Improvements in Purifying Oil Extracted by Solvent from Linseed or similar Substance
Year: 1895

page_text: Date of Application, 3rd Dec., 1895-Accepted, 4th Jan., 1896
Improvements in Purifying Oil Extracted by Solvent from Linseed
or similar Substance.
Communicated to me from abroad by THE CLEVELAND LINSEED OIL COMPANY,
of Cleveland, in the State of Ohio, one of the United States of America,
Manufacturers.
I, WILLIAM THOMAS WHITEMAN, of No. 7, Staple Inn, in the County of
Middlesex, Patent Agent, 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 purification of oils which have been extracted by
a solvent, such as naphtha, from ground linseed or similar substances, and which
contain matters coagulable by heat or heat and moisture that have been extracted
with the fatty constituents of the seed. In the purification of such oils, it has been
found essential to pass steam through the solvent-containing oil in order effectively
to get rid of the solvent, since dry heat alone does not accomplish that object.
As heretofore practised, the steaming has brought about not only the removal
of the naphtha, but also the coagulation of some of the albuminous or mucilaginous
constituents of the oil and the formation of an intimate admixture or emulsion of
such coagulated constituents, oil and condensed moisture. It has consequently
heen necessary to submit the steamed and emulsified oil to a further treatment to
clarify it and rid it of the suspended matters.
It will be perceived, therefore, that this old process involves a further treat-
ment after the removal of the solvent, and also changes the composition of the oil
by the removal of the mucilaginous or albuminous constituents. The further
treatment is, of course, an item of expense; but the change of composition is, as has
been discovered, a much more serious objection, since to it must be attributed (as
is believed) the well-known unfitness of solvent-extracted oil, as heretofore made,
for certain industrial uses such as painting, for example.
It has now been discovered that by having the oil at a suitably low temperature
and introducing steam of a suitably reduced tension and temperature, the
removal of the naphtha may be effected without coagulating the mucilaginous or
albuminous constituents which give. body to the oil and which are extracted with
the fatty matters from the ground linseed. The temperature of the oil and of the
steam must be sufficiently below 212° F. to be non-coagulative of the mucilaginous
or albuminous constituents and is preferably at about or below 140° F., for there
is no practical difficulty in securing such reduced temperature, and obtaining
excellent results thereby. Temperatures above 140° F. may be used; (and still
be within the invention ;) but there is believed to be no substantial advantage in
employing such higher temperatures; and it is evident also that the higher the
temperatures, the greater the risk of causing injurious coagulation.
In accordance with the invention, therefore, the solvent-containing mucilaginous.
or albuminous oil is kept at a non-coagulative temperature, (preferably at
about or below 140° F.,) and there is passed through such oil low tension steam of:
non-coagulative temperature (preferably at about 140° F. during the principal.
steaming operation,) thereby removing the naphtha or solvent while leaving a
substantial body of coagulable matter in the oil.

page_text: Low tension steam of proper temperature may be secured by suitably reducing
the vapor pressure in the separator (that is the vessel which holds the oil to be
purified) and delivering steam from an ordinary boiler below the surface of the oil
through a pipe of a bore to deliver sufficient steam rapidly to drive off the naphtha
without unduly raising the vapor pressure. In passing through the pipe the steam
is relieved more and more of the pressure which confined it in the boiler, so that at
its entrance into the oil, its tension corresponds with the back pressure in the
separator-due both to the resistance of the overlying body of oil and to the vapor
pressure above it. Its temperature will then also be low in correspondence with
the reduced tension.
Practically it is found best to carry on the solvent-removing operation in two
stages; in the first of which the temperature of the oil is kept lower and a less
volume of steam introduced than in the second or later stage when the solvent or
naphtha has been largely removed. This mode constitutes a special improvement;
although all the claims are not confined thereto, but only the third of those
hereinafter written.
The accompanying drawings illustrate what is considered the best form of
apparatus for use in carrying the invention into effect.
Fig. I is a general view in elevation of such apparatus ;
Fig. 1 is a view in longitudinal section of the left hand portion of the separator,
or vessel to hold the oil, and
Fig. III is an end view of such separator with the head removed and the upper
part of the vapor-dome broken away.
The separator "A" is provided with a fitting 2 to receive the filling pipe (not
shown) by which the oil is introduced into the separator. It also has a dome 3
with which the vapor outlet 4 is connected, and a draw off 5 (provided with a
suitable cock or valve, not shown) for removing the purified oil. At 6 are bull's
eyes or glass covered holes in the walls of the separator through which the interior
can be inspected. At the ends are manholes 7. The coils and 9 are dry heating
coils; that is to say, they are imperforate coils through which steam is passed for
raising the temperature of the oil by dry heat. The inlets 8' and 9' are shown at
one end, and the outlets (8" only is shown) at the opposite end. The pipe 10 is
perforated along the bottom, and serves to admit steam into the oil through such
perforations.
The vapor outlet pipe 4 leads to a condenser "B," which in turn is connected
by the pipe 11 with an aspirating pump "C," (or exhauster of any suitable
description,) the discharge of said pump being connected by the pipe 12 with a
second condenser "D."
The oil extracted, say at or slightly above atmospheric temperature from
linseed by naphtha, by means of one of the well-known percolators and containing
solvent and coagulable matter, is introduced into the separator "A" so as to fill it
say two-thirds full. The oil may come from the percolator containing all the
solvent or with some of the solvent already evaporated off; or generally it may
have been subjected to any treatment not inconsistent with the purposes of the
present invention. Preferably it is introduced into the separator just as it comes
from storage tanks in which it is pumped from the percolator.
When the separator has been charged the filling pipe or opening is closed, and
the pump "C" started. Steam is introduced into the dry coils 8 and 9; and steam
is also injected into the oil through the pipe 10. Proper conditions at this stage
are a temperature of about 125° F., a pressure of about 17 inches by the vacuum
gauge (or in other words about 17 inches below the ordinary barometrical pressure)
and the injection of enough steam to prevent foaming. Practically suitable condi
tions can be secured by keeping the dry coils 8 and 9 (having suitably proportioned
heating surface) full of steam from a boiler at say 60 lbs. pressure per square inch
(the boiler connection being left open and the water from condensation of the steam
in the coils being drawn off through a cock sufficiently closed to let off the water
while preventing any considerable escape of steam) and maintaining a suitably rapid
5

page_text: removal of vapor by means of the condenser "B" and pump "C." Assuming a
conical-ended cylindrical separator "A," eight feet in diameter and thirty-nine feet
extreme length, provided with coils 8 and 9, each composed of five hundred and
twenty-seven feet of two-inch pipe; the condenser "B" may contain 1,500 copper
tubes, each three-fourths of an inch in outside diameter and ten feet in length, and
be supplied with enough condensing water at ordinary temperature (say 67° F.) to
be not above 110° F. at its outlet, and the pump "C" may be of the reciprocating
type of 36 inches diameter of cylinder and 36 inches stroke, and make about
45 revolutions (or complete reciprocations) a minute. By observation through a
bull's eye 6, the attendant can regulate the supply of injected steam through the
pipe 10 so as to correct any tendency of the oil in the separator to foam. The
pipe 10 may be 3 inches in diameter. The perforations in this pipe are preferably
small and close together along the bottom line of the pipe, say of inch diameter
of aperture and an inch and a third apart.
The naphtha vapor and steam from the separator together pass through pipe 4.
to the condenser "B," wherein the steam and most of the naphtha are condensed..
The condensed liquids and uncondensed vapor pass through the pump "C" and
condenser "D" wherein a higher pressure is retained and wherein the remaining
solvent vapor is condensed. The liquids need not enter the pump "C" and
condenser D," as they could be trapped off or separated by well-known means.
From the condenser "D" the water and liquified solvent would flow into a suitable
receiver.
As the evaporation proceeds it is not necessary to alter the power of the con- .
denser "B," nor the speed of the pump "C," nor the volume of steam injected
through the pipe 10, although as to the latter it is to be observed that the tendency
to foam diminishes and the volume of injected steam could therefore be reduced if
thought desirable. Under these conditions the vacuum gauge gradually rises (in
other words the pressure in the separator becomes less); the temperature also
gradually rises. When the solvent has nearly disappeared, which will be in about,
three quarters of an hour, and which will be shown by the height of the vacuum
gauge, (say when such gauge reaches about 25 inches, the thermometer standing
about 140° F.,) the steam is shut off from the dry coils and is injected freely
through the pipe 10, so as to maintain the oil in thorough ebullition until the water
of condensation from the condenser "B" shows no more naphtha, which should be
the case in about five minutes.
On passing through the pipe 10 the tension of the steam and its temperature
also would be reduced so that on entering the oil its tension would be somewhat
above 4 inches of mercury, (for an indication of 25 inches by the vacuum gauge
represents a vapor pressure of 4 inches of mercury when the outside barometer
stands at 30 inches, and the entering steam has to overcome the resistance of the
oil in addition to such vapor pressure,) and its temperature would be corre-
spondingly above 1314° F., (which is the temperature of saturated steam under the
pressure of 4 inches of mercury.) The temperature of the entering steam would
therefore be about 140° F. The degree of vacuum in the separator "A" thus
allows such an expansion of the injected steam as that its temperature is lowered
below the coagulating point of the mucilaginous or albuminous constituents of the
oil. Consequently these constituents are not coagulated and separated from the
fatty matter as they are believed to have been in all previous processes in which
solvent-extracted linseed oil, or an oil extracted by solvent and containing such
albuminous or mucilaginous matter as occurs in linseed oil, has been steamed to
remove the solvent.
When a sample withdrawn shows no trace of naphtha, the steam is shut off,
the pump is stopped, and the purified oil drawn off. The oil should then be clear.
It contains a substantial body of albuminous and mucilaginous matter, and is well
adapted to painting and other uses for which an oil with "body" is desired. Should,
however, the oil appear cloudy or contain water, it can be heated by the dry coils 8
and 9 alone (the pump "C" being operated) in order to clarify it, or other means

page_text: It is
(such as an air blast through say the pipe 10) can be used for that purpose.
not necessary, however, to do this if the process has been carefully carried out.
While the use of air is no part of the present invention, it may be observed
that it can be injected into and allowed to pass through the oil, before, or simul-
taneously with, or after the injection of steam; but since it has a chemical action,
its use may be injurious if carried too far.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. The process of purifying linseed or similar oil, containing solvent such as
naphtha together with the coagulable mucilaginous or albuminous matter extracted
with the fatty matter, by evaporating the naphtha at a temperature suitably
below 212° F. to be non-coagulative of said mucilaginous or albuminous matter
(preferably about or below 140° F.) with the aid of low tension_steam passed
through said oil and having a temperature suitably below 212° F. to be non-
coagulative of its said mucilaginous or albuminous matter; substantially as
described.
2. The process of purifying linseed or similar oil, containing solvent such as
naphtha together with the coagulable mucilaginous or albuminous matter extracted
with the fatty matter, by evaporating the naphtha at a temperature suitably
below 212° F. to be non-coagulative of said mucilaginous or albuminous matter
(preferably about or below 140° F.) with the aid of dry heat and of low tension
steam passed through said oil and having a temperature suitably below 212° F. to
be non-coagulative of its said mucilaginous or albuminous matter; substantially as
described.
3. The process of purifying linseed or similar oil, containing solvent such as
naphtha together with the coagulable mucilaginous or albuminous matter extracted
with the fatty matter, by evaporating the naphtha with the aid of dry heat and
low tension steam in two stages, in both of which the oil is kept at a temperature
suitably below 212° F. to be non-coagulative of said mucilaginous or albuminous
matter, (preferably about or below 14° F.,) and in both of which low tension non-
coagulative steam is passed through said oil, the temperature of the oil being lower
and a less volume of steam being passed through the oil in the first than in the
second or later stage, wherein the temperatures of the oil and of the injected steam
are preferably about 140° F.; substantially as described.
Dated this Nineteenth day of November 1895.