Improvements in the Production of Sulphydrate of Calcium to be used in the Manufacture of Alkali and Sulphuretted Hydrogen, and in Apparatus therefor.
Year: 1890

page_text: Date of Application, 3rd Oct., 1890-Accepted, 29th Nov., 1890
COMPLETE SPECIFICATION.
Improvements in the Production of Sulphydrate of Calcium to be
used in the Manufacture of Alkali and Sulphuretted Hydrogen,
and in Apparatus therefor.
I, JOHN LEITH of Knowsley Road St. Helens in the County of Lancaster Manu-
acturing Chemist do hereby declare the nature of this invention and in what manner
he same is to be performed, to be particularly described and ascertained in and by
the following statement :-
This invention relates to the production of sulphydrate of calcium in a modified
method of conducting the manufacture of alkali and sulphuretted hydrogen as
described in the Parnell and Simpson Specification No. 381 of the year 1885
whereby the sulphide of calcium is converted into sulphydrate which is separated
from the inert and insoluble residue and is then employed in the distillation of
chloride of ammonium produced in the manufacture of alkali.
In order to carry out the operation in a simple and economical manner I cause the
gases which are given off from the carbonating plant such as that described in
Specification No. 381 of the year 1885 aforesaid to pass through a series of vessels
connected with each other by pipes and valves and containing a mixture of Le Blanc
alkali waste or other material containing sulphide of calcium and water.
sulphuretted hydrogen contained in the said gases is absorbed by the sulphide of
calcium in the waste thereby forming sulphydrate of calcium which enters into
solution.
The
The nitrogen contained in the gases which have passed through the sulphydrate
plant is allowed to escape into the atmosphere preferably after passing through a
tower in which it is brought in contact with milk of lime and also through a bed
of iron oxide for the purpose of eliminating any traces of sulphuretted hydrogen.
In practice I find a series of five vessels a convenient number to employ for the
production of sulphydrate of calcium. The gas containing sulphuretted hydrogen can
be passed through a series of three or four such vessels while one or two vessels are
being emptied and filled or kept in reserve.
When sulphuretted hydrogen begins to pass into the final vessel of the series-a
recently filled vessel is connected to the said final vessel-or this may be done at an
earlier period provided that the sulphide of calcium in the first vessel of the series has
by that time been converted into sulphydrate.
When the vessel longest in operation has its contents sufficiently converted into
sulphydrate, the current of gas is diverted to the next vessel in series while the
finished charge may be allowed to settle and the clear sulphydrate conducted to a
closed storage tank or tanks. After settling, the insoluble residue is preferably
washed with water or steam by filtration or other convenient method for removing
any traces of sulphur and the washings obtained may be employed further in the
process while the insoluble residue is discharged and may be utilized in the manu-
facture of cement.
The sulphydrate of calcium thus produced is employed in the still for liberating the
ammonia contained in the chloride of ammonium produced in the carbonating plant,
the operation resulting in the evolution of sulphuretted hydrogen and sulphide of
ammonium. These two gases or vapors are separated by condensation-the sulphide
of ammonium being absorbed in brine for treatment with carbonic acid in the alkali
manufacture while the sulphuretted hydrogen after being passed through a scrubber
containing brine or acid to absorb any ammonia is conducted to the gas-holder for
use as required and the chloride of calcium solution is run to waste or utilized. By
this method of working it will be seen that while all or nearly all the sulphuretted
hydrogen produced by the carbonating plant is employed for converting the calcium

page_text: sulphide of the waste into sulphydrate; the sulphuretted hydrogen which goes to the
gas holder is all or nearly all produced by the reaction of the chloride of ammonium
on the sulphydrate in the still. The advantages of this method of working are:-
First. As there is practically no solid matter to conie in contact with the chloride
of ammonium the loss of ammonia is greatly reduced.
Second. As the gases containing the sulphuretted hydrogen are under pressure
when they leave the carbonating plant and are used direct on the mixture of waste
and water, there is no necessity for separate pumping apparatus.
Third. Substantially the whole of the sulphur in the waste employed is converted
into pure sulphuretted hydrogen-the high strength obtained being a great advantage
in the conversion of the sulphur in the gas into brimstone.
Fourth. A considerable economy of steam is effected by reason of the reduced bulk
which passes through the still.
Fifth. A most important advantage in the use of sulphydrate of calcium over milk
of lime for distilling the chloride of ammonium consists in its allowing the heat
necessary for distillation to be conducted to the ammoniacal liquor under treatment in
the still through a closed steam coil or by external heat without the introduction of
steam into the charge. This advantage is due to the fact that there is practically no
deposit nor precipitate from the sulphydrate to prevent the conduction of heat.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I wish it to be distinctly understood
that I do not claim broadly the use of sulphydrate of calcium for distilling the
chloride of ammonium for use in the ammonia alkali process but, I declare that what
I claim is :-
First. The employment of the gases containing sulphuretted hydrogen which are
given off under pressure from the carbonating plant of the Parnell and Simpson
process as described in Specification No. 381 of the year 1885, for the con-
version of the sulphide of calcium employed in that process into sulphydrate of
calcium to be used in the distillation of chloride of ammonium.
Secondly. In the manufacture of alkali and sulphuretted hydrogen by the sub-
stitution of a solution of sulphydrate of calcium for milk of lime in the distilling
operation of the ammonia alkali process, the combination of carbonating apparatus,
scrubbers, vessels for absorbing sulphuretted hydrogen in sulphide of calcium and
water, stock tanks for sulphydrate, still and absorber substantially as set forth.
Dated the 2nd day of October 1890.
Per pro J. T. KING,
J. Johnson,
Agent.