IMPROVEMENTS IN PURIFYING GAS, PROVISIONAL SPECIFICATION
Year: 1859

page_text: LETTERS PATENT to Thomas Greenshields, of No. 11, Little Titchfield
Street, London, for the Invention of "IMPROVEMENTS IN PURIFYING GAS,
PROVISIONAL SPECIFICATION left by the said Thomas Greenshields at
the Office of the Commissioners of Patents, with his Petition, on
the 10th June 1859.
I, THOMAS GREENSHIELDS, of No. 11, Little Titchfield Street, London, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN PURI-
FYING GAS, AND OBTAINING AMMONIACAL AND OTHER SALTS," to be as follows:-
The improvements consist in preparing and using a solution of chloride of
barium in a "scrubber" or other suitable apparatus, to deprive the foul gas of
ammonia and its combinations; the "ammoniacal liquor" obtained from the
condensers is to be decomposed either by distilling the liquor and condensing
the vapour in a solution of chloride of barium, or the chloride of barium
added to the "liquor;" upon using the solution of chloride of barium in the
"scrubber" or in the "liquor," a decomposition will be effected, carbonate of
baryta will precipitate, and chloride of ammonia will be in solution; the
solution is to be run from off the precipitate and evaporated to a salt, or
crystalised or sublimed. When making muriatic acid, a residual sulphate of.
soda is obtained, the sulphate of soda is to be made into a nearly saturated
solution, and by adding the carbonate of baryta obtained as before described
(or made into a caustic baryta), a sulphate of baryta will precipitate, and leave
in solution a carbonate of soda to be run from off the precipitate evaporated
to a salt, or crystalised. If the caustic baryta was added to the sulphate of
soda solution, sulphate of baryta would precipitate, and a caustic soda be left

page_text: in solution; the solution to be used in a "scrubber" to deprive gas of sulphur
and carbonic acid. When it will not further deprive gas of sulphur or carbonic
acid, it is to be evaporated to a salt, and the sulphur vaporised by heat in a
suitable apparatus, leaving a combined salt of carbonate and caustic soda as a
product. The sulphate of baryta that was precipitated is to be made into a
sulphuret of barium, and decomposed by dilute muriatic acid, when sulphur
will precipitate; the chloride of barium formed is to be run from off the
precipitate, and used to deprive gas of ammonia and its combinations.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Greenshields in the Great Seal Patent Office on
the 8th December 1859.
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 Tenth day of June, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Thomas Greenshields, Her special licence that I, the said Thomas
Greenshields, 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 there-
after 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 "IM-
PROVEMENTS IN PURIFYING GAS, AND OBTAINING AMMONIACAL AND OTHER 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 hands and seals, should particularly 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 per-
formed, 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

page_text: impurities that it contains will be removed by passing it through the con-
densers; when the gas leaves the condensers it has usually been found to
contain as impurities 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 an improved mode of seperating
and removing from the gas the ammonia, sulphur, and carbonic acid, whether
combined or uncombined with other elements. The most efficient practical
mode of effecting this object has been found to be to pass the gas through
"Scrubbers" supplied with a solution or solutions containing elements that
would decompose or seperate the impurities from their combinations, and
combine with the ammonia, sulphur, and carbonic acid, and form new com-
binations with one or more of the elements in the solution or solutions, and
when combined, that would be soluble and remain in the solution, and not be
volatile, but become what is termed fixed. By using "scrubbers" the purifi-
cation would be effected with the least amount of pressure, and it would be
continuous by means of a regular and sufficient supply of the purifying
solution or solutions.
Another part of my Invention has for its object an improved mode of
preparing the solutions, that, 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 best adapted for being manufactured
in the most economical and profitable manner into muriate of ammonia
(sal ammoniac), carbonate, or caustic soda, and other products. The solutions
that have been found to answer best are prepared in the following manner :—
I commence by preparing muriatic acid and sulphate of soda by decomposing
common salt (chloride of sodium) with sulphuric acid, a process well under-
stood. With the muriatic acid, prepared as before described, I decompose
sulphuret of barium (prepared as berein-after described), until a neutral
solution of chloride of barium is obtained, of the specific gravity of not less than
1-260; this solution, when run from off the precipitated sulphur, is to be called
the purifying solution No. 1. The decomposition is to be made in a close
vessel lined with lead, containing the sulphuret of barium solution; upon
adding the muriatic acid, sulphur will precipitate, and chloride of barium
remain in solution, and sulphuretted bydrogen be given off, to be conveyed by
a pipe and condensed in a suitable vessel containing caustic soda solution
No. 2, by this means all nuisance will be prevented. The chloride of barium
solution No. 1 is to be placed in a suitable vessel lined with lead, and
decomposed with the ammoniacal liquor obtained from the condensers, either

page_text: by adding the liquor to the chloride of barium solution, or as giving a purer
product, distilling the ammoniacal liquor (an operation well understood), and
condensing in the chloride of barium solution, and continue the operation
until the chloride of barium solution is decomposed (ascertained by the usual
tests); when the operation has been completed carbonate of barytes will pre-
cipitate, and chloride of ammonia remain in solution, to be run from off the
precipitate, evaporated to. a salt, crystalised, or sublimed, to obtain muriate of
ammonia (sal ammoniac). The precipitated carbonate of barytes, when
deprived of all muriate of ammonia by washing with water, is to be added to
a sulphate of soda solution (prepared by dissolving in water, in a suitable
vessel or pan, the sulphate of soda prepared as before described, in the pro-
portion of forty-two parts of dry sulphate of soda to one hundred parts of
water), in the proportion of one hundred parts of the precipitated carbonate of
barytes to seventy-two parts of dry sulphate of soda contained in the solution;
to be well mixed and boiled about two hours (occasionally well stirring). when
the sulphate of soda will be nearly decomposed (ascertained by the usual tests),
and converted into carbonate of soda in solution, and sulphate and undecom-
posed carbonate of barytes precipitate. If nearly decomposed it is preferred to
complete the decomposition of the sulphate of soda by adding anhydrous
caustic baryta (prepared as herein-after described) until the sulphate of soda
is decomposed, ascertained by adding chloride of barium solution to a small
portion; if no precipitate forms the decomposition is complete. In this part of
the process sulphate of barytes will precipitate and caustic soda remain in
solution, the solution is then carbonate and caustic soda, to be run from off
the precipitate and treated in the usual manner for manufacturing carbonate
of soda either as a salt or crystalised, as is well understood; or the solution
containing the carbonate and caustic soda may be made caustic by well known
means, and when made of the specific gravity of 1.125, will be the purifying
solution to be called No. 2, for removing sulphur from the gas; or the caustic
soda to form the purifying solution No. 2 may be made by adding to a sul-
phate of soda solution made with water at 90° Farenheit, and sulphate of
soda in the proportion of fifty parts of dry sulphate of soda to one hundred
parts of water, the solution to be kept at 90° Farenheit, and anhydrous
caustic baryta (prepared as herein-after described) added until the sulphate of
soda is decomposed, ascertained as before described. In this part of the
process sulphate of barytes will precipitate, and caustic soda remain in
solution, to be run from off the precipitate, and, made of the specific gravity
before described, will then be the purifying solution No. 2. The precipitated
carbonate of barytes, when deprived of all muriate of ammonia by washing

page_text: with water, may be used as before described for making carbonate of soda,
but in order to make caustic soda, the precipitated carbonate of barytes is to
be made into anhydrous caustic barytes by mixing it with about one-third of its
weight of coal or slack in fine powder, and well and intimately mixed and
placed in a suitable retort or furnace, and the mass made and kept at a bright
red heat for rather more than one hour, then drawn, and (if not immediately
used) kept in an air-tight vessel, and is the anhydrous caustic barytes before
referred to for decomposing sulphate of soda to make the purifying solution
No. 2.
A portion of the caustic barytes is to be drawn from the retort or
furnace, and dissolved in boiling water, and immediately filtered and kept in
air-tight vessels, and when cold the precipitated or crystalised barytes formed
on cooling is to be dissolved with water at 60° Farenheit to make the
whole into a saturated solution, and which is the purifying solution to be
called No. 3, to be used for depriving gas of carbonic acid. The precipitated
sulphate of barytes obtained by decomposing the sulphate of soda is to have
about one-third of its weight of fine coal or slack in fine powder added and
well mixed, and then placed in an iron or other suitable retort, and the mass
made and kept at a red heat for rather more than one hour, and then drawn
into hot water and filtered, and is then the sulphuret of barium solution
referred to for making chloride of barium solution, and obtaining precipitated
sulphur before described. Should the precipitated sulphate of barytes also
contain carbonate of barytes, the carbonate may be seperated by dilute
muriatic acid of the specific gravity of 1.061, by adding it cautiously until
effervescence ceases, the solution will then be chloride of barium (to be made
neutral if necessary), and sulphate of barytes will remain unaltered as a pre-
cipitate. For the purpose of effecting the purification, 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, but the known quantity of the
gas made, the amount of impurity ordinarily existing in gas obtained from. a
given quantity and quality of coal will furnish the means for estimating the
size and the number of "scrubbers," and the quantity of the solutions that will
contain the equivalents that will combine with the estimated impurities; but the
impurities being variable in quantity it would be advisable to have an extra
"scrubber" for each solution that would insure perfect purification should an
unusual quantity of either impurity have to be removed. The number of
"scrubbers" and perfect purification will also depend upon the gas in its rapid
passage (in some instances under twenty-seven seconds in each scrubber)
through the "scrubbers" being brought in contact with the purifying solution.
In the first place it is desirable to remove from the gas the ammonia and

page_text: carbonic acid, and the "scrubbers used for this purpose (the ordinary iron
"scrubbers") should be lined or cased on the inside with tiles of about one
inch in thickness, and made of "brown stoneware set in Portland cement;
the seal cup, exit pipe, and spreader should also be made of the same materials.
It is necessary to line the scrubbers to prevent the muriate of ammonia being
discoloured with an impurity of iron. For the purpose of removing the
ammonia and carbonic acid, I mix the solution No. 1 and the solution No. 3,
the solution No. 3 to be in the proportion required to remove the estimated
quantity of carbonic acid. Upon passing the solution through the "scrubber
the solution No. 1 (chloride of barium), the ammonia will combine with the
chlorine, and the carbonic acid liberated will combine with the barium libe-
rated, and form two new compounds, chloride of ammonia and carbonate of
barytes. The solution No. 3, will combine with the free carbonic acid, and
form carbonate of barytes, and the whole of the new combinations will run out
of the "scrubber" by the exit pipe, and upon being allowed to stand, the carbo-
nate of barytes will precipitate, and the chloride of ammonia remain in
solution; the solution to be run from off the precipitate, and again passed
through the "scrubber" until the whole or nearly the whole of the solution is
decomposed, or will not deprive the gas of ammonia and carbonic acid ascer-
tained by the usual tests; or when nearly decomposed, it may be completed by
adding the required quantity of ammoniacal liquor from the condensers, or
should it have ammonia in slight excess by adding chloride of barium solution.
Upon allowing the solution to stand after passing through the scrubber, or the
addition of the ammoniacal liquor, the carbonate of barytes will precipitate,
and the clear solution be chloride of ammonia to be treated as before described
for making muriate of ammonia (sal ammoniac). The precipitated carbonate
of barytes, treated as before described, for making carbonate or caustic soda,
or the solution No. 3. When a large quantity of gas has to be purified, two
or more "scrubbers" should be used.. Assuming that two "scrubbers" are
used, numbered No. 1 and No. 2, the foul gas is first to be passed through
No. 1, and then through No. 2, when the solution in No. 1 will not deprive
the gas of ammonia and carbonic acid; the solution from No. 2 is then to be
used in No. 1 and No. 2, supplied with fresh solution, but the gas is to be
passed through the requisite, number of "scrubbers," until perfectly purified
from ammonia and carbonic acid, ascertained by the usual tests. When the
whole of the ammonia and carbonic acid bas been removed, the gas is to be
passed through the ordinary "scrubber or "scrubbers," being supplied with
the purifying solution No. 2, caustic soda, to remove the sulphur in combination
with bydrogen, or the sulphur in combination with carbon, and the solution
ガ

page_text: used until it will not deprive the gas of sulphur, ascertained by the usual test.
Assuming that two "scrubbers" are in use, numbered No. 3 and No. 4, the
solution would only be once run through No. 3 (being the first "scrubber" to
receive the gas after the ammonia, &c., had been removed); and the solution,
after passing through No. 4 to be used in No. 3, and fresh solution used in
No. 4, but the gas would be required to be passed through the requisite number
of scrubbers until deprived of all sulphur, ascertained by the usual test. When
the solution has been passed through the "scrubbers" as described, it is to be
evaporated to a salt, and placed in a furnace with about one-third of its bulk
of sawdust, and kept at a dull red heat for about two hours, and then re-
moved and dissolved, when cold, and may be made caustic, and if the required
specific gravity to be the purifying solution No. 2. When the gas has been
deprived of ammonia, sulphur, and carbonic acid by the means herein-before
described, it is to be conveyed to the gasholder (gasometer) for use.
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 confine myself to the precise details above stated, as any chemist practi-
cally acquainted with this department of the art will understand the variations
which may be made without departing from the principle for obtaining the
results herein-before described; and I wish it to be understood that I do not
claim as new or as of. my Invention, or the exclusive use of the decomposition
of salt by sulphuric acid to obtain muriatic acid and sulphate of soda, or
"scrubbers" or evaporating pans, or the decomposition, or vaporisation and
recovering of substances, or the several processes as herein-before mentioned
or referred to, except so far as the same may be employed in and for the
purpose of my said Invention, which I do hereby declare to consist in the
purification of gas by the removal of the impurities, and obtaining the several
products as herein-before described.
In witness whereof, I, the said Thomas Greenshields have hereunto set
my hand and seal, this Eighth day of December, in the year of our
Lord One thousand eight hundred and fifty-nine.
THOMAS (L.s.) GREENSHIELDS.
Witness,
AUGUSTUS PIERRE DE LA MARE.