IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS
Year: 1864

page_text: LETTERS PATENT to George Tomlinson Bousfield, of Loughborough Park,
Brixton, in the County of Surrey, for the Invention of "IMPROVEMENTS
IN THE MANUFACTURE OF ILLUMINATING GAS."-A communication from
abroad by William Elmer, M.D., residing at New York, United States
of America.
Sealed the 7th February 1865, and dated the 6th December 1864.
COMPLETE SPECIFICATION filed by the said George Tomlinson Bousfield
at the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 6th December 1864, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, BE IT
KNOWN, that I, GEORGE TOMLINSON BOUSFIELD, of Loughborough Park,
Brixton, in the County of Surrey, do hereby declare the nature of the
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS,"
(communicated to me from abroad by William Elmer, M.D., a person resident
at New York, in the United States of America,) and in what manner the
same is to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say :-
In order that the nature and extent of the Invention may be fully
understood it is deemed proper to make a brief statement of the nature of
bituminous coal (which is the gas stock most generally used for the manu-
facture of illuminating gas), and of the effect of heat upon it.

page_text: Bituminous coal is a compound substance composed of certain elementar
constituents, of which the most important are carbon, hydrogen, and oxygen
it also contains small quantities of nitrogen and sulphur, and more or les
earthy matter.
.
Illuminating gas, as usually produced, is a compound of carbon and
hydrogen, or, more properly speaking, a mechanical mixture of various
chemical compounds of carbon and hydrogen, of which olefiant gas is the most
valuable, hence the carbon and hydrogen of the coal are valuable for the
manufacture of illuminating gas, while the oxygen, nitrogen, and sulphur are
injurious, as they impair the purity of the product by combining with a
portion of the carbon or hydrogen to form chemical compounds which do not
yield light, and some of which if not removed are noxious. But carbon and
hydrogen combine in many proportions, some of which are gaseous at ordinary
temperatures, while others are oily or ethereal liquids, or have the form of
ethereal vapors, and those compounds which are gaseous contain a less
proportion of carbon than those which are liquid or vaporous..
Compounds in all these forms can be produced from bituminous coal by the
application of heat, which effects certain changes in the combinations of its
elementary constituents, but the nature of the product varies with the degree
of heat employed. If, for example, the coal be distilled in the dry way in a
retort at the lowest temperature required to disorganize it, and drive off the
volatile substances produced, the bydrogen passes off in chemical combination
with so great a proportion of the carbon that the products of the distillation
are mainly oily and ethereal in their nature, and the least possible quantity of
carbon remains in solid form in the retort, while the gas produced available
for illumination is small in quantity and deficient in illuminating power. If,
on the other hand, the distillation be effected at a sufficiently high tem-
perature to produce illuminating gas of the best quality usually obtained at
gas works, a much less quantity of carbon passes from the retort in combination
with the bydrogen, and a large portion remains in the retort in solid form.
The process of manufacturing illuminating gas in general use is to effect
the distillation at the comparatively high temperature required to produce
good illuminating gas, and consequently the manufacture is attended with the
loss of a large amount of carbon, which, remaining in the retort in solid form,
either adheres to the retort or is valuable only as coke for fuel. Another loss
occurs from the passing off of a part of the hydrogen of the coal in chemical
combination with the oxygen thereof in the form of water, which is subse-
quently condensed, so that the hydrogen given off by the coal in this form is
withheld from combining with a portion of the carbon to form illuminating

page_text: gas, and is practically lost to the manufacturer. An additional loss occurs
from the combination of some of the oxygen of the coal with some of the
carbon thereof, in the form of carbonic acid and carbonic oxide, which not
only absorb some of the carbon, but require the employment of a largo
amount of lime in the purifying process to eliminate the former from the gas.
A further loss occurs in ordinary gas making from the deficiency of hydrogen
in the coal, there not being enough to combine with all the carbon in the
form of illuminating gas; hence, even if all the hydrogen that exists in the
coal were rendered available for the manufacture of illuminating gas, there
would still be a loss of carbon, from the want of hydrogen to combine with it
in the form of illuminating gas; and this surplus carbon either remains in the
retort or combines with a portion of the hydrogen to form liquid products
which escape decomposition, and are mainly condensed at the gas works in the
form of coal tar, which contains about as much gas-making constituents as
the illuminating gas produced, so that only about half as much illuminating
gas is produced by the ordinary process of manufacture as the gas stock has
the capacity to yield. Although the product issuing from the retort when
working at what may be termed the gas-making temperature is mainly illu-
minating gas, water, carbonic oxide, carbonic acid, and certain oily and
ethereal products, the bulk of which are condensed at the gas works in the
form of water and coal tar, the Inventor of the new process herein-after
described has satisfied himself that good illuminating gas is not the primary
product of the distilling process, but that it is a secondary product produced
by the decomposition of the oily vapors, which are first disengaged by the
coal under the action of the heat, and that in the process of gas making
directly from coal as ordinarily practised two operations are effected in the
retort; the first, which, for the sake of distinction, may be called distillation,
consisting mainly of the transmutation of certain of the constituents of the
coal into oily vapors containing too great a proportion of carbon to constitute
illuminating gas; and the second consisting in the change of the combination
of the chemical constituents of these vapors, whereby illuminating gas is
produced, accompanied with the deposit of a portion of the carbon.
Now the objects of the present Invention are to reduce the loss in carbon
incurred by the common process, and to effect the combination of all the
hydrogen existing in the coal with the carbon thereof in the form of illumi-
nating gas; also at the same operation to produce an illuminating gas of a
higher illuminating power than is generally produced at gas works. To this
end this Invention consists of a new process of gas making, consisting of two
parts, one or both of which may be used as deemed expedient.

page_text: The first part of the Invention consists of the process of distilling the coal
or other gas stock in a retort distinct and separate from that in which the gas
making is effected, and which is heated to a lower temperature than that at
which the retorts for the manufacture of illuminating gas from coal are main-
tained, and then passing the products of the distillation without condensation
into a retort heated to a high temperature, in which they are transformed into
illuminating gas in the presence of metallic zinc or other material capable of
absorbing and fixing the oxygen contained in the vapor of water, carbonic
acid, and carbonic oxide at a high temperature, so that the vapour of water
passing from the gas stock during the operation of distillation is decomposed
during the operation of gas making, the oxygen being eliminated and fixed in
a compound which cannot mix mechanically with the illuminating gas, and
the hydrogen being put in a condition to combine with a portion of the carbon
of the oily vapors in the form of illuminating gas, or, in other words, being
rendered available for gas making, and also that the oxygen may be elimi-
nated from the carbonic acid and carbonic oxide, and the carbon thereof put
in a condition to combine with hydrogen in the form of illuminating gas, the
result of this process being the utilization for gas making of portions of the
carbon and hydrogen, which would otherwise be lost for that purpose, and
the production of a much larger amount of illuminating gas than could be
produced if a portion of the hydrogen of the gas stock was permitted to escape
in combination with the oxygen in the form of water, and portions of the
carbon in combination with oxygen in the forms of carbonic acid and carbonic
oxide.
The second part of the Invention consists in the process of effecting the
distillation of the gas stock in one retort, and the gas making of the product
in another retort in presence of an additional quantity of steam (to that
obtained from the distillation of the coal), and of a material which will
decompose water at a high temperature, whereby all the hydrogen existing
in the gas stock is not only rendered available for gas making, but an addi-
tional quantity is derived from the additional steam introduced, sufficient to
transmute the surplus carbon (produced in gas making) into illuminating gas.
The introduction of steam is best effected during the distilling process, so that
it becomes highly heated and thoroughly intermingled with the products of
the distillation of the coal before it enters the gas-making retort. Its intro-
duction during the distilling process is useful also in another respect. It is
a well-known fact that any vapor passing from or through a substance
undergoing distillation tends to carry with it the vapors of other vaporizable
constituents of the substance, hence the introduction of the steam into the

page_text: distilling retort instead of directly into the gas-making retort, facilitates the
separation of the oily vapours from the gas stock, and their transmission from
the distilling retort to the gas-making retort.
The entire new process may be practised with a modification of the ordinary
apparatus now generally used at coal gas works, consisting of a bench of three
retorts connected with the hydraulic main, condenser, washer, lime purifier,
and gas holder.
As the construction and mode of operating with such apparatus is well
known to gas engineers, it is not deemed necessary to describe it in detail,
but only the modifications required, and the mode of using the modified
apparatus.
The modifications should be as follows:-In place of connecting each of
the three retorts with the hydraulic main by a separate. pipe, the lower two
retorts are connected with the upper one by discharge pipes of the customary
size, and the upper one alone is connected with the hydraulic main. The
connection between the lower and upper retorts is effected at the end of the
upper retort furthest from its connection with the hydraulic main, so that the
products of the distillation in the lower retorts are compelled to traverse the
length of the upper one before escaping, and the discharge pipe of the upper
retort must be of sufficient size to permit the free escape of the current of gas,
which is about three times as great in quantity as usually issues from a single
retort of the same size. The upper part of this discharge pipe is formed in
part of glass, so that the presence of water in the gas issuing from the upper
retort is made sensible by the condensation of it upon the glass connection..
The discharge pipe is also fitted with a small gas burner, to enable the quality
of the gas produced to be ascertained by the quality of the light it gives when
burned. A steam boiler must also be provided, and connected with each of
the lower retorts by means of a pipe fitted with a valve, or stop-cock, to
regulate the discharge of steam into the retort. Each lower retort is pro-
vided with a perforated false bottom or grating, upon which the coal can be
charged, and the steam pipe is arranged so as to direct the steam beneath the
false bottom. The lower two retorts may be constructed of iron, the upper
retort may be of iron lined with clay; but it is deemed best to construct it of
fire-brick material, as it is to be heated to a much higher temperature than
is usully employed in gas works. The three retorts may all be heated by one
fire, but the flues must be arranged in such manner as to permit the lower
two retorts to be maintained at a low red heat (say, from 700° to 800° Fah-
renheit), while the upper one is maintained at a white heat, say,. 2,500°
Fahrenheit, or more. The regulation of the beat may be effected by means of

page_text: fire-brick dampers, or in any other suitable mode. The lower two retorts
thus arranged constitute the distilling retorts for the new process, and the
upper one constitutes the gas-making retort.
The apparatus thus modified is operated as follows:-Metallic zinc is charged
juto the upper retort, coal is charged in the ordinary manner upon the false
bottoms of the lower retorts, and the retorts are closed in the ordinary way.
The coal being heated to the temperature of distillation gives off certain
products, the bulk of which are the vapors of liquids whieh passing into the
more highly heated gas-making retort are there changed by the heat in presence
of the vapor of the zinc, which having a high affinity for oxygen decomposes the
vapor of water, absorbs its oxygen, and liberates the hydrogen to permit it to
enter into combination with the carbon present in the vapours entering from
the distilling retorts. The vapor of the zinc also decomposes such carbonic
oxide and earbonic acid as may be produced by the distillation, absorbs their
oxygen, and puts their carbon in a condition to combine with hydrogen. If.
the gas stock used be cannel coal, the product of the distillation in the distilling
retorts may be represented with sufficient accuracy for practical purposes by
the chemical formula CH,+CH,+HO+CO,+CO, which represents &
mixture of the vapors of liquid, hydrocarbons, light, carburetted bydrogen,
vapour of water, carbonic acid, and carbonic oxide. These in presence of the
volatilized zinc (Zn) and under the high temperature are transformed, and
the changes produced may be represented by the equation CH,+CH₂+
HOCO + CO +4 Zn = 12 C, H+ 4 Zn O, that is to say, the four
equivalents of oxygen (from the water, the carbonic acid, and the carbonic
oxide) combine with four equivalents of zinc to form oxide of zinc, while the
24 equivalents of carbon combine with 12 equivalents of hydrogen to form
12 of acetylene (CH), which is an illuminating gas of the highest light-pro-
ducing power. If an additional quantity of hydrogen be supplied, so that the
24 equivalents of carbon may combine with 24 of hydrogen, olefiant gas is pro-
duced, which is the illuminating gas most highly valued by gas manufacturers.
This result may be accomplished by the admission of steam into the distilling
retorts by means of the pipes and stop-cocks provided for that purpose (us
before described), so that the steam mingles with the volatile products given off'
by the coal during distillation and enters the gas-making retort with them;
its oxygen is there absorbed by combination with an additional quantity of the
zine to form oxide of zinc, while its hydrogen is placed in a condition to combine
with the carbon of the products of the distillation of the coal. In order to
ensure the operation, the steam should be superheated before its introduction
into the distilling retorts by causing it to pass through a heated pipe.

page_text: From the foregoing description it appears that the quantity of the illumina-
ting gas produced depends upon the quantity of steam admitted. If more
than the quantity required to transform the carbon into olefiant gas be admitted
the illuminating gas will be deficient in illuminating power, and the steam may
under certain circumstances escape decomposition by the zinc, and issue from
the upper retort mechanically mixed with the illuminating gas; it is therefore
important that the operator should have the means of regulating the quantity
of steam and of determining how much is required. The first of these two is
furnished by the valves on the steam pipes, the second by the test burner and
the glass portion of the discharge pipe of the gas-making retort, or by roting
the accumulation of water in the hydraulic main, or its escape therefrom. If
the steam be admitted in too large quantities the illuminating power of the
gas as shown at the test burner is impaired, and the steam valves are to be
partially closed or wholly if necessary towards the close of the operation when
the gas stock is exhausted, and if any steam escape decomposition, it is made
sensible by condensation at the glass portion of the discharge pipe or in the
hydraulic main. The operations of distillation and gas making proceed until
the quality of the light at the test burner shows that the gas stock is exhausted,
when the distilling retorts are opened, the residuum withdrawn, and new
charges of gas stock are introduced as before. The oxide of zine requires to
be withdrawn from the gas-making retort, and from the discharge pipe where
it sometimes lodges at intervals, and fresh quantities of zinc must be charged
into the upper retort. The oxide of zinc thus produced may be sold for paint
or may be treated as zine ore for the manufacture of metallic zinc, and the
zinc so recovered may be used over again in the gas-making retort. As the
zine is always present in excess in the gas-making retort, a portion of its
vapors pass off with the gas, this portion is condensed in the discharge pipe
leading upwards to the hydraulic main and runs back into the gas-making
retort, and if the discharge pipe does not prove on trial to be sufficiently
long to condense all the vapor of zinc thus escaping it should be made
longer.
The gas produced passes into the hydraulic main of the gas works, and is
treated in all respects as to purification, &c., like ordinary coal gas, but the
lime required in the lime purifiers is less in quantity than is required for
ordinary coal gas, as little or no carbonic acid escapes with the gas. The
residuum remaining in the distilling retorts, if the process be conducted
carefully, is almost wholly earthy matter. As, however, the fuel generally used
in gas works is coke produced by the operation, it may frequently be advan-
tageous to conduct the manufacturo by the new process in such manner as

page_text: to produce sufficient coke to serve as fuel in the gas works. This result may
be obtained by stopping the admission of steam at some predetermined stage
in the operation which may be found by trial sufficient, thus, for example, if
the process required a period of four hours for the complete exhaustion of the
gas stock, the steam may only. be admitted during a portion of this period, say
three hours, then upon opening the distilling retorts at the end of the four
hours, a certain quantity of coke will be found in them, and if this quantity be
less or more than the average required for gas making, a charge of coal, the
stage at which the admission of steam is stopped for succeeding charges may
be made earlier or later in the operation. The manufacturer therefore has it
in his power to regulate the production of coke by regulating the admission of
steam during the operation.
The foregoing description sets forth the complete process as applied to the
manufacture of illuminating gas from cannel coal as the gas stock, but the
process is applicable with advantage to other gas stock, as, for example, peat,
asphaltam, and solid and liquid hydrocarbons, such as the fats, oils, and petro-
leums. In case the solid hydrocarbons are liquifiable either by heat or by
beat and solution in the liquid hydrocarbons, they should be reduced to the
liquid form before their introduction into the distilling retort, and fed to it by
means of a feed pipe and valve of the same description as is used for feeding
oils in the manufacture of oil gas. The liquid hydrocarbons should be fed in
the same manner.
The process has also been described as practised with two distilling and one
gas-making retort, because this mode is adapted to the ordinary arrangement of
many coal gas
works with the least change of the apparatus, but the number of
distilling retorts and of gas-making retorts is a matter of expediency and may be
varied to suit particular circumstances; all that is essential in respect to number
being that there shall be at least one distilling retort and at least one gas-making
retort working in connection; zinc has also been described as the material for
eliminating and fixing the oxygen of the vapour of water and other compounds
of oxygen, but the Invention is not limited to the use of this material, as
manganese or other material having the requisite affinity at a high heat for
oxygen to eliminate it from the gaseous compounds of oxygen present in the
gas-making retort, and fix it so that it cannot mix mechanically with the
illuminating gas delivered in the gas holder, may be used for the purpose.
The foregoing description also describes the introduction of the additional
quantity of steam as effected in the distilling retort, it may however be intro-
duced into the gas-making retort instead of into the distilling retort, but in this
case it should be highly heated by being caused to pass through pipes heated

page_text: to the highest red heat, or better to a white heat, before it enters the gas-
making retort, so that it may not reduce the heat of the latter; it should also
be arranged to enter with the products of the distillation so as to be intimately
mingled with them.
The complete Invention having been thus described, it is proper to state that
the first part of the Invention may be used without using the second, whenever
circumstances may render such use advantageous. The illuminating gas pro-
duced being richer in carbon than the ordinary coal gas made at gas works,
has a higher illuminating power, and is more valuable to the consumer.
Having thus described one mode of practising the entire Invention, what I
claim and desire to secure by Letters Patent is,-
The process of manufacturing illuminating gas by distilling the gas stock in
one retort, and converting the volatile product of the distillation into illumina-
ting gas in another retort in the presence of a material which when at a bigh
temperature will absorb and fix the oxygen contained in the volatile product
of the distillation, the process being conducted substantially as set forth.
I also claim the process of manufacturing illuminating gas by distilling the
gas stock in one retort, and converting the volatile product of the distillation
into illuminating gas in another retort in the presence of additional quantity
of steam to that obtained from the gas stock, and of a material which will
absorb and fix the oxygen contained in the volatile product of the distillation
and in the additional steam, the process being conducted substantially as set
forth.
In witness whereof, I, the said George Tomlinson Bousfield, have here-
unto set my hand and seal, this Twenty-eighth day of November, in the
year of our Lord One thousand eight hundred and sixty-four.
GEO. T. BOUSFIELD. (L.S.)