Improvements in Purifying Brine
Year: 1890

page_text: Date of Application, 25th Mar., 1890-Accepted, 3rd May, 1890
COMPLETE SPECIFICATION.
Improvements in Purifying Brine.
A communication from abroad by CASSIUS C. PECK, of Warsaw, County of Wyoming,
State of New York, United States of America, Manufacturer.
I, JOHN CLAYTON MEWBURN of 55 and 56 Chancery Lane in the County of
Middlesex, Fellow of the Institute of Patent Agents, 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 the manufacture of salt from brine, and consists in a
process or processes of purifying the brine preparatory to evaporating it, by means of
the combined action of heat and carbonate of soda.
Sufficient heat is employed to precipitate the carbonates of lime, magnesia &c. and
cause the aggregation of solid particles held in suspension, and carbonate of soda is
used in connection with artificial heat to effect the precipitation of sulphates of lime,
magnesia &c. and chlorides of calcium and magnesium
It is common to heat water to its boiling point in order to free it from carbonate of
lime. Caustic soda and carbonate of soda have been used to soften water by causing
the precipitation of sulphate of lime, also the carbonate of an alkali in connection with
caustic alkali has been employed at temperatures of 140° to 158° Fahrenheit to
purify brine; as also carbonate of soda mixed with brine when cold, in connection
with jets of air for the same purpose, but so far as I am aware the method hereinafter
described has not been applied to nearly saturated solutions of salt and water used in
manufacturing salt from brine.
The presence of salt (Na Cl) in water has the effect of retarding chemical action, and
it becomes necessary to provide different conditions in purifying brine, from what are
needed in purifying ordinary water.
In other words strong solutions of brino constitute an essentially different liquid
from ordinary water for purposes of purification.
Thus certain temperatures applied to ordinary water will cause the precipitation of
nearly all the sulphate of lime which it contains, while the same temperatures will
effect the precipitation of very little sulphate of lime from strong brine..
By the process herein described new and valuable results are produced inasmuch as
the salt is freed from certain deleterious substances otherwise difficult of removal and
which have not heretofore been effectually removed. Such substances are sulphate of
lime and chloride of magnesium and of calcium. The two latter substances give to
salt a bitter and nauseating taste and by their deliquescence cause absorption of
moisture from the atmosphere after the salt has been manufactured.
In the accompanying drawings I show apparatus suitable for carrying out the
process practically, although I do not confine myself to the use of any special form or
construction of apparatus since it is obvious that various modifications may be made
therein without deviating from the essential features of the invention.
Figure 1 is a plan view of apparatus for carrying out the process.
Figure 2 is a side elevation with a portion of the tank broken away to show tho
interior arrangement of heating pipes and centrifugal pump.
Figure 3 is a cross section of one of the cooler pipes and
Figure 4 is a sectional plan through line - Figure 3 showing the interior con-
struction of the cooler pipes.
Feathered arrows indicate the circulation of steam supply, arrows feathered on but
one side show the direction of movement of the feed brine; and arrows without
feathering refer to the circulation of brine which has been treated in the tanks and
is flowing toward the filter.
A, A³, A² are three independent heating tanks for heating the brine under

page_text: treatment. B, B1, B2 are coils of pipe heated by a circulation of steam or hot liquid.
C, C1, C2 are vertically set centrifugal pumps provided with driving pulleys c, c¹, c²
for giving a rapid circulation to the brine in the tanks. D is a combined heater and
cooler which for the sake of convenience shall term a cooler, each pipe in which is
divided centrally by a diaphragm, Figures 3 and 4, into two divisions d¹ and d², the
inflowing current of brine passing through one division and the outflowing current
through the other division in opposite direction. E is a filter for separating, all
suspended solid matter from the brine after the latter has been treated by heat, and
carbonate of soda.
The operation is as follows: Brine is first delivered into one of the tanks, say tank A,
through feed pipe F by pump or other means of producing a head, the said
pipe being
supplied with valves f, ff, f3 for regulating the discharge of brine into the
several tanks. When the level of the liquid is as much above the coil B as is desired,
as indicated at a, Figure 2, a circulation of steam or hot liquid is produced in heating
coil B.
The supply of steam to coils B, B1, B2 is conducted through pipe H and the
return of water of condensation through pipe H', the supply being regulated by
valves h, h, h2, h3, h4, 1. The brine in tank A being heated to about its boiling
point a sufficient amount of carbonate of soda is added to cause the precipitation of
all the sulphate of lime, and the chlorides of magnesium and lime.
The carbonate of soda is introduced preferably in the form of solution, but may
be sprinkled into the tanks in the form of powder. In either case it is added
gradually to the brine in tank A in order that the chemical reactions may not be so
violent as to cause excessive foaming. The mixture of the carbonate of soda with
the brine and the rapid and uniform heating of the latter is facilitated by the
centrifugal pump which is driven by a belt upon pulley e, although the use of this
pump is not absolutely necessary.
The carbonate of soda may be added to the brine before the latter is heated, but
the chemical reactions are more complete and rapid when the brine is in a heated
state, at the time of mixing in the carbonate. It is also preferred to first free the
brine from bicarbonates of lime and magnesia before introducing the soda.
When brine is heated to near its boiling point soluble bicarbonates of lime &c: are
rapidly changed into insoluble carbonates by driving off in the form of gas the
carbonic acid which hold them in solution.
Heat also has the effect of aggregating the particles of solid matter held in
suspension in the brine, and in collecting such particles in flakes or light flocculent
masses.
In this condition the fine suspended matters will gradually settle to the bottom if
left undisturbed, or will be strained out if passed through a filter.
Carbonate of soda reacts with sulphate of lime and the chlorides of calcium and
magnesium producing insoluble carbonates and soluble sulphate of soda. The latter
is comparatively harmless in connection with making salt, while sulphate of lime
causes great loss and trouble by collecting on heating apparatus, and the chlorides of
calcium and magnesium greatly injure the quality of salt.
The combined action of heat and the carbonate of soda-the action of the latter
being intensified by the use of the former-serves to precipitate all elements which
prove noticeably injurious, either to the evaporating apparatus or to the quality of
the salt, the result being an important advance in the art of making salt.
:
After heating the brine and admixture of carbonate of soda it is preferred to stop
the centrifugal pump C and allow the liquid to remain in a quiescent condition
for a short time so that the floating solid matter may settle to the bottom of
tank A although when a filter as E is employed to eliminate all solid material
this period of rest may be dispensed with. When the brine is heated and the
centrifugal pump is in operation, the chemical reactions will be completed almost as
soon as the soda is added, and the brine may be drawn off through pipe F through
the cooler D to filter E, and thence through pipe, e, to evaporating apparatus, or
to a storage reservoir.

page_text: The draw-off pipe F₁ has a branch connecting with each tank, the said branches
being provided with valves f, ƒ³, ƒº.
The filter E is provided with secondary pipes F2, F³ for reversing the current and
cleaning the filter, which is nearly filled with a mixture of coke and sand. Any other
form of filter may be used, the essentials being complete removal of solid matter and
convenience in cleaning.
When valve f is opened and the heated brine in tank A allowed to flow out
through cooler D, a corresponding amount of fresh or untreated brine is delivered
by a suitable head through pipe F and cooler D into either tank A' or tank A².
The two different bodies of liquid pass through cooler D in opposite directions
in order that temperatures may be exchanged, the outflowing heated liquid
giving up its excess of heat to the inflowing brine so as to avoid loss of heat in case
the purified brine is to be conducted to a storage reservoir.
When, however, the purified brine passes directly from the heating tanks to the
evaporating apparatus, cooler D may be dispensed with. The operation is the same
with tanks A and A2 as with tank A. The process of refining or purifying can be
conducted with two tanks, but in general it is more convenient to employ three, so
that one tank may be cleaned while the process proceeds without interruption in
the other two tanks.
When time can be allowed for the separation of solid matter from the brino
by deposition, filter E may be dispensed with, but in such case cooler D) will be
needed to prevent the loss of a large amount of heat.
When loss of heat is of little account and time can be allowed for settling the
brine after treatment both filter E and cooler D may be dispensed with.
The most important feature of the invention is the heating of brine to near its
boiling point say to 200° Fahrenheit and upwards previous to mixing in it the
carbonate of soda, and effecting the mixture while the temperature is thus elevated.
This preliminary step of heating the brine to near its boiling point, by precipitating
the carbonates, avoids the necessity of using caustic alkali or brine, and at the
same time intensifies the chemical union of the carbonate of soda with the sulphates
and chlorides.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me and in what manner the same is to be performed,
I declare that what I claim is :-
1. The process of purifying brine herein set forth consisting in heating the brine
to about its boiling point and treating with carbonate of soda, substantially in the
manner and for the purpose described.
2. The process of purifying brine herein set forth, consisting in heating the brine
to about its boiling point, treating it with carbonate of soda in the manner and for
the purpose described, and subsequently cooling the brine by causing it to exchange
temperature with a supply of fresh brine, substantially in the manner and for the
purpose described.
3. The process of purifying brine herein set forth consisting in heating the brine
to about its boiling point, treating it with carbonate of soda in the manner described,
cooling the brine under treatment by causing it to exchange temperature with a
supply of fresh brine, and then filtering the brine substantially in the manner and
for the purpose described.
4. The process of purifying brine herein set forth, consisting in heating the brine
to about its boiling point, treating it with carbonate of soda in the manner described
and then filtering the brine, substantially in the manner and for the purpose
described.
Dated this 25th day of March 1800
J. C. MEWBURN.