IMPROVEMENTS IN PURIFYING COAL GAS
Year: 1877

page_text: LETTERS PATENT to John Hammond, of Lewes, in the County of Sussex, Gas
Engineer, for the Invention of "IMPROVEMENTS IN PURIFYING COAL GAS."
Sealed the 12th April 1878. and dated the 15th October 1877.
PROVISIONAL SPECIFICATION left by the said John Hammond at the
Office of the Commissioners of Patents on the 15th October 1877.
JOHN HAMMOND, of Lewes, in the County of Sussex, Gas Engineer.
MENTS IN PURIFYING COAL GAS."
66
IMPROVE
The object of this Invention is the continuous purification of coal gas in closed
vessels by strong liquid ammonia produced from the crude ammoniacal liquor of
gasworks, and the ultimate recovery of the ammonia as sulphate of ammonia, also
the prevention of napthaline formations by the thorough absorbsion of the acid
vapours contained in the gas.
In carrying out this Invention, the crude ammoniacal liquor is conducted by
proper arrangements to two suitable vessels (ordinary egg end steam boilers, each
set over an ordinary furnace will answer the purpose) properly provided with
dampers, that each boiler may, as required, be fired independently of the other;
these boilers have an arrangement of pipes and valves, that the vapours escaping
from the one may be conducted through the liquid contained in the other, and vice
versa.
The process is as follows:-The two boilers being filled to a proper height with
the crude ammoniacal liquor, both fires are lighted under the boilers, and the escaping
vapours from each boiler conducted by suitable pipes to a leaden vessel, called a
saturator, filled to the proper height with a given quantity of sulphuric acid of a
suitable strength for the manufacture of ammonia sulphate. The ammonia contained
in the escaping vapours from the boilers is thus arrested and converted into sulphate
of ammonia in the ordinary way. The saturator being constructed in such a manner
that the gases or vapours after passing through the sulphuric acid are again collected,
and after proper cooling may be passed through oxide of iron for the recovery of
CD 1.31

page_text: sulphur by well-known methods; the remaining gases can then be conducted over a
red hot furnace flue and escape by the main chimney shaft.
The vapours or gases continue to pass freely from the boiler to the saturator and
oxide vessel, &c., till most of the carbonic acid and sulphureted hydrogen are driven off
the crude liquor, also with sufficient ammonia to convert the given quantity of acid
contained in the saturator to sulphate of ammonia. The boiler valves leading to
saturator are then closed, and the sulphate of ammonia taken out to a draining table
in the usual way, and a fresh supply of acid put into saturator for the next operation.
In the mean time milk of lime has been mixed in an ordinary tub. High-pressure
steam is used to expel the air contained in a strong and suitable iron vessel; the steam
being shut off, a vacuum is produced in the said iron vessel, whereby the whole of the
milk of lime contained in the tub (minus the sediment) is drawn over the top of tub
through pipes properly arranged to the iron vessel, the cock or valve leading to lime
tub is then closed, and the high-pressure steam turned on full to said iron vessel,
and the whole of the milk of lime is driven into the boilers containing the crude
ammoniacal liquor now under treatment; this milk of lime is in sufficient quantity
to neutralize the acids now remaining in the ammoniacal liquor in the boilers, since
the valves to the saturator were closed. The milk of lime and the liquor is then
agitated together by high-pressure steam in the said boilers, producing a strong
chemical reaction, and setting free the ammonia in large quantities, and this agitation
can be repeated as often as necessary, till the whole of the ammonia is driven
off from the liquor in one boiler through the other boiler, or vice versa (to
keep up a continuous agitation of the contents of boilers, the flue dampers and fires
being regulated accordingly). As soon as this strong chemical reaction is produced
by the milk of lime and higher-pressure steam, the strong ammoniacal vapours are
conducted through suitable pipes and apparatus to the hydraulic main of
the gasworks, provision is made to regulate the temperature of vapours entering
the hydraulic main; this strong ammoniacal vapour now condenses in the ordinary
apparatus of the gasworks in the form of strong liquid ammonia, and flows out
comparitively cool with the tar and liquid from the outlet of condenser to a
closed vessel of suitable capacity, in which is arranged suitable coils of pipes, the
cold water supply to the works being made to pass through these pipe coils; the
contents of this closed vessel are kept cold and the tar settles away from the liquid
ammonia, and can be drawn off as desired. The liquid ammonia being cold can now
be conducted to a suitable vessel, so constructed as to bring the liquid ammonia
and the crude gas into the closest possible contact, provision being made to free the
crude gas from any remaining tarry impurity on its entrance by direct contact with
the liquor contained in the bottom of vessel; the crude gas then passes up and
between a series of thin circular rings or plates of metal or other suitable material,
slightly concaved on the under and upper side, and arranged in such numbers and
at such distance as to give the best possible effect to the passing gas, which rushes
in the thinest possible streams over the surface of the strong liquid ammonia now
descending from plate to plate till it reaches the bottom, fully impregnated with the
impurities from the crude gas (this liquid may be used over again, as described
for the purpose of obtaining sulphate of ammonia and purifying the gas); the
gas now passing this vessel is conducted to what is known as the tower or clean
water scrubber for the recovery of any aminonia escaping with the gas from the
last vessel; in purifying gas by this method, no trouble is experienced from
napthaline deposits, and little or no work is left for ordinary lime purifiers in
proportion to the quantity and strength of liquid ammonia employed in this
process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Hammond in the Great Seal Patent Office on the 13th April
1878.
JOHN HAMMOND, of Lewes, in the County of Sussex, Gas Engineer. "IMPROVE-
MENTS IN PURIFYING COAL GAS."
The object of this Invention is the continuous purification of coal gas in closed
vessels by strong liquid ammonia produced from the crude ammoniacal liquor of gas-
works, and the ultimate recovery of the ammonia as sulphate of ammonia, also the
prevention of napthaline formations by the thorough absorbsion of the acid vapour
contained in the gas.
In carrying out this Invention, the crude ammoniacal liquor is conducted by proper
arrangements to two suitable vessels (ordinary egg end steam boilers, each set over
an ordinary furnace will answer the purpose) properly provided with dampers, that
each boiler may, as required, be fired independently of the other. These boilers
have an arrangement of pipes and valves that the vapours escaping from the one
may be conducted through the liquid contained in the other, and vice versa.
The process is as follows:-The two boilers being filled to a proper height with
the crude ammoniacal liquor, both fires are lighted under the boilers, and the
escaping vapours from each boiler conducted by suitable pipes to a leaden vessel
called a saturater, filled to the proper height with a given quantity of sulphuric
acid of a suitable strength for the manufacture of ammonia sulphate; the ammonia
contained in the escaping vapours from the boilers is thus arrested and converted
into sulphate of ammonia in the ordinary way. The saturater being constructed in
such a manner that the gases or vapours after passing through the sulphuric acid
are again collected, and after proper cooling may be passed through oxide of iron
for the recovery of sulphur by well-known methods; the remaining gases can then
be conducted over a red hot furnace flue and escape by the main chimney shaft.
The vapours or gases continue to pass freely from the boilers to the saturater
and oxide vessel, till most of the carbonic acid and sulphuretted hydrogen are driven
off from the crude liquor, also with sufficient ammonia to convert the given quan-
tity of acid contained in the saturater to sulphate of ammonia. The boiler valves
leading to saturater are then closed, and the sulphate of ammonia taken out to a
draining table in the usual way, and a fresh supply of acid put into saturater for
the next operation. In the meantime milk of lime has been mixed in an ordinary tub.
High-pressure steam is used to expel the air contained in a strong and suitable iron
vessel; the steam being shut off, a vacuum is produced in the said iron vessel, whereby
the whole of the milk of lime contained in the tub (minus the sediment) is drawn
over the top of tub through pipes properly arranged to the iron vessel, the cock or
valve leading to lime tub is then closed, and the high-pressure steam turned on full
to said iron vessel, and the whole of the milk of lime is driven into the boilers
containing the crude ammoniacal liquor now under treatment; this milk of lime is
in sufficient quantity to neutralize the acids now remaining in the ammoniacal
liquor in the boilers, since the valves to the saturater were closed. The milk of lime
and the liquor is then agitated together by high-pressure steam in the said boilers,
producing a strong chemical reaction, and setting free the ammonia in large quan-
tities, and this agitation can be repeated as often as necessary till the whole of the
ammonia is driven off from the liquor in one boiler through the other boiler, or
vice versa (to keep up a continuous agitation of the contents of boilers), the Blue
dampers and fires being regulated accordingly. As soon as this strong chemical
reaction is produced by the milk of lime and high-pressure steam, the strong ammo-
niacal vapours are conducted through suitable pipes and apparatus to the hydraulic
main of the gasworks, provision is made to regulate the temperature of vapours
entering the hydraulic main; this strong ammoniacal vapour now condenses in the
ordinary apparatus of the gasworks in the form of strong liquid ammonia, and flows
out comparitively cool with the tar and liquid from the outlet of condenser to a

page_text: closed vessel of suitable capacity, in which is arranged suitable coils of pipes, the
cold water supply to the works being made to pass through these pipe coils to keep
cool the contents of this closed vessel and the tar settles away from the liquid
ammonia, and can be drawn off as desired. The liquid ammonia being cold can
now be conducted to a suitable vessel, which may be termed as a "scrubber washer,"
so constructed as to bring the liquid ammonia and the crude gas into the closest pos-
sible contact, provision being made to free the crude gas from any remaining tarry
impurity on its entrance by direct contact with the liquor contained in the bottom
of vessel; the crude gas then passes up and between a series of thin circular rings
or plates of metal or other suitable material, slightly concaved on the under and
upper side, and arranged in such numbers and at such distance as to give the best
possible effect to the passing gas, which rushes in the thinnest possible streams close
to the surface of the strong liquid ammonia now descending from plate to plate
till it reaches the bottom fully impregnated with the impurities from the crude
gas (this liquid may now be used over again, as described, for the
purpose
obtaining sulphate of ammonia and purifying the gas); the gas now passing this
vessel is conducted to what is known as the tower or clean water scrubber for the
recovery of any ammonia escaping with the gas from the last vessel; in purifying
gas by this method no trouble is experienced from napthaline deposits, and little or
no work is left for ordinary lime purifiers in proportion to the quantity and
strength of liquid ammonia employed in this process.
of
Having thus fully described my Invention, and the manner of performing the
same, I wish it to be understood that I ciaim,-
First. The purification of coal gas by the process of introducing to the hydraulic
main of the gasworks, strong ammoniacal gas (containing steam or vapour) set free
from carbonic acid and sulphuretted hydrogen, by distillation of the crude amino-
niacal liquor of gasworks with the caustic lime, and agitated together by steam in
closed vessels or boilers, as before described, the contents of boilers to be kept at
boiling point by means of ordinary fires set under them. The temperature of the
said ammoniacal gas and vapour before entering the hydraulic main is reduced and
regulated by passing through a series of pipes arranged in a closed vessel and kept
filled with water. It is obvious that caustic ammonia liquor will be thus be produced,
and further condensing in the ordinary apparatus of the gasworks, it will, of
necessity, absorb impurities from the passing gas.
Second. (The further use of the caustic ammonia liquor so produced in) the appa-
ratus constructed and described as above, and termed the scrubber washer, the
ammonia to be afterwards recovered as sulphate of ammonia, as before described.
In witness whereof, I, the said John Hammond, have hereunto set my hand
and seal, this Fifth day of April, in the year of our Lord One thousand
eight hundred and seventy-eight.
JOHN HAMMOND. (L.S.)