Improvements in and relating to the Purification of Coal Gas.
Year: 1899

page_text: Date of Application, 3rd Feb., 1899
Complete Specification Loft 2nd Nov 4000
.חו.00
1000
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Purification of Coal Gas.
I, ARTHUR MCDOUGALL, of 1, Egerton Road, Fallowfield, in the County of
Lancaster, Corn Merchant, do hereby declare the nature of this invention to be
as follows:
This invention relates to the purification of coal gas and its object is to provide
a continuous process for such purification simultaneously with the recovery of
certain by-products and their utilization.
In the removal of sulphur compounds from coal gas it is usual to use dry
purifiers which require frequent filling and emptying and therefore cause a con-
siderable expenditure through increased labour and loss of gas. The present in-
vention consists generally in using certain solutions (which may be acidified or
not) of the persalts of iron, manganese, or chromium, or of mixtures of these
metals, in wet scrubbers. On these solutions coming in contact with the foul coal
gas in the scrubbers tower or apparatus for similar purpose, chemical re-actions
ensue whereby free sulphur is precipitated and simultaneously the persalt solutions
are converted to proto-salt solutions. The free sulphur can be removed from the
liquid by settling or filtration.
The present invention further consists in taking the proto-salt solutions and
oxidizing them to persalt solutions again by electrolysis. When a suitable
current is employed, reactions ensue with the result that hydrogen is given off
at the cathode and at the anode the proto-salt solutions are oxidized to persalt
solutions again so that they may be again available for use in the manner here-
inbefore described, the process being continuous. The hydrogen evolved may be
employed for lighting, heating, balloon, or motive power or other purposes.
A plant to carry the continuous process hereinbefore described into effect may
be arranged as follows. The wet scrubber has a suitable quantity of persalt
solution continuously pumped into it. This is continuously acted upon by the
foul gas and then drained off into a filtering tank where the sulphur is recovered
The solution has now become proto-salt and is allowed to flow into a closed in
electrolytic vat. Here it is acted upon in one or more compartments by a con-
tinuous current dynamo operated by any convenient motive power and sometimes
by a gas engine, and when converted into persalt solution again, then led to the
pump feeding the wet scrubber. The hydrogen is collected from the closed in
electrolytic vat and with air and a proportion of ordinary coal gas used to provide
the motive impulses for the gas engine when such motor is employed.
The applicant is well aware that persalts of iron, manganese, or chromium for
the removal of sulphur compounds from coal gas have been hitherto employed
and his invention is distinct from such reactions, as it consists in the continuous
purification by electrolysis substantially as herein before described.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, Birmingham, Agents.

page_text: Improvements in and relating to the Purification of Coal Gas.
I, ARTHUR MCDOUGALL, of 1, Egerton Road, Fallowfield, in the County of
Lancaster, Corn Merchant, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and as-
certained in and by the following statement:-
This invention relates to the purification of coal gas and its object is to provide
a continuous process for such purification simultaneously with the recovery of
certain bye-products and their utilisation.
In the removal of sulphur compounds from coal gas it is usual to employ dry
purifiers which require frequent filling and emptying and therefore cause a con-
siderable expenditure, through increased labor and loss of gas. The present in-
vention consists in using certain solutions (which may be acidified or not) of the
persalts of iron, manganese, or chromium, or of mixtures of solutions of these
metals in wet scrubbers. On these solutions coming into contact with the foul
coal gas in the scrubbers tower or apparatus for a similar purpose, chemical re-
actions ensue whereby free sulphur is precipitated and simultaneously the per-salt
solutions are converted to proto-salt solutions. The free sulphur can be removed
from the liquid by settling or filtration.
The present invention further consists in oxidising the proto-salt solutions to
per-salt solutions by electrolysis. When a suitable current is employed reactions
ensue with the result that hydrogen is given off at the kathode and at the anode
the protosalt solutions are oxidised to persalt solutions so that they may be again
available for use in the manner hereinbefore described, the process being con-
tinuous.
The hydrogen evolved may be employed for lighting, heating, balloon, or
motive power or other purposes.
Referring to the accompanying sheet of drawings which illustrate an arrange-
ment of plant constructed to carry into effect the continuous process hereinbefore
described.
Figure 1 is an elevation of the apparatus showing the condensing towers in
section, and
Figure 2 is a section of the electrolytic tank on the line of Figure 1.
The condensing towers or scrubbers A are fitted with cross boards B or other
suitable condensing packing and are connected in the gas main from the retorts
at the inlet and outlet pipes C and D, the upper part of the tower A being con-
nected to the lower part of its adjacent tower by a pipe E. An overhead tank F
adapted to contain the persalt solution is arranged, communicating by pipes G
with the top portion of each tower. The bottom of each tower is fitted with a
pipe H provided with a stopcock H¹ and communicating with a collecting tank I.
This tank communicates by a pipe J with a filter press K which in turn com-
municates by the pipe L with an electrolytic regenerating vat M. The electrolytic
vat consists of a closed-in vessel which is divided by porous partitions P (Figure 2)
into compartments N, O, adapted to contain the liquid to be regenerated. The
inner compartment N contains the anode Q which may consist of a plate or a
number of plates of platinised carbon or thin sheet of platinum or other suitable
material while the outer compartments contain the kathodes R which may
consist of sheets of lead or other suitable material. I find that both anode and
kathodes constructed of lead may be successfully employed. By properly regulat-
ing the current density in the cell the oxidation of the lead may be entirely
prevented. The current for the electrolytic vat is furnished by a suitable con-
tinuous current dynamo S connected to the terminals T, T¹, which connect with

page_text: the anode and kathode element respectively. The electrolytic vat is fitted with
a pipe U by means of which the liquid may be drawn off into a tank V, and a
pump W is provided for returning the regenerated liquid to the overhead tank F.
The operation of the apparatus arranged as above described is as follows:-
The tank F is filled with a solution (which may be acidified or not) of a persalt
of iron, manganese, or chromium, for example Ferric Chloride or Ferric Sulphate
The liquid flows by pipes G down through the scrubbers or condensers A where
it meets the stream of foul gas which passes into the scrubbers by the inlet
pipe C. Owing to the action of the sulphur compounds in the gas, the Ferric
Chloride or Sulphate solution becomes converted into a solution of the corre
sponding protosalt or Ferrous salt with precipitation of sulphur. The protosalt
solution carrying with it the sulphur thus formed passes by the pipes H into the
collecting tank L. Part of the sulphur may be recovered by settling in the
tank I, but the greater part of the sulphur is recovered from the filter press K
through which the protosalt solution passes, on its way to the electrolytic vat M.
The protosalt solution in the vat M under the action of the electric current is
oxidised to persalt solution at the anode with evolution of hydrogen at the
kathodes.
The hydrogen passes off by the pipe M¹ fitted into the cover of the electrolytic
vat and may be collected and mixed with air and a proportion of ordinary coal
gas to provide the motive power of a gas engine which may be employed to drive
the dynamo S.
The regenerated persalt solution which is formed in the electrolytic vat M is
drawn off from the vat by the pipe U into the collecting tank V from which it
is pumped by the pump W into the overhead tank F to be utilised again in
purifying the gas.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that I am
aware that solutions of per salt of iron, manganese or chromium have been
employed in the purification of coal gas and I do not claim the use of these
solutions per se but what I claim is:
1. In the purification of coal gas a continuous process for the removal of
sulphur compounds by the use of solutions of persalts of iron, manganese or
chromium or mixtures of solutions of persalts of these metals and the subsequent
regeneration of the persalt solutions by electrolysis substantially as hereinbefore
described.
2. In a continuous process for the removal compounds from coal gas by
solutions of persalts of iron, mangenese or chromium with subsequent electrolytic
regeneration of the persalt solution, the combination of a reservoir for the persalt
solutions condensers or scrubbers in which the gas and solutions are brought into
contact an electrolytic vat or vessel for the regeneration of the persalt solution
with means for returning the regenerated persalt solution to the reservoir, sub-
stantially as hereinbefore described.
3. In a process for the purification of coal gas by solutions of persalts of iron
manganese or chromium the regeneration of the persalt solutions by electrolysis
substantially as herein before described.
Tax of Vocambar 1809
MARKS & CLERK,
18, Southampton Buildings, London, W.C.