Improvements in the Production of Carbonic Acid from Bicarbonates of Soda.
Year: 1891

page_text: Date of Application, 15th Jun, 1891-Accepted, 1st Aug., 1891
COMPLETE SPECIFICATION.
Improvements in the Production of Carbonic Acid from
Bicarbonates of Soda.
Dr. EDWARD LUHMANN Andernach-on-Rhine, Chemist do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The most suitable means for the production of carbonic acid gas for the different
specific purposes for which same is now daily used it has been ascertained, are the
use of bicarbonate alkalies (by bi-carbonate alkalies I do not intend to restrict myself
here, and in the following, to strictly speaking bi-carbonates, but this term will also
apply to an intermediate stage between mono and bi-carbonates, which salt is
formed in consequence of mono-carbonates coming into contact with free carbonic
acid) and the decomposition of same into mono-carbonate alkalies and carbonic acid
and the consequent regeneration of such mono-carbonates into bi-carbonates.
The difficulty however which has arisen has been to promote a sufficiently close
contact of the mono-carbonates with regenerating carbonic acid so as to secure an
effectual absorption of this gas.
The complete transformation of the mono-carbonate alkalies into bicarbonates is
mainly dependent upon this close contact, hence this forms the leading feature of
the whole process subject of this Specification.
In order to attain this object viz. the close contact of the gases and of the
mono-carbonates, I construct an apparatus composed of a series of horizontal and
parallel or otherwise suitably placed discs disposed after the fashion of alternately
overlapping steps over which the solution, which enters the top of the apparatus
under pressure obtained in the solution boiler is made to run step by step, in such a
way moreover, that this introduction of liquid into the boiler is produced in the
shape of a spray, this latter being either continuous or intermittent, and the carbonic
acid which might have passed all the different steps without having been absorbed by
the mono-carbonate solution, reaches the spray within the top of the apparatus is
brought into close contact with the mono-carbonate alkali solution in this state of finc
division. It goes without saying that the concentrated solution which comes from
the boiler is passed through a cooling apparatus previous to its being introduced into
the step apparatus under the shape of a spray, so that this solution is reduced to the
temperature most appropriate for the absorption of the carbonic acid.
A further characteristic of this process for the production of carbonic acid is
that same is introduced into the step apparatus in a highly concentrated state as
same is obtained directly from the products of combustion from the coke fire, and
is unmixed with the outer atmospheric air, but is simply freed of its sulphurated
gases through its being passed through a scrubber and cooled by means of a water
spray entering the step apparatus at the lower part of same.
This direct utilization of the carbonic acid resulting from the combustion gases,
necessitates especial construction of the grate of the coke furnace so as to avoid the
entrance of superfluous air. For that purpose the coke furnace is built after the
fashion of an upright tray furnace and the rear parts of the grate are formed of
pipes the extremities of which enter the boiler at two different parts whereby the
harmful introduction of an admixture of air is prevented and an energetic heating
of the solution which creates a rapid concentration and complete decomposition of
same (freeing of carbonic acid) is obtained.
It is important to maintain the coke fire at a dull red heat, and to avoid white
heat, as the overheating of the furnace easily results in the reduction of the carbonic
acid, in consequence of incandescent carbon being transformed into carbonic oxide and
in gaseous combinations of sulphur the contact of which with the carbonate solution

page_text: would form hydro-sulphureous gases which would render the carbonic acid impure.
The disposition of pipes or pipe shaped baths of the coke furnace completely avoids
this defect.
66 "
The construction of the apparatus is illustrated in the accompanying drawing.
is the solution boiler which is heated by means of the upright tray shaped coke
furnace "a." The front of the solution boiler and the bottom of same are connected
outwardly by means of a series of pipes "s "and form the rear part of the furnace,
the front part of same being formed of a number of firebars of usual construction.
The gases of the coke fire which heats the boiler, and the mono-carbonate alkali
solution contained therein, enter the lower part of the cooling and washing
apparatus "" by means of the flue "e" and pipe "c" and this washing and cooling
cylinder is filled with a quantity of small pieces of suitable material, on which a
number of small jets of water supplied from the tank "w" play from the top, so
that the combustion gases are cooled and washed in traversing this apparatus.
33
a
These gases collect in the upper part of the cooling apparatus and enter the
lower part of the step apparatus "" in which a great number of horizontal,
parallel, or otherwise suitably constructed discs are inserted by means of the
pipe 6. A blower or similar appliance may with advantage be inserted between
the washer and the step or absorption apparatus. The steam produced in boiler "
by the ebullition of the solution, forces this solution through a coil shaped
arrangement of pipes contained in the cooling tank for the purpose of cooling the
solution. This cooler is also supplied with water from the tank " W. The cooled
solution, which is of course under pressure enters the top of the absorption cylinder
by means of the pipe "" and is at this point divided into minute jets by means of
a rose or other spraying apparatus. The mono-carbonate alkali solution as it runs
over the numerous discs "m" which provide large surfaces, is brought into close
contact with the carbonic acid coming from the opposite direction-and which in
this state has great absorbent power, so that the solution reaches the lower part of
the absorption apparatus fully saturated with the carbonic gas. The rose "3" is
arranged in such a way as to allow finely divided jets of the solution emanating
from same, to be still further brought into contact and to absorb any carbonic acid
which might remain free after having passed the absorption apparatus, thus avoiding
all waste of carbonic acid. The bi-carbonate alkali solution which has thus been
obtained runs through the pipe "n" into the vat "n" whence it is pumped by
means of the pump 66
" and through the pipe "n" into the boiling vessel "k."
The lower part of this vessel is provided with a series of perforated pipes which
are in communication with the steam pipe "" coming from the boiler ❝ a so that
the vapors which are of course still saturated with carbonic acid, considerably heat
the bi-carbonate solution contained in the vessel "k." The solution, now ridding
itself of the rest of the carbonic acid it still contains, is again transformed into
mono-carbonate solution, which latter runs through pipe "m into the container "t"
and hence is pumped back, by means of pump "p" through the pipes e e¹ into the
solution boiler " a," again to go through the circle afresh as described. The
carbonic acid, which accumulates in the upper part of the boiling vessel, is carried
away by means of a pipe into a cooler, and passes through a condensing trap,
the water of which is also returned to the container t so as to maintain a constant
concentration of the solution whilst the carbonic acid itself is collected in a
gasometer.
"
"
Having now particularly described and ascertained the nature of my inven-
tion, and in what way the same is carried out in practice I claim :-
1. The construction and use in connection with the extraction of carbonic acid
from bi-carbonate alkalies of an absorption apparatus formed of a series of parallel
horizontal or otherwise suitably disposed discs or surfaces alternately placed in
the form of steps substantially as described.
2. In combination with an apparatus mainly as described and claimed in Claim 1.
the use and construction of a spray or similar contrivance at the upper part of the

page_text: apparatus, with introduction of the carbonic acid at the lower part of same, and in
opposite direction to that of the solution entering by means of the rose for the
purpose set forth substantially as described.
3. In an apparatus substantially as described and claimed in the previous claims,
the use of carbonic acid obtained directly from the coke fire, in combination with
the specially constructed furnace for the purpose of regenerating the mono-carbonate
residue solution, substantially as described.
4. The use and construction, in connection with a process for the production of
carbonic acid, of an upright tray shaped furnace, the rear part of which is formed
of a series of tubes communicating with the boiler containing the solution,
substantially as described.
5. In an apparatus as described with an upright furnace, as claimed in Claim 4,
the construction and use of a system of circulating solution at the rear of the
furnace, for the purpose of preventing the coke fire from attaining too high a
temperature so as to avoid the production of carbonic oxide, substantially as
described.
6. In an apparatus substantially as set forth, the combination of an absorption
tower, the utilization of carbonic acid obtained directly from a coke fire, the
construction and use of a closed coke furnace with hollowed fire tubes at the rear in
communication with the solution boiler, and the way of connecting these different
parts so as to form a continuous circle, the whole substantially as described.
Dated this 15th day of June 1891
F. FANTA,
85, Gresham Street, Agent for Applicant.