Note: Descriptions are shown in the official language in which they were submitted.
~585~8
BACKGROUND OF THE INVENTION
Field of the Invention:
This invention relates to a cleaning method and
apparatus for removing liquid substance such as water, oil
or the like and/or solid substance such as zincing or the
like which is adhered to the surface of an object. It also
concerns a method and an apparatus for efficiently
recovering substance such as plated material adhered to the
surface of an object to be processed, by causing such
materials to be evaporated in a vacuum.
Description of the Prior Art:
Such procedures as pickling, shot-working, and in-air
oxidation removal have heretofore been well known in the art
as methods of removing zincing provided on the surfaces of
an automobile body, for example.
Of such conventional methods, pickling is most commonly
employed, but it is disadvantageous in that the cleaning
liquid used therewith tends to cause environmental pollution
and also in that the running cost is high and skilled
workers are needed. Shot-working also has such
disadvantages that the running cost is high and difficulties
are experienced in processing shot-particles having zinc
adhered thereto. Further, the in-air oxidation removal
procedure is disadvantageous in that oxide tends to be
formed on the object to be processed per se and the
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2058508
dezincing ability is poor. Thus, in the case where i ron
plate is melted for recycling, unmelted material such as
iron oxide, zinc oxide or the like and/or zinc is caused to
infiltrate into the wall of the furnace so that the life
span of the furnace tends to be shortened.
Also well known in the art is a method of recovering
zinc, nickel and/or lead adhered to the surface of an
automobile body and/or oil adhered thereto, by increasing
the temperature of the vacuum atmosphere in which such a
body is placed. However, due to the fact that no
convection-heating means is provided, such conventional
method is disadvantageous in that the temperature increasing
rate in the range of O to 500i-C is extremely low; thus, when
it is attempted to effect dezincing of 6,000 tons of scrap
per month, a large-sized equipment is inevitably required so
that the cost merit is lost because of its high initial
cost. To cope with such problems, it may be conceivable
that oxidation-heating is effected during the low-
temperature period while vacuum-heating is carried out
during the evaporation period. With such a procedure,
however, metal oxide is formed so that the vacuum-
evaporation temperature should be elevated as a matter of
course; thus, to completely remove the zincing, the
temperature should be elevated for a long period of time.
In this case, too, the cost merit is lost as in the above-
mentioned cases.
As mentioned above, the prior-art method is
disadvantageous in that the temperature rising rate of the
conventional vacuum furnace is low; heating with inert gas
such as nitrogen gas or the like is high in running cost;
2058508 27877-7
oxidation-heating requires that the evaporation temperature be
elevated so that the evaporation rate turns out to be slow,
which has adverse effect on the running cost or the like.
SUl!qMARY OF THE INVENTION
Accordingly, it is an object of the present invention
to obviate the above-mentioned drawbacks of the prior art.
The present invention involves two aspects, i.e.,
method and apparatus.
A first major embodiment of the method aspect of the
present invention provides a method of cleaning a surface of a
solid ob]ect to be processed, which comprises the steps of
placing the object in a closed atmosphere, and heating and
evacuating the closed atmosphere after reducing the pressure in
the closed atmosphere, or reducing the pressure in the closed
atmosphere after increasing the pressure in the closed space with
a non-oxidizing gas and heating the closed atmosphere, thereby
removing liquid substance and/or solid substance adhered to the
object, through variations in the temperature and pressure in the
closed atmosphere.
A first major embodiment of the apparatus aspect of the present
invention provides an apparatus for cleaning a surface of a solid
object to be processed, which comprises a closed container having
a closed atmosphere in which the object is to be placed; heating
means for elevating the temperature within the closed container;
condensing means in communication with the closed container for
condensing metal or non-metal removed from the object; pressure
reducing means for reducing the pressure in the closed container
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through the condensing means; pressure increasing means for
increasing the pressure in the closed container with a non-
oxidizing gas; and preheating means for utilizing the gas for
the purpose of preheating the object.
A second major embodiment of the method aspect of the
present invention provides a method for efficiently recovering
substance such as zincing or the like adhered to a surface of
an object to be processed, by causing such substance to evaporate
in a vacuum, which comprises placing the object in a furnace
provided with heating means; elevating the temperature within the
furnace up to a predetermined level with the aid of an oxidizing
gas atmosphere; reducing the pressure in the furnace so that the
quantity of the oxidizing gas is reduced below the explosion
limit; feeding a reducing gas atmosphere into the furnace to
reduce the oxidization of the object; thereafter evacuating the
interior of the furnace while the interior of the furnace is
maintained under a predetermined evaporation temperature
condition; and introducing the substance evaporated from the
object processed to recovery means provided in communication with
the furnace, so that the evaporated substance is condensed in the
recovery means and recovered therefrom.
A second major embodiment of the apparatus aspect of
the present invention provides an apparatus for efficiently
recovering substance such as zincing or the like adhered to a
surface of an object to be processed, by causing such substance
to evaporate in a vacuum, which comprises heating means for
elevating the temperature within a furnace; condensing means
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for causing gas and/or liquid to be condensed; pressure
reducing means for reducing the pressure within the furnace
through the condensing means; and pressure increasing means
for increasing the pressure within the furnace by flowing a
reducing gas into the furnace.
Other objects, features and advantages of the present
invention will become apparent from the ensuing description
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view, partially in cross-section,
showing the cleaning system according to an embodiment of
the present invention.
Fig. 2 is a graph illustrating variations with time in
the pressure in the closed atmosphere and the temperature of
the object to be processed.
Fig. 3 is a front view showing a second embodiment of
the present invention.
Fig. 4 is a plan view of the apparatus shown in Fig. 3.
Fig. 5 is a front view showing a third embodiment of
the present invention.
Fig. 6 is a front view showing a fourth embodiment of
the present invention.
Fig. 7 is a graph illustrating the zinc recovery and
the quantity of residual zincing.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Description will now be made of a first embodiment of
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the present invention, and in accordance with this
embodiment, there is provided a method in which in an
attempt to remove metal or non-metal adhered to an object to
be processed, the object is placed in a hermetically closed
container; the interior of the hermetically closed container
is heated by heating means and evacuated after the pressure
therein is reduced by pressure reducing means, or
alternatively a non-oxiziding gas is fed into the
hermetically closed container by pressure increasing means
and the interior of the container is heated under the heat
transfer action of the non-oxidizing gas, and subsequently
the container is evacuated and the interior of the container
is heated up to a temperature equal to or higher than the
boiling point of the metal or non-metal adhered to the
object to be processed, so that the metal or non-metal is
evaporated; and thereafter, the pressure in the container is
reduced while the interior of the container is kept under
the heated condition, and the vapor of the metal or non-
metal is recovered and passed to be condensed in condensing
means provided in a recovery line.
As the non-oxidizing gas, use is made of inert gas such
as nitrogen, argon or the like, and care is taken to prevent
the recovered substance from being oxidized when the
interior of the hermetically closed container is pressurized
and heated. The non-oxidizing gas may also be passed to a
pre-heating chamber and utilized to pre-heat the object to
be processed. It is reasonable to consider that the
substance such as metal or non-metal may be a composite one
consisting of several materials instead of a single
substance such as metal or non-metal; thus, preferably, the
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vapor pressure at the predetermined temperature at which the
object to be processed is heated, should be set up to be
variable over a predetermined range, and under such a
condition, selection should be made with respect to the
extent of pressure reduction (degree of the vacuum) within
the hermetically closed container, heating temperature, the
extent to which the inert gas is pressurized, and so forth.
Referring to Figures 1 and 2 of the drawings, the
apparatus for carrying out the above-mentioned method
according to the first embodiment of the present invention
will be described, which comprises a hermetically closed
container 3 having a hermetically closed space or atmosphere
2 in which an object 1 to be processed is placed; a heater 4
acting as heating means for elevating the temperature of the
substance adhered to the surface of the object to be
processed; a condenser 5 serving as means for causing the
evaporated substance or the like removed from the object 1
to be condensed; a pressure reducing pump 6 serving as means
for reducing the pressure in the hermetically closed
container 3 through the condenser 5; a gas cylinder 7
serving as means for increasing the pressure in the
hermetically closed container 3 with the aid of non-
oxidizing gas; and a pre-heating furnace 31 in which is
introduced nitrogen gas for cooling the heated object 1 to
use the nitrogen gas to pre-heat the object to be processed.
More particularly, the hermetically closed container 3
comprises a container body consisting of a hollow retort 11
and a heat insulating material 12 provided on the outer
surface of the retort 11; a rear heat insulating door 14
lined with a heat insulating material 13 and mounted at one
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side of the container body; a front heat insulating door 15
lined with a heat insulating material 15 and mounted at the
other side of the container body; a front door 17 mounted to
open and close an opening portion 16a of the front heat
insulating door 6, whereby a hermetically closed space or
atmosphere 2 is defined within the container 3. An agitator
21 is provided at the top of the hermetically closed
container 3, and a heating element 4 is provided in the
space 2 to elevate the temperature of the atmosphere 2.
Further, the condenser 5 is connected in communication with
the hermetically closed space 2 through piping 25 and also
with the pressure reducing pump 6 through piping 26. The
pressure reducing pump 6 is provided with an exhaust pipe
27. The nitrogen gas cylinder 7 is connected to the
hermetically closed container 3 via piping 30 including a
pressure regulator valve 28 and a pressure gauge 29.
In operation, the front door 17 is opened, and the
object 1 to be processed is loaded into the hermetically
closed container 3. Subsequently, the front door 17 is
lowered to close the opening portion 16a; the pressure
reducing (vacuum) pump 6 is operated, thereby reducing the
pressure in the space 2 of the closed container 3 down to
about 10-' to 10- 4 Torr. Then, nitrogen gas is supplied to
increase the pressure in the space 2 through the piping 30,
and the agitator 21 is operated. The atmosphere 2 is heated
up to a predetermined temperature by means of the heating
element 4 while being agitated by the agitator 21. As a
result, the temperature of the object 1 to be processed is
elevated under the heat transfer action of the nitrogen gas.
At a time point when a predetermined temperature
20~8S08 27877-7
(temperature at which evaporation does not occur too much)
is reached, the pressure in the atmosphere 2 is reduced, and
the object 1 to be processed is further heated so that
the substance adhered to the surface thereof is evaporated.
The pressure in the atmosphere is then caused to build up as
a result of the atmosphere being supplied with nitrogen gas,
and the atmosphere is cooled; the nitrogen gas, which is
heated to some extent, is introduced into the pre-heating
furnace 31 to pre-heat the object 1 to be processed. Fig. 2
illustrates variations with time in the pressure in the
closed atmosphere 2 and the temperature of the object 1 to
be processed. The evaporated substance is accommodated and
-condensed in the condenser 5. The object 1, when cooled, is
taken out, with the front door 17 open.
As will be appreciated from the above discussion,
according to this embodiment of the present invention, metal
or non-metal adhered to the surface of an object to be
processed can be most efficiently removed without using any
special cleaning agent, combustion flame or the like as in
the prior art. Advantageously, the cleaning process is
effected within a hermetically sealed processing atmosphere
so that there occurs no possibility of environmental
pollution; the substance adhered to the object to be
processed is evaporated in a vacuum and thus recovered in a
substantially pure form and can be recycled; the solid or
liquid substance adhered to the object to be processed,
whether it is metal or non-metal, can be removed with an
extremely high efficiency so that the running cost can be
reduced and automation can readily be achieved.
Referring to Figs 3 to 6, there are illustrated other
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embodiments of the present invention which may incorporate
the principles of the embodiment shown in Figs. 1 and 2 and
described above.
According to the present invention, in this aspect,
there is provided a method for removing liquid and/or solid
substance such as water, metal plating or the like adhered
to an object to be processed, wherein an object to be
processed is previously heated up to a desired temperature
in an oxidizing atmosphere furnace; the object to be
processed is then successively loaded into closed containers
which are arranged in contiguous relationship with and in
communication with each other; the pressure in each of the
individual closed containers is reduced by pressure reducing
means; and thereafter, the interior of each closed container
is heated by heating means and evacuated, or alternatively
reducing gas is supplied by pressure increasing means. The
interior of each closed container is deoxidized under the
reducing action of the reducing gas; then the interior of
each closed containers is evacuated and heated up to a
temperature equal to or higher than the boiling point of the
substance such as metal, galvanizing, oil or the like
adhered to the surface of the object to be processed,
thereby causing such substance to be evaporated.
Subsequently, each closed container is subjected to
pressure-reduction while being heated, and the vapor
resulting from the above evaporation is recovered which in
turn is accommodated and condensed in condensing means
provided in a recovery line.
As the reducing gas, use is made of hydrogen gas, gas
resulting from decomposition of NH~, or the like, and the
20S8508
product is subjected to sufficient deoxidation when the
pressure in each closed container is increased and the
temperature therein is also elevated or the interior thereof
is uniformly heated. It is also possible that such gas may
be circulated to the pre-heating chamber and used to reduce
the object to be processed.
With reference to the drawings, description will now be
made of the apparatus for carrying out the vacuum-
evaporation and recovery method according to embodiments of
the present invention. The heating furnace body 1 comprises
one or more chambers which are partitioned and can be
hermetically closed with a sealing door or doors. On the
bottom of each chamber, there are provided self-
running rollers for transporting trays 60 on which objects
to be processed are placed, and an pneumatic or hydraulic
device for actuating a pusher. Shafts for the self-running
rollers extend out of the the hermetically closed chambers
and are coupled to a self-running roller driving device.
Each chamber consists of a hollow retort covered with a heat
insulating material.
The most upstream chamber (left-hand side as viewed in
the drawing~ constitutes a front evacuation/substitution
chamber 3 which is provided with a sealing door 4 at one
side and a sealing door 5 at the rear side ( at the next
adjacent chamber side). The term "evacuation/substitution"
is used herein to mean both the case where the atomsphere in
the chamber is evacuated to be a vacuum and the case where
the atomosphere in the chamber is substituted with inert gas
such as nitorgen gas or the like. There are also provided a
door cylinder 6 for opening and closing the door 4; and a
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door cylinder 7 for opening and closing the door 5.
As shown in Fig. 4, there is provided a driving device
8 for carrying the trays 60 containing the objects to be
processed into the front evaporation/substitution chamber 3.
A cylinder 9 acts to push and deliver the objects processed
in the front evaporation/substitution chamber 3 into the
next adjacent chamber. The front evaporation/substitution
chamber 3 is also provided with an agitator 3a, a vacuum
pump 10 for evacuating the chamber, and condensing means 11
for recovering metal, water and/or oil removed from the
object to be processed. A gas circulating pipe 12 for
supplying pre-heating gas, and a recovery pipe 13 for
recovering the gas are coupled to the front
evaporation/substitution chamber 3.
A first vacuum-heating chamber 14 is provided in
contiguous relationship and in communication with the front
evaporation/substitution chamber 3. The chamber 4 is
provided at the input side with a sealing door 16 which can
be opened and closed by a door cylinder 15. The first
vacuum-heating chamber 14 is also provided with a heater 717
for heating the interior thereof; condensing means 18 and 19
provided in communication therewith for condensing
evaporated substance or the like removed from the object to
be processed; and a vacuum pump 20 acting as pressure
reducing means for reducing the pressure in the chamber 14.
An exhaust pipe is connected to the vacuum pump 20. The
first vaccum-heating chamber 14 may also be provided with
one or more agitator fans 23 if necessary.
A second vacumm-heating chamber 24 may have the same
construction as the first vacuum-heating chamber 14. More
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specifically, this chamber 24 is provided with a door
cylinder 25 for opening and closing a sealing door 26; a
heater 27; and condensing means 28 and 29. There are also
provided a vacuum pump 30, a vacuum valve 31, a filter 32,
and an agitator fan 33. The second vacuum-heating chamber
24 is also provided with a sealing door 34 at the rear side
thereof, which is driven to be opened and closed by means of
a door cylinder 35.
A third vacuum-heating chamber 36 is provided with a
sealing door 37; a door cylinder 38 for opening and closing
the sealing door 37; condensing means 39 and 40; a vacuum
pump 41; a vacuum valve 42; a filter 43; and a cooling fan
44. The third chamber 36 is also provided at the rear side
thereof with a sealing door 45, and a door cylinder 46.
The third heating chamber 36 is followed by a rear
evaporation/substitution chamber 47. The chamber 47 is
provided with a sealing door 49 which is opened and closed
by means of a door cylinder 48; a vacuum pump 50 for
evacuating the interior thereof; condensing means 51; and
drive means 52 (air cylinder) for taking our the trays 60
transported into the chamber 47. Although not shown in the
drawings, in addition to the elements mentioned above, a gas
cylinder containing nitrogen, hydrogen or the like is also
provided which is connected to the respective vacuum-heating
chambers 14, 24, and 36 through piping including a vacuum
valve and pressure gauge
With the above-mentioned arrangement, when the object
to be processed which is placed on the tray 60, is cooled by
nitrogen gas and carried into the front
evaporation/substitution chamber 3 under the action of the
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drive means 8, the sealing door 4 is closed under the action
of the door cylinder 6. In this case, the sealing door 5 is
closed, and thus the chamber 3 is hermetically closed.
Then, the vacuum pump 10 is actuated so that the chamber 3
is evacuated, and the object to be processed is subjected to
evaporation/substitution and pre-heated by the nitrogen gas
supplied through the gas circulating pipe 12 and heated in
the rear evaporation/substitution chamber 47 or
alternatively by heating means. Alternatively, the object
to be processed may be subjected to evaporation/substitution
without being pre-heated.
Subsequently, the sealing door 5 is opened under the
action of the door cylinder 7, and the sealing door 16 is
also opened under the action of the door cylinder 15. The
tray 60 is pushed under the action of the cylinder 9, and
carried into the first vacuum-heating chamber 14 by means of
the self-running rollers. Then, the sealing door 16 is
closed, and thereupon the vacuum pump 20 is actuated so that
the chamber 14 is evacuated, and the interior of the chamber
14 is heated by the heater 17. In this way, water, plated
metal, oil or the like is evaporated and removed from the
object to be processed which is placed on the tray 60,
depending on the temperature in the chamber. The substance
thus evaporated and removed is fed and condensed in the
condensing means 18 and 19. In the case where there is
water and/or oil, the heating in the chamber is effected at
a relatively low temperature so that primarily liquid
substance such as water, oil or the like is removed and
recovered.
Thereafter, the sealing door 26 is opened; the object
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to be proeessed is transferred to the second vacuum-heating
chamber 24; then the sealing door 26 is closed; thereafter,
pressure reduction, heating and condensation of evaporated
substance are effected as in the first vacuum-heating
chamber 14. The heating in the second vacuum-heating
chamber 24 is effected at a higher temperature than that in
the first vacuum-heating chamber 14 so that primarily solid
substancesuch as zincing is vacuum-evaporated.
Further, the object to be processed is transferred to
the third vacuum-heating chamber 36 and subjected there to
heating at a higher temperature so that zincing or the like
is removed therefrom. Subsequently, the object to be
processed is carried into the rear evaporation/substitution
chamber 47, and when it is desired that the substance
removed from the object be recovered in a non-oxidized form,
the pressure in the chamber 47 is increased with nitrogen
gas, and the substance is taken out after being cooled with
the nitrogen gas. The nitrogen gas thus heated is
introduced to the respective vacuum-heating chambers through
the gas circulating pipe 12. Both the front
evaporation/substitution chamber 8 and the rear
evaporation/substitution chamber 47 serve to prevent air
from flowing into the respective vacuum-heating chambers,
thus preventing the recovered substance from being oxidized.
As shown in Fig. 5, depending on the conditions for
recovery, the vacuum-recovering apparatus may be eonstrueted
to eomprise three ehambers, i.e., a front and a rear
evaporation/substitution ehamber and an intermediate vaeuum-
evaporation ehamber. It may also be eonstrueted to eomprise
a single ehamber without any evaporation/substitution
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chamber, as shown in Fig. 6. Effectiveness of such
constructions has also been experimentally confirmed.
The graph of Fig. 7 illustrates the relationship with
temperature between the zinc recovery and the quantity of
residual zincing which has been obtained as a result of zinc
removing test according to the method of the present
invention. The test was conducted under the following
conditions:
Object to be processed 300 Kg per piece
(shredded article)
Temperature 300-C, 500}C, 700CC, 900'C
Vacuum 5 to 6 x 10--~ Torr
Time Reduced for 60 minutes;
Vacuum-evaporated and recovered
for 600 minutes (Oxidation and
temperature increase effected
for 2 hours respectively)
In Fig. 7, circles indicate the recovery of zincing for
the case where the object to be processed was subjected to
oxidation and temperature elevation and then to reduction
with hydrogen gas and zincing was vacuum-evaporated and
recovered therefrom; triangles indicate the recovery of
zincing for the case where the object to be processed was
subjected to oxidation and temperature elevation and then
the zincing was vacuum-evaporated and recovered therefrom;
solid circles indicate the quantity of residual zincing for
the case where the object to be processed was subjected to
oxidation and temperature elevation and then reduction with
hydrogen gas and the zincing was vacuum-evaporated and
recovered therefrom; and solid triangles indicate the
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quantity of residual zincing for the case where the object
to be processed was subjected to oxidation and temperature
elevation and the zincing was vacuum-evaporated and
recovered therefrom.
As will be appreciated from what has been described
with reference to Figs. 3 to 7, according to the present
invention, metal oxide is removed from the object to be
processed by subjecting the latter to oxidation and
temperature elevation and then to reduction with hydrogen;
thereafter, the atmosphere in which the object to be
processed is placed is evacuated, and substance such as
zincing, oil, metal or the like adhered to the surface of
the object to be processed is vacuum-evaporated to be
removed and recovered from the object to be processed. Thus,
according to the present invention, the recovery of the
substance can be remarkably increased and the substance can
be completely removed at a lower temperature as compared
with the conventional method which comprises effecting
oxidation and temperature elevation and then vacuum-
evaporation and recovery. Furthermore, the cleaning and
processing procedures are performed in a hermetically closed
atmosphere or space so that there occurs no possibility of
environmental pollution or the like, and the running cost
can be reduced, automation can readily be achieved, and the
substance adhered to the surface of the object to be
processed can be recovered in a substantially pure form
since it is evaporated in a vacuum, so that the substance
thus recovered can be recycled.
While the present invention has been illustrated and
described with respect to some specific embodiments thereof,
2 0 ~ 8
it is to be understood that the present invention is by no
means limited thereto but encompasses all changes and
modifications which will become possible within the scope of
the appended claims.
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