Improved Means for Evaporating and Concentrating Liquid Solutions and in Obtaining Solid Substances from such Solutions.
Year: 1898

page_text: Improved Means for Evaporating and Concentrating Liquid Solutions
and in Obtaining Solid Substances from such Solutions.
I, WILLIAM MATHER, of Salford Iron Works, Manchester, Engineer, do hereby
declare the nature of this invention to be as follows:-
This invention relates to improved means for evaporating and concentrating
liquid solutions and in obtaining in a solid state the salts or other substances
previously held in solution.
"
The invention is applicable to solutions of various kinds and the nature of
the invention being described with reference to the concentrating of solutions
of caustic soda and the obtaining therefrom of caustic soda in a solid or an-
hydrous state, its application to solutions of other substances will be evident.
The ordinary method of concentrating caustic soda solutions so as to eventually
secure solid or anhydrous caustic is to run the comparatively weak liquor as it
is formed, by electrolytic or chemical processes, into a large cast iron evaporating
pan called a
pot," which is built into a furnace, and by the direct application
of the heat of the furnace to evaporate the water contained in the liquid alkali,
after which the anhydrous liquid is scooped from the "pot" by ladles and placed
in sheet iron drums, in which it solidifies on becoming cold. The drums are
then sealed with a cover and are ready for the market. The waste heat from
the "pot" furnace is often employed to surround a second pot or pan (called a
boat pan,") into which weak liquid may be first received on its way to the
pot," and where it undergoes a partial evaporation. This preliminary or partial
concentration is sometimes effected by a special evaporater in which the liquid
is passed through a multitubular apparatus heated by steam, while the liquid
is subjected to a vacuum in the tubes to increase the effect of the steam heat.
According to this invention the weak caustic solution may be concentrated
to any desired extent and be reduced to a solid state by a continuous process.
To effect this, the weak or comparatively weak caustic solution is fed in regu-
lated quantity to a trough in which a hollow cylinder is continuously revolving.
The trough is heated so as to maintain the liquid at a considerable temperature,
and the hollow cylinder is heated from within by oxy-hydrogen gas or any
other suitable source of heat, so that its exterior surface is considerably higher
in temperature than that of the liquid in the trough. The surface of the cylinder
being partially immersed in the caustic liquid, in revolving its surface becomes
covered with a film of the alkali. The effect of this is that the water contained
in the film of caustic liquid upon the cylinder, is very rapidly driven off as the
cylinder revolves and the whole of the liquid contained in the trough becomes
gradually more and more concentrated. This operation may be repeated by an
overflow of the concentrated liquid in the first trough passing to a second trough
heated in a similar way, and having a similar revolving cylinder, and so on
through any number of troughs containing cylinders that may be required for a
given amount of concentration or for treating any given solution.
Where it is desired to produce solid caustic the evaporation is continued until

page_text: the film upon the surface of the first or other cylinder of a series, consists of
anhydrous liquid caustic soda, which is removed from the surface of this cylinder
as it revolves by a stripping cylinder revolving in the same direction so as to
produce an opposite face travel at what may be called the point of contact.
When dealing with caustic soda it is preferable not to have absolute contact
but simply to adjust the stripping cylinder closely to the surface of the last hot
cylinder. The stripping cylinder is also hollow, and is chilled or kept cool by
a continuous stream of cold water flowing therethrough or by other means.
The cold cylinder coming almost into contact with the last hot cylinder makes
contact with and collects most of the film upon the surface of the latter and
this film passing directly to the surface of the cold cylinder is immediately
reduced to a solid state, and covers the cold cylinder with a fine film of
anhydrous caustic soda, which is continually stripped from the cylinder by a
"doctor" or like blade. The film of pure white caustic soda is thus broken up
into the form of powder or fine shells and as it falls is received into the packing
drums ready for the market.
An essential condition to the success of these operations is that all the metallic
parts of the apparatus in contact with the liquid shall be of a material or be
coated with a surface which will not injuriously affect or be affected by the
particular liquid being treated and which shall be capable of standing the heat
which is to be applied.
"
It may be noted among the advantages of this process and arrangement of
apparatus that as the film is taken from the hot cylinder by the cold cylinder
all scraping of hot cylinders by a doctor" is obviated and consequently the
surface of such hot cylinder may be of expensive metal if necessary, as there is
practically no wear and tear or scraping action thereon.
Where it is desired to hasten the evaporation and concentration one or more
cylinders and pans may be enclosed in a vacuum chamber.
P
1000
PHILIP M. JUSTICE,
55 and 56, Chancery Lane, London, Chartered Patent Agent,
For the Applicant.
Improved Means for Evaporating and Concentrating Liquid Solutions.
and in Obtaining Solid Substances from such Solutions.
I, WILLIAM MATHER, of Salford Iron Works, Manchester, Engineer, 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;-
This invention relates to improved means for evaporating and concentrating
liquid solutions or in obtaining in a solid state the salts or other substances
previously held in solution.
The invention is applicable to solutions of various kinds and the nature of
the invention being described with reference to the concentrating of solutions-
of caustic soda and the obtaining therefrom of caustic soda in a solid or an-
hydrous state, its application to solutions of other substances will be evident.
The ordinary method of concentrating caustic soda solutions so as eventually to
secure solid or anhydrous caustic is to run the comparatively weak liquor as it
is formed, by electrolytic or chemical processes, into a large cast iron evaporating
pan called a "pot," which is built into a furnace, and by the direct application

page_text: f
of the heat of the furnace to evaporate the water contained in the liquid alkali,
after which the anhydrous liquid is scooped from the "pot" by ladles and placed
in sheet iron drums, in which it solidifies on becoming cold. The drums are
then sealed with a cover and are ready for the market. The waste heat from
the "pot" furnace is often employed to surround a second pot or pan (called a
"boat pan,") into which weak liquid may be first received on its way to the
pot," and where it undergoes a partial evaporation. This preliminary or partial
concentration is sometimes effected by a special evaporater in which the liquid
is passed through a multitubular apparatus heated by steam, while the liquid
is subjected to a vacuum in the tubes to increase the effect of the steam heat.
According to this invention the weak caustic solution may be concentrated to
any desired extent and be reduced to a solid state by a continuous process.
And to clearly explain how this may be done reference is made to the accompany-
ing drawings in which Fig. 1 represents in side sectional elevation an apparatus for
carrying out the invention the section being on line A B of Fig. 2 which is a sectional
elevation through one of the evaporating cylinders and pans and is taken on the
line CD of Fig. 1 while Fig. 3 is a sectional elevation of the stripping or chilling
cylinder showing the preferred arrangement of water inlet and outlet therefrom.
As shown in the drawings the weak or comparatively weak caustic solution is fed
from tank 1 through valve 2 in regulated quantity to a trough 3 provided with
an overflow lip over which the caustic quietly flows to the first of the evaporating
troughs 4 in which a hollow cylinder 5 is continuously revolving. The trough 4
is heated so as to maintain the liquid at a considerable temperature, and the
hollow cylinder is heated from within by oxy-hydrogen gas or any other suitable
source of heat, so that its exterior surface is considerably higher in temperature
than that of the liquid in the trough.
The means for heating shown in the drawings consist of atmospheric burners 6
supplied with air and gas by pipes 7 and 8 the supply to the interior of cylinders 5
being made through one trunnion as most clearly shown in Fig. 2 while the
waste gases escape by pipe 9 through the other trunnion but it is obvious that
any other suitable heating system may be employed. The surface of the cylin-
der 5 being partially immersed in the caustic liquid, in revolving its surface
becomes covered with a film of the alkali. The effect of this is that the water
contained in the film of caustic liquid upon the cylinder, is very rapidly driven
off as the cylinder revolves and the whole of the liquid contained in the trough 4
becomes gradually more and more concentrated. This operation may be repeated
by an overflow of the concentrated liquid in the first trough 4 passing to a
second trough 4 heated in a similar way, and having a similar revolving cylin-
der 5 and so on through any number of troughs containing cylinders that may
be required for a given amount of concentration or for treating any given
solution.
Where it is desired to produce solid caustic the evaporation is continued until
the film upon the surface of the first or other cvlinder 5 of a series, consists of
anhydrous liquid caustic soda, which is removed from the surface of this cylinder
as it revolves by a stripping cylinder 10 revolving in the same or in the opposite
direction so as to produce the same or opposite face travel at what may be called
the point of contact. When dealing with caustic soda it is preferable not to
have absolute contact but simply to adjust the stripping evlinder 10 closely to
the surface of the last hot cylinder 5. The stripping cylinder 10 is also hollow,
and is chilled or kept cool by a continuous stream of cold water flowing there-
through or by other means.
As shown in Fig. 3 cylinder 10 has an inlet pipe 11 passing through one trun-
nion and delivering the water near the bottom of the cylinder while the outlet
pipe 12 passes through the other trunnion and terminates near the top of the
cylinder.
The cold cylinder 10 coming almost into contact with the last hot cylinder
makes contact with and collects most of the film upon the surface of the latter

page_text: and this film passing directly to the surface of the cold cylinder is imme-
diately reduced to a solid state, and covers the cold cylinder 10 with a
fine film of anhydrous caustic soda which is continually stripped from the
cylinder by a doctor or like blade 13. The film of pure white caustic soda
is thus broken up into the form of powder or fine shells and as it falls is received
into hopper 14 from whence it may be packed into drums 15 ready for shipment.
An essential condition to the success of these operations is that all the metallic
parts of the apparatus in contact with the liquid shall be of a material or be
coated with a surface which will not injuriously affect or be affected by the
particular liquid being treated and which shall be capable of standing the heat
which is to be applied.
It may be noted among the advantages of this process and arrangement of
apparatus that as the film is taken from the hot cylinder by the cold cylinder all
scraping of hot cylinders by a "doctor" is obviated and consequently the sur-
face of such hot cylinder may be of expensive metal if necessary, as there is
practically no wear and tear or scraping action thereon.
If it be desired to hasten the evaporation and concentration one or more
cylinders and pans may be enclosed in a vacuum chamber.
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 improved means of evaporating and concentrating liquid solutions which
consists in continuously carrying from a bath upon a heated cylinder a film of
the solution to be concentrated, transferring said film to a cold cylinder and
removing the film therefrom.
2. The improved means of evaporating and concentrating liquid solutions
which consists in passing the solution through a series of baths containing a
series of heated cylinders continuously carrying from such baths upon the heated
cylinders a film of the solution to be concentrated and passing the more con-
centrated solution to the bath next in order and finally transferring the film from
the last heated cylinder to the surface of a cold cylinder and removing the film
therefrom.
3. The improved apparatus for evaporating and concentrating liquid solutions
and for obtaining solid substances therefrom, substantially as described.
Dated this 20th day of September 1899.
PHILIP M. JUSTICE,
55 and 56, Chancery Lane, London, Chartered Patent Agent,
For the Applicant.