IMPROVEMENTS IN THE MANUFACTURE OF SULPHUROUS ANHYDRIDE
Year: 1882

page_text: LETTERS PATENT to Sydney Pitt of Sutton in the County of Surrey for
"
an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF SULPHUROUS
ANHYDRIDE Communicated to him from abroad by the Compagnie
Industrielle des procédés Raoul Pictet of Paris
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 4th August 1882.
SYDNEY PITT of Sutton in the County of Surrey. "IMPROVEMENTS IN THE
MANUFACTURE OF SULPHUROUS ANHYDRIDE [Communicated to him from abroad,
by the Compagnie Industrielle des procédés Raoul Pictet of Paris]
-
In manufacturing sulpburous anhydride practical difficulties have been
experienced; particularly in the perfect dehydration of the gas.
The present invention relates to a new process of dehydration. It has been
found by laboratory experiments that the whole series of hydrates of sulphurous
acid crystallise at temperatures higher than 10 degrees Centigrade. This
crystallization takes place easily under atmospheric pressure.
The novel system of dehydration consists in lowering the temperature of the
whole mass of gas to 10 degrees, and removing all trace of water by means of
crystallization.
Gaseous acid which has experienced this reduction of temperature has deposited
all the vapour of water which it may have contained.
The following are the arrangements to be employed to obtain this result in
practice.
The gaseous sulphurous acid as it comes from the retorts where it is prepared
by any method but preferably by the decomposition of commercial sulphuric acid
of commerce by sulphur, is delivered by a pipe suitably proportioned to the
production; about 12 centimetres for a daily production of 1500 kilos into a long
refrigerating channel say 18 to 20 metres long and 20 centimetres in diameter.
These dimensions however may be very considerably varied.

page_text: The refrigerating channel is laid nearly horizontally, with a slight fall to the
further end which is closed by a cover.
Another tube is fixed at the further end of the refrigerating channel. By this
the purified gas issues and passes into an oil gasometer. A tube leads the gas to a
small compressing pump.
This pump compresses the gaseous sulphurous anhydride into a condenser The
condenser is of cylindrical form and contains a bundle of tubes traversed constantly
by a current of water at ordinary temperature.
The water is heated during its passage by the whole of the heat disengaged in
the liquidification of the sulphurous anhydride compressed by the pump.
The liquified sulphurous anhydride passes out of the condenser and a jet of
liquified sulphurous anhydride is projected into the refrigerating channel.
The liquid being now subjected only to the atmospheric pressure becomes cooled
instantly to a temperature of 10 degrees and the walls of the channel being
metallic (wrought or cast iron or copper) the whole channel partakes of this low
temperature. The gaseous sulphurous acid being obliged in reaching the gasometer
to traverse the whole length of the refrigerating channel is also reduced in
temperature and deposits in the form of crystals all the hydrates which it contains.
The working of the pump is so regulated that the refrigerating channel is kept
about one third full of liquid.
Thus in accordance with the preceeding, the operation is started and carried on
continuously in the following manner. A small quantity of gaseous sulphurous
acid is prepared and this is at once compressed by the pump and sent into the
refrigerating channel which it enters in the liquid form.
Evaporation rapidly takes place and commences the dehydration of this portion
of sulphurous acid by reducing the temperature in the refrigerating channel.
This same quantity of gaseous acid is taken by the pump reliquified and returned
into the refrigerating channel.
It results from this operation, which is slowly conducted, that at last the greater
part of the sulphurous acid manufactured is obtained in a liquid form in the
refrigerating channel. When hoar frost completely covers the channel and it is
known from the time which has been occupied that sufficient sulphurous acid is
accumulated, the pump is stopped and the production of sulphurous acid is rendered
more active.
The gas becomes completely dehydrated in the refrigerating channel and passes
out in the form of sulphurous anhydride, perfectly pure and dry.
From time to time the pump is again set to work to maintain the level of the
liquid in the refrigerating channel.
At the end of four or five days working, the operation is stopped the covers are
taken off and the refrigerating channel is emptied. The bydrates of sulphurous
acid melt at temperatures about 15 degrees and run out of the channel in a
liquid form.
Cocks or valves are placed on all the tubes so that any part of the apparatus can
be isolated at will and rendered independant.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sydney Pitt in the Great Seal Patent Office on the 2nd February
1883.
"
SYDNEY PITT of Sutton in the County of Surrey.
"IMPROVEMENTS IN THE
MANUFACTURE OF SULPHUROUS ANHYDRIDE' (A communication to me from
abroad by the Compagnie Industrielle des procédés Raoul Pictet of Paris)
In manufacturing sulphurous anhydride by the processes described in the
Patent No. 2727 in the year 1875 some practical difficulties have been experienced;
particularly in the perfect dehydration of the gas obtained by the decomposition of
commercial sulphuric acid under the influence of sulphur.
•
The present invention relates to a new process of dehydration. It has been
found by laboratory experiments that the whole series of hydrates of sulphurous
acid crystallise at temperatures higher than 10 degrees centigrade. This
crystallization takes place easily under atmospheric pressure.
The novel system of dehydration consists in lowering the temperature of the
whole mass of gas to 10 degrees, and removing all trace of water by means of
crystallization.
Gaseous acid which has experienced this reduction of temperature has deposited
all the vapour of water which it may have contained.
The following are the arrangements to be employed to obtain this result in
practice.
The gaseous sulphurous acid as it comes from the retorts where it is prepared
by any method but preferably by the decomposition of commercial sulphuric acid
of commerce by sulphur, is delivered at A by a pipe suitably proportioned to the
production, about 12 centimetres for a daily production of 1500 kilos. The tube A
is attached to a long refrigerating channel B, say 18 to 20 metres long and 20
centimetres in diameter.
These dimensions however may be very considerably varied.
The refrigerating channel is laid nearly horizontally, with a slight fall to the
further end L which is closed by a cover.
Another tube M is fixed at the further end of the refrigerating channel By this
the purified gas issues.
From the pipe M the gas passes into an oil gasometer G. At C a tube leading
to a small compressing pump D is connected with the pipe M.
This pump compresses the gaseous sulphurous anhydride which it draws at C
into a condenser E. The condenser is of cylindrical form and contains a bundle of
tubes traversed constantly by a current of water at ordinary temperature.
The water enters at I, and issues at K and is heated during its passage by the
whole of the heat disengaged in the liquification of the sulphurous anhydride
compressed by the pump.
The liquified sulphurous anhydride passes out of the condenser by the orifice F
and is regulated in its flow by a screw cock R. A jet of liquified sulphurous
anhydride is projected at S from the end of the pipe F, R, H, S, into the
refrigerating channel B.
The liquid being now subjected only to the atmospheric pressure becomes cooled
instantly to a temperature of 10 degrees and the walls of the channel being metallic
(wrought or cast iron or copper) the whole channel partakes of this low tem-
perature. The gaseous sulphurous acid, being obliged in reaching the gasometer to
traverse the whole length of the refrigerating channel is also reduced in
temperature and deposites in the form of crystals all the hydrates - which it
contains.

page_text: The working of the pump D is so regulated that the refrigerating channel is
kept about one third full of liquid.
Thus, in accordance with the preceding, the operation is started and carried on
continuously in the following manner:-a small quantity of gaseous sulphurous
acid is prepared and this is at once compressed by the pump D and sent into the
refrigerating channel which it enters in the liquid form.
Evaporation, rapidly takes place, and commences the dehydration of this portion
of sulphurous acid by reducing the temperature in the refrigerating channel.
This same quantity of gaseous acid is taken by the pump, reliquified and returned
into the refrigerating channel.
It results from this operation, which is slowly conducted, that at last the greater
part of the sulphurous acid manufactured is obtained in a liquid form in the
refrigerating channel B. When hoar frost completely covers the channel and it
is known from the time which has been occupied that sufficient sulphurous acid is
accumulated the pump D is stopped and the production of sulphurous acid is
rendered more active. The gas becomes completely dehydrated in the refrigerating
channel B and passes out at M in the form of sulphurous anhydride, perfectly pure
and dry.
From time to time the pump D is again set to work to maintain the level of the
liquid in the refrigerating channel B.
At the end of four or five days working, the operation is stopped the covers
at L and H are taken off and the refrigerating channel B is emptied. The hydrates
of sulphurous acid melt at temperatures about 15 degrees and run out of the
channel in a liquid form.
Cocks or valves are placed on all the tubes so that any part of the apparatus can
be isolated at will, and rendered independant.
What I claim is :-
The dehydration of gaseous sulphurous acid, produced by known means, by
means of liquified sulphurous acid and by the employment of low temperatures
obtained directly by the natural evaporation of this body, separating from the gas
by crystallization and condensation, all the hydrates of sulphurous acid.
In witness whereof I the said Sydney Pitt have hereunto set my hand
and seal this thirty first day of January in the year of our Lord One
thousand eight hundred and eighty three.