JP3640023B2 - Emission CO2 recovery system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses low-temperature exhaust heat of about 100 to 200 ° C. of exhaust gas discharged from establishments such as thermal power plants, incineration facilities, factories, etc., and generates cold heat through a chemical heat pump, and the cold heat and exhaust heat. A low-concentration CO ₂ adsorption separation process in which a composite process is formed by
Exhaust CO comprising a CO ₂ supercritical refrigeration cycle that forms a low-temperature cold heat source with a low-temperature medium having a temperature substantially equal to the temperature of liquefied CO ₂ , dry ice, or low-pressure CO ₂ below the triple point from adsorbed and separated CO _{2 This} relates to the _second recovery system.
[0002]
[Prior art]
Natural refrigerants are expected from the regulation of fluorocarbon refrigerants for protection of the global environment, and in particular, the presence of CO ₂ having an ozone depletion coefficient of zero and a global warming coefficient of 1 is drawing attention.
In other words, regarding global warming, the development of a refrigerant with a low global warming potential is strongly demanded from the viewpoint of global warming as compared with the fluorocarbon refrigerant having a global warming potential several thousand times that of CO _2. It is expected that CO ₂ that exists in large quantities in nature instead of the refrigerant will be used as the refrigerant.
On the other hand, CO ₂ is recognized as a medium for storing and transporting cold energy with high-density energy, and its use is diversified. For its recovery, it is required to increase the rate of the low-concentration CO ₂ recovery process. In addition, there is a strong demand from the viewpoint of further application to industrial sectors such as consumer and transportation, as well as contributing to the construction of energy-saving systems.
[0003]
In other words, while aiming to effectively use low-temperature exhaust heat that has been in the disposable state of around 100-200 ° C, which is discharged from business sites such as thermal power plants, incineration facilities, and factories, global environmental problems, especially global warming From the standpoint of prevention, there is a strong demand for the reduction and recovery of atmospheric CO ₂ emissions and the effective use of refrigerant in the refrigeration cycle of recovered CO ₂ .
[0004]
A pressure swing adsorption type (PTS) is used for the separation and recovery of the CO _{2 from} the combustion exhaust gas. The PTS is a process in which a pressurized raw material gas is passed through an adsorbing substance such as zeolite to adsorb and separate impurities to obtain a target gas having a required purity. The adsorbed impurity gas is released and removed at atmospheric pressure or vacuum pressure. Yes.
For example, recovery by PTS method using synthetic zeolite is used for separation and recovery of CO _{2 having} a higher concentration than blast furnace hot stove exhaust gas.
Incidentally, the CO ₂ in a higher concentration than the normal flue gas in this case as a raw material, further the CO ₂ with employing the price competitiveness of the vacuum desorption PTS method using a high separation efficiency synthetic zeolite as above Although recovery is possible, the power cost required for the adsorption separation requires energy equivalent to the power cost for obtaining the liquefied CO ₂ after separation, and reduction of the power cost required for the adsorption separation is desired.
In the case of PTS separation using activated carbon or synthetic zeolite as an adsorbent, moisture in the raw material gas is an adsorbing component and inhibits CO ₂ adsorption. Therefore, it is necessary to dehumidify the source gas as a pretreatment, and a dehumidification process using exhaust heat is also required.
[0005]
When the recovered CO ₂ is used as a refrigerant in a refrigerator, since the critical point of CO ₂ is low, the above refrigeration cycle forms a cycle including a supercritical region exceeding the critical point, and the condensation process is performed at a high temperature. In order to determine the sensible heat change, it is necessary to cool the heat efficiently. The cold heat is obtained by a chemical heat pump driven by exhaust heat extracted from the exhaust gas in the system together with the CO _2. There is a demand for the production of a high-density energy medium and the formation of a versatile heat supply system that can function sufficiently as a CO ₂ supercritical refrigeration cycle by using cold heat.
[0006]
There have been various proposals for recovering CO ₂ from the above-described combustion exhaust gas and recovering it as gaseous, liquid or solid dry ice.
Japanese Laid-Open Patent Publication No. 2000-24454 discloses a proposal “Method and apparatus for treating flue gas”.
The schematic configuration of the proposal will be described below with reference to FIG.
This apparatus relates to a combustion exhaust gas treatment method and apparatus for separating and recovering carbon dioxide in combustion exhaust gas after solidifying it as dry ice using LNG cold heat.
[0007]
The structure is composed of a moisture aggregating means 62 for aggregating moisture by cooling the moisture in the combustion exhaust gas 61 discharged from the boiler 60, and cooling the residual moisture in the combustion exhaust gas at a low temperature of −30 ° C. or lower to make the ice 63a. Solid-gas separation for separating the solidifying ice solidifying device 63, the carbon dioxide solidifying device 64, the carbon dioxide gas (dry ice) 65 in the combustion exhaust gas 61 from which moisture has been completely removed, and the exhaust gas 66 containing no low-temperature carbon dioxide gas. A unit 67, a carbon dioxide gas liquefying device 68 for pressurizing and liquefying the separated dry ice 65, a liquefied carbon dioxide storage tank 70 for storing liquefied carbon dioxide 69, and liquefying the LNG to obtain cold heat (not shown) It consists of a heat exchanger.
[0008]
The above proposal is to effectively use the heat of vaporization of the LNG as a cold heat, solidified or separated moisture in the combustion exhaust gas as ice, and further solidified or liquefied the carbon dioxide gas in the combustion exhaust gas as dry ice. However, the use of fuel having such a large heat of vaporization is limited to a specific case, and there is a problem that cannot be applied when using general city gas.
[0009]
On the other hand, as for the CO ₂ liquefaction apparatus, Japanese Patent Laid-Open No. 10-59706 discloses a proposal relating to a high-yield CO ₂ liquefaction apparatus that hardly releases CO ₂ as a raw material to the outside. The proposal is shown in FIG.
The low-pressure gas line 83 from the gas holder 81 storing CO ₂ is connected to the low-pressure side suction port 84a of the carbon dioxide gas compressor 84 composed of a two-stage compressor through a water washing cylinder 82 that removes impurities in the carbon dioxide gas. The low pressure side discharge port 84b of the compressor 84 is connected to the high pressure side suction port 84c of the compressor via the deodorizing device 85 by the medium pressure gas line 86, and the discharge port 84d is connected to the dehumidifier 88 by the high pressure gas line 87. And connected to a carbon dioxide gas inlet 89 a of the cooling device 89.
[0010]
The cooling device 89 cools CO ₂ from the high-pressure gas line 87 to condense and liquefy it. For example, the refrigerant sent into the refrigerant coil 89c in the cooling device 89 from a refrigerator (not shown) condenses and liquefies carbon dioxide gas. doing.
Supply line 93 of the liquefied CO ₂ and the other end of the liquefied CO ₂ high-pressure liquid line 90 having one end connected to the outlet 89b is at the bottom of the vacuum insulated tank 91 for storing liquefied CO ₂ with the opening and closing valve 92 of the cooling device 89 One end is connected.
The other end of the return gas line 94 whose one end faces the gas phase portion in the vacuum heat insulation tank 91 is connected to an intermediate pressure gas line 86 between the low pressure side discharge port 84 b of the compressor 84 and the deodorizing device 85.
With the above configuration, CO ₂ compressed by the compressor 84 is condensed and liquefied by the cooling device 89 to be liquefied CO ₂ , and is sent to the vacuum heat insulation tank 91 and stored.
When liquefied CO ₂ is sent into the tank and the gas phase pressure in the tank exceeds a predetermined value, CO ₂ is returned to the suction side of the compressor via a return gas line by a signal from the pressure regulator 96, Eliminate waste.
[0011]
Further, in the conventional dry ice production process including liquefaction of CO ₂ , as shown in FIG. 7, the washing treatment by the washing tower 101 and the desulfurization treatment by the desulfurizer 102 performed before the compression by the compressor 100 of carbon dioxide gas, after the compression The purification process performed by the purification tower 103 and the dehumidification process performed by the dehumidifier 104 are required (some of which are also found in the above proposal). After these processes, the high-pressure high-temperature CO ₂ is supplied to the ice cooler 105, CO _A supercooled supercritical CO ₂ is formed by the _two cooler 106 and the supercooler 107, and after storing a high density supercritical gas close to the supercritical CO ₂ liquid in the CO ₂ liquefaction tank 108, the pressure reducing valve 109 The dry ice press machine 110 is used to generate dry ice at about −78.5 ° C., and the low-temperature CO ₂ generated during the decompression is passed through the process. The configuration is such that the compressor 100 is refluxed through the heat exchanger of the cooler 107.
In the conventional dry ice production system, since the raw material is a crude gas, the equipment costs of the washing tower 101, the desulfurizer 102, the purification tower 103, and the dehumidifier 104 are required before and after compression as described above, and the raw material It is a low yield of 39.4% with respect to the CO ₂ crude gas 111.
Therefore, there is a demand for realizing a high-yield dry ice production method with high energy saving and an apparatus therefor while keeping the facility cost low.
[0012]
Further, by CO ₂ refrigeration cycle using recovered CO ₂ as the refrigerant, for versatile system for supplying a high-density energy medium, there is a heat storage system having the following constitutions.
The system includes a supercritical CO ₂ cycle using CO ₂ as a refrigerant, an air-cooled refrigerator unit forming a gas cooler of the cycle, and a pressure of about 9.2 Kg / cm ² , a temperature by a pre-stage expansion means of the supercritical refrigeration cycle. A liquefied CO ₂ generator that obtains low-pressure liquefied CO ₂ at −40 ° C. and an evaporator that lowers the liquefied CO ₂ to near the triple point pressure by means of subsequent expansion means, and a heat exchanger provided in the evaporator Then, cold heat is supplied through indirect contact to obtain a low-temperature refrigerant liquid R22 of about −40 ° C., and evaporative gas is recirculated from the evaporator.
In this case, since there is a problem of solidification due to a temperature drop below the triple point of liquefied CO ₂ , the pressure drop is kept near the triple point and dry ice is not used, so the cooling temperature is also above the triple point temperature of −56.6 ° C. The temperature of the heat transfer medium on the load side cannot be cooled below -40 ° C.
[0013]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems,
By using low-temperature exhaust heat of about 100 to 200 ° C. discharged from establishments such as thermal power plants, incineration facilities, factories, etc., by generating cold heat through a chemical heat pump and combining the cold heat and the exhaust heat An adsorption separation process of low-concentration CO ₂ at a high rate;
Versatile CO ₂ refrigeration such as to provide a low-temperature cold generating and below the triple point of the liquefied CO ₂ dry ice generation and liquefaction CO ₂ or dry ice, etc. The density of the energy medium using a CO ₂ adsorbed separated as a refrigerant The purpose is to provide an exhaust CO ₂ recovery system that forms a cycle.
[0014]
[Means for Solving the Problems]
Therefore, the exhaust CO ₂ recovery system of the present invention is
Exhaust CO that uses low-temperature exhaust heat around 100 to 200 ° C of exhaust gas discharged from establishments such as thermal power plants, incineration facilities, and factories, and cold heat obtained from chemical heat pumps that operate using the exhaust heat _In the recovery system of No. 2, first means for performing recovery of low concentration CO ₂ discharged together with the exhaust gas by deformation pressure swing adsorption,
The recovered CO ₂ is used as a refrigerant for a CO ₂ supercritical refrigeration cycle equipped with a liquefier that operates by cold, and liquefied CO ₂ is formed in the front stage of the multi-stage expansion means, and below the triple point by the subsequent stage expansion means. And a cold heat generating means (second means) for forming a low-temperature cold heat.
[0015]
The above-mentioned present invention is based on the low-temperature exhaust heat in the recovery of low-concentration CO ₂ discharged together with exhaust gas in a low-temperature exhaust heat system of about 100 to 200 ° C. discharged from establishments such as thermal power plants, incineration facilities, and factories. Chilled heat is generated through a chemical heat pump such as an adsorption heat pump, and the recovery of the low-concentration CO ₂ is performed by pressure swing adsorption (PTS) using an adsorption separation means that takes into account the generated cold heat and adsorption promotion and desorption promotion means by the exhaust heat. ) Efficiently by deformed adsorption / desorption,
The recovered low-concentration CO ₂ is used as a refrigerant for the refrigeration cycle, and cold heat formed by the chemical heat pump is introduced into a liquefier (gas cooler) provided downstream of the compressor, and CO ₂ formed by the refrigeration cycle. by absorbing the sensible heat of the supercritical gas, to obtain a liquefied CO ₂ by the pressure drop to just before the triple point by adiabatic expansion means in a plurality of stages provided on the downstream side, and then the formation of the liquified CO _2, the downstream Exhaust CO ₂ that provides low-temperature cold heat that forms a low-temperature cold heat source by dry ice or its sublimation heat by a pressure drop below the triple point pressure by the expansion means of the present invention, and enables the supply of versatile cold heat that is the object of the present invention A collection system is proposed.
[0016]
That is, by using the low-temperature exhaust heat generated in the low-temperature exhaust heat system according to the above invention, the combined use of the low-temperature CO ₂ formed by the exhaust heat and the exhaust heat from the exhaust gas discharged together with the exhaust heat. by efficiently collecting, using the recovered CO ₂ ozone depletion of the refrigeration cycle, as the refrigerant to solve global warming and the like, the high pressure side of the supercritical by CO ₂ used by cold formed by the low-temperature waste heat A high-efficiency versatile heat supply system for recovered CO ₂ is formed, such as liquefied CO ₂ , dry ice, or a low-temperature cold-heat source that can be cycled is formed by a plurality of stages of expansion means.
[0017]
In the exhaust CO ₂ recovery system of the present invention, a configuration in which dry ice is generated by low-temperature cold heat is preferable.
[0018]
Alternatively, the low-temperature cold heat formation preferably has a configuration in which a refrigeration cycle is provided with formation of a low-temperature medium that operates at a low-pressure CO ₂ temperature below the triple point by directly injecting liquefied CO ₂ that has been depressurized below the triple point into the antifreeze. Cycle formation of low-temperature cooling to -78.9 ° C corresponding to a pressure drop below the triple point from a low-temperature medium, even for low-temperature cooling below -56.6 ° C below the triple point, which was impossible in the past It is possible to obtain a variety of materials other than dry ice in the supply of low-temperature cold heat.
[0019]
In addition, the low-temperature cold heat formation is preferably generated by a low-temperature medium formed by direct injection of low-pressure CO ₂ whose pressure is lowered below the triple point into the antifreeze.
In other words, liquefied CO ₂ begins to solidify due to a pressure drop below the triple point and shifts to the formation process of dry ice. If low pressure CO ₂ below the triple point is injected into the antifreeze solution, direct propagation of sublimation heat occurs. The antifreeze is cooled to form a low-temperature medium up to about −79 ° C., which is equal to the temperature of CO ₂ whose pressure has dropped, and the vaporized low-temperature CO ₂ is refluxed to the suction side of the low-stage compressor of the refrigeration cycle. Form.
Note that the evaporated gas of the antifreeze liquid is mixed in the vaporized CO ₂ refluxed by the direct contact, but the mixed gas is condensed and removed in a later step of the cycle.
In addition, CO ₂ is mixed in the antifreeze forming the low-temperature medium. However, the heat conductivity of the antifreeze having a low heat conductivity is improved by the mixing, which has an advantage of enabling efficient heat exchange.
[0020]
Further, in the exhaust CO ₂ recovery system of the present invention, the deformation pressure swing adsorption means as the first means is an adsorption promotion means using the cold formed by the exhaust heat and a desorption promotion using the exhaust heat. It is preferable to add temperature swing adsorption (TSA) comprising means to pressure swing adsorption (PTS).
[0021]
In other words, adsorption separation is performed by vacuum swing type pressure swing adsorption (PTS) using polymer synthesized zeolite, and temperature swing adsorption (TSA) comprising adsorption promotion means by cold heat and desorption promotion means by heating (utilizing exhaust heat). ) With a high temperature and pressure PTSA method, which enables highly efficient recovery of low concentration CO ₂ .
In addition, the cooling heat used for the said adsorption | stimulation promotion means is set as the structure which uses what was produced | generated via the chemical heat pump from the low-temperature waste heat of about 100-200 degreeC discharged | emitted in the system.
The pressure swing adsorption (PTS) is provided with a pusher into the adsorbent, a vacuum pump for removing impurities adsorbed from the adsorbent and a plurality of adsorbers, and the adsorbent such as zeolite incorporated in the adsorber. Impurities are adsorbed and separated from the pressurized source gas pressurized by the pusher, and the adsorbed and separated impurities are separated from the vacuum by a vacuum pump.
[0022]
In the exhaust CO ₂ recovery system of the present invention,
The CO ₂ supercritical refrigeration cycle by the second means is constituted by a two-stage compression and two-stage expansion refrigeration cycle, and the first stage adiabatic expansion means forms liquefied CO ₂ by a pressure drop before the triple point, It is preferable to form dry ice or a low-temperature cold heat source by a pressure drop below the triple point by the second stage adiabatic expansion means.
[0023]
In other words, the refrigeration cycle in the present invention is constituted by a two-stage compression and two-stage expansion refrigeration cycle, and the entire amount of the high-pressure side refrigerant is reduced to a pressure just before the triple point, which is an intermediate pressure, by the preceding stage expansion means. The intermediate pressure liquid at the bottom of the vessel is depressurized by the expansion means at the subsequent stage and flows into the evaporator.
Liquefied CO ₂ is formed in the previous stage of expansion, and the pressure is reduced to below the triple point pressure in the subsequent stage of expansion, and dry ice or a low-temperature cold heat source is formed in the dry ice press machine or the evaporator.
[0024]
In other words, the antifreeze is filled in an evaporator provided downstream of the subsequent expansion means, and is in a solidification process formed by reducing the pressure to a pressure below the triple point through the expansion means in the antifreeze. Low temperature and low pressure CO ₂ is introduced to form a low temperature medium by direct contact.
Therefore, the low-temperature medium in the evaporator is cooled by the sublimation heat by CO ₂ that has been lowered below the injected triple point pressure to form a low-temperature heat source up to about −79 ° C.
The injected CO ₂ is vaporized and refluxed to the low-stage compressor to form a cycle.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, as long as there is no specific description, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention. .
FIG. 1 is a block diagram showing a schematic configuration of the exhaust CO ₂ recovery system of the present invention, FIG. 2 is a diagram showing a schematic configuration of temperature-pressure swing adsorption (PTSA) in FIG. 1, and FIG. FIG. 4 is a block diagram showing the ice production process, and FIG. 4 is a Mollier diagram of the CO ₂ supercritical refrigeration cycle of FIG.
[0026]
As shown in FIG. 1, the exhaust CO ₂ recovery system of the present invention is
CO ₂ supercritical that targets low-temperature exhaust gas discharged from establishments such as thermal power plants, incineration facilities, and factories, recovers low-concentration CO ₂ contained in the exhaust heat, and drives the recovered CO ₂ recovered as a refrigerant A multi-purpose cooling system that supplies liquefied CO ₂ , dry ice or low-temperature cooling through a refrigeration cycle,
The schematic configuration includes an exhaust heat driven chemical heat pump 31 that generates cold from the low temperature exhaust heat 30, and a temperature pressure swing adsorption (PTSA) 20 that is an adsorption separation means for performing low concentration CO ₂ recovery separation contained in the low temperature exhaust gas. When, more configuration recovered _CO 2 26 with CO ₂ supercritical refrigeration cycle 11 for driving as a refrigerant.
[0027]
That is, the low-temperature exhaust heat 30 having a temperature of about 100 to 200 ° C. discharged by the low-temperature exhaust gas exhaust system is supplied to a chemical heat pump 31 including an adsorption heat pump that can be driven by the low-temperature exhaust heat. A cold heat 31a of 0 ° C. is formed.
Cold 31a formed by the above, the temperature pressure swing adsorption, as shown in FIG. (PTSA) while supplied with the low-temperature exhaust heat 30 to 20, the sensible heat of the CO ₂ supercritical region of CO ₂ supercritical refrigeration cycle 11 It is configured to supply for cooling.
[0028]
The temperature-pressure swing adsorption (PTSA) 20 is an apparatus for recovering low-concentration CO ₂ contained in the low-temperature exhaust gas 25 by adsorption separation. As shown in FIG. 2, it swings between adsorption 21a and desorption 21b and incorporates zeolite. An adsorption / desorption mechanism 21 for adsorbing impurities in exhaust gas to an adsorbent such as, or desorbing the adsorbed impurities;
The adsorbent 21a of the adsorption / desorption mechanism 21 supplies an exhaust gas 25a containing low-concentration CO ₂ to the adsorbent and pressurizes the adsorbent by a blower 22a, and the adsorbent 21a of the adsorption / desorption mechanism 21 generates cold heat 31a. An adsorption promoting part 23a for promoting adsorption by supplying,
A desorption promoting portion 23b for supplying and heating the low-temperature exhaust heat 30 to promote desorption in the desorption 21b of the adsorption / desorption mechanism 21;
Sending of the recovery CO 2 ₂₆ for delivering the CO ₂ that said impurities through the vacuum withdrawal portion 24a from the heated desorption promoted adsorbent by the exhaust heat separated and recovered with is vacuum leaving the desorption 21b of the adsorption-desorption mechanism 21 24.
[0029]
With the above configuration, press-fitting with a conventional blower and detachment with a vacuum are alternately performed, and at the time of adsorption of pressure swing adsorption (PTS), the adsorption is accelerated by the cold heat 31a through the adsorption promoting portion 23a, and the efficiency is enhanced.
At the time of desorption, in addition to the separation by the vacuum, the desorption is promoted by the low-temperature exhaust heat 30 through the desorption promoting portion 23b, and the efficiency is increased
This is a combination of conventional pressure swing adsorption (PTS) and temperature swing adsorption (TSA) by cold heat and exhaust heat, separating low concentration CO ₂ with high efficiency and obtaining recovered CO ₂ 26 from the exhaust gas 25a. Yes.
[0030]
As shown in FIG. 1, the CO ₂ supercritical refrigeration cycle 11 is a two-stage compression two-stage expansion refrigeration cycle, and includes a low-stage compressor 12a, a rear-stage compressor 12b, a gas cooler 13a, and a high-stage two-phase flow expander 14a. , The intermediate cooler 15, the low-stage two-phase flow expander 14 b, and the evaporator 16.
[0031]
And as seen in the Mollier diagram shown in Figure 4,
The recovered CO ₂ (1) introduced by the low-stage compressor 12a and the reflux gas (10) from the evaporator 16 are adiabatically compressed to an intermediate pressure equal to or higher than the triple point pressure along the isentropic line. After being cooled from (2) to the saturated state (3) by the intercooler 15, the adiabatic compression is continued by the high-stage compressor 12b and compressed to a supercritical pressure of 7.38 MPa or more to become the supercritical state (4) and become a high temperature. A high-pressure compressed refrigerant is formed. Next, the gas cooler 13a is sensible heat cooled by the cold 31a to form the supercritical state (5).
The formed supercritical CO ₂ is depressurized to a pressure (6) just before the triple point, which is an intermediate pressure, by the adiabatic expansion means including the high-stage two-phase flow expander 14a, and is introduced into the intermediate cooler 15 to be liquefied CO _2. 18 is formed. Then, after passing through (7), the pressure is lowered to the pressure (8) below the triple point by the adiabatic expansion means comprising the low-stage two-phase flow compressor 14b from the intermediate cooler 15 to form the dry ice 19 or the low-temperature cold heat source 17.
[0032]
The low-temperature cold heat source 17 is formed by placing an antifreeze liquid 16a in an evaporator 16 provided downstream of the low-stage two-phase flow expander 14b and placing the antifreeze liquid 16a below the triple point through the expansion means in the antifreeze liquid. Low temperature low pressure CO ₂ in the solidification process formed by pressure reduction to the pressure is injected and cooled by direct contact with sublimation heat to form a low temperature medium equivalent to the temperature of the low temperature low pressure CO ₂ .
Therefore, the antifreeze liquid 16a in the evaporator 16 is cooled by direct contact with its sublimation heat by the CO ₂ pressure lowered below the injected triple point pressure, and efficiently forms a low-temperature medium up to about −79 ° C. The formed low-temperature medium can be refluxed to the cold heat source 17 to supply cold heat close to −79 ° C.
The injected low pressure CO ₂ is vaporized and refluxed to the low stage compressor 12a to form a cycle.
[0033]
Note that the evaporated gas of the antifreeze liquid is mixed in the vaporized CO ₂ that is refluxed by the direct contact, and the mixed gas is condensed and removed in a later step of the cycle.
In addition, CO ₂ is mixed in the antifreeze forming the low-temperature medium. However, the heat conductivity of the antifreeze having a low heat conductivity is improved by the mixing, which has an advantage of enabling efficient heat exchange.
[0034]
In addition, as shown in FIG. 3, the dry ice 19 is generated by providing a dry ice press machine 35 instead of the evaporator 16 downstream of the low-stage two-phase flow expander 14 b of the CO ₂ supercritical refrigeration cycle 11. Then, it is solidified by the press machine 35 to produce dry ice 19. The low temperature CO ₂ gas generated during the pressing returns to the low stage compressor 12a.
[0035]
The two-phase flow expanders 14a and 14b are formed by an expansion turbine and adiabatically expand CO ₂ during expansion. In addition, the power generator G (refer FIG. 4) connected directly is operated so that motive power can be recovered.
[0036]
Further, the liquefied CO ₂ 18 can generate the low-temperature cold heat source 17 in the cycle formation and supply cold heat close to about −79 ° C., or the generation of dry ice can diversify the use of cold heat such as storage of cold heat. Can be planned.
[0037]
【The invention's effect】
With the above configuration, the present invention has the following effects.
Using low-temperature exhaust heat, conversion to cold heat, and efficient recovery of low-concentration CO ₂ by performing combined use of the converted cold heat and the exhaust heat, the recovered CO ₂ is used as a refrigerant for a supercritical refrigeration cycle. As well as contributing to protection of the ozone layer and prevention of global warming, it has become possible to provide a manufacturing process of high-density energy such as liquefied CO ₂ and dry ice, and a low-temperature cold heat source around −70 ° C.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an exhaust CO ₂ recovery system of the present invention.
2 is a block diagram showing a schematic configuration of temperature-pressure swing adsorption (PTSA) in FIG. 1; FIG.
FIG. 3 is a block diagram showing a schematic configuration of the dry ice production apparatus of the present invention.
4 is a Mollier diagram of the CO ₂ liquefaction cycle of FIG. 1. FIG.
FIG. 5 is a block diagram showing an embodiment of a conventional combustion gas processing method.
FIG. 6 is a diagram showing a schematic configuration of a conventional CO ₂ liquefaction apparatus.
FIG. 7 is a block diagram showing a schematic configuration of a dry ice production apparatus in the case of using conventional CO ₂ crude gas.
[Explanation of symbols]
11 CO ₂ supercritical refrigeration cycle 12a Low stage compressor 12b High stage compressor 13a Gas cooler 14a High stage two phase flow expander 14b Low stage two phase flow expander 15 Intermediate cooler 16 Evaporator 16a Antifreeze liquid 17 Low temperature cold heat source 18 Liquefaction CO ₂
19 Dry ice 20 Temperature pressure swing adsorption (PTSA)
21 Adsorption / desorption mechanism 21a Adsorption 21b Desorption 22 Source gas supply unit 22a Blower 23a Adsorption promotion unit 23b Desorption promotion unit 24 Delivery unit 24a Vacuum release unit 25 Low temperature exhaust gas 26 Collected CO ₂
30 Low temperature exhaust heat 31 Waste heat drive chemical heat pump 31a Cold heat 35 Dry ice press machine

Claims (5)

Exhaust CO that uses low-temperature exhaust heat around 100 to 200 ° C of exhaust gas discharged from establishments such as thermal power plants, incineration facilities, and factories, and cold heat obtained from chemical heat pumps that operate using the exhaust heat _In the collection system of ₂ ,
A first means for recovering low-concentration CO ₂ discharged together with the exhaust gas by deformation pressure swing adsorption;
The recovered CO ₂ is used as a refrigerant for a CO ₂ supercritical refrigeration cycle equipped with a liquefier that operates by cold, and liquefied CO ₂ is formed in the front stage of the multi-stage expansion means, and below the triple point by the subsequent stage expansion means. The exhaust CO ₂ recovery system, characterized in that it is constituted by a cold heat generating means (second means) for forming a low temperature cold heat. The exhaust CO ₂ recovery system according to claim 1, wherein dry ice is generated by the low-temperature cold heat. _2. The exhaust CO ₂ recovery system according to claim 1, wherein the low-temperature cold heat formation is generated by a low-temperature medium formed by directly injecting low-pressure CO ₂ whose pressure is lowered to a triple point or less into the antifreeze liquid. The first means adds to the pressure swing adsorption (PTS) a temperature swing adsorption (TSA) comprising an adsorption promotion means using the cold generated by the exhaust heat and a desorption promotion means using the exhaust heat. The exhaust CO ₂ recovery system according to claim 1, wherein the system is configured. The CO ₂ supercritical refrigeration cycle by the second means is constituted by a two-stage compression and two-stage expansion refrigeration cycle, and the first stage adiabatic expansion means forms liquefied CO ₂ by a pressure drop before the triple point, 2. The exhaust CO ₂ recovery system according to claim 1, wherein the dry ice or the low-temperature cold heat source is formed by a pressure drop below the triple point by the second stage adiabatic expansion means.

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