Improved Vacuum Evaporating Apparatus for Separating Common Salt (Chloride of Sodium) from Solutions especially from Brine.
Year: 1899

page_text: Date of Application, 17th Aug., 1899
Complete Specification Left, 10th Apr., 1900-Accepted, 17th Aug.,
1900
Improved Vacuum Evaporating Apparatus for Separating Common
Salt (Chloride of Sodium) from Solutions especially from Brine.
I, GERHARD NICOLAAS VIS, of Schweizerhalle, near Basel, Switzerland, Doctor
of Philosophy and Chemist, do hereby declare the nature of said invention to be
as follows:-
The present invention relates to the separation of common salt (chloride of
sodium) from solutions, especially from brine, and its object consists in an improved
apparatus whereby the evaporation of brine is enabled to be operated by the aid
of a vacuum.
Multiple effect apparatuses as heretofore devised for obtaining solid products
from liquids are substantially concentrating apparatuses, that is to say, the liquid
to be evaporated is concentrated in the vacuum apparatus, and the substance to be
obtained deposits after letting off the liquid as the same cools.
For the separation of common salt (chloride of sodium) these apparatuses are
unsuited as usually constructed because common salt is only slightly more soluble
in hot than in cold water, that is in other words, because the saturation point is
soon attained, especially as most brines are already completely or highly saturated
with common salt. and consequently the evaporation of a very small quantity of
water causes a separation of salt to take place.
It is therefore desirable to so organize or devise the apparatus that: -1st; the
salt separated out can be removed from the boiling brine, and 2nd; it is removed
in such a manner as to prevent the salt from adhering to the heating pipes.
The first requirement is accordingly attained in the present invention by the
use of a so-called open vacuum specially constructed for this purpose, and the
second requirement is fulfilled by admitting air periodically which causes the
column of brine to sink suddenly and consequently produces a removal of the salt
from the boiling brine.
In order more clearly to set forth the invention let us take an apparatus with
triple action by way of example, such as that illustrated diagrammatically in the
accompanying drawing.
The three evaporators A, A1, A2, which may be of a circular or rectangular shape
and provided with valves i, i, at the top as usual, are in this case constructed
with horizontal heating pipes h. There is no reason, however, why vertical pipes
should not be employed; or the heating of the evaporators may be effected by trans-
mission through the walls of the vessel either entirely or in combination with heat-
ing pipes, and this transmission may also take place through the sides of the cone.
A condenser B is connected with the evaporator A2, or in general terms, with the
last evaporator of the series.
The vessels A, A1, A2 are exhausted by means of one or more suitable pumps in
such a way that there is a difference of the level of the brine which for instance
in A amounts to about 4 metres, in A' to about 6 metres, and in A2 to about
8 metres. All these vessels communicate at the bottom by means of a pipe (C,
C, C2) fixed on the cone, with a common reservoir D (or into three separate reser-

page_text: voirs, one for each vessel), which is filled from a main reservoir not illustrated in
the drawing.
Said reservoir D) is chosen as small as possible, on the one hand because the salt
collects better, and on the other hand for the following reason: the operation
begins by exhausting the vessels sufficiently so that the brine can fill up the same
to the proper level by rising therein from the reservoir D. The evaporator or
boiler A is then supplied with direct steam of from 100° to 130° Centigrade. The
brine in A becomes boiling, and the steam developed there from the brine in A
passes over into the heating tubes h of the evaporator A¹ and causes the contents
of same to boil. The steam developed in A¹ passes over into the
heating pipes / of boiler A2 and causes, the brine contained in A2
to evaporate.
If the brine contained in the reservoir D were allowed
to continually compensate for the evaporated liquor by ascending into the boilers
through the pipes C, C, C2 under the suction of the vacuum maintained in the
boilers, without paying any further attention to the operation, then the heating
pipes in A, A1, A2 would very soon be covered with a crust of salt, consequently
the transmission of heat through the pipes would be reduced the more and more
and in a short time all the vessels would be encrusted with salt, and evaporation
would cease.
In order to avoid this, each boiler is provided at the top with a pipe a, al or a³
respectively for the admission of air, said pipes starting from a common point,
for instance from a table fixed to the wall of the locality in which the boiler series
is placed, where they are provided, each with a cock. By opening these cocks
periodically, air rushes into A, A1, A2 respectively, and the vacuum being thereby
destroyed, the brine is caused to sink suddenly, and by this sudden movement of
the brine, the salt separated out, is caused to fall down through the pipes C, C¹, C³
into the reservoir D.
By means of this admission of air into boiler A the brine there leaves off boiling
so that no hot steam is led into the heating pipes of the boiler A', consequently
the brine in the latter ceases to develop steam, so that no counter-pressure to the
action of the pump is produced. The consequence would be a rising of brine
from the reservoir D into the boiler A¹; the same occurrence would be repeated in
boiler A². In order to obviate this, that is to attain a constant height of brine
in the boilers A, A1 and A2, the pipes d, and d² are applied, one for each boiler.
They discharge with their upper ends into the boilers a little above the normal
level of the brine, and with their lower ends they dip into the brine contained
in the reservoir, said lower ends being cut sloping. An excessive rising of the
level of the brine either in A, A' or A2 causes the level of the brine in the
reservoir D to sink until the lower ends of the pipes d, d'or d² become free, when
air rushes through said ends into the vessels and causes the brine to sink, so that
the described difference of level is immediately re-established.
Obviously the same object may be attained by providing valves at the lower
ends of the pipes C, C¹, C².
In order that the level in the reservoir D can easily be lowered so as to quickly
uncover the pipes d, d', d, the reservoir D should be as small as possible, and in
order that the boilers can be filled from the reservoir D, the latter should be con-
nected with a second reservoir D¹ by means of a wide pipe D2 provided with a
cock or other means for opening and re-closing. This second or main reservoir D'
is only made use of when the vessels are filled or entirely emptied. The pipes d,
d', d, or compensating pipes, may also be made use of instead of the tubes a, a, as
for causing the brine to sink suddenly for the purpose of removing from the
boilers the salt separated out. This is effected by creating such a vacuum by
means of the air pump in the boilers, that the pipes d, d¹, become uncovered
from the brine being sucked into the boilers.
As known even when operating upon a perfectly pure brine, that is, one com-
pletely free from gypsum, part of the salt separated out, adheres to the heating
tubes h, and forms there an incrustation which prevents the proper transmission

page_text: of heat, so that after a few days the output becomes unremunerative. In order
to avoid this I provide for a periodical removal of said incrustation by the follow-
ing device:-
The compensating pipes d, d, are connected each by means of a three way
cock respectively e, el, e with a pipe respectively f, f¹, få starting from the top
of the reservoir D. When after a twelve hours work or there about salt is deposited
on the walls and pipes of the boilers, the steam is shut off for a short time and
thus the brine contained in the boilers A, A¹, and A² caused to fall back into the
reservoir D, the communication of which with the second reservoir D¹ has been
established. Then the pipes C, C, C are closed for a short time by means of a
plate placed on their mouth by means of a rod, the three way cocks e, e', e 80
turned that communication is established between the pipes f and d (or f¹ and d
or and respectively) when brine is drawn again from the reservoir into the
boiler through f, d (or f¹ d' or fd). After refilling, the plates are removed
from the tubes C, C1, C2 and the cocks c, c¹, re-closed. Obviously the pipes f,
f, may, if preferred, directly discharge into the boilers instead of being con-
nected by cocks with the compensating pipes d, d', d³.
This refilling of the boilers with fresh brine, without the necessity of emptying
the reservoir D into which the vessels A, A1, A2 discharge, can also be obtained
by placing (after the cock e, e¹ or e² respectively has been turned so as to establish
the communication between the pipes f and d (f' and d, f and d²) a V-shaped
pipe g with one of its legs under the pipe C so as to receive the same (as shown
in dotted lines for the boiler A). the other leg being supplied with fresh brine for
instance by means of a feeding tube q' as shown in dotted lines. After the vessels
have been refilled with fresh brine the V-shaped pipe g is removed.
The apparatus is operated again in the usual manner. The fresh brine in
becoming hot dissolves the incrustation of salt which has been accumulating
during 12 hours, so that the operation can go on for another 12 hours. This
periodical re-dissolving of the incrustation of salt allows of working longer than
was formerly the case.
It is understood, that the improvements described can also be applied to appa-
ratuses with double or single action that the reservoir D can be provided with
an automatic device for discharging the separated salt to the outside, and that the
boilers are supplied with vacuum gauges.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.
improved Vacuum Evaporating Apparatus for Separating Common
Salt (Chloride of Sodium) from Solutions especially from Brine.
I, GERHARD NICOLAAS VIS, of Schweizerhalle, near Basel, Switzerland, Doctor
of Philosophy and Chemist, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
The present invention relates to the separation of common salt (chloride of
sodium) from solutions, especially from brine, and its object consists in an improved
apparatus whereby the evaporation of brine previously freed from gypsum, is
enabled to be operated upon by the aid of a vacuum in a by far more advantageous

page_text: manner than heretofore, and especially on the so called "multiple" effect"
principle.
Multiple effect apparatuses as heretofore devised for obtaining solid products
from liquids are substantially concentrating apparatuses, that is to say, the liquid
to be evaporated is concentrated in the vacuum apparatus, when the liquid is
allowed to cool to separate out the substance.
For the separation of common salt (chloride of sodium) these apparatuses are
unsuited as usually constructed, because common salt is only slightly more soluble
in hot than in cold water, that is, in other words, because the saturation point is
soon attained, especially as most brines are already completely or highly saturated
with common salt. and consequently the evaporation of a very small quantity of
water causes a separation of salt to take place, so that after a comparatively short
period of boiling, the separated salt will cover the heating pipes to such an extent
as to render them inoperative, much of the salt being, moreover, caused to firmly
adhere to the said pipes.
In order to render the vacuum boiler available to the separation of salt from
brine it is therefore necessary to so organize the same that the salt separated out
can be periodically discharged from the boiler and the incrustations removed from
its heating pipes and walls. Moreover, with apparatuses working on the so-called
"multiple effect" principle, a provision has to be made whereby the normal height
of level is automatically maintained in the series of boilers. This is important for
the reason that the level at which the brine stands in a boiler determines the boil-
ing point and thus the temperature of the steam generated in this boiler and con-
ducted into the heating pipes of the next boiler of the series.
To obtain the above results the boiler, which is constructed with a lower conical
end communicating with a brine reservoir or charging-reservoir that is open to
the atmosphere and receives the brine from a main reservoir, is
1. Provided at its top with an air cock,
2. With a tube descending from a point slightly above the heating system down
in a reservoir filled with fresh brine preferably to a higher level than the charging
reservoir or in the said main reservoir, and, closed by means of a cock during the
operation of the evaporating process, and
3. With a tube descending from a point slightly above the heating system down
into the said charging reservoir to a point slightly below the normal level of
brine, the open end of this pipe being preferably cut sloping. It is obvious that
with the normal vacuum in the boiler this tube will be filled with brine only up
to about the level of brine then existing in the boiler so as not to discharge.
If it is desired to discharge the salt from the boiler, said air cock is opened
whereby the brine in the boiler is caused to rapidly sink, pushing the separated
salt down into the reservoir; when the air cock is re-closed, brine is anew sucked
n the boiler from the charging reservoir.
If from any cause the level of brine in a boiler rises, the pipe dipping into the
brine of the charging reservoir will become unsealed, air will rush into the boiler
and reduce the vacuum so that the level of brine is caused to sink until said pipe
is sealed again.
If it is desired to remove incrustations, the pump is stopped, so that the brine is
discharged from the boiler in the charging reservoir, when the opening in the
lower end of the boiler is closed, the cock of the pipe cited under head 2 opened,
and the pump started; at present fresh brine is sucked into the boiler from the
main reservoir or other reservoir connected with said pipe, and discharged above
the heating system until the boiler is refilled up to the normal level when the
said cock is re-closed said opening re-opened and the boiling continued. The
brine discharged above the heating system in running down the latter and the
wall of the boiler dissolves any salt crusts formed thereon.
In order more clearly to set forth the invention I proceed to describe the same
with reference to an apparatus with triple action illustrated diagrammatically in
the drawing left with the Provisional Specification.

page_text: The three evaporators A, A', A³, which may be of a circular or rectangular shape,
are in this case constructed with horizontal heating pipes h. There is no reason,
however, why vertical pipes should not be employed, or the heating of the evapo-
rators may be effected by transmission through the walls of the vessel either entirely
or in combination with heating pipes, and this transmission may also take place
through the sides of the cone. A condenser B is connected with the evaporator A³,
or in general terms, with the last evaporator of the series.
The vessels A, A', A2 are exhausted by means of one or more suitable pumps
in such a way that there is a difference of the level of the brine, which for instance
in A may amount to 4 metres, in A¹ to about 6 metres, and in A2 to about 8 metres.
All these vessels communicate at the bottom by means of a pipe (C, C1, C2) fixed
on the cone, with a common reservoir D or preferably into three separate reservoirs
one for each vessel, which is or are open to the atmosphere and filled from a main
reservoir D¹.
The operation begins by exhausting the vessels sufficiently so that the brine can
fill up the same to the proper level by rising therein from the charging reservoir D
through the pipes C, C1, C2. The evaporator or boiler A is then supplied with
direct steam of from 100° to 130° Centigrade. The brine in A becomes boiling,
and the steam generated from the brine in A passes over into the heating tubes h¹
of the evaporator A¹ and causes the contents of the same to boil. The steam gene-
rated in A passes over into the heating pipes h² of boiler A² and causes the brine
contained in this boiler to evaporate. If the brine contained in the reservoir D
were allowed to continually compensate for the evaporated liquor by ascending
into the boilers through the pipes C, C1, C2 under the suction of the vacuum main-
tained in the boilers. without paving any further attention to the operation, then
the heating pipes h in A. A1, A2 would very soon be covered with a crust of salt,
consequently the transmission of heat through the walls of the pipes would be
reduced more and more, and in a short time all the vessels would be incrusted
with salt and the operation would cease.
In order to avoid this each boiler is provided at the top with a pipe a, a, or a²
respectively, for the admission of air. said pipes starting from a common point,
for instance from a table fixed to the wall of the locality in which the boiler series
is placed. where they are provided each with a cock. By opening these cocks
periodically, air rushes into A, A¹ or A2 respectively, and the vacuum being thereby
reduced the brine is caused to sink suddenly and by this sudden movement of the
brine, the salt separated out, is caused to fall down through the pines C, C¹. 02
into the reservoir D. I prefer to so regulate the admission of air that the brine
is allowed to sink by 20 centimetres or thereabout.
By means of this admission of air into boiler A the brine there leaves off boiling
so that no hot steam is supplied to the heating pipes of the boiler A¹, consequently
the brine in the latter ceases to develop steam, so that no counter-pressure to the
action of the pump is produced. The consequence would be a rising of brine
from the reservoir D into the boiler A¹, the same occurrence would be repeated
in boiler A2. In order to obviate this, that is to maintain a constant height of
brine in A, A1 and A2. pipes d. and are applied one for each boiler. These
pipes discharge with their upper ends into the boilers a little above the normal
level of the brine and with their lower ends they dip into the brine contained in
the reservoir, said lower ends being cut sloping. It is obvious that with the nor-
mal vacuum in the boilers, the pipes d, d. d will be filled with brine only up
to about the normal level of brine in the boilers so as not to discharge brine in
the latter. Any excessive rising of the level of the brine either in A, A¹ or
in A causes the level of the brine in the reservoir D to sink until the lower end
of the pipes d, or d² becomes free, when air rushes through said ends into the
vessels and causes the brine to sink so that the desired difference of level is imme-
diately re-established.
In order that the level in the reservoir D can easily be lowered so as to quickly
uncover the pipes d, d, the reservoir D should be as small as possible, and in

page_text: order that the boilers can be fed from the reservoir D, the latter should be con-
nected with the main reservoir D¹ by means of a wide pipe D2 provided with a cock
or other means for opening and re-closing.
The pipes d, d', d² or compensating pipes may also be made use of instead of
the air-tubes a, a', a² for causing the brine to sink suddenly for the purpose of
removing from the boilers the salt separated out. This is effected by creating such
a vacuum by means of the air pump in the boilers that the pipes d, d¹, d² become
uncovered from the brine being sucked into the boilers.
In order to periodically remove the incrustations formed on the heating tubes h
by means of fresh brine the upper portions of the compensating pipes d, d', d²
are connected by means of three-way cocks e, e', e², with pipes f, f, f2, starting
from the main reservoir D¹ (or a special reservoir filled with fresh brine preferably.
up to a higher level than the normal level of brine in the charging reservoir).
During the operation of the evaporating process said cocks are so turned as to estab-
lish communication between the boilers and the charging reservoir through the
pipes d, d, d, whilst the pipes f, f f are closed.
When after twelve hours or thereabout salt is deposited on the walls and pipes
of boilers, the steam is shut off for a short time and thus the brine contained in
the boilers A, A' and A² caused to fall back into the reservoir D. Then the
pipes C, C and C² are closed for a short time by means of a plate placed against
their openings by means of a rod and the three way cocks e, e¹, 2 so turned that
communication is established between the pipes f, f¹, f, and the upper portions
of the pipes d, d, &, whilst the lower portions of same are closed, when the pump
is re-started and fresh brine is drawn directly from the reservoir D into the boilers
through f, f, 72 and the upper portions of d d d², and discharged into the same
from above the heating system, which brine in flowing down over the hot pipes
and the inner walls of the boiler will readily dissolve away any salt crusts formed.
After refilling, the said plates are removed from the pipes C, C1, C2, the cocks e, c¹, e
are turned back to shut off the pipes f, f, f2, and to re-establish communication
between the upper portions of the pipes and the charging reservoir, and
the boiling is proceeded with as before for another twelve hours. This periodical
re-dissolving of the salt crusts allows of working for a considerably longer period
than was formerly the case. Obviously the pipes f, f¹, f2 may if preferred directly
discharge into the boilers instead of being connected through cocks with the
pipes d, d, d. This refilling of the boilers with fresh brine can also be obtained
by placing (after the cock e, e, e respectively has been turned so as to close both
the pipes and f, respectively, d¹ f', and f with regard to the boiler), a V-
shaped pipe g with one of its legs under the pipe C, C or C2, so as to receive the
same, the other leg being supplied with fresh brine, for instance by means of a
feeding tube g¹ as shewn in dotted lines for the boiler A. After the vessel has
been refilled with fresh brine the V-shaped pipe g is removed, and the cock e,
respectively e¹, e², so turned as to re-establish communication between the boiler
and the charging reservoir D) through pipe d, respectively, d¹, d whilst the pipe f,
respectively f, is left closed.
It is understood that the improvements described can also be applied to appa-
ratuses with double or single action, that the reservoir 1) can be provided with an
automatic device for discharging the separated salt to the outside, and that the
boilers are supplied with vacuum gauges.
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. A vacuum apparatus for separating common salt from solutions especially
from brine having the characteristic features that the boiler, communicating at
its lower end with a charging brine reservoir communicating with the air (so-called
open vacuum) and fed with brine from a main reservoir is provided
a) With an air cock a respectively a¹, a³) at its top part for the purpose of

page_text: discharging the separated salt into said reservoir by means of periodical varia-
tion of the vacuum.
b) With a pipe d (respectively d, d²) starting from a point above the heat-
ing system and descending into said charging reservoir to a point somewhat
below the normal level of brine of same for the purpose of maintaining a con-
stant level of brine in the boiler, and
c) With a pipe f (respectively f¹, f2) starting from a point above the heat-
ing system and connected by means of a cock with a reservoir containing
fresh brine, for the purpose of periodically filling the boiler with brine from
above the heating system for removing incrustations: substantially as
described.
2. In an apparatus as claimed the substitution for the pipe cited under c), of a
emovable V-shaped tube, as and for the purpose stated.
3. In an apparatus as claimed the substitution for the air cock of the pipe cited
nder b), the pump being periodically caused to work at a higher speed, as and
or the purpose stated.
Dated the 24th day of Tul. 1000