An Improved Method of Recovering Carbonic Acid Gas from Lime Kilns and Furnaces, and Apparatus in connection therewith.
Year: 1891

page_text: Date of Application. 5th June, 1891
Complete Specification Left, 7th Mar., 1892-Accepted, 4th June, 1892
PROVISIONAL SPECIFICATION.
An Improved Method of Recovering Carbonic Acid Gas from Lime
Kilns and Furnaces, and Apparatus in connection therewith.
1, WALTER WALKER, of 132 Adelaide Road, in the County of London,
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to an improved method for recovering, at a comparatively
small cost, carbonic acid gas in a pure state from the gases of lime kilns and
furnaces by the use of carbonate of soda as the collecting and purifying agent.
In carrying out my invention the gases from the lime kilns or furnaces before
they are brought in contact with the carbonate of soda are preferably washed
in any ordinary manner and are then passed into suitable retorts or chambers
where carbonate of soda crystals are so exposed on trays or otherwise as to
ensure an intimate contact of the carbonic acid gas with the carbonate of soda
when the latter will collect the carbonic acid gas at a low temperature and
become bicarbonate of soda for the time being. This bicarbonate is then heated
to a higher temperature and gives off pure carbonic acid gas which is led into
a suitable gas holder and the carbonate of soda is left behind to be used over
and over again as the collecting and purifying agent.
Or to avoid the alteration in temperatures 1 may maintain the retorts or
chambers at an uniform temperature and pump the carbonic acid gas into the
retorts under pressure, and afterwards exhaust it by the pump. The pressure
and vacuum of the pump being chosen suitably, and preferably being about equal.
Or may both use less pressure and vacuum and change the temperature of
the retorts somewhat, having the lower temperature and pressure working together
when collecting carbonic acid and the higher temperature and vacuum working
together when giving it off.
As I only require comparatively low temperatures, I can use the waste heat of
boiler furnaces, or steam, or hot water, for heating the chambers or retorts.
Carbonic acid from other sources may also be recovered by this method.
Any close topped gas fired kiln will answer my purpose, but I would prefer one
fired with water gas in order to reduce the nitrogen in the gases to a minimum.
When absorbing the carbonic acid gas the nitrogen and some of the carbonic
acid escapes to a chimney flue through suitable valves or devices properly
adapted, if needful, to enable the requisite pressure to be maintained.
In order to get rid of any nitrogen remaining I may let in carbonic acid from
a reservoir of the same when the current of the gas entering from the kiln or
furnace is cut off, and may allow the carbonic acid to continue to enter after the
vacuum pumps are started if any are used.
If requisite provide means for supplying water to the retorts by a jet or
spray or in some other suitable manner to keep the carbonate of soda in a state
of crystallization as the soda crystals have been found to absorb carbonic acid
more readily than anhydrous carbonate of soda.
The carbonate of soda is not wasted but when it has collected the carbonic
acid gas, it becomes for the time being bicarbonate of soda, and after it has
parted with the carbonic acid it again returns to carbonate of soda to be used
over and over to collect and purify the gases.
⚫ I may:
if deemed advisable, use carbonate of potassium or any other carbonate
which may be found suitable instead of carbonate of soda to obtain the result
required. I prefer as stated to use the carbonates in the shape of crystals but

page_text: they may be used either in solution; or in a paste, or in an anhydrous or
uncrystallized form with or without mechanical agitation.
Dated this 5th day of June 1891.
ERNEST DE PASS,
78, Fleet Street, London, and 6, Victoria Street, Nottingham,
Agent for the Applicant.
COMPLETE SPECIFICATION.
An Improved Method of Recovering Carbonic Acid Gas from Lime
Kilns and Furnaces, and Apparatus in connection therewith.
I, WALTER WALKER, of 132, Adelaide Road, in the County of London,
Engineer, 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, reference being had to the accompanying drawings and to
the letters and figures marked thereon, that is to say :-
My invention relates to an improved method of recovering, at a comparatively
small cost, carbonic acid gas in a pure state from the gases of lime kilns and
furnaces by the use of carbonate of soda as the collecting.and purifying agent.
The
In carrying out my invention the gases from the lime kilns or furnaces before
they are brought in contact with the carbonate of soda are preferably washed, in
any ordinary manner, and are then passed into suitable retorts or chambers where
carbonate of soda crystals are so exposed on trays, or otherwise, as to insure an
intimate contact of the carbonic acid gas with the carbonate of soda.
carbonate of soda will collect the carbonic acid gas at a low temperature and
become bi-carbonate of soda for the time being. This bicarbonate is then heated to
a higher temperature and gives off pure carbonic acid gas which is led into a
suitable gas holder, and the carbonate of soda is left behind to be used over and
over again as the collecting and purifying agent.
Or to avoid the alteration in temperature I may maintain the retorts or chambers
at an uniform temperature and pump the gases into the retorts under pressure, and
afterwards exhaust them by the pump. The pressure and vacuum of the pump
being chosen suitably, and preferably being about equal. Or I may use both less
pressure and vacuum and change the temperature of the retorts somewhat, having
the lower temperature and pressure working together when collecting the carbonic
acid, and the higher temperature and vacuum working together when giving it off.
Or I may allow the carbonate of soda to take up the carbonic acid at the natural
low temperature, using pressure from the pump to help it, and allow it to give off
the carbonic acid at the natural high temperature, using suction from the pump to
help it.
As I only require comparatively low temperatures, I can use the waste heat of
boiler furnaces, or steam, or hot water, for heating the chambers or retorts.
Carbonic acid from other sources may also be recovered by this method.
Any close-topped gas fired kiln will answer my purpose, but I would prefer one
fired with water gas in order to reduce the nitrogen in the gases to a minimum.
When absorbing the carbonic acid gas, the nitrogen and some of the carbonic
acid may escape to a chimney flue, through suitable valves or devices properly
adapted, if needful, to enable the requisite pressure to be maintained.
In order to get rid of any nitrogen remaining, I may let in carbonic acid from a
reservoir of the same when the current of the gas entering from the kiln or furnace
is cut off, and may allow the carbonic acid to continue to enter after the vacuum
pumps are started, if any are used.
If requisite, I provide means for supplying water to the retorts by a jet or spray,
or in some other suitable manner, to keep the carbonate of soila in a state of

page_text: crystallization, as the soda crystals have been found to absorb carbonic acid more
readily than anhydrous carbonate of soda.
The carbonate of soda is not wasted, but when it has collected the carbonic acid
gas it becomes, for the time being, bicarbonate of soda, and after it has parted with
the carbonic acid it again returns to carbonate of soda to be used over and over to
collect and purify the gases.
I may, if deemed advisable, use carbonate of potassium or any other carbonate
which may be found suitable, instead of carbonate of soda, to obtain the result
required. I prefer, as stated, to use the carbonates in the form of crystals, but
they may be used either in solution, or in a paste, or in an anhydrous or
uncrystallized form, with or without mechanical agitation.
In order that my invention may be readily understood, I proceed to describe
the same fully with reference to the drawings which show, by way of example,
apparatus suitable for my purpose.
Fig. 1 is a sectional elevation; Fig. 2 is a plan; aud Fig. 3 is a vertical cross
section on the line A, A, of Fig. 2, showing the apparatus I prefer to employ in
carrying out my improved method.
Fig. 4 is a plan of one of the retorts with its cover or upper portion removed.
In the drawings I have only shown two of the retorts viz.: the first and the last
of a series; it is however to be understood that in practice any suitable number can
be employed.
The gases from which pure carbonic acid is to be recovered, having been
previously washed, are conducted by means of the inlet pipe à to the first of the
series of retorts b. Each of these retorts may advantageously consist of a cast
iron vessel formed in halves which are flanged and bolted together and covered
with any suitable material b', for preventing the radiation of heat. Within each
retort is a frame upon which rests a coil of piping ; and above this piping
is a perforated shelf & whose upper surface is covered with a filter cloth b. The
filter cloth may be of slightly larger diameter than that of the interior of the
retort so as to permit of its edges being nipped between the flanges when the
halves of the retort are bolted together, thereby enabling said filter cloth to be
firmly retained in position.
The carbonate of soda, or other carbonate employed, which is preferably in a
crystalline form, is placed into the retort through a manhole 6, and is heaped
upon the filter cloth. The retorts are connected together by means of pipes a¹,
the lower portion of one retort being in communication with the upper portion
of the next, and so on throughout the series until the last retort is reached.
This last retort is, by means of a pipe a², in communication with a long tube a*
which dips into and extends almost to the bottom of a tank a³ containing a column
of water.
When the inlet valve a is opened the gases are free to pass into the retorts,
and by means of a force pump connected to the inlet pipe at a said gases are
forced into and through all the retorts in succession. The before mentioned
tube a is provided with a valve a which, when the force pump is set to work,
is opened so as to put said tube a* into communication with the retorts; the
column of water in the tank a then serves as a regulator for preventing the
pressure produced by forcing the gases into the retorts from becoming excessive.
Most of the carbonic acid contained in the impure gases, as they pass through
the series of retorts, conies into intimate contact with the carbonate crystals and,
for the time being, converts them into bicarbonate of soda. Any of the carbonic
acid which was not taken up by the crystals, and most of the nitrogen, or other
impurities, which existed in the gases will have escaped through suitable valves
to a chimney, but any nitrogen, or other impurities, which may have remained
within the retorts in a gaseous condition will, after the valve a' is closed and the
current of gas cut off, be expelled either by forcing through the retorts pure
carbonic acid from a reservoir of the same, or after the vacuum pumps are started

page_text: by allowing the first carbonic acid gas given off from the bicarbonate, to pass
through into the chimney Hues instead of into the gas holder and carry all
nitrogen or impurities with it.
The nitrogen, e, having been entirely removed, steam or hot water is admitted
to the coils of piping and the temperature within the retoris is thereby raised to
about 170° F., which will cause the bicarbonate to give off the pure carbonic acid it
had previously collected from the impure gases coming from the lime kilns, or
elsewhere. An aspirator connected to the pipe a* at a is then set into operation
whereby the pure carbonic acid is withdrawn from the retorts and led into a
suitable gas holder.
The saturated solution which the carbonate crystals part with in the process
trickles through the filter cloth and falls into the lower portion of the retort,
whence it finds its way down the inclined pipe & into a chamber c with which each
retort is provided; and from this chamber it can be allowed to flow into a trough d
where it is allowed to remain until the crystals re-form, when they can be removed
and be used over again.
The chamber c, as well as the inclined pipes 67, are respectively furnished with
valves and each set being arranged to be operated simultaneously by means of
their respective rods and c extending from end to end of the series.
So soon as all the carbonic acid has been withdrawn from the retorts, the steam
or.hot water circulating in the coils of piping is shut off, and, if desirable, cold
water may then be circulated through these coils so as to reduce the temperature
in the retorts to about 70° F. Water, or steam, coming through the pipe e is next
admitted to the retorts through the rose ' in the form of a spray by means of the
jet apparatus g with which cach retort is provided; the said jet apparatus being
operated by steam entering through the pipe f. The carbonate is thus kept in a
crystalline state and is ready to again collect and recover the carbonic acid from
the gases when these latter are admitted to the retorts during a fresh operation.
It will thus be seen that, according to my method of recovering carbonic acid, the
carbonate crystals are not wasted, but are available for use over and over again.
Instead of allowing the saturated solution to flow into the chambers c, as above
explained, I can, if preferred, dispense with these chambers and allow said solution
to collect in the space at the bottom of the retorts, and employ a pipe extending
through the carbonate crystals and dipping into the solution. By passing gas
under pressure through this pipe, the solution can be forced back into the upper
part of the retorts and be caused to fall upon the carbonate in the form of a spray,
or otherwise, and, if necessary, I could supply a little added water, or steam, so as
to keep the carbonate in a crystalline state.
The carbonic acid gas recovered according to my invention can be compressed
in cylinders for sale to mineral water manufacturers, or others, at a much less cost
than it is now produced by them.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:.
―:
1. The improved method of recovering carbonic acid gas, in a pure state, from
the gases of lime kilns, furnaces, and other sources, by the use of carbonate of soda
as the collecting and purifying agent, and which agent is capable of use over and
over again substantially as herein described.
2. The improved method of recovering carbonic acid gas, in a pure state, from
the gases of lime kilns, furnaces, and other sources, by the use of carbonate of
potassium, or other suitable carbonate, as the collecting, and purifying agent, and
either in the form of crystals, or in solution, or in a paste, or in an anhydrous or
uncrystallized form, and with or without mechanical agitation, such carbonate
being capable of use again and again, substantially as herein described.
3. The general arrangement and combination of parts constituting the apparatus

page_text: for use in the herein described method of recovering pure carbonic acid gas from
lime kilns, furnaces, and other sources, substantially as specified and as shown with
reference to the accompanying drawings.
Dated this 7th day of March 1892.
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 6, Victoria Street, Nottingham,
Agent for the Applicant.