Improvements in or connected with Evaporating or Concentrating Apparatus.
Year: 1892

page_text: Date of Application, 16th July, 1892
Complete Specification Left, 17th Apr., 1893-Accepted, 20th May, 1893
PROVISIONAL SPECIFICATION.
Improvements in or connected with Evaporating or Concentrating
Apparatus.
We, FRANK WALTER SCOTT, of 44, Christian Street, Commercial Road, in
the County of London, Engineer, ERNEST GEORGE SCOTT, of 67, Lord Street,
Liverpool, in the County of Lancaster, Consulting Chemist, and FRANK WALTER
SCOTT Junior, of 44, Christian Street, aforesaid, Engineer, do hereby declare the
nature of this invention to be as follows:-
This invention relates to evaporating or concentrating apparatus.
Hitherto it has been impracticable to evaporate or concentrate in multiple effect
apparatus liquids such as caustic soda, caustic potash, silicate of soda and zinc
chloride which boil at high temperatures. Furthermore we have found that the
internal circulation and consequent evaporation of the liquor in the last effect is
not nearly as good as in the first, and this we ascribe to the fact that, although the
boiling point of the liquor is reduced in the last effect, by means of vacuum,
so as to leave the same margin of heat as there is between the boiling point of
the liquor and the surrounding steam in the first effect, the margin of heat in the
last effect is not sufficient to raise the liquor to its boiling point as this boiling
point is higher than that of the liquor in the first effect owing to the increased
viscosity and density of the liquor.
The object of our invention is to overcome both of these difficulties; that is to
say, the difficulty of dealing with liquids boiling at high temperatures and the
difficulty of the circulation, and we overcome the first difficulty by superheating.
the steam in order to raise it to the required temperature, and the second by causing
the steam to circulate in the reverse direction to that in which the liquor is
circulated so that the hottest steam first acts upon the liquor having the highest.
boiling point.
In carrying out our invention we advantageously use two vessels to constitute the
first effect, the said two vessels having one continuous heating system and one *:
vapour outlet to the second effect.
The steam, which may be either exhaust or high pressure steam, after passing
through the superheating apparatus enters the heating system of the first of the
two vessels of the first effect and there causes the liquor under treatment to
evaporate. After passing around the heating tubes of this vessel through which it
may be guided by suitable battles, the steam, which has been cooled nearly to the
temperature of the boiling liquor in the tubes, but which has not been condensed,
owing to the high temperature of the liquor, passes into the second vessel of the
first effect where the heat in the steam is finally made use of and where condensation :
takes place.
By working a double first effect in this way we are able to get multiple effect
not only out of the heat which we applied in the superheater but also the whole of
the latent heat which was contained in the steam before it came into the apparatus
and which otherwise would be wasted. The steam from the two vessels of the
first effect is used for heating the second effect and so on.
With regard to the circulation, to overcome the objectionable effect of having
the thickest liquor in the last effect, we reverse the direction of the flow of the
liquor by introducing the liquor to be treated into the last vessel and pumping or
otherwise discharging it from this vessel into the next and so on until it reaches
the first or double vessel heated by the hottest steam.
. f
The superheating apparatus which we advantageously employ is provided with a..

page_text: series of tubes through which the steam is caused to travel in the reverse direction
to that in which the furnace heat passes over them.
Dated this 16th day of July 1892.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in or connected with Evaporating or Concentrating
Apparatus.
We, FRANK WALTER SCOTT, of 44, Christian Street, Commercial Road, in the
County of London, Engineer, ERNEST GEORGE SCOTT, of 67, Lord Street,
Liverpool, in the County of Lancaster, Consulting Chemist, and FRANK WALTER
SCOTT Junior, of 44, Christian Street, aforesaid, 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 evaporating or concentrating apparatus.
Hitherto it has been impracticable to evaporate or concentrate in multiple-effect
apparatus liquids such as caustic soda, caustic potash, silicate of soda and zine
chloride which boil at high temperatures. Furthermore it has been found that the
internal circulation and consequent evaporation of the liquor in the last effect or
evaporating vessel, is. that containing the most concentrated liquid is not nearly as
good as in the first, riz. that containing the unconcentrated or least concentrated
liquid and this we ascribe to the fact that, although the boiling point of the liquor
is reduced in the last effect, by means of vacuum, so as to leave the same margin of
heat between the boiling point of the liquor therein and the surrounding steam as
in the first effect, this margin of heat in the last effect is not sufficient to raise the
liquor to its boiling point as this boiling point is higher than that of the liquor in
the first effect owing to the increased viscosity and density of the liquor.
The object of our invention is to overcome both of these difficulties; that is to
say, the difficulty of dealing with liquids boiling at high temperatures and the
difficulty of the circulation, and we overcome the first difficulty by superheating the
steam in order to raise it to the required temperature, and the second by causing
the steam to travel in the reverse direction to that in which the liquor travels
so that the hottest steam first acts upon the liquor having the highest boiling
point.
In carrying out our invention we advantageously use two vessels to constitute the
last effect, the said two vessels having one continuous heating system and one
vapour outlet to the preceding effect.
To enable our invention to be fully understood we will describe the same by
reference to the accompanying drawings, in which :-
Figure 1 is a sectional elevation of a multiple-effect evaporating apparatus
arranged in accordance with our invention and adapted to be heated by exhaust
steam and,
Figure 2 is a sectional elevation of a modified form of apparatus adapted to be
heated by live steam.
Similar letters of reference indicate corresponding parts in both figures.
u, b, c, d are the four evaporating vessels of the system, and a, b, c, d¹ are tanks
into which the contents of the evaporating vessels can be respectively discharged in
a well known manner.
e is a furnace for heating a steam superheater which advantageously consists of a
series of tubes through which the steam derived from an external source is caused
to travel in the reverse direction to that in which the furnace heat passes over
them, the steam flowing to the evaporating vessel through the pipe e¹. It is to be
understood, however, that any other suitable form of superheating apparatus may
be employed.

page_text: IS a ondensing apparatus in which the steam escaping from the vessel a is
condensed, and which contains a coil or pipes into which the liquid to be boiled in
the said vessel a is introduced through a pipe f¹ and from which it flows into the
vessel a through a pipe, whereby the said liquid is partially heated before passing
into the said vessel a.
b, c, d are pipes respectively connected with the vessels b, c, d and with the
tanks a', ', through which pipes the partially concentrated liquor discharged
from one vessel is drawn into the next succeeding vessel under the action of vacuum
or by means of a pump in a well known manner.
In the arrangement of our invention shown in Figure 1 we make use of a double
last effect that is to say, the heating systems of the vessels d, c are connected by a
pipe so that the steam after passing through the heating system of the vessel d,
where it is cooled nearly to the temperature of the boiling liquor in the vessel but
is not condensed (owing to the high temperature of such liquor) passes into the
second vessel c of the double effect where the heat in the steam is finally made use
of and where condensation takes place, the water of condensation being discharged
in the usual manner.
Both of the vessels d, e are connected with a pipe communicating with the
heating system of the next vessel so that the steam due to the evaporation in the
said vessels d, e is utilized for heating the liquor in the vessel b, whilst the steam
due to the evaporation in the vessel is conducted to the heating system of the
vessel a, that is to say each of the vessels preceding those heated by steam
from an external source is heated by the steam escaping from the adjacent
succeeding vessel.
By working a double effect in the manner just described we are able to utilize
not only the heat applied to the steam in the superheater but also the latent heat
contained in the steam before it entered the apparatus and which would otherwise
be wasted.
As hereinbefore stated the thinnest liquor first enters the vessel a and as it
becomes concentrated is transferred from vessel to vessel until it reaches the vessel d
where it is subjected to the greatest heat.
The arrangement hereinbefore described is especially adapted for using exhaust
steam but it is to be understood that it may also he used with live steam. When
live steam is employed, however, we advantageously make use of the arrangement
shown in Figure 2. In this arrangement, instead of passing the heating steam
through the heating systeins of two vessels in order to utilize the heat thereof, we
inject the steam into the liquid mass in the vessel d, in which case we dispense with
the ordinary system of heating tubes in the said vessel d and substitute therefor a
perforated coil or its equivalent directly connected with the steam inlet-pipe e'.
In this way the heating steam passes directly through the body of liquid in the
vessel but is not condensed owing to the high temperature of such liquid, the
steam as it rises through the boiling mass being conveyed in a well known manner
to the ordinary system of heating tubes of the effect e.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The method of operating multiple-effect evaporating apparatus consisting in
utilizing steam supplied from an external source for heating the evaporating vessel
or vessels containing the thickest or most concentrated liquid and having the
highest boiling point, the steam escaping from the evaporating liquid in such vessel
or vessels being utilized for heating the preceding vessel containing less concentrated
liquid and so on, substantially as described.
2. Multiple-effect evaporating apparatus the last vessel or vessels of which is or
are heated by superheated steam derived from an external source, the other or
preceding vessel or vessels being heated by the steam resulting from the evaporation
in the succeeding vessel or vessels, substantially as described.

page_text: 3. The combination with concentrating or evaporating apparatus of the kind
described of means for superheating the steam supplied to such apparatus,
substantially as set forth.
4. In multiple-effect, evaporating or concentrating apparatus the employment of
a double effect, that is to say, of two vessels the heating systems of which are
connected so that both may be heated from the same source, substantially as
described.
I
5. In evaporating or concentrating apparatus in which the steam supplied from
an external source is applied for heating that vessel containing the thickest or most
concentrated liquor, the arrangement, substantially as described by reference to
Figure 2, in which the steam is caused to pass directly through the liquid mass,
substantially as described.
6. In multiple-effect evaporating or concentrating apparatus in which the heating
steam is caused to travel in a reverse direction to the liquid being treated, a
condenser into which the steam escaping from the first effect is delivered and
through which the liquid to be treated is caused to flow, substantially as, and for
the purpose, described.
Dated the 17th day of April 1893.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.