Improved Means for Obtaining Oyanides from Illuminating and Heating Gas.
Year: 1892

page_text: Date of Application, 18th May, 1892
Complete Specification Left, 20th Feb., 1893-Accepted, 8th Apr., 1893
PROVISIONAL SPECIFICATION.
Improved Means for Obtaining Oyanides from Illuminating and
Heating Gas.
1, WILLIAM FOULIS of 45 John Street Glasgow, in the County of Lanark,
Civil Engineer do hereby declare the nature of my invention to be as follows:-
My invention has for its object to provide means whereby cyanides contained in
illuminating and heating gas are obtained in a marketable form with facility and
economy.
According to my invention I pass the gas, after the ammonia has been removed
from it, through, or in contact with, a solution of carbonate of potash, or carbonate
of soda in which solution carbonate or other suitable salt of iron is maintained
in suspension by causing the said gas on its way from the ammonia scrubbers to
the purifiers to pass through the said solution having the compound of iron in
suspension: so that the gas itself constitutes the means whereby the iron compound
is maintained in suspension. A convenient way of obtaining carbonate of iron for
use in the process (which I will presume is the salt of iron to be used) is to take
chloride of iron and add to it a solution in water, of carbonate of soda sufficient to
decompose the chloride of iron, forming chloride of sodium and carbonate of iron
which latter, being insoluble in water, precipitates; the supernatant liquid
(consisting of a solution of chloride of sodium) being run off and, if required,
treated for the obtainment of the salt by crystallization. The carbonate of iron,
and a solution of carbonate of potash, or of soda, are then introduced into a vessel
provided with a stirring, or agitating device, such as blades, or stirrers and these
are operated so as to maintain the carbonate of iron in suspension. The mixture
is then run in quantities intermittenly, or in a small continuous stream or streams
into the upper part of a vessel containing a number of superposed shallow trays,
the liquid passing downwards, from one to the other of the said trays maintaining
only a small depth of liquid in each tray. The said vessel has, at its lower part,
an inlet for gas, leading from the ammonia scrubbers and, at its upper part, an
outlet for the gas leading to the purifiers. The gas passes upwards through the
vessel from tray to tray by means of a number of short pipes standing up from the
bottoms of the trays and provided with hoods which dip nearly to the bottoms of
the trays so that the gas passes thereunder at or near to, the bottom of the liquid
contained in the trays, and then passes up through, and out of, the liquid
maintaining, in its passage through the liquid, sufficient agitation thereof to keep
the carbonate of iron in suspension. As the gas so passes through the liquid the
cyanides in the gas are removed therefrom being converted into ferro-cyanides of
potassium, or of sodium (according to the alkali employed) and retained in
the liquid.
Or instead of the foreging method the compound of iron and alkali may be
exposed to the action of the gas on large surfaces wetted therewith, the iron
compound being kept in suspension by mechanical agitation. The liquid is drawn
off, and evaporated to dryness, by fire heat, or otherwise, (it can be done best in
an iron pan with a fire underneath it) and to the cake, which is the result of this
process, water is afterwards added, which dissolves the soluble cyanide salts therein,
the carbonaceous, or other, impurities depositing freely from the clear liquor which
The ferro-
it would not have done but for the previous evaporating process.
cyanides can be obtained in the crystalline form by slightly evaporating the liquor.
The sludge, which is removed from the vessel in which the cyanides have been

page_text: dissolved from the cake may be treated for the recovery of any iron cyanides or
other matter of any value, there may be in it.
Dated this 18th day of May 1892.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improved Means for Obtaining Cyanides from Illuminating and
Heating Gas.
I, WILLIAM FOULIS of 45 John Street Glasgow in the County of Lanark,
Civil 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:-
My invention has for its object to provide means whereby cyanides contained in
illuminating and heating gas are obtained in a marketable form with facility and
economy.
According to my invention I pass the gas, after the ammonia has been removed
from it through or in contact with a solution of carbonate of potash, or carbonate
of soda in which solution carbonate, or oxide of iron is maintained in suspension
which may be effected by causing the said gas, on its way from the ammonia
scrubbers to the purifiers to pass through the said solution having the carbonate or
oxide of iron in suspension, so that the gas itself constitutes the means whereby
the carbonate, or oxide of iron is maintained in suspension. A convenient way of
obtaining carbonate of iron for use in the process is as follows, but I do not limit
myself thereto.
Take five gallons of a solution of chloride of iron (containing about 1.5 lbs. of
metallic iron per gallon) and add to it a solution in about 30 gallons of water
of 15 lbs. of soda-ash (containing 98 per cent. of carbonate of sodium). A double
decomposition takes place and chloride of sodium and carbonate of iron are
formed which latter being insoluble in water precipitates the supernatant liquid
(consisting of a solution of chloride of sodium) being run off, and if required
heated for the obtainment of the salt by crystallization. The carbonate of iron
thus obtained together with a solution of 27 pounds of soda-ash made up to
40 gallons with water are then introduced into an apparatus wherein the mixture
is subjected to agitation whilst the gas deprived of its ammonia is brought into
contact therewith. The gas in passing through this apparatus parts with the
cyanide it contains forming ferro-cyanide of soda or potash as the case may be.
If carbonate of potash be used instead of soda to treat the carbonate of iron
35 pounds of carbonate of potash may be used in place of the above named
27 pounds of carbonate of soda.
Figure 1 is a sectional elevation and Figure 2 is a section at right angles
thereto (the latter only of the upper part) of an apparatus adapted for the
purpose.
The mixture is poured by the opening a into the mixing vessel or stirrer shewn
at A and is therein kept agitated by the blades a³ on the rotating shaft a¹ and
from thence the mixture is admitted (either in quantities intermittently or in a
continuous small stream) by the opening a³ and valve a' into the scrubber Bas
required, it descending from shelf 6 to shelf by overflowing and passing down the
pipes c. The gas is admitted at d from the ammonia scrubbers and passes up.
through the pipes c which are covered by hoods e with openings at bottom which
may be serrations with their points resting on the shelves b so that the gas is com-
pelled to pass down into the mixture between the pipes c and hoods e and up
through the said mixture from compartment to compartiment of the scrubber B and
the said gas keeps the liquid so agitated that the carbonate of iron is kept:
suspended therein, the gas eventually passing off by the outlet 9. The gas is

page_text: during its passage through the scrubber B exposed to the mixture for a sufficient
time to cause the cyanides to be removed therefrom, they being retained in the
liquid (in the form of ferro-cyanides) which liquid can be withdrawn from time to
time for treatment (for example as hereinafter described) for the obtainment of the
cyanide in a commercially available form.
There may be a pipe with branches (provided with valves f³ f*) leading
from each shelf and with valves at f in the pipe f so that any compartment may
be shut off or the liquid can be drawn off from either compartment as desired by
opening valves f*.
Or instead of the foregoing method the compound of iron and soda or potash
may be presented to the gas by other means for example by the gas being exposed
on large surfaces wetted with the mixture the carbonate or oxide of iron being
kept in suspension by mechanical agitation. An arrangement for the purpose may
consist of brushes with their lower parts revolving in the mixture so as to con-
tinually agitate it from the bottom and present freshly wetted surfaces to the gas
passing through the upper part of the vessel containing the mixture and the
brushes. As aforesaid I may use oxide of iron in place of carbonate of iron for
the mixture. The liquid drawn off from the scrubber B may be evaporated to
dryness by fire heat or otherwise, (it can be done best in an iron pan with a fire
underneath it) and to the cake, which is the result of this process water is after-
wards added which dissolves the soluble cyanide salts therein the carbonaceous or
other impurities depositing freely from the clear liquor which it would not have
done but for the previous evaporating process. The ferro cyanides can be obtained
in the crystalline form by slightly evaporating the liquor.
The sludge which is removed from the vessel in which the cyanides have
been dissolved from the cake may be treated for the recovery of any iron cyanides
or other matter of any value there may be in it.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
First. The treatment of illuminating and heating gas for obtaining cyanides
therefrom by first removing the ammonia from the said gas and then causing the
gas from which the ammonia has been removed to pass through or in contact with a
solution of carbonate of soda or of potash in which carbonate or oxide of iron is
maintained in suspension substantially as herein before described.
Second. The treatment of illuminating and heating gas for obtaining cyanides
therefrom by first passing the said gas through the ammonia scrubbers and after-
wards through a solution of carbonate of soda or of potash in which solution
carbonate or oxide of iron is kept in suspension by the gas being caused to pass
up through the mixture or in contact with surfaces wetted therewith substantially
as herein before described.
Third. The treatment of illuminating and heating gas for obtaining cyanides
therefrom by first passing the said gas through the ammonia scrubbers and after-
wards through a solution of carbonate of soda or of potash with carbonate or oxide
of iron kept in suspension in the said solution by mechanical means so that it is
properly mixed as it is supplied to and whilst it is in the scrubber or like apparatus
in which the gas is brought into contact with the mixture substantially as herein-
before described with reference to the accompanying drawings.
Fourth. The treatment of the liquor the result of the aforesaid operation by
first evaporating it to dryness and then adding water to the cake so obtained to
dissolve the soluble cyanide salts therein substantially as hereinbefore described.
1
1000
J. H. JOHNSON & Co.,
Agents.