Note: Descriptions are shown in the official language in which they were submitted.
l l 7298~
BACKGROUND OF THE INVENTION
Field: This invention relates to processes for recovering
bituminous organic material from tar sands or oil sands, and, more
particularly, to process utilizing and organic solvent to dissolve the
bituminous material from the sands.
State of the Art: Large deposits of oil sands or tar sands are
found in various parts of the world, in particular in Canada, the
United States of America, Venezuela, Russia, and Malagasy. Various
attempts have been made in the past to recover the bituminous
organic material from tar sands and oil sands. Retorting and other
thermal processes are uneconomical due to the large quantity of heat
consumed without any effective and efflcient recovery thereof.
Processes utilizing water and a hydrocarbon diluent, such as
kerosene, have been disclosed. For example, see U.S. Patent Nos.
2,453,060; 2,825,677; and 3,509,037. Unfortunately, such processes
utilize large amounts of heat and water. In addition, these processes
are expensive and can cause serious environmental problems due to
polluted water and sand which are produced in copious amounts.
Solvent extraction of bituminous organic material from tar sands
or oil sands has also been proposed. For example, see U.S. Patent
Nos. 1,514,113; 2,453,633; 2,596,793; 3,050,289; 3,079,326; 3,131,141;
3,392,105; 3,475,318; 3,503,868; 3,509,037; 4,029,568; 4,046,668;
4,046,669; 4,057,485; and 4,110,194. Unfortunately, low yields, high
energy consumption, loss of solvents, and environmental problems
including dirty spent sands containing both solvent and bituminous
material has hindered the development the solvent extraction
processes .
Objectives: A principal objective of the present invention is to
provide an efficient solvent extraction process for high yields of
bituminous organic material from tar sands or oil sands with a low
solvent loss. Another objective of the invention is to develop a
~172984
process requiring a minimum of energy consumption due to the
relatively mild conditions used in recovering the organic solvent
from the bituminous organic material and the effective recovery and
reuse of heat values. A further objective of the invention is to
provide a process which uses only very small amounts of water. An
even further objective of the invention is to provide a process which
is environmentally clean , i . e ., can be operated without polluting the
ambient air and water, and produces a clean sand which can be
further processed to recover mineral values therefrom or disposed of
without causing a pollution problem. A still further object of the
invention is to provide a process for efficiently recovering the
bituminous organic material in a form which can be used for many
purposes without further processing or treatment.
SUMMARY OF THE INVENTION
The above objectives are achieved in accordance with the
present invention by providing a novel method of recovering
bituminous organic material from tar sands or oil sands. The sands
containing the bituminous organic material are mixed with a
halogenated organic solvent which is substantially immiscible with
water and has a density greater than that of water at the same
temperature. The organic solvent is also capable of dissolving the
bituminous organic material contained in the sands. A slurry is
thereby produced comprising solid sand particles suspended in a
solution of bituminous organic material dissolved in the halogenated
organic solvent.
The resulting slurry is continuously transferred to a conveyor
system which is at least partially submerged in water with the
slurry being fed onto the portion of the conveyor which is submerged
in the water. The sands in the slurry are preferentially wetted by
water, and the organic solvent solution, which is essentially
immiscible in the water phase, separates from the particulate sands
1 172984
and forms a separate phase beneath the water. The movement of the
particulate sands on the conveyor enhances the separation of the
organic solution from the sand particles so that the sand particles
become essentially completely wetted by the water phase. The
particulate sands ultimately move upwardly on the conveyor through
the surface of the water and are transferred to storage. The sands,
which emerge from the water on the conveyor, are wetted essentially
only by water and contain essentially no organic solvent. Such
sands are readily available for further processing to recover other
mineral values therefrom, or the sand can be used as a conventional
clean sand aggregate. If further utilization of the sand is not
economically feasible, the clean sands can be disposed of without
creating a detrimental pollution problem.
The organic phase comprising the solution of bituminous organic
material dissolved in the halogenated organic solvent is recovered
from beneath the water phase. Preferably the organic solvents used
in the present process have relatively low boiling points, low
specific heats and low heats of vaporization. Even though such
solvents are quite volatile (even at atmospheric conditions which are
used in the mixing and sand separation steps of this process) losses
of the organic solvent has been found to be minimal due to the water
cap which is maintained over the solvent solution during the sand
separation step. Further, the mixing of the tar sands or oil sands
with the organic solvent is advantageously accomplished in a mixing
vessel in which a water cap is maintained on the top of the organic
phase in the mixing vessel.
Preferably, the solution of bituminous material dissolved in the
organic solvent which is recovered from beneath the water phase is
subjected to flash evaporation to separate the bituminous material
from the organic solvent. The solution is introduced into a flash
evaporator chamber, and solvent vapors are removed from the
evaporator chamber by a compressor. The vapors are compressed and
--3--
i 172984
then introduced into a condenser chamber wherein the vapors are
condensed and the liquid, organic solvent is recovered for reuse in
the process. The halogenated organic solvents have low heats of
vaporization, and low specific heats so that minimum heat is
required in flashing the solvents in the flash evaporator. Further,
solvents having relatively low boiling points can be used thereby
allowing use of low grade heat energy in the process.
Further efficiency is achieved by continuously circulating a
heat exchange medium between the condenser chamber and the flash
evaporator chamber. Heat is transferred from the heat exchanger
medium in the flash evaporator chamber to aid in the flash evapora-
tion of the organic solvent therein. Heat is recovered and
transferred to the heat transfer medium in the condenser chamber by
the condensing vapors.
Bituminous organic material is withdrawn from the evaporator
chamber, and it has been found that the bituminous material can
unexpectedly be used in many applications without further treatment
or refinement. The bituminous material has been found to be
equivalent to or better than gilsonite in those uses for which
gilsonite is presently in demand, such as in printers ink, pipeline
insulation, varnishes and paints, concrete foundation sealer, black
top paving sealer. The bituminous material has also been found to
provide excellent coatings for parking terraces, foundations,
bridges, wood surfaces of any kind, and underseal coatings for
automobiles, locomotives, and other equipment where rust inhibitors
are very important. In addition, of course, the bituminous material
can be refined for use as a fuel and petrochemical feedstocks.
Additional objects and features of the invention will become
apparent from the following detailed description taken together with
the accompanying drawings.
T HE DRAW I NGS
Particular embodiments of the present invention representing the
--4--
1 17298~
best mode presently contemplated of carrying out the invention is
illustrated in the accompanying drawings, in which:
Fig. 1 is flowsheet of the process of this invention;
Fig. 2 is an elevational, side view of a belt conveyor which
can be used in separating the solution of solvent and bituminous
material from the particulate sands;
Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2;
Fig. 4 is an end view of the belt conveyor of Fig. 2;
Fig. 5 is a schematic representation of another type conveyor
which can be used in the process in place of the belt conveyor;
Fig. 6 is an elevational, side view of a preferred embodiment of
the solvent flashing and condensing system of this invention;
Fig. 7 is a cross-sectional view through the flash evaporator
chamber taken on line 7-7 of Fig. 6;
Fig. 8 is a cross-sectional view through the condenser chamber
taken on line 8-8 of Fig. 6; and
Fig. 9 is an enlarged cross-sectional through one of the heat
pipes taken on line 9-9 of Fig. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A general flowsheet of the process of this invention is shown in
Fig. 1. In the first step of the process, oil sand or tar sand is
mixed with a halogenated organic solvent. The halogenated, organic
solvent dissolves the bituminous material in the sands to produce a
slurry of the particulate sands suspended in the organic solvent
solution containing the dissolved bituminous material. The mixing is
preferably accomplished in a mixing vessel 20 having appropriate
means for agitating the contents thereof so as to produce a
substantially uniformly dispersed slurry.
The halogenated organic solvent employed has a density greater
than that of water and is essentially immiscible in water. The
solvent is also capable of dissolving the bituminous organic material
in the oil sands or tar sands. The halogenated organic solvent is
--5--
1172984
preferably selected from the group consisting of methylene chloride,
trichloromonofluoromethane, chloroform, carbon tetrachloride, bromo-
trichloromethane, dibromotetrafluoromethane, trichloroethane, tri-
chloroethylene, tetrachloroethane, trichlorotrifluoroethane, dibromo-
tetrafluoroethane, dichlorotrifluoroethane, and tetrachloroethylene.
The temperatures and pressures employed in the mixing vessel
are not per se critical. Atmospheric pressure and temperatures are
preferred as being most cost efficient generally. Subatmospheric
pressures would generally be avoided as being unnecessary and
costly. Pressures greater than atmospheric could be employed to
minimize solvent evaporation losses or for operation at temperatures
above the normal atmospheric boiling point of the solvent which is
being used. Atmospheric temperatures within the range of about 50 to
300 degrees F are preferably employed, with the proviso that the
temperature is less than the boiling point of the solvent at the
pressure which is being used. It is pointed out, however, that one
of the benefits of the present invention is its use of mild operating
conditions to avoid unnecessary energy requirements in operating the
process.
The solvents used in the present process are generally highly
volatile which aids in the efficient separation of the solvent and
bituminous organic material as described hereinafter. To prevent
loss of solvent vapors from the mixing vessel, a water cap is main-
tained in the vessel. The water cap forms a separate phase on top of
the solvent-sand slurry and prevents volatilization of the solvent.
The slurry is withdrawn from the mixing vessel 20 and continu-
ously transferred onto a conveyor system 21 which is at least
partially submerged in water, with the slurry being fed onto the
portion of the conveyor which is submerged in the water. As illus-
trated diagramatically in Fig. 1, the conveyor can be of the inclined
drag line type comprising an endless belt 22 which travels about end
pulleys in an elongated circuitous looop within a housing containing
--6--
1 172984
the belt 22. A plurality of paddles or cleats 23 are attached to the
belt 22 in longitudinally spaced positions along the belt 22. Sand is
moved upwardly along the inclined housing by the cleats 23. Other
conveyor systems which have been found to be useful in the present
invention will be described hereinafter.
The slurry is withdrawn from the mixing vessel 20 and continu-
ously transferred onto a conveyor system 21 which is at least
partially submerged in water, with the slurry being fed onto the
portion of the conveyor which is submerged in the water. As
illustrated diagramatically in Fig. 1, the conveyor can be of the
inclined drag line type comprising an endless belt 22 which travels
about end pulleys in an elongated circuitous loop within a housing
containing the belt 22. A plurality of paddles or cleats 23 are
attached to the belt 22 in logitudinally spaced positions along the
belt 22. Sand is moved upwardly along the inclined housing by the
cleats 23. Other conveyor systems which have been found to be useful
in the present invention will be described hereinafter.
Generally, the sands are moved through the water by the
conveyor means, and the solution of bituminous organic material
dissolved in the halogenated organic solvent quickly separates from
the particulate sands and forms a separate organic phase beneath
the water phase. The organic phase comprising the halogenated
solvent is heavier than the water and is essentially immiscible in
the water. In addition, the sands are preferential]y wetted by the
water phase. Although not intending to be limited to any particular
theory, it is believed that the rapid separation of the organic phase
and the sands is due to the preferential wetting of the sands with
the water and the immiscible heavier nature of the organic solvent
phase. Irrespective of any theory, it has been found that the
organic phase quickly and effectively separates from the sand and
forms a separate phase beneath the water phase. The particulate
sands continue to move upwardly through the water and emerge from
--7--
~172984
the surface of the water so that the sand particles are wetted
essentially only by water and contain essentially no organic solvent.
The sands emerging from the water phase in the conveyor
mechanism 21 will generally be essentially cleaned of any bituminous
material if an adequate ratio of solvent to tar sands or oil sands is
utilized in the mixing vessel and if residence time in the mixing
vessel is adequate for the solvent is dissolve the bituminous material
from the sands. Generally, the solvent to tar sands or oil sands
ratio will be about 30 to 50 gallons of solvent per ton of tar sands
or oil sands. The residence time in the mixing vessel is generally
between about one to ten minutes. Operation with somewhat less
solvent per ton of sands and with less residence time in the mixer is
feasible; however, the sands emerging from the surface of the water
in the conveyor system may contain some residual bituminous
material thereon. In such cases, a cascade type separation may be
used, wherein the water wetted sands is mixed with additional
solvent and then introduced into a second conveyor system ( not
shown in drawing) similar to the conveyor system 23 wherein the
solvent phase is separated from the sands. The temperature of the
water in the conveyor system 21 will generally be maintained about
the same as the temperature of the slurry which is being introduced
thereinto. The conveyor system preferably operates at atmospheric
pressure .
The organic phase containing the bituminous material dissolved
in the halogenated organic solvent is recovered from beneath the
water phase in the conveyor system 21 and preferably treated to
separate the organic solvent from the bituminous material. When a
cascade type separation is used, solvent is made to move counter-
currently through the cascade system, with the solvent being with-
drawn from the initial unit of the cascade system being receovered
and treated to separate the organic solvent from the bituminous
material. As illustrated, the recovered organic phase containing the
--8--
1 172984
bituminous material is introduced into a flash evaporator chamber 24
wherein the organic solvent is flashed from the bituminous material.
The pressure in the evaporator chamber is maintained at a value
less than the pressure of the organic solution which is being intro-
duced thereinto by withdrawing vapors of the organic solvent from
the evaporator chamber 24 by a compressor 25. Generally, the
evaporator chamber 24 will operate at a subatmospheric pressure or
vacuum of about lOto 20 inches of water. The vapors are compressed
by the compressor 25 to between about atmospheric pressure and 50
ps)unds per square inch absolute, and the compressed vapors are
introduced into a condenser chamber 26.
The vapors in the condenser chamber 26 are brought into heat
exchanging relation with a heat exchange medium, whereby the
vapors are condensed. As illustrated in Fig. 1, a heat exchange
medium, such as water, is continuously circulated by pump 27
through a closed loop which extends from the evaporator chamber 24
to the condenser chamber 26. As the heat exchange medium circulates
through the portion of the closed loop within the condenser chamber
26, heat is transferred to the heat exchange medium by the
condensing vapors. The heated heat exchange medium then circulates
through the portion of the closed loop in the evaporator chamber 24,
whereby heat is transferred from the heat exchange medium to aid in
the flash evaporation of the or anic solvent therein. As a result, the
heat exchange medium is cooled in the evaporator chamber 24, and
the cooled heat exchange medium is then recirculated to the portion
of the closed loop in the condenser chamber 26. By utilizing the heat
liberated by the condensing vapors in the condenser chamber 26 to
provide at least a portion of the heat required in flashing the
solvent in the evaporator chamber 24, little if any additional heat is
needed. The work input by the compressor usually provides all the
equivalent heat necessary in the system; however, as shown, a
supplemental heating coil can be positioned in the evaporator
_g _
1172984
chamber 24 through which a heated medium can be passed if nec-
essary. A supplemental cooling coil can also be positioned in the
condenser chamber 26 through which a cooling medium can be passed
to aid in the condensation of the vapors in the condenser chamber 26
if necessary. Alternatively, a heating unit and cooling unit could be
provided on the closed loop through which the heating medium is
circulated by the pump 27. The heating unit would add additional
heat to the heat exchange medium flowing from the condenser
chamber 26 to the evaporator chamber 24, and the cooling unit would
cool the heat exchange medium moving in the opposite direction of
the closed loop.
The temperatures employed in the evaporator chamber 24 and the
condenser chamber 26 are dependent upon the boiling point of the
solvent which is used. The solvents have relatively low boiling
points and are highly volatile, i.e., have relatively low heats heats
of vaporization. The relatively low temperatures and the low heats of
vaporization contribute to the high efficiency which is achieved in
the separation of the solvent from the bituminous material. In
addition to the efficiency achieved by the heat exchange system in
the evaporator chamber 24 and condenser chamber 26, the low heats
of vaporization of the solvents of this invention minimizes the amount
of heat required in flashing the solvents in the evaporator chamber
24. By virtue of the low boiling temperatures of the solvents which
are used, heating requirements are further reduced and low grade
heat sources can be employed. In addition to the above benefits, the
solvents of this invention are inflamable and, thus, do not create a
fire hazard. Further, the solvents are completely inert with respect
to the bituminous material which is extracted from the tar sands or
oil sands, and the recovered solvent can be reused over and over
without any effect on its chemical and physical properties, including
its nonflamability. The condensed solvent which accumulate in the
condenser chamber is withdrawn therefrom and recycles. A solvent
--10--
1172984
holding tank 55 (Fig. 1) is advantageously employed to store
recovered solvent prior to its reuse in the process.
The bitminous materials, which accumulate in the evaporator
chamber 24 as the solvent is flashed, forms a liquid phase at the
bottom of the evaporator chamber 24. The bituminous material is
withdrawn from the evaporator chamber 24, and as mentioned here-
inbefore, the recovered bituminous material can be used in many
applications and uses without further treatment or refinement. In
addition, the bituminous material can be further refined for use as a
fuel and petrochemical feedstock.
A preferred embodiment of a belt conveyor apparatus which can
be employed in place of the drag line conveyor of Fig. 1, is
illustrated in detail in Figs. 2-4. The belt conveyor comprises an
endless belt 28 which travels in an elongated circuitous loop around
spaced apart drums 29 and 30 which rotate about a substantially
horizontal axis. An upper bearing assembly supports the upper
portion of the belt 28 as it travels from the upper side of one drum
29 to the upper side of the other drum 30. The upper bearing
assembly comprises spaced apart sets of roller bearings. Each set of
roller bearings comprises a plurality of rollers 31 as shown in Fig.
3 which are positioned so as to form the upper portion of the belt
into a substantially deep "V" trough as it passes from drum 29 to
drum 30. As shown, the sets of roller bearings are supported on
vertical support members 32 spaced along the length of the belt 28
between the drums 29 and 30. The belt 28 forms flat ends of the
trough as it passes over the respective drums 29 and 30.
A body of water is maintained in the trough formed by the
upper portion of the belt 28, and the slurry of sand and organic
solvent from the mixing vessel is fed to the trough near or adjacent
to drum 29 through an appropriate feed chute (not shown) which
extends beneath the surface of the water. The particulate sands
which are deposited on the belt 28 with the slurry moves on the belt
1 l729~4
28 from the one drum 29 adjacent to the feed chute 32 to the other
drum 30. As the particulate sands moves through the body of water
the solvent phase containing the dissolved bituminous material forms
a separate phase beneath the water on the belt 28. The particulate
sands move upwardly through the surface of the body of water as the
belt 28 passes around the upper portion of the drum 30. The sands,
which are wetted by water but not by the organic solvent finally
falls from the belt 28 as the belt 28 continues its movement around
drum 30, with the sands being disposed of or recovered for further
use as a clear sand aggregate or for further treatment to recover
mineral values therefrom. The organic phase comprising the solvent
and bituminous material is continuously withdrawn from beneath the
body of water in the trough formed by the belt 28. A plurality of
spaced, flat rollers 34 are provided to support the lower portion of
the belt 28 as it passes from drum 30 back to drum 29.
A third embodiment of conveyor apparatus which can be
employed in place of the drag line conveyor or the belt conveyor is
shown schematically in Fig. 5. The conveyor shown in Fig. 5
comprises an auger or screw 35 which is mounted within a housing
and the units is inclined. The slurry from the mixing vessel is
introduced near the bottom end of the auger or screw 35, and a body
of water is maintained in the housing so as to submerge at least the
greater portion of the auger or screw 35. As the auger or screw
rotates, it moves the particulate sands upwardly through the body of
water, and the organic solvent solution separates from the sands and
forms a separate phase beneath the body of water. The cleaned,
water wetted sands are ejected from a port 36 in the upper end of
the housing above the body of water therein. The organic phase
containing the solvent and bituminous material is withdrawn from a
port 37, the bottom end of the housing and below the body of water
therein.
-12-
1172984
A particularly preferred embodiment of the solvent flashing and
condensing system of this invention is shown in Figs. 6-9. The flash
evaporation chamber 24 is positioned side-by-side of the condenser
chamber 26. Means are provided for introducing the solvent solution
into the evaporator chamber 24. As illustrated, a plurality of spray
nozzles 40 are provided in the top portion of the evaporator chamber
24. with the spray nozzles 40 being connected to a manifold which in
turn is connected to a supply port in the evaporator chamber
through which the solvent solution is supplied to the manifold.
Positioned just above the spray nozzles 40 is a mist elimination
mechanism 41 which collects and coalesces small droplets of liquid.
The mist eliminator 41 comprises a mesh grid as is well known in the
art. Above the mist eliminator 41 is a large port for withdrawing
solvent vapors from the evaporator chamber. This port is connected
by a conduit 42 to the intake of a compressor 25. As will be
described hereinafter, heat exchange means are provided below the
spray nozzles 40 in the evaporator chamber 24 for providing heat
necessary to flash the solvent from the solution being sprayed into
the evaporator chamber 24.
The compressor 25 compresses the solvent vapors and the com-
pressed vapors are transferred through conduit 43 to an inlet port in
the top of the condenser chamber 26. The vapor compressor 25 can be
any of the type used in large commercial refrigeration systems. The
compressed vapors contact heat exchange rr.eans in the condenser
chamber 26 which cool the vapors so that the vapors condense.
The heat exchange means associated with the condenser chamber
26 and the evaporator chamber 24 comprises at least one elongate,
sealed container, such as a conduit or pipe 44 which has one end
thereof positioned within the flash evaporator chamber 24 and the
other end thereof positioned within the condenser chamber 26. A heat
exchange medium, comprising any of the commercially available
--13--
1 172984
refrigerants, is charged into the sealed conduit 44 to form a working
fluid therein having a liquid phase in equilibrium with its vapor
phase within the conduit 44.
~ eans are provided for moving the liquid phase of the working
fluid from the end of the conduit 44 positioned within the evaporator
chamber 24 to the other end of the conduit positioned within the
evaporator chamber 26, so as to cause the vapor phase of the
working fluid to migrate generally from the end of the conduit 44
positioned within the flash evaporator chamber 24. In operation, the
vapor phase of the working fluid absorbs heat in the portion of the
conduit 44 positioned in the condenser chamber 26 and thus cool the
condensing solvent vapors in the condenser chamber 26. The vapors
of the working fluid then move to the portion of the conduit 44
positioned within the evaporator chamber 24, wherein heat is
transferred to the solvent which is being flashd from the solution of
bituminous organic material and solvent being sprayed into the
evaporator chamber 24. The working fluid condenses in the portion of
the conduit 44 positioned within the evaporator chamber, and means
are provided for moving the liquid phase to the portion of the
conduit 44 positioned within the condenser chamber 26. A capillary
wick structure is advantageously used on the inner surface of the
conduit 44 at least as a portion of the means for moving the liquid
phase of working from the evaporator chamber 24 to the condenser
chamber 26. The capillary structure may be comprised of grooves
formed on the inner surface of the conduit 44, or as shown in Fig.
9, a layer of wire or fabric mesh 45 is positioned around the inner
surface of the conduit. As shown, a temperature gauge 46 and
pressure gauge 47 can be installed through the end flange 48 of the
conduit 44 to measure the working parameters within the conduit 44
and changing of the working fluid thereto. In addition to the
capillary structure, the conduits 44 are preferably slanted at least
slightly so that the end portions thereof positioned within the
--14--
1 172984
evaporator chamber 24 is higher than the corresponding end portions
positioned within the condenser chamber 26, whereby the working
fluid will move from the higher ends under the force of gravity.
The organic bituminous material from which the solvent has
flashed in the evaporator chamber 24 accumulates at the bottom of
the evaporator chamber 24 and is withdrawn through a pump 50. An
auxilliary heating means can be positioned near the bottom of the
evaporator chamber 24 to maintain the organic bituminous material
at a temperature at which it can be pumped to storage or packaging
facilities. The auxilliary heating means can be a conventional tube
and shell heat exchanger 51 (Fig. 6 and 7) which uses hot water or
low pressure steam.
The condensed solvent accumulates in the condenser chamber 26
and is withdrawn by pump 52 for recycle as described hereinabove.
An auxilliary heat exchange means can be positioned within the
condenser to cool the condensate. A conventional tube and shell heat
exchanger 53 ( Figs. 6 and 8) can be used, with the heat exchange
medium being a liquid such as chilled water. Means for removing
noncondensibles from the condenser chamber 26 can be provided as
shown in Fig. 6. A high pressure compressor 54 withdraws the
noncondensibles and some solvent vapors from the condenser chamber
26 and discharges the high pressure gases to a cooling chamber 55.
The cooling chamber 55 has a conventional heat exchange means
therein for cooling the high pressure gses, whereupon the con-
densable solvent vapors condense and are returned to the condenser
chamber 26 as illustrated. Although not illustratd, the condensate
from cooling chamber 55 can be recycled directly to the solvent
holding tank 59 ( Fig .1 ) . Non-condensibles are vented through a
discharge conduit 56 and associated pressure responsible valve 57.
The pressure responsive valve is adapted to maintain the desired
pressure in the cooling chamber 55 as the noncondensibles are
--15--
1 172984
vented. A float valve 58 is associated with the conduit through
which the condensate is withdawn from the cooling chamber 55. The
float valve 58 maintains a preset level of condensate in the cooling
chamber 55 and thereby cooperates with the pressure responsive
valve 57 in maintaining the desired pressure within the cooling
chamber 55.
Whereas there are here illustrated and described embodiments of
processes and apparatus presently contemplated as the best mode of
carrying out the invention, it is to be understood that various
changes may be made without departing from the subject matter
coming within the scope of the following claims, which subject matter
is regarded as the invention.
--16--
