Improvements in Recovering Sulphur from Sulphuretted Hydrogen.
Year: 1896

page_text: Date of Application, 23rd June, 1896
Complete Specification Left, 11th Mar., 1897-Accepted, 17th Apr., 1897
PROVISIONAL SPECIFICATION.
Improvements in Recovering Sulphur from Sulphuretted
Hydrogen.
We, JOHN BROCK, Director of The United Alkali Company Limited, and
FERDINAND HURTER, Ph.D., Chemist, both of G11 Exchange Buildings,
Liverpool, in the County of Lancaster, do hereby declare the nature of this
invention to be as follows:-
Hitherto sulphuretted hydrogen gas obtained by the decomposition of metallic
sulphides with an acid or otherwise has been treated for the recovery of its sulphur
on a large scale either :-
By mixing the sulphuretted hydrogen gas in definite proportions with sulphurous
acid gas and passing the mixture through water or a saline solution when the
hydrogen of the sulphuretted hydrogen combined with the oxygen of the sulphurous
acid to form water and the sulphur of both the sulphuretted hydrogen, and the
sulphurous acid, was precipitated; or,
The sulphuretted hydrogen. gas was mixed with a definite proportion of
atmospheric air and the mixture passed through what is known as a "Claus kiln,"
when at the elevated temperature of the kiln the oxygen of the air combined with
the hydrogen of the sulphuretted hydrogen to form water and the sulphur was
separated as vapour and afterwards condensed.
Our invention consists in obtaining sulphur from sulphuretted hydrogen gas.
by mixing the gas with a definite proportion of sulphurous acid gas and passing
this mixture through a Claus kiln, when the following reaction takes place :-
2 H₂SSO, = 2 H2O + 3 S.
The gases should be mixed so that for every two molecular proportions of
sulphuretted hydrogen there shall be present one molecular proportion of
sulphurous acid gas. Inert gases may also be present, but we prefer not to have
much oxygen present. If oxygen is present, the proportion of the gases must be
so adjusted that there shall be sufficient hydrogen in the gaseous mixture to
combine both with the oxygen of the sulphurous acid and with the free oxygen to
form water.
We prefer as the source of sulphuretted bydrogen the gas obtained by the
action of lime kiln gases upon alkali waste; but it may be otherwise obtained, and,
as the source of sulphurous acid, the products of combustion of sulphur or pyrites
in air. It is advisable to avoid arsenical pyrites and to separate all dust from the
sulphurous acid gas by washing, by filtration, or otherwise. If arsenical pyrites
are used they should be cooled so as to deposit all arsenic in form of arsenious acid
and then be filtered.
The mixed gases are passed through an ordinary Claus kiln, that is a chamber
filled with oxide of iron or bricks or the like and kept at an elevated temperature.
As the reaction evolves much less heat than the old process of burning sulphuretted
hydrogen in air, the kiln must be protected against loss, of heat and may require
the application of heat externally.
Dated this 23rd day of June 1896.
:
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.

page_text: mode of treatment and with this gas we mix sulphurous acid gas obtained by burning
iron pyrites or zinc blende in air.
If the sulphurous acid gas contain arsenic we cool the gas to ordinary temperature
so as to deposit the arsenic in the solid form, then pass it through a coke scrubber
in which the gas meets a stream of sulphuric acid to wash out dust and any
remaining arsenic.
We then pass the washed gas through a dry scrubber or filter filled with coke,
or other suitable material. The gas so purified is then mixed with the sulphuretted
hydrogen gas in suitable proportiou to be ascertained by testing, so that the
oxygen contained in, or with, the sulphurous acid gas, both free and combined,
shall be just sufficient to combine with the hydrogen contained in the sulphuretted
hydrogen to form water.
This gaseous mixture is conveyed into a Claus kiln maintained at the proper
temperature. We find that it is necessary to commence operations with a mixture
of sulphuretted hydrogen gas and air and to continue feeding the kiln with this
mixture until the requisite temperature (from 400 to 600° Fahrenheit) has been
attained, and then to introduce the mixture of sulphurous acid and sulphuretted
hydrogen. The kiln will then maintain its temperature provided it be well
protected against loss of heat by radiation.
If the sulphurous acid contain no free oxygen it may be necessary to apply
external heat to the kiln. We have found it advantageous to work with a gas
containing from 12 to 13 per cent. of SO, aud from 5 to 6 per cent. of oxygen, when
the heat of the reaction is sufficient to maintain the temperature of the kiln without
the use of other source of heat.
The proper admixture of the two gases may be judged by testing the exit gases
from the Clans kiln, and be regulated according to these tests in the way
now done in the Chance process for the recovery of sulphur from sulphuretted
hydrogen.
The sulphur flows out from the Claus kiln into the usual sulphur pan from which
it is withdrawn from time to time.
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. In the recovery of sulphur from sulphuretted hydrogen, the addition of
sulphurous acid gas in equivalent proportion to the sulphuretted hydrogen, and
passing the gaseous mixture through a Claus kiln substantially as hereinbefore
described.
2. In the recovery of sulphur from sulphuretted hydrogen, adding to the
sulphuretted hydrogen gas a mixture of sulphurous acid, oxygen, and inert gases,
proportioning the hydrogen and oxygen as hereinbefore set forth, and passing the
mixture through a Claus kiln, substantially as herein before described.
Dated this 11th day of March 1897.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.