JP5720463B2 - Carbon dioxide recovery method and recovery apparatus - Google Patents

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.

  As shown in Patent Document 1, heat energy is exchanged between a high-temperature absorption liquid (lean liquid) that has released carbon dioxide in the regeneration process and an absorption liquid (rich liquid) that has absorbed carbon dioxide in the absorption process. Can be recovered and reused in the regeneration process.

JP 2009-214089 A

  In heat exchange between absorbing liquids, the smaller the temperature difference between the rich liquid after heat exchange and the lean liquid before heat exchange, the better the heat recovery efficiency and the lower the energy required for regeneration. However, if a rich liquid is supplied to the regeneration process at the highest possible temperature using a heat exchanger with a high heat exchange rate, the gas pressure of carbon dioxide in the absorbent rises and the heat In this case, carbon dioxide foaming occurs, and heat transfer efficiency due to gas generation is likely to be reduced, or temperature reduction due to vaporization is likely to occur.

  The problem of the present invention is to solve the above-mentioned problems, suppress gas generation in heat exchange of the absorption liquid used for carbon dioxide recovery, and stably supply the absorption liquid to be supplied to the regeneration process at a higher temperature. It is to provide a carbon dioxide recovery method and a recovery device that improve energy efficiency.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research and found that the pressure in the regeneration process is effectively adjusted from the heat exchange process of the absorbing liquid, and the present invention has been completed. .

According to one aspect of the present invention, a carbon dioxide recovery device includes an absorption tower in which a gas containing carbon dioxide is brought into contact with an absorption liquid so that the absorption liquid absorbs carbon dioxide, and the absorption tower absorbs carbon dioxide. A regeneration tower that regenerates the absorption liquid by heating the absorption liquid to release carbon dioxide from the absorption liquid, a supply path that supplies the absorption liquid from the absorption tower to the regeneration tower, and the absorption from the regeneration tower. A reflux path for refluxing the absorption liquid to the tower, an absorption liquid in the supply path supplied from the absorption tower to the regeneration tower, and an absorption liquid in the reflux path refluxed from the regeneration tower to the absorption tower. A heat exchanger for exchanging heat, and a back pressure valve provided between the heat exchanger and the regeneration tower in the supply path, wherein the absorption liquid supplied from the absorption tower to the regeneration tower is in a pressurized state. The absorbent to be supplied to the heat exchanger. And pressurizing means for pressurizing said to miss the pressure excess in the pressurization by the pressurizing means, possess the evacuation path branched from the supply passage, and a flow control valve provided in the evacuation passage, the flow regulating valve Is summarized in that the opening degree is adjusted according to the pressure of the absorbing liquid in the supply path .
According to another aspect of the present invention, a carbon dioxide recovery apparatus includes an absorption tower for bringing a gas containing carbon dioxide into contact with an absorption liquid to cause the absorption liquid to absorb carbon dioxide, and a carbon dioxide in the absorption tower. A regeneration tower for regenerating the absorbing liquid by heating the absorbing liquid that has absorbed carbon to release carbon dioxide from the absorbing liquid; a supply path for supplying the absorbing liquid from the absorbing tower to the regenerating tower; and the regenerating tower A reflux path for refluxing the absorption liquid from the absorption tower to the absorption tower, an absorption liquid in the supply path supplied from the absorption tower to the regeneration tower, and an absorption liquid in the reflux path refluxed from the regeneration tower to the absorption tower; And a back pressure valve provided between the heat exchanger and the regeneration tower in the supply path, and an absorption liquid supplied from the absorption tower to the regeneration tower is added to the heat exchanger. The suction so as to be supplied to the heat exchanger under pressure. A pressurizing means for pressurizing the liquid, a retreat path branched from the supply path for releasing excess pressure in pressurization by the pressurizing means, and a back pressure valve provided in the retreat path, and the heat The gist is that the pressurized state of the absorbent supplied to the exchanger is adjusted by a back pressure valve in the supply path and a back pressure valve in the retreat path.

According to another aspect of the present invention, a method for recovering carbon dioxide includes an absorption step in which a gas containing carbon dioxide is brought into contact with an absorption liquid to cause the absorption liquid to absorb carbon dioxide, and carbon dioxide is absorbed in the absorption step. Heating the absorption liquid that has absorbed the carbon dioxide to release carbon dioxide from the absorption liquid to regenerate the absorption liquid; the absorption liquid supplied from the absorption process to the regeneration process; and the absorption from the regeneration process A heat exchanging process for exchanging heat with the absorbing liquid refluxed to the process. In the heat exchanging process, the absorbing liquid supplied from the absorbing process to the regeneration process is heat-exchanged in a pressurized state. In order to release the excess pressure in the pressurized state, the retraction is performed according to the pressure of the absorbent in the pressurized state using a retreat path that branches the absorbing liquid supplied from the absorption step to the regeneration step. Absorbing liquid evacuated to the road And gist Rukoto varying the flow rate.
According to another aspect of the present invention, a method for recovering carbon dioxide includes: an absorption step in which a gas containing carbon dioxide is brought into contact with an absorption liquid to absorb the carbon dioxide in the absorption liquid; A regeneration step of heating the absorption liquid that has absorbed carbon to release carbon dioxide from the absorption liquid to regenerate the absorption liquid; an absorption liquid supplied from the absorption process to the regeneration process; and A heat exchange step for exchanging heat with the absorption liquid refluxed to the absorption step, and in the heat exchange step, the absorption liquid supplied from the absorption step to the regeneration step is heat exchanged in a pressurized state. The back pressure of the absorption liquid that retreats to the retraction path using the retraction path that branches the absorption liquid that is supplied from the absorption process to the regeneration process, and the absorption liquid that is supplied from the absorption process to the regeneration process Of back pressure and by And summarized in that miss the pressure of surplus by adjusting the pressure.

  According to the present invention, in the process of recovering carbon dioxide contained in the gas, the absorption liquid is transferred to the regeneration process at a higher temperature by suppressing the foaming and gas generation in the heat exchange of the absorption liquid and efficiently exchanging heat. Therefore, it is possible to reduce the energy required to regenerate the absorbing solution, and to provide a carbon dioxide recovery method and recovery device that are effective in reducing operation costs. It is economically advantageous because it can be carried out easily using general equipment without requiring special equipment or expensive equipment.

The graph which shows the relationship between the pressure added to an absorption liquid, and the generation rate of gas. 1 is a schematic configuration diagram showing a carbon dioxide recovery apparatus according to a first embodiment of the present invention. The schematic block diagram which shows the collection | recovery apparatus of the carbon dioxide which concerns on the 2nd Embodiment of this invention.

  In the absorption process of carbon dioxide by the chemical absorption method, an absorption process in which carbon dioxide contained in the gas is absorbed by a low-temperature absorption liquid, and a high-temperature regeneration in which the absorbed carbon dioxide is released from the absorption liquid and the absorption liquid is regenerated. The absorption liquid is circulated between the processes, and the absorption process and the regeneration process are alternately repeated. Heat energy is recovered and heated by exchanging heat from the high-temperature absorption liquid (lean liquid) regenerated by releasing carbon dioxide in the regeneration process with the absorption liquid (rich liquid) that has absorbed carbon dioxide in the absorption process. The lean liquid is supplied to the regeneration process. From the viewpoint of energy efficiency, it is desirable that the temperature difference between the inlet temperature of the lean liquid and the outlet temperature of the rich liquid in the heat exchanger is small, and this difference is conventionally said to be around 10 ° C. This temperature difference can be reduced by increasing the efficiency in the heat exchanger, but carbon dioxide bubbles as the temperature of the rich liquid rises, hindering heat transfer and hindering the reduction of the temperature difference.

  In the present invention, in consideration of the above points, the rich liquid is introduced into the heat exchanger in a pressurized state to suppress foaming when the temperature of the rich liquid rises. Thereby, the temperature rise of the lean liquid in the heat exchanger is facilitated, and the temperature difference between the inlet temperature of the lean liquid and the outlet temperature of the rich liquid can be reduced to less than 10 ° C. by improving the efficiency of the heat exchanger. The pressure applied to the rich liquid is released when it is put into the regeneration process, so that carbon dioxide is efficiently released, and the heat energy given to the rich liquid by the heat exchanger is efficiently supplied to the regeneration process. The

  Absorbing liquid that has absorbed carbon dioxide begins to release carbon dioxide as the temperature rises, but the absorption performance and release performance of carbon dioxide in the absorbing liquid vary depending on the type and composition ratio of the absorbent contained in the absorbing liquid. In order to investigate the generation of gas at the heat exchanger outlet temperature of the rich liquid, when the carbon dioxide gas generated from the absorbing liquid during heating is measured using two kinds of absorbing liquid, a graph as shown in FIG. 1 is obtained. It is done. In this measurement, 30 wt% MEA (monoethanolamine) aqueous solution or PZ / MDEA aqueous solution (piperazine / N-methyldiethanolamine) was used as an absorbing solution, and carbon dioxide was absorbed at a rate of 50 to 100 [g / L]. The ratio [mol%] of carbon dioxide gas generated when the absorbing solution is heated to 100 to 115 ° C. was examined by changing the pressure applied to the absorbing solution. The PZ / MDEA aqueous solution is one of the absorbing liquids having good diffusibility. In any absorption liquid, gas is generated at normal pressure, but generation of gas can be suppressed by pressurization. The absorption liquid in the regeneration step is generally heated near the boiling point, and the boiling points of the two types of absorption liquid are about 100 ° C. (normal pressure) to about 130 ° C. (100 kPaG), so the pressure applied to the absorption liquid is 150 kPaG or more, When it is preferably set to 200 kPaG or higher, more preferably 250 kPaG or higher, gas generation in the heat exchanger can be suppressed, and the outlet temperature of the rich liquid in the heat exchanger is brought close to the inlet temperature (regeneration temperature) of the lean liquid. It is effective in.

  In addition, when the rich liquid that had been subjected to heat exchange in a pressurized state was introduced into the regeneration tower, the temperature of the gas containing water vapor and carbon dioxide discharged from the regeneration tower was examined, compared with the case of heat exchange at normal pressure. Turned out to be low. Specifically, when the PZ / MDEA aqueous solution is used as an absorption liquid and the absorption liquid in which carbon dioxide has been absorbed is heated to 50 ° C. and charged into the regeneration tower, the temperature of the exhaust gas from the regeneration tower is When it is normal pressure, it is 91.3 ° C., but when heated under a pressure of 200 kPaG or more, it drops to 88.1 ° C. Such a temperature decrease is thought to be due to the fact that the regeneration reaction proceeds in the heating state in the heat exchanger, and the proportion of energy that can be consumed as latent heat of vaporization when it is introduced into the regeneration tower increases. This is advantageous in that it is easy to condense.

  The carbon dioxide recovery method and recovery apparatus of the present invention using the above-described configuration will be described in detail below with reference to the drawings. In addition, the connection described with a broken line in a figure shows an electrical connection.

  FIG. 2 shows an embodiment of the carbon dioxide recovery method of the present invention and a recovery apparatus for implementing the method. 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. Furthermore, since the cooling tower 30 is provided so that the gas G supplied to the absorption tower 10 can be easily maintained at a low temperature suitable for absorption of carbon dioxide, various gases such as combustion exhaust gas and process exhaust gas can be handled. The gas G supplied to the recovery device 1 is not particularly limited. The absorption tower 10, the regeneration tower 20, and the cooling tower 30 are each configured as a countercurrent gas-liquid contact device, and hold fillers 11, 21, 31 for increasing the contact area. The fillers 11, 21, 31 are generally made of ferrous metal materials such as stainless steel and carbon steel, but are not particularly limited, and are materials having durability and corrosion resistance at the processing temperature. It is preferable to select a shape that can provide 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 gas G supplied from the bottom of the cooling tower 30 passes through the filler 31 held in the tower, is cooled by the cooling water supplied from the upper part of the cooling tower 30, and is then supplied to the absorption tower 10. Thereby, the gas G below the saturation humidity at the cooling temperature is supplied to the absorption tower 10, and the temperature rise of the absorption tower 10 due to the gas G is prevented. The cooling water whose temperature has risen by cooling the gas G is sent to the water-cooled cooler 33 by the pump 32, cooled, and then returned to the cooling tower 30. If a temperature sensor is provided in the air pipe 18 connected to the bottom of the absorption tower 10 and the drive of the pump 32 is controlled according to the detected temperature, the heat is increased by increasing the flow rate of the cooling water when the temperature of the gas G is high. The temperature of the gas G can be lowered by increasing the exchange rate.

  The gas G containing carbon dioxide that has passed through the cooling tower 30 is supplied from the lower part of the absorption tower 10. On the other hand, the absorption liquid is supplied from the upper part of the absorption tower 10, and gas-liquid contact is made while the gas G and the absorption liquid pass through the filler 11, so that carbon dioxide in the gas G is absorbed by the absorption liquid. The absorption liquid (rich liquid) A1 that has absorbed carbon dioxide is stored at the bottom of the absorption tower 10 and is supplied to the regeneration tower 20 by a pump 12 through a supply path 16 that connects the bottom of the absorption tower 10 and the top of the regeneration tower 20. . The gas G ′ from which carbon dioxide has been removed is discharged from the top of the absorption tower 10.

  Since the absorption liquid absorbs carbon dioxide and generates heat, and the liquid temperature rises, a cooling condensing unit 13 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 as necessary. 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 14 and a pump 15 attached outside the absorption tower, and a part of the condensed water stored under the cooling condenser 13 (including the gas G ′ in the tower). Is good) is circulated between the cooler 14 by the pump 15. Condensed water or the like cooled by the cooler 14 and supplied to the top of the tower maintains the cooling condensing unit 13 at a low temperature and reliably cools the gas G ′ passing through the cooling condensing unit 13. The water condensed in the cooling and condensing unit 13 flows down to the packing material 11, and the composition fluctuation of the absorbing liquid in the tower is compensated. The driving of the pump 15 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.

  The absorption liquid A1 of the absorption tower 10 is supplied from the supply path 16 to the upper part of the regeneration tower 20, flows down on the filler 21, and is stored at the bottom. A reboiler is attached to the bottom of the regeneration tower 20. That is, a steam heater 22 provided outside the regeneration tower 20 for heating the absorption liquid and a circulation path 22 ′ for circulating the absorption liquid through the steam heater 22 are provided, and one of the absorption liquid A 2 at the bottom of the tower is provided. The part is branched to a steam heater 22 through a circulation path 22 ', heated by heat exchange with high-temperature steam, and then refluxed into the tower. By this heating, carbon dioxide is released from the absorption liquid at the bottom, and the filler 21 is also indirectly heated to promote the release of carbon dioxide by gas-liquid contact on the filler 21.

  The absorption liquid (lean liquid) A2 regenerated by releasing carbon dioxide in the regeneration tower 20 is refluxed to the absorption tower 10 by the pump 23 through the reflux path 17. Heat transfer occurs between the supply path 16 and the reflux path 17 due to contact in the heat exchanger 24, and the absorption liquid A1 in the supply path 16 supplied from the absorption tower 10 to the regeneration tower 20 is heated. The absorbing liquid A2 is cooled. Further, the absorption liquid A2 in the reflux path 17 is sufficiently cooled to a temperature suitable for absorption of carbon dioxide by the cooler 25 using cooling water. There are various 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-liquid type, etc. There are various types, and any type may be used as the heat exchanger 24 in the present invention, but the plate type is superior in terms of simplification of the apparatus and ease of cleaning and disassembly.

  The gas containing carbon dioxide released by heating in the regeneration tower 20 is discharged as a recovered gas C from the top through the condensing part 26 at the top of the regeneration tower 20. The condensing part 26 condenses the water vapor | steam contained in gas, suppresses excessive discharge | release, and also suppresses discharge | release of an absorber. The recovered gas C is sufficiently cooled by the cooler 27 using cooling water from the top of the regeneration tower 20 through the exhaust pipe 34, condensed as much as possible water vapor and the like, and condensed by the gas-liquid separator 28. It is recovered after removing the water. Carbon dioxide contained in the recovered gas C can be fixed and reorganized in the ground by, for example, injecting it into the ground or oil fields. The condensed water separated in the gas-liquid separator 28 is supplied at a predetermined flow rate from the flow path 35 onto the condensing unit 26 of the regeneration tower 20 by the pump 36, and functions as cooling water.

  In the supply path 16, a back pressure valve 41 is provided between the heat exchanger 24 and the regeneration tower 20 in the supply path 16 in order to pressurize the absorbing liquid A1 flowing through the heat exchanger 24 using the driving force of the pump 12. It is done. In this embodiment, the back pressure valve 41 is disposed in the vicinity of the regeneration tower side outlet of the supply 16, that is, in the vicinity of the inlet, and the pressure and temperature applied to the absorbing liquid A1 are maintained until immediately before the inlet to the regeneration tower 20. Then, the pressure is released into the regeneration tower 20 and released from the pressurized state to reduce the pressure, so that the pressure in the regeneration tower 20 becomes equal. In addition, a retreat path 42 and a flow rate control valve 43 branched from the supply path 16 are provided on the upstream side of the heat exchanger 24 in order to release excess pressure. The flow rate control valve 43 is electrically connected to a pressure sensor 44 that detects the hydraulic pressure in the supply path 16, and adjusts the opening degree of the flow rate control valve 43 according to the detected pressure, thereby retreating from the supply path 16. The flow rate of the absorbing liquid retreating to 42 is changed so that the pressure of the absorbing liquid A1 in the heat exchanger 24 is maintained at a predetermined value. That is, the pressure of the absorbing liquid A1 flowing through the heat exchanger 24 can be adjusted without requiring control of the driving force of the pump 12. The absorption liquid A1 in the retreat path 42 is refluxed to the bottom of the absorption tower 10. The flow rate of the absorption liquid A1 flowing through the supply path 16 is adjusted by the flow rate adjustment valve 45 so as to be equal to the flow rate of the absorption liquid A2 in the reflux path 17. In this embodiment, the flow control valve 45 is disposed on the inlet side of the heat exchanger 24, that is, between the pump 12 and the heat exchanger 24, but this position is on the outlet side of the heat exchanger 24, that is, It may be changed between the heat exchanger 24 and the back pressure valve 41.

  In the above embodiment, the pump 12 that exhibits a higher driving force than the driving force required to pressurize the absorbing liquid is used to release excess pressure from the retreat path 42. It is possible to eliminate the influence of fluctuations in If the pump 12 having a function of adjusting the driving force is used, the driving force of the pump 12 is directly controlled according to the detection value of the pressure sensor 44 without providing the retreat path 52 and the flow rate adjusting valve 43. The pressure of the absorbing liquid A1 flowing through the heat exchanger 24 can be adjusted.

  A collection method performed in the collection apparatus 1 of FIG. 2 will be described.

  In the absorption tower 10, when the gas G containing carbon dioxide such as combustion exhaust gas and process exhaust gas is supplied from the bottom and the absorption liquid is supplied from the top, the gas G and the absorption liquid come into gas-liquid contact on the filler 11, Carbon dioxide is absorbed by the absorbing solution. Since carbon dioxide is well absorbed at low temperatures, the liquid temperature of the absorbent or the temperature of the absorption tower 10 (particularly the filler 11) is adjusted so that it is generally about 50 ° C. or lower, preferably 40 ° C. or lower. 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 is also adjusted to an appropriate temperature by the cooling tower 30 in consideration of the above. An aqueous liquid containing a compound having affinity for carbon dioxide as an absorbent is used as the absorbent. Examples of the absorbent include alkanolamines and hindered amines having an alcoholic hydroxyl group, and specific examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, diisopropanolamine, and the like. Examples of the hindered amine having an alcoholic hydroxyl group include 2-amino-2-methyl-1-propanol (AMP), 2- (ethylamino) ethanol (EAE), and 2- (methylamino). ) Ethanol (MAE) and the like can be exemplified. Usually, the use of monoethanolamine (MEA) is preferred, and a plurality of the above compounds may be used in combination. The absorbent concentration of the absorption liquid can be appropriately set according to the amount of carbon dioxide contained in the gas to be processed, the processing speed, etc. A concentration of about 10 to 50% by mass is applied. For example, an absorbent having a concentration of about 30% by mass is suitably used for the treatment of the gas G having a carbon dioxide content of about 20%. The supply rates of the gas G and the absorbing liquid are appropriately set so that the absorption proceeds sufficiently according to the amount of carbon dioxide contained in the gas, the gas-liquid contact efficiency, and the like.

  The absorption liquid A1 that has absorbed carbon dioxide is supplied to the regeneration tower 20 through the supply path 16 by the driving force of the pump 12, and during this time, the pressure of the absorption liquid A1 flowing through the heat exchanger 24 is increased by the back pressure valve 41. , 150 kPaG or higher, preferably 200 kPaG or higher, more preferably 250 kPaG or higher. The pressure of the absorbent A1 flowing through the heat exchanger 24 is set higher than the pressure in the regeneration tower 20 in consideration of the regeneration conditions in the regeneration tower 20. However, in consideration of pressure resistance of equipment and the like, it may be set to about 900 kPaG or less. In the heat exchanger 24, the absorption liquid A <b> 1 is heat-exchanged with the absorption liquid A <b> 2 refluxed from the regeneration tower 20. Since the absorbing liquid A1 is pressurized, the difference between the outlet temperature of the absorbing liquid A1 and the inlet temperature of the absorbing liquid A2 in the heat exchanger 24 can be configured to be less than 10 ° C., and the absorbing liquid A1 is regenerated. The temperature is raised to a temperature close to the heating temperature in the tower 20. The heating temperature of the absorbing liquid A2 in the regeneration tower 20 varies depending on the absorbing liquid composition used and the regeneration conditions, but is generally set to about 100 to 130 ° C. Based on this, the heat exchanger outlet of the absorbing liquid A1 in heat exchange The temperature is raised to about 95-125 ° C. At this time, the absorbing liquid A1 is in a state where it is easy to release carbon dioxide by raising the temperature, but the generation of gas is suppressed by pressurization.

  The absorption liquid A1 supplied to the regeneration tower 20 at a high temperature near the boiling point is released from the back pressure valve 41 as a boundary, and flows down onto the filler 21 while rapidly releasing carbon dioxide. Furthermore, the release of carbon dioxide is promoted by gas-liquid contact on the filler 21, and the temperature rise and the release of carbon dioxide further progress by heating at the bottom of the regeneration tower 20. The absorbent A2 stored in the bottom is heated to the vicinity of the boiling point by partial circulation heating, and the boiling point of the absorbent depends on the composition (absorbent concentration) and the pressure in the regeneration tower 20. At this time, it is necessary to supply the latent heat of vaporization of the water lost from the absorbing liquid and the sensible heat of the absorbing liquid.If the vaporization is suppressed by pressurization, the sensible heat increases due to the rise in boiling point. It is effective in terms of energy efficiency to use a condition setting in which the inside of the regeneration tower 20 is pressurized to about 100 kPaG and the absorbing solution is heated to 120 to 130 ° C. The pressurization in the regeneration tower 20 can be adjusted by controlling a pressure control valve 29 provided at the outlet of the exhaust pipe 34.

  Since the temperature of the upper part of the regeneration tower 20 is close to the temperature of the absorbing liquid A1 to be charged, the recovered gas that has passed through the condensing unit 26 is sufficiently cooled by the cooling water in the cooler 27. Moisture and absorbent condensing from the recovered gas C are separated from the recovered gas C in the gas-liquid separator 28 and supplied to the condensing unit 26 to cool the condensing unit 26 and increase the concentration of the absorbing liquid in the regeneration tower 20. Reduces vaporization and release of absorbent.

  In this way, the absorption liquid circulates between the absorption tower 10 and the regeneration tower 20, and the absorption process and the regeneration process are alternately repeated, and the rich liquid whose heating temperature in the heat exchange is increased by pressurization is charged. This improves the energy efficiency in the regeneration tower.

  2 is provided with a pressure control valve 29 in the exhaust pipe 34 of the regeneration tower 20 so that the pressure can be adjusted by pressurizing the inside of the regeneration tower 20 as necessary. If the atmospheric pressure is set, it may be omitted. Further, although the gas pressure in the absorption tower 10 is set to atmospheric pressure, it may be configured so that the pressure can be adjusted using a pressure control valve in the same manner as the regeneration tower 20, and carbon dioxide recovery of the absorption liquid 10 is possible. When the rate needs to be increased, the pressure may be adjusted to a pressure range of about 120 kPaG or less exceeding normal pressure, preferably about 10 to 100 kPaG.

  FIG. 3 shows another embodiment of a recovery apparatus for implementing the carbon dioxide recovery method of the present invention. The recovery device 2 is a modification of the pressurization control system for the absorbing liquid A1 that flows through the heat exchanger 24. In the supply path 16, the installation position of the flow rate adjustment valve 45 'is changed to the outlet side of the heat exchanger 24, and then retreated. A back pressure valve 46 is used in the passage 42 instead of the flow rate adjusting valve 43.

  In the recovery device 2 of FIG. 3, the liquid pressure of the absorbing liquid A1 by the driving force of the pump 12 is adjusted by the back pressure valve 41 and the back pressure valve 46, and the flow rate of the absorbing liquid A1 in the supply path 17 is constant by the flow rate adjusting valve 45 ′. Therefore, the excess pressure is released when the absorbing liquid A1 recirculates through the back pressure valve 46 and the retreat path 42. Therefore, the pressure sensor 44 does not need to be used for pressurization control, and may be used for monitoring or confirmation. In this embodiment, when the pressure of the absorbing liquid A1 flowing through the heat exchanger 24 can be maintained at a predetermined pressure by adjusting the flow rate of the flow rate adjusting valve 45 ', the back pressure valve 41 can be omitted. Since the points other than those described above are the same as those of the collection device 1 of FIG. 2, the description thereof is omitted.

  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. The cost required for the carbon dioxide recovery process can be reduced, and a carbon dioxide recovery device that can contribute to energy saving and environmental protection can be provided.

1, 2: Recovery device, 10: Absorption tower, 20: Regeneration tower, 30: Cooling tower,
11, 21, 31: Filler, 12, 15, 23, 32, 36, 42: Pump,
13: Cooling condensing part, 14, 25, 27, 33: Cooler, 16: Supply path,
17: Return path, 18: Check valve, 18 ': Air pipe,
19, 29: pressure regulating valve, 19 ', 34: exhaust pipe,
22: Steam heater, 22 ': Circuit, 24: Heat exchanger,
26: condensing part, 28: gas-liquid separator, 35, 43: flow path, 41: liquid level gauge,
44, 46, 47: temperature sensor, 45: flow control valve,
G, G ′: Gas, A1, A2: Absorbing liquid, C: Recovery gas, W: Cooling water.

Claims (9)

An absorption tower in which a gas containing carbon dioxide is brought into contact with the absorption liquid to cause the absorption liquid to absorb carbon dioxide;
A regeneration tower for heating the absorption liquid that has absorbed carbon dioxide in the absorption tower to release carbon dioxide from the absorption liquid to regenerate the absorption liquid;
A supply path for supplying an absorption liquid from the absorption tower to the regeneration tower;
A reflux path for refluxing the absorbent from the regeneration tower to the absorption tower;
A heat exchanger for exchanging heat between the absorption liquid in the supply path supplied from the absorption tower to the regeneration tower and the absorption liquid in the reflux path refluxed from the regeneration tower to the absorption tower;
A back pressure valve is provided between the heat exchanger and the regeneration tower in the supply path, and an absorption liquid supplied from the absorption tower to the regeneration tower is supplied to the heat exchanger in a pressurized state. Pressurizing means for pressurizing the absorbing liquid ,
A retreat path branching off from the supply path for releasing excess pressure in pressurization by the pressurizing means;
Wherein possess a flow regulating valve provided in the evacuation passage, said flow control valve, the absorption liquid carbon dioxide recovery device configured to adjust the opening degree in accordance with the pressure of the said supply channel.   The heat exchanger has a heat at which a difference between the temperature of the absorbent supplied from the heat exchanger to the regeneration tower and the temperature of the absorbent supplied from the regeneration tower to the heat exchanger is less than 10 ° C. The carbon dioxide recovery device according to claim 1, which has exchange efficiency. Furthermore, the hydraulic pressure in the supply channel has a pressure sensor for detecting carbon dioxide recovery apparatus according to claim 1 or 2 opening of the flow regulating valve in accordance with the detected pressure of the pressure sensor is adjusted . An absorption tower in which a gas containing carbon dioxide is brought into contact with the absorption liquid to cause the absorption liquid to absorb carbon dioxide;
A regeneration tower for heating the absorption liquid that has absorbed carbon dioxide in the absorption tower to release carbon dioxide from the absorption liquid to regenerate the absorption liquid;
A supply path for supplying an absorption liquid from the absorption tower to the regeneration tower;
A reflux path for refluxing the absorbent from the regeneration tower to the absorption tower;
A heat exchanger for exchanging heat between the absorption liquid in the supply path supplied from the absorption tower to the regeneration tower and the absorption liquid in the reflux path refluxed from the regeneration tower to the absorption tower;
A back pressure valve is provided between the heat exchanger and the regeneration tower in the supply path, and an absorption liquid supplied from the absorption tower to the regeneration tower is supplied to the heat exchanger in a pressurized state. Pressurizing means for pressurizing the absorbing liquid,
A retreat path branching off from the supply path for releasing excess pressure in pressurization by the pressurizing means;
And a back pressure valve provided in the evacuation passage, pressurized state of the absorbing liquid supplied to the heat exchanger, adjusted Ru dioxide by the back-pressure valve of the evacuation passage and back pressure valve of the supply passage Carbon recovery equipment. An absorption step in which a gas containing carbon dioxide is brought into contact with the absorption liquid to cause the absorption liquid to absorb carbon dioxide;
A regeneration step of regenerating the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide in the absorbing step to release carbon dioxide from the absorbing liquid;
A heat exchange step of exchanging heat between the absorption liquid supplied from the absorption step to the regeneration step and the absorption liquid refluxed from the regeneration step to the absorption step;
In the heat exchange step, the absorption liquid supplied from the absorption step to the regeneration step is heat-exchanged in a pressurized state ,
In order to release the excess pressure in the pressurized state, a retreat path for branching the absorbing liquid supplied from the absorption process to the regeneration process is used, and the retreat path according to the pressure of the absorbing liquid in the pressurized state method for recovering carbon dioxide flow rate Ru alter the absorption liquid to be saved to. An absorption step in which a gas containing carbon dioxide is brought into contact with the absorption liquid to cause the absorption liquid to absorb carbon dioxide;
A regeneration step of regenerating the absorbing liquid by heating the absorbing liquid that has absorbed carbon dioxide in the absorbing step to release carbon dioxide from the absorbing liquid;
A heat exchange step of exchanging heat between the absorption liquid supplied from the absorption step to the regeneration step and the absorption liquid refluxed from the regeneration step to the absorption step;
In the heat exchange step, the absorption liquid supplied from the absorption step to the regeneration step is heat-exchanged in a pressurized state,
Using a retreat path for branching the absorption liquid supplied from the absorption process to the regeneration process, the back pressure of the absorption liquid retreated to the retraction path and the back of the absorption liquid supplied from the absorption process to the regeneration process. A method for recovering carbon dioxide that adjusts the pressurization state according to pressure and releases excess pressure. The heat exchange efficiency in the heat exchange process is such that the difference between the temperature of the absorbent supplied from the heat exchange process to the regeneration process and the temperature of the absorbent supplied from the regeneration process to the heat exchange process is 10 ° C. The method for recovering carbon dioxide according to claim 5 or 6 , wherein the carbon dioxide recovery method is set to be less. The method for recovering carbon dioxide according to any one of claims 5 to 7 , wherein, in the heat exchange step, the absorption liquid supplied from the absorption step to the regeneration step is heat-exchanged in a pressurized state of 150 kPaG or more. . The absorption liquid under pressure supplied to the regeneration step from the absorption step, the carbon dioxide collection methods according to any one of claims 5-8 which is reduced while being turned to the regeneration step.

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