JP6575050B2 - Carbon dioxide recovery method and recovery apparatus - Google Patents

Description

  The present invention relates to a carbon dioxide recovery method and recovery apparatus that uses an adsorbent that selectively adsorbs carbon dioxide and separates and concentrates carbon dioxide from a gas containing carbon dioxide such as combustion gas according to a pressure swing adsorption method. In particular, the present invention relates to a carbon dioxide recovery method and a recovery apparatus capable of recovering high-purity carbon dioxide by effectively using a configuration using a metal-organic structure as an adsorbent.

  Facilities such as thermal power plants, steelworks, and boilers use large amounts of fuel such as coal, heavy oil, and super heavy oil. Sulfur oxides, nitrogen oxides, and carbon dioxide emitted by the combustion of fuel are There is a need for quantitative and concentration restrictions on emissions from the perspective of air pollution prevention and global environmental protection. In recent years, carbon dioxide has been seen as a major cause of global warming, and movements to suppress emissions have become active worldwide. For this reason, in order to enable recovery and storage of carbon dioxide from combustion exhaust gases and process exhaust gases without releasing them into the atmosphere, various researches have been vigorously conducted. As a method for recovering carbon dioxide, for example, pressure swing Adsorption methods, membrane separation and concentration methods, chemical absorption methods utilizing reaction absorption by basic compounds, and the like are known.

  The pressure swing adsorption (PSA) method is a separation method in which a specific component in a gas is separated from a gas by using an adsorbent having selective adsorption property to the specific component, and a mixed gas containing a plurality of components. It is widely known as a separation method for the mixed gas and can be used as a separation method for mixed gas in various fields. In the PSA method, the specific component on the adsorbent adsorbed is then desorbed and recovered from the adsorbent by reducing the pressure, and adsorption and desorption are repeated. The separation efficiency of the PSA method depends on the selectivity of the adsorbent with respect to the specific component, but for the purpose of removing, separating, concentrating or purifying the specific component depending on the selectivity of the adsorbent and the specific component concentration of the raw material gas. The PSA method can be used. For example, Patent Document 1 described below describes supplying oxygen produced by a PSA apparatus to an oxyfuel combustion facility.

  Conventionally, as a method of recovering carbon dioxide from exhaust gas, after removing various impurities (sulfur oxide, nitrogen oxide, chlorine, mercury, etc.) from exhaust gas, the remaining concentrated carbon dioxide is subjected to cryogenic separation (liquefaction and precision distillation) The method of purifying by the method is promising, and various studies have been made for practical use.

  The separation of carbon dioxide using an adsorbent is described in Patent Document 2 below, for example. In this document, as an adsorbent, a carrier made of mesoporous silica is used which supports an element selected from Mg, Ca, Sr, Ba, Y, and La, and carbon dioxide adsorbed on the adsorbent is heated. Desorption has been shown. On the other hand, in Patent Document 3 below, silica gel, zeolite, porous glass, or the like is used as an adsorbent when water is adsorbed and removed in the presence of sulfur oxide or nitrogen oxide in the purification of gas containing carbon dioxide. It is described. In the development of new materials, attempts have been made to develop applications as adsorbents (see Non-Patent Documents 1 and 2 below).

JP 2001-221429 A JP 2010-184229 A Patent 5350376

The Society of Polymer Science, “Super Hybrid Materials (Polymer Frontier 21 Lecture Series 34)”, November 2012 SIGMA-ALDRICH catalog, “Fundamentals of Materials Science No.7: Basics of Porous Coordination Polymers (PCP) / Metal Organic Structures (MOF)”

  In the PSA method, it is relatively easy to selectively separate carbon dioxide from exhaust gas containing carbon dioxide and various types of impurities, and to recover high-purity carbon dioxide. Is better than a recovery method in which carbon dioxide is subjected to cryogenic separation (liquefaction and precision distillation) after removing various impurities (sulfur oxide, nitrogen oxide, chlorine, mercury, etc.) from the exhaust gas. In addition, there is an advantage that the burden of maintenance for coping with the corrosion of the instrument and apparatus for removing the impurities described above is reduced.

  However, the inorganic adsorbents conventionally used in the PSA method such as activated carbon and zeolite need to be set to a negative pressure condition or a high temperature state in order to desorb the adsorbed carbon dioxide. Since desorption by heating requires time for switching between adsorption / desorption, the processing efficiency is poor, so negative pressure conditions are advantageous for practical use. In this case, a carbon dioxide recovery device is used by using a vacuum pump. Must be configured. For this reason, in order to increase the processing capacity, it is necessary to enlarge the vacuum pump, and the improvement of the processing capacity is limited by the scale of the vacuum pump.

The object of the present invention is to recover carbon dioxide, which solves the above-mentioned problems, is excellent in energy saving and economical efficiency, and can recover high-concentration carbon dioxide from a carbon dioxide-containing gas with a high processing capacity using a pressure swing adsorption method. It is to provide a method and a recovery device.
Another object of the present invention is to provide a highly economical dioxide dioxide that has high energy utilization efficiency, reduces the burden of imparting durability to the apparatus, and can disperse the recovery of carbon dioxide in the treatment of exhaust gas such as combustion gas. It is to provide a carbon recovery method and a recovery apparatus.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research, and as a result, by using a metal-organic structure as an adsorbent, a vacuum pump is used for the separation apparatus by the PSA method by eliminating the negative pressure condition. The present invention has been completed by finding that it can be configured without using it, and that the gas used after the PSA method can be effectively used for dehumidification to improve the efficiency of energy use.

According to one aspect of the present invention, a carbon dioxide recovery device is a carbon dioxide recovery device having a separation device that separates carbon dioxide from gas by using adsorption and desorption of carbon dioxide to and from an adsorbent due to pressure fluctuation. The separator contains an adsorbent having a metal-organic structure, and the adsorbent adsorbs carbon dioxide contained in the gas by supplying gas, and releases the treated gas with reduced carbon dioxide. An adsorbing unit, a pressurizing unit that applies pressure to the gas so that the gas can be supplied to the adsorbing unit with a relatively high partial pressure of carbon dioxide, and a gas that has been pressurized by the pressurizing unit. and a suppliable gas supply system to the suction portion, the suction portion, in order to release from the suction unit to desorb carbon dioxide from the adsorbent having adsorbed carbon dioxide, lowering the pressure in the relative low pressure Pressure And a recovery system that recovers the desorbed carbon dioxide when the concentration of the desorbed carbon dioxide released from the adsorption unit is equal to or higher than a predetermined concentration, and the recovery system is released from the adsorption unit. A detector for detecting the concentration of the desorbed carbon dioxide provided in the flow path through which the desorbed carbon dioxide flows, and a reflux path branched from the flow path for supplying the desorbed carbon dioxide to the gas supply system And when the concentration of carbon dioxide detected by the detector is greater than or equal to a predetermined concentration, the desorbed carbon dioxide is recovered, and when the concentration of carbon dioxide detected by the detector is less than the predetermined concentration, desorption is performed. The gist of the invention is to supply the carbon dioxide that has been supplied to the gas supply system from the reflux path .

In the carbon dioxide recovery apparatus, the pressure lowering means includes a pressure control valve capable of releasing pressure from a gas to which pressure is applied, the relative low pressure is set to be equal to or higher than atmospheric pressure, and the separation apparatus includes Furthermore, it has a cooler that cools the gas supplied to the adsorption unit in advance and maintains it at a predetermined temperature or lower. The adsorption unit includes a pair of first adsorption tower and second adsorption tower, the adsorbent is accommodated in each of the first adsorption tower and the second adsorption tower, and the gas supply system is , the pressing by one by can be supplied alternately to urchin configuration of said gas that is applying pressure first adsorption column and the second adsorption tower by the first adsorption tower and the second adsorption In one of the columns, the carbon dioxide contained in the pressured gas is adsorbed to the adsorbent at a relatively high carbon dioxide partial pressure, and the treated gas with reduced carbon dioxide concentration is released alternately. The pressure reducing means alternately reduces the pressure on the other of the first adsorption tower and the second adsorption tower where the gas is not supplied, and the carbon dioxide is desorbed from the adsorbent at a pressure reduced to a relatively low pressure. Can be configured to be released

The detector of the recovery system, the first to detect the adsorption tower and the concentration of the desorbed carbon dioxide is released alternately from the second adsorption tower, wherein the recovery system, the gas supply system by prior Symbol return path has a pressurizing圧装location for applying pressure to the carbon dioxide is supplied to, thereby, the desorbed carbon dioxide can be configured to be adsorbed by the adsorbent. The adsorbing unit further switches the gas supply destination from the first adsorption tower to the second adsorption tower when the adsorbent in the first adsorption tower is broken, and the adsorbent in the second adsorption tower is broken. The gas supply destination can be switched from the second adsorption tower to the first adsorption tower at this time, and a control system that controls switching of the gas supply destination by the gas supply system can be provided. The control system has a detector that detects the concentration of carbon dioxide in the treated gas alternately discharged from the first adsorption tower and the second adsorption tower, and the concentration of carbon dioxide detected by the detector However, control may be performed based on the detected carbon dioxide concentration so that the gas supply destination is switched when the carbon dioxide concentration of the supplied gas is reached. A cooling unit for cooling the gas, a desulfurization unit for removing sulfur oxide from the gas, and a dehumidifying unit having a hygroscopic agent for removing moisture from the gas; A liquefying unit that is disposed downstream of the separation device and compresses recovered carbon dioxide to prepare liquefied carbon dioxide, and the separation device further includes a gas to which pressure is applied by the pressurizing unit. A heat exchanger for exchanging heat between the first adsorption tower and the treated gas emitted from the first adsorption tower and the second adsorption tower, and the treated gas passed through the heat exchanger to regenerate the moisture absorbent in the dehumidifying section. In order to use, it is good to comprise so that it may have a channel connected to the dehumidification part.

Moreover, according to one aspect of the present invention, a carbon dioxide recovery method includes a separation process for separating carbon dioxide from a gas using adsorption and desorption of carbon dioxide with respect to an adsorbent due to pressure fluctuation. The separation treatment includes a pressure treatment for applying pressure to the gas and a gas subjected to the pressure treatment at a relatively high carbon dioxide partial pressure to the adsorbent having a metal-organic structure. The pressure is set to a relatively low pressure so that carbon dioxide contained in the gas is adsorbed by the adsorbent and the carbon dioxide is desorbed and released from the adsorbent that has adsorbed carbon dioxide. carbon dioxide and desorption treatment for reducing the concentration of carbon dioxide desorbed is released by the desorption process when the predetermined concentration or more, possess a recovery process for recovering the desorbed carbon dioxide, it is detected When the concentration is below a predetermined concentration, and summarized in that feeding the desorbed carbon dioxide to the adsorption treatment.

  In the carbon dioxide recovery method, the relative low pressure is set to be equal to or higher than atmospheric pressure in the recovery process, and the pressure is reduced to a relatively low pressure by releasing the pressure using a pressure control valve. A cooling process in which the gas used in the adsorption process is cooled in advance and maintained at a predetermined temperature or lower. The separation process is performed using a first adsorption tower and a second adsorption tower each containing an adsorbent, and the adsorption process and the desorption process are performed by supplying a gas to the first adsorption tower to obtain a relatively high pressure. A first treatment for adsorbing carbon dioxide at a partial pressure of carbon dioxide and adjusting the second adsorption tower to a relatively low pressure to desorb carbon dioxide; and supplying a gas to the second adsorption tower to provide a relatively high pressure The carbon dioxide is adsorbed at a partial pressure of carbon dioxide, and the second treatment is performed by adjusting the first adsorption tower to a relatively low pressure to desorb carbon dioxide, and the separation treatment is further performed in the first treatment. When the adsorbent of the first adsorption tower is broken, the first process is switched to the second process, and when the adsorbent of the second adsorption tower is broken in the second process, the second process is changed to the first process. Switching operation to switch to And in the recovery process, the carbon dioxide released from the second adsorption tower or the first adsorption tower in each of the first treatment and the second treatment is released when the concentration is equal to or higher than a predetermined concentration. It can be configured to recover carbon dioxide.

  Furthermore, according to another aspect of the present invention, a carbon dioxide recovery device uses a dehumidifying unit having a hygroscopic agent that removes moisture from a gas, and adsorption and desorption of carbon dioxide with respect to the adsorbent due to pressure fluctuation. A carbon dioxide recovery device having a separation device for separating carbon dioxide from a gas, wherein the separation device contains an adsorbent having a metal-organic structure and is contained in the gas by supplying a gas. An adsorbing part from which the adsorbent is adsorbed and a gas after treatment with reduced carbon dioxide is released, a pressurizing part for applying pressure to the gas supplied to the adsorbing part, the pressurizing device, and the Heat exchange is performed between the gas placed between the adsorption tower and the pressure applied by the pressurizing device, and the post-treatment gas released from the adsorption tower to cool the gas and after the treatment Heat exchange to heat gas And a flow path for supplying the treated gas heated in the heat exchanging section to the dehumidifying part, wherein the dehumidifying part absorbs moisture using the heated treated gas. The gist is that it is configured to regenerate the agent. In the recovery apparatus, the adsorption unit includes a pair of first adsorption tower and the second adsorption tower each containing the adsorbent, and gas applied with pressure by the pressurization unit. A gas supply system capable of alternately supplying one of the second adsorption towers, and a pressure reducing means capable of alternately reducing the pressure on the other of the first adsorption tower and the second adsorption tower where gas is not supplied. In one of the first adsorption tower and the second adsorption tower, carbon dioxide contained in the pressure-applied gas is adsorbed to the adsorbent at a relatively high partial pressure of carbon dioxide, The treated gas having a reduced concentration of carbon dioxide is released, and carbon dioxide is desorbed and released from the adsorbent at a pressure reduced to a relatively low pressure in the other of the first adsorption tower and the second adsorption tower. Can be configured. Further, the pressure lowering means has a pressure control valve capable of releasing the pressure from the pressure-applied gas, and the relative low pressure is set to be equal to or higher than the atmospheric pressure.

  According to another aspect of the present invention, a method for recovering carbon dioxide uses a dehumidification process having a hygroscopic agent that removes moisture from a gas, and adsorption and desorption of carbon dioxide with respect to the adsorbent due to pressure fluctuation. And a separation process for separating carbon dioxide from the gas, wherein the separation process is performed using a pressurization process that applies pressure to the gas and a gas that has undergone the pressurization process. Gas is brought into contact with an adsorbent having an organic structure so that carbon dioxide contained in the gas is adsorbed to the adsorbent, and thereby, an adsorption treatment in which a gas after treatment with reduced carbon dioxide is released and the pressurization treatment are performed. Heat exchange between the pressure-applied gas and the post-treatment gas released by the adsorption treatment to cool the gas and heat the post-treatment gas, For exchange processing The processed gas which has been heated have been supplied to the dehumidifying process, the gist to play a desiccant with a heated said processed gas. In the above recovery method, the separation process further includes a desorption process for desorbing and releasing carbon dioxide from the adsorbent that has adsorbed carbon dioxide at a relatively low pressure, and each of the separation processes contains an adsorbent. In order to carry out using the first adsorption tower and the second adsorption tower, the gas pressurized by the pressure treatment is supplied alternately to one of the first adsorption tower and the second adsorption tower. Gas supply and a pressure reduction operation for alternately reducing the pressure on the other of the first adsorption tower and the second adsorption tower where gas is not supplied, whereby the adsorption treatment and the desorption treatment are Supplying a gas to the first adsorption tower to adsorb carbon dioxide at a relatively high carbon dioxide partial pressure, and adjusting the second adsorption tower to a relatively low pressure to desorb carbon dioxide; The second suction A gas is supplied to the tower to adsorb carbon dioxide at a relatively high partial pressure of carbon dioxide, and the first treatment is performed by a second treatment in which the first adsorption tower is adjusted to a relatively low pressure to desorb carbon dioxide, In one of the first adsorption tower and the second adsorption tower, carbon dioxide contained in the pressure-applied gas is adsorbed to the adsorbent at a relatively high carbon dioxide partial pressure, and the concentration of carbon dioxide is increased. The lowered treated gas is released, and the other of the first adsorption tower and the second adsorption tower can be configured such that carbon dioxide is desorbed and released from the adsorbent at a pressure reduced to a relatively low pressure. . Further, the relative low pressure is set to be equal to or higher than the atmospheric pressure, and the pressure reduction operation reduces the pressure to a relative low pressure using a pressure control valve capable of releasing the pressure.

  According to the present invention, the burden of the apparatus configuration is reduced by a pressure setting range that does not reach negative pressure, and simplification is possible. Therefore, it is possible to provide a carbon dioxide recovery method and recovery apparatus that are effective for energy saving and cost reduction. Since it can be carried out easily using general equipment without using special equipment or expensive equipment, it is economically advantageous, and the versatility of the carbon dioxide recovery method by the PSA method is enhanced. Effective for enlargement.

The graph which shows the adsorption isotherm of the metal-organic structure used as an adsorbent. The schematic block diagram which shows the collection | recovery apparatus of the carbon dioxide which concerns on one Embodiment of this invention. The schematic block diagram which shows the structure of the adsorption | suction part in the collection | recovery apparatus of FIG. The time chart which shows the time-dependent change of the carbon dioxide concentration of the gas discharge | released from an adsorption tower in the adsorption | suction part of FIG.

  The pressure swing adsorption (PSA) method is a method that separates and removes specific components in a mixed gas by using adsorption and desorption of specific components to the adsorbent due to pressure fluctuations, and adsorbs substances capable of adsorbing carbon dioxide. It can be used as an agent to recover carbon dioxide from a gas containing carbon dioxide such as combustion exhaust gas. By increasing the pressure of the exhaust gas supplied to the adsorbent to a relatively high pressure (adsorption pressure), carbon dioxide is adsorbed on the adsorbent and when the pressure is reduced to a relatively low pressure (desorption pressure), Carbon is desorbed and released from the adsorbent. By repeatedly increasing and decreasing the pressure and adsorbing and desorbing carbon dioxide in the exhaust gas to the adsorbent (desorbing the adsorbate), the carbon dioxide gas and the concentrated (or purified) carbon dioxide are removed from the exhaust gas. Carbon is obtained.

  Since activated carbon and zeolite, which are known as substances capable of adsorbing carbon dioxide, have a negative desorption pressure, the use of a vacuum pump is indispensable for the desorption of carbon dioxide, and the transition from the adsorption process to the desorption process is essential. There is a limit to shortening the time required for reducing the pressure (decompression time).

On the other hand, as a new functional material, in recent years, research on porous materials called metal-organic structures (MOFs) or porous coordination polymers (PCPs) has been advanced. Yes. A metal-organic structure is a structure in which a porous structure is formed based on a complex formed by coordination bond between a metal ion and an organic ligand. Attempts have been made to develop applications as adsorbents. When a metal-organic structure is used as an adsorbent, the adsorption isotherm showing the relationship between the pressure of the adsorbate and the equilibrium adsorption amount is characterized by an S-shaped curve having a sharp rise near a certain pressure. For example, when [Cu (4,4′-dihydroxybiphenyl-3-carboxyl) ₂ (4,4′-bipyridyl)] _n is measured as a metal-organic structure, as shown in FIG. Fluctuates rapidly around 0.25 MPa. In such an adsorption isotherm, the adsorption pressure is set in the high pressure range and the desorption pressure is set in the low pressure range with the pressure value (threshold value) at which the equilibrium adsorption amount suddenly increases (for example, 1, even if the pressure difference between the adsorption pressure and the desorption pressure is small, the difference in equilibrium adsorption amount (= adsorption capacity) can be increased. As a result, the load on the device due to the pressure fluctuation between the adsorption pressure and the desorption pressure is significantly smaller than when a conventional adsorbent is used, reducing the burden for imparting durability to the device structure. Is possible. Moreover, since the desorption pressure can be set to atmospheric pressure or positive pressure (above atmospheric pressure) instead of negative pressure, the adsorption pressure and desorption pressure can be set and adjusted by the pressure control valve without using a vacuum pump. Is possible. Therefore, the energy consumed by the vacuum pump is reduced, and the limitation on the processing capacity of the recovery device due to the performance of the vacuum pump, which is a problem in the conventional PSA method, is also eliminated.

  In accordance with the above, the present invention proposes a carbon dioxide recovery method and recovery apparatus configured to improve energy efficiency and processing capacity by using a metal-organic structure as an adsorbent by the PSA method. . Hereinafter, a method for recovering carbon dioxide oxygen and a recovery apparatus for carrying out the method according to the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram showing an embodiment of the carbon dioxide recovery apparatus of the present invention. The recovery device 1 has a separation device that separates carbon dioxide from the exhaust gas G using adsorption and desorption of carbon dioxide with respect to the adsorbent due to pressure fluctuation, and the separation device is configured with the adsorption unit AD as a main part, , Heat exchange for exchanging heat between the pressurization part PR for applying pressure to the exhaust gas G, and the exhaust gas G given pressure by the pressurization part PR and the treated gas G ′ released from the adsorption part AD Part EX. Further, a cooling unit CL that cools the exhaust gas G, a desulfurization unit DS that removes sulfur oxides from the exhaust gas G, and a dehumidification unit DH that has a hygroscopic agent that removes moisture from the exhaust gas G are sequentially provided in the preceding stage of the separation device. A liquefaction unit LQ is provided in the rear stage of the separation device to compress the carbon dioxide C recovered in the separation device to prepare liquefied carbon dioxide. In the cooling part CL, the desulfurization part DS, the dehumidification part DH, the pressurization part PR and the adsorption part AD, the exhaust gas G introduced into the cooling part CL is sequentially supplied to the desulfurization part DS, the dehumidification part DH, the pressurization part PR and the adsorption part AD. As supplied, they are connected in series by flow paths L1, L2, L3, and L4, and a heat exchange section EX is disposed on the flow path L4. The exhaust gas G supplied to the adsorption unit AD is separated into concentrated or purified carbon dioxide C and a treated gas G ′ that is a decarbonized gas from which carbon dioxide has been reduced or removed. The adsorbing part AD is connected to the liquefying part LQ and the dehumidifying part DH by the flow path L5 and the flow path L6, respectively. The concentrated or purified carbon dioxide C is supplied to the liquefying part LQ through the flow path L5. On the other hand, after the carbon dioxide is removed and the treated gas G ′ released from the adsorption unit AD is supplied to the dehumidifying unit DH through the channel L6, the heat in the heat exchange unit EX provided on the channel L4. Heated by exchange and used as a heating medium for regenerating the hygroscopic agent of the dehumidifying part DH. Further, a water sampling treatment unit WT for treating waste water generated in the cooling unit CL, the desulfurization unit DS, and the dehumidification unit DH is provided, and the waste water from each unit is supplied to the water sampling treatment unit WT through the flow paths L7, L8, and L9. Is done.

  The cooling unit CL is a facility for cooling the exhaust gas discharged from the combustion facility at a high temperature so as to have a temperature suitable for processing in the subsequent facility, and the exhaust gas G is about 40 ° C. or less, preferably about 30 ° C. It is configured to be cooled to the following outlet temperature. The combustion exhaust gas generally has an inlet temperature of about 100 to 200 ° C., and the volume of the exhaust gas G is reduced by cooling, so that the throughput in the subsequent equipment can be increased. The refrigerant may be any of commonly used refrigerants such as water, air-cooling, and refrigerants in the refrigeration cycle, and the contact with the refrigerant may be a direct contact method such as spraying, gas-liquid contact using a filler, or Any of cooling by an indirect contact method using a condenser or a heat exchanger may be used. In this embodiment, the exhaust gas G is sprayed with cooling water and cooled by direct contact with the cooling water. The direct contact method using cooling water has good economic efficiency and cooling efficiency, and also has a function as a cleaning means for removing chlorides, sulfur oxides and the like from the exhaust gas G. If the cooling water is contaminated by washing such components, the waste water is appropriately discharged to the water sampling treatment unit WT and replenished with cooling water.

  The desulfurization section DS is equipment for removing sulfur oxide from the exhaust gas G in order to prevent the adsorbent of the adsorption section AD from being contaminated or damaged by sulfur oxide. The desulfurization method includes dry desulfurization using a solid absorbent such as activated carbon and alumina, an adsorbent or a catalyst, and wet desulfurization using an aqueous liquid containing a basic substance such as ammonia, lime milk, and alkali metal hydroxide. Any of these methods may be used, and a desulfurization method generally used for desulfurization of exhaust gas may be appropriately selected and used. In this embodiment, a wet desulfurization apparatus based on a limestone / gypsum method using limestone dispersed water as an absorbing liquid is applied, and as a cooling means for preventing the temperature of the absorbing liquid from rising, a multitubular heat exchanger, a plate type A liquid-liquid type heat exchanger (not shown) such as a heat exchanger is attached to cool the absorption liquid by heat exchange with cooling water. When the calorific value and sulfur oxide concentration of the exhaust gas G are relatively small, it is possible to configure the above-described cooling part CL and the desulfurization part DS to be combined by a water washing apparatus that contacts the exhaust gas G with the spray water. If the exhaust gas G contains a small amount of chlorine gas, chlorine can also be removed in the desulfurization section DS. The absorbent or the like consumed by desulfurization is appropriately replaced. In the case of wet desulfurization, the waste water is discharged to the water sampling treatment unit WT to replenish the desulfurization aqueous liquid.

  The dehumidifying part DH is a facility for removing moisture from the exhaust gas G in order to prevent deterioration and damage of the adsorbent used in the adsorbing part AD, and the cooling unit CL and the desulfurizing part DS in the previous stage use a wet apparatus. This is especially important when configured. There is a hygroscopic agent inside, the exhaust gas is dehumidified by bringing the exhaust gas G into contact with the hygroscopic agent, and the low-humidity exhaust gas G is supplied to the pressurizing part PR. The hygroscopic agent may be appropriately selected from generally used hygroscopic agents such as silica gel, alumina gel, molecular sieve, zeolite, activated carbon and the like. Economically, a hygroscopic agent that can be easily regenerated by heating silica gel or the like is advantageous, and a temperature swing hygroscopic tower can be constructed. By constructing the dehumidifying section DH using one or more hygroscopic towers loaded with a hygroscopic agent, the exhaust gas G and the high-temperature regeneration gas are alternately supplied to the hygroscopic tower to absorb the moisture of the exhaust gas G and the hygroscopic agent. Can be alternately performed, and the dehumidification treatment and the regeneration of the hygroscopic agent can be repeated continuously without stopping the treatment of the exhaust gas G.

  In this embodiment, the dehumidifying part DH is configured to regenerate the moisture absorbent after being used for the dehumidifying process by using the post-treatment gas G ′ released from the adsorption part AD as a regeneration gas. Specifically, since the temperature of the exhaust gas G rises due to the application of pressure in the subsequent pressurizing part PR, the treated gas G ′ released from the adsorption part AD is converted into the high-temperature exhaust gas G using the heat exchange part EX. The heated post-treatment gas G ′ is supplied to the used moisture absorbent to release moisture from the moisture absorbent. In the heat exchanging unit EX, the temperature of the treated gas G ′ generally rises to about 150 to 180 ° C., and becomes a high-temperature dry gas having a dew point of about −90 to −60 ° C. that hardly contains moisture. The treated gas G ′ containing moisture by regeneration of the moisture absorbent is discharged to the outside through the pressure control valve PV, and the pressure of the treated gas G ′ is released to atmospheric pressure. In this embodiment, all the processed gas G ′ released from the adsorption unit AD is used as a regeneration gas. However, a part of the processed gas G ′ released from the adsorption unit AD is used. May be used to cool the exhaust gas G supplied from the desulfurization section DS. For example, the flow path L6 is branched and connected so that a part of the treated gas G ′ is supplied directly to the dehumidifying part DH without going through the heat exchanging part EX. A heat exchanger for exchanging heat can be provided in the front stage of the moisture absorption tower. When the temperature of the exhaust gas G decreases, the water vapor condenses and separates due to a decrease in the saturated water vapor pressure, so the condensed water generated by cooling the exhaust gas G is separated from the exhaust gas G and discharged as waste water to the water sampling treatment unit WT. Since the cooled exhaust gas G is dehumidified by contact with the hygroscopic agent, the low temperature and low humidity exhaust gas G is supplied to the pressurizing part PR.

  The pressurizing part PR is an apparatus for applying the pressure required for carbon dioxide adsorption to the exhaust gas G in the subsequent adsorption part AD, and adsorbs the exhaust gas with the carbon dioxide partial pressure of the adsorption pressure (relatively high pressure) PA. Pressure is applied to the exhaust gas G so that it can be supplied to the exhaust gas G. Therefore, any pressurization means that can increase the carbon dioxide partial pressure of the exhaust gas G to the adsorption pressure PA applied in the adsorption unit AD may be used. The pressure applied to the exhaust gas G by the pressurizing part PR can be maintained in the adsorption part AD by the pressure control valve PV described above, and the pressure of the exhaust gas G can be adjusted by the control of the pressure control valve PC. In the present invention, the adsorption pressure applied in the adsorption part AD is preferably equal to or greater than the threshold value indicated by the adsorption isotherm of the adsorbent, and is generally set to an adsorption pressure of about 0.3 to 0.5 MPa, although it varies depending on the adsorbent used. be able to. Therefore, the pressurizing part PR may be any pressure applying means capable of generating a fluid pressure capable of pressurizing the exhaust gas G so that the carbon dioxide partial pressure becomes an appropriate adsorption pressure. For example, a pressurizing pump, a compressor And blowers. A device having a relatively small applied pressure as compared with the conventional method can be used, and a compressor and a blower can be suitably used, and the compressor is optimal. The pressure applied in the pressurizing part PR is determined based on the carbon dioxide concentration of the exhaust gas G and the adsorption pressure. That is, in the adsorption isotherm for the carbon dioxide of the adsorbent used in the adsorption unit AD, a pressure equal to or higher than the threshold is appropriately set as the adsorption pressure, and the carbon dioxide partial pressure of the exhaust gas G is adsorbed according to the carbon dioxide concentration of the exhaust gas G. The pressure is set to be a pressure. Accordingly, the pressure of the pressurized exhaust gas G is 100 × adsorption pressure / carbon dioxide concentration of exhaust gas G [%]. The temperature of the exhaust gas G rises due to the pressurization in the pressurization part PR. For example, when the exhaust gas G having a temperature of 40 ° C. and a carbon dioxide concentration of 80% (volume ratio) is pressurized to about 0.5 MPa, the carbon dioxide partial pressure (that is, the adsorption pressure) is about 0.4 MPa. The temperature of G is about 190 ° C. Thus, when the pressurization pressure of the exhaust gas G is appropriately adjusted in accordance with the carbon dioxide concentration in the pressurizing part PR, the temperature of the exhaust gas G after the pressure increase generally rises to about 180 to 200 ° C.

  The heat exchanging unit EX is installed so as to exchange heat by indirect contact between the high-temperature exhaust gas G pressurized by the pressurizing unit PR and the treated gas G ′ recirculated from the adsorption unit AD. The high-temperature exhaust gas G is cooled to about 50 to 70 ° C. and pumped to the adsorption unit AD in the heat exchange part EX, and the cooling temperature is about 30 to 40 ° C. or lower depending on the heat exchange rate of the heat exchange part EX. It can also be lowered. The treated gas G ′ having a temperature of about 20 to 40 ° C. refluxed from the adsorption unit AD is heated to about 150 to 180 ° C. and supplied to the dehumidifying unit DH as a regeneration gas. What is necessary is just to comprise the heat exchange part EX using a well-known air-air heat exchanger. Any type such as a counter flow type, a parallel flow type, and a cross flow type may be used, and for example, a static heat exchanger, a rotary regenerative heat exchanger, a periodic heat storage heat exchanger, or the like can be appropriately selected. is there.

  The adsorbing part AD is a main part of the recovery apparatus of the present invention, contains an adsorbent having a metal-organic structure, adsorbs the carbon dioxide contained in the exhaust gas G by supplying the exhaust gas G, The treated gas with reduced carbon dioxide is released. Specifically, it has a pair of adsorption towers containing an adsorbent for separating carbon dioxide from exhaust gas according to the PSA method, and each adsorbs a metal-organic structure capable of selectively adsorbing carbon dioxide. Housed inside as an agent. In each of the adsorption towers, when the exhaust gas G is supplied at a pressure at which the carbon dioxide partial pressure becomes the adsorption pressure (relatively high pressure), the carbon dioxide contained in the exhaust gas G is adsorbed by the adsorbent, and the pressure is desorbed (relative). Carbon dioxide is desorbed and released from the adsorbent. Therefore, by switching the two adsorption towers so that the adsorption and desorption of carbon dioxide are alternately performed, the series of operations of supplying the exhaust gas G and reducing the pressure is repeated, so that the dioxide dioxide from the exhaust gas G in each adsorption tower. Carbon separation and recovery are alternately repeated (the specific configuration and operation of the adsorption unit AD will be described later with reference to FIG. 3). Using the exhaust gas G continuously supplied from the pressurizing unit PR, carbon dioxide C can be alternately recovered from the two adsorption towers of the adsorption unit AD, and the recovered carbon dioxide C is supplied to the liquefaction unit LQ. . The treated gas G ′ from which carbon dioxide has been removed is refluxed to the dehumidifying part DH through the flow path L6 and the heat exchanging part EX, and is discharged after being used as a high-temperature gas for regeneration. That is, the treated gas G ′ also acts as a heat medium that carries the heat energy of the pressurized exhaust gas G to the dehumidifying part DH.

  The liquefaction part LQ has a compression device for compressing the carbon dioxide C and a cooling device for cooling using a heat exchanger. The concentrated or purified carbon dioxide C recovered in the adsorption unit AD is liquefied in the liquefaction unit LQ by cooling to the boiling line temperature or lower, preferably about −20 to −50 ° C. and pressurizing and compressing. The liquefied carbon dioxide C is preferably prepared in a supercritical state, and carbon dioxide C liquefied and purified to a purity of about 95 to 99% is obtained.

  As described above, the exhaust gas G supplied to the recovery device 1 is sequentially subjected to a cooling process, a desulfurization process, a dehumidification process, a separation process, and a liquefaction process. In the separation process, the exhaust gas G by pressure treatment and heat exchange is used. Cooling, adsorption processing, desorption processing, and recovery processing are performed. The post-treatment gas G ′ heated in the heat exchange for cooling the pressurized exhaust gas G is used to regenerate the hygroscopic agent used in the dehumidification treatment.

  FIG. 3 shows a specific configuration of the adsorption unit AD in the recovery device 1 of FIG. In addition, the broken line in FIG. 3 shows electrical connection. The adsorption unit AD is configured as a main part of a separation device that adsorbs and separates carbon dioxide from a mixed gas according to the PSA method, and a pair of adsorption columns each composed of a first adsorption tower 2a and a second adsorption tower 2b each containing an adsorbent F. A tower, a gas supply system capable of alternately supplying exhaust gas G to one of the first adsorption tower 2a and the second adsorption tower 2b, and an exhaust gas G of the first adsorption tower 2a and the second adsorption tower 2b are supplied. On the other hand, it has pressure reducing means that can alternately reduce the pressure to a relatively low pressure, a control system that controls switching of the supply destination of the exhaust gas G by the gas supply system, and a recovery system that recovers the desorbed carbon dioxide.

  Specifically, the gas supply system includes a flow path 3 for introducing the exhaust gas G from the outside of the adsorption unit AD, and a flow branched from the flow path 3 and connected to the first adsorption tower 2a and the second adsorption tower 2b, respectively. It is comprised by the switching valve 6 which can switch the connection of the flow path 4 and 5 and the flow path 3 and the flow paths 4 and 5, and the connection destination of the flow path 3 is made into the flow path 4 and the flow path 5 by the switching valve 6. By switching between them, the supply destination of the exhaust gas G is switched between the first adsorption tower 2a and the second adsorption tower 2b. Since the exhaust gas G is pressurized in the pressurizing unit PR so that the carbon dioxide partial pressure becomes the adsorption pressure, the carbon dioxide contained in the exhaust gas G is adsorbed by the adsorbent in the adsorption tower to which the exhaust gas G is supplied. Then, the treated gas G ′ having a reduced carbon dioxide concentration is released. Accordingly, when the exhaust gas G is alternately supplied to one of the first adsorption tower 2a and the second adsorption tower 2b by switching the switching valve 6, the treated gas G ′ having a reduced carbon dioxide concentration is converted into the first adsorption tower 2a. And alternately discharged from the second adsorption tower 2b. The flow path 3 has a cooler 7 for cooling the exhaust gas G in advance and maintaining it at a predetermined temperature or lower, and the cooling temperature is about 40 ° C. or lower, preferably about 30 ° C. or lower, more preferably about 20 ° C. The following is suitable, and a water-cooled cooler using a coolant of about 5 to 25 ° C. as a refrigerant can be suitably used as the cooler 7. The cooler 7 is for supplementing the cooling by the heat exchanging unit EX, and can be omitted when the cooling by the heat exchanging unit EX is sufficient.

  On the opposite side to the flow paths 4 and 5 of the first adsorption tower and the second adsorption tower, a flow path 8 for deriving the treated gas G ′ and a flow path 9 for deriving the carbon dioxide C are provided. . The flow path 8 is connected to each of the first adsorption tower 2a and the second adsorption tower 2b by the flow path 10 and the flow path 11, and the connection destination can be switched by the switching valve 12 so as to communicate with one of the adsorption towers. It is. The flow path 9 is connected to each of the first adsorption tower 2a and the second adsorption tower 2b by the flow path 13 and the flow path 14, respectively, and the connection destination is switched by the switching valve 15 so as to communicate with one of the adsorption towers. Is possible. Further, the first adsorption tower 2a can switch the connection destination so as to communicate with either the flow path 10 or the flow path 13 by the switching valve 16, and the second adsorption tower 2b can be switched by the switching valve 17 to the flow path. The connection destination can be switched so as to communicate with either one of 11 and 14. The flow path 8 is provided with a concentration sensor 18 as a detector for detecting the concentration of carbon dioxide in the discharged processed gas G ′. The switching valves 6, 12, 15, 16, and 17 are those that can be electrically controlled such as electromagnetic valves, and the concentration sensor 18 is electrically connected to the switching valves 6, 12, 15, 16, and 17. Connected. Since the desorption pressure is equal to or higher than the atmospheric pressure, a pressure control valve is provided as a pressure reducing means capable of releasing the pressure from the exhaust gas to which the pressure is applied. Specifically, the flow path 9 is provided with a pressure control valve 19 for maintaining the upstream pressure below a certain value, so that the gas pressure of the adsorption tower communicating with the flow path 9 becomes the desorption pressure. Set to Therefore, in the first adsorption tower 2a and the second adsorption tower 2b, when the exhaust gas G is supplied to adsorb carbon dioxide and then connected to the flow path 9 to reduce the pressure to the desorption pressure, the adsorbed carbon dioxide C is Released.

  When one of the first adsorption tower 2a and the second adsorption tower 2b communicates with the flow path 3 and the flow path 8, the other of the switching valves 6, 12, 15, 16, and 17 communicates with the flow path 9 and communicates with the flow path. The connection switching is controlled so as to be disconnected from 3. Therefore, when the exhaust gas G is supplied from the flow paths 3 and 4 to the first adsorption tower 2a and the carbon dioxide partial pressure becomes the adsorption pressure (relatively high pressure), the treated gas G ′ flows from the first adsorption tower 2a. The second adsorption tower 2b is cut off from the exhaust gas G and communicated with the flow path 9 through the flow path 14 through the passage 10 and thereby the pressure inside the second adsorption tower 2b is desorbed ( The carbon dioxide desorbed from the adsorbent F is released through the flow path 9. When the exhaust gas G is supplied from the flow paths 3 and 5 to the second adsorption tower 2b, the treated gas G ′ is released from the second adsorption tower 2b to the flow path 8 through the flow path 11 and the first adsorption tower. The carbon dioxide 2 a that is blocked from the exhaust gas G and desorbed from the adsorbent F is released to the flow path 8 through the flow path 13.

  The treated gas G ′ released from the first adsorption tower 2a while the exhaust gas G is supplied to the first adsorption tower 2a is kept at a low concentration of carbon dioxide before the adsorbent F breaks down. When the adsorbent F approaches rupture, the concentration of carbon dioxide rapidly increases and reaches the concentration of carbon dioxide in the exhaust gas G before treatment. The concentration sensor 18 in the flow path 8 detects breakage based on the detected carbon dioxide concentration information, and when the adsorbent F is broken, that is, the concentration of carbon dioxide in the treated gas G ′ is the carbon dioxide in the exhaust gas. When the concentration is reached, a control signal is issued to the switching valves 6, 12, 15, 16, 17, and the switching valves 6, 12, 15, 16, 17 are switched so that the supply destination of the exhaust gas G is switched to the second adsorption tower 2 b. Connection is controlled. Therefore, the concentration sensor 18 and the switching valves 6, 12, 15, 16, and 17 function as a control system that controls switching of the supply destination of the exhaust gas G, and the exhaust gas G when the adsorbent F of the first adsorption tower 2a is destroyed. Is switched from the first adsorption tower 2a to the second adsorption tower 2b, and when the adsorbent F in the second adsorption tower 2b is broken, the supply destination of the exhaust gas G is switched from the second adsorption tower 2b to the first adsorption tower 2a. .

  In the first adsorption tower 2a, when the exhaust gas G is blocked by the breach of the adsorbent F and the first adsorption tower 1a is connected to the flow path 9, the exhaust gas G in the tower is released via the pressure control valve 19. In the meantime, the gas pressure in the party falls to the desorption pressure (the carbon dioxide partial pressure is lower than the desorption pressure). At the same time, desorption of carbon dioxide C starts in the adsorbent F, and the pressure is maintained at the desorption pressure while releasing carbon dioxide through the pressure control valve 19. The carbon dioxide concentration of the gas released from the adsorption tower can be increased from the concentration of carbon dioxide in the exhaust gas G to 95% (volume ratio) or more. For example, when the concentration of carbon dioxide in the exhaust gas G is about 60% or more, it is possible to recover the carbon dioxide C concentrated or purified to a concentration of 90 to 99%. At this time, detection is performed to detect the concentration of carbon dioxide as a recovery system that recovers carbon dioxide C when the concentration of desorbed carbon dioxide C reaches or exceeds a predetermined concentration without recovering low-concentration carbon dioxide at the initial stage of desorption. A concentration sensor 20 provided on the flow path 9 as a vessel, a reflux path 21 branched from the flow path 9, and a switching valve 22 provided at a branch point of the flow path 9, and carbon dioxide C having a concentration lower than a predetermined concentration is Then, the gas is supplied to the gas supply system through the reflux path 21 without being collected. As the switching valve 22, a valve that can be electrically controlled such as an electromagnetic valve is used, and the concentration sensor 20 is electrically connected to the switching valve 22. Accordingly, when the concentration of carbon dioxide C released from the first adsorption tower 2a is detected by the concentration sensor 20 and is less than the predetermined concentration, the switching valve 22 communicates the flow path 9 and the reflux path 21 and is desorbed. Carbon is supplied to the flow path 3 of the gas supply system. When the concentration of the carbon dioxide C reaches a predetermined concentration, a control signal for switching the connection of the switching valve 22 is issued based on the concentration information, and the control signal is discharged from the flow path 9 to the outside of the adsorption unit AD and supplied to the liquefaction unit LQ. . On the reflux path 21, a compressor 24 is provided as a pressurizing device for applying pressure to the carbon dioxide supplied to the gas supply system, and the carbon dioxide C that has fallen below the desorption pressure is returned again by the compressor 24. The pressure is controlled by the pressure control valve 23 so that the pressure is increased and is approximately equal to the supply pressure of the exhaust gas G. The compressor 24 may be replaced with other pressurizing means such as a blower. A check valve 25 for preventing a backflow of gas from the flow path 3 to the reflux path 21 is provided near the junction with the flow path 3 on the reflux path 21. The compressor 24 is electrically connected to the concentration sensor 20 and is controlled so that the switching of the switching valve 22 and the operation of the compressor 24 are interlocked. When the switching valve 22 connects the reflux path 21 and the flow path 9, the carbon dioxide C having a concentration lower than the predetermined concentration is supplied to the second adsorption tower 2 b during the adsorption process through the reflux path 21 and is adsorbed by the adsorbent F. The

  If the adsorbent F breaks in the second adsorption tower 2b, the connection in the gas supply system is switched again, and the supply of the exhaust gas G and the adsorption of carbon dioxide are started in the first adsorption tower 2a. In this way, the exhaust gas G is alternately supplied to one of the first adsorption tower and the second adsorption tower to release the treated gas G ′, and on the other hand, the carbon dioxide C is desorbed from the adsorbent F. The purity of carbon dioxide recovered from the flow path 9 and supplied to the liquefaction unit LQ is determined by the carbon dioxide concentration setting for switching the connection destination of the switching valve 22, and the setting is appropriately changed according to the quality requirements in the liquefaction unit LQ. it can.

A metal-organic structure is used as the adsorbent F accommodated in the first adsorption tower 2a and the second adsorption tower 2b. For example, [Cu (4,4′-dihydroxybiphenyl-3-carboxyl) ₂ (4,4′-bipyridyl)] _n , [Cu (PF ₆ ⁻ ) ₂ (1,2-bis (4-pyridyl) ethane) ] _N , [Cu (CF ₃ SO ₃ ⁻ ) ₂ (1,3-bis (4-pyridyl) propane) ₂ ] _n , {[Cu (PF ₆ ⁻ ) (2,2-bis (4-pyridyl)) ] PF ₆ ⁻ } _n , [Cu ₂ (PF ₆ ⁻ ) ₂ (4,4′-bipyridyl) propane) ₂ ] _n , [Cu ₂ (PF ₆ ⁻ ) ₂ (pyridine) ₄ ] _n , [M ₂ ( 2,5-dioxide-1,4-benzenedicarboxylate)] (wherein M is Mg ²⁺ , Mn ²⁺ , Co ²⁺ , Ni ²⁺ , Fe ²⁺ or Zn ²⁺ ), [Cu (4,4′-dioxidebiphenyl-3-carboxylate) ₂ (4,4′-bipyridyl)] _n , [Zn ₄ O (4,4 ′, 4 ″-(benzene-1,3,5) -Triyl-tris (benzene-4,1-diyl) tribenzoate) ] A metal-organic structure such as _n, etc. In addition, a commercially available metal-organic structure that exhibits adsorptivity to carbon dioxide may be appropriately selected and used. When a plurality of pairs of adsorption towers are used so as to be feasible, a different type of metal-organic structure may be used in each group so as to exhibit the adsorption performance according to the type. Some organic structures are adsorptive to multiple types of gases, but even in such cases, the threshold pressure in the adsorption isotherm generally depends on the type of gas and depends on the appropriate pressure setting. The selective adsorption of carbon dioxide can be suitably performed.

  In the above configuration, the switching valves 6, 12, 15 to 17, 22 and the concentration sensors 18, 20 are connected to an arithmetic processing device such as a CPU, and concentration information obtained by the concentration sensors 18, 20 is managed in the arithmetic processing device. However, the switching valves 6, 12, 15 to 17, 22 may be configured to be automatically controlled, and this makes it possible to perform complicated processing such as operation correction by correcting density information and handling in the event of an abnormality.

  The composition of the combustion exhaust gas varies depending on the fuel and combustion type, and the exhaust gas by oxyfuel combustion generally contains about 80% carbon dioxide, about 10% nitrogen and about 10% oxygen (volume ratio). A small amount of water vapor and impurities such as sulfur oxide, nitrogen oxide, chlorine, mercury and the like may be included. When such a combustion gas is processed as the exhaust gas G, carbon dioxide concentrated at a high concentration of about 98% or more can be recovered from the adsorption part AD. Since the exhaust gas G supplied to the adsorption unit AD has the water vapor and sulfur oxide removed through the desulfurization unit DS and the dehumidification unit DH, the treated gas G ′ discharged from the adsorption unit AD contains almost no water vapor. It is suitable for use as a regeneration gas in the dehumidifying part DH. By utilizing this point, the present invention is configured to recover the heat energy generated from the pressure applied to the exhaust gas G supplied to the adsorption unit AD and use it for regeneration of the moisture absorbent in the dehumidification unit DH. The configuration of the invention is superior in terms of energy utilization efficiency.

  In the carbon dioxide recovery method of the present invention, a separation process performed in the adsorption unit AD of FIG. 3 will be described below with reference to FIG. FIG. 4 is a time chart showing a change in posting of the carbon dioxide concentration of the gas released from each adsorption tower when the exhaust gas G having a carbon dioxide concentration of 60% (volume ratio) is processed. 1 shows the change over time in the carbon dioxide concentration (volume%) of the gas released from the first adsorption tower 2a, and (b) shows the change over time in the carbon dioxide concentration (volume%) of the gas released from the second adsorption tower 2b. Show.

  In the separation process, the first adsorption tower 2a and the second adsorption tower 2b each containing the adsorbent F containing the metal-organic structure are used to utilize adsorption and desorption of carbon dioxide to the adsorbent due to pressure fluctuation. Separate carbon dioxide from exhaust gas. The separation treatment is included in the exhaust gas G by bringing the exhaust gas G into contact with the adsorbent at a relatively high pressure of carbon dioxide partial pressure using the pressure treatment for applying pressure to the exhaust gas and the exhaust gas G that has undergone the pressure treatment. It is released by an adsorption process that adsorbs carbon dioxide to the adsorbent, a desorption process that desorbs carbon dioxide from the adsorbent that adsorbs carbon dioxide and releases carbon dioxide by reducing the pressure to the desorption pressure, and a desorption process. A recovery process for recovering the desorbed carbon dioxide when the concentration of the desorbed carbon dioxide is equal to or higher than a predetermined concentration.

  Since the separation process is performed using a pair of adsorption towers including the first adsorption tower and the second adsorption tower, the above-described adsorption treatment and desorption treatment are performed by supplying the exhaust gas G to the first adsorption tower 2a and relatively high pressure. Carbon dioxide is adsorbed at the partial pressure of carbon dioxide, and the second adsorption tower 2b is adjusted to a relatively low pressure to desorb carbon dioxide (period before time ta in the time chart), and second adsorption. A second treatment (determined in the time chart) of supplying exhaust gas G to the tower 2b to adsorb carbon dioxide at a relatively high partial pressure of carbon dioxide and adjusting the first adsorption tower 2a to a relatively low pressure to desorb carbon dioxide. For a period after time ta). The separation process is further switched from the first process to the second process (time ta in the time chart) when the adsorbent F of the first adsorption tower 2a is broken in the first process, and the second adsorption tower 2b in the second process. When the adsorbent F is broken, it has a switching operation (not shown) for switching from the second process to the first process. In the recovery process, the second adsorption is performed in each of the first process and the second process after the switching operation. When the concentration of carbon dioxide released from the tower 2b or the first adsorption tower 2a is equal to or higher than a predetermined concentration, the released carbon dioxide is recovered (a period after time tb and a period before time ta).

  Since the adsorption reaction of carbon dioxide in the metal-organic structure is an exothermic reaction, and the desorption reaction is an endothermic reaction, the temperature can fluctuate up to about 20 ° C. by repeated adsorption and desorption. Since it is desirable to maintain the temperature at the time of adsorption at a low temperature in order to adsorb carbon dioxide quickly, the exhaust gas G supplied to the first adsorption tower 2a or the second adsorption tower 2b in each of the first treatment and the second treatment is Then, it is cooled in advance in the heat exchanging unit EX and the cooler 7 and maintained at a predetermined temperature or lower, specifically about 40 ° C. or lower, preferably about 30 ° C. or lower, more preferably about 20 ° C. or lower. The cooling method of the exhaust gas G is not particularly limited, and may be appropriately selected from well-known refrigerant cooling techniques such as a water cooling method and an air cooling method and applied to the cooler 7, and can be satisfactorily performed by the water cooling method. If the heat exchanger EX can be sufficiently cooled, the cooling in the cooler 7 can be omitted.

  For example, an exhaust gas G having a carbon dioxide concentration of 60%, a temperature of 20 ° C., and 0.6 MPa is supplied to start the first separation process (period before time ta) (the second time chart in FIG. When the carbon dioxide is adsorbed on the adsorption tower 2b, the first adsorption tower 2a on the adsorption side starts adsorption of carbon dioxide at an adsorption pressure of 0.36 MPa. The gas released from the first adsorption tower 2a is discharged through the flow path 8 as the treated gas G ', and the carbon dioxide concentration of this gas is adsorbed by the amount of carbon dioxide adsorbed as shown in FIG. It is extremely low until it approaches the adsorption capacity of the adsorbent F, but when the adsorbent F is nearly broken (adsorption saturation), the carbon dioxide concentration of the released gas begins to increase due to the decrease in the adsorption speed, and the carbon dioxide concentration of the exhaust gas G (60 %) And the adsorbent F is destroyed (time ta). During this time, in the second adsorption tower 2b on the desorption side, the pressure is regulated to a desorption pressure of 0.2 MPa by the pressure control valve 19, and carbon dioxide is released from the second adsorption tower 2b. When the concentration of carbon dioxide released from the second adsorption tower 2b is equal to or higher than a predetermined concentration (before time ta), a recovery process for recovering the released carbon dioxide C is performed. In addition, since the temperature of the adsorbent F is reduced by the endothermic reaction during desorption, the temperature inside the adsorbent F during adsorption becomes higher than that during desorption even when the supplied exhaust gas G is cooled to a constant temperature. For this reason, the speed at which the adsorbent F takes in carbon dioxide at the time of adsorption is faster than the speed at which it is released at the time of desorption, and can generally be about 1.2 times. Accordingly, the release of carbon dioxide from the desorption side adsorbent F is substantially continued until the adsorption side adsorbent F is broken.

  When the adsorbent F in the first adsorption tower 2a is broken in the first process, a switching operation for switching from the first process to the second process is performed. This operation is performed when the concentration sensor 18 detects the carbon dioxide concentration of the treated gas G ′ released from the first adsorption tower, and the detected carbon dioxide concentration reaches the carbon dioxide concentration of the exhaust gas G to be supplied ( At time ta), it is determined that the adsorbent F has broken, and the process is executed by switching the switching valves 6, 12, 15 to 17. By this switching operation, the first adsorption tower 2a is connected to the flow path 9 and the pressure is reduced to the desorption pressure. Therefore, desorption in the adsorbent F starts, and the second adsorption tower 2b is connected to the flow path 3 and the exhaust gas. Since G is supplied and the carbon dioxide partial pressure reaches the adsorption pressure, the adsorption by the adsorbent F is started. That is, the second process (after the elapsed time t: ta) is started.

  In the second treatment, the pressure of the first adsorption tower 2a is adjusted to the desorption pressure, and carbon dioxide is desorbed from the adsorbent F. Therefore, the carbon dioxide concentration of the gas released from the first adsorption tower 2a is It gradually increases from carbon dioxide. During this time, the exhaust gas G is supplied to the second adsorption tower 2b, and the carbon dioxide partial pressure reaches the adsorption pressure so that the carbon dioxide is adsorbed. Therefore, the carbon dioxide concentration of the gas released from the second adsorption tower 2b decreases. The concentration becomes extremely low.

  In the second process, the concentration of carbon dioxide released from the first adsorption tower 2a after the switching operation increases and reaches a predetermined concentration (for example, 98%). When the carbon dioxide concentration detected by the concentration sensor 20 is less than a predetermined concentration, the switching valve 22 of the flow channel 9 connects the flow channel 9 to the reflux path 21 and when the detected carbon dioxide concentration reaches the predetermined concentration. The connection switching is set so as to connect the flow path 9 and the outside. Therefore, the recovery process for recovering the carbon dioxide C released from the first adsorption tower 2a is performed when the concentration of the released carbon dioxide is equal to or higher than a predetermined concentration (after time tb). During a period (time ta to time tb) in which the concentration of carbon dioxide C released from the first adsorption tower is less than a predetermined concentration, the released carbon dioxide C passes through the reflux path 21 from the flow path 9 and is compressed. The pressure is applied so as to be equivalent to the exhaust gas G and is introduced into the flow path 3. Accordingly, the carbon dioxide C having a concentration lower than the predetermined concentration is supplied to the second adsorption tower 2b on the adsorption side, and the carbon dioxide is adsorbed by the adsorbent F.

  The state after this is not shown in the time chart of FIG. 4, but if the adsorbent F of the second adsorption tower 2b breaks down in the second process, the release gas from the second adsorption tower 2b is not shown in the second process. Since the carbon dioxide concentration rises as before time ta in FIG. 4A and reaches the same concentration as the exhaust gas G, the switching operation is performed to switch from the second process to the first process. In the first process performed in the same manner as described above, carbon dioxide while the concentration of carbon dioxide released from the second adsorption tower 2b after the switching operation is less than a predetermined concentration passes from the reflux path 21 through the flow path 3. It is supplied to the first adsorption tower 2a. When the carbon dioxide concentration increases and reaches a predetermined concentration, recovery of the released carbon dioxide C is started by switching the connection of the switching valve 22.

  In this way, the adsorption and desorption of carbon dioxide are alternately repeated in the first adsorption tower 2a and the second adsorption tower 2b, and the treated gas G ′ having a reduced carbon dioxide concentration and the desorbed carbon dioxide C are alternately taken. Released repeatedly. By performing adsorption separation of carbon dioxide using a metal-organic structure having a high selective adsorption property of carbon dioxide, it is possible to recover carbon dioxide concentrated or purified to a high purity as shown in FIG. Therefore, the present invention may be applied to a carbon dioxide-containing gas other than exhaust gas, and may be used to purify carbon dioxide by utilizing the point that high purity carbon dioxide is obtained. When the carbon dioxide concentration of the exhaust gas G is low, it can be dealt with by increasing the pressure applied in the pressurizing part PR so that the carbon dioxide partial pressure of the exhaust gas G becomes a suitable adsorption pressure. However, when the pressure of the exhaust gas G is increased, the partial pressure of other components (nitrogen, oxygen, etc.) contained in the exhaust gas G is also increased, so that the adsorption of other components may proceed. For this reason, the pressure of the exhaust gas G is set within a range where the equilibrium adsorption amount of the other component in the partial pressure of the other component becomes small.

  The configuration of the suction unit AD in FIG. 3 can be changed as appropriate according to the situation. For example, carbon dioxide having a concentration lower than a predetermined concentration released from the desorption side is changed to be temporarily collected in a storage container without being refluxed from the reflux path 21 to the flow path 3 and subjected to a separate separation process. May be. In addition, when the selective adsorption property to the carbon dioxide of the metal-organic structure to be used is relatively low, the carbon dioxide obtained by desorption cannot be obtained at a high concentration as shown in FIG. Using a plurality of pairs of adsorption towers composed of the first adsorption tower 2a and the second adsorption tower 2b, the separation process is performed again on the carbon dioxide recovered by the first separation process. Thus, the purity can be increased by concentrating or purifying carbon dioxide. Alternatively, a plurality of pairs of adsorption towers composed of the first adsorption tower 2a and the second adsorption tower 2b may be arranged in parallel to increase the exhaust gas treatment capacity.

  Further, the adsorbing part AD can also make changes related to fluctuations in the internal temperature of the adsorbent F due to adsorption and desorption. Specifically, a pipe for indirect heat exchange is arranged inside the adsorbent F in the first adsorbing tower 2a and the second adsorbing tower 2b, and a heat medium is circulated through the pipe, or a heat storage material is contained in the adsorbent F. The temperature fluctuation of the adsorbent F can be suppressed by heating or cooling with a heat medium, or heat absorption or heat release by a heat storage material. Alternatively, instead of arranging the piping inside the adsorbent F, it is also possible to provide a jacket that covers the outer periphery of the adsorption tower and to change the heating medium to flow through the jacket and to heat or cool from the outside. The adsorption unit AD configured as described above can cope with a rapid temperature fluctuation. For example, when applied to the purification of a relatively high concentration of carbon dioxide, the adsorbent F generated by vigorous heat generation during adsorption. Temperature rise can be suppressed from the inside.

  The configuration as described above can be further changed, for example, before supplying the exhaust gas G to the adsorption tower on the adsorption side, the flow path 4, so as to circulate through the heat exchange pipe or jacket on the desorption side. When the connection form 5 is changed, the exhaust gas G is cooled by the heat absorption of the adsorbent F in the desorption side adsorption tower, and then supplied to the adsorption side adsorbent F. That is, the exhaust gas G is used as a heat medium to be circulated through the heat exchange pipe in the adsorbent F or the jacket on the outer periphery of the adsorption tower, and the temperature decrease of the adsorbent during desorption can be suppressed while cooling the exhaust gas G. . Since the exhaust gas G is cooled by heat absorption on the desorption side, it may be possible to configure the cooler 7 to be omitted. By such a change, the temperature fluctuation inside the adsorbent F becomes small, and the temperature fluctuation inside the adsorbent F can be adjusted by the heat exchange efficiency in the heat exchange pipe or jacket. It can maintain suitably at 40 degreeC. Further, by utilizing adjustment of the temperature fluctuation range, it is possible to change / adjust the speed difference during adsorption / desorption of carbon dioxide in the adsorbent F.

  In the case where carbon dioxide is separated from a gas containing a high concentration of nitrogen and having a relatively low carbon dioxide concentration, an adsorbent that exhibits selective adsorptivity to nitrogen in advance, for example, a crystalline hydrous aluminosilicate alkaline earth You may change so that the pre-processing which raises the carbon dioxide concentration in gas by the adsorption process using metal salt (zeolite) etc. may be performed.

  The present invention efficiently produces carbon dioxide that is concentrated or purified to a high concentration by adsorbing and separating carbon dioxide contained in a mixed gas such as combustion exhaust gas and process exhaust gas by the PSA method. This is an economically advantageous technique because it does not require a means for generating pressure and can reduce the burden for imparting durability to the apparatus and reduce the energy required for operation. Therefore, it can be used for the treatment of carbon dioxide-containing gas discharged from combustion facilities such as thermal power plants, steelworks, boilers, etc., and it is useful for reducing the amount of carbon dioxide emission and the impact on the environment, and for energy saving and environmental protection. A carbon dioxide recovery device that can contribute can be provided.

1 recovery device, 2a first adsorption tower, 2b second adsorption tower, 3, 4, 5 flow path,
7 cooler, 8, 9, 10, 11, 13, 14 flow path,
6, 12, 15, 16, 17 selector valve, 18, 20 concentration sensor,
19, 23 Pressure control valve, 21 Return path, 24 Compressor, 25 Check valve,
26 Pressure gauge,
CL cooling section, DS desulfurization section, DH dehumidification section, PR pressurization section,
PV pressure control valve, EX heat exchange part, AD adsorption part, LQ liquefaction part,
WT water treatment section, L1-L9 flow path,
G exhaust gas, G ′ treated gas, C carbon dioxide, F adsorbent.

Claims (10)

A carbon dioxide recovery device having a separation device that separates carbon dioxide from gas using adsorption and desorption of carbon dioxide with respect to an adsorbent due to pressure fluctuation, wherein the separation device comprises:
An adsorbing part that contains an adsorbent having a metal-organic structure, adsorbs carbon dioxide contained in the gas by supplying gas, and adsorbs the released gas after treatment with reduced carbon dioxide;
A pressurizing unit that applies pressure to the gas so that the gas can be supplied to the adsorbing unit at a relatively high carbon dioxide partial pressure ;
A gas supply system capable of supplying gas adsorbed by the pressurizing unit to the adsorbing unit, and the adsorbing unit desorbs carbon dioxide from an adsorbent that has adsorbed carbon dioxide from the adsorbing unit. Pressure reducing means for reducing the pressure to a relatively low pressure for release, and a recovery system for recovering the desorbed carbon dioxide when the concentration of the desorbed carbon dioxide released from the adsorption unit is equal to or higher than a predetermined concentration. Have
The recovery system includes a flow path through which the desorbed carbon dioxide released from the adsorption unit circulates, a detector provided in the flow path for detecting the concentration of desorbed carbon dioxide, and the desorbed carbon dioxide as the gas. A reflux path branched from the flow path for supplying to the supply system, and when the concentration of carbon dioxide detected by the detector is equal to or higher than a predetermined concentration, the desorbed carbon dioxide is recovered, and the detector the concentration of carbon dioxide detected by the at less than a predetermined concentration, carbon dioxide recovery device for supplying the desorbed carbon dioxide from the return channel to the gas supply system. The pressure lowering means has a pressure control valve capable of releasing pressure from the gas to which pressure is applied, and the relative low pressure is set to atmospheric pressure or higher,
The carbon dioxide recovery device according to claim 1, wherein the separation device further includes a cooler that cools a gas supplied to the adsorption unit in advance and maintains the gas at a predetermined temperature or lower. The adsorption unit includes a pair of first adsorption tower and second adsorption tower, the adsorbent is accommodated in each of the first adsorption tower and the second adsorption tower, and the gas supply system includes: It can be supplied alternately gas granted the pressure by the pressing in one of the first adsorption tower and the second adsorption tower, one of the first adsorption tower and the second adsorption tower , The carbon dioxide contained in the pressure-applied gas is adsorbed to the adsorbent at a relatively high carbon dioxide partial pressure, and the treated gas having a reduced carbon dioxide concentration is alternately released, and the pressure drop The means alternately reduces the pressure on the other side of the first adsorption tower and the second adsorption tower where the gas is not supplied, and carbon dioxide is desorbed and released from the adsorbent at the pressure reduced to a relatively low pressure. The carbon dioxide according to claim 1 or 2. Osamu apparatus. The detector of the recovery system, the first to detect the adsorption tower and the concentration of the desorbed carbon dioxide is released alternately from the second adsorption tower, wherein the recovery system, the gas supply system by prior Symbol return path has a pressurizing圧装location for applying pressure to the carbon dioxide is supplied to, thereby, the desorbed carbon dioxide carbon dioxide recovery device according to claim 3 which is adsorbed by the adsorbent. The adsorbing part further includes
The gas supply destination is switched from the first adsorption tower to the second adsorption tower when the adsorbent of the first adsorption tower is broken, and the gas supply destination is the first when the adsorbent of the second adsorption tower is broken. The carbon dioxide recovery apparatus according to claim 3 or 4, further comprising: a control system that controls switching of a gas supply destination by the gas supply system so as to switch from a two adsorption tower to the first adsorption tower.   The control system has a detector that detects the concentration of carbon dioxide in the treated gas alternately discharged from the first adsorption tower and the second adsorption tower, and the concentration of carbon dioxide detected by the detector 6. The carbon dioxide recovery device according to claim 5, wherein control is performed based on the detected concentration of carbon dioxide so that the gas supply destination is switched when the carbon dioxide concentration of the supplied gas is reached. A cooling unit for cooling the gas, a desulfurization unit for removing sulfur oxide from the gas, and a dehumidifying unit having a hygroscopic agent for removing moisture from the gas;
A liquefying section that is disposed downstream of the separation device and compresses the recovered carbon dioxide to prepare liquefied carbon dioxide, and the separation device further comprises:
A heat exchanger for exchanging heat between the gas applied with pressure by the pressurizing unit and the treated gas released from the first adsorption tower and the second adsorption tower;
The carbon dioxide according to any one of claims 3 to 6, further comprising a flow path connected to the dehumidifying unit in order to use the treated gas that has passed through the heat exchanger for regeneration of the moisture absorbent of the dehumidifying unit. Recovery equipment. A method for recovering carbon dioxide having a separation process for separating carbon dioxide from a gas using adsorption and desorption of carbon dioxide with respect to an adsorbent due to pressure fluctuation, wherein the separation process includes:
Pressurizing treatment to apply pressure to the gas;
Using the gas subjected to the pressurization treatment, an adsorption treatment is performed in which the gas is brought into contact with the adsorbent having a metal-organic structure at a relatively high carbon dioxide partial pressure, and the carbon dioxide contained in the gas is adsorbed onto the adsorbent. When,
A desorption process that reduces the pressure to a relatively low pressure so as to desorb carbon dioxide from the adsorbent that has adsorbed carbon dioxide and release carbon dioxide;
It said desorbing process to detect the concentration of carbon dioxide desorbed is released by, dioxide concentration of carbon dioxide detected when the predetermined concentration or more, possess a recovery process for recovering the desorbed carbon dioxide, is detected when the concentration of carbon is less than a predetermined concentration, a method of recovering carbon dioxide supplying desorbed carbon dioxide to the adsorption treatment.   In the recovery process, the relative low pressure is set to be equal to or higher than the atmospheric pressure, and the pressure is reduced to a relatively low pressure by releasing the pressure using a pressure control valve. The separation process further includes a gas used in the adsorption process. The method for recovering carbon dioxide according to claim 8, further comprising a cooling process of cooling in advance and maintaining the temperature at a predetermined temperature or lower. The separation process is carried out using a first adsorption tower and a second adsorption tower each containing an adsorbent, and the adsorption process and the desorption process are:
Supplying a gas to the first adsorption tower to adsorb carbon dioxide at a relatively high carbon dioxide partial pressure, and adjusting the second adsorption tower to a relatively low pressure to desorb carbon dioxide;
A second process of supplying gas to the second adsorption tower to adsorb carbon dioxide at a relatively high partial pressure of carbon dioxide and adjusting the first adsorption tower to a relatively low pressure to desorb carbon dioxide; The separation process is further carried out by switching from the first process to the second process when the adsorbent of the first adsorption tower is broken in the first process, and in the second process, the separation process of the second adsorption tower is performed. A switching operation for switching from the second process to the first process when the adsorbent breaks; in the recovery process, the second adsorption tower or the first adsorption in each of the first process and the second process; The method for recovering carbon dioxide according to claim 8 or 9, wherein the carbon dioxide released is recovered when the concentration of carbon dioxide released from the tower is equal to or higher than a predetermined concentration.

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