IMPROVEMENTS IN THE MODE OF EVAPORATING SALINE SOLUTIONS, AND IN APPARATUS USED FOR THAT PURPOSE
Year: 1878

page_text: "
LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for
the Invention of IMPROVEMENTS IN THE MODE OF EVAPORATING SALINE
SOLUTIONS, AND IN APPARATUS USED FOR THAT PURPOSE." A communica-
tion from abroad by Paul Piccard, of the City of Lausanne, Canton de Vaud,
in Switzerland. Engineer.
Sealed the 27th September 1878, and dated the 6th August 1878.
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 6th August 1878.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN THE
MODE OF EVAPORATING SALINE SOLUTIONS, AND IN APPARATUS USED FOR THAT
PURPOSE." A communication from abroad by Paul Piccard, of the City of
Lausanne, Canton de Vaud, in Switzerland, Engineer.
This Invention has for its object improvements in the mode of evaporating saline
solutions, and in apparatus used for that purpose, and relates especially to the
apparatus described in the Specification of a Patent granted to the said Paul Piccard,
dated the 9th day of January 1877, No. 92.
According to this Invention the heating of the liquid to be evaporated and its.
evaporation are conducted in different vessels, so that the solution during the
operation of heating, whether it be by a circulation of vapour in a tubular, lenticular,
or other apparatus, or by other means, cannot deposit any part of the salt which
it contains, and so that the deposit of the salt shall take place in a separate vessel
by rapid vaporisation. This is effected by the application of a well-known principle,
and consists in maintaining in the heating apparatus an artificial pressure, and
causing expansion to take place at the entrance of the vaporising vessel.

page_text: The annexed Drawing will render intelligible and practicable the manner in which
it is preferred to carry out this process.
The apparatus consists of a boiler, by preference a tubular boiler A, and a vessel B
called the evaporator. A discharge pipe T, T, furnished with two valves V and V¹,
one above the other, and having a space S between them, is fixed at the bottom of
the evaporator, so that by alternately closing one valve and then opening the
other the salt deposited in the evaporator can be withdrawn as described in the
Specification of the Patent before mentioned without putting the evaporator into
communication with the exterior air.
The lower end of the discharge tube T, T, is prolonged by means of a branch 1
K, K, ascending obliquely to the same height as that of the valves, and. is open at.
the top. The column of water in this oblique branch therefore balances the column
in the vertical branch, and prevents all disengagement of vapour. The salt which
falls into the elbow is drawn out in any suitable manner.
P
The tubes and ends of the tubular boiler are filled with the solution. to be 1
vaporised. The evaporator B is also partially filled with the same solution. At a
point situated below the surface of the liquid in the evaporator B-there is a pipe C
leading to the bottom of the boiler A, and at any point in this pipe there is a pump
of any suitable construction. This pump may be replaced by any apparatus which
will permit the solution to pass from the evaporator B to the boiler A without 2
allowing the pressure which exists in A being transmitted to B. From the top of
the boiler A there is a pipe D leading to the evaporator B through an orifice O.
The size of this orifice may be regulated in any suitable manner either by a needle,
by a valve, by a plug, or may be kept uniformily of the same size.
The evaporator B is furnished with a dome I, from which a pipe F passes 2
for the escape of the vaporized products, it is also furnished with a water
gauge (not shewn in the Drawing). The pipe C carries another pipe t for the
introduction of the solution to be evaporated.
The evaporator B is traversed by a shaft E, E, which carries one or more screw
blades, which by their rotation carry into the tube T, T, the salt deposited by the 3
evaporation.
The boiler A is furnished with two pipes G and H, which communicate with the
space between the tubes, the pipe G receives the vapour for heating the solution,
the pipe H allows of the escape of water produced by the condensation of the
heating vapour.
The boiler and evaporator A and B are cased with any badly conducting sub-
stance; they are made of sheet or cast iron, or other substance, according to the
nature of the solution to be treated.
3
The boiler A may be vertical or horizontal, tubular, or of any other construction
which will attain the same ends. Thus the liquid to be heated may be on the ex- 4
terior of the tubes, or a boiler heated externally may be used in the same way.
The evaporator B may be horizontal, as it is represented in the Drawings, or it
may be vertical; may also be of any desired form, provided that the salt can fall
into the pipe T, T, or can be brought there by mechanism. This mechanism, in
place of being rotative, as is shewn, may be formed to have a rectilinear reciprocating 4
to-and-fro movement, or other movement given to it; or in some cases it may even
be entirely omitted, according to the shape of the evaporator, or according to the
greater or less adherence of the salt produced.
The means employed for maintaining the liquid under pressure whilst it is being
heated in the boiler A. may, as shewn in the Drawing, be a pump, which draws the 5
solution from the evaporator, and then forces it along the pipes to the boiler A, and
from thence through the orifice O into the evaporator B. In.this case by means of
the pump
Pa pressure can be obtained in the liquid which fills the boiler A, such
that no vaporisation of this solution will be possible. Or to make the solution pass:
from the evaporator B to the boiler A the latter may be placed at a lower level than 5
the evaporator, and by employing an intermediate vessel communicating alternately.

page_text: with one and the other, but never with both at the same time. Every time that
communication is opened between B and the intermediate vessel a certain quantity
of the solution passes from the first to the second until the level of the liquid in the
intermediate vessel is the same as that in the evaporator. In the same way by
opening the communication between the intermediate vessel and the boiler A liquid
passes from the intermediate vessel to the boiler until the level of the liquid in these
two vessels is the same.
:
To allow liquid to flow freely from the evaporator to the intermediate vessel, and
from the intermediate vessel to the boiler, two pipes are led from the top of the
intermediate vessel, one leading to the steam space in the evaporator, and the other
to the steam space in the boiler; two other pipes below the liquid level also pass
from the intermediate vessel, one to the boiler, the other to the evaporator. On all
the pipes are valves.
'
As the valves on the two pipes leading from the intermediate vessel to the
boiler are closed, the valves on the two pipes leading to the evaporator are opened,
and vice versa. Thus the movements of the liquid take place simply by the action
of gravity, and without the necessity of having recourse to a pump. The pressure
necessary for forcing the liquid past the orifice O is obtained by the heating of the
solution in the boiler A. The solution as it is heated itself produces a limited quantity
of vapour, which maintains the solution under pressure until the pressure is brought
to a point sufficient to expel a certain quantity of liquid through the orifice O into
the evaporator B. The admission of the solution by means of the intermediate
vessel being repeated as frequently as desired, and the heating of the solution being
continued, the expulsion of the solution heated under pressure in the boiler A can
also be regulated as desired.
Other means than those above described may, as before stated, be adopted for
causing the solution from the evaporator to be forced into the boiler without
allowing the pressure in the boiler to be transmitted back to the evaporator.
The action of the apparatus is as follows:-Vapor at a higher temperature than
the liquor in the evaporator is introduced by the pipe G to the boiler into the
space around the exterior of the tubes, at the same time the pump, or the other
apparatus by which the solution to be evaporated is brought from the evaporator B
to the boiler A, is set.in action. The solution is heated by traversing the tubes of
the boiler, and then escapes into the evaporator B by the orifice O either by reason
of the pressure caused by the pump to the pressure due to the partial vaporization
of the liquid or otherwise. The size of the orifice. O is so regulated that the
pressure of the liquid behind the orifice O is higher that that in the evaporator B.
When the pressure of the liquid is obtained by means of a pump, the pressure
can be raised sufficiently high to prevent any evaporation in the solution, and thus
prevent any deposit of salt. When the pressure is caused by the disengagement of
vapour in the solution itself, the volume of the vapour produced is so regulated that
a deposit of salt is not formed. The augmentation of solubility produced by the
elevation of the temperature of the solution is used for this purpose; that is to say,
that the solution being heated to a higher degree can dissolve a larger quantity of
salt than would be deposited by reason of the formation of a certain quantity of
vapour.
In the evaporator the pressure is less than in the pipe D which leads to it from
the boiler by the difference of pressure caused by the passage of the liquid through
the orifice O.
As the heated solution under pressure in the boiler A escapes from the orifice it
passes suddenly to a lower pressure, and is partially vaporized on entering the
vaporiser B. The part of the solution which is not vaporised circulates gently in
the evaporator. until it is again sucked into the outlet pipe C, and is then reforced
by the pump P into the boiler A, and then again to the orifice O as before. The
solution is thus maintained in continuous circulation between the boiler A and the
evaporator B. In passing the orifice O it continually vaporises a part when the

page_text: salt which is separated is deposited on the bottom of the evaporator, and is
continually drawn into the discharge pipe T, T,' by the screw blades on the
shaft E, E.
For withdrawing the salt without putting the evaporator into communication
with the exterior air, it is only necessary to first close the valve VI, and then open
the valve V, the salt then falls to the bottom of the pipe K, K, from whence it is
withdrawn either by hand, or by a rake, or by other mechanical means.
To avoid the entrance of air into the apparatus during the movement of the
valves the level of the solution in the pipe K, K, is maintained at a height such that
the lower end of the pipe T, T, is never uncovered. When the removal of the salt
is finished the valves are replaced to their former position until the next removal.
During the working of the apparatus the level of the solution in the evaporator
B is maintained at approximately the same point.
The water condensed between the tubes of the boiler A is generally at a tempera;
ture more elevated than that of the solution coming by the supply pipe t, and is
used to heat the latter by means of a worm, a known apparatus, which is not here
shown, as it has nothing to do with the present Invention.
The apparatus extracts with great economy of fuel all salts which are extracted
from solutions.
Hydraulic power or any other motive power can be applied to the apparatus in
the well-known manner, which consists in compressing the vapour resulting from
the evaporation in order to again raise its temperature.
The vapour which escapes by the pipe F is drawn away by a pump, which
compresses it and forces it thus compressed into the boiler A. In consequence of
this compression the vapour between the tubes of the boiler A is at a temperature
more elevated than that of the solution contained in the tubes of the boiler A. The
vapour thus reheats the solution, and the solution afterwards vaporizes in the
evaporator B. A continuous evaporation of the solution thus results without
the expenses of fuel.
The arrangement of the apparatus above described allows of a continuous ex-;
traction of the salt, produces without interrupting or disturbing the working of the
apparatus.
.
According to the temperatures and pressures at which the apparatus is worked,
the liquid condensed between the tubes of the vessel A will escape by the pipe H
either by the influence of the interior pressure, if this is greater than the
atmospheric pressure, or by means of a pump if there is a relative vacuum in the
apparatus.
When there is not any cheap motive power at disposal a continuous series of
apparatus may be used, the boiler of the first apparatus being heated by steam
from an ordinary steam generator, and the steam afterwards being caused to pass to
the boiler of the next apparatus, and so on until from the last evaporator it passes
to a condenser.
An ordinary air pump may be used to remove the water of condensation, the
water of injection, and the air from the condenser in general; it will be driven by
a steam engine, the vapour which escapes from which will with a certain quantity
of the vapour of the generator pass into the first boiler A; the extraction of the
water of condensation from the various vessels A will take place as in the
preceding case.
Having thus described the nature of the Invention and the manner of performing
the same, I would have it understood that what is claimed is,-
First. The continuous process of evaporating saline solutions, the solutions being
heated under pressure, then forced into an evaporator, where they are relieved from
pressure and allowed to deposit salt, and then again forced back into the boiler,
to be again heated, whilst at the same time the deposited salt can be drawn
off from time to time from the evaporator, substantially as herein-before
described.
4

page_text: Second. The combined arrangement of apparatus for continuously evaporating
saline solutions, substantially as herein-before described.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Sixth of August, in the year of our Lord One thousand eight
hundred and seventy-eight.
SYDNEY PITT. (L.S.)