Improvements in and relating to Apparatus for Distilling Sea-water and other Liquids.
Year: 1894

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to Apparatus for Distilling Sea-water
and other Liquids.
I, HENRI EDMOND FOUCHÉ, of 95, Boulevard Beaumarchais, Paris, in the
Republic of France, 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 :-
The present extended use of multitubular boilers on board ship has stimulated
the study of sea-water distillating apparatus or evaporators for the purpose of
avoiding the use of salt water for boiler-feeding purposes when the supply of fresh
water is exhausted.
The apparatus of this kind or class as employed hitherto has been designed
chiefly with a view to economy, without sufficiently considering weight and space
occupied.
The principle on which those most commonly used, (which are single-acting) is
based, is to employ steam for this purpose which has already been expanded in the
high-pressure cylinder or cylinders of the engine, before entering the intermediate
or following cylinder, the cost of production being thereby considerably reduced.
Various forms of double-acting apparatus have been also employed, but their
working is very imperfect and necessitates continual supervision, which it is
impossible to provide in a staff which is generally too small in number and already
over-worked.
Almost all of these evaporators work at high pressures, thus producing saline
deposits, and necessitating their parts being made very heavy and hence they are
of considerable weight. Further, they are all very cumbersome and it is well
known how disadvantageous this is on board ship, where space is valuable.
My main object is to construct an apparatus which is powerful, economical, light,
occupying a very small space, and which is, moreover, very easily operated and
understood.
Its economy and lightness are due to the method of using the steam in steps or
stages at a very low pressure, which steam can be taken, not only from the third
valve-chest of a triple-expansion engine, but even from the third cylinder itself,
just at the commencement of the stroke. The amount of energy remaining in the
steam removed for evaporative purposes is thus reduced to one-fifth only, in place
of one-third of its original value. To this saving in cost must be added the saving
due to the high efficiency of the apparatus, which is calculated to usefully employ
nearly the whole of the heat applied to it.
The power, and consequently the small space necessary are due to the use of
circulation, which has not hitherto been employed in the evaporation of sea-water,
and cannot be with the pressures hitherto employed.
Automatic operation displaces constant supervision, and the apparatus requires
only very simple manipulation. By reason of the arrangement of details, the
apparatus is very easily understood.
My said invention comprises a multiple-effect sea-water distilling apparatus,
based on the employment of circulation, combined with balancing pressure columns
arranged between the different chambers, and also with a heater for the water to
be distilled, hereinafter called the "feed-water heater."
My improved apparatus may, moreover, be used for the distillation of any other
liquid besides water.
I will now proceed to describe a triple-effect distiller, constructed according to
my invention.

page_text: In the accompanying drawings
Figure 1 is a side elevation, and
Figure 2 a plan of the whole apparatus, with certain parts removed or shown in
section to illustrate details of construction.
Figure 3 is a transverse section showing the heater.
Figure 4 is a view illustrating details of construction.
The apparatus comprises three similar heating chambers or evaporators, A, A', A",
containing heating tubes t, around which circulates the steam taken from the third
cylinder of the steam-engine, or from a boiler, if the ship be at rest.
B, B', B are steam cylinders or reservoirs; joining the steam reservoirs to the
evaporators are short cylindrical chambers C, C, C containing the circulating
tubes. These tubes are soldered at one end to conical brass rings or sleeves which
are forced by a light tap of a hammer, into the plates which separate the
chambers C, C, C from the steam cylinders or reservoirs B, B', B". The other
extremities of the circulating tubes, which penetrate some centimetres down into
the evaporating or heating tubes, t, are bell-mouthed, and are fluted or channelled
on the circumference of the widened part.
The water entering by the short cylindrical chambers runs between the two tubes
and through the channels, after which it circulates in a thin stream, about
a millimetre thick down the interior walls of the evaporating tubes t.
This
water accumulates in chambers D, D', D" below the bottom of the evaporating
chambers A, A¹, A".
E is an overflow vessel, arranged at a suitable level, through which the feed-
water runs from the heater over into the short cylindrical chamber C of the first
section of the apparatus.
F, F are water columns, the lower ends of which communicate with the
chambers D, D' below the first two evaporators, and their upper ends with the
steam cylinders or reservoirs B', B" of the second and third sections.
These water columns directly balance the differences of pressure between the
steam generated in the first evaporator and that generated in the second, aud
between the latter and the steam generated in the third evaporator.
The connection between each of the water-columns F, F and the corresponding
bottom chamber D, D' is made by means of siphons G, G₁ which maintain a constant
level of the water round the lower parts of the heating tubes.
At their upper ends, these balancing columns F, F' are bell-mouthed and are
formed with caps, H, H' provided with gauge-glasses, whereby the level of the
water therein may be ascertained.
The water passes from these caps into chambers I, I' which communicate
directly with the chambers C³, C".
J is a feed-water heater through which the feed-water is pumped before entering
the chamber E.
Whilst rising in the heater, the water successively passes over :-
A worm K through which a pump S. forces the saturated brine before its return
to the sea.
A worm L through which a pump S₁ forces the fresh water, gathered from the
second and third evaporators, into the water-tank.
A worm M in which the condensed water from the first evaporator circulates
before its return to the feed-water tank of the boiler.
Finally, through a set of tubes N which are heated externally by steam taken
from the second steam cylinder.
The first evaporator A is provided with a valve P to control the supply of steam
from the third cylinder of the engine, a reducing-valve Q which serves to reduce
the pressure of steam taken from a boiler, when the engines are not in motion, to
about 1 kilos. per square cm., and a safety-valve to prevent the pressure rising
above the proper value.
The pumps, S., Sa, S., the duties of which I have just described, are driven by
two coupled cylinders acting reciprocally.

page_text: Operation. The operation of the apparatus is as follows :—
1st. Circulation of the sea-water. The sea-water to be evaporated is drawn into
the heater, preferably after having previously passed through the condenser of the
main engines, by the pump S₁, the speed of which is so regulated as to maintain
the level of water in the vessel E at a practically constant height.
The temperature of the water in this vessel rises to very near the boiling-point.
The water then runs through the short cylindrical chamber, C between the inner
and outer tubes and through the channels into the evaporating tubes t in order to
be evaporated whilst passing down inside the heated walls thereof.
The water which is not vaporized accumulates in the bottom chamber D, until it
reaches the level determined by the siphon G. It then rises in the balancing
column F, and finds its level in the cap H. The water then escapes by an
intermediate vessel I into the chamber C¹ to circulate in the tubes of the second
chamber or evaporator A' and so on.
Finally, it is drawn from the chamber below the third evaporator A" by the
pump S, and pumped back into the sea through the coil K of the feed-water
heater.
2nd. Circulation of steam. The steam for heating enters the first evaporator A
by the check-valve P, or by the reducing valve Q and is there condensed. The
steam produced thereby is quietly generated in the interior of the evaporating
tubes and rises into the steam cylinder or reservoir B through the interior of the
circulating tubes. From this cylinder it passes to be condensed around the tubes
of the second evaporator.
In the same manner, the steam generated in the second evaporator passes up into
the second steam-cylinder B' into the third evaporator where it is condensed.
Finally, the steam generated in the third evaporator is drawn into the condenser
of the main engines by the vacuum.
3rd. Circulation of fresh water. The water produced by the condensation of the
heating steam from the main engines or elsewhere in the first evaporator, is
returned to the feed-tanks of the boilers through the coil M in the feed-water
heater.
The water produced by the condensation of the steam in the second evaporator A¹
passes directly into the third evaporator whence it is drawn with the condensed
water in the latter by the pump S₁ which pumps it into the fresh water tanks
through the coil L in the feed-water heater.
The management of the apparatus is thus very simple. It is only necessary to
regulate the speed of the feed-pump, so as to maintain the level in the chamber E
connecting the feed-water heater and the first short cylindrical chamber C, after
which everything operates automatically. This can be easily checked by looking
at the gauge-glasses on the caps H and H₁ of the balancing columns and the
water-level indicator placed on the chamber D", into which the evaporating tubes
discharge their water below the third heating chamber or evaporator A".
The pumps Sa and S, work at the same rate as the pump S, and are calculated
to throw the same amount of water as that pump. The motor driving the pumps is
preferably supplied with steam from the same source as that which is used to
produce evaporation in the first evaporator. In this manner the apparatus starts
and stops itself with the main engines.
The advantages of circulation are well known, riz. :-Absence of reversal in the
withdrawal of the steam, equality of temperature throughout the condenser tubes,
utilization of the whole of the heating surface, and of the whole of the available
difference of temperatures, possible transmission of the whole of the heat to the
same body of liquid, and a considerable increase in the power and efficiency.
By reason of their arrangement, their weight and the space they occupy, none of
the forms of evaporating apparatus, in which circulation is employed as constructed
hitherto, can conform to the exigences of use on board ship. Further, the use of
high-pressure steam seems incompatible with the application of circulation. The

page_text: application of this principle which I am now making is thus novel and original and
constitutes one of the characteristic features of my distilling apparatus.
It is necessary to more fully explain the function of the said balancing
columns G F H and G' F' H'.
Let us suppose that communication is established between the chamber D and
the chamber C. There would then be nothing to regulate the level in the
chamber D below the first evaporator A. The water could then rise in the tubes t
and produce violent ebullition in the lower parts of the same, thus causing the
suspension of water in the steam produced.
In my apparatus, on the contrary, the level in the evaporating tubes at the
bottom of the first evaporator or rather in the chamber D into which they
discharge, is caused to remain at a fixed point by means of the siphon G. But the
variations make themselves felt on the level in the cap of the said column H. If
the latter tends to rise, the stream of water running through the channels below
the chamber C¹ increases and the speed of circulation increases in the tubes of the
second evaporator A'; if it tends to fall, this speed decreases.
It is understood that by means of the said balancing-columns G F H, G'F' H',
a regulating action is produced, which is not subject to any derangement, as is the
case when floats, pumps, or other more complicated accessories are employed.
By reason of this arrangement, the whole of the heating surface of the apparatus
works smoothly, equably, and with a high efficiency owing to the circulation; the
suspension of water in the steam is entirely obviated, a point which is very
essential when the water is to be used for making up the waste for steam boilers.
Thus, by the employment of the said columns, a balance of pressures is
automatically maintained from one end of the apparatus to the other. Another
effect of this arrangement is the equal distribution of temperature between one
chamber and another without wasting any fraction of the total difference of
temperatures available; this value of the total difference of temperatures is
determined by the difference of pressures between the steam used for heating and
the vacuum of the condenser.
I have said above, that, by reason of this limit, the parts of the apparatus can
be made very light and thus a minimum weight secured.
This advantage, moreover is not incompatible with the conditions of economy
which must equally be considered. The economy of my apparatus is due, not only
to the use of steam at a very low pressure, as explained above, but also by the
almost complete utilization of the heat contained therein. A very small part, in
fact, reaches the condenser, with the steam from the last evaporator.
This result must be attributed to the novel arrangement of the feed-water
heater, which raises the temperature of the feed-water very nearly to boiling point
before entering the first evaporator, in such a manner that all the heat contained
in the steam is immediately utilized for evaporation.
In rising around the three coils of the feed-water-heater, the liquid takes up the
heat which would otherwise escape from the apparatus with the saturated water and
the condensed water.
Its rise in temperature is consequently obtained by the condensation of a certain
quantity of steam Q, taken from the steam cylinder or reservoir B' of the second
evaporator. This rise induces an increase of evaporation in the first evaporator A.
Let q be the additional amount of liquid thus evaporated. The latter evaporates a
quantity q' in the second evaporator A', which, in its turn evaporates a quantity q"
in the third evaporator A". But the effect of the steam Q in the third evaporator
has not yet been considered, and consists in producing a diminution Qin the
evaporation therein.
It is clear that the arrangement employed will be advantageous if the sum of the
quantities q+y₁+q" be greater than Q
Further, calculation shows not only that this inequality does exist, but that the
first term may reach a value almost three times that of the second.

page_text: As the water condensed in the second chamber is collected with the water
condensed in the chamber A", a larger amount is produced in the whole apparatus,
without increasing the amount of steam required to heat the same, thus the
efficiency is considerably increased.
This method can be applied to all multiple-effect apparatus, whatever be the
number n of the evaporating chambers. It thus consists in completing the heating
of the feed-water, by a portion of the steam produced in the 7th chamber, and
before it has completed its work of evaporation in the n-p remaining chambers.
The efficiency, in a triple-acting apparatus constructed according to my invention,
reaches 2 kilos. of soft water produced per kilogram of steam used. If it be
considered that the cost price of this kilogram of steam is reduced four-fifths, by
reason of the work which it has already done in the engines, it is calculated that a
ton of soft water may be produced with a consumption of only 23 kilos. of coal.
An apparatus capable of producing this ton of soft water would not weigh more
than 900 kilos., and would occupy a space of 1½ x ½ metres in plan with a height of
1 metres.
I will now consider the arrangement of the details relating to the maintenance of
the apparatus. I have described above how the circulating tubes are fixed in the
plate which supports them. The brass ring carries, across one diameter, two
grooves in which rests a key, whereby the removal of the conical portion in the
plate may be readily effected, and the tube lifted out.
The cylinders are provided with an easily removable cover and attachments to
facilitate this operation.
About once in every two months, it is advisable to clean the apparatus. For
this purpose, the circulating tubes are removed as just described, and the three
chambers are filled with slightly acidulated water, which is caused to boil by means.
of steam introduced by suitable tubes. Any deposits which may be present in the
interior of the apparatus are thus dissolved.
These deposits are always very small, as, by reason of the circulation, the
evaporation is carried on very quietly, and the heating surfaces are always kept
wet by the liquid.
If, for any reason, the apparatus is used for a long time without cleansing, the
interior portions of the evaporating tubes may be brushed, by removing the small
channelled circulating tubes and the bottom of the steam cylinder or reservoir. In
which case a simple joint has to be broken and re-made.
Apparatus independent of the engines. If desired, a different arrangement of
apparatus may be adopted, so as to render it entirely independent of the main
engines. An arrangement of this kind can be used on board large sailing-vessels,
(where there is always a boiler for the winch), for the purpose of replenishing the
store of fresh water. The latter can be reduced, and the small quantity of coal
which is required, will leave a considerable space free for other purposes.
For this purpose it is only necessary to replace the three coils in the heater by a
set of parallel tubes in which the steam generated in the last chamber is condensed.
The pump Sa draws all the water produced in the apparatus from the lower part of
the casing holding these parallel tubes. Its dimensions may be increased if it is
desired to produce a vacuum.
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 :-
First. The above described improved apparatus for evaporating sea-water and
other liquids, characterized by :-The multiple effect, the employment of steam at
very low pressure, the use of circulation, and the combination of any or all of the
special arrangements claimed in the succeeding claiming clauses, for the purpose of
obtaining economy, lightness, smallness of space occupied, automatic operation, and
great facility of control and maintenance.
Second. The arrangement of each section of the evaporator, comprising a steam

page_text: cylinder, an evaporating chamber containing a series of heating tubes, provided
with removable circulation-tubes, and a lower chamber, or base.
Third. The combination, with the first section of the evaporator, of the vessel E
for regulating the feed.
Fourth. The combination, with each of the sections of the evaporator, with the
exception of the last, of a liquid column in three parts, siphons, a central part,
and a cap, communicating at the bottom with the preceding chamber, and at the
top with the cylinder of the next succeeding chamber, and operating to keep the
level of water in the bottom of the chambers constant and to automatically and
directly compensate for the differences of pressure between one chamber and the
next, for the purposes specified.
Fifth. In combination with the above described liquid columns, the arrangement
of the intermediate feed-chamber for obtaining a variable speed of circulation of
the water according to the level in the caps H.
Sixth. The arrangement of the gauge-glasses on the caps H and of the water-
level indicator at the bottom of the last chamber, to facilitate the control of the
working of the apparatus.
Seventh. In combination with the sections of an evaporator of any system, with
or without one or more coils as above described and with or without a series of tubes
serving to condense the steam generated in the last chamber, the arrangement of
the heater characterized by the use of a series of tubes or of a coil in which a
portion of the steam generated in the pth chamber is condensed and removed before
it reaches the (p + 1) th chamber, in such a manner as to complete the reheating of
the feed-water and to convey it, without giving up heat to the steam, at a tempera-
ture approximating as nearly as possible to the temperature of evaporation in the
first chamber.
Eighth. In combination with the sections of an evaporator of any kind and in
combination or not with the heater above described, the arrangement of three
pumps, one serving as a feed-pump, another for removing the softened water, and a
third for removing the saturated water operated together by a suitable motor, and
of such capacities that their deliveries correspond, the first only being controlled
according to the level of water in the vessel E.
Ninth. The arrangements of detail relative to the maintenance such as are above
described.
All in combination or separately for the purpose specified.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.