IMPROVEMENTS IN THE PURIFICATION OF GAS
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by Augustus George Vernon
Harcourt at the Office of the Commissioners of Patents, with his
Petition, on the 12th November 1870.
I, AUGUSTUS GEORGE VERNON HARCOURT, of Christ Church, in the
City of Oxford, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE PURIFICATION OF GAS," to be as follows:―
This Invention consists of two distinct and separate processes, either
of which may be used singly or the two combined, each and both having
for their object the more complete removal from the gas of impurities
existing as sulphur compounds.
The first of these processes aims at converting the sulphur contained
in coal gas (other than in the form of sulphuretted hydrogen) into
sulphuretted hydrogen. For this purpose a mass of iron turnings, wire,
or other suitable material is thrust into the mouthpiece of the retort
after charging, the whole of the said mass being so compacted as to be
easily removable. In this position it acquires a temperature of low
redness, which it communicates to the gas passing through it. By this.
means the bisulphide of carbon contained in the gas is decomposed, and

page_text: its sulphur combines with hydrogen, forming sulphuretted hydrogen,
which it is comparatively easy to remove. The same result may be
obtained by conducting the gas, at any subsequent stage of its course
between the retort and the purifiers, through a tube or system of tubes
or chamber of any form heated by any convenient method to low
redness and partially filled with suitable heat conducting and surface
presenting material.
The second process if adopted in combination with the foregoing
would be used subsequently, and if used alone would be applied to the
gas anterior to its passing through the ordinary purifiers, the object of
this being the extraction of a part of the sulphur and ammonia more
economically than by any method hitherto in use. With this view it is
proposed to wash or scrub the gas with water in which oxide of iron is
suspended contained in a vessel similar to a wet lime purifier, in which
the liquid is to be agitated and brought as effectually as possible into
contact with the gas. As the oxide of iron would soon become inert by
reason of its conversion into sulphide of iron, it is necessary to revivify
it; this may be done continuously by causing a stream of the liquid
with the oxide suspended in it to flow from the purifier to be brought
into contact with the air and to flow back into the purifier. It is
proposed to effect this circulation and aeration by pumping through
suction and discharge pipes of considerable length, in the course of
which chambers of larger diameter may be interpolated, the liquid with
its suspended oxide now partially converted into sulphide and atmo-
spheric air. The discharge pipe passes to the bottom of a tank, whence
the liquid flows back to the purifier. Into this tank runs also a small
quantity of solution of persulphate of iron, which is decomposed by the
ammonia extracted by the liquid from the gas, forming sulphate of
ammonia and oxide of iron. This solution of persulphate of iron is one
of the products of the following process, which is applied to portions of
the liquid withdrawn at intervals from the purifier. The liquid is
allowed to stand until it has separated into two layers, the upper con-
sisting of a solution of sulphate of ammonia, the lower of a mixture
of oxide of iron and sulphur. The upper layer is withdrawn and
evaporated, yielding sulphate of ammonia. The lower layer is to be
mixed with sulphuric acid; the mixture heated and allowed to stand.
The residue which remains undissolved consists of sulphur; the liquid is
a solution of persulphate of iron.

page_text: In order to make the Invention more complete it is proposed to
combine the purification process with that of converting the ammoniacal
liquor into sulphate of ammonia by blowing air first through the heated
ammoniacal liquor, thence through the purifying liquid, and thence into
a scrubber, where the ammonia which has not been taken up by the
purifying liquid may be fixed by dilute sulphuric acid. By these means
a continuous round of purification and revivification is kept up, and
although it may be necessary to pass the gas through a second purifier
of the same description, or subsequently through a dry oxide purifier,
or a lime purifier, or both in addition, so ready and effectual a means is
afforded for removing sulphuretted hydrogen and ammonia from gas and
converting these substances into a form in which they are commercially
valuable as to constitute a great improvement upon the processes now
in use.
It will be observed that no particular form of apparatus is relied upon
in either of the processes before described for effecting the object in
view, but any convenient form may be adopted.