Improvements in the Purification of Coal Gas.
Year: 1892

page_text: Date of Application, 5th Sept., 1892
Complete Specification Left, 5th July, 1893-Accepted, 5th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Purification of Coal Gas.
We, JOHN JAMES HOOD, of 21 Shepherds Bush Road in the County of
Middlesex, and ALFRED GORDON SALAMON of 1 Fenchurch Avenue in the City
of London Analytical Chemists do hereby declare the nature of this invention to
be as follows:-
These improvements relate to the purification of coal gas.
The gaseous impurities to which this invention relates existing in coal gas are
3 in number. First carbonic acid. Second sulphuretted hydrogen. Third a class
of bodies known as sulpho compounds, the chief of which is carbon bisulphide.
Oxide of iron, or the manganiferous material known as Weldon mud, may be
employed for the removal of the sulphuretted hydrogen, but hydrated lime is
necessary for the removal of the carbonic acid, and sulphide of lime for the sulphur
compounds; or hydrated lime may be employed for the removal of all three
impurities.
The improvements herein claimed, relate to the employment of lime, in
conjunction with the manganiferous material known as Weldon mud, in such manner
as to render both these materials more effective in their several capacities, that is
to say, the former material or hydrated lime more active for the abstraction of
carbonic acid and sulphur compounds, and the Weldon mud for sulphurated
hydrogen.
In making our preliminary experiments we have been guided by the following
well-known facts :-
The material known as carbonate of lime, the ultimate product obtained by the
gas maker, by the action of the carbonic acid in gas upon hydrated lime, exists in
nature in two different forms, exhibiting essentially different physical properties,
and are known as calcite and arragonite. These two distinct forms of carbonate of
lime, may be prepared artificially, the former by precipitation from a cold and the
latter from a hot solution. Sulphide of lime likewise exhibits different physical
properties according to the temperature at which it is prepared. It has been long
known that if sulphide of lime be prepared with pure sulphuretted hydrogen, it is
much more active in abstracting sulphur compounds, and carbon bisulphide, than if
the sulphide of lime is prepared or fouled, as is usually done in gas works with the
sulphuretted hydrogen contained in the coal gas. This fact however, has nothing
to do with the parity of the sulphuretted hydrogen employed.
Now we have found that if freshly slaked lime in a hot state whether the heat
be produced by chemical action of moisture or by other means be employed for
absorbing the carbonic acid in coal gas, this material will pass more than twice the
volume of gas that cold slaked lime, as employed at the present time in gas works,
will do, before showing traces of carbonic acid passing. Thus showing a much
greater activity of the hot lime over the cold lime for absorbing the carbonic acid.
And the tendency is probably, under the hot conditions, to form arragonite instead
of calcite, as above indicated.
Our experiments have also shown that the sulphide of lime formed simultaneously
with the carbonate, in the first stage of the purification, is of a less stable character,
when the lime is employed hot, than when it is used cold. In other words the
sulphuretted hydrogen gas, like carbonic acid, is absorbed more readily by hot than
by cold lime, but the carbonic acid displaces it from the sulphide of lime more
readily in a hot state than in the cold, and thus the sulphuretted hydrogen is sent
forward in a large burst by the carbonic acid, as the lime becomes fouled.
.
Our experiments have also shown us, that if hot lime be employed for the

page_text: preparation of sulphide of lime, the material thus formed is extremely active in
absorbing sulphur compounds and that if the active form of lime thus prepared is
chilled or cooled, it loses much of its activity, but if again warmed, its absorbing
power for the sulphur compounds returns to a greater or less degree. But we
prefer to maintain the temperature of the vessel warmed in the manner indicated
below.
Our object, therefore, is to utilize the properties above stated for the more
efficient purification of coal gas in the following manner.
First. As regards carbonic acid. We deposit the hydrated slaked lime hot, into
the purification vessels or deposit the lime in such vessel unhydrated or partly
hydrated in lump or in the form of ground lime and complete the hydration process
by means of water or steam or by both and further maintain the heat by any
suitable means, as by the introduction of steam with the crude gas, or by warming
a portion of the gas. By so doing we allow less of the carbonic acid to slip
through the vessel than is usual with cold lime. We also accumulate a larger
burst of sulphuretted hydrogen which is sent forward, either to form a hot sulphide
of lime for absorbing the sulphur compounds or to be absorbed in Weldon mud or
oxide of iron.
Secondly. We introduce the slaked lime that is intended for the formation of
sulphide of lime hot into the vessels or prepared by the means previously described,
at such a time as the former vessel known as the carbonate vessel is becoming foul,
and thus we collect the burst of sulphuretted hydrogen driven out by the carbonic
acid from the first vessel into the hot lime, so as to form a very active sulphide
vessel.
The temperature of this sulphide of lime vessel, which has been prepared with
hot lime, in the manner described is maintained warm by the gas passing through
the first vessel known as the carbonate vessel, and which has been formed by the
employment of hot lime, or by the introduction of steam with the gas at inlet or
by warming a portion of the gas.
Thirdly. Weldon mud or oxide of iron, by preference the former, is employed
for absorbing the sulphuretted hydrogen, and with the warm gas, and the
introduction of a small percentage of air, the activity of this material for
absorbing sulphuretted hydrogen, is very much increased over that when the
material is employed cold.
We further find that when the line is hot as aforesaid, the action as between
ammonia, which may be present in the gas in small quantities, carbon bisulphide
and lime, resulting in the formation of sulphocyanide of lime, is greatly accelerated
and in this way the duty of the lime over carbon bisulphide is increased.
Dated this 5th day of September 1892.
ERNEST
SALAMAN,
61 & 62, Chancery Lane, London, Agent for Applicants.
COMPLETE SPECIFICATION.
Improvements in the Purification of Coal Gas.
We JOHN JAMES HOOD of 21 Shepherds Bush Road in the County of Middlesex
and ALFRED GORDON SALAMON of 1 Fenchurch Avenue in the City of London 4
Analytical Chemists do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
These improvements relate to the purification of coal gas.
The gaseous impurities to which this invention relate existing in coal gas are 5
three in number. First carbonic acid. Second sulphuretted hydrogen. Third a class
of bodies known as sulphur compounds, the chief of which is carbon bisulphide.
Oxide of iron, or the manganiferous material known as Weldon mud may be

page_text: employed for the removal of the sulphuretted hydrogen but hydrated lime is
necessary for the removal of the carbonic acid, and sulphide of lime for the sulphur
compounds; or hydrated lime may be employed for the removal of all three
impurities.
The improvements herein claimed, relate to the employment of lime in such
manner as to render this material more effective in the abstraction of carbonic acid
and sulphur compounds.
In making our experiments we have been guided by the following well known
facts.
The material known as carbonate of lime the ultimate product obtained by the
gas maker, by the action of the carbonic acid in gas upon hydrated lime, exists in
nature in two different forms, exhibiting essentially different physical properties,
and are known as calcite and arragonite. These two distinct forms of carbonate
of lime, may be prepared artificially the former by precipitation from a cold and
the latter from a hot solution. Sulphide of lime likewise exhibits different physical
properties according to the temperature at which it is prepared. It has been long
known that if sulphide of lime be prepared with pure sulphuretted hydrogen it is
much more active in abstracting sulphur compounds and carbon bisulphide than if
the sulphide of lime is prepared or fouled as is usually done in gas works with the
sulphuretted hydrogen contained in the coal gas. This fact however has nothing
to do with the purity of the sulphuretted hydrogen employed. Now we have
found that if freshly slaked lime in a hot state, whether the heat be produced by
chemical action of moisture or by other means, be employed for absorbing the
carbonic acid in coal gas, this material will pass a greater volume of gas than cold
slaked lime, as employed at the present time in gas works, before shewing traces
of carbonic acid passing, thus shewing a much greater activity of the hot lime
over the cold lime for absorbing the carbonic acid. And the tendency is under
the hot conditions to form arragonite instead of calcite, as above indicated.
Our experiments have also shown that the sulphide of lime formed in the first
stage of the purification by lime, is of a less stable character, when the line is
employed hot than when it is used cold, in other words, the sulphuretted hydrogen
gas, like carbonic acid is absorbed more readily by hot than by cold lime, but the
carbonic acid displaces it from the sulphide of lime more readily in a hot state
than in the cold, and thus the sulphuretted hydrogen is sent forward in a large
burst by the carbonic acid, as the lime becomes fouled.
Our experiments have also shewn that if hot lime be employed for the preparation
of sulphide of lime, the material thus formed is extreinely active in absorbing
sulphur compounds and that if the active form of lime thus prepared is chilled or
cooled, it loses much of its activity, but if again warmed, its absorbing power, for
the sulphur compounds returns to a greater or less degree. But we prefer to
maintain the temperature of the vessel warmed in the manner indicated below.
Our object, therefore, is to utilize the properties above stated for the more
efficient purification of coal gas in the following manner.
First. As regards carbonic acid. We deposit the hydrated slaked lime hot into
the purification vessels or deposit the lime in such vessel unhydrated or partly
hydrated in lump or in the form of ground lime and complete the hydration process
by means of water or steam or by both and further maintain the heat by any
suitable means, as by the introduction of steam with the crude gas, or by warming
a portion of the gas. By so doing we allow less of the carbonic acid to slip through
the vessel than is usual in cold lime. We also accumulate a longer continued
stream of sulphuretted hydrogen free from carbonic acid which is sent forward
either to forin a hot sulphide of lime for absorbing the sulphur compounds or to be
absorbed in Weldon mud or oxide of iron.
Secondly. We introduce the slaked lime that is intended for the formation of
sulphide of lime, hot into the vessels or prepared by the means previously described,
at such a time as the former vessel known as the carbonate vessel is becoming
foul and thus we collect the burst of sulphuretted hydrogen driven out by the

page_text: carbonic acid from the first vessel into the hot lime so as to form a very active
sulphide vessel.
The temperature of this sulphide of lime vessel which has been prepared with
hot lime in the manner described is maintained warm by the gas passing through
the first vessel known as the carbonate vessel, and which has been formed by the
employment of hot lime, or by the introduction of steam with the gas at inlet or
by warming a portion of the gas.
If lime, alone be not employed Weldon mud or oxide of iron, by preference the
former, is employed for absorbing the sulphuretted hydrogen, and with the warm
gas and the introduction of a small percentage of air the activity of this material
for absorbing sulphuretted hydrogen is very much increased over that when the
material is employed cold.
We further find that when the lime is hot as aforesaid the action as between
ammonia, which may be present in the gas in small quantities, carbon bisulphide
and lime, resulting in the formation of sulpho cyanide of lime, is greatly accelerated
and in this way the duty of the lime over carbon bisulphide is increased.. In
connection with the removal of the last traces of ammonia from coal gas by means
of lime in the purifiers we also find that it is greatly assisted by adding to the
water employed to slake the lime a solution of calcium chloride. The strength of
this solution may vary so as to meet the variation of the ammonia in the gas, but
we have found that one tenth part by weight of solid calcium chloride on the
weight of water used in slaking is a convenient quantity. The employment of the
calcium chloride in this manner also tends to retain moisture in the hot slaked
lime when in the purifiers and this retention of moisture assists in the complete
retention of the carbonic acid gas by the lime.
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 purification of coal gas the employment of hot slaked lime in the manner
and for the purposes above described.
2. The employment of a solution of calcium chloride in the slaking of lime in
the manner and for the purposes described.
Dated this 5th day of July 1893.
ERNEST SALAMAN,
Pinners Hall, Great Winchester Street, E.C., Agent for Applicants.