New or Improved Processes for the Manufacture of Gas from Water Vapour, and for Purification and Separation of Mixed Gases.
Year: 1892

page_text: Date of Application, 4th May, 1892-Accepted, 18th June, 1892
COMPLETE SPECIFICATION.
New or Improved Processes for the Manufacture of Gas from
Water Vapour, and for Purification and Separation of Mixed
Gases.
I, ALFRED LONGSDON, of 75 Old Broad Street, in the City of London, Civil
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 (which invention has been communicated to me by the
firm of Fried. Krupp of Essen in the Empire of Germany, Cast Steel
Manufacturers) :-
-
Gas as previously manufactured by conducting water vapour over highly heated
coke or other suitable carbonaceous fuel is, owing to the large proportion of
carbonic oxide or carbon monoxide present, unsuitable for many purposes, and
has not generally been adopted for domestic use on account of its poisonous
properties.
The hereinafter described process has for its object to obtain a gas nearly
completely free from carbonic oxide or carbon monoxide, and to produce from
water vapour and coal in the simplest possible way two products, one practically
pure hydrogen gas and the other practically pure carbonic acid gas or carbon
dioxide.
This process is based upon the fact that the reaction between water vapour and
carbonaceous material at low temperaturės―below 1000° centigrade,―takes place
more in the sense of the equation
C + 2 H,O = CO,+4 H
i.e. one part of carbon + 2 parts of water = 1 part of carbonic acid gas + 4 parts
of hydrogen gas, and that therefore at a low temperature a gaseous mixture is
obtained containing more carbonic acid gas or carbon dioxide and hydrogen gas,
and less carbonic oxide or carbon monoxide than when the reaction takes place at
a higher temperature. The conditions necessary for such a re-action to take place
exclusively, could not hitherto be fulfilled; there always was obtained considerable
quantities of carbonic oxide or carbon monoxide, which were mixed with the gas,
the production of which is explained by the equation
C +H,O=CO + 2 H
i.e. one part of carbon + 1 part of water = 1 part of carbonic oxide + 2 parts of
hydrogen gas, or
CCO = 2 CO

page_text: When the above named carbonaceous material is impregnated for instance with
a solution of carbonate of potassium, and the dried mass is brought to a red heat
in a retort or in other suitable apparatus, and superheated steam or ordinary water
vapour is conducted over same, the production of carbonic oxide or carbon
monoxide is nearly completely prevented, and the gas produced contains carbonic
acid gas or carbon dioxide and hydrogen gas with only very small quantities of
other gases.
The analysis of such a raw gas obtained from peat-coke gave the following
result:-
Carbonic acid gas
Carbonic oxide
Hydrogen gas
Hydrocarbon gas-CH4"
Nitrogen gas
Oxygen gas
26.4%
1.2°
10
62.0 %
2.3 °
6.5%
1.5%
This raw gas when produced would possess a high calorific value, and after the
expulsion of the carbonic acid gas or carbon dioxide, would consist chiefly of pure
hydrogen gas. The above proportions would have been of course still more
favourable, if the accidental impurities and atmospheric air indicated by the
analysis could have been avoided.
The raw gas produced in the above described manner is as such, already fit for
industrial use owing to its calorific value.
The further process consists in separating from each other the two gases, of
which the raw gas chiefly consists, viz.-carbonic acid gas or carbon dioxide and
hydrogen gas, and in obtaining each of these two gases separately by absorbing
the carbonic acid gas or carbon dioxide from the hydrogen gas, and then extracting
again from the absorbent mass the carbonic acid gas or carbon dioxide.
For separating from the raw gas the carbonic acid gas or carbon dioxide mixed
therewith, all the hitherto known absorbing agents for carbonic acid gas or carbon
dioxide, such as lime, alkalies, etc. may be employed, but in order to carry out the
separation economically and to render the carbonic acid gas or carbon dioxide
valuable for other purposes, the hereinafter described process is employed, which
process is based on the production and subsequent decomposition of bicarbonates of
the alkalies.
In order to carry out this improved process of absorption, a purifying mass is
made by mixing coarsely powdered wood, charcoal, and an organic substance easily
decomposible by heat, such as meal, molasses, sawdust etc. with a concentrated
solution of carbonate of potassium or of sodium, evaporating to dryness and heating
inclosed vessels until the mass glows. Thus a porous pumice-like mass is obtained,
which forms, when moistened, an extraordinarily efficacious absorbent for carbonic
acid gas or carbon dioxide.
For a similar purpose, instead of my improved mass, coal or coke impregnated
with the said solution may also be employed.
The mass prepared in the manner above described is placed in a suitable
apparatus and moistened with water. The mixed gases are to be conducted over
the mass, which will entirely absorb the carbonic acid gas or carbon dioxide, the
hydrogen gas passing over unchanged may be collected in a store receiver or may
be immediately led away for use.
When the purifying mass is saturated, in order to obtain the absorbed carbonic
acid gas or carbon dioxide, and at the same time regenerate the mass, it is only
necessary to cause a current of water vapour to pass through the apparatus, or in
other ways to decompose the produced bicarbonate, for instance by heating, and
thus the mass may be renewed and the process repeated at pleasure.
If the gas to be purified contains other gases capable of being absorbed by the
carbonate, the purifying process must correspondingly be modified, which modifi-
cation depends on the character of the gas to be removed,

page_text: By means of this process carbonic acid gas or carbon dioxide may be removed
also from other gases and be rendered useful for industrial purposes.
Besides the process hereinbefore described for obtaining hydrogen gas and
carbonic acid gas, or carbon dioxide, there is another process particularly suitable
for separating carbonic acid gas or carbon dioxide from hydrogen gas, water gas,
heating gas, and other gases containing carbonic acid gas or carbon dioxide, which
also may be utilized for obtaining pure carbonic acid gas or carbon dioxide.
This other process is based upon the fact that it is possible to absorb carbonic
acid gas, or carbon dioxide, by alkaline earths when they are brought to a red heat,.
and to expel it again by means of water-vapour. For this purpose, lime as
magnesite and dolomite in a burnt or unburnt condition may be employed, but
burnt lime or oxide of calcium such as it is obtained by burning limestone, marble,
etc. is particularly advantageously employed. The advantage of this process,
compared with other similar processes, consists in that the process can be carried
out quite continuously and that the gases and the absorbents act the one on the
other in a dry condition, so that the application of aqueous solutions is entirely
avoided.
To carry out the process, a retort or other similar suitable receiver is charged
with lime, limestone, or with such bodies, which in burning leave a residue of oxide
of calcium, the material is then brought to a bright red heat and water-vapour,
(if required in a superheated condition), is conducted over it until the carbonic
acid gas or carbon dioxide is expelled. When the burnt lime is still at a red heat,
hydrogen gas containing carbonic acid gas or carbon dioxide, or another gas con-
taining carbonic acid gas or carbon dioxide, is conducted over it, a quick absorption
of carbonic acid gas or carbon dioxide, and a purification of the mixed gas from
carbonic acid gas or carbon dioxide will take place. When the lime is saturated,
the admission of mixed gas is cut off and the carbonic acid gas or carbon dioxide
absorbed is expelled by causing water vapour to pass over the absorbent substance.
The expulsion and absorption of carbonic acid gas or carbon dioxide can be
continued in an alternating manner, until after some time, the action of the lime,
owing to the alteration of its pure condition by dust etc., has become too weak,
and a supplementary or renewed charge is required. The temperature necessary
for the absorption of the carbonic acid gas or carbon dioxide, and for its expulsion
by water vapour, are very nearly the same, and in consequence thereof the whole
process may be carried out without considerable variations of temperature and with
a very small loss of heat.
The escaping carbonic acid gas or carbon dioxide can easily be re-collected, and
utilized then for other purposes.
In lieu of burning lime in retorts, already previously burnt lime may of course
also be used, and in this case the first part of the process is to be modified
accordingly.
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 process for commercially obtaining a raw gas (composed chiefly of
hydrogen and carbonic acid gas or carbon dioxide) by passing water vapour over
carbonaceous materials, such materials having been previously impregnated with a
substance which prevents the process being carried on at such a heat as will
produce an undesirable reaction, substantially as hereinbefore described.
2. The processes of separation of the raw gas into its component gases, whereby
the carbonic acid gas or carbon dioxide is absorbed and subsequently obtained
separately as set forth.
3. In order to absorb and obtain carbonic acid gas, or carbon dioxide, from gas
mixtures containing carbonic acid gas or carbon dioxide, the application of a porous
mass containing the carbonates of alkalies, and the 'action of which is based on the
fact that carbonic acid gas or carbon dioxide is capable of being absorbed very

page_text: freely by the wet mass, and that the bicarbonate so produced is decomposable, by
water vapour or by heating, into pure carbonic acid gas or carbon dioxide, and
carbonate, so that a continuous repeating of the process of absorbing and
developing carbonic acid gas or carbon dioxide can be obtained, substantially as
described.
4. A continuous process for expelling or obtaining carbonic acid gas or carbon
dioxide from gaseous mixtures consisting in conducting the gases to be purified
over alkaline earths-in particular lime-brought to a red heat, and in expelling
again in the red heat the carbonic acid gas or carbon dioxide so absorbed by
means of water vapour, so that the remaining lime may be used without any
interruption for the further absorption of the carbonic acid gas or carbon dioxide,
and for the subsequent expulsion of the same, substantially as described.
Dated this 4th day of Mar 1809
BREWER & SON,
33, Chancery Lane, London, Agents for Applicant.
BREWER & SON,
33, Chancery Lane, London, Agents for Applicant.