IMPROVED MODE OF AND APPARATUS FOR PURIFYING GAS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John Clark and Frank William Clark
at the Office of the Commissioners of Patents on the 22nd June 1877.
JOHN CLARK, of King's Cross, in the County of Middlesex, Civil Engineer, and
FRANK WILLIAM CLARK, of Clapton, in the same County, Civil Engineer.
IMPROVED MODE OF AND APPARATUS FOR PURIFYING GAS."
«AN
The object of our Invention is to purify coal gas by eliminating therefrom the
sulphur compounds contained therein. This object is now partially effected by
bringing the gas into contact with oxide of iron or some other chemical agent which
will take up the sulphuretted hydrogen contained therein, but there are other sul-
phur compounds, such as bisulphide of carbon, which cannot be so easily elimi-
nated, and which in fact have little or no affinity for the oxide of iron.
Considerable difficulty has been experienced in getting rid of the bisulphide of
carbon, and although the object may be effected as a laboratory experiment, no one
has yet succeeded practically upon a large scale in removing this impurity from the
gas. Bisulphide of carbon can be decomposed by subjecting it to a temperature of
about 500° Fahr., and attempts have been made to purify gas of this impurity by
means of heat. No practical process for doing so successfully on a large scale has,
however, hitherto been devised.
It is not necessary for us to explain in detail the reasons of these failures, but
they probably mainly arise from the difficulty of keeping up the temperature of a
large body of gas in a chamber of large dimensions.
We have found that by dividing the gas into streams of moderate depth or
thickness, and causing it to traverse long narrow passages which are heated
externally, the gas will be maintained for a sufficient length of time at such a
temperature that the bisulphide of carbon will be decomposed, and the sulphur of
the compound will combine with an equivalent of hydrogen, and will form sul-
phuretted hydrogen, while the carbon will be taken up by another portion of hydro-
gen, and will form carburetted hydrogen. The sulphuretted hydrogen thus formed
may then be easily removed from the gas by passing the same a second time
through the oxide of iron purifier.
In carrying into effect our improved mode of purifying coal gas, we cause the gas
(after it has passed through the oxide of iron, or other purifier, for the purpose of

page_text: removing the sulphuretted hydrogen then existing in the gas) to pass into a
series of pipes enclosed in a hot air chamber, and arranged for convenience in a
serpentine form so as to obtain a great length of passage, and consequently a large
extent of heating surface within a limited space. This chamber is heated by fire-
places arranged below, and the heated gases from these fire-places are conducted
into the hot-air chamber, and impart heat to the gas pipes placed therein. By this
means the gas, while passing along the long narrow channels, is heated to the
proper point, and the bisulphide of carbon is thereby decomposed. We find it con-
venient to suck the gas through the apparatus by means of an exhauster so as to
prevent any gas from leaking into the hot-air chamber. Sometimes we charge, or
partially charge, the gas channels or passages with coke or charcoal for the purpose
of dividing or separating the gas into thin streams in order that it may be more
effectually acted on by the heat.
When the gas has been passed through the apparatus it is conducted to a second
oxide of iron purifier which will take up and remove from the gas any sulphuretted
hydrogen that may have been formed by the decomposition of the bisulphide of
carbon.
We prefer to construct the channels (for the passage of the gas through the
heating apparatus) of iron pipes as these may be easily kept gas-tight, and there
will be less risk of leakage, but the gas channels may be. constructed of tiles made
of fire-clay or other suitable material, and instead of being circular or cylindrical,
they may be made in the form of flat, wide, but shallow passages, so that the gas
will be spread out in a stream of moderate depth.