AN IMPROVED PROCESS POR PURIFYING GAS
Year: 1853

page_text: LETTERS PATENT to Richard Laming, of Millwall, Poplar, in the
County of Middlesex, Chemist, for the Invention of "AN IMPROVED
PROCESS POR PURIFYING GAS"
Sealed the 18th November 1853, and dated the 13th September 1853.
PROVISIONAL SPECIFICATION left by the said Richard Laming
at the Office of the Commissioners of Patents, with his Peti-
tion, on the 18th September 1853.
I, RICHARD LAMING, do hereby declare the nature of the said Inven-
tion for "AN IMPROVED PROCESS FOR PURIFYING GAS " to be as follows:-
My Invention consists in a particular combination or combinations
of operations for purifying gas from carbonic acid, hydrosulphuric acid,
and ammonia by means of ammonia water and a metallic compound
or compounds, and without the use of any lime.
With respect to my first operation, the impurities above named exist
in gas partly as hydrosulphate of ammonia and carbonate of ammonia,
and partly as free hydrosulphuric and carbonic acids; but hydrosulphate
of ammonia cannot permanently exist in contact with free carbonic
acid; and, in conformity to that fact, if ammonia be added to a
mixture of hydrosulphuric and carbonic acids it will, in preference,

page_text: combine with the latter. The object of my first operation is to establish
chemical contact between all the free carbonic acid in the gas and
ammonia, and to wash them out in combination. As there is seldom
or never enough of ammonia in the gas to saturate its carbonic acid I
make up for the deficiency by supplying ammonia, either in a free state
or as hydrosulphate of ammonia, or even as carbonate of ammonia,
provided only that the latter salt has not already got its maximum dose
of carbonic acid. The whole of the carbonic acid is thus made into
soluble carbonate of ammonia, and washed out by means of water.
As in practice more ammonia is introduced into the gas during this
my first operation than is equivalent to the free carbonic acid present,
the excess will remain combined with hydrosulphuric acid, and the
hydrosulphate of ammonia which thence results, being a very volatile
salt, tends to pass on with the gas out of the vessels in which the first
operation has been conducted. This I prevent by using such an abun-
dance of water as to wash out the last traces of both the ammoniacal
salts together, but in that case the resulting ammoniacal solution
becomes so diluted as to have less commercial value than is desirable.
To avoid this inconvenience, and at the same time to take out the last
traces of ammonia from the gas, I prefer to employ either a separate
washing or a metallic compound; as, for example, a salt of iron or
some other known re-agent capable of retaining at least the alkaline
constituent of hydrosulphate of ammonia, if not also its acid constituent.
The next operation is to purify the gas from free hydrosulphuric
acid. This I effect by causing the gas to be acted upon by an oxide
of iron susceptible, after being used, of re-acquiring its purifying energy
by exposure to the atmosphere; or the ammonia of the hydrosulphate
may be removed simultaneously with the hydrosulphuric acid by using
with the revivifiable oxide of iron a salt of iron, or other re-agent
capable under the circumstances of arresting the ammonia.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Richard Laming in the Great Seal Patent
Office on the 13th March 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
RICHARD LAMING, of Millwall, Poplar, in the County of Middlesex,
Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of September, in
the year of our Lord One thousand eight hundred and fifty-three,
in the seventeenth year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Richard Laming, Her
special license that I, the said Richard Laming, my executors, adminis-
trators, and assigns, or such others as I, the said Richard Laming,
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
"AN IMPROVED PROCESS FOR PURIFYING GAS," upon the condition (amongst
others) that I, the said Richard Laming, by an instrument in writing
under my hand and seal, 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 Richard Laming, 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 (that is to say):
My Invention of "An Improved Process for Purifying Gas" relates to
the use of a particular combination or combinations of operations
whereby the carbonic acid contained in the gas is first wholly converted
into carbonate of ammonia by additions of that alkali, and then removed
by washing, and afterwards the hydrosulphuric acid of the gas is
removed by the agency of oxide of iron.

page_text: It is not absolutely necessary for the ammonia used in my first
operation to be free from carbonic acid, provided it be capable of
absorbing still more; and, instead of ammonia, the hydrosulphate of that
alkali may be wholly or in part substituted, because hydrosulphate of
ammonia is decomposed by free carbonic acid into carbonate of am-
monia on their coming into contact. This state of contact between the
carbonic acid which exists naturally in the gas and the ammonia with
which it is intended to combine I establish by employing an apparatus
called a "scrubber." The scrubber is a vessel (generally cylindrical)
nearly filled with pieces of coke, gradually diminishing in size towards
the top. The gas intended to be purified generally enters the scrubber
by an aperture near the bottom, and leaves it by another aperture at
or near the top. Water or other purifying liquid enters at or near
the top, and, being distributed over the surface of the coke contained
in it, finds its way to the bottom of the scrubber, where the liquid
makes its exit, either finally, or to be again raised by a pump, and spread
over the surface of the coke, a process which is sometimes repeated on
the same portion of liquid many times in succession. Instead of coke,
the scrubber may be filled with other materials, as brickbats, coarse
gravel, or brushwood. Various mechanical contrivances are in use for
distributing the purifying liquid over the surface of the materials with
which the scrubber is charged; and this liquid is generally supplied to
the distributing apparatus by a pump or elevated cistern, and received
after its descent into a tank or reservoir near the base of the scrubber.
The scrubber is usually made of iron, and should either be of such
height and diameter as that the gas which enters foul below may make
its exit above, purified from that particular impurity for which the
scrubber has been used; or, what is better, deficiency in the size of
the scrubber may be compensated for by employing two or more scrub-
bers for one and the same operation.
In my improved process I prefer to use a set of scrubbers for a
single operation, but whether a set be used or only a single scrubber I
prefer that the gas and the purifying liquid should pass in opposite
directions. In the case of a set of scrubbers being used I employ the
same liquid consecutively in each of the scrubbers, beginning with
that through which the gas passes last, and neding with that by which

page_text: the gas enters the set, whereby the purifying liquid is separated into
distinct portions, and the finishing of the purification of the gas from
any particular impurity is confided to that portion of the liquid most
competent to effect it.'
The ammonia which is necessary for my first operation 'may be
introduced in a gaseous state into the unpurified coal gas itself, or, when
scrubbers are used, it may be introduced into them in solution. The
same remark applies to hydrosulphate of ammonia, and also to ammonia
only partially saturated with carbonic acid. The ordinary gas liquor
made in the works, and which contains both hydrosulphate and
carbonate of ammonia, may be passed through the set of scrubbers,
instead of employing water to receive the addition of ammonia (either
free or combined, as above described), which will generally be necessary
to convert the whole of the carbonic acid of the gas into carbonate of
ammonia, especially when the coals used for making the gas abound
with carbonate of lime. The practical rule is to add to the gas by one
way or another not much more ammonia than will suffice to prevent
carbonic acid from passing out from the last scrubber of the set. The
liquid which flows out from the base of each scrubber being repeatedly
returned into it by its distributing apparatus, a time will arrive when it
may be found that the liquid in the scrubber by which the impure
gas enters the set will have become highly charged with carbonate of
ammonia, contaminated with other ammoniacal compounds. At that
time the said liquid should be withdrawn, and its place supplied by the
liquid from the scrubber next in succession, and thus onward to the
end of the set of scrubbers, if it comprise more than two, the last in
the set being supplied with fresh liquid.
The purification of the gas being thus far accomplished, I finish the
purification in dry lime purifiers by removing hydrosulphuric acid from
the gas by means of any moist oxide of iron, or mixture of oxide of
iron, artificial or native, which is susceptible of becoming changed in
the purifiers into sulphuret of iron, and afterwards of being reconverted
by exposure to the air back again into an oxide. In the Specification
of a Patent granted to me on the Fourth day of November, One
thousand eight hundred and forty-seven, I described several ways of

page_text: making oxide of iron suitable for purifying gas; but it may also be
obtained by art in other known ways, as well as in states of natural
combination with other matters, such as peat.
In using water for removing the carbonic acid combined with
ammonia I prefer to interpose between the washing operation and the
purification by oxide of iron a second set of scrubbers to remove any
ammonia which may have been added in excess in the first operation,
and which may have passed over from the last of the first set of
scrubbers in combination with hydrosulphuric acid. This second set is
to be managed as already explained with regard to the first set, the
charge being simply water.
I know that this second set of scrubbers is doing its duty so long
as I find that the gas leaves the last scrubber uncontaminated with
ammonia, and when this ceases to be the case I supply this last
scrubber with fresh water, transferring its liquid charge to the next
scrubber, and so on to the first of the set, the liquid from which I set
aside as a solution of hydrosulphate of ammonia to be introduced, as
occasion may require, into the last scrubber of the first set.
Instead of the intermediate scrubbing operation, as above described,
I sometimes mix with the oxide of iron a sufficient quantity of a
solution or powder of some metallic salt capable of combining with both
the elements of hydrosulphate of ammonia. Of these salts I prefer to
use a sulphate or a muriate of iron or manganese; or, if the first
operation be so carefully performed that only a small quantity of
ammonia passes along with the gas out from the last set of scrubbers,
the intermediate washing with water may be omitted, although the
oxide of iron in the subsequent process be used without any admixture
of a metallic salt, because, as a small quantity of ammonia is suscep-
tible of being absorbed into the mass of the moist oxide of iron, the
minute quantity of ammonia which under such circumstances would
find its way into the gas holders might not always be considered
objectionable.
Having thus described the best ways I am acquainted with for
putting my Invention into practice, I wish it to be understood that I
claim the purification of gas by saturating its carbonic acid with

page_text: ammonia, either alone or combined with hydrosulphuric acid, or even
combined with carbonic acid in less quantity than it can absorb, and
afterwards removing the resulting carbonate of ammonia, in conjunc-
tion with the further purification of the gas, from free hydrosulphuric
acid by any effective oxide of iron.
In witness whereof, I, the said Richard Laming, have hereunto
set my hand and seal, the Eleventh day of March, in the year
of our Lord One thousand eight hundred and fifty-four.
RICH LAMING. (L.S.)