An Improved Process for the Manufacture of Carbonic Acid, and Apparatus therefor.
Year: 1897

page_text: Date of Application, 28th Oct.,
1897
Complete Specification Left, 9th June, 1898-Accepted, 13th Aug., 1898
PROVISIONAL SPECIFICATION.
An Improved Process for the Manufacture of Carbonic Acid, and
Apparatus therefor.
I, HERBERT SAMUEL. ELWORTHY, temporarily of 69, Guilford Street, London,
care of Messrs. H. S. King & Co., 65, Cornhill, in the City and County of London,
Chemist and Chemical Engineer, do hereby declare the nature of this invention
to be as follows:-
My invention consists in an improved process of manufacturing carbonic acid
or carbon dioxide and apparatus therefore.
I carry this invention into effect in the following manner:-
Carbonic acid or steam or a mixture of carbonic acid and steam, or of either
of them with any suitable hydrocarbon in the gaseous fluid or solid state such
"astatki" or
for instance as acetylene gas, petroleum, petroleum residues as
"mazut" or other crude petroleum oils or residues, or any of the paraffine or
olefine series, or anthracine or napthol, or turpentine or turpenes or common
or other rosin, or bitumen or asphaltum or any similar hydrocarbonaceous sub-
stance, or the products of the destructive distillation of waste rubber, and many
other substances such for instance as, wood, and coal and wood tar, and their
products of distillation naphtha or any substances of whatever nature containing
the elements carbon and hydrogen, or carbon, hydrogen and oxygen, such as
wood spirit, ordinary alcohol, or the alcoholic series, also the organic acids such
as acetic acid, and the acetic series, oxalic, tartaric, citric, and others, also sugar,
glucose, starch, from whatever source, or grain, cotton, cotton waste, or any form
of lignose or cellulose, and substances containing in addition to the above three
elements, nitrogen, can also be used the nitrogen being converted into ammonia,
which may be removed in any suitable manner, such as by absorption in acid
solution, and the ammonia so removed, may be recovered and used in any way,
thus forming an additional source of profit."
Most of the above mentioned substances, which are liquid or gaseous or which
may be rendered so by heat, or by distillation, destructive or otherwise can be used
alone by passing them through the regenerative stoves, whereby they are resolved
into substances of simpler chemical constitution, which are readily oxidised by
passing through the oxidising furnaces, pure carbonic acid resulting. This method
is one of extreme simplicity,, and applicable in many cases, more especially where
hydrocarbons such as paraffines or natural gas can be readily obtained. Others
are applicable under special circumstances.
The above substances are strongly heated in a regenerative furnace or hot blast
stove, such for instance as a Cowper" or "Whitwell" stove, producing mutual
decomposition of the aforesaid mixture.
The carbon of the hydrocarbon removes a part of the oxygen from the carbonic.
acid reducing it thereby to carbonic oxide, or in the presence of steam the whole
of the oxygen thereof will be removed and the hydrogen will be liberated in

page_text: the free state, the carbon of the hydrocarbon being at the same time converted
into carbonic oxide and its hydrogen also liberated in the free state. Any
oxygen contained in the carbonaceous material will also combine to form carbonic
oxide.
This action takes place at a temperature well within the range of an apparatus
such as above indicated, whereas the decomposition of carbonic acid alone or
mixed with steam without addition of hydrocarbon is impossible unless at or
about the temperature at which the gases dissociate. In my process the highly
superheated gases are brought into contact with hydrocarbons and the decompo-
sition effected or the hydrocarbons themselves in the gaseous state are decomposed
as aforesaid. If solid carbonaceous materials are used, such as coal, coke, char-
coal, peat, etc., these are most conveniently placed in a separate chamber formed
of refractory material, and the carbonaceous material may be heated to the
required temperature to bring about decomposition by the steam or heated gases
itself, or may in the first instance be brought to a state of incandescence by ignition
in any of the ordinary ways, either with or without a blast of hot or cold air.
The final result of any of the above operations is the production of carbonic
oxide more or less pure or a mixture of carbonic oxide and carbonic acid or of
carbonic oxide and hydrogen or a mixture of all three gases, together with any
compounds of sulphur or nitrogen or other elements which may be present as
impurities in the materials employed.
The gaseous products formed in the manner above set forth may be cooled
and purified in any desired manner with recovery of any by-products produced
and the remaining gas can either be stored in a gas holder or otherwise, or be
passed from the gas holder or direct from the purifiers into a furnace or apparatus
charged with a suitable oxidising mixture or material such as for instance as
oxide of iron or of copper or any other suitable oxidising reagent or reagents.
Firebrick or refractory material may be coated with copper by fusing the oxido
and immersing the broken material in it.
Instead of sending the gases as they come from the regenerative stoves or
from the reducing furnace into the purifiers, or into a gas-holder, they may if
preferred, be sent direct to the oxidising furnace being passed through the latter
by means of a hot-blast fan or blower, or by means of their own pressure, in
either case without being cooled or treated in any manner whatever.
By means of the oxidising process hydrogen is converted into water vapour
and the carbonic oxide is re-converted into carbonic acid whilst any excess of
the latter gas which has passed through the process remains unchanged.
The metallic oxide used as the reagent is reduced either to the metallic state
or to a lower oxide and may be regenerated in the well known manner.
My process requires no retorts and no external heat is employed to the reducing
nor to the oxidising furnaces or apparatus. My regenerative apparatus is
preferably constructed of an iron or steel casing lined with refractory material
and filled with fire-bricks or other refractory material arranged to absorb the
heat and afford passage for the gases, the heating of this apparatus may be
effected by any of the usual means and the working conducted in the well known
manner by alternately heating and when sufficiently heated being employed for
the decomposition of the substances as aforesaid.
In order to keep up continuous working, it is preferable to use three of such
furnaces, two working together to heat each other, the fuel being burned alternately
in each, whilst the other is supplying the necessary hot-blast, and the
third being used for the purpose of heating or decomposing the steam or carbon-
aceous matter.
A convenient construction of my improved furnace is somewhat in the form
of an ordinary blast furnace provided internally with honey-comb brickwork of
the like of refractory material and having charging doors at the top and dis-
charging doors or outlets below, together with suitable connections for the con-
venience of the gaseous products to and from the apparatus in the usual manner.

page_text: I do not however confine my invention to this specific form of apparatus
apparatus may be used for the same purpose.
Where carbonic acid alone, or steam alone, or a mixture of these two gases
is used as the raw material, necessitating the use of a separate reducing furnace,
the mode of construction which I prefer is to build the six furnaces, namely
three regenerative furnaces, one reducing furnace, and two oxidising furnaces
in one block, that is to say, a double line of three furnaces, the outer wall or
casing being divided into six compartments, so that the three regenerative
furnaces form one side, and the two oxidising furnaces the corner furnaces of the
second line, the reducing furnaces being placed between these latter furnaces.
Any other arrangement calculated to facilitate working may be adopted, and
the arrangement will also vary with the capacity of production of the plant, the
best construction being such that the passages for the highly superheated gases
from one furnace to the other are as short as possible, to avoid expense and loss
of heat, and also such as to minimise the number of the hot-blast valves used.
1007
An Improved Process for the Manufacture of Carvonic
Apparatus therefor.
I, HERBERT SAMUEL ELWORTHY, temporarily of 69, Guilford Street, London,
are of Messrs. H. S. King & Co., 65, Cornhill, in the City and County of London,
Chemist and Chemical 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: -
This invention has reference more particularly to the manufacture by combus-
tion of carbonic acid free from permanent gases such as nitrogen, for the prepara-
tion of liquefied or solid carbonic acid, for the charging of beverages with or
without previous liquefaction, and to other uses to which such pure carbonic
acid may be adapted, but each of the improvements constituting the invention
is intended to be secured for all the uses to which it may be applicable.
The combustion of carbon in carbonaceous bodies of all kinds yields carbonic
acid, as is well known, when the combustion is effected with a sufficient quantity
of oxygen; but when such combustion is effected by means of air, the resulting
a small proportion,
gases consist mainly of nitrogen. Such a gaseous mixture is wholly unsuited
to many uses to which carbonic acid is applied and even
say, 5% for example, of a non-condensable gas will interfere with its uses for
many purposes. Thus, if it be desired to liquefy the carbonic acid by compres-
sion it is found that it is necessary to employ much higher pressure (at a given
temperature) if even 5% of a non-condensable gas is present. Again, if the
liquefied carbonic acid is to be used in refrigerating machines, the presence of
the non-condensable gas (which may be dissolved in the liquefied carbonic acid)
is apt to interfere with the working of the machine by necessitating higher pres-
sure in compression and thereby impeding the action of the pumps. Further,
if water is charged with impure carbonic acid, the non-condensable gas dissolves
also to a sufficient extent to impair the comestible value of the carbonated water,
as the so charged waters lose their sparkle and sharp taste quickly after opening.

page_text: Moreover, for certain chemical reactions carbonic acid will not answer if it
contain a certain proportion of inert gas.
In each of the cases mentioned the same objection would be encountered,
whether the impurity consists of air, nitrogen, hydrogen or other neutral gas
non-condensable as compared with carbonic acid gas.
In accordance with the present invention, carbon (in the form of coke, char-
coal, petroleum or other carbonaceous substance or substances, herein termed
the fuel for convenience of reference) is burnt without air by converting the
said carbon (first) by steam or carbonic acid or a mixture thereof into carbonic
oxide (CO) free from non-combustible non-condensable gas and (second) oxidi-
zing completely this carbonic oxide and any accompanying combustible non-
condensable gas by means of a metallic oxide, which is formed again after reduc-
tion so that the same charge can be repeatedly utilized.
In order to convert carbon into carbonic oxide by means of steam or carbonic
oxide or mixture thereof, it is necessary to supply heat from an outside source;
and to do so in the most advantageous manner recourse is had (in the present
invention) to contact with the surfaces of fire-brick or other suitable inert bodies
previously raised to a sufficiently high temperature. According to one mode,
the steam or carbonic acid, or mixture thereof is superheated by contact with
such highly heated surfaces before it is brought into contact with the carbonaceous
substance.
According to another mode, the steam or carbonic acid or mixture thereof and
the fuel are passed together over the highly heated inert surfaces.
These two modes can be combined by admitting part of the fuel to pass with
the steam or carbonic acid or mixture thereof over the highly heated inert sur-
faces in such manner that the escaping products are so highly superheated that
on contact with a further portion of fuel a further amount of carbonic oxide is
formed.
In either or any mode the inert surfaces must supply heat enough to compensate
for that which is rendered latent by the decomposition of the steam or carbonic
acid, or both, and the conversion of carbon into carbonic oxide. In other words,
the formation of the carbonic oxide develops a certain quantity of heat; but
the decomposition of the steam or carbonic acid, or both (the oxidizing gas as
it may be shortly expressed) renders latent a larger amount of heat than is thus
developed; the excess is supplied by contact of the oxidizing gas or of the oxidi-
zing gas and fuel with the highly heated surfaces. The fuel, when superheated
steam or carbonic acid is brought in contact therewith, may, and indeed should,
itself be at a high temperature.
In many places, and perhaps under most conditions, it may be advisable to
use coke or charcoal or other solid fuel massed in a stack or cupola, as customary
in the making of water gas. At the beginning such coke or other solid fuel
may be brought to incandescence by an air blast: but by suitably superheating
the steam or carbonic acid or mixture thereof, the formation of carbonic oxide
can afterwards be made continuous, without requiring the charge to be blown
with air at short intervals. Such periodic blowing with air would be very
objectionable; because, after each application of an air blast, the carbonic oxide
obtained would be mixed with the non-condensable non-combustible nitrogen
for a considerable time, until in fact the nitrogen which would remain
in the fuel when the air blast is stopped should have been all
removed. These losses are avoided by supplying the heat by means of inert
bodies. If the temperature of the latter fall, they can readily be raised again to
a proper temperature; and if in the heating the nitrogen is left between them
it can readily he swept out by a blast free from non-condensable non-combustible
gas, as of steam or carbonic acid for example.
In order to effect the complete combustion of the carbonic oxide into carbonic
acid, by a metallic oxide or oxides, the latter may be arranged in various ways.
What is considered the best way, itself forming a special improvement, is to

page_text: abine the oxide with fragments of an inactive
stitute a carrier for the oxide.
Or less
The invention also comprises certain other features and certain improvements
apparatus as hereinafter set forth.
The accompanying drawing which forms part of the specification is a diagram
apparatus which can be used to carry out the process improvements of the
esent invention and which embodies the improvements in apparatus.
The furnace, D, which constitutes a generator of carbonic oxide and which
shown in the form of a cupola, although other forms may be used, is supplied
ith coke or other solid fuel; or, according to another mode of working, it may
e filled with brick or other inert refractory material, or it may be cut out or
isused entirely. It is shown as connected on the one side by the flue, J, with
he hot blast stoves, B and C, and on the other by the flue, P J, with the two
xidizing furnaces, E F, charged with a body, E, F, of an oxidizing or oxidiz-
ble metal, which most advantageously is distributed over the fragments of an
nactive or less active refractory substance, as a carrier. This carrier is particu-
arly useful in connection with an active substance, like copper oxide, which is
fusible.
Between each of the hot blast stoves and the flue, J, is a valve, K L, respec-
tively, so that either stove can be connected with the flue, J, while the other is
cut off, the object being to use the stoves alternately. This is necessary with
the regenerating type of stove, since such a stove has to be shut off while it is
being reheated.
Each stove consists of a chamber filled with the open brickwork usual in
regenerating furnaces and provided with the valved inlet, X' or X³, for the
admission and valved outlet, K or L, for the escape of the steam or carbonic
acid or mixture thereof, and also with a valved inlet, Wb or Wo, for the admis-
sion of the reheating gas, the valved air pipe, U or V, for the admission of air
for burning the reheating gas, and a valved passage, Gb or G°, for the escape
of the products of combustion.
The valved air pipes lead from a hot blast stove, A, which, as shewn, is also
of the regenerating type, and consists of a chamber filled with the usual brick-
work and provided, in addition to the valved air pipes, U and V, for delivering
the hot air blast to the chamber, B and C, with the valved inlet Wa, for the gas
to reheat chamber, A, a valved passage, G¹ or G2, for the escape of the products
of combustion, and means for admitting air at top or bottom of the chamber,
as may be desired.
These means, most advantageously, are constituted by four way reversing
valves, HH, provided each with an air inlet, h, and an outlet, H, for the products
of combustion and interposed one between the tops of the chambers A and B,
the other between the tops of chamber A and C. Between each of these valves
and the tops of the corresponding chambers are additional valves cach in the
form of an inverted cup, g, whose edges are sealed by dipping into a gutter g¹
which is filled with melted lead or other suitable metal. If the inverted cups g
15 in the passages Gb and G¹ are raised, and the valve H is in the position shewn
in full lines, air can enter the top of the chamber A, and by turning the valve H
to the position shewn in dotted lines, air from the inlet h can enter the top of
chamber B and will enter the bottom of the chamber A, by the passage U, after
passing through the brick-work of chamber B. Similarly, if the inverted cups
50 in the passage G2 G are raised, those in the passages G1 Gb being shut down,
air can enter the top of chamber A, from the inlet h, and passage G2, when valve H
is in the position shewn, by turning the said valve to the position shewn in
dotted lines, the air from the inlet h will first enter the top of chamber C and
after it has passed through the brickwork in this chamber it will enter the botton
55 of chamber A, by the passage V.
With this arrangement the dotted openings b° 22 would be unnecessary, bu
desired the four way valves could be omitted, and valved passages openin

page_text: at z² and z² respectively might serve to admit air to the top and bottom respec-
tively. Or the air could be admitted to the top of the chamber A by an open-
ing at zb and to the bottom of said chamber by the passage U or V, the air in
this case first entering the chamber, B or C, at 2ª or 2° and descending through
the brickwork therein before it goes through the passage U or V, into the bottom
of chamber A.
The connection of the carbonic oxide generator D with the oxidizing fur-
naces, E F, may be direct or through gas purifying apparatus, or both forms
of connection may be provided. The flue P J is shewn as opening directly into
the bottom of the oxidizing furnaces E F, through the valved branch pipes S¹Q,
but such direct connection is advisable only in case the fuel in the furnace D,
is a very pure carbon. Ordinarily the carbonic acid from the flue J would be
passed through one or more coolers and scrubbers or other purifying apparatus
to the pipe R, from which it passes into whichever of the furnaces, E F, has its
charge E¹ or F¹, in an oxidized condition. After or before passing through the
purifying apparatus the carbonic oxide may be stored in gasometers. Blowers
can be employed to force the carbonic oxide into the furnaces.
Each of the oxidizing furnaces has a valved inlet N or N₁, for admitting air
or steam thereinto for oxidizing its metallic charge E¹ or F1; and each of said
furnaces also has an outlet e or f, for the residual gas and for the carbonic acid
gas. As shewn, one opening is represented. This may serve for both gases;
but of course the passage leading therefrom would be used, one for the residual
gas, the other for the carbonic acid gas.
The charge E or F may consist of fragments of brick or other refractory
material coated or combined witli copper oxide. This is considered the best
material; but other oxides, and other ways of supporting the oxide can be used,
so long as aeriform fluids have access to the metallic matter (oxidized or de-
oxidized, as the case may be).
What is considered the best way of coating or combining the copper oxide with
the refractory material is to fuse the copper oxide, which can be done in any
ordinary glass furnace, such as a tank furnace, for instance, and to immerse
fragments of fire-brick therein. To prevent the oxide of copper being reduced by
small amounts of organic matter present in the firebrick or by the gases of com-
bustion, ammonium or sodium nitrate in small amounts may be added to the
bath of fused copper oxide from time to time. By making the nitrate adhere
to the fragments of firebrick, it can be introduced with the latter.
Having charged the furnace D with coke and the furnaces E F with a material
which is capable of being oxidized or deoxidized, preferably fragments of fire-
brick coated with copper oxide, the said furnaces and also the chambers, ABC,
are raised to a high temperature. To ignite the charge of solid fuel in the
furnace, D, a fire is started in the bottom of said furnace, the top T is raised, and
air from one of the stoves A B C is blown in until the mass of fuel is at a white
heat. At this time the valves S and S2, are closed, also the valve L (if the air
is taken from the chamber B) and the valve U. The air can be admitted to the
chamber B, through the valve H¹ and passage Gb, by turning the valve H¹ to.
the dotted position and raising the inverted cup in the passage Gb; or it can
be admitted to B by the opening z, if this be used.
To heat the furnaces E and F air may be introduced at N and N', and fuel
in the form of carbonic oxide or of other combustible gas through the branches
of pipe R.
To raise the temperature of chambers, A B C, gas (producer gas for example)
from the inlet W is burnt among the brickwork of the chamber A by air intro-
duced from the chamber B (let us say) or from the passage 22, if this be used.
By raising the inverted cups g in the passages G¹ Gb, and turning the valve H¹
to the dotted position, the air may descend through the chamber B and enter
the chamber A by the passage U: and the products of combustion can escape
to the chimney I through the passage G¹ and the flue F.

page_text: After a proper time (half an hour or more or less) by turning the valve H¹
to the position represented, the air will go by the passage G¹ to the top of the
chamber A while products of combustion from the chamber B can escape to the
chimney I by the passage Gb and the flue H. At this time the gas at W* is cut
off and is admitted at Wb into the chamber B. Combustion now takes place
among the brickwork of the chamber B. After a proper time the valve Ĥ' is
reversed, and gas from the opening W is burnt among the brickwork of the
chamber A, by a hot blast of air from the chamber B. In time after changing
the position of the valve H¹ as often as necessary, both chambers are brought
to an intense heat.
In like manner the chamber C is heated, the chamber A serving to heat the air
which is introduced by the passage V to the bottom of the chamber C, and which
serves to burn the gas which is introduced at the opening W. During this
operation the passages G1 Gb would be closed and the passages G2 G° would be
opened; and the valve H2 would be shifted from time to time.
Assuming that chamber B is heated to, say, about 1,500° C., and that the
passages zWb and U are closed, the valve K is opened and also the valves 82 S³.
Steam or carbonic acid or mixture thereof is then introduced through the pipe X¹
to drive out the non-condensable and non-combustible nitrogen from the cham-
ber B. It passes off to a waste flue or to any desired receiver. When all of the
nitrogen has been expelled, the valve S2 is closed and the valves M and S opened,
the top T being shut down. The steam or carbonic acid or mixture thereof now
passes into the incandescent fuel in the furnace D, and is decomposed, the products
of decomposition passing out by the flue P J and valve S3, to any suitable
receiver. When the nitrogen, left by the air blast in the interstices of the fuel
in the furnace D has been carried off, the products of decomposition will consist
of carbonic oxide, free from non-condensable and non-combustible gas, the only
other gases being hydrogen (from the steam if this is used) and ammoniacal
sulphur and hydrocarbon compounds (from the solid fuel in the furnace D if this
is not sufficiently pure). These bodies are either combustible or condensable,
and therefore removable at once or after combustion in the oxidizing furnace.
Hence they are not open to the objection which arises from the presence of a
non-combustible non-condensable gas like nitrogen.
In order that the decomposition in the carbonic oxide generator. D may take
place as near as may be without loss of temperature, the steam or carbonic acid
or mixture thereof is heated by contact with the inert surfaces of the firebrick
in the stove B so much above the temperature necessary for the decomposition
in the carbonic oxide generator that it carries with it from said stove B enough
heat energy to compensate for that which is rendered latent by said decomposi-
tion, without lowering the temperature below the decomposing point.
After a time, however, the temperature of stove B when of the regenerating
type as shewn, becomes insufficient properly to superheat the steam or carbonic
acid or mixture thereof. When this occurs, the valve K is closed; and the brick-
work of the stove C, being at the highest temperature used, the valve L and
pipe X are opened, so that this stove now supplies the superheated blast of steam
or carbonic acid or mixture thereof to the carbonic oxide generator. Before,
however, this steam or carbonic acid or mixture thereof is admitted to the fur-
nace D it is allowed (the valve M being temporarily closed) to blow off through
the flue J J and valves S2 S3 until the nitrogen is displaced from chamber C and
flue J J. The valve M is now opened, the valve $2 is closed, and the superheated
steam or carbonic acid or mixture thereof from the chamber or regenerating
stove C is admitted to the furnace D. While using the stove C the brick work
of stove B is reheated by the combustion of gas from opening Wb by means of a
hot blast from the stove A. In this reheating the valve H¹ is shifted once or
oftener in the manner before explained. Thus the chambers B and C
alternately as hot blast stoves for superheating the steam or carbonic acid or
mixture thereof which is supplied to the furnace D; while the chamber A serves
serve

page_text: as a hot blast stove for supplying hot air alternately to the stoves B and C, for
reheating the same.
The carbonic oxide from the generator D free from non-condensable nou-
combustible gas, is passed through whichever of the furnaces E F is ready to
receive it, the said carbonic oxide being, when desired, first passed through one
or more coolers and scrubbers or other purifying apparatus, or, when this is not
desired, and the carbonic oxide is sufficiently pure, being admitted directly to
the oxidizing furnace.
Assuming that the furnace E is ready, the valve S, and the passage S may be
opened for a direct admission; or the passage S¹ being closed the carbonic oxide
passing away by the flue J and valve S3, may be passed through appropriate
purifying apparatus and afterwards be introduced through the pipe R, and its
left hand branch.
The carbonic oxide or carbonic oxide and other combustible gas in the products
of decomposition from the furnace D in passing through the furnace come in
contact with the metallic oxide therein, and combine with oxygen of said oxide
to form carbonic acid or carbonic acid and water. The contact with the said
oxide should be sufficient completely to burn all the combustible gas, the resulting
product being simply carbonic acid or carbonic acid and vapour of water free
from non-condensable gas.
After a time the furnace F is utilized, the charge E¹ in furnace E being re-
oxidized by passage of air or steam from the inlet N, through the said charge.
If air is used the operation is completed by a current of steam, so that no nitrogen
is left in said furnace..
When the charge in the furnace F has been sufficiently deoxidized, the delivery
of carbonic oxide thereto is stopped and the charge is reoxidized either by air
or steam or mixture thereof; and the furnace E is utilized while this is being
done.
The carbonic acid gas from the oxidizing furnace is passed through coolers
for lowering its temperature and removing therefrom the vapour of water which
it may contain; and, being free from any non-condensable gas, it is then ready
for liquefying by compression, for charging beverages, or for use in the gaseous
state.
If it be desired to fill the cupola, D, with inert refractory material, instead
of with solid fuel, the fuel for decomposing the steam or carbonic acid or mix-
ture thereof may be introduced into the superheated steam or carbonic acid or
mixture thereof on its way to the furnace, D), the superheating in the cham-
ber, B or C, being sufficient to supply the heat for effecting decomposition without
lowering the temperature of the furnace, D.
Instead of bringing the fuel into contact with the steam or carbonic acid
or mixture thereof after superheating the latter, they may be passed together
over the highly heated inert surfaces, which supply the heat rendered latent by the
decomposition. In the drawing the pipes, Y¹ Y2, are for introducing liquid,
vaporized or gaseous hydrocarbon of any suitable description, petroleum for
example. Solid fuel in powder could also be introduced alone or in connection
with other forms. It might be injected by the blast of steam or carbonic acid or
mixture thereof. The furnace, D, need not be used; and it could either be dis-
pensed with entirely or be simply shut off by closing the valves, M and S.
The furnace D filled with solid fuel may be used in conjunction with the
delivery of fuel into the hot blast stove, the decomposition of the steam of carbonic
acid or mixture thereof being effected partly in the stove and partly in the fur-
nace, D.
After the decomposition has been carried on in the stove B, the brick-work
therein loses its temperature until it falls below the decomposition temperature.
Just before this point is reached the supply of fuel and of steam or carbonic acid
or mixture thereof is transferred to the stove C, the chamber B, being now re-

page_text: heated by producer or other suitable gas from the opening Wb, and a blast of hot
air from the stove A, in the manner hereinbefore explained.
The carbonic oxide free from non-condensable non-combustible gas which is
generated in the chambers, B and C, is passed through the oxidizing furnaces EF,
in such manner that all the combustible gases are completely consumed, leaving
only carbonic acid free from non-condensable gas. The carbonic oxide, unless
sufficiently pure, should, and it in any case may, be passed through purifying
apparatus before it is passed through the oxidizing furnace. The principal im-
purity (as is also the case when the steam or carbonic acid or mixture thereof
is decomposed by the solid fuel in the furnace 1),) would be ammonia, which
would be decomposed in the oxidizing furnace with the elimination of nitrogen.
Washing the carbonic oxide with water or dilute acid would remove the ammonia.
Although the pipe, J, is for convenience shewn exposed and unlined, this is
preferably made of larger diameter, and internally lined with refractory material,
and may also be coated outside with some non-conducting composition. The
valves exposed to a high temperature are of the hot blast type, in which a water
current is caused to circulate through the valve and also through the seat to
prevent fusion.
It is believed to be of the highest industrial importance to generate the carbonic
oxide free from non-condensable non-combustible gas and to effect a complete
combustion by the metallic oxide in the oxidizing furnaces, so that the carbonic
acid thus obtained shall be free from non-condensable gas. In the working of
the apparatus described, with solid fuel in the furnace, D, some carbonic oxide
is produced (at the beginning of an operation) which is mingled with nitrogen;
and it may sometimes happen that by carelessness of the attendant a complete
combustion is not effected and more or less carbonic acid is obtained which is
mingled with hydrogen or carbonic oxide, both of which are non-condensable.
Such impure carbonic oxide and carbonic acid may be used as fuel, but it may
in some cases be preferred to prepare pure carbonic acid therefrom. For this
purpose carbonic oxide can be passed through an oxidizing furnace, and the
carbonic acid thus generated can then be separated from the non-condensable gas
by any known or suitable means, such as solution in water under pressure and
evaporation therefrom. In the case of the impure carbonic acid a like separation
can be effected; or the impure carbonic acid, when the non-condensable impurity
or impurities are combustible, may be passed again over metallic oxide to effect
a complete combustion.
Heretofore it has been proposed to separate carbonic acid from non-condensable
gas in admixture therewith; but, as far as I am aware, this step was never used
in combination with the two operations of (first) decomposing steam or carbonic
acid or mixture thereof and (second) effecting a combustion of the carbonic oxide
by metallic oxide. The resulting gaseous mixture consists mainly of carbonic
acid, and thus differs essentially from ordinary products of combustion which
are mainly composed of nitrogen. When carbonic acid predominates, it is much
easier to effect a separation of the same than where it is mixed with an excess
of nitrogen. When the step of separating the carbonic acid from non-conden-
sable gas in admixture therewith is used in the combination just mentioned,
some air might be admitted during the decomposing operation into the stove, A
or B, or into the furnace D, whether this contain solid fuel or be filled with inert
refractory material; and some air might be admitted into the furnace, E or F,
during the oxidation of the carbonic oxide to carbonic acid; but this is not
recommended. For some uses, where carbonic acid above a certain degree (which
is always more than half carbonic acid) is required, the carbonic acid may be
obtained in admixture with the (for such purposes immaterial or comparatively
unimportant) amount of non-condensable gas, the generation of carbonic oxide
and the oxidation with metallic oxide may be employed without any separation
of the carbonic acid from the smaller volume of non-condensable gas mingled
therewith.

page_text: It will be understood that in referring to carbon in the claims following it is
intended to include coke, charcoal, anthracite coal, bituminous coal, crude
petroleum, petroleum tar, other petroleum products, coal tar, wood tar, asphaltum,
bitumens, natural or artificial gas containing carbon compounds, and any other
suitable form of carbon, combined or uncombined.
If it should be desired, the carbonic acid free from non-condensable gas can,
of course, be subjected to a treatment calculated to effect a separation of the
carbonic acid from non-condensable gas mixed therewith. Such a treatment
would be a solution in water and evaporation from such solution; and it might
perhaps be useful in some cases for a more assured state of absolute purity to
use such treatment, notwithstanding that the carbonic acid may be free from
non-condensable gas, or practically so, for purposes of liquefaction.
Certain hydrocarbon gases, such for instance as natural gas, may be sent through
the regenerative stoves, B or C, and thence into the oxidizing furnaces, E or F,
without admixture with steam or carbonic acid, but it is preferable to mix a
certain proportion of one or other of the two latter gases with the hydrocarbon.
The hydrocarbon gas might also be sent direct into the oxidizing furnaces, with-
out first passing through the regenerative stoves, but in this case again it would
be preferable to mix it with a certain proportion of carbonic acid or steam, more
especially the latter. Where the hydrocarbon is sent direct into the oxidizing
furnaces, it is a diffcult matter to get entirely rid of the odour, and this may
unfit the gas for commercial use for the manufacture of aerated beverages or ice..
Where the production of carbonic acid free from non-condensable gas is desired
as the direct result of the oxidization, a complete combustion must be effected
by the metallic oxide, and the gas or vapour which is passed into the oxidizing
furnace must be free from non-condensable non-combustible gas. If, however,
the product after leaving the oxidizing furnace is to be subjected to a treatment
calculated to separate the carbonic acid from condensable gas, or if the carbonic
acid would be suited to the use intended, notwithstanding the presence of a non-
condensable gas which would unfit it for liquefaction, the freedom from non-
condensable non-combustible gas of the gas or vapour which is supplied to the
oxidizing furnace and a complete combustion of said gas or vapour by metallic
oxide are not essential, the content of carbonic acid in any case exceeding the
content of non-condensable gas of the gaseous product which results from the
oxidation with metallic oxide.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The process for making carbonic acid free from non-condensable and non-com-
bustible gas, consisting essentially in passing steam or carbonic acid or a mixture
thereof heated to a high temperature by contact with heated inert surfaces, over
incandescent combined or uncombined carbon, forming carbonic oxide (CO)
and in passing the carbonic oxide thus obtained, with or without intermediate
purification, over extensive surfaces of heated metallic oxide for the purpose of
oxidizing the CO into CO2 without the admixture of non-condensable and non-
combustible gas.
2. The modification of the process set forth in Claim 1 consisting essentially
in passing a mixture of steam with or without carbonic acid, and a hydrocarbon
in the gaseous state over highly heated inert surfaces to produce carbonic oxide
an hydrogen gases, and then subjecting the said products to the action of a
metallic oxide for the purpose of oxidizing them to carbonic acid CO2 and water
vapour H2O respectively.
3. The modification of the process set forth in Claim 1 consisting essentially
in passing carbonic acid and a hydrocarbon in the gaseous or liquid state over
highly heated inert surfaces to produce carbonic oxide and hydrogen gases and
then subjecting the said products to the action of a metallic oxide for the pur-
pose of oxidizing them to carbonic acid and water vapour respectively.

page_text: 4. The apparatus for the production of carbonic acid free from non-condensable
and non-combustible gas substantially as set forth in Claims 1, 2, and 3, con-
sisting of the combination of the generating furnace D connected by the pipe J
and valves M L and K, or of any other suitable CO producing device, with the
regenerative hot blast stoves B and C (with superheater A) on the one hand, and
with the oxidizing furnaces E F by means of the pipe P and valve S, or by
means of the pipe J and valve S² on the other hand, with or without the inter-
position of purifying apparatus whereby the continuous production of pure
carbonic acid free from deleterious mixture is obtained.
•
5. In apparatus of the kind set forth in Claim 3, the series of hot blast
stoves BA C, the middle stove A being connected to B by the valve U and by
the valved passage Gb G¹ connected to the chimney flue H and controlled by the
reversing valve H, and to C by the valve V and by the valved passage G2 G°
connected to the chimney flue H and controlled by the reversible valve H2
respectively, and provided with the auxiliary inleta and outlets z zb z z² and
the heating gas inlets wwbw steam injecting pipes X1 X2 and the hydrocarbon
injecting pipes Y¹ Y2 respectively for the purpose above set forth.
6. In apparatus of the kind set forth in Claim 3 the oxidizing stoves E F
filled with refractory material F¹ coated or combined with a metallic oxide
and provided with valved inlets N N' outlets e and f and valve connecting pipe R
for the purpose above set forth.
7. In combination, the improved apparatus for generating carbonic oxide,
with or without admixture of carbonic acid or of hydrogen and for oxidizing
the same without intermixture of non-condensable or non-combustible gas in one
continuous operation substantially as described and illustrated in the accom-
panying drawing.
1 1
011
1
0 T
1000
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant..