IMPROVEMENTS IN PURIFYING GAS PRODUCED FROM COAL, AND OBTAINING AMMONIACAL AND OTHER ALKALINE SALTS
Year: 1858

page_text: LETTERS PATENT to Thomas Greenshields, of No. 11, Little Titchfield
Street, London, for the Invention of "IMPROVEMENTS IN PURIFYING GAS
PRODUCED FROM COAL, AND OBTAINING AMMONIACAL AND OTHER ALKALINE
SALTS."
Sealed the 30th September 1858, and dated the 23rd April 1858.
PROVISIONAL SPECIFICATION left by the said Thomas Greenshields at
the Office of the Commissioners of Patents, with his Petition, on the
23rd April 1858.
I, THOMAS GREENSHIELDS, of No. 11, Little Titchfield Street, London, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
PURIFYING GAS PRODUCED FROM COAL, AND OBTAINING AMMONIACAL AND OTHER
ALKALINE SALTS," to be as follows:--
One part of the Invention consists in subjecting the impure gas to the
action of a saturated solution of caustic soda and caustic cream of lime, mixed
with suitable porous materials, by which action carbonic acid will be absorbed
by the lime, and sulphur by the caustic alkali. The gas is then to be subjected
to the action of the chloride of sodium and caustic cream of lime, mixed with
porous material; a reaction will take place, the ammonia will combine with
the chlorine and form muriate of ammonia, and any sulphur remaining will
combine with the sodium, forming sulphuret of sodium soluble in water, and
any carbonic acid will combine with the lime. The gas is then to be subjected
to the action of a suitable porous material saturated with sulphuric acid to
absorb moisture and any remaining ammonia. The gas may be subjected to

page_text: the action of the materials in what are termed dry purifiers, or by any other
suitable means.
Another part of the Invention is, when the porous materials are saturated
with the impurities removed from the gas, they are to be removed and treated
with water, the precipitated carbonate of lime removed, and the muriate of
ammonia and the sulphuret of sodium in solution subjected to known processes
to obtain muriate of ammonia, carbonate, or caustic soda, and sulphur, either
free or in combination.
Another part of the Invention is, that when the ammoniacal liquor obtained
from the condensers is to have chloride of sodium added to it, when a double
decomposition will take place, forming muriate of ammonia, and carbonate
and sulphuret of soda, that may be seperated by well-known means.
Another part of the Invention is, that when sulphate of ammonia is required,
the ammoniacal liquor is to have the equivalent of sulphate of lime in fine
powder put into it and well mixed, and allowed to remain some time, or until
decomposed; the carbonate of ammonia contained in the gas liquor will be
decomposed and converted into sulphate of ammonia, and there will remain in
the solution hydrosulphuret of ammonia. The solution when decomposed is to
be run into a close vessel, and dilute sulphuric acid is to be cautiously added
until sulphuretted hydrogen ceases to be given off. The sulphuretted hydrogen
is to be conducted by a pipe into a saturated solution of caustic alkali. The
sulphuretted hydrogen will be decomposed, and form sulphuret of sodium
soluble in water, and the hydrogen will be set free, and is to be conducted by
a pipe into water and absorbed; the sulphur is to be removed by well-known
means from the caustic alkali, and the alkali again used for decomposing
sulphuretted hydrogen, or for purifying gas. The sulphate of ammonia, when
deprived of the hydrosulphuret, is to be run into evaporating pans, and con-
verted by evaporation into crystals or salts of sulphate of ammonia.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Greenshields in the Great Seal Patent Office on the
23rd October 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
GREENSHIELDS, of No. 11, Little Titchfield Street, London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of April, in the year of our Lord One
thousand eight hundred and fifty-eight, in the twenty-first year of Her reign,

page_text: did, for Herself, Her heirs and successors, give and grant unto me, the
said Thomas Greenshields, Her special licence that I, the said Thomas Green-
shields, my executors, administrators, and assigns, or such others as I, the said
Thomas Greenshields, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
PURIFYING GAS PRODUCED FROM COAL, AND OBTAINING AMMONIACAL AND OTHER
ALKALINE SALTS," upon the condition (amongst others) that I, the said
Thomas Greenshields, my executors or administrators, by an instrument in
writing under my, or their, or one of their bands and seals, should par-
ticularly describe and ascertain the nature of the said Invention, and in what
manner the same was to be performed; and cause the same to be filed in the
Great Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Greenshields, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement:-
When the gas obtained from coal leaves the retorts, a portion of the
impurities which it contains will be removed by passing it through condensers,
when the gas leaves the condensers it has usually been found to contain as
impurities (but in variable proportions) ammonia in combination with other
elements, sulphur in combination with hydrogen; sulphur in combination with
carbon, and also carbonic acid. One part of my Invention has for its object
to seperate and remove from the gas the ammonia, sulphur, and carbonic acid,
either combined or uncombined with other elements. The most efficient mode
of effecting this object has been found to be, to make a solution or solutions
containing elements that would decompose or seperate the impurities from
their combinations, and combine with ammonia, sulphur, and carbonic acid,
and form new combinations with one or more of the elements contained in the
solution or solutions, and when combined that would be soluble and not
volatile, but become what is termed fixed. And by using an apparatus known
in gas works as "scrubbers," the ammonia, sulphur, and carbonic acid either
combined or uncombined would be seperated and removed from gas. Another
part of my Invention has for its object that the solution, or solutions, as well as
being efficient for the purpose of removing the impurities before referred to,
should-be used in a manner so as to obtain the new combinations in a form

page_text: best adapted for being manufactured into marketable articles in the most
economical and profitable manner. Another part of my Invention has for its
object a process or processes for economically manufacturing from the
products obtained from the purification of gas, muriate of ammonia, carbonate
of soda, and other products. The solutions that have been found to answer
best for the object before referred to are prepared in the following manner :—
No. 1, a saturated solution of chloride of sodium made with water and
coarse grained salt (broad salt), or a strong natural brine from which salt is
made may be used as a solution No. 1. .
No. 2, a saturated solution of sulphate of soda, made in the first instance by
dissolving in water the residual sulphate of soda left from the process of making
muriatic acid, or the residual sulphate of soda obtained or recovered from the
manufacturing processes herein-after described, or any other cheap residual
sulphate of soda may be used for the purpose of making the solution, or
supplying the deficiency caused by waste in using the solution over again,
sulphate of soda having the property of lowering the temperature of water
when mixed with it. It will be desirable in winter to make the soution with
warm water, that will give the solution of the required temperature, but using
the same quantity of sulphate of soda as was used with cold water.
No. 3, a strong solution of caustic alkali, made by dissolving in water an
hydrated alkaline. metallic oxyde, as the hydrated metallic oxyde of potash,
soda, &c., but it is preferred to use the hydrated oxyde of soda (caustic
alkali) as being more economical, and prepared by dissolving in water the
carbonate of soda of commerce (or the carbonate of soda obtained from the
manufacturing processes, herein after described) and depriving it of carbonic
acid by means of caustic lime, a process well understood; the solution to be
made of the specific gravity of 1.150.
For the purpose of purification only from the impurities in gas before referred
to, the three solutions, or the solutions No. 2 and No. 3 may be mixed in their
equivalent or other proportions that will combine with the estimated amount of
impurity in the gas, and used in a "scrubber" or "scrubbers," and the gas passed
through until the impurities are removed, to be ascertained by the usual tests.
After the solution has passed through the "scrubber or "scrubbers," it is to
be received into a suitable receptacle or vessel, and used again until it will not
deprive the gas of the impurities, as ascertained by the usual tests, when the
products obtained from the purification may be seperated by known means, or the
three solutions or the solutions No. 2 and No. 3 may be mixed in their equivalent
or other proportions that will combine with the estimated impurity in the gas,
and absorbed into porous materials, and when so prepared may be used in

page_text: what are known in gas works as "dry lime" or similar description of purifiers,
and the gas passed through until deprived of the impurities, ascertained by the
usual tests. When the solution in the porous materials has become inert, the
spent solution may be washed out by any convenient means, and fresh solution
added, and the solution washed out may be treated by known means to seperate
the products obtained; but it is preferred to use the solution in "scrubbers"
as being more efficient and not requiring so much pressure to force the gas
through the purifying media as when absorbent materials and "dry" or similar
description of purifiers are used. The mode of proceeding that has been
found to answer best to effect the removal of the impurities herein-before
referred to, and to obtain the new combinations that are most suitable for
being economically manufactured into marketable articles, is, that when the
gas leaves the condensers, it is to be passed through a "scrubber" or
"scrubbers," supplied with the solution No. 2 (sulphate of soda) until deprived
of ammonia, ascertained by the usual tests; when deprived of ammonia it is
then to be passed through a "scrubber" or "scrubbers" supplied with the
solution No. 3 (caustic alkali) until deprived of sulphur and carbonic acid,
ascertained by the usual tests. When deprived of sulphur and carbonic acid,
the gas may be conveyed into the gasholder for use; but before being con-
veyed into the gasholder (gasometer) it would be improved for lighting
purposes if it was deprived of moisture by passing through or over sulphuric
acid, caustic lime, or by any convenient or known means of depriving gas
of moisture. When a large quantity of gas has to be purified, it is desirable
that two or more "scrubbers" for each solution should be used. Assuming
that two "scrubbers" are used for the sulphate of soda, solution No. 2, and
that the "scrubbers" are numbered No. 1 and No. 2, the foul gas from the
condensers is first to be passed through No. 1 "scrubber," and then through the
scrubber No. 2. The whole of the solution will not be decomposed by.
passing once through the "scrubber;" after it has passed once or twice through
No. 2, it is then to be used in No. 1 scrubber, (No. 2 being supplied with
fresh solution,) until it is decomposed or will not deprive the gas of ammonia,
ascertained by the usual test; when decomposed it is to be run into a suitable
covered vessel, and will usually contain sulphate of ammonia, carbonate of
soda, sulphuret of sodium, a small quantity of sulphuretted hydrogen, and
sulphate of soda and cyanogen; the sulution to be treated as herein-after
described. Assuming that two "scrubbers" are also used for the caustic
alkali solution No. 3, it is to be treated in every respect as described for the
sulphate of soda, solution No. 2, until the solution will not deprive the gas of
sulphur and carbonic acid (ascertained by the usual tests); it is then to be run

page_text: into a suitable covered vessel (to be treated as herein-after described), and will
usually contain sulphuret of sodiuni, carbonate of soda, some cyanogen, and
sulphite of soda. The number and size of the "scrubbers," and the quantity
of the solution to be used, will depend on the quantity and quality of the gas
to be purified, and the number of parts the whole body of gas may be divided
into, but the known quantity of gas made and the amount of impurities ordinarily
existing in gas obtained from a given quantity and quality of coal, will furnish
the means of estimating the number and size of the "scrubbers," and the
quantity of the solutions that will contain the equivalents that will combine
with the impurities; but it is preferred to use the solutions considerably
in excess of the equivalents estimated; as the impurities become what is
termed fixed in the solution, it can without injury to the gas be passed
many times through the "scrubber," or until decomposed, or a saturated or
nearly a saturated solution obtained. The process or processes that have
been found to answer best for manufacturing articles from the products
obtained from the purification by means of the condensers, by the sulphate
of soda solution No. 2, and by the caustic alkali solution No. 3, used in seperate
"scrubbers" as before described, is as follows:-A known quantity of the
"ammoniacal water" from the condensers is to be placed in an evaporating
pan, and the quantity of ammonia it contains ascertained in the usual
manner by the test acid; having ascertained the quantity of ammonia, add the
equivalent of anhydrous, or crystalised sulphate of soda that will decompose
the ascertained quantity of ammonia. When dissolved, it is to be cautiously
mixed with the "ammoniacal water," and allowed to stand one or two hours
to decompose; when decomposed, the solution in the evaporating pan will
contain sulphate of ammonia, carbonate of soda, sulphuret of sodium, sul-
phuretted hydroden, and cyanogen; upon evaporating the solution the sulphate
of ammonia will separate, but it will be necessary to keep the cover of the
pan closed, and convey the sulphuretted hydrogen disengaged by a pipe to
a vessel containing some of the caustic alkali solution No. 3, into which it is
to be absorbed. When the whole of the sulphuretted hydrogen has been driven
off, the cover of the pan may be opened, and the sulphate of ammonia that
has separated may be removed; when the whole of the sulphate of ammonia
bas separated and been removed, the remaining solution may be evaporated to
a salt and removed to a suitable furnace, and the sulphur vaporised at a dull
red heat. When the whole of the sulphur has been driven off, the carbonic
and caustic soda may be drawn for sale, or crystalised, or made into pure
carbonate of soda. A known quantity by weight of the sulphate of ammonia
obtained during the last-described process is to be placed in an evaporating

page_text: pan and dissolved in rather more than twice its weight of cold water; when so
dissolved the quantity of the solution No. 1 containing the equivalent of
chloride of sodium that will decompose the sulphate of ammonia, is to be
added, and the solution well mixed; upon evaporating the solution, muriate of
ammonia will seperate and can be removed; when the whole of the muriate
of ammonia has seperated and been removed, the remaining sulution of
sulphate of soda (is to be evaporated (if required) to a saturated solution) to
be used as the sulphate of soda solution No. 2. Or, when the chloride of
sodium solution is added to the sulphate of ammonia solution, the solution
may be evaporated to a salt containing muriate of ammonia and sulphate of
soda, and the mixed salt dried and placed in a suitable apparatus, and the
muriate of ammonia sublimed (a process understood), and the residual sulphate
of soda used to decompose the "ammoniacal water" from the condensers as
before described. The sulphate of soda solution No. 2 after being used in the
"scrubber" until it becomes saturated or decomposed as before described, is
to be conveyed into an evaporating pan, and some "ammoniacal water" from
the condensers is to be added to decompose the sulphate of soda remaining in
the liquor, and then treated in every respect as described for the process
or processes for treating the "ammoniacal water" from the condensers (after
the addition of the sulphate of soda), that is to say, first seperate by evapo-
ration the sulphate of ammonia, then obtain the carbonate and caustic soda,
and then decompose the sulphate of ammonia, and obtain muriate of ammonia
and sulphate of soda, to be used again as sulphate of soda solution No. 2.
The caustic alkali selution No. 3 after being used in the "scrubber" until it
becomes saturated as herein-before described, is to be placed in a suitable
evaporating pan and evaporated to a salt, and when dry it is to be placed in a
suitable furnace or "burner" and vaporised, and the vapour conveyed to a
suitable receptacle for recovering the sulphur or the vapour from the "burner"
used for manufacturing sulphuric acid, and the remaining carbonate and
caustic soda may be used again to make the solution No. 3, herein-before
described. I do not confine myself to the precise details, or to the exact
strength or specific gravity of the solutions, or to the precise mode of com-
bining or using them, as any chemist practically acquanted with this depart-
ment of the arts will understand the variations which may be made without
departing from the principle for obtaining the results herein-before described.
Having now described the nature of my said Invention, and in what
manner the same is to be performed, I wish it to be understood that I do not
claim as new the use of salt for purifying gas or scrubbers, or absorbent
materials or quicklime, or dry or similar description of purifiers, or evapc-

page_text: rating pans, or the decomposition or vaporisation and recovering of substances,
or of the several processes as herein-before mentioned or referred to, except so
far as the same may be employed in and for the purposes of my said Invention,
and I hereby declare that I claim,-
First, the use of the solution formed by mixing the solution of chloride of
sodium No. 1, the solution of the sulphate of soda No. 2, and the solution of
an hydrated alkaline metallic oxyde No. 3 (caustic alkali), and using the
solution thus made in a "scrubber," or "scrubbers," or absorbed into porous
material, and used in a "dry" or similar description of purifiers, as herein-
'before described, for removing ammonia, sulphur, and carbonic acid from gas.
Secondly, I claim the use of the solution of sulphate of soda No. 2, and the
solution of an hydrated alkaline metallic oxyde No. 3 (caustic alkali), the
solution to be used seperately, in seperate "scrubbers," or seperately absorbed
into porous material, and used in seperate "dry" or similar description of
purifiers, or to be used by mixing the two solutions into one solution, and used
in a "scrubber" or scrubbers, or absorbed into porous material, and used
in "dry" or similar description of purifiers, as herein-before described, for
depriving gas of ammonia, sulphur, and carbonic acid.
Thirdly, I claim the use of sulphate of soda solution No. 2, in combination
with the process or processes herein-before described for manufacturing from
the products obtained from the purification, muriate of ammonia, carbonate of
soda, and recovering the sulphate of soda used, to be used again.
Fourthly, I claim the use of a caustic alkali in combination with the process
or processes before described for removing from gas, sulphur and carbonic
acid, and for obtaining the sulphur; or for manufacturing sulphuric acid, and
recovering the alkali, to be used again for removing sulphur and carbonic acid
from gas.
In witness whereof, I, the said Thomas Greenshields, have hereunto set
my hand and seal, this Twenty-first day of October, in the year of our
Lord One thousand eight hundred and fifty-eight.
Witness,
GEO. P. MORRELL.
THOMAS GREENSHIELDS. (L.S.)