Note: Descriptions are shown in the official language in which they were submitted.
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S P E C I F I C A T I O N
BACKGROUND OF THE INVENTION
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l. Field of the Invention
In one aspect this invention relates to vacuum ;
distillation systems. In yet another aspect this invention
relates to closed loop waste treating systems.
2. Prior Art
Vapor compression stills for distilling saline
water and the like are known in the art. Such devices
have a vacuum chamber for evaporation of pure water from
the saline solution, means for heating the saline solution
to an elevated temperature and a heat exchanger to recycle
some of the heat put into the purified water vapor during
vapor compression.
Similar vapor distillation apparatus has been
used to purify and concentrate plating solutions. The
concentrated solution is then recycled. Recycling reduces
the waste of raw materials and results in a produc.ion ~1
cycle having essentially zero pollution.
The prior art systems have achieved some success
in reducing pollution and recycling plating solutions. -
However, even the vapor compression systems have problems
which inhibit their use. The prior art systems generally
use a rotor or vane type compressor, which has rubbing
parts, to maintain a vacuum in the evaporation cha~ber
and compress solvent vapor evaporated from the contaminated
plating solution. This type of compressor is inef-icient
and requires a high degree of maintenance, especially
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when used in a system for concentrating plating fluids. Thus,
the system is costly to operate and lacks the desired reli-
ability. Maintenance problems can also result in expensive
down time while repairs are made to the system.
Prior art compressors also operate at a uniform
rate and, therefore, the output solution is a function of the
input solution. The resulting treated concentrate can be too
strong or too weak for direct recycling to the process
requiring further treatment to bring the solution to the
proper concentration for recycling.
According to the present invention, there is
provided a continuous treatlnent for use in a processing cycle,
the system being adapted to treat contaminated rinse water
eontaining valuable materials. The system ineludes a vapor
compression still having a housing, an evaporation chamber
contained within the housing, and a evaporation surface
eontained within the housing, a eompressor located at one
end of the housing adapted to accelerate the vapor formed
in the evaporation chamber and maintain the evaporation
ehamber at a reduced pressure, a fixed blade compressor
disposed radially about the compressor to reeeive and compress
the aeeelerated vapor, and a condensation chamber surrounding
the evaporation chamber and being adapted to transfer heat
given off by the condensing vapor to the evaporation chamber,
and means to feed eontaminated liquid to the evaporation
ehamber. Means is provided to withdraw eoncentrated liquid
from the evaporation chamber and return it to the processing
cyele, and means is provided for withdrawing the purified
eondensed vapor from the eondensation ehamber and returning
it to a rinse cycle.
A feature of this invention is the provision of
a stationary blade diffuser which receives and compresses
the vapors accelerated by the centrifugal compressor. The
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stationary blade configuration reduces the volume of the
diffuser or volute. The smaller diffuser results in a
smaller operating unit which reduces cost and the amount of
expensive space consumed in the plant. Also, a stationary
blade compressor more efficiently compresses the vapor
decreasing the amount of energy which must be added to the
system.
A further feature of a specific embodiment of the
invention is the provision of an archemedian evaporation
surface and heat exchanger which receives a continuous flow
of the solution to be concen-trated. The evaporation chamber
is cone-shaped with the apex at the bottom. An evaporation
surface, mounted a approximately righ angles to the cone's
surface, extends in a continuous spiral along the inner -~
surface of the cone. The solution to be concentrated is
- fed onto the evaporation surface near the base or supper
portion of the cone and will flow slowly downward along the
spiral towards the apex at the bottom. The evaporation
surface and cone form a trough which holds the solution as
it flows towards the apex.
- A heat absorbtion surface extends into the
compression chamber which surrounds the cone-shaped
evaporation chamber. The heat absorbtion surface absorbs
the latent heat of vaporization given off by the condensing -
vapor and transfers the heat to the spiral evaporation
surface.
As an alternative evaporation surface in a specific
embodiment of the invention, the vapor compression chamber
can contain several conical evaporation surfaces. In general,
the evaporation chamber will have at least 4 of the hollow
conical evaporation surfaces disposed within the chamber.
Liquid to be concentrated is sprayed or fed onto the surface
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of the cones near their apex, the liquid adhering to the
surface as it falls towards the bottom of the evaporation
chamber. The solvent evaporates from the liquid film and
the resulting vapor is drawn into the centrifugal compressor
where it is compressed. The compressed gas is forced into
the hollow interior of the cone where it condenses on the
inner walls of the cone giving off latent heat of vaporization
to the cone wall which, in turn, conducts the heat to the
liquid being concentrated. The concentrated liquid and
condensed pure solvent flow or fall to the bottom of the
evaporation chamber into separate chambers from which they
can be withdrawn.
This structure provides a large surface area for
evaporation in a small compact structure which is easily
assembled.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawing:
Fig. 1 is a schematic diagram of a plating line
having a vapor compression system associated therewith;
Fig. 2 is a side elevation of a vapor compression
system showing an evaporation chamber of this invention;
Fig. 3 is an enlarged sectional view of the
evaporation surface of Fig. 2 showing the surface in
greater detail;
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Fig. 4 is a top view taken along the line 4-4
of Fig. 2 showing the stationary blade diffuser blades
used in compressing the gas; and
Fig. 5 is a side view in section of an evaporation
chamber having a plurality of conical evaporation surfaces.
DETAILED DESCRIPTIO~J OF THE PREFERRED EMBODIMENTS
A typical plating system is shown in Fig. 1.
Parts to be plated are placed in a plating tank 10 which
contains a solution of ions to be deposited on the part as
a metal layer. After the desired metal layer is deposited,
the parts are moved to rinse tanks 11, 12 and 13, where
the plating solution adhering to the parts is washed off.
During the plating cycle a substantial amount of plating
solution, containing valuable plating ions and rinse water
is carried from tank to tank. As shown, water from tank
13 is used to keep tank 12 full and liquid from tank 12
is used to fill tank 11. The water in tank 11 eventually
contains large amounts of metal ions and plating additives.
Before pollution control laws such rinse water was generally
dumped into the nearest stream or sewer and additional
fresh water added to tank 13 as needed. With the increasing
cost of metals throwing away the rinse water has become
uneconomical.
In the system of this invention, the contaminated
rinse water from tank 11 passes through a conduit 16 into
a heat exchanger 14 where the contaminated rinse water
absorbs heat from purified water which enters the heat
exchanger via conduit 18. Pipe 20 carries the preheated
rinse water to a vapor compression unit 21.
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The preheated rinse water is subjected to reduced pressure and
condensation heat from a vapor compression cycle which concen-
trates the rinse water and evaporates pure water. Vaporizing
pure water concentrates metal ions in the remaining rinse
water to the same concentration as is in the plating tank 10.
The concentrated solution is then returned to the tank by a
conduit 22. If desired,the concent~rate can be pumped to a
holding tank (not shown) and held until a quantity of concen-
trate has been collected. Then the concentrate can be added
to the plating bath as a batch.
One vapor compression unit 21 useful in this invention,
is shown in greater detail in Figs. 2 and 3, which also show a
detailed heat exchanger. The rinse water to be concentrated
enters the heat exchanger 14 at the bottom through pipe 16
passing upward and exits at 19. The rinse water passes through
pipe 20 into an auxiliary heater 24 which can supply additional
heat to help start the vapor compression apparatus when desired.
The contaminated liquid passes through a valve 25
which controls the rate at which contaminated rinse liquid
flows onto an archemedian spiral surface 26. The spiral
surface 26 projects from the wall at approximately a right
angle forming a natural trough which holds the contaminated
liquid as it flows down the spiral.
A housing 28 having an inner wall 29 and an outer
wall 30 supports the spiral 26. The inner wall 29 and outer
wall 30 form a vapour condensation chamber 32 therebetween.
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The housing's inner chamber 36, which forms an
evaporation chamber, is maintained at a reduced pressure
of about 0.5 to 1.5 psia. The chamber 36 is continuously
evacuated by means of a centrifugal compressor 38 mounted
atop the housing 29. The compressor 38 draws pure water
vapor which has evaporated from the contaminated rinse
water out of the chamber 36 through a screen 40. The
screen 40 separates any liquid droplets in the vapor allow- -
ing only vapors to pass into the compressor 38. Separating
the droplets from the vapor protects the centrifugal com-
pressor vanes and prevents carryover of the contamination.
As shown, the compressor 38 is driven by an
electric motor 41 but other drive means would be acceptable.
The vapor from the contaminated liquid is drawn
into the compressor 38 where it is accelerated to a high
velocity by the impellers 42 and pushed into a stationary
blade compression unit 44 as shown in greater detail in
Fig. 4. The stationary blades 45 allow the vapor to slow
in velocity which raises the pressure. The compressed gas
moves through an annular chamber 46 and into the condensation
chamber 32.
In the condensation chamber 32, the vapor con-
denses to form a liquid. The latent heat of vaporization
given off by the condensing vapor is absorbed by fins 47
which extend into the condensation chamber and the inner
wall 29 of the housing. The heat is transferred to the
archemedian spiral. The heat evaporates the water from the
contaminated water forming more water vapor. The liquid
is withdrawn from the chamber 32 at outlet 48 into line
49 which enters a vacuum pump 50. The pump 50 removes air
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and other entrained gases from the purified water before
the water is returned to the rinse tank. The vacuum pump
50 can also be used to reduce the pressure in the evaporation
chamber when the vapor compression unit is being started.
The vacuum pump 50 can reduce the pressure in the conden-
sation and evaporation chamber to a level which insures
evaporation of the rinse water initially fed to the
evaporation chamber.
As shown, there is a line 52 which runs from line
54, the purified water, to line 20, carrying contaminated
rinse water to the vacuum still 21. A portion of the
purified water can be directly recycled via line 52 to
maintain the vapor compression apparatus at optimum feed
rate. This also allows the concentration output to be
varied by varying the concentration of the rinse water
entering the evaporation chamber. -
Turning to Fig. 5, a second embodiment of a
suitable evaporation chamber is shown. Liquid to be con-
centrated enters an evaporation chamber 62 contained in ~-
housing 60 via a line 63. The liquid is sprayed by nozzles
64 onto a plurality of cones 66 forming a falling thin film
of liquid. The cones 66 are hollow and provide a large
outer surface area for the evaporation of solvent. The
solvent vapor generated on the outer surface of the cones
66 is drawn upward into a centrifugal compressor 68 which
increases the velocity of the vapor.
The vapor passes into a volute or diffuser 70
where the gas slows and kinetic energy is changed into
pressure energy. The compressed vapor passes down an
annular passage 72 which surrounds
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the evaporation chamber 66 and into a reservoir area 74at the bottom of the housing 60. The compressed vapor will
enter conical condensation compartments 76 inside the cones
66 where the vapor will condense on the sides of the com-
partment and drip into the reservoir 74 at the bottom of
the housing. As the vapor condenses in the compartment 76,
it will from an area of reduced pressure in the compartment
which will tend to draw the compressed vapor upward into the
compartment. As the compressed vapor condenses in the
compartment, it transfers its latent heat of vaporization
to the cone wall which in turn transfers the heat to the
falling film of liquid to be concentrated.
Various modifications and alterations of the
system of this invention will become obvious to those
skilled in the art and it is understood that this invention
is not limited to the embodiment described hereinbefore.
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