IMPROVEMENTS IN THE MEANS AND PROCESS FOR PURIFYING COAL GAS."
Year: 1881

page_text: LETTERS PATENT to John Greaves Hawkins, of Wigan, in the County of
Lancaster, for an Invention of "IMPROVEMENTS IN THE MEANS AND PROCESS
FOR PURIFYING COAL GAS."
PROVISIONAL SPECIFICATION left by the said John Greaves Hawkins at the
Office of the Commissioners of Patents on the 29th June 1881.
JOHN GREAVES HAWKINS, of Wigan, in the County of Lancaster. " IMPROVE-
MENTS IN THE MEANS AND PROCESS FOR PURIFYING COAL GAS."
In the ordinary method of purifying coal gas by means of oxide of iron, it is well
known that the oxide has at frequent intervals to be removed from the purifiers
and exposed to the air so as to revivify it, as it is called, or render it capable of
acting again in the purifiers, and this entails considerable nuisance. To reduce
these results atmospheric air has at times been drawn in along with the gas through
the purifying material so as to effect the revivification in the purifiers, but
atmospheric air alone so drawn in dilutes the gas, lowers its illuminating power,
and becomes dangerous.
The object of this Invention is to produce a continuous revivification in the
purifiers without injuriously affecting the quality of the gas.
In carrying out the Invention I cause a carefully regulated quantity of
atmospheric air to be forced or drawn in along with the gas through the purifiers,
the air having been by any suitable apparatus and means brought into such
intimate contact with the tar produced in the manufacture or with the lighter
portions thereof, that it may become saturated with the more volatile hydrocarbons
contained therein, and thus add to the bulk of the gas produced without
deteriorating its illuminating power or rendering the process dangerous, as is
usually the case when air is drawn in with the gas without such previous treatment.
In this way by a comparitively small quantity of air carefully regulated and

page_text: continuously introduced the oxide is constantly revivified, and so gradually that no
excessive rise in temperature can possibly take place, the sulphur does not become
fused, nor the grids of the purifiers damaged, and the deposit of sulphur takes
place so evenly through the mass of purifying material that no appreciable increase
of pressure is required to force the gas through it, although the process is continued
without removal of the oxide from the purifier until it is completely saturated
with sulphur. The air thus introduced may be taken in at the ordinary
atmospheric temperature, or it may be heated to any degree below which the
heavy hydrocarbons from the tar would be volatilized. The minimum quantity of
air to be introduced under this Invention is that absolutely required to revivify
the oxide of iron.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Greaves Hawkins in the Great Seal Patent Office on the
28th December 1881.
JOHN GREAVES HAWKINS, of Wigan, in the County of Lancaster. "IMPROVE-
MENTS IN THE MEANS AND PROCESS FOR PURIFYING COAL GAS."
In the ordinary method of purifying coal gas by means of oxide of iron it is well
known that the oxide has at frequent intervals to be removed from the purifiers
and exposed to the air so as to revivify it, as it is called, or render it capable of.
acting again in the purifiers, and this entails considerable labour and expense,
together with the loss of gas and considerable nuisance. To reduce these results,
atmospheric air has at times been drawn or forced in along with the gas through
the purifying material so as to effect the revivification in the purifiers, but
atmospheric air alone so drawn in dilutes the gas, lowers its illuminating power,.
and becomes dangerous.
The object of this Invention is to produce a continuous revivification of the oxide
in the purifiers, and so reduce the trouble and cost of purification without
injuriously affecting the quality of the gas.
The Invention consists in causing a carefully regulated quantity of atmospheric
air to enter an apparatus, chamber, or vessel wherein the tar, or the lighter portions
thereof, resulting from the carbonization of coal, is subjected to a temperature of
about 170 degrees Fahrenheit, so as to eliminate the volatile hydrocarbons. The
air thus introduced may be taken in at the ordinary atmospheric temperature, or it
may be heated to any degree below which the heavy hydrocarbons from the tar
would be volatilized. The air in passing through the apparatus becomes charged
with some of the light hydrocarbons, and this mixture is delivered into the main
conveying the gas from the retorts immediately after the outlet of the scrubbers,
so as to ensure the carburated air mixing uniformly with the gas before entering
the oxide purifiers.
It is to be understood that to carry out this arrangement it is necessary to force
the air into the gas by means of a suitable machine [such as an exhauster, for
instance] by which the quantity of air may be also regulated at will. The
minimum quantity of air to be introduced is that absolutely required to revivify
the oxide of iron. I find that in order that the process may be carried out in such a
manner as to prevent the presence of free oxygen in the purified gas, there must be
a sufficiently large area of oxide purifiers to allow the gas to pass slowly through
them and so ensure the revivification of the oxide going on gradually and
continuously, as where this is not the case the revivification is not complete and
the oxygen of the air is not completely removed, but goes on with the gas and
diminishes its illuminating power. But when the process is carried on as I have
described, the oxygen combines with the iron, the revivification goes on continuously,
and the heat never rises in the purifiers sufficiently to fuse or partly fuse the
sulphur. There is therefore no clogging of the material in the purifier and
consequent increase of pressure, and the process of revivification may be continued
without the removal of the oxide from the purifiers until the oxide is practically
saturated with sulphur.
When lime purifiers are used to eliminate sulphur compounds other than
sulphuretted hydrogen, I prefer to introduce the carburated air immediately after
the outlet of such lime purifiers and before the oxide of iron purifiers, and to ensure
the uniform mixing of the carburated air with the gas before entering the oxide
purifiers, it is advisable to have a considerable length of main between the two
sets of purifiers, or the gas may be caused to flow through a suitable vessel in
which the mixture may take place.

page_text: The drawing or forcing of atmospheric air through oxide of iron while in the
purifiers in order to revivify it is old, but the drawing or forcing of carburated air
either at the ordinary atmospheric temperature or artificially heated, for this
purpose is new, and is such an improvement that the gas is increased in bulk, the
illuminating power is not. diminished, the trouble and expense of the frequent
removal of the oxide from the purifiers are reduced, and the danger arising from
the oxide becoming unduly heated is reduced to a minimum.
Having now described and particularly set forth the nature of this Inven-
tion, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that I do not confine or restrict myself
to the precise details or arrangements that I have described or referred to, as
variations may be made therefrom without deviating from the principles or main
features of this Invention; but what I consider to be novel and original, and
therefore claim as the Invention secured to me by the hereinbefore in part recited
Letters Patent is,―
The introduction at a suitable point or points in the manufacture of illuminating
coal gas of carburated atmospheric air, either at the normal temperature of the
atmosphere, or at a suitably increased température, for the purposes herein set
forth, and in the manner herein described.
In witness whereof, I, the said John Greaves Hawkins, have hereunto set my
hand and seal, this Twenty seventh day of December, in the year of our
Lord One thousand cight hundred and eighty-one."
JOHN GREAVES HAWKINS. (L.S.)