JP2014213275A - Recovery method and recovery device of carbon dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method and a recovery device of carbon dioxide which can reduce operation cost by reducing energy necessary to regenerate an absorbent.SOLUTION: An absorption tower and a regeneration tower of a recovery device are structured by two stages or more. Gas is supplied to a second absorption part through a first absorption part of the absorption tower. A first regeneration part of the regeneration tower includes external heating means, and a second regeneration part is heated by heat of gas emitted from the first regeneration part. Recovery gas discharged from the regeneration tower is compressed by a compressor, heat of the recovery gas is recovered by a heat recovery system and is supplied to the regeneration tower, and condensed water of the recovery gas is separated by a gas-liquid separator. A circulation system of the absorbent includes a first circulation system for circulating the first absorption part and the second regeneration part, and a second circulation system for circulating the second absorption part and the first regeneration part, and supplies water in the gas-liquid separator to the absorbent refluxed from the first regeneration part to the second absorption part.

Description

  The present invention relates to a carbon dioxide recovery method and recovery device for separating and recovering carbon dioxide from a gas containing carbon dioxide such as combustion gas and reducing clean gas to the atmosphere.

  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 the 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 advanced. As a carbon dioxide recovery method, for example, PSA ( Known are pressure swinging), membrane separation and concentration, and chemical absorption using reaction absorption by basic compounds.

  In the chemical absorption method, mainly alkanolamine-based basic compounds are used as the absorbent. In the treatment process, an aqueous liquid containing the absorbent is generally used as the absorbent, and carbon dioxide contained in the gas is absorbed into the absorbent. The absorbing solution is circulated so as to alternately repeat the absorbing step to be performed and the regeneration step of regenerating the absorbing solution by releasing the absorbed carbon dioxide from the absorbing solution (see, for example, Patent Document 1 below). In the regeneration process, heating for releasing carbon dioxide is necessary, and in order to reduce the operating cost of carbon dioxide recovery, it is important to reduce the energy required for heating / cooling for regeneration. In this regard, as shown in Patent Document 1, heat exchange of a high-temperature absorption liquid (lean liquid) from which carbon dioxide has been released in the regeneration process is performed with an absorption liquid (rich liquid) that has absorbed carbon dioxide in the absorption process. Thus, thermal energy can be recovered and reused in the regeneration process.

  In addition, since the gas containing carbon dioxide discharged from the regeneration process contains heat energy that can be recovered and used, in Patent Document 2 below, for the purpose of recovery, the carbon dioxide discharged from the regeneration tower is included. Using a compressor that compresses the gas and a heat exchanger that performs heat exchange of the gas discharged from the compressor, the absorption liquid held in the regeneration tower is supplied to the heat exchanger and heated by heat exchange with the gas. To return to the regeneration tower.

JP 2009-214089 A JP 2010-235395 A

  The energy required to regenerate the absorption liquid is to compensate for the sensible heat required to raise the temperature of the absorption liquid, the heat of reaction when carbon dioxide is released from the absorption liquid, and the heat loss due to moisture evaporation of the absorption liquid. There is latent heat. In the above-described prior art, thermal energy related to these is recovered, but there is still room for improvement in the recovery and reuse of energy related to latent heat.

  In order to promote the capture of carbon dioxide for environmental conservation, it is desirable from the economic point of view to increase the energy efficiency as much as possible to reduce the cost required for the recovery, and increase the recovery efficiency of thermal energy from the absorbent. This is important for energy saving, and can also effectively affect the carbon dioxide recovery efficiency.

  An object of the present invention is to provide a carbon dioxide recovery method and a recovery apparatus that can solve the above-described problems and reduce the energy required for regenerating the absorbing liquid to reduce the operating cost.

  Another object of the present invention is to reduce the burden on the apparatus and the absorption liquid, reduce the energy required for regeneration of the absorption liquid without reducing the carbon dioxide recovery rate, and reduce the carbon dioxide recovery cost. 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. As a result, it is effective to reduce the amount of water vapor contained in the recovered carbon dioxide in order to easily recover sufficient heat energy related to latent heat. The inventors have found that it is advantageous in the apparatus configuration to use the configuration in which the absorption process and the regeneration process are each divided into at least two stages, and the present invention has been completed.

  According to one aspect of the present invention, the carbon dioxide recovery device is an absorption tower that causes a gas to contact the absorption liquid and absorbs the carbon dioxide contained in the gas into the absorption liquid. The absorption tower disposed so as to be supplied to the second absorption section through the first absorption section, and the absorption liquid that has absorbed carbon dioxide in the absorption tower. A regeneration tower for heating and releasing carbon dioxide to regenerate the absorbing solution, comprising a first regeneration unit and a second regeneration unit, wherein the first regeneration unit has an external heating means, and the second regeneration A part circulates the absorbing liquid between the regeneration tower disposed so as to be heated by the heat of the gas released from the first regeneration part, and the first absorption part and the second regeneration part. Circulating the absorption liquid between the first circulation system, the second absorption part and the first regeneration part; A circulation system having a second circulation system, a compressor that compresses the recovered gas containing water vapor and carbon dioxide discharged from the regeneration tower as it is, and recovers the heat of the recovered gas compressed by the compressor. And a heat recovery system for supplying the regeneration tower.

  The recovery device further includes a gas-liquid separator that separates water condensed from the recovered gas from which heat has been recovered by the heat recovery system, and reflux from the first regeneration unit to the second absorption unit in the second circulation system. It is preferable to have a water supply path for supplying the water separated in the gas-liquid separator to the absorbing liquid.

  Moreover, according to one aspect of the present invention, the method for recovering carbon dioxide is an absorption process in which a gas is brought into contact with an absorption liquid and the carbon dioxide contained in the gas is absorbed into the absorption liquid. And a second absorption step, wherein the gas is supplied to the second absorption step through the first absorption step, and the absorption liquid that has absorbed carbon dioxide in the absorption treatment is heated to generate carbon dioxide. A regeneration process for regenerating the absorbing liquid by discharging, comprising a first regeneration process and a second regeneration process, wherein heating is performed using an external heating means in the first regeneration process, and in the second regeneration process The regeneration process for heating by the heat of the gas released in the first regeneration process, the first circulation process for circulating the absorbent between the first absorption process and the second regeneration process, and the second Between the absorption process and the first regeneration process A second circulation step for circulating the absorbent, a compression step for compressing the recovered gas containing water vapor and carbon dioxide discharged from the regeneration process, and recovering the heat of the recovered gas compressed by the compression step. And a heat recovery step for supplying to the regeneration process.

  The recovery method further includes a separation step of separating water condensed from the recovered gas after the heat recovery step, and an absorption liquid circulated from the first regeneration step to the second absorption step in the second circulation step. And a water supply step for supplying water separated in the separation step.

  According to the present invention, in the process of recovering carbon dioxide contained in gas, the recovery efficiency of heat used for regeneration of the absorbing liquid is improved, and the thermal energy required for regeneration is reduced without reducing the recovery rate of carbon dioxide. Therefore, it is possible to provide a carbon dioxide recovery method and a recovery device that are effective in reducing operation costs. Absorption liquid concentration correction using condensed water obtained from recovered gas can be performed in a form that is advantageous for temperature adjustment, and carbon dioxide recovery and absorption liquid regeneration can be performed efficiently. Since the load upon regeneration with respect to the liquid is reduced and the absorbing liquid can be used efficiently and stably, it is effective in reducing the operating cost and the equipment maintenance cost. It is economically advantageous because it can be carried out easily using general equipment without requiring special equipment or expensive equipment.

1 is a schematic configuration diagram showing a first embodiment of a carbon dioxide recovery apparatus according to the present invention. The schematic block diagram which shows 2nd Embodiment of the collection | recovery apparatus of the carbon dioxide which concerns on this invention. The schematic block diagram which shows 3rd Embodiment of the collection | recovery apparatus of the carbon dioxide which concerns on this invention. The schematic block diagram which shows 4th Embodiment of the collection | recovery apparatus of the carbon dioxide which concerns on this invention.

  In the absorption process of carbon dioxide by the chemical absorption method, absorption treatment that absorbs carbon dioxide contained in the gas into a low-temperature absorption liquid and high-temperature regeneration that regenerates the absorption liquid by releasing the absorbed carbon dioxide from the absorption liquid The absorption liquid is circulated between the treatments, and the absorption treatment and the regeneration treatment are alternately repeated. The regeneration rate of the absorbent in the regeneration process depends on the heating temperature of the absorbent. The higher the temperature, the more carbon dioxide gas is released and the residual carbon dioxide concentration in the absorbent becomes lower (see: Jong I. Lee, Frederick D. Otto and Alan E. Mather, “Equilibrium Between carbon Dioxide and Aqueous Monoethanolamine Solutions”, J. appl. Chem. Biotechnol. 1976, 26, PP541-549). Therefore, normally, the absorbing liquid in the regeneration process is maintained near the boiling temperature by external heating means using thermal energy supplied from an external heat source. The high-temperature regenerated absorbent (lean liquid) that has released carbon dioxide in the regeneration process exchanges heat with the absorbent (rich liquid) that has absorbed carbon dioxide in the absorption process, so that the heated rich liquid is supplied to the regenerative process. Heat energy is recovered and reused. However, the gas containing carbon dioxide released from the absorbing solution in the regeneration process is discharged in a high temperature state including the heat, and the amount of heat contained in the exhaust gas is wasted. The temperature of the exhaust gas can be lowered, that is, the temperature at the top of the regeneration tower can be lowered by lowering the heat exchange rate between the rich liquid and the lean liquid, but the sensible heat recovered in the heat exchange is reduced. Therefore, it does not contribute to the reduction of heat.

  In the present invention, the absorption process and the regeneration process are each divided into at least two stages to constitute two sets of absorption process and regeneration process, and the circulation path for circulating the absorbent is also separated into two independent paths. The absorbent is configured to be circulated individually between the pair of absorption processes and the regeneration process. In one regeneration process, the absorbing liquid is positively heated by an external heating means using an external energy source. The high-temperature gas released in this process is supplied to another regeneration process and becomes a heat source. The absorbent is regenerated by heating. That is, the heat recovered from the gas is directly used for the regeneration of the absorbent. Further, the exhaust gas from the regeneration tower is compressed, and a heat exchanger for recovering the released heat energy is introduced, and the recovered heat energy is supplied to the regeneration tower, thereby being supplied from an external heat source. The use efficiency of thermal energy becomes much higher. At this time, since water is condensed from the exhaust gas from which the thermal energy has been recovered, this condensed water is supplied to the absorbent and used for adjusting the concentration of the absorbent. As described above, the configuration in which the absorption liquid used in the absorption tower and the regeneration tower is circulated by two independent paths is such that the water vapor evaporated from the absorption liquid moves from one path to the other path, However, the use of condensed water separated from the exhaust gas is advantageous as a means for effectively solving this problem. In addition, the absorbent (amine compound) can be mixed into the exhaust gas from the regeneration tower. However, since the top temperature of the regeneration tower is lowered by dividing the regeneration tower into two stages, the amount of absorbent mixed in is greatly reduced. To do. This point is also advantageous in that the compressor for compressing the exhaust gas and the sealing material for the device connection portion are less susceptible to corrosion due to contaminants in the gas.

  In the above configuration, the absorption liquid circulating through the two sets of paths can be individually selected, and can be adjusted to characteristics suitable for the processing conditions of each path, and prepared in different compositions. It is also possible to use two types of absorbents. In general, it is difficult to develop an absorbent that is excellent in both absorption and regenerative properties, and it is generally excellent in either one. In the configuration in which the liquid can be used, the energy required for regeneration can be reduced while avoiding a decrease in absorption efficiency and regeneration efficiency by selecting and using an absorption liquid specialized for the processing conditions of the absorption process and regeneration process of each circulation system. Reduction can be advantageously promoted.

  Hereinafter, the carbon dioxide recovery method and recovery apparatus of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment of the carbon dioxide recovery apparatus of the present invention. The recovery device 1 is configured to bring the gas G containing carbon dioxide into contact with the absorption liquid and absorb the carbon dioxide into the absorption liquid, and heat the absorption liquid that has absorbed the carbon dioxide to release the carbon dioxide from the absorption liquid. And a regeneration tower 20 for regenerating the absorbent. There is no restriction | limiting in particular about the gas G supplied to the collection | recovery apparatus 1, Handling of various gas, such as combustion exhaust gas and process exhaust gas, is possible. The absorption tower 10 and the regeneration tower 20 are each configured as a countercurrent gas-liquid contact device, and are filled with fillers 11 and 21 for increasing the contact area. As the absorbing liquid, an aqueous liquid containing a compound having an affinity for carbon dioxide such as alkanolamines as an absorbent is used. The fillers 11 and 21 are made of a material having durability at a processing temperature and corrosion resistance, and can be appropriately selected and used in a shape capable of providing a desired contact area. Although those made of an iron-based metal material such as steel are used, it is not particularly limited. Furthermore, if necessary, a cooling tower for maintaining the gas G supplied to the absorption tower 10 at a low temperature suitable for carbon dioxide absorption may be provided.

  The gas G containing carbon dioxide is supplied from the lower part of the absorption tower 10. The inside of the absorption tower 10 is partitioned into a lower first absorption part 12a in which the filler 11a is accommodated and an upper second absorption part 12b in which the filler 11b is accommodated, and the first absorption part 12a and the second absorption part 12b. A partition member 13 having a tubular wall standing on the periphery of the central hole of the horizontal annular plate is interposed between the absorber 12b and a shade covering the upper end hole of the tubular wall of the partition member 13 so that the absorption tower 10 A liquid pool is formed on the horizontal annular plate between the inner wall of the partition member 13 and the tubular wall of the partition member 13. The gas G supplied from the lower part of the absorption tower 10 rises in the tower, passes through the filler 11a of the first absorption part 12a, and then fills the second absorption part 12b through the tubular wall inner hole of the partition member 13. It passes through the material 11b. On the other hand, the absorption liquid is divided into two parts, a first absorption liquid and a second absorption liquid. The first absorption liquid is supplied to the upper part of the first absorption part 12a of the absorption tower 10 and flows down the filler 11a, and then the absorption tower. 10 is stored at the bottom, and the second absorption liquid is supplied to the upper part of the second absorption part 12b of the absorption tower 10, and after flowing down the filler 11b, is stored in the liquid reservoir of the partition member 13 and is stored in the first absorption part 12a. Is configured to be led out of the tower without flowing down. While the gas G passes through the fillers 11a and 11b, the two absorbing liquids are sequentially brought into gas-liquid contact, and the carbon dioxide in the gas G is absorbed by the absorbing liquid. Since the carbon dioxide concentration of the gas after passing through the first absorption portion 12a is lowered, the second absorption liquid comes into contact with a gas having a lower carbon dioxide concentration than the gas G with which the first absorption liquid comes into contact. The first absorption liquid (rich liquid) A1 ′ that has absorbed carbon dioxide in the first absorption section 12a is stored at the bottom of the absorption tower 10 and is connected to the bottom of the absorption tower 10 and the top of the regeneration tower 20 by the pump 14. It is supplied to the regeneration tower 20 through the supply path 15. The second absorption liquid (rich liquid) A2 ′ that has absorbed carbon dioxide in the second absorption section 12b is stored in the liquid pool of the partition member 13, and the central portion of the absorption tower 10 and the regeneration tower 20 are separated by the pump 16. It is supplied to the regeneration tower 20 through the connected second supply path 17. The gas G ′ from which carbon dioxide has been removed is discharged from the top of the absorption tower 10.

  The absorption liquid absorbs carbon dioxide to generate heat and the liquid temperature rises. Therefore, if necessary, a cooling condensing unit 18 for condensing water vapor or the like that can be contained in the gas G ′ is provided at the top of the absorption tower 10. Thereby, it can suppress to some extent that water vapor | steam etc. leak out of a tower. In order to further ensure this, there is a cooler 31 and a pump 32 attached outside the absorption tower, and a part of the condensed water stored under the cooling condensing unit 18 (including the gas G ′ in the tower). Is good) is circulated between the cooler 31 and the pump 32. Condensed water or the like cooled by the cooler 31 and supplied to the top of the tower maintains the cooling condensing unit 18 at a low temperature and reliably cools the gas G ′ passing through the cooling condensing unit 18. The drive of the pump 32 is controlled so that the temperature of the gas G ′ discharged to the outside of the tower is preferably about 60 ° C. or less, more preferably 45 ° C. or less. In the configuration of FIG. 1, the water condensed in the cooling condensing unit 18 is supplied to the packing material 11b, but the condensed water can be used to compensate for the composition variation of the absorption liquid in the tower, so the first is necessary. And it is good to comprise so that concentration composition of the 2nd absorption liquid may be detected and condensed water may be distributed according to the rate of concentration fluctuation, and supplied to fillers 11a and 11b, and supply of condensed water in cooling condensation part 18 is It can be set and changed as appropriate in consideration of compensation by condensed water in the regeneration tower 20 described later.

  The regeneration tower 20 is partitioned into a lower first regeneration unit 22a in which the filler 21a is accommodated and an upper second regeneration unit 22b in which the filler 21b is accommodated, and the first regeneration unit 22a and the second regeneration unit 22b. A partition member 23 that forms a liquid pool with a structure similar to that of the partition member 13 is interposed between the regenerator 22b. The first absorbing liquid A1 ′ supplied from the bottom of the absorption tower 10 through the first supply path 15 is introduced into the upper part of the second regeneration section 22b of the regeneration tower 20 and flows down through the packing material 21b, and then pools in the partition member 23. And is led out of the tower without flowing down to the first regeneration unit 22a. The second absorption liquid A2 ′ supplied from the second absorption part 12b of the absorption tower 10 through the second supply path 17 is supplied to the upper part of the first regeneration part 22a, and flows down the filler 21a and then flows into the bottom part of the regeneration tower 20. Stored.

  A reboiler is attached to the bottom of the regeneration tower 20 as an external heating means for positively heating the absorption liquid using externally supplied energy. That is, a steam heater 24 attached outside the regeneration tower 20 and a circulation path 25 for circulating the second absorbent A2 stored in the tower bottom through the steam heater 24 are attached, and the second absorbent at the bottom of the tower is added. A part of A2 is diverted to the steam heater 24 through the circulation path 25, continuously heated by heat exchange with high-temperature steam, and refluxed into the tower. Accordingly, the second absorbing liquid A2 at the bottom is actively heated to sufficiently release carbon dioxide, and the filler 21a is also indirectly heated to cause carbon dioxide by gas-liquid contact on the filler 21a. Release is accelerated. The high temperature gas containing carbon dioxide and water vapor released from the second absorbing liquid rises and passes through the filler 21a of the first regeneration unit 22a, and then passes through the tubular wall inner hole of the partition member 23 for the second regeneration. It passes through the filler 21b of the part 22b. During this time, the second absorbing liquid A2 'flowing down the filler 21a and the first absorbing liquid A1' flowing down the filler 21b are heated, and carbon dioxide in these absorbing liquids is released. The first absorbing liquid A1 ′ supplied to the second regeneration unit 22b is not actively heated by the external heating means, and is heated only by the heat of the gas released from the first regeneration unit 22a. 2 lower than the absorption liquid A2 ′. Therefore, when the first absorption liquid and the second absorption liquid have the same composition, the regeneration degree of the first absorption liquid A1 in the pool of the partition member 23 is lower than the regeneration degree of the second absorption liquid A2 at the bottom of the column. It becomes semi-lean liquid. The first absorption liquid A1 from which carbon dioxide has been released is supplied to the first absorption tower 10 through the first reflux path 27 that connects the central portion of the regeneration tower 20 and the central portion of the absorption tower 10 by the pump 26 from the pool of the partition member 23. It is refluxed to the upper part of the absorption part 12a. The second absorption liquid A2 (lean liquid) that has been stored at the bottom of the regeneration tower 20 and has sufficiently released carbon dioxide is absorbed by the pump 28 through the second reflux path 29 that connects the top of the absorption tower 10 and the bottom of the regeneration tower 20. It is refluxed to the upper part of the second absorption part 12b of the tower 10. As a result, a first circulation system in which the first absorption liquids A1 and A1 ′ reciprocate between the first absorption unit 12a and the second regeneration unit 22b is configured by the first supply path 15 and the first return path 27. A second circulation system in which the second absorption liquids A2 and A2 ′ reciprocate between the second absorption unit 12b and the first regeneration unit 22a is configured by the second supply path 17 and the second reflux path 29. The gas containing carbon dioxide released from the absorbent in the regeneration tower 20 is discharged from the top of the regeneration tower 20.

  The first absorbing liquid A1 from which the carbon dioxide has been released by the second regeneration unit 22b passes through the first heat exchanger 33 while refluxing the first reflux path 27. Since the first heat exchanger 33 is installed so as to exchange heat between the first supply path 15 and the first reflux path 27, the first absorption liquid A <b> 1 is absorbed in the first absorption path 15 in the first supply path 15. After being cooled by the liquid A1 ′ and further sufficiently cooled to a temperature suitable for absorption of carbon dioxide by the cooler 35 using cooling water, it is introduced into the upper part of the first absorption part 12a. Further, the second absorbent A2 from which the carbon dioxide has been released by the first regeneration unit 22a passes through the second heat exchanger 34 while flowing through the second reflux path 29. Since the second heat exchanger 34 is installed so as to exchange heat between the second supply path 17 and the second reflux path 29, the second absorption liquid A <b> 2 is absorbed by the second absorption path 17 in the second supply path 17. After being cooled by the liquid A2 ′ and further sufficiently cooled in the same manner by the cooler 36 using cooling water, it is introduced into the upper part of the second absorption part 12b. There are various types of heat exchangers such as spiral type, plate type, double pipe type, multiple cylinder type, multiple circular pipe type, spiral tube type, spiral plate type, tank coil type, tank jacket type, direct contact liquid type, etc. There are various types, and any type may be used as the first and second heat exchangers 33 and 34 in the present invention, but the plate type is superior in terms of simplification of the apparatus and ease of cleaning and disassembly.

  The recovered gas C containing carbon dioxide released from the absorbing liquid by heating in the regeneration tower 20 passes through a condensing part 37 provided at the upper part of the regeneration tower 20 in order to suppress the release of water vapor and absorbent, and then exhausted from the top. It is discharged through the tube 38. In the present invention, in order to recover and reuse heat from the recovered gas C discharged from the regeneration tower 20, the regeneration tower 20 has a heat recovery system by compression and heat exchange, and in order to increase heat recovery efficiency. The recovered gas C discharged from the gas is compressed as it is without undergoing condensation separation of water vapor by cooling. Both the heat of gas compression generated by this compression and the heat of condensation of water are collected and reused. Specifically, the recovery apparatus 1 shunts a part of the second absorbing liquid A2 at the bottom of the regeneration tower 20 by dividing the compressor 40 provided on the exhaust pipe 38 so as to directly communicate with the regeneration tower 20 and outside the regeneration tower. And a heat exchanger 41 installed so as to exchange heat between the recovered gas C compressed by the compressor 40 and the second absorbent A2 in the circulation path 50. Have In the heat exchange, the water vapor contained in the recovered gas C is cooled and condensed to release the heat of condensation. Therefore, in the heat exchanger 41, the heat of condensation of water is recovered together with the heat of compression. For the heat exchange between the recovered gas C and the absorption liquid, various heat exchangers generally used for gas-liquid heat exchange can be appropriately selected and used. For example, direct contact type, fin tube type, plate A heat exchanger such as an equation is mentioned. In the regeneration tower 20 of the present invention, the regeneration section is configured in two stages, and the top temperature of the regeneration tower 20 is lower than in the case of the one-stage structure. Is properly prevented. Therefore, this is a preferable configuration from the viewpoint of preventing corrosion of the compressor 40 and the sealing material of the connection portion. The second absorbent A2 after heat exchange by the heat exchanger 41 is refluxed to the bottom of the regeneration tower 20. That is, the heat recovered from the recovered gas C is supplied to the first regeneration unit 22a of the regeneration tower 20 via the second absorption liquid A2. In this embodiment, the second absorbent A2 after heat exchange is directly refluxed to the regeneration tower 20, but the circulation path 50 may be connected so as to be refluxed to the regeneration tower 20 via the steam heater 24. Good.

  The recovered gas C that has undergone heat recovery by the heat recovery system is sufficiently cooled by the cooler 42 that uses cooling water, condenses water vapor as much as possible, and then the condensed water is removed by the gas-liquid separator 43. Collected. Carbon dioxide in the recovered gas C can be fixed and reorganized in the ground by, for example, injecting it into the ground or an oil field. The pressure of the recovered gas C by the compressor 40 can be effectively used, for example, as a working pressure such as an injection pressure in the processing of recovered carbon dioxide.

  The gas / liquid separator 43 is connected to the downstream side of the cooler 36 of the second reflux path 29 by a water supply path 45 having a pressure reducing valve 44 provided as a pressure reducing means for releasing the applied pressure. The separated condensed water is depressurized and adjusted to a pressure suitable for introduction into the absorption tower 10 by the pressure reducing valve 44 and added to the second absorbent A2 in the second reflux path 29 from the water supply path 45, and the absorption tower. 10 is recirculated to the upper part of the second absorption part 12b. That is, the condensed water is used to compensate for the composition variation of the second absorbent A2 supplied to the absorption tower 10. As the pressure reducing valve 44, for example, what is generally used as a pressure adjusting valve or a back pressure valve may be used.

  A pressure gauge 46 is connected to the exhaust pipe 38 in order to detect the pressure in the regeneration tower 20, and the output of the motor 40M of the compressor 40 is controlled in accordance with the detected pressure value. The operation of the compressor 40 is adjusted so as to maintain a constant pressure (the connection indicated by a broken line in the figure indicates an electrical connection). In the control of the motor 40M, for example, if output control using an inverter or the like is used, energy efficiency is good.

  In the above-described embodiment, the pressure release and adjustment of the condensed water can be changed by using an expander instead of the pressure reducing valve 44. In this case, the expander and the compressor 40 are coaxial rotors. If it is configured as a heat pump that cooperates to drive, the operating efficiency is improved. Alternatively, it is possible to reduce the flow condensate using an ejector, or to recover the power energy from the flow pressure of the pressurized condensate using a turbine or the like and use it for driving the compressor. Can be improved. Further, the above-described embodiment can be modified to increase the amount of recovered heat using a plurality of sets of compressors and heat exchangers. That is, the recovered gas C that has passed through the heat exchanger 41 is connected in series on the exhaust pipe 38 so as to pass through the second set of compressors and heat exchangers before reaching the cooler 42 for compression and heat exchange. By repeating again, the heat recovery amount is increased by the amount of heat exchange in the second heat exchanger. If necessary, three or more sets of compressors and heat exchangers can be installed, and the combination of multi-stage compression and heat exchange can be repeated as appropriate. In such a multi-stage heat exchange, the circulation path 50 may be branched so that the absorption liquid exchanges heat in parallel, or the flow of the absorption liquid faces the flow of the recovered gas C in series. You may comprise so that it may pass through a heat exchanger. In addition, it is more preferable to arrange a gas-liquid separator so as to separate condensed water from the recovered gas for each heat recovery by each heat exchanger.

  In the regeneration tower 20, the temperature of the second absorbent A2 heated at the bottom of the first regenerator 22a is T1, and the second absorbent A2 ′ introduced from the second heat exchanger 34 to the top of the first regenerator 22a. If T2 is T2, then T1> T2. Further, the temperature of the first absorbing liquid A1 in the liquid pool heated in the second regeneration unit 22b by the gas released from the first regeneration unit 22a is set to T3, and is introduced from the first heat exchanger 33 to the second regeneration unit 22b. When the temperature of the first absorbing liquid A1 ′ is T4, the temperature of the gas released from the first regeneration unit 22a to the second regeneration unit 22b is t1, and the temperature of the gas released from the second regeneration unit 22b is t2. , T1> T3> T4 and t1> t2. In general, the absorption liquid in the regeneration tower is heated in the vicinity of the boiling point of the absorption liquid in order to increase the degree of regeneration, and the heat difference is increased by using a heat exchanger having a high heat exchange performance to increase the temperature difference (T1-T2). When becomes smaller, the temperature t1 of the gas released from the first regeneration unit 22a also becomes higher. If this gas is discharged from the regeneration tower 20 as it is, not only energy for sensible heat will be released, but also a large amount of energy for latent heat will be released together with water vapor. The amount of heat released from the gas is recovered in the second regeneration unit 22b and used for regeneration of the absorbent, and the temperature of the gas is lowered from t1 to t2 to reduce the amount of sensible heat released. As the temperature decreases, the condensation of the water vapor also proceeds, so that the water vapor and latent heat contained in the gas released from the second regeneration unit 22b also decrease. In the above-described configuration, the condensed water vapor evaporated from the absorption liquid is converted into the second absorption liquids A2 and A2 ′ of the second absorption section 12b in the absorption tower 10 and the second regeneration section 22b in the regeneration tower 20. However, since the amount of vaporized water from the second absorbing liquid A2 in the first regeneration unit 22a tends to exceed the amount of condensed water supplemented in the second absorbing unit 12b, It is useful to use the condensed water of the gas-liquid separator 43 as dilution water for suppressing an increase in the concentration of the two absorbents. In addition, when using the 1st absorption liquid and the 2nd absorption liquid of the same composition, in order to equalize the density | concentration of a 1st absorption liquid and a 2nd absorption liquid when the density | concentration fluctuation | variation by vaporization is large, A part of the second liquid may be mixed with the second absorbent, or a part of the second liquid may be mixed with the first absorbent. In this case, the energy loss caused by the partial mixing of the absorbing liquid can be reduced by adjusting the operating conditions (such as the circulating amount of the absorbing liquid), and the first absorbing liquid A1 after regeneration and the second absorbing liquid A2 after absorption. It is advisable to adjust the operating conditions so that the carbon dioxide concentration of 'is approximately the same and mix the absorbent.

  The collection method implemented by the operation of the collection apparatus 1 in FIG. 1 will be described.

  In the absorption tower 10, a gas G containing carbon dioxide such as combustion exhaust gas or process exhaust gas is supplied from the bottom, and the pumps 14, 16, 26, 28 are driven to circulate the first and second absorption liquids A1, A2. (First and second circulation step) When supplied from the upper part of the first and second absorption parts 12a and 12b, respectively, the gas G and the first and second absorption liquids A1 and A2 on the fillers 11a and 11b Is in gas-liquid contact, and an absorption process (first and second absorption steps) in which carbon dioxide is absorbed by the absorption liquid proceeds. Since carbon dioxide is well absorbed at a low temperature, the liquid temperature of the absorbing liquids A1 and A2 or the temperature of the absorption tower 10 (particularly the packing materials 11a and 11b) is generally about 50 ° C. or lower, preferably 40 ° C. or lower. Adjust. Since the absorbing liquid generates heat due to absorption of carbon dioxide, it is desirable to take into consideration the increase in liquid temperature caused by this, so that the liquid temperature does not exceed 60 ° C. The gas G supplied to the absorption tower 10 may be adjusted in advance to an appropriate temperature using a cooling tower as necessary in consideration of the above. As the first and second absorbing liquids A1 and A2, aqueous liquids containing a compound having affinity for carbon dioxide as an absorbent are used. Examples of the absorbent include alkanolamines and hindered amines having an alcoholic hydroxyl group. Specific examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine (MDEA), Examples of the hindered amine having an alcoholic hydroxyl group include 2-amino-2-methyl-1-propanol (AMP), 2- (ethylamino) ethanol (EAE), and the like. Examples include 2- (methylamino) ethanol (MAE), and a plurality of the above compounds may be used in combination. The absorbent concentration of the absorbing liquid can be appropriately set according to the amount of carbon dioxide contained in the gas to be processed, the processing speed, the fluidity of the absorbing liquid, the suppression of consumption loss, and the like. For example, for treatment of gas G having a carbon dioxide content of about 20%, an absorbing solution having a concentration of about 30% by mass is preferably used.

  In the present invention, it is also possible to use the same absorption liquid containing the same absorbent as the first and second absorbents A1 and A2, or 1) an absorbent having a different absorbent concentration and 2) an absorbent. It is also possible to use absorption liquids with different types and composition ratios. For example, in the form of 1), by setting the absorbent concentration of the second absorbent A2 having a relatively high heating temperature in the regeneration tower 20 to be lower than that of the first absorbent, the first regeneration unit 22a (first The heat absorption of the second absorbent A2 in the first regeneration step) is suppressed to increase the heat resistance, and the first absorbent A1 can increase the absorption capacity. It is possible to select and use one having good absorbability and reproducibility (reproducibility). In the form 2), the carbon dioxide concentration of the gas processed in the first absorption unit 12a (first absorption step) is higher than that of the second absorption unit 12b (second absorption step), and the carbon dioxide is easily absorbed. Therefore, priority is given to the regenerative property of the absorbent for the first absorbent A1, and priority is given to the absorbability for the second absorbent A2 that is in contact with the second absorbent 12b where the carbon dioxide concentration of the gas is relatively low. By selecting the absorbent, it is possible to easily regenerate the absorbing liquid without reducing the absorption efficiency as a whole, and to reduce the energy required for the regeneration. By using an absorbent having a good regenerative property as the first absorbent A1, the degree of regeneration at a lower temperature in the second regeneration unit 22b (second regeneration step) is increased, and the absorbent recirculates to the first absorption unit 12a. Can be brought close to the lean solution. Monoethanolamine (MEA), which is generally preferred for use, is an absorbent having high absorbability, and examples of the absorbent having good regenerative properties include AMP and MDEA. Often, for the purpose of improving the absorption of AMP and MDEA, MEA is mixed to form an absorption liquid. However, the absorption and regeneration can be adjusted to some extent depending on the mixing ratio. If the 1st and 2nd absorption liquid is prepared using, the absorption process and the regeneration process can be efficiently implemented using the characteristic of each absorption liquid. For example, an absorbent solution having a relatively high concentration of MDEA or AMP is used as the first absorbent solution A1, and an absorbent solution having a relatively high MEA concentration and a high absorbability is used as the second absorbent solution A2. Is preferable in terms of reducing the regenerative energy.

  The supply speed of the gas G and the circulation speed of the first and second absorption liquids are determined in consideration of the amount of carbon dioxide contained in the gas G, the carbon dioxide absorption capacity of the absorption liquid, the gas-liquid contact efficiency in the filler, and the like. It is set as appropriate so as to proceed well. The absorption process / regeneration process is repeatedly executed by circulation of each absorption liquid.

  The second absorption liquid A2 ′ that has absorbed carbon dioxide is supplied from the second supply path 17 to the first regeneration unit 22a, and during this time, is heated by heat exchange with the second absorption liquid A2 that is refluxed from the regeneration tower 20. (Second heat exchange step). The temperature T1 of the second absorbent A2 heated by external heat in the first regeneration unit 22a varies depending on the composition of the absorbent used and the regeneration conditions, but is generally set to about 100 to 130 ° C. (near the boiling point). Based on this, the outlet temperature of the second heat exchanger 34 of the second absorbing liquid A2 ′, that is, the introduction temperature T2 to the first regeneration unit 22a can be about 90 to 125 ° C. The temperature t1 of the gas released from the first regeneration unit 22a to the second regeneration unit 22b is about 85 to 115 ° C., and is heated by the second regeneration unit 22b by the gas released from the first regeneration unit 22a. The temperature T3 of the first absorbing liquid A1 is about 85 to 115 ° C. The temperature T4 of the first absorbent A1 'introduced into the second regeneration unit 22b by the heat exchange (first heat exchange step) in the first heat exchanger 33 can be about 80 to 110 ° C. The temperature t2 of the gas released from the second regeneration unit 22b can be lowered to 100 ° C. or lower.

  By performing regeneration at a temperature lower than that of the first regeneration unit 22a in the second regeneration unit 22b, the temperature t2 at the top of the regeneration tower 20 can be lowered to a temperature close to the temperature T4 of the first absorbent A1 ′ to be charged. (T2 <t1, T4 <T3 <t1). Therefore, the absorbent contained in the recovered gas passing through the condensing part 37 is reduced, and corrosion of the equipment and materials provided in the exhaust pipe 38 by the absorbent can be prevented. In order to advance the regeneration of the absorbing solution at a low temperature, it is important that the carbon dioxide content of the absorbing solution is high, but the first absorbing solution that contacts the gas having a high carbon dioxide concentration in the first absorbing portion 12a is: Since the carbon dioxide content tends to be relatively high, it is convenient to perform regeneration using the heat of gas in the second regeneration unit 22b.

  The second absorbent A2 stored at the bottom of the regeneration tower 20 is heated to the vicinity of the boiling point by partial circulation heating. At this time, the boiling point of the absorbent depends on the composition (absorbent concentration) and the pressure in the regeneration tower 20. In heating, it is necessary to supply the latent heat of vaporization of water lost from the absorbing liquid and the sensible heat of the absorbing liquid. When the vaporization is suppressed by pressurization, the sensible heat increases due to the rise in boiling point. Therefore, considering these balances, it is preferable in terms of energy efficiency to apply a condition setting in which the inside of the regeneration tower 20 is pressurized to about 100 kPaG and the absorbent is heated to 120 to 130 ° C. The operation of the compressor 40 has the effect of lowering the internal pressure of the regeneration tower 20. Therefore, in order to pressurize the regeneration tower 20, the exhaust from the exhaust pipe 38 is controlled by an on-off valve (not shown) or the like. After increasing the pressure, the internal pressure of the regeneration tower 20 and the outlet pressure of the compressor 40 may be adjusted while controlling the operation of the compressor 40.

  In the regeneration tower 20, the recovered gas C containing carbon dioxide released from the absorbing liquid is immediately compressed by the compressor 40 (compression stroke), the gas temperature rises due to an increase in pressure, and it is easy to recover heat by heat exchange. Become. In the heat recovery process by the heat exchanger 41, the water vapor contained in the recovered gas C is condensed due to the temperature decrease, and the heat of condensation of the water is also released. In order to efficiently recover the heat, the compression rate by the compressor 40 may be adjusted so that the temperature after compression is about 120 to 500 ° C., preferably about 5 ° C. higher than the boiling point of the absorbing liquid. Although it depends on the amount of water vapor contained in the recovered gas C, it is generally preferable that the pressure of the recovered gas C is set to about 0.3 to 2.0 MPaG by the compression process. When performing a multi-stage compression process using a plurality of compressors, a higher pressure is required as the latter stage is reached. For example, when performing a three-stage compression, the pressure in the first stage compression process is 0. About 0.3 to 1.0 MPaG, about 0.5 to 1.5 MPaG in the second stage compression stroke, and about 1.0 to 2.0 MPaG in the third stage compression stroke may be set.

  The heat of compression and the heat of condensation of water generated by the compression are recovered through a part of the absorbing liquid A2 circulated from the regeneration tower 20 in the heat exchange process in the heat exchanger 41, and this is recovered in the first regeneration section of the regeneration tower 20. By recovering to 22a, the recovered heat is supplied to the absorption liquid of the regeneration tower 20. Thereby, the heat energy required for heating the absorption liquid A2 of the regeneration tower 20 by the steam heater 24 can be reduced. The condensed water condensed from the recovered gas C after the heat recovery step is subjected to the separation step by the gas-liquid separator 43, and then the pressure is released by the pressure reducing valve 44 and the second absorption liquid flowing in the second reflux path 29. It is added to A2 (water supply step) and refluxed to the second absorption part 12b of the absorption tower 10. The temperature of the condensed water in the gas-liquid separator 43 is about 40 to 50 ° C., and further decreases with vaporization due to the pressure reduction in the pressure reducing valve 44, which is convenient for introduction into the absorption tower 10 and in the cooler 36. It is also effective in reducing the amount of cooling heat. The addition of condensed water to the second reflux path 29 is also preferable in terms of adjusting the concentration to compensate for the concentration that is likely to occur in the second absorbent due to the transfer of water vapor from the first regeneration unit 22a to the second regeneration unit 22b. It is. If the water supply path 45 is branched and connected to the first reflux path 27, a part of the condensed water in the gas-liquid separator 43 is separated and the first absorption liquid in the first reflux path 27 is separated. This can be used for dilution of A1, and the degree of freedom in adjusting the concentration of the absorbing solution is increased.

  FIG. 2 shows a second embodiment of the carbon dioxide recovery method of the present invention and a recovery apparatus for carrying out the method. Unlike the first embodiment, the recovery device 2 is different from the first embodiment in the flow path of the absorbing liquid that exchanges heat with the recovered recovery gas C after compression, and the heat recovered in the heat recovery process is introduced from the absorption tower 10 into the regeneration tower 20. Is supplied to the second absorbing liquid A2 ′ immediately before being carried out.

  Specifically, a circulation path 51 that branches from the downstream side of the second heat exchanger 34 of the second supply path 17 and joins the second supply path 17 via the heat exchanger 41 a is provided, and the second absorption of the absorption tower 10. Part of the second absorbing liquid A2 ′ sent from the section 12b and passed through the second heat exchanger 34 is not directly supplied to the regeneration tower 20, but passes through the circulation path 51 to exchange heat in the heat exchanger 41a. After the processing, the refrigerant is refluxed to the second supply path 17 and supplied to the first regeneration unit 22a of the regeneration tower 20. The heat exchanger 41a is installed so as to exchange heat between the compressed recovered gas C in the exhaust pipe 38 and the second absorbent A2 'in the circulation path 51. Accordingly, the heat recovered from the recovered gas C discharged from the regeneration tower 20 is supplied to the first regeneration portion 22a of the regeneration tower 20 via the second absorption liquid A2 '.

  In the heat recovery process in the recovery device 2 of FIG. 2, a part of the second absorbent A2 ′ after the absorption process is heat-exchanged with the recovered gas C before being supplied to the regeneration process, and the second absorbent A2 ′. The introduction temperature T2 to the first regeneration unit 22a can be made higher than the temperature in FIG. 1, and can be, for example, about 95 to 130 ° C. Along with this, the temperature t1 of the gas released from the first regeneration unit 22a to the second regeneration unit 22b and the temperature T3 of the first absorbing liquid A1 heated by the second regeneration unit 22b can also be increased. . This embodiment is useful when it is necessary to supplement heat exchange in the second heat exchanger 34, and conversely, the second heat exchanger 34 can be downsized. In order to further strengthen this, the second supply path 17 is changed so as to be connected to the regeneration tower 20 via the circulation path 51, and all the second absorbing liquid A2 'in the second supply path 17 is subjected to heat exchange. It can comprise so that it may pass through the container 41a.

  In the embodiment of FIG. 2, the configuration other than the above is the same as that of the embodiment of FIG.

  FIG. 3 shows a third embodiment of the carbon dioxide recovery method of the present invention and a recovery apparatus for carrying it out. Unlike the first embodiment, the recovery device 3 is different from the first embodiment in the flow path of the absorbing liquid that exchanges heat with the recovered recovery gas C after compression, and the heat recovered in the heat recovery process is from the absorption tower 10 to the regeneration tower 20. 2 is supplied to the first absorbent A1 ′ just before being introduced into the regenerator 22b.

  Specifically, a circulation path 52 that branches from the first heat exchanger downstream of the first supply path 15 and joins the first supply path 15 via the heat exchanger 41b is provided, and the first absorption section of the absorption tower 10 is provided. Part of the first absorbing liquid A1 ′ sent from 12a and passed through the first heat exchanger 33 is not directly supplied to the regeneration tower 20, but passes through the circulation path 52 and is subjected to heat exchange processing in the heat exchanger 41b. Then, the refrigerant is refluxed to the first supply path 15 and supplied to the second regeneration unit 22b of the regeneration tower 20. The heat exchanger 41b is installed so as to exchange heat between the compressed recovered gas C in the exhaust pipe 38 and the first absorbent A1 'in the circulation path 52. Accordingly, the heat recovered from the recovered gas C discharged from the regeneration tower 20 is supplied to the second regeneration portion 22b of the regeneration tower 20 via the first absorption liquid A1 '.

  In the heat recovery step in the recovery device 3 of FIG. 3, a part of the first absorbent A1 ′ after the absorption step is heat-exchanged with the recovery gas C before being supplied to the regeneration step, and the second regeneration unit 22b The temperature T4 of the first absorbing liquid A1 ′ to be introduced can be made higher than the temperature in FIG. 1, and can be, for example, about 85 to 115 ° C. Accordingly, the temperature T3 of the absorbing liquid A1 at the bottom of the second regeneration unit 22b and the temperature t2 of the gas released from the second regeneration unit 22b can also be increased. This embodiment is useful when it is necessary to supplement heat exchange in the first heat exchanger 33, and conversely, the first heat exchanger 33 can be downsized. In order to further strengthen this, the first supply path 15 is changed so as to be connected to the regeneration tower 20 through the circulation path 52, and all of the first absorbent A1 ′ in the first supply path 15 is heat exchanger 41b. It can be configured to pass through.

  In the embodiment of FIG. 3, the configuration other than the above is the same as that of the embodiment of FIG.

  FIG. 4 shows a fourth embodiment of the carbon dioxide recovery method of the present invention and a recovery apparatus for implementing the method. The recovery device 4 is a combination of the configurations shown in FIGS. 1 to 3, and the heat recovery system is configured such that the recovered gas C after compression is converted into the second absorbent A2 at the bottom of the regeneration tower 20 and the first regeneration unit 22a. The second absorption liquid A2 ′ immediately before being introduced into the first absorption liquid and the first absorption liquid A1 ′ immediately before being introduced into the second regeneration unit 22b are sequentially heat-exchanged.

  Specifically, on the exhaust pipe 38a for discharging the recovered gas C from the regeneration tower 20, a compressor 40 provided so as to be in direct communication with the regeneration tower 20 and the bottom of the regeneration tower 20 as in the recovery devices 1 to 3. A part of the second absorption liquid A2 is circulated and circulated between the outside of the regeneration tower, the recovered gas C compressed by the compressor 40, and the second absorption liquid A2 of the circulation path 50. A heat exchanger 41 installed so as to exchange heat between them, and a gas-liquid separator 43 for separating condensed water condensed from the recovered gas C. Further, in this embodiment, the exhaust pipe 38a is provided with a heat exchanger 41c and a heat exchanger 41d between the heat exchanger 41 and the gas-liquid separator 43, and the heat exchanger 41c is connected to the exhaust pipe 38a. Heat exchange is performed between the recovered gas C and the second absorbent A2 ′ in the second supply path 17, and the heat exchanger 41c is connected to the recovered gas C in the exhaust pipe 38a and the first absorbent A1 ′ in the first supply path 15. Heat exchange. The second absorption liquid A2 in the regeneration tower 20 is refluxed to the bottom of the regeneration tower 20 after heat exchange by the heat exchanger 41, and the second absorption liquid A2 ′ in the second supply path 17 is subjected to heat exchange by the heat exchanger 41c. The first absorption liquid A1 ′ in the first supply path 15 is charged into the upper part of the first regeneration unit 22a, and is then introduced into the upper part of the second regeneration unit 22b after heat exchange by the heat exchanger 41d. The heat recovered from the compressed recovery gas C is the second absorption liquid A2 in the circulation path 50, the second absorption liquid A2 ′ in the second supply path 17, and the first absorption liquid A1 ′ in the first supply path 15. Are sequentially transmitted to the regeneration tower 20 via these. In the heat exchange in the heat exchangers 41, 41c, 41d, the temperature of the recovered gas C decreases stepwise, and the water vapor contained in the recovered gas C cools and condenses to release condensation heat, so these heat exchangers In addition to the heat of compression, the heat of condensation of water is also recovered.

  In this configuration, the outlet temperature of the second heat exchanger 34 of the second absorbing liquid A2 ′ is about 90 to 125 ° C., and the introduction temperature T2 to the first regeneration unit 22a is 95 to 130 by the heat exchanger 41c. It can be set to about ° C. The temperature t1 of the gas released from the first regeneration unit 22a to the second regeneration unit 22b is about 90 to 120 ° C., and is heated by the second regeneration unit 22b by the gas released from the first regeneration unit 22a. The temperature T3 of the first absorbent A1 is about 85 to 120 ° C. Due to heat exchange in the first heat exchanger 33, the temperature of the first absorption liquid A1 ′ becomes 80 to 110 ° C., and the temperature T4 of the first absorption liquid A1 ′ introduced into the second regeneration unit 22b is changed by the heat exchanger 41d. It can be about 85-115 degreeC.

  In FIG. 4, the recovered gas C in the exhaust pipe 38a that has undergone heat recovery by the heat recovery system is sufficiently cooled by the cooler 42 using cooling water to condense water vapor as much as possible, and then the gas-liquid separator 43. The water is recovered after removing the condensed water. The gas-liquid separator 43 is connected to the downstream side of the cooler 36 of the second reflux path 29 by a water supply path 45, and the condensed water separated by the gas-liquid separator 43 is appropriately controlled by a pressure reducing valve 44 that releases the pressure. The pressure is adjusted to a reduced pressure, added from the water supply path 45 to the second absorbent A2 on the downstream side of the cooler 36 of the second reflux path 29, and refluxed to the upper part of the second absorption section 12b of the absorption tower 10.

  Also in the embodiment of FIG. 4, it is possible to similarly apply and change possible in the embodiment of FIGS. 1 to 3. Further, any one of the heat exchangers 41, 41c, and 41d may be omitted, and the heat recovery may be performed using only two heat exchangers. If the two heat exchangers are omitted from the embodiment of FIG. 4, the embodiment is the same as the embodiment of FIGS. 1 to 3.

  As described above, in the first to fourth embodiments, the first and second absorption liquids A1 and A2 circulate between the absorption tower 10 and the regeneration tower 20 independently of each other, and the first regeneration section 22a. By performing the two-stage regeneration process using the second regeneration unit 22b that performs regeneration at a lower temperature, the utilization efficiency of heat energy in the regeneration tower is improved. Of the first and second absorption liquids A1 and A2, the first absorption liquid A1 can be regarded as an auxiliary absorption liquid, and the second absorption liquid A2 can be regarded as a main absorption liquid. That is, the role of the first absorption liquid A1 includes the reduction of the absorption load given to the second absorption liquid A2 by the gas having a high carbon dioxide concentration, as well as the recovery and reuse of thermal energy in the regeneration tower. In other words, the apparatus configuration shown in FIGS. 1 to 4 is also effective in improving the process adaptability of the recovery apparatus.

  In the first to fourth embodiments, the ratio α1 / α2 between the filling volume α1 of the filler 11a of the first absorber 12a and the filler volume α2 of the filler 11b of the second absorber 12b in the absorption tower 10 is regenerated. The tower 20 is designed to be substantially equal to the ratio β2 / β1 of the filling volume β2 of the packing material 21b of the second regeneration unit 22b and the packing volume β1 of the packing material 21a of the first regeneration unit 22a. The ratio γ1 / γ2 between the circulating amount γ1 of the absorbing liquid and the circulating amount γ2 of the second absorbing liquid may be substantially equal to the above-described ratios α1 / α2 and β2 / β1. As described above, the first absorption liquid A1 can be regarded as an auxiliary absorption liquid, and the ratios α1 / α2 and γ1 / γ2 are about 1/10 to 9/10, preferably 4/10 to 8/10. Setting it to a degree is convenient for efficiently using heat energy.

In order to investigate the effect of heat recovery of the three heat exchangers 41, 41c, 41d in the embodiment of FIG. 4, 0 to 3 of the three heat exchangers 41, 41c, 41d are used to collect the recovered gas C. Regeneration energy (energy required for carbon dioxide recovery) when recovering heat from wastewater is examined by calculation using a process simulator, and the regenerative energy in the basic structure (processing by a single absorption tower and regeneration tower) (about The ratio to 2.8 GJ / t-CO ₂ ) was determined. This is expressed as a percentage as shown in Table 1 below. In this calculation, the heat exchange performance of the first and second heat exchangers 33, 34 and the heat exchangers 41, 41c, 41d (the temperature between the inlet temperature of the heat supply fluid and the outlet temperature of the heat receiving fluid) Difference) It is assumed that ΔT is set to 10 ° [K], the above-mentioned ratio α1 / α2 is set to 5/10, and processing is performed so as to recover carbon dioxide from the carbon dioxide-containing gas at a recovery rate of 90%.

(Table 1)
Sign of heat exchanger used Percentage of regenerative energy- 84.6%
41 72.0%
41c 76.8%
41d 80.4%
41 + 41c 70.5%
41 + 41d 64.1%
41c + 41d 72.1%
41 + 41c + 41d 63.2%
Basic structure 100%

  As can be seen from Table 1, the effect of reducing the regenerative energy is increased by increasing the number of heat exchangers used for heat recovery and repeating heat recovery and supply. In the comparison of the three heat exchangers 41, 41c, 41d, it is most effective to reduce the regeneration energy by supplying the recovered heat to the second absorbent A2 at the bottom of the regeneration tower 20 using the heat exchanger 41. is there. In other words, it is more advantageous to supply the recovered heat to the part where the temperature is high.

  However, when two heat exchangers are used, the form using the heat exchangers 41 and 41d has less regeneration energy than the form using the heat exchangers 41 and 41c. One reason for this is that the heat exchange performance cannot be satisfactorily exhibited because the difference between the inlet temperature of the recovered gas C and the inlet temperature of the second absorbent A2 'in the heat exchanger 41c is small. When the heat exchanger 41d is used, the heat exchange performance is suitably exhibited in the difference in inlet temperature between the recovered gas C and the first absorption liquid A1 ′, so that the amount of water vapor released to the exhaust pipe 38a and Even if the latent heat increases, the heat is recovered again, and as a result, the efficiency becomes better than when the heat exchanger 41c is used. This superiority or inferiority relationship changes depending on the use of a heat exchanger with higher heat exchange performance. Alternatively, even if an additional compressor is provided on the exhaust pipe 38a on the downstream side of the heat exchanger 41, the heat regeneration performance is sufficiently exhibited in the heat exchanger 41c by the compression heat of the additional compressor, and the first regeneration is performed. The recovered heat supplied to the section 22a increases and the regeneration energy decreases. From the above, in the configuration of FIG. 4, additional compressors are provided between the heat exchanger 41 and the heat exchanger 41c, and between the heat exchanger 41c and the heat exchanger 41d, respectively, and the temperature of the recovered gas C. By changing so as to increase the heat recovery efficiency of the heat exchanger 41c and the heat exchanger 41d, the regeneration energy can be reduced most.

  The condensed water separated and recovered from the recovered gas C can be used to correct the composition of the fluctuating absorption liquid. If necessary, a part of the condensed water in the gas-liquid separator 43 may be branched to change the condensed water. You may change so that it may add to 2 absorption liquid. Such a change may be appropriately selected in consideration of the degree of composition variation of the absorbing liquid in the regeneration tower 20, the amount of recovered condensed water, and the liquid temperature. When addition of an absorbent is necessary due to consumption or leakage of the absorbent, the composition can be adjusted by adding it to the absorbent before introduction into the absorption tower together with condensed water.

  INDUSTRIAL APPLICABILITY The present invention is useful for reducing the amount of carbon dioxide released and its influence on the environment by using it for the treatment of carbon dioxide-containing gas discharged from facilities such as thermal power plants, ironworks, and boilers. It is possible to reduce the thermal energy required for the carbon dioxide recovery process, and to provide a carbon dioxide recovery device that can contribute to a reduction in operating costs, energy saving, and environmental protection.

1, 2, 3, 4 recovery device, 10 absorption tower, 20 regeneration tower,
11, 11a, 11b, 21, 21a, 21b, 21c filler,
12a 1st absorption part, 12b 2nd absorption part, 13, 23 Partition member,
14, 16, 26, 28, 32 pumps,
15 1st supply path, 17 2nd supply path, 18 cooling condensation part,
22a first reproduction unit, 22b second reproduction unit,
24 steam heater, 25, 50, 51, 52 circuit,
27 1st reflux path, 29 2nd reflux path,
31, 35, 36, 42 cooler,
33 1st heat exchanger, 34 2nd heat exchanger,
37 Condensing section, 38, 38a Exhaust pipe,
40 compressor, 40M motor,
41, 41a, 41b, 41c, 41d heat exchangers,
43 gas-liquid separator, 44 pressure reducing valve,
45 water supply path, 46 pressure gauge,
G, G 'gas, C recovered gas,
A1, A1 ′ first absorbing solution, A2, A2 ′ second absorbing solution.

Claims (20)

An absorption tower in which a gas is brought into contact with an absorption liquid and carbon dioxide contained in the gas is absorbed by the absorption liquid, the absorption tower having a first absorption section and a second absorption section, and the gas includes the first absorption section. The absorption tower disposed so as to be supplied to the second absorption part via,
A regeneration tower that regenerates the absorption liquid by heating the absorption liquid that has absorbed carbon dioxide in the absorption tower to release carbon dioxide, the first regeneration section having a first regeneration section and a second regeneration section. Part has an external heating means, and the second regeneration unit is arranged to be heated by the heat of the gas released from the first regeneration unit, and
A first circulation system for circulating the absorption liquid between the first absorption section and the second regeneration section; and a second circulation system for circulating the absorption liquid between the second absorption section and the first regeneration section. A circulation system having a circulation system;
A compressor that directly compresses the recovered gas containing water vapor and carbon dioxide discharged from the regeneration tower;
And a heat recovery system that recovers heat of the recovered gas compressed by the compressor and supplies the recovered gas to the regeneration tower. Furthermore, a gas-liquid separator that separates water condensed from the recovered gas from which heat has been recovered by the heat recovery system;
A water supply path for supplying water separated in the gas-liquid separator to an absorption liquid that is refluxed from the first regeneration section to the second absorption section in the second circulation system;
2. The carbon dioxide recovery apparatus according to claim 1, wherein the first circulation system and the second circulation system circulate the absorption liquid independently of each other, and the second regeneration unit does not have an external heating unit.   The circulation system includes a first heat exchanger and a second heat exchanger, and the first heat exchanger is supplied from the first absorption unit to the second regeneration unit in the first circulation system. Heat exchange is performed between the absorption liquid and the absorption liquid recirculated from the second regeneration section to the first absorption section, and the second heat exchanger is configured such that in the second circulation system, the second absorption section A heat exchanger exchanges the absorption liquid supplied to the first regeneration section with the absorption liquid refluxed from the first regeneration section to the second absorption section, respectively. The carbon dioxide recovery device described in 1. The heat recovery system includes:
A heat exchanger that performs heat exchange between the absorption liquid between the second heat exchanger and the first regeneration unit in the second circulation system and the recovered gas compressed by the compressor, The carbon dioxide recovery apparatus according to claim 3, wherein heat of the recovery gas is supplied to the first regeneration unit via the absorption liquid of the second circulation system. The heat recovery system includes:
A heat exchanger that performs heat exchange between the absorption liquid between the first heat exchanger and the second regeneration unit in the first circulation system and the recovered gas compressed by the compressor, The carbon dioxide recovery apparatus according to claim 3 or 4, wherein heat of the recovery gas is supplied to the second regeneration unit via the absorption liquid of the first circulation system. The heat recovery system includes:
A circulation path for circulating the absorption liquid of the first regeneration section between the outside of the regeneration tower;
A heat exchanger for exchanging heat between the absorption liquid in the circulation path and the recovered gas compressed by the compressor, whereby heat of the recovery gas flows through the absorption liquid in the circulation path to the first The carbon dioxide recovery apparatus according to any one of claims 1 to 5, which is supplied to the regeneration unit.   The temperature of the absorption liquid supplied to the second regeneration unit in the circulation of the first circulation system is configured to be lower than the temperature of the absorption liquid supplied to the first regeneration unit in the circulation of the second circulation system. Item 7. The carbon dioxide recovery device according to any one of Items 1 to 6.   The carbon dioxide recovery apparatus according to any one of claims 1 to 7, wherein the first circulation system and the second circulation system circulate a first absorbent and a second absorbent having different compositions from each other.   The carbon dioxide recovery apparatus according to claim 8, wherein the first absorbent that circulates in the first circulation system has a higher absorbent concentration than the second absorbent that circulates in the second circulation system.   The first absorbent that circulates in the first circulation system contains an absorbent that is more regenerative than the absorbent that the second absorbent that circulates in the second circulation system, and the second absorbent is The carbon dioxide recovery device according to claim 8 or 9, further comprising an absorbent having higher carbon dioxide absorption capacity than the absorbent contained in the first absorbent. An absorption process in which a gas is brought into contact with an absorption liquid and carbon dioxide contained in the gas is absorbed by the absorption liquid, the first absorption process and the second absorption process, and the gas passes through the first absorption process. The absorption treatment supplied to the second absorption step;
A regeneration process for heating the absorption liquid that has absorbed carbon dioxide in the absorption process to release carbon dioxide to regenerate the absorption liquid, and includes a first regeneration process and a second regeneration process, and the first regeneration process. In the process, heating is performed using an external heating means, and in the second regeneration process, the regeneration process is performed by heat of the gas released in the first regeneration process;
A first circulation step for circulating the absorbent between the first absorption step and the second regeneration step;
A second circulation step for circulating the absorbent between the second absorption step and the first regeneration step;
A compression step of directly compressing the recovered gas containing water vapor and carbon dioxide discharged from the regeneration process;
And a heat recovery step of recovering heat of the recovered gas compressed in the compression step and supplying the recovered gas to the regeneration process. A separation step of separating water condensed from the recovered gas after the heat recovery step;
A water supply step of supplying water separated in the separation step to an absorption liquid circulated from the first regeneration step to the second absorption step in the second circulation step;
The carbon dioxide recovery method according to claim 11, wherein the first circulation step and the second circulation step circulate the absorbing solution independently of each other.   In the first circulation step, heat exchange is performed between the absorption liquid supplied from the first absorption process to the second regeneration process and the absorption liquid refluxed from the second regeneration process to the first absorption process. An absorption liquid supplied from the second absorption process to the first regeneration process and an absorption refluxed from the first regeneration process to the second absorption process; The method for recovering carbon dioxide according to claim 11 or 12, further comprising a second heat exchange step for exchanging heat with the liquid. The heat recovery step includes
In the second circulation step, there is a heat exchange process for performing heat exchange between the absorption liquid before being supplied to the first regeneration step through the second heat exchange step and the recovered gas compressed in the compression step, Accordingly, the carbon dioxide recovery method according to claim 13, wherein the heat of the recovered gas is supplied to the first regeneration step via the absorption liquid of the second circulation step. The heat recovery step includes
A heat exchange process for performing heat exchange between the absorption liquid before being supplied to the second regeneration step through the first heat exchange step in the first circulation step and the recovered gas compressed by the compression step; Accordingly, the method for recovering carbon dioxide according to claim 13 or 14, wherein the heat of the recovered gas is supplied to the second regeneration step via the absorbing liquid in the first circulation step. The heat recovery step includes
A heat exchange process for performing heat exchange between the absorbing liquid in the first regeneration step and the recovered gas compressed in the compression step, whereby heat of the recovered gas is supplied to the first regeneration step. The method for recovering carbon dioxide according to any one of 11 to 15.   The temperature of the absorption liquid supplied to the second regeneration process in the circulation of the first circulation process is lower than the temperature of the absorption liquid supplied to the first regeneration process in the circulation of the second circulation process. The carbon dioxide recovery method according to any one of 16.   The method for recovering carbon dioxide according to any one of claims 11 to 17, wherein in the first circulation step and the second circulation step, a first absorbent and a second absorbent having different compositions are circulated.   The method for recovering carbon dioxide according to claim 18, wherein the first absorbent that circulates in the first circulation step has a higher absorbent concentration than the second absorbent that circulates in the second circulation step.   The first absorbent that circulates in the first circulation step contains an absorbent that is more regenerative than the absorbent contained in the second absorbent that circulates in the second circulation step, and the second absorbent is The method for recovering carbon dioxide according to claim 18 or 19, comprising an absorbent having higher carbon dioxide absorption capacity than the absorbent contained in the first absorbent.

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