JP2011020885A - Method for regenerating spent carbon dioxide gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively regenerating spent carbon dioxide gas exhausted from a carbon dioxide gas cleaning means as reusable high purity liquefied carbon dioxide gas. <P>SOLUTION: The method for regenerating spent carbon dioxide gas comprises: a distillation step introducing the spent carbon dioxide gas exhausted from the carbon dioxide gas cleaning means to a distillation tower 1 and rectifying the gas to remove impurities contained in the spent carbon dioxide gas; and a re-liquefying step of introducing the high purity gasified carbon dioxide gas bled from the distillation tower 1 into a condenser 3 to liquefy the gas. The regenerated carbon dioxide gas after re-liquefied is reused for the cleaning in the carbon dioxide gas cleaning means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention removes contaminants and unnecessary substances from a used carbon dioxide gas exhausted from a carbon dioxide gas cleaning device using high-pressure liquefied carbon dioxide gas as a cleaning solution to purify the carbon dioxide gas. As for the method of reusing as.

  Conventionally, as a method for dry cleaning clothes, bedding, and other fabric products, a cleaning method that uses carbon dioxide (carbon dioxide) that does not easily remain on the surface or inside of the object to be cleaned as a cleaning agent has been proposed without using organic solvents. (See, for example, Patent Document 1).

  The cleaning method using carbon dioxide gas as a cleaning agent is also used for cleaning semiconductor substrates in semiconductor manufacturing processes, removing unnecessary materials from electrical / electronic components and optical members, etc. Various carbon dioxide cleaning methods using dry ice flakes, subcritical or supercritical carbon dioxide, or liquefied carbon dioxide to which an additive for improving cleaning power is added have been proposed (for example, Patent Document 2). See ~ 3 etc.).

  By the way, the cleaning apparatus used for these carbon dioxide gas cleaning methods usually has few impurities, and uses a large amount of high-purity carbon dioxide gas for cleaning. However, if carbon dioxide after cleaning containing contaminants and the like is discharged to the outside of the cleaning device (in the atmosphere) every time it is used, it is not preferable in terms of the environment such as global warming, and the cost increases.

  Therefore, these carbon dioxide gas cleaning devices are provided with a recovery process for purifying and regenerating liquefied carbon dioxide gas exhausted from the cleaning tank through a filter that removes contaminants and the like. In addition, there are some equipped with a gas recovery device that compresses and recovers high-pressure gas (vaporized carbon dioxide) remaining in the cleaning tank after the cleaning is completed.

Special table 2003-516838 gazette Japanese Patent Laid-Open No. 2002-237481 JP 2006-297371 A

  However, in the method of removing contaminants through the filter as described above, impurities such as contaminants and unnecessary substances mixed into the carbon dioxide gas due to the cleaning of the object to be cleaned cannot be completely removed. There has been a problem that the regenerated carbon dioxide gas cannot be used for cleaning electric / electronic parts and optical members that require gas.

  In particular, in the semiconductor component industry field that requires precise processing, for example, an object to be cleaned such as a semiconductor wafer that must be managed for fine foreign substances is included in the carbon dioxide gas. The oil and particles that are present adhere to the object to be cleaned and damage the object to be cleaned.

  The present invention has been made in view of such circumstances, and can be used to efficiently regenerate used carbon dioxide exhausted from the carbon dioxide cleaning means as reusable high-purity liquefied carbon dioxide. The purpose is to provide a method for regenerating spent carbon dioxide.

  In order to achieve the above object, the method for regenerating used carbon dioxide gas of the present invention introduces spent carbon dioxide gas exhausted from the carbon dioxide gas cleaning means into a distillation column and rectifies it, and is contained in this used carbon dioxide gas. And a re-liquefaction step of introducing a high-purity vaporized carbon dioxide extracted from the distillation column into a condenser to liquefy the regenerated carbon dioxide after re-liquefaction, It is configured to be reused for cleaning with carbon dioxide gas cleaning means.

That is, the inventors of the present application have made extensive studies to solve the above problems, and as a result, when purifying and regenerating carbon dioxide gas (cleaning liquid) containing contaminants derived from the object to be cleaned, the following ( It has been found that the methods 1) to (3) are effective.
(1) Distillation purification is effective for removing oil and high-boiling organic substances.
(2) A filter and / or adsorbent is effective for removing particles and low-boiling organic substances.
(3) In addition, by these combinations, it is possible to purify higher purity carbon dioxide.

  The present invention has been made on the basis of the above knowledge, and the used carbon dioxide regenerating method of the present invention is used carbon dioxide exhausted from the process of cleaning an object to be cleaned using carbon dioxide. Is introduced into a distillation column and rectified, and the vaporized carbon dioxide gas extracted from the distillation column after the rectification is reliquefied using a condenser, thereby removing impurities and the like in the used carbon dioxide gas. It can be removed efficiently and with high accuracy. Therefore, the used carbon dioxide regeneration method of the present invention can effectively regenerate and utilize the carbon dioxide exhausted from the carbon dioxide cleaning means without releasing it into the atmosphere. Moreover, the method for regenerating used carbon dioxide gas of the present invention is friendly to the global environment and economically superior.

  Further, in the present invention, among them, carbon dioxide gas extracted from the distillation column is introduced into an adsorption vessel to remove impurities contained in the carbon dioxide gas, and then introduced into the condenser. In the case of liquefaction, particles, low boiling point organic substances, etc. in the used carbon dioxide gas are efficiently removed. Therefore, this used carbon dioxide regeneration method has the advantage that, in addition to the high purity obtained by distillation, there are very few particles or the like that may damage the semiconductor substrate or the like in the recycled carbon dioxide gas.

  In the present invention, among them, in particular, a heating heat exchanger, a cooling heat exchanger, a compressor, an expansion mechanism, and a heat pump composed of a working fluid are provided. Using this heat pump, distillation in the distillation step is performed. When supplying hot heat to the tower and supplying cold heat to the condenser in the reliquefaction step, the heat energy required on the distillation tower side (hot heat) and the condenser side are passed through the working fluid in the heat pump. The necessary heat energy (cold heat) is transported and exchanged with high efficiency. Therefore, the method for regenerating spent carbon dioxide gas of the present invention greatly reduces the energy and cost of the operation compared to the conventional method in which a heating source for the distillation process and a cooling source for the reliquefaction process are individually provided. Can do.

  In addition, in this used carbon dioxide regeneration method, the amount of heat required to vaporize the liquefied carbon dioxide gas (warm heat) and the amount of heat required to liquefy the vaporized carbon dioxide gas (cold heat) are approximately equal. Therefore, there is an advantage that energy (that is, running cost) added later to the heat pump cycle is very small. Moreover, since it is not necessary to install the heating source of a distillation process and the cooling source of a reliquefaction process separately, it also has the advantage that an installation can be simplified.

  Furthermore, in the present invention, among the regeneration methods using a heat pump, in particular, a flow path for circulating the working fluid of the heat pump to the evaporator and the condenser of the distillation tower is provided, and the heat exchanger for heating of the heat pump is provided. The energy required for heating the carbon dioxide gas in the distillation step and cooling the carbon dioxide gas in the reliquefaction step is obtained by combining the function of the evaporator and the heat exchanger for cooling also having the function of the condenser. When supplying directly through the working fluid of the heat pump, the following advantages arise. In other words, in this way, the heating of the liquefied carbon dioxide gas in the distillation step and the cooling of the vaporized carbon dioxide gas in the reliquefaction step are performed by the working fluid of the heat pump without using a secondary heat medium or heat storage means. It is done directly. Therefore, this used carbon dioxide regeneration method can further reduce the loss of thermal energy and purify and regenerate carbon dioxide with high thermal efficiency.

  The “heat pump” in the present application is composed of a heat exchanger for heating, a heat exchanger for cooling, a compressor, an expansion mechanism, a flow path for circulating these, and a working fluid filled in the flow path. The low temperature generated by the expansion of the working fluid that occurs when the other liquid or gas that passes through the heating heat exchanger is heated by the high temperature working fluid that is generated by compression by the compressor and passes through the expansion mechanism. This is a general term for a system, a circuit, or a cycle itself for cooling other liquid or gas passing through the cooling heat exchanger by the working fluid. Therefore, it includes vapor compression heat pumps and gas liquefaction heat pumps that transport thermal energy within the system by working fluid, but does not include so-called chemical heat pumps such as absorption heat pumps and adsorption heat pumps that use exothermic and endothermic reactions. . The “expansion mechanism” referred to here indicates an “expansion valve” or an “orifice”.

It is a flowchart which shows 1st Embodiment of the carbon dioxide regeneration apparatus used for the reproduction | regeneration method of the used carbon dioxide of this invention. It is a flowchart which shows 2nd Embodiment of the carbon dioxide regeneration apparatus used for the regeneration method of the used carbon dioxide of this invention. It is a flowchart which shows 3rd Embodiment of the carbon dioxide regeneration apparatus used for the reproduction | regeneration method of the used carbon dioxide of this invention.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this embodiment.

  FIG. 1 is a flowchart for explaining a schematic configuration of a carbon dioxide regenerator used in the method for regenerating used carbon dioxide in the first embodiment of the present invention.

  Here, the block on the right side of the alternate long and short dash line in FIG. 1 is a cleaning process for supplying the used carbon dioxide gas containing contaminants (after cleaning the object to be cleaned) to the carbon dioxide regeneration device of the present embodiment ( The reference numeral 21 in the figure is a cleaning liquid tank for storing high-purity liquefied carbon dioxide gas, 22 is a cleaning tank for cleaning an object to be cleaned, and 23 is a used after cleaning. A trap for removing foreign matter from carbon dioxide, 24 is a recovery tank for storing used carbon dioxide after cleaning, 25 is a pump for pumping used carbon dioxide from the recovery tank 24, and 26 is exhausted from the cleaning tank 22 A compressor 27 for compressing and recovering the recovered gas, and 27, a reservoir tank for replenishing high-purity unused liquefied carbon dioxide gas.

  Further, in the cleaning step depicted by a two-dot chain line in FIG. 1, an object to be cleaned (for example, a semiconductor wafer) is accommodated in the cleaning tank 22 and sealed, and then the cleaning tank 22 is filled with the cleaning liquid tank 21. By supplying liquefied carbon dioxide gas (cleaning liquid) and spraying the liquefied carbon dioxide gas onto the object to be cleaned in the cleaning tank 22, contaminants such as oil and particles adhering to the object to be cleaned are removed. The carbon dioxide gas used for cleaning is collected separately in a liquid phase and a gas phase. That is, the liquid phase (liquefied carbon dioxide gas) in the cleaning tank 22 is exhausted from the flow path below the cleaning tank 22, and foreign substances and the like are removed by the trap 23 and then stored in the recovery tank 24. Further, the gas phase (vaporized carbon dioxide gas) remaining in the upper portion of the cleaning tank 22 is introduced into the compressor 26 from the exhaust port, compressed by the compressor 26, and similarly stored in the recovery tank 24.

  As shown by the solid line portion in FIG. 1, the carbon dioxide regenerator in this embodiment is a distillation column 1 that rectifies used carbon dioxide exhausted from the carbon dioxide gas cleaning means, and is extracted from the distillation column 1. A condenser 3 for liquefying the vaporized carbon dioxide gas, an adsorption cylinder 2 (adsorption vessel) disposed between the distillation column 1 and the condenser 3, and heating for supplying warm heat to the evaporator 4 of the distillation column 1 A source 6, a cooling source 7 for supplying cold heat to the condenser 3, and a flow path (pipe, etc.) connecting these to each other are configured.

  The distillation column 1 is provided with an evaporator and a rectifying shelf disposed therein, and used carbonic acid introduced into the evaporator using warm heat (hot water or the like) supplied from a heating source 6 described later. It is for rectifying gas. Below the distillation column 1, an evaporator 4 having a heating coil is disposed, and a plurality of shelves (rectifying shelves) or regular packings (packing) are disposed above the evaporator 4. A flow path for supplying vaporized carbon dioxide gas to the adsorption cylinder 2 extends upward at the upper part of the distillation column 1, and the lowermost part does not evaporate in the evaporator and is concentrated as a liquid phase. A pipe or the like is provided for exhausting the impurities and the like out of the system as waste liquid. In the upper part of the distillation column 1, there is a flow path for refluxing a part of the high-purity liquefied carbon dioxide gas reliquefied by the condenser 3 as a reflux liquid above the shelf in the distillation column 1. It is connected.

  The condenser 3 is for liquefying the high-purity vaporized carbon dioxide gas generated by evaporation in the distillation tower 1 using cold heat (cold water or the like) supplied from a cooling source 7 described later. On the side, the regenerated liquefied carbon dioxide is supplied (returned) to the cleaning liquid tank 21 in the cleaning step, and a part of the liquefied carbon dioxide is supplied to the rectifying shelf of the distillation column 1 described above. A flow path for refluxing upward is provided.

  The adsorption cylinder 2 disposed between the distillation column 1 and the condenser 3 contains a filter, an adsorbent, or the like inside, and introduces carbon dioxide gas in a gaseous state generated in the distillation column 1.・ It is designed to pass through. In addition, since this adsorption cylinder 2 may not be used depending on the object to be cleaned, a flow path (bypass line) that bypasses this and supplies carbon dioxide vaporized in the distillation column 1 to the condenser 3 is provided. Yes.

  Examples of the adsorbent accommodated in the adsorption cylinder 2 include activated carbon, alumina, silica gel, molecular sieve, and the like, and one or a combination of these is used. And as for the filter accommodated in the said adsorption | suction cylinder 2, although a mesh size is selected according to the request | requirement of the washing | cleaning target object, generally an in-line filter of about 1 micrometer is used. In addition, the filter of another mesh size may be used for a filter, Furthermore, you may use these adsorbents and a filter together.

  And as the heating source 6 which supplies warm heat to the evaporator 4 (heating coil) of the distillation column 1, various heat sources which can heat liquefied carbon dioxide gas other than a heater, a boiler, etc. can be used. As the cooling source 7 for supplying cold heat to the cooling coil 5 of the condenser 3, various heat sources capable of cooling the vaporized carbon dioxide gas can be used in addition to the cold water production apparatus and the air outside the apparatus (atmosphere). .

  In the regeneration of the used carbon dioxide gas using the carbon dioxide gas regenerating apparatus having the above-described configuration, first, the used carbon dioxide gas stored in the recovery tank 24 of the cleaning step is put into the evaporator of the distillation column 1 using the pump 25. Introduce.

  And the heating coil of the evaporator 4 is heated with the warm heat supplied from the heating source 6, and the liquefied carbon dioxide gas in the said evaporator is evaporated. At this time, in the lower part of the distillation column 1, the used liquefied carbon dioxide gas evaporates while leaving the oil and high-boiling organic substances derived from the object to be cleaned in the liquid phase. Is removed.

  In addition, a flow path for refluxing a part of the high-purity liquefied carbon dioxide gas from the condenser 3 is connected to the upper part of the distillation tower 1. The liquefied carbon dioxide gas (reflux) and the carbon dioxide gas vaporized by the evaporator 4 are brought into countercurrent contact, and the vaporized carbon dioxide gas is further purified.

  Next, the carbon dioxide gas in a gaseous state having a high purity by removing high-boiling organic substances is introduced into the adsorption cylinder 2 and cannot be completely removed by the distillation column 1 by a filter, an adsorbent or the like housed therein. Particles and low boiling point organic substances are filtered and adsorbed.

  Thereafter, the vaporized carbon dioxide gas having high purity and containing no particles or the like is introduced into the condenser 3 and is cooled and liquefied by the cooling coil 5 of the condenser 3. Most of the liquefied carbon dioxide gas is stored in the cleaning liquid tank 21 in the cleaning step and reused for cleaning the object to be cleaned.

  As described above, the method for regenerating used carbon dioxide gas in the present embodiment can efficiently remove impurities and the like in the used carbon dioxide gas by combining the distillation column 1 and the condenser 3. Therefore, the used carbon dioxide regeneration method of the present embodiment can effectively utilize the carbon dioxide exhausted from the carbon dioxide cleaning means without releasing it into the atmosphere.

  Moreover, according to this carbon dioxide regeneration method, particles, low-boiling organic substances, etc. in the used carbon dioxide are removed with high accuracy. Therefore, the regenerated carbon dioxide gas obtained by the regenerating method of the present embodiment has a very small amount of particles or the like that may damage oil or a semiconductor substrate in the regenerated carbon dioxide gas in addition to the high purity obtained by distillation. It can be suitably reused in the cleaning process for substrates and the like.

Next, a second embodiment of the present invention will be described.
FIG. 2 is a flowchart illustrating a schematic configuration of a carbon dioxide regenerator used in the method for regenerating used carbon dioxide in the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the structural member which has the same function as 1st Embodiment, and the detailed description is abbreviate | omitted.

  The feature of the carbon dioxide regenerator in the present embodiment is that, instead of the heating source 6 and the cooling source 7 in the first embodiment, the heat necessary for the distillation tower 1 in the upper distillation step and the condenser 3 in the reliquefaction step. The heat pump which supplies required cold heat is arrange | positioned. Further, a heat medium circulation passage H for circulating a heat medium (hot water in the present embodiment) different from the working fluid used in the heat pump is provided between the heat pump and the distillation tower 1. At the same time, a refrigerant circulation channel C is provided between the heat pump and the condenser 3 for circulating a refrigerant (cold water in the present embodiment) different from the working fluid.

  The heat pump circulates in the order of the compressor 10-the heat exchanger 12 for heating-the heat exchanger 14 for expansion temperature adjustment-the expansion valve 11-the heat exchanger 13 for cooling-the heat exchanger 15 for compression temperature adjustment. It consists of a path (pipe) and a working fluid filled in the flow path, and moves and exchanges heat between the heating heat exchanger 12 and the cooling heat exchanger 13. The heat pump cycle (circuit) which can be formed is formed.

  Further, in the present embodiment, water is used as the heat medium in the heat medium circulation channel H and the refrigerant in the refrigerant circulation channel C, and the heating heat exchanger 12 of the heat pump is transferred to the evaporator 4 of the distillation tower 1. On the other hand, hot water as a heat medium is supplied. And the cold water as a refrigerant | coolant is supplied with respect to the condenser 3 from the heat exchanger 13 for cooling of the said heat pump, the heating in the said evaporator 4 and the cooling in the condenser 3 are via these warm water and cold water. The necessary heat is supplied.

  In FIG. 2, reference numeral 16 in the drawing denotes a hot water tank that stores hot water, and reference numeral 17 denotes a cold water tank that stores cold water. Moreover, the code | symbol P in a figure is a pump for circulating these hot water and cold water.

  Also with the above configuration, the method for regenerating used carbon dioxide gas of the present embodiment can be effectively used without releasing the carbon dioxide gas exhausted from the carbon dioxide gas cleaning means into the atmosphere. Further, the regenerated carbon dioxide obtained by the regenerating method of the present embodiment has not only high purity by distillation, but also the regenerated carbon dioxide gas has very few particles that may damage oils, semiconductor substrates, etc. It can be suitably reused in the cleaning process for substrates and the like.

  Moreover, the carbon dioxide regenerator in the present embodiment has high heat energy (hot heat) required in the distillation tower 1 and high heat energy (cold heat) required in the condenser 3 through the working fluid in the heat pump. Transported and exchanged with efficiency. Therefore, the used carbon dioxide regeneration method using the heat pump reduces the energy and cost of the operation compared to the conventional regeneration method in which the heating source in the distillation process and the cooling source in the reliquefaction process are individually provided. It becomes possible.

Next, a third embodiment of the present invention will be described.
FIG. 3 is a flowchart for explaining a schematic configuration of a carbon dioxide regenerator used in the method for regenerating used carbon dioxide in the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the structural member which has the function similar to 1st, 2nd embodiment, and the detailed description is abbreviate | omitted.

  The carbon dioxide gas regenerating apparatus in the present embodiment is different from the second embodiment in that a flow path for circulating the working fluid of the heat pump to the evaporator 4 and the condenser 3 of the distillation tower 1 is formed. The heat exchanger 12 for heating the heat pump also serves as the heating coil for the evaporator 4, and the heat exchanger 13 for cooling the heat pump serves as the cooling coil for the condenser 3 (reference numeral 5 in FIGS. 1 and 2). It is the point arrange | positioned so that it may be combined.

  Even with the above configuration, the method for regenerating used carbon dioxide gas in this embodiment releases carbon dioxide gas exhausted from the carbon dioxide gas cleaning means into the atmosphere, as in the first and second embodiments described above. And can be used effectively. Further, the regenerated carbon dioxide obtained by the regenerating method of the present embodiment has not only high purity by distillation, but also the regenerated carbon dioxide gas has very few particles that may damage oils, semiconductor substrates, etc. It can be suitably reused in the cleaning process for substrates and the like.

  Further, the carbon dioxide regenerator in the present embodiment includes a heating heat exchanger 12 that directly supplies warm heat to the evaporator 4 in the distillation process, and a cooling heat exchanger that directly supplies cold heat to the condenser 3 in the reliquefaction process. 13 are arranged in one heat pump cycle, and therefore, through the working fluid in the heat pump, the heat energy required on the evaporator 4 side (heat) and the heat energy required on the condenser 3 side are provided. (Cold heat) is directly transported and exchanged.

  Moreover, in the carbon dioxide regenerator, the amount of heat necessary for vaporizing the liquefied carbon dioxide gas in the distillation column 1 (hot heat) and the amount of heat necessary for liquefying the vaporized carbon dioxide gas with the condenser 3 (cold heat). Has the advantage that they are almost equal.

  Therefore, the regeneration method of the used carbon dioxide gas in this embodiment greatly reduces the energy consumption and cost for the operation compared with the conventional regeneration method in which the heating source in the distillation process and the cooling source in the reliquefaction process are individually provided. Can be reduced. Moreover, it can be a carbon dioxide regeneration method that is friendly to the earth in terms of both environment and energy.

  Further, the carbon dioxide regenerator in the present embodiment has an advantage that the equipment can be simplified because it is not necessary to separately provide a heating source for the distillation process and a cooling source for the reliquefaction process.

  In the above three embodiments, the method of regenerating used carbon dioxide exhausted from a dry cleaning device for precision cleaning of a semiconductor wafer or the like has been described as an example. However, the present invention is a carbon dioxide cleaning device having other configurations. Needless to say, the present invention can be applied to used carbon dioxide exhausted from the factory.

  In addition to a carbon dioxide gas cleaning device with multiple cleaning processes, as well as a rinse process and a finishing process, in addition to a device that repeatedly uses liquefied carbon dioxide gas in a cleaning tank during one batch, and a batch type cleaning device, You may apply to the continuous washing | cleaning apparatus etc. which wash | clean to-be-cleaned object continuously.

  The present invention relates to carbon dioxide using a high-pressure liquefied carbon dioxide as a cleaning liquid for dry cleaning of cloth products such as clothing and bedding, cleaning of semiconductor substrates in semiconductor manufacturing processes, removal of unnecessary materials from electrical / electronic components and optical members, etc. The present invention can be widely applied to a method of purifying carbon dioxide gas by removing contaminants and unnecessary substances from used carbon dioxide gas exhausted from the gas scrubber and reusing it as a cleaning liquid for the carbon dioxide scrubber.

1 Distillation tower 2 Adsorption cylinder 3 Condenser 4 Evaporator

Claims (4)

  A distillation process for removing the impurities contained in the used carbon dioxide gas by rectifying by introducing the used carbon dioxide gas exhausted from the carbon dioxide cleaning means into the distillation tower, and high purity vaporization extracted from the distillation tower. A re-liquefaction step of introducing carbon dioxide into a condenser and liquefying, and the regenerated carbon dioxide after re-liquefaction is reused for washing in the carbon dioxide washing means. How to play.   The spent carbon dioxide gas according to claim 1, wherein the vaporized carbon dioxide gas extracted from the distillation tower is introduced into an adsorption vessel to adsorb and remove impurities contained in the carbon dioxide gas, and then introduced into the condenser to be liquefied. Playback method.   A heat pump comprising a heat exchanger for heating, a heat exchanger for cooling, a compressor, an expansion mechanism, and a working fluid, and using this heat pump, heat is supplied to the distillation tower in the distillation step, and in the reliquefaction step The method for regenerating used carbon dioxide gas according to claim 1 or 2, wherein cold heat is supplied to the condenser.   A flow path for circulating the working fluid of the heat pump to the evaporator and the condenser of the distillation tower is provided, the heating heat exchanger of the heat pump also serves as the evaporator, and the cooling heat exchanger The spent of Claim 3 which supplies the energy required for the heating of the carbon dioxide gas in the said distillation process, and the cooling of the carbon dioxide gas in the said reliquefaction process directly through the working fluid of the said heat pump, combining the function of a condenser. Carbon dioxide regeneration method.

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