Year: 1886

page_text: We EDWARD WILLIAM PARNELL of Queen's Park Chester in the county of
Chester Analytical chemist and JAMES SIMPSON of Sa Rumford Place Liverpool
in the county of Lancaster Alkali Manufacturer do hereby declare the nature of
this invention to be as follows:-
In various chemical industries in which carbonic acid gas is employed the
difficulty and expense of procuring the gas in quantity otherwise than in a dilute
or impure condition have always been obstacles in the way of the developement of
certain manufactures The object of our invention is to produce pure carbonic acid
gas in a cheap and efficient manner from impure gas such as that obtained from a
lime kiln or from the products of combustion.
Our invention is based on the well known fact that a solution of monocarbonate
of ammonia will absorb carbonic acid gas when cold and will liberate a portion of
the latter when heated: but our method of employing this general principle so
as to make it commercially and industrially valuable necessitates a combination
of special operations each of which is essential to the efficiency of the entire
process.
In carrying our invention into operation we treat a solution containing from
25 to 30 per cent of carbonate of ammonia with carbonic acid gas (preferably in a
tower such as is used in the Solvay Ammonia Alkali Process) till a portion of the
Wo
carbonate of ammonia is converted into crystals of bicarbonate of ammonia.
then separate the crystals so formed from the greater part of the mother liquor,
leaving about enough to cover them; and heat them by a steam pipe or any other
convenient means in a closed vessel, fitted with outlet pipe, to a temperature not
so high as boiling point say to 160° F. when the bicarbonate of ammonia will be
decomposed giving off nearly half of its carbonic acid in a pure condition available
for use in the arts while the ammonia will be reduced to the state of carbonate
mixed with some sesquicarbonate. This solution (which we will refer to as
carbonate of ammonia) is then cooled by any convenient means and is again
treated with the impure carbonic acid gas for the production of bicarbonate of
ammonia crystals and the operation is repeated.
In practice we sometimes add a little water to the bicarbonate crystals in lieu
of mother liquor before applying the heat in order to compensate for any evaporation

page_text: which may take place under certain conditions. The escaping gases from the
treatment with impure carbonic acid gas ought to be washed in water or acid to
arrest any ammonia that may be carried over.
In conducting the decomposition of the bicarbonate of ammonia in the manner
described that is to say at à temperature below the boiling point of a solution of
carbonate of ammonia the pure carbonic acid gas is given off in a cool condition
without admixture of steam and at a trifling expenditure for fuel while the range
of temperature required for cooling of the resulting solution of carbonate of
ammonia, prior to repeated treatment with carbonic acid gas, is reduced to a
minimum.
By this process a given quantity of carbonate of ammonia can be used
continuously while any loss caused by ammonia being carried over will be
exceedingly small in consequence of the low temperature at which the operations
are conducted.

page_text: Improvements in the Production of Pure Carbonio Acid Gas.
We EDWARD WILLIAM PARNELL of Queens Park, Chester, in the County of
Chester, and JAMES SIMPSON of N° 84 Rumford place Liverpool, in the County
of Lancaster, Alkali Manufacturers do hereby declare the nature of the said
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:—
In various chemical industries in which carbonic acid gas is employed, the
difficulty and expense of procuring the gas in quantity, otherwise than in a dilute,
or impure condition, have always been obstacles in the way of the developement
of certain manufactures.
The object of our invention is to produce pure carbonic acid gas in a cheap and
efficient manner from impure gas, such as that obtained from a lime kiln, or from
the products of combustion, and our invention is based on the well known fact;
that a solution of monocarbonate of ammonia will absorb carbonic acid gas when
cold say at a temperature lower than 80° F and will liberate carbonic acid gas
when heated say to temperature above 150° F If the solution of monocarbonate
of ammonia is sufficiently strong, bicarbonate of ammonia crystals will be formed:
and if the crystals be heated in the presence of a small proportion of water, say
enough to cover them, the crystals will be decomposed and will disappear leaving
a solution, consisting chiefly of monocarbonate of ammonia. But to make the
general principle available in a method for obtaining pure carbonic acid gas
economically, and to render the method or process of manufacture commercially
and industrially. valuable, we make use of special combinations of operations each of
which is essential to the efficiency of the process.
The invention consists essentially (A) in treating a solution of monocarbonate of
ammonia of suitable strength with dilute or impure carbonic acid gas, until a
sufficient quantity of crystals of bicarbonate of ammonia is formed (B) in heating
the crystals to drive off carbonic acid gas (C) in recarbonating the monocarbonate
liquor produced and (D) in repeating the process. In detail the invention is
carried into practice as follows:-
Dilute or impure carbonic acid gas obtained from a lime kiln, from products of
combustion, or from any other source, in a cheap manner, is after washing and
cooling, brought into contact with a cold aqueous solution containing from 25 to
30 per cent of carbonate of ammonia. The proportion of carbonate of ammonia in
solution may be greater or less than the above, but between the limits given, good
results are obtained. The operation is carried on in suitable apparatus for facili-
tating the absorption of gases by liquids and at as low a temperature as can be
conveniently maintained say not exceeding 70° F. The tower known by the
name of the Solvay absorption tower used in the ammonia alkali process may be
employed.
The crystals of bicarbonate of ammonia formed during the above process are
separated to a considerable extent from the mother liquor, if the best results are
desired, and are heated to a temperature of 150° F. or over, but not so high as
boiling point, a temperature of about 165° F being found to answer well in

page_text: practice, this operation is conveniently carried on in a metallic vessel having inlet
and discharge ways. The said vessel is heated by a steam jacket, or coil, or by
direct heat from products of combustion.
The carbonic acid evolved from the heated crystals, carrying with it some
carbonate of ammonia and aqueous vapour is passed through a suitable cooling
apparatus, so arranged that the products of condensation may be returned to the
vessel containing the bicarbonate of ammonia crystals; after passing through the
Baid cooling apparatus, and being thoroughly cooled, the carbonic acid will only
contain a very small proportion of ammonia, which may be caught in a wash
tower. After cooling the carbonic acid gas, it is washed with acid, water, or brine
to separate any traces of ammonia. When the carbonic acid leaves the washing
apparatus it is ready for use.
The liquor which remains after the crystals have been heated is cooled in the
same vessel which was used for heating, or in a seperate vessel if desired. During
cooling, the liquor deposits bicarbonate of ammonia crystals, which (when the
heating vessel is also used as a cooler) are allowed to remain in the said vessel
whilst the liquor is run off, and passed again into the absolving apparatus. When
the liquor is cooled in a vessel detached from the heating vessel, the crystals of
bicarbonate deposited are separated from it and returned to the said heating
vessel.
To economize as much as possible the reagents used, the gases escaping from the
absorption apparatus, are brought into contact with acid, water, or brine, to remove
any traces of ammonia, as herein before mentioned. The ammoniacal products
thus obtained from the carbonic acid gas and escaping gases are treated in any
usual manner for the recovery of ammonia. The ammoniacal gas obtained is
collected in water and added to the mother liquor in the absorption tower.
.
In order to enable others to carry our invention into practice with certainty and
economy we have appended a sheet of drawings, giving an illustration of arrange-
ment of apparatus suitable for use in conducting all the combinations of operations
which constitute our invention.
a. represents a lime kiln, in which impure carbonic acid is produced, b. pipe
leading from the limo kiln, to the wash tower c., d. pipe leading from the wash-
tower c. to the pump e. f. pipe leading from the pump e. to the absorption
apparatus g. h. pipe leading from the absorption apparatus g. to the heater or
decomposing vessel i., j. pipe leading from the heater i. to the cooling apparatus k.,
1. pipe leading from the cooling apparatus k. to the acid tower m., n. pipe leading
from the acid tower to a gasometer or other receptacle. o. pipe leading from the
heater to the pump r., q. pipe leading from the pump r. to the refrigerator p.,
8. pipe leading from the refrigerator p., to the carbonator, or absorption apparatus g.,
t. way leading any gases escaping from 9. to a wash tower u. v, w, x, and y. draw
off doors and ways.-Regulating cocks and valves are provided between the various
parts of the apparatus. The above drawing is only intended to indicate apparatus
and connections combined, so as to shew the complete series of operations. As all
the various parts are commonly used in chemical operations, each manufacturer
can arrange the various appliances to suit the space at his command and may
dispense with some of the parts such as the tower u. if it is not considered desirable
to economise the products, to the greatest possible extent.
In the apparatus shown, impure carbonic acid gas evolved from the kiln a. would
be washed in the tower c. and forced by the pump e. through the carbonator g.
where it would come into contact with the solution of monocarbonate of ammonia
and convert it into bicarbonate. The bicarbonate crystals with at least sufficient
mother liquor to cover them are drawn through h. into i. where they are heated by
steam or otherwise, until carbonic acid gas is evolved to the required extent.
acid passes through the cooling apparatus k and wash tower m. to a gasometer or
elsewhere as desired. Before drawing the bicarbonate crystals into i. some of the
mother liquor in.g. might be run into the refrigerator p. After heating, the liquor
is run from, by the pipe o, and forced into the refrigerator p and carbonator g. by
The

page_text: the pump r., any bicarbonate crystals deposited in the refrigerator p. and cooler k
are removed through x. and y. and deposited in the heater i., or the cooler k. may
be so disposed that the bicarbonate will be washed back into i., any acid ammoniacal
products obtained in m and u. are conveyed through v and w. to ammonia recovery
apparatus.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is :-
First. In the production of pure, or practically pure, carbonic acid gas, from
lime kiln gas, or from the products of combustion, the repeated use or employment
of carbonate of ammonia for the alternate absorption and liberation of the said
carbonic acid, the absorption being conducted at a low temperature and the
subsequent liberation at a higher temperature, substantially in the manner described
and for the purpose set forth.
Second. The manufacture of carbonic acid gas by means of the combination of
parts and according to the process substantially as hereinbefore described.
J. T. KING, Agent,
Per J. Johnson.