Method of and 'Apparatus for Purifying Sea Water for use in Steam Generators.
Year: 1889

page_text: Date of Application, 28th Mar., 1889
Complete Specification Left, 30th Dec., 1889-Accepted, 22nd Mar.. 1890
LROY IDIUNAIS DI MUITIVATION,
Method of and 'Apparatus for Purifying Sea Water for use in Steam
Generators.
I, VIVIAN BYAM LEWES, of 19 Park Row, Greenwich, in the County of Kent,
Professor of Chemistry, do hereby, declare the nature of this invention to be as
follows:
This invention has for object to remove; the impurities such as certain salts of
calcium and magnesium usually present in sea water and thereby to render such water
fit for use in steam generators without causing incrustation..
According to this invention the water is mixed with a suitable salt or compound
such as carbonate of soda and heated under pressure in a suitable vessel, after which it
is passed through a suitable filter and into a feed tank, hot well, or other receptacle
from which it is supplied to the steam generator. For heating the water high pressure
or super-heated steam may advantageously be passed into it by a suitably arranged
perforated pipe.
A convenient arrangement of apparatus for carrying my invention into practice
comprises a vessel provided with inlets for the sea water and for the carbonate for
purifying the same, and with an outlet placed above the bottom of the vessel and in
communication with a filter that may be constructed with one or more frames or
perforated plates upon which is placed suitable filtering material such as asbestos cloth.
At the bottom of the vessel is an outlet for blowing off the impurities precipitated
from the water. The construction of filter is such that when not being used for
"filtering the heated sea water may be passed through it in the reverse direction for
cleaning the filtering material. A pipe arranged within the vessel serves to admit
steam from a suitable source for heating the sea water. Suitably arranged cocks or
valves are used for controlling the inlet and outlet of water and the discharge of the
COMPLETE SPECIFICATION...
Method of and Apparatus for Purifying Sea. Water for use in Steam
Generators.
VIVIAN BYAM LEWES, of 19 Park Row, Greenwich, in 'the County of Kent,
Professor of Chemistry, 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 has reference to a method of removing the impurities, such as certain
salts of calcium and magnesiumn usually present in sea water and in some fresh waters
in order thereby to render such water fit for use in steam-generators without causing
incrustation..
For this purpose the sea water or other impure water (hereinafter referred to
generally as sea water) is mixed with, some salt or compound that will precipitate the
calcium and magnesium salts contained in the water. A suitable substance, is
carbonate of soda; carbonate of potash would produce the desired effect but carbonate
of soda.is much cheaper. The mixture is heated under, pressure in a suitable vessel
separate from the steam generator in which the water is afterwards to be used; from
ΓΥ

page_text: this vessel the water is passed through a suitable filter and into a feed tank, hot well,
or other receptacle from which it is supplied to the steam generator. By heating
under pressure the process is expedited but where it is not practicable or convenient
to heat under pressure, atmospheric pressure may prevail and the result can be attained
by prolonging the process. The water may be heated in different ways; it may be by
causing high pressure or superheated stem to circulate through a coil with which the
water to be heated is in contact; or the steam may be passed into the water by³ä
suitably arranged perforated pipe.
A convenient arrangement of apparatus for carrying my invention into practice is
shewn in the accompanying drawings in which;
Figs. 1 and 2 are respectively a vertical section and a plan of a precipitator or
apparatus in which sea water is treated according to this invention.
Figs. 3, 4 and 5 are respectively a vertical longitudinal section, a transverse section,
and a half plan with part of the cover removed, of a filter through which the sea water
is passed after being treated in the precipitator.
Referring to Figs. 1 and 2, 1 is a cylindrical vessel of any suitable capacity. It is
provided at its upper part with an inlet pipe 3 and cock 4 for admission of sea water,
and at bottom with an outlet pipe 5 and cock 6 for the discharge of impurities
separated from the sea water. 7 is an outlet pipe for the treated water. This outlet
is controlled by a cock 8 and has its inner end located sufficiently above the bottom of
the vessel 1 to allow of the deposit settling in the lower part of the vessel. 9 is an
opening with steam tight cover through which carbonate of soda can be introduced.
10 is a coil with inlet cock 11 and outlet cock 12. Through this coil high pressure or
superheated steam is passed for heating the sea water contained in the vessel 1 to a
sufficient temperature and pressure to completely separate in an insoluble form, the
calcium and magnesium salts present therein. Where it is not practicable or
convenient to heat under pressure greater than that of the atmosphere this pressure
may prevail in the vessel 1 as hereinbefore mentioned but the process must be pro-
longed to completely precipitate all the salts present. The dotted lines at 12 in Fig.
are to indicate the level at which the cock 12 is placed, but it will be understood
from Fig. 2 that said cock is fixed to that half of the vessel which is not shewn in
Fig. 1.
Instead of using a steam coil as shewn other arrangements might be employed to
sufficiently heat the sea water in the vessel 1;. for example, a perforated pipe arranged
vertically within the vessel 1 and extending downward to about the level of the inner
end of pipe 7, might be used. In this case the water instead of being heated merely
by contact with the pipe will be heated by the direct introduction of steam into the
water. 13 is a safety valve; 14 a gauge glass; 14ª a pressure gauge; and 15 a
manhole with suitable cover all of which may be of ordinary construction. As already
stated, from the precipitator the water is conducted to and caused to pass through a
filter.
The filter shewn in Figs. 3, 4 and 5 comprises a vessel 16 with a removable
cover 16 and with a series of vertical partitions 17 each formed with an opening 17°
therethrough. 18, 18 are filter frames each of which may consist of two sheets of
perforated metal such as iron, between which is placed suitable filtering material such
as asbestos cloth. These filter frames 18, are secured, one over each opening 17° as
shewn by bolts 19. 20 is an inlet opening whereby communication is established by
any suitable connection between the outlet pipe 7 of the precipitator and the interior
of the filter when the apparatus is in use. 21 is an outlet opening 'through which the
purified sea water is passed to a hot water well, or feed water tank. The method of
purifying sea water with the apparatus described is as follows:-
Assuming the vessel 1'to have a capacity equal to four tons of sea water, then sea
water to be purified is run into it through the inlet pipe 3 until a mark on the gauge
glass shews that three tons of water have been admitted. The cover of the opening 9
is then removed, and about forty pounds of soda crystals (carbonate of soda) or twenty
pounds of soda ash are added for each ton of water. This quantity of soda will-be

page_text: sufficient to convert all the calcic sulphate present in the water into calcic carbonate,.
and all the magnesic sulphate and chloride into magnesic carbonate: an equivalent
quantity of sodic sulphate and sodic chloride, is formed and remains in solution. The
magnesic carbonate is thrown down in the hydrated form in which condition it is very
bulky. All the openings to the vessel 1 are then closed, and steam under pressure
is passed through the coil 10 until the pressure gauge indicates that there is in the
vessel 1 a pressure of about five or six pounds per square inch, that is to say, until
the temperature of the sea water is about 230° F. or 110° C. Under these conditions,
the precipitate becomes very dense, and rapidly settles in a small bulk in the lower
part of the vessel as a loose powdery precipitate. The water having reached the
temperature mentioned, the flow of steam through the coil 10 is stopped, and the
contents of the vessel are allowed to stand for about half an hour to allow the pre-
cipitate to deposit. If about half a pint of paraffin oil, free from paraffin scale, be
introduced once a week into the vessel 1 while it is empty, the precipitate will have
no tendency to adhere to the inner surface of the vessel. The cover of opening 9 is
then removed or the interior of the vessel 1 otherwise placed in communication with
the external atmosphere and about two and one half tons of the supernatant water
are allowed to flow through the outlet pipe 7 into and through the filter wherein the
last traces of suspended matter are removed from the water; or if the flow is not
sufficiently rapid, steam pressure can be applied to the contents of the precipitator.
The water flows through the opening 21 to a hot water well or feed water tank, and
being at a high temperature can with advantage be pumped direct into a steam
generator. If the purified water be conducted to a condenser, then the interior of
the vessel need not be placed in communication with the atmosphere before drawing
off the supernatant water.
The remaining water and the insoluble impurities are then drawn off by the outlet
pipe 5 and cock 6 and thrown overboard or otherwise disposed of. After closing the
cocks 6 and 8 the hereinabove described process may be repeated for treating a fresh
quantity of sea water.
By removing the cover of the filter, the filtering frames may be taken out and
cleaned, and separated impurities in the several compartments removed.
Sea water treated in the manner hereinbefore described may with advantage be
mixed with the condenser water of marine steam engines, in lieu of the distilled
water usually employed, thus obviating the injurious action which distilled water has
on the plates of steam generators in which it is used; whilst dispensing with the
expensive distilling apparatus ordinarily used for supplying the necessary quantity of
water to the condenser water to replace that unavoidably lost in the working of a
marine steam engine.
I am aware that the use of carbonate of soda in marine boilers has been advocated
from time to time but the serious drawback to its use in the marine boiler itself is
that it throws down the inagnesium salts as carbonate, and so forms a bulky precipitate
which, unless got rid of within a few weeks of its deposition, bakes to a hard mass
and constitutes a bad form of deposit. By treating sea water in the manner herein
described, the impurities are readily removed without forming an incrustation in the
vessel in which the water is treated, and as the said vessel is only required to with-
stand a slight pressure, it can be made of comparatively thin metal with every part
easily accessible.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is:-
The herein described method or process of treating sea water for use in steam
generators, by mixing with the water a salt or compound such as carbonate of soda,
capable of precipitating the calcium and magnesium salts contained in the water,
heating the mixture to boiling in a closed heating vessel separate from the steam
generator in which the purified water is to be used, allowing the insoluble precipitated