Improvements in Separating Carbonic Acid from other _Gases, specially in the Production of Gas for Lighting and Heating Purposes Free, or practically Free, from Carbonic Oxide.
Year: 1891

page_text: Date of Application, 4th Feb., 1891-Accepted, 21st Mar., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by JOSÉ CARLOS REISSIG, La Plata, Argentine
Republic, Gentleman, and JOHN LANDIU, Regeringsgatan 58, Stockholm,
Sweden, Engineer.]
Improvements in Separating Carbonic Acid from other _Gases,
specially in the Production of Gas for Lighting and Heating
Purposes Free, or practically Free, from Carbonic Oxide.
I, PATRICK FRASER MACCALLUM, of Fairbank, Helensburgh, in the County of
Dumbarton, Engineer, do hereby declare the nature of this invention, and in what
manner the same is to be performed (as communicated to me) to be particularly
described and ascertained in and by the following statement:-
The main object of this invention is the removal of carbonic acid from combustible
and other gases with a view to increasing the calorific power of the gases treated
the removed carbonic acid being a residual product, which may be utilized in any
desired manner.
It is well known that when steam is passed through incandescent carbonaceous.
fuel, maintained at a temperature of about 550° to 750° Centigrade the result is the
production of a gas consisting mainly of hydrogen and carbonic acid, with only
small quantities of carbonic oxide; and that when the fuel is maintained at a higher
temperature the proportion of carbonic oxide increases till at a temperature of
about 1000° Centigrade, the gas resulting consists of a mixture containing
about 40 per cent. carbonic oxide and 50 per cent. hydrogen with only about 5 per cent.
of carbonic acid. This mixture is commonly known as water gas; and its use is
often objected to on account of the poisonous properties of the large amount of
carbonic oxide contained.
In the preparation of calefacient gas containing only a small per centage of
carbonic oxide, we proceed as follows:-
Steam preferably superheated or water is passed through fuel contained either in
externally heated retorts, or in water gas generators, maintained at a temperature
of about 550° to 750° Centigrade. The resulting gas consisting principally of a
mixture of hydrogen and carbonic acid, in the proportion of about two-thirds
hydrogen to one-third carbonic acid-is cooled and freed from sulphur impurities
in the ordinary way. The gas is then passed through an absorbing apparatus
containing carbonates of alkalies or alkaline earths, solid or soluted in or mixed
with water, preferably employing a solution of sodic carbonate (soda) or potassic
carbonate (potash). These substances and solutions freely absorb-especially under
pressure the carbonic acid, with the attendant formation of bi-carbonates-from
which the carbonic acid may be easily removed by the action of a moderate vacuum,
or by the application of heat and vacuum in combination. After the removal of
the carbonic acid the remaining gas which is principally hydrogen is or may be
conducted to a gas holder for use as required and the mixtures or solutions are
again available for the absorption of further quantities of carbonic acid the
operations being capable of repetition for an unlimited number of times.
The absorption apparatus should preferably be of such a description that the
absorbing solution is kept gradually descending from compartment to compartment
while the gas ascends through numerous small orifices arranged in such a way as to
bring the gas into contact with a large surface of the solution as practised for
example in some ammonia absorbing plants. By these means the solution or
mixture when saturated with carbonic acid may be from time to time drawn from
the lowest compartment of the apparatus, and conveyed to a separate vessel, in
which it is subjected to the action of a partial vacuum or to the action of partial
vacuum and heat in combination.

page_text: To ensure the exposure of a large surface of the solution to the action of the
partial vacuum,
the solution may be agitated in any convenient way, or injected
into the partial vacuum chamber in a finely divided state or spray.
The action of the partial vacuum, or of the partial vacuum and heat in combination,
effects the removal of the carbonic acid from the solution or mixture, and the
regenerated solution or mixture may-after cooling if heat has been employed-be
conveyed back to the upper compartment of the absorption apparatus, for absorbing
fresh quantities of carbonic acid.
The carbonic acid recovered from the solution or mixture may be utilized in any
desired way.
When two or more absorbing apparati are worked in conjunction the removal
of the carbonic acid from the saturated solutions or mixtures, in any of the apparati
may be effected without removal to a separate vessel.
Before passing the mixture of hydrogen and carbonic acid into the absorbing
apparatus, it may be subjected to a process of mechanical filtration, whereby
according to the known laws of the diffusion of gases much of the carbonic acid is
separated from the hydrogen.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me,
I declare that what I claim is :-
The method of separating carbonic acid from other gases-by its absorption-
with or without a previous mechanical filtration, in carbonates of alkalies or
alkaline earths and the subsequent recovery of the carbonic acid, from the formed
bicarbonates by the action of a partial vacuum, with or without the combined action
of heat mono-carbonates being thus reformed, which are again available for the
absorption of fresh quantities of carbonic acid, substantially as described.
Dated this Third day of February 1801
CRUIKSHANK & FAIRWEATHER,
62, St. Vincent Street, Glasgow, Agents.