9th Jan., 1897
PROVISIONAL SPECIFICATION.
Improved Means for Recovering Cyanides from Waste Products in
Gas, Chemical, and Iron Works,
We GEORGE PEARCE LEWIS of 2 Florence Villas, Helvetia Road, Catford in
the County of Kent, Engineer, and FREDERICK SOUTHWELL CRIPPS of
27 Great George Street, Westminster in the County of Middlesex, Civil and
Mechanical Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to means for recovering cyanides from the effluent or
"waste liquor" running from ammonia stills employed for distilling ammoniacal
liquor in gas, chemical, and iron works, and it may also be applied with the same
object to a liquor obtained in a manner to be hereafter described from "spent
oxide of iron obtained from gas works.
Crude ammoniacal gas liquor consists of a variety of ammonium compounds,
which are usually grouped into two classes, namely, those containing "free" and
"fixed" ammonia respectively.
The said gas liquor is found to contain sulphocyanide and ferrocyanide of
ammonia, which are classed as "fixed" ammonium compounds, and are, in common
with the remainder of this class, generally decomposed in the distilling towers by
the use of lime, the ammonia being set free, while the sulphocyanide and ferro-
cyanide combine with the lime to form sulphocyanide and ferrocyanide of calcium
(or the use of alkali, such as caustic soda, produces sulphocyanide and ferrocyanide
of that alkali)-in solution,-being found as such in the effluent liquor, which is
generally allowed to run into a sewer, or drain, as being valueless.
The description of apparatus and method of procedure is as follows:-
The effluent liquor is caused to flow into a cooling tank, where it is admixed with
a solution of sulphurous acid, or ferrous sulphate, and after standing for sometime,
is run through a strainer to clear it of lime in suspension, into another tank, where
it meets with a small stream of a solution of a copper salt, which precipitates the
sulphocyanide present as insoluble cuprous sulphocyanide. The supernatant liquid
is then run through another strainer into a third tank, in which it is treated with
a mixture of ferric and ferrous salts, and made acid with hydrochloric acid,
precipitating the ferrocyanide as Prussian blue, and finally the liquor is discharged
into a drain or sewer.
The precipitate of cuprous sulphocyanide is allowed to lie in the settling tank
until a sufficiency has accumulated for further treatment; it is then washed to
remove impurities, and may be utilized for producing various sulpho cyanides.
Supposing ammonium sulphocyanide is required, it is exposed to the action of a
liquid produced as follows:-
The gases evolved in ammonia stills consist principally of ammonia, sulphuretted
hydrogen, carbonic acid, and steam, and are generally passed through a saturator,
where the ammonia is almost entirely absorbed by an acid, such as sulphuric acid,
as in the well-known manufacture of ammonium sulphate; the remainder, together
with sulphuretted hydrogen and carbonic acid, pass up the outlet pipe, and are then
known as "foul gases," and are usually cooled by passing them through some form
of condenser, which causes them to deposit a liquid, which is sometimes almost in the
condition of ammonium sulphydrate, but this state of things is not always attained;

page_text: the liquid is therefore allowed to flow into a suitable form of gas washer, and is
passed into a stream of ammonia gas, until it is as nearly as practical in the
condition of ammonium sulphydrate.
Cuprous sulphocyanide is decomposed by ammonium sulphydrate in ammonium
sulphocyanide in solution, and a precipitate of sulphide of copper. The ammonium
sulphocyanide is separated by filtration, and may be obtained in the crystalline
condition by evaporation. The precipitated sulphide of copper may be reconverted
into a solution of copper salt by dissolving it in acids.
The same copper may thus be used over and over again for an indefinite number
of precipitations, with very little loss.
Potassium or sodium sulphocyanide and the like may be produced as follows:-
Potassium or caustic hydrate, as the case may be, is run into the washer mentioned
above, and a stream of the waste gases is passed into it, converting it principally
into sulphydrate of the alkali employed.
Potassium sulphydrate converts cuprous sulphocyanide into potassium sulpho-
cyanide and sulphide of copper, as before.
The solution of sulphurous acid for treating the effluent liquor may be obtained
by passing the "waste gases" through a furnace, so constructed and arranged as
to burn the sulphuretted hydrogen principally to sulphurous acid, the products
passing through a tower filled with bricks, coke, or the like, down which a stream
of water trickles, absorbing the sulphurous acid, and a portion of the other gases,
and flowing into a cooling tank for effluent liquor, as before described in this
specification.
The process may also be applied to a liquor obtained from "spent oxide of
iron" obtained as follows:-
The oxide is first freed from sulphur by any known methods, and it is then
soaked in water and boiled with lime, the resulting liquor being run into a cooling
tank, and treated as before described, with the same results.
Dated this 7th day of March 1896.
NEWTON & SON,
Agents for the Applicants.
Improved Means for Recovering Cyanides from Waste Products in
Gas, Chemical, and Iron Works.
We GEORGE PEARCE LEWIS of 2 Florence Villas, Helvetia Road, Catford in
the County of Kent, Engineer, and FREDERICK SOUTHWELL CRIPPS, of
27 Great George Street, Westminster in the County of Middlesex, Civil and
Mechanical 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 :-
This invention relates to neaus for recovering cyanides from the effluent or
"waste liquor" running from ammonia stills employed for distilling ammoniacal
liquor in gas works, chemical works, and iron works, and it may also be applied,
with the same object, to a liquor obtained in a manner to be hereafter described
from "spent oxide of iron," after doing duty as a purifying agent in the manufacture
of coal gas.
Crude ammoniacal gas liquor consists of a variety of ammonium compounds,
which are usually grouped into two classes, namely, those containing "free
ammonia" and "fixed ammonia" respectively.
The said gas liquor is found to contain sulpho-cyanide and ferro-cyanide of

page_text: ammonia, which are classed as "fixed" ammonium compounds, and are, in common
with the remainder of this class, generally decomposed in distilling towers by the
use of lime, the ammonia being set free, while the sulpho-cyanide and ferro-
cyanide combine with the lime to form sulphocyanide and ferro-cyanide of
calcium; or the use of an alkali, such as caustic soda, produces sulpho-cyanide
and ferro-cyanide of that alkali in solution in the effluent liquor, which is generally
allowed to run into a sewer or drain, as being valueless.
The mode of carrying out our invention is as follows:-
The effluent liquor is caused to flow into a cooling tank, where it is mixed with
a solution of sulphurous acid or ferrous sulphate, and, overflowing through au
interposed strainer (to clear it of lime in suspension), it is received into another
tank, where it meets with a small stream of a solution of a copper salt, which
precipitates the sulphocyanide present as insoluble white cuprous sulphocyanide.
The supernatant liquor is then run off as waste, or may, if required, be applied to
any useful purpose.
The solution of sulphurous acid, or sulphurous acid gases, for treating the
effluent liquor, can be obtained by passing the "waste gases" hereinafter described
through a furuace or kiln suitably constructed and arranged for converting the
contained sulphuretted hydrogen into sulphurous acid, the resulting products
passing through a tower filled with bricks, coke, or the like, down which a stream
of water trickles, absorbing the sulphurous acid and a portion of the other gases,
and flowing thence into a cooling tauk, or, alternatively, the effluent liquor may be
passed through a scrubber.
If the liquor is not treated with a reducing agent, such as sulphurous acid, before
adding the solution of a copper salt, black cupric sulphocyanide is precipitated,
which is partly soluble, whereas white cuprous sulphocyanide is insoluble.
The precipitate of cuprous sulpho-cyanide is allowed to lie in the settling tank
until a sufficient accumulation has been obtained for further treatment; it is then
washed, to remove impurities, and may be utilised for producing various sulpho-
cyanides.
Supposing ammonium sulpho-cyanide is required, it is exposed to the action of
a liquid produced as follows:-
The gases evolved in ammonia stills consists principally of ammonia, sul-
phuretted hydrogen, carbonic acid, and steam, and are generally passed through
a saturator, where the ammonia is almost entirely absorbed by an acid, such as
sulphuric acid, as in the well-known method of manufacturing sulphate of
ammonia. The remainder, together with sulphuretted hydrogen and carbonic
acid, pass up the outlet pipe, and are then known as waste or foul gases, and are
usually cooled by passing them through some form of condenser, which causes
them to deposit a liquid which is sometimes almost in the condition of ammonium
sulphydrate, but this state of things is not always attained. The liquid is there-
fore allowed to flow into a suitable form of gas washer, and a stream of ammonia
gas is passed through it, until the liquid is as nearly as practical in the condition
of ammonium sulphydrate.
"Waste" gases of similar composition to the above are also evolved in the
partial distillation of ammoniacal liquor, as in the well-known Hill's process of
ammoniacal liquor purification, and may also be applied with the same object.
Cuprous sulphocyanide is decomposed by ammonium sulphydrate into ammonium
sulphocyanide in solution, and a precipitate of sulphide of copper. The ammonium
sulphocyanide is separated by filtration, and may be obtained in the crystalline
condition by evaporation.
The precipitated sulphide of copper may be reconverted into a copper salt by
dissolving it in acids, such as sulphuric or hydrochloric acid. The same copper
may thus be used over and over again for an infinite number of times with very
little loss.
Potassium or sodium sulphocyanide and the like may be produced as follows:-
Potassium or sodium hydrate, or carbonate, as the case may be, is run into the

page_text: washer herein before mentioned, and a stream of the "waste" gases is passed
through it, converting it principally into sulphydrate of the alkali employed.
Potassium sulphydrate converts cuprous sulphocyanide into potassium sulpho-
-cyanide and sulphide of copper, as before.
The same result may also be achieved by mixing the cuprous sulphocyanide
with the alkali in a washer, and passing gases through, as before.
The process may also be applied to a liquor obtained from spent oxide of iron
-obtained as follows:-
The oxide is first freed from sulphur by any known and approved means, and
is then soaked in water and boiled with lime, thereby producing a solution con-
taining ferro-cyanide and sulpho-cyanide of calcium. This solution is run into a
cooling tank, where it is treated with sulphurous acid, as hereinbefore described,
and afterwards a stream of a mixture of ferrous and ferric salts of iron is run in,
producing a precipitate of Prussian blue. The supernatant liquor is then drawn
off into another tank, and treated for the recovery of cuprous sulpho-cyanide in
the manner hereinbefore described.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, we declare that what we
-claim is :-
1. Utilizing the "waste" gases evolved in the complete or partial distillation
of crude ammoniacal gas liquor, to produce sulphurous acid gas for preliminary
treatment of the hereinbefore mentioned liquors for the recovery of cyanogen
compounds.
2. Utilizing a portion of the "waste" gases referred to in Claim 1, to produce
alkaline sulphydrates for decomposing cuprous sulphocyanide.
3. The combination of the processes herein described, whereby waste products
which are sources of possible nuisance are applied to a useful purpose.
Dated this 3rd day of December 1896.
NEWTON & SON,
Agents for the Applicants.