Improvements in the Manufacture of Sodium Bicarbonate and in Apparatus therefor.
Year: 1888

page_text: Date of Application, 4th Jan., 1888
Complete Specification Left, 3rd Oct., 1888
Complete Specification Accepted, 9th Nov., 1888
Improvements in the Manufacture of Sodium Bicarbonate and in
Apparatus therefor.
I, ERNEST SOLVAY, of 19 Rue du Prince Albert, Brussels, Belgium, Manufacturer,
do hereby declare the nature of the said invention to be as follows:-
The Bicarbonate of soda produced in the manufacture of ammonia soda is not pure
for the reason that it contains ammonia which can only be removed with difficulty
and frequently it also contains empyreumatic matters which render it unfit
for use.
The object of the present invention is to provide a simple and effective process
whereby I am enabled to obtain commersially pure Bicarbonate of Soda.
For this purpose I dissolve the crude Bicarbonate of Soda in water or the mother
liquor from previous operations by the application of heat, preferably by the introduction
of steam. The solution so obtained is clarified by decantation or filtration and after
being cooled to about 35° C. is treated by carbonic acid. By this treatment
commercially pure Bicarbonate of Soda is precipitated which is separated from the
solution by filtration or otherwise and only requires drying and dressing to be ready
for use.
In heating the crude Bicarbonate of Soda with water in the first part of this process
nearly the whole of the ammonia contained in it and a considerable quantity of
carbonic acid gas are driven off. These gases are passed through suitable cooling and
condensing apparatus to cool the gases and to absorb the ammonia and the residual
carbonic acid gas, which is very pure, may with great advantage be used in the
second part of the process for reprecipitating the Bicarbonate of Soda.
In carrying out this process I prefer to use two vertical cylinders divided into a
number of compartments which may be similar in construction to the absorbing
columns described in Letters Patent granted to me dated the 18th May 1872 No. 1525.
Into one of these columns I introduce near the top the Bicarbonate of Soda and the
water or mother liquor while I introduce steam near the bottom. The gases which

page_text: leave the top of this column are passed through an absorbing apparatus and refrigerator
and are then taken into the bottom of the second column. The liquor which is drawn
off the bottom of the first column, is passed through a filter, then through a
refrigerator and is then introduced into the second column near the top and after being
saturated with carbonic acid is drawn off again from the bottom. In this way the
process can be worked as an almost continuous operation and the carbonic acid driven
out of the bicarbonate in the first operation can be used again in the second and
without the use of any machinery for compressing or propelling this gas.
The refrigerators used for cooling the gases and liquors obtained in the first
operation can be used for heating the water or mother liquor used for dissolving the
crude bicarbonate.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Sodium Bicarbonate and in
Apparatus therefor.
I, ERNEST SOLVAY of 19 Rue du Prince Albert, Brussels, Belgium, Manufacturer,
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:
The Bicarbonate of Soda produced in the manufacture of ammonia soda is not pure
for the reason that it contains ammonia which can only be removed with difficulty and
frequently it also contains empyreumatic matters which render it unfit for use.
The object of the present invention is to provide a simple and effective process
whereby I am enabled to obtain commercially pure bicarbonate of soda.
For this purpose, I dissolve the crude bicarbonate of soda in water or the mother
liquor from previous operations by the application of heat, preferably by the introduction
of steam.
The solution so obtained is clarified by decantation or filtration and after being
cooled to about 35° C. is treated by carbonic acid. By this treatment commercially
pure Bicarbonate of soda is precipitated, which is separated from the solution by
filtration or otherwise and only requires drying and dressing to be ready for use.
In heating the crude bicarbonate of soda with water in the first part of this process,
nearly the whole of the ammonia contained in it and a considerable quantity of
carbonic acid gas are driven off. These gases are passed through suitable cooling
and condensing apparatus to cool the gases and to absorb the ammonia, and the
residual carbonic acid gas, which is very pure, may with great advantage be used in
the second part of the process for reprecipitating the bicarbonate of soda.
In carrying out this process 1 prefer to use two vertical cylinders, chambers or
columns (hereinafter called columns) divided into a number of compartments, which
may be similar in construction to the absorbing columns described in Letters Patent
granted to me dated the 18th May 1872 No. 1525.
Into one of these columns I introduce near the top the bicarbonate of soda and the
water or mother liquor while I introduce steam near the bottom. The gases which
leave the top of this column are passed through an absorbing apparatus and refrigerator
and are then taken into the bottom of the second column. The liquor which is drawn
off the bottom of the first column is passed through a filter, then through a refrigerator
and is then introduced into the second column near the top, and after being saturated
with carbonic acid is drawn off again from the bottom. In this way the process can be
worked as an almost continuous operation, and the carbonic acid driven out of the
bicarbonate in the first operation can be used again in the second, and without the use
of any machinery for compressing or propelling this gas.
The refrigerators used for cooling the gases and liquors obtained in the first
operation can be used for heating the water or mother liquor used for dissolving
the crude bicarbonate.

page_text: Having thus described the nature of my said invention, I will now proceed to
describe, with reference to the accompanying drawing, the manner in which the same
is to be performed.
a is a vertical cylinder chamber or column provided at its top with an inlet pipe b
for the introduction of the crude bicarbonate of soda to be decomposed. At the
bottom of the columna is a pipe e for the admission of steam, and near the top of the
said column a is another pipe o which serves for the admission thereto of water or
mother liquor from previous operations. is a pipe through which the gases resulting
from the decomposition of the bicarbonate pass out to enter a refrigerator or cooler g
from whence they are admitted into a suitable washing apparatus . The purified
gases which leave the said washing apparatus are then taken through a pipe i into
the bottom of the second column in which the bicarbonate is reproduced.
The liquor drawn off from the bottom of the column a passes through a pipe d,
thence through a filter (not shown in the drawing) and is introduced into a refrigerator
or cooling drum m whence it is conveyed through the pipe to the top of the second
column, and after being saturated with the carbonic acid introduced into the said
column through the pipe i as before stated, the bicarbonate of soda thus produced is
drawn off from the bottom of the said column k through a pipe p from which it may
be caused to pass through a filter s in which the pure bicarbonate of soda separates
from the solution or mother liquor which may be used again for further operations.
The water or mother liquor introduced at the top of the column a through the pipe o
is forced by a suitable pump through a pipe e into the refrigerator m and passes
around the pipes or tubes through which is conveyed the liquor discharged from the
column a. Thus the said refrigerator m is used both for cooling the liquors obtained
in the first operation and for heating the water or mother liquor to be used for
dissolving the crude bicarbonate.
The bicarbonate of soda thus produced is pure and requires only to be dried and
treated in the usual manner to be ready for use.
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 is
1. The process herein described for obtaining pure bicarbonate of soda from the
crude bicarbonate, said process consisting in decomposing the crude bicarbonate by
heat, cooling and washing the carbonic acid gas evolved, and decanting and cooling
the soda solution resulting, and finally treating said solution with said purified gas and
filtering and drying the resulting bicarbonate, substantially as described.
2. An apparatus for manufacturing pure bicarbonate of soda, consisting essentially
of the columns or chambers a and k, pipes cand f, for admitting steam and discharging
carbonic acid from the column a, the inlet pipe 6 for impure bicarbonate, water inlet
pipe o, cooling drum m, water inlet pipe e, cooler y, washing apparatus h, pipe i and
pipe, substantially as described.
Dated this 3rd day of October 1888.