IMPROVEMENTS IN THE MANUFACTURE OF HYDROGEN
Year: 1884

page_text: I, ROBERT LEHMANN, of 82, Turnmill Street, London, Merchant, do hereby
declare the nature of said Invention for IMPROVEMENTS IN THE MANUFACTURE OF
HYDROGEN, a communication to me from abroad by Jacob Oettli, of Cossonay,
Switzerland, Professor of Chimistry, to be as follows :—
This invention relates to the manufacture of hydrogen by the decomposition of
aqueous vapours, and has for its object to remove the difficulties hitherto
encountered in this manufacture and thereby to reduce the cost of the product.
For this purpose I introduce into the tube or retort in which the aqueous
vapour is decomposed by heat, hydrogen previously produced by any suitable
method, in order that the formation or reproduction of water from the hydrogen
and oxygen set free by decomposition may be prevented by the presence of an
inert gas.
I also connect the tube or retort with an exhaustor, air pump or equivalent
apparatus for producing a comparative vacuum in the same and maintaining it
during the process of manufacture.
In order to facilitate the decomposition of steam at the beginning of the
operation, the decomposing pipes, preferably made of refractory earthenware, may
be filled with iron in a fine state of division (for instance filings, shavings or
spongy iron), which when highly heated, will combine with the oxygen contained
in the steam.
The whole process may be carried out by means of apparatus arranged as
follows:
A furnace heated by coke or other suitable material (which may subsequently
be replaced by a portion of the hydrogen obtained by my process) contains several
horizontal tubes of fire-proof earthenware connected at one end with a mixing
chamber and at the other end with an exhaustor.
The mixing chamber communicates with a steam generator and with a hydrogen
receptacle or generator adapted to give a continuous supply of hydrogen during the
process. The exhaustor is adapted to draw gases out of the decomposing tubes or
from an intermediate chamber connected with the latter, and to force them into a

page_text: gas-holder, from which the resultant gases (hydrogen and oxygen) are conducted,
to a separator.
The separation of the oxygen from the hydrogen is preferably effected by means
of membranes, which allow the gases to pass in inverse proportion to the square
root of their densities. As the density of hydrogen is only about 1 of that of
oxygen, these gases will pass through a diaphragm in the proportion of 4 to 1, so
that by repeating the operation several times an almost complete separation may
be obtained.
After the process has been fairly started, a part of the hydrogen obtained may
be used, instead of coke, for heating the decomposing tubes in the furnace and the
steam generator, as well as for supplying the hydrogen intended to be mixed with
the steam.
The proportion and pressure of gases in the mixing chamber may be regulated
by valves or cocks interposed in the pipes communicating with the steam generator
and the hydrogen receptacle, or in a conduit between the mixing chamber and the
retort.
The membranes for separating the gases are preferably made of fine wire gauze
and parchment, so that at each separation the gases must pass through a double
strainer formed by a sheet of wire gauze and a sheet of parchment.
The gases may also be separated by dipping into the mixture one or more
pieces of porous material, such as gas carbon or coke, and removing it again after
it has become charged with gas.
In some cases the resulting gases (oxygen and hydrogen) may be used
unseparated.

page_text: Improvements in the Manufacture of Hydrogen.
I, ROBERT LEHMANN, of 82 Turnmill Street, London; Merchant, do hereby
declare the nature of this Invention, a communication to me from abroad by
Jacob Oettli, of Cossonay, Switzerland, Professor of Chimistry, and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:—-
This invention relates to the manufacture of hydrogen for industrial purposes,
by the decomposition of aqueous vapours (steam) and more especially to the ways
of removing the difficulties, which have hitherto encountered in attempting to
produce hydrogen at a low cost and by an industrial process.
The principles of this process are the following:
a, The decomposition of aqueous.vapour by introducing it into highly heated
tubes of refractory earthen ware, in which a more or less complete vacuum has
been previously produced, and which form together a retort of greater volume.or
capacity than that of the vessel from which the steam escapes, so as to obtain a
considerable expansion.
b, The introduction into the said highly heated tubes, simultaneously with tho
aqueous vapour, of any desired quantity of hydrogen, which, after the operation
has been fairly started, is renewed from that produced by my improved process."
This quantity of hydrogen constitutes in the gaseous mass an inert gas, which,
after the decomposition of the steam by its contact with the heated walls of the
porcelain tubes, prevents the recombination of the oxygen with the hydrogen.
c. The temporary promotion of the decomposition of steam by means of iron
filings or other easily oxidisable matter, with which the heating tubes are partly
filled before the beginning of the process. When the tubes are highly heated, the
iron filings absorb a portion of the oxygen of the aqueous vapor, conducted into
the earthenware tubes, and thus destroy the proportion between the quantity of
oxygen and of hydrogen, the disproportion being further increased by the free
hydrogen, introduced with the steam.
The expansion of the steam allowed by the greater capacity of the refractory
earthen ware tubes as compared with that of the inlet pipe, is a first cause of
absorption of heat; the decomposition of steam into one part of hydrogen for two
parts of oxygen, produced by the contact of the aqueous vapour with the highly
heated walls of the porcelain tubes, is another cause of loss of heat.
The reduction of temperature produced by these two causes, the presence of an.
inert gas (namely the free hydrogen introduced into the retort) and the absorption
of a portion of the oxygen prevent the recombination of the oxygen with the
bydrogen, which gases therefore pass mixed with each other, but not chemically
combined, into the outlet pipes, leading to the separators, from which the oxygen
and the hydrogen are separately conducted into the respective gas holders.
The separation of the oxygen from the hydrogen is effected according to known
principles preferably by means of parchment diaphragms, or membranes, through
which the two gases pass in the inverse ratio of the square root of their respective

page_text: densities. As the density of hydrogen is about 1 of that of oxygen, the gases
pass through the diaphragms in the ratio of 4 parts of hydrogen to 1 part of
oxygen. By repeating the operation a certain number of times, an almost complete
separation of the two gases may be obtained.
As the processes described above may be carried out by various appliances,
which will easily suggest themselves to practical chemists, I do not claim any
special machinery or apparatus, or limit myself to the same. The apparatus may
for instance comprise:
A boiler for the transformation of pure water into steam; a small reservoir
filled beforehand with hydrogen, produced by any ordinary process and afterwards
fed by the gas holder; a furnace, heated by coke or other suitable material, which
may subsequently be replaced by a portion of the bydrogen, obtained by the above
patented process.
This furnace contains several horizontal tubes of fire proof earthenware. These
tubes or pipes are connected
a) At one end with a mixing chamber, to which the steam from the boiler and
the hydrogen from the reservoir are admitted by means of pipes.
b) At the other end, by means of a large pipe, with an exhaustor or pump.
The exhaustor is arranged to draw the gases out of the decomposing earthenware
tubes and to force them into a gas-holder, from which the said gases (oxygen and
hydrogen) are conducted to the separators, fitted with the membranes, as mentioned
before.
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 in Improvements in the manufacture of hydrogen is
1.) The process of decomposing aqueous vapour in vacuo (more or less complete)
and in a highly heated retort or a system of tubes of refractory earthenware such
retort or tubes of such a volume, that the vapour may expand therein.
2.) Introducing as an inert gas into the body of steam. to be decomposed or
already decomposed a suitable quantity of hydrogen.
3.) The process of decomposing aqueous vapour in highly heated retorts by the
aid of a vacuum, with or without the presence of an inert gas, and with the use of
iron filings or other oxidisable matter..
D
100-