Improvements in Means and Apparatus for Evaporating, Concen- trating, and Distilling Liquids, and Condensing the Vapours Produced therein.
Year: 1888

page_text: Date of Application, 4th Sept., 1888
Specification Accepted, 12th Oct., 1888
Improvements in Means and Apparatus for Evaporating, Concen-
trating, and Distilling Liquids, and Condensing the Vapours
Produced therein.
I CHARLES LATARCHE, of Lempire près Verdun (Meuse) in the Republic of France,
Gentleman, do hereby declare the nature of this invention and in what manner the samo
is to be performed to be particularly described and ascertained in and by the following
statement:
This invention has for its object effecting the evaporation distillation and concen-
tration of liquids at low temperatures and clates to an improved arrangement
of apparatus whereby these processes and the condensation of the resulting
vapours are enabled to be performed more efficiently and economically than
heretofore.
According to this system the liquid to be evaporated is not heated in the same
chamber or space in which the vapours are formed as heretofore practised but is
heated in a separate apparatus or outside this space which is reserved exclusively for
the purpose of evaporation or distillation and condensation the liquid being admitted
in a heated condition and gradually in proportion to the rate at which evaporation
takes place.
The liquid to be treated according to this invention being beated in a separate vessel
of any suitable construction is distributed by means of arrangements hereinafter
described over a series of wide parallel vertical plates in a chamber separate from
the heating vessel and descends the surfaces of these plates in thin films to the
lower part of the apparatus thus presenting a very large area of surface to
evaporation.
It is one of the chief distinguishing features of the invention that the liquid is
simply caused to pass quickly through the evaporating vessel where it parts with
the heat in evaporating after which the unevaporated part returns to the boiler or
heating vessel and there takes up a fresh supply of heat whereby a further
evaporation is produced as before the process being repeated until the operation is
terminated.

page_text: On the other hand a cold liquid employed for the condensation of the vapours
introduced at the same time into the evaporating chamber where it is spread over a
series of parallel vertical plates similar to and presenting the same amount of surface
as the plates herein before described the plates for the condensing liquid being arranged
alternately with the plates for the liquid to be evaporated. After flowing down
these plates the condensing liquid being heated in the condensing process may be
immediately conducted away to a refrigerator and when sufficiently cooled is
returned to the evaporating and condensing chamber being thus utilised again and
again.
The hot liquid and the cold liquid are caused to pass through the evaporating
vessel or chamber in such a manner that the hot films on one set of plates are
arranged opposite the cold films on the other set of plates the said films being
parallel with one another and separated by a narrow space only so that the
two liquids circulate continually in presence of one another without becoming
mixed and leave the apparatus through separate orifices in the same manner as they
entered.
The evaporating vessel is completely separate and independent of the heating
apparatus which operates under different conditions, unfavourable to the action of the
evaporator and condenser.
The heating is thus enabled to be carried on more advantageously and may even be
effected in the centre of the space where combustion takes place and the evaporating
vessel or chamber is enabled to act much more powerfully.
In place of a chamber performing a multiplicity of functions and encumbered by
the presence of a mass of liquid presenting only its comparatively limited area of
free surface available for evaporating-this improved arrangement enables an
effective apparatus to be constructed presenting an immense area of evaporating
surface in combination with an extremely small volume of liquid which is continually
renewed.
This method of evaporating by the mechanical circulation of the liquids enables the
area of evaporating and condensing or absorbing surfaces to be extended to any
desired amount and also enables these surfaces to be placed immediately opposite to
one another so as to still further increase their efficacy.
The heated liquid which trickles down the surfaces of the vertical plates being
relieved of the pressure of any superincumbent mass of liquid vaporises under the
influence of the smallest excess of temperature and the vapour given off meeting
with no resistance in the short space which it has to traverse is immediately absorbed
or taken up by the cold liquid which carries away the heat contained in the said
vapour.
Thus the evaporating vessel attains the maximum power possible and combines great
rapidity of action with a lowering of the temperature which enables the pressure to be
reduced waste of heat is thereby obviated this waste being in proportion to the
difference in the temperatures and the duration of the operations.
In order that my invention may be fully understood I will now proceed to describe
with reference to the accompanying drawings and by way of example only an apparatus
for concentrating sulphuric acid an operation which under the ordinary conditions has
heretofore been attended with peculiar difficulties owing to the elevated temperature
which corresponds to the boiling point of this liquid. This involved waste of heat and
the consumption of a relatively large quantity of fuel in proportion to the quantity of
water evaporated.
The general arrangement of the said apparatus for concentrating sulphuric acid
according to my invention is illustrated in elevation and partly in section in Figure 1
of the accompanying drawings and Figure 2 illustrates a detail of the same drawn to
a larger scale.
In the general view Figure 1 the boiler or heating vessel is marked A, and B is the
evaporating vessel or chamber. This apparatus also provided with pumps P. P¹ for
the acid and condensing water and an air pump Q whose functions are hereinafter
more fully described.

page_text: The heating apparatus A does not require special description being of any ordinary
or suitable construction. It may consist simply of a leaden pan or vessel and may be
heated either by steam or by the direct action of a furnace in the same way as when
evaporation at atmospheric pressure is performed but it should be observed that there
is no necessity for or advantage in arranging for a large area of free surface of the
liquid as no vapour is given off the temperature of the acid not being sufficient
to produce evaporation in the heating vessel. The vessel may consequently be
constructed solely with regard to utilising and transmitting the heat to the best
advantage.
The evaporating vessel B is arranged as indicated in the drawing at a higher level
than the heater A. and other parts of the apparatus in order to facilitate the extraction
of the liquids. The said evaporating vessel consists of a metal chamber or case
constructed of sufficient strength to resist the external pressure of the atmosphere and
of a size corresponding to the scale on which the operations are to be performed.
This chamber contains two series of parallel vertical plates a and b and arrangements
for separately distributing the liquids to the same. The series of plates a receiving
the acid are distinct from the series which receive the condensing water and are
arranged alternately with the latter in the interior of the chamber.
The plates a receiving the hot acid must be made of some acid proof material such
as glass for example. Although the temperature is somewhat high there is no danger
of cracking the glass provided that we take the precaution to heat it gradually by
causing the acid to circulate in the apparatus from the commencement of the heating.
In the present example both series of plates a and b are represented as being made of
glass.
Each plate being arranged in a vertical position in the apparatus is provided at its
upper edge with a thin strip of lead or platinum carrying a small distributing tube c
or d perforated with fine holes near the point of contact as indicated in Figure 2.
The distributing tubes e supply acid to the plates a and the tubes & supply cold
water to the plates b. All the distributing tubes are closed at one end and at the other
end communicate with supply pipes C. and D of larger diameter connected with the
pipes which supply the liquids to the apparatus the acid being introduced through the
pipe C and the cold water through the pipe D. By these means both the liquids are
introduced in a similar manner each liquid being conducted to the corresponding series
of distributing pipes.
The acid in the heating vessel and the cold water employed for condensation are
exposed to atmospheric pressure outside the evaporator but a somewhat high degree of
vacuum is obtained in the evaporating chamber B by means of the air pump so that
the liquids have a strong tendency to rush into the said chamber. Stop cocks or
valves placed upon the connecting pipes serve to moderate and regulate the flow
of liquids so as to produce if desired a mere trickling or sweating of the liquid
through the small holes in the distributing pipes.
The liquids are thus caused to spread themselves over each side of the glass
plates which are wetted over their entire surface. Adhering to these surfaces the
said liquids slide down to the bottom edges of the plates where they are received
in a double series of gutters e f where the two liquids are collected separately
and conveyed to separate collector pipes E. F. communicating with discharge
outlets a¹
Owing to the corrosive action of the acid the connecting pipes are made of lead
platinum glass or other acid proof material, but it is sufficient to cool the sides of
the evaporating chamber with lead and even this may be dispensed with as the liquid
does not give off acid vapours at the relatively low temperature employed.
The gutters e f are formed by a corrugated plate resting on the bottom of the
apparatus, each corrugation forms a channel open at one end and closed at the other
the open ends being arranged alternately with the closed ends so that two series of
gutters are obtained one series marked e opening at one side of the apparatus and
communicating with the discharge pipe a' and the other series marked opening at
the opposite side and communicating with the discharge pipe 6'. The form of these

page_text: corrugations is such that hollow spaces are formed between the gutters which serve
to prevent any prejudicial exchange of temperature between the two liquids which are
thus effectually separated.
The glass plates a and b rest on suitable supports arranged to maintain the plates at
the proper distance apart in the gutters.
The evaporating apparatus is closed in by a wide lid or cover B secured by bolts
which can be unscrewed when it is necessary to obtain access to the interior. The
interior of the apparatus communicates through a copper pipe g with an air pump Q
and is provided with a vacuum guage or indicator v. The sides of the chamber are
provided with strong panes of glass which enable the interior to be inspected and
show the distribution of the liquids and the level at which they stand in the
gutters.
The liquids are extracted or drawn off from the evaporator by means of two
pumps P. P which do not act directly on the liquids in the evaporating chamber. The
said liquids are collected separately in two vessels E. F. placed at a lower level into
which the liquids flow continuously from the gutters ef so that the said gutters are
never liable to overflow in case the working of the pumps is slowed or even temporarily
suspended.
The vessels E. F. are provided with gauge glasses n showing the level of the
liquid in each vessel and the internal pressure is made the same as in the evapo-
rator itself by means of two connecting pipes elf connecting the upper parts of
the vessels with the evaporating chamber so that it is unnecessary to connect the
vessels E. F. directly with the air pump. The pump P is employed to draw off
the acid and the pump P to draw off the water. The latter is of any ordinary
or suitable construction, but the pump P must be made of acid proof material or be
protected at those parts which come in contact with the acid the piston being of
stone ware or glass. These pumps draw the liquids from the vessels E. and F.
and deliver the acid to the boiler A and the water to a discharge pipe H or a
refrigerator.
In the arrangement illustrated hand pumps are employed, but it is evident that
steam or other motive power may be employed to work the pumps in apparatus
dealing with large quantities of liquid and suitable precautions are taken to prevent
the atmospheric pressure from acting on the pistons only in the direction of the
resistance and to cause it to act in the other direction also, so as to compensate
the pressure in order to avoid unnecessarily adding to the work to be done by the
motor.
In certain cases the pumps may be dispensed with altogether as will be readily
understood without special illustration. The example given in the accompanying
drawings is merely to explain the working of the invention in the simplest form. The
arrangement and construction may evidently be modified in various ways without
departing from the principle of the invention for example the liquid in the heater need
not be moved by atmospheric pressure.
The working of the apparatus will be readily understood from the foregoing descrip-
tion and reference to the drawings in which the direction of the circulation of the
liquid is indicated by arrows, the unevaporated portion of the acid being continually
returned to the heater A and the heated acid passing in a heated condition from
the heater to the evaporator B where it is exposed in a most effective manner
to the direct and almost instantaneous action of the evaporating surfaces. By these
means the evaporation is caused to proceed very rapidly and with a very small
expenditure of fuel.
The acid after concentration may be distilled an operation which has heretofore
been performed in the laboratories with great difficulty. For this purpose it is
simply necessary to substitute cold purified acid for the cold water hereinbefore
described. The acid vapours are formed and condensed without difficulty and the
same liquid may be used again and again for the condensation by causing it to
pass through a refrigerator where it is deprived of the heat taken up in the condensing
process.

page_text: The evaporation concentration or distillation and condensation of more volatile
liquids such as water or alcohol for example may evidently be performed in a similar
manner.
My invention is especially designed to utilize the fuel to the best advantage and
to obtain a rapid action which is the necessary consequence of the reduction of
temperature but in the numerous purposes to which the invention is applicable in
the arts there some in which the saving of fuel is of merely secondary importance
compared to the other advantages resulting from its employment. For example in
the operation of distilling alcoholic liquids which requires to be performed very
rapidly and at a low temperature the invention enables products to be obtained at
a relatively small cost of a quality superior to any that has been obtained by the
methods heretofore practiced.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The general arrangement and combination of the improved means and apparatus
for evaporating or concentrating and distilling liquids at low temperatures substantially
as hereinbefore described.
2. In evaporating or concentrating and distilling liquids at low temperatures the
arrangement whereby the heating apparatus or boiler A for the liquids to be treated
is rendered independent of the evaporating apparatus or chamber B where condensa-
tion is also effected the said combination of apparatus being arranged and
operating substantially as hereinbefore described and illustrated in the accompanying
drawings.
3. In combination with an independent or separate boiler or heater A an evaporating
chamber B containing two series of parallel vertical plates a and b over which by
means of tubes c and d the hot and cold liquids are separately distributed in thin films
separated by narrow spaces or intervals the said liquids being afterwards received
in gutters e and without being allowed to become mixed in the manner and for the
purpose substantially as hereinbefore described and illustrated in the accompanying
drawings.
4. In combination with the independent boiler a heating apparatus A and the
evaporating apparatus B, the collecting vessels E and F connected with the gutters e
and and in which the two liquids (liquid treated and water or product of
condensation) are separately received, the said liquids being subsequently transferred
to the heating apparatus A and to a pipe H leading to a refrigerator respectively
substantially as hereinbefore described and illustrated in the accompanying drawings.
Dated this 4th day of September 1888.