AN IMPROVED PROCESS OR METHOD OF PURIFYING GAS
Year: 1877

page_text: LETTERS PATENT to William Marriott, of Huddersfield, in the County of
York, Manufacturing Chemist, for the Invention of "AN IMPROVED PROCESS
OR METHOD OF PURIFYING GAS."
Sealed the 18th December 1877, and dated the 30th August 1877.
PROVISIONAL SPECIFICATION left by the said William Marriott at the
Office of the Commissioners of Patents on the 30th August 1877.
WILLIAM MARRIOTT, of Huddersfield, in the County of York, Manufacturing
Chemist. AN IMPROVED PROCESS OR METHOD OF PURIFYING GAS."
My Invention relates to a novel process or method of purifying coal gas, and
its object is the removal or separation therefrom of those sulphur compounds,
generally called other sulphur compounds, which are not separated or eliminated
from the gas by the methods or processes in use, for the separation or removal
of sulphuretted hydrogen; the nature or character of these sulphur compounds,
which it is the object of my Invention to separate from the gas, is not clearly
defined, but their presence in the gas has a very deleterious influence thereon,
and therefore their removal is very desirable.
The only practicable process now in use to reduce these indefinite sulphur
compounds to the prescribed quantity or proportion, is that in which the gas is
passed through foul lime, that is to say, lime containing sulphide of calcium.
This process partially removes or reduces these sulphur compounds, but the
removal of the foul lime necessary for this purpose is a great nuisance in the
neighborhood of the gas works, and adds considerably to the cost of purification.
But by my improved method or process I effect the purification of the gas with-
out causing any nuisance, and separate or eliminate therefrom a greater portion
of the sulphur compounds than has heretofore been practicable.
My improved process or method is carried into practise as follows, that is to
Bay: I free the gas from these sulphur compounds by scrubbing it with a
solution of a caustic alkali, such as soda, potash, or ammonia, or sulphide of
soda, potash, or ammonia, or alkaline earth, such as lime, magnesia, or baryta,
or sulphides of these alkaline earths. I may use either of these substances
Prid

page_text: separately, or any of them combined, but of these substances the soda or lime
is preferable. The said alkali or alkaline earth or alkaline sulphide is dissolved
in water with as much sulphur as it will take up at a boiling temperature.
When the solution is cold and settled it is ready for use.
I may employ in this process the ordinary scrubbers now used in gas works or
any other suitable apparatus.
When the said solution, after being in use some time, will not remove or
eliminate from the gas any more of the sulphur compounds contained in the
same the solution can be re-converted or restored to an active state by re-boiling
it with a small quantity of lime.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Mariott in the Great Seal Patent Office on the 23rd
February 1878.
WILLIAM MARRIOTT, of Huddersfield, in the County of York, Manufacturing
Chemist. "AN IMPROVED PROCESS OR METHOD OF PURIFYING GAS."
*
My Invention relates to a novel process or method of purifying coal gas, and
its object is the removal or separation therefrom of those sulphur compounds
generally known as and herein-after termed other sulphur compounds," which
are not separated or eliminated from the gas by the methods or processes in
use for the separation or removal of sulphuretted hydrogen; the nature or
character of these other sulphur compounds," which it is the object of my
Invention to separate from the gas, is not positively known or clearly defined,
but their presence in the gas has a very deleterious influence or effect, and
therefore their removal is very desirable.
*
The only practicable process now in use to reduce these indefinite sulphur
compounds to the prescribed quantity or proportion is that in which the gas is
passed through foul lime, that is to say, lime containing sulphide of calcium.
This process partially removes or reduces these sulphur compounds, but the
removal of the foul lime necessary for this purpose is a great nuisance in the
neighborhood of the gas works, and adds considerably to the cost of purification.
But by my improved method or process I effect without creating any nuisance the
purification of the gas, and separate or eliminate therefrom a greater portion
of the sulphur compounds, other than sulphuretted hydrogen, namely, the_80
called other sulphur compounds" than has heretofore been practicable. For
this purpose I use a solution or solutions made as follows, that is to say:-I take
any of the alkalies, such as soda, potash, or ammonia, or the alkaline earths,
such as lime, magnesia, or baryta, or the sulphides of sodium, potassium,
ammonia, calcium, magnesium, or barium. I convert either or any of these
substances into polysulphides by boiling them in water with an excess of sulphur
until all the alkali or alkaline earth is dissolved and sulphur alone remains.
I wish it understood that I use the name polysulphides to indicate all those
soluble sulphides which contain more equivalents of sulphur than of the base
combined therewith.

page_text: As some of the above-named substances are more costly than others, and as
the treatment of some of them in the apparatus now in use in gas works would
be attended with practical difficulties, I give the preference to soda or sulphide
of solium as being the least difficult in its manipulation in scrubbing the gas. I
have therefore in the following description of my process specified the use of
caustic soda or sulphide of sodium, but the same process may be carried into
effect with any of the other above-named substances and by the employment of
the same apparatus. I use a cylindrical boiler, arranged horizontally, with a
shaft extending centrally throughout the length of the said boiler. To this shaft
arms are attached to keep the materials in the boiler well agitated. The said
boiler may either be heated directly by a fire or by high-pressure steam:
The said apparatus may be made of any suitable and convenient size and
shape. I fill the boiler about half full of water, and when the water boils
introduce the caustic soda or sulphide of sodium. When these are dissolved and
the solution stands when hot at 15 degrees by Twaddle's hydrometer, I add
sulphur so broken up as not to impede the agitator, and continue the boiling as
long as any sulphur will dissolve, leaving an excess of sulphur. The solution
is then allowed to settle, and when cold is ready for use.
The solution so prepared, and which I term polysulphide solution stands when
cold at about 23 degrees Twaddle, but I do not confine myself to any particular
or precise strength of this solution, as I have found by experiment that the
same may be increased or diminished, according to the strength of the sulphur
compounds and carbonic acid. I use this solution for scrubbing the crude gas
in the same manner and in the same apparatus as now used in gas works to
separate the ammonia from coal gas.
Crude gas contains in addition to the illuminating gas sulphuretted hydrogen,
carbonic acid, ammonia, and bisulphide of carbon, the latter constituting the
chief element of what are generally called "other sulphur compounds." When
carbonic acid comes in contact with the said polysulphide solution, the carbonic
acid combines with the alkaline base, forming with soda, potash, or ammonia,
soluble carbonates, and with lime, magnesia, or baryta, insoluble carbonates.
These latter are precipitated along with the sulphur forming the polysulphide.
Not only is the polysulphide solution converted by the crude coal gas into a
carbonate, and sulphur deposited, but there is also formed in the solution a
considerable quantity of sulpho-cyanide when ammonia is present in the
but the polysulphide solution will remove the other sulphur compounds" if
all the ammonia be previously removed from the gas.
+6
gas,
When any quantity of the polysulphide solution becomes exhausted or ceases to
remove the "other sulphur compounds" from the coal gas, it is drawn off and a
fresh quantity of the solution is supplied in its place, that this operation will
be continuous with very slight cost for labour. If this polysulphide solution is
made from sulphide of sodium the exhausted solution consists principally of
carbonate of soda, sulpho-cyanide of ammonia, and suspended sulphur. All of
these substances may be recovered by any of the well-known means. The sulphur
which settles after being thrown on a filter may be used again to form the
polysulphide solution.
When caustic soda is used to make the polysulphide solution, one half of the
soda is converted into hyposulphite of soda, and this will be found in the
exhausted solution with the carbonates and sulphocyanides.
++
33
By using the polysulphides for separating the other sulphur compounds
and carbonic acid from coal gas, all nuisance is avoided, and the employment
of lime may be altogether dispensed with, oxide of iron alone being made to
separate the sulphuretted hydrogen.
Having thus fully described the said Invention and the manner of performing
the same, I wish it understood that I claim, in the purification of gas,-
First. The employment of the aforesaid polysulphides or polysulphide solution
or solutions for the removal of the sulphur compounds herein specified as
other sulphur compounds" and carbonic acid from the gas, as above set forth.

page_text: Second. The recovery of the soda, hyposulphite of soda, sulphocyanide of
ammonium, or sulphur resulting from the use of the polysulphides, as above set
forth.
In witness whereof, I, the said William Marriott, have hereunto set my
hand and seal, this Twentieth day of February, in the year of our Lord
One thousand eight hundred and seventy-eight.
WILLIAM MARRIOTT. (L.S.)