JP2010207729A - System for recovering carbon dioxide from exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for recovering carbon dioxide from exhaust gas, capable of reducing energy required for liquefaction of solid carbon dioxide recovered from the exhaust gas and improving energy efficiency of the entire system. <P>SOLUTION: The carbon dioxide recovery system 10 includes: a pair of carbon dioxide storage and liquefaction tanks 41 and 44 configured to store dry ice and liquid carbon dioxide; lines L5 and L7 for introducing the dry ice from a sublimator 35; lines L6 and L8 for discharging the liquid carbon dioxide; valves 42, 43, 45 and 46 for opening and closing the lines L5, L6, L7 and L8; a dry ice amount detection sensor 62, a temperature sensor 63 and a pressure sensor 64 for monitoring the internal state of the carbon dioxide storage and liquefaction tanks 41 and 44; and a controller 60 for controlling the opening and closing of the valves 42, 43, 45 and 46 on the basis of the monitored results. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a carbon dioxide recovery system from exhaust gas for recovering carbon dioxide contained in combustion exhaust gas (hereinafter referred to as exhaust gas) discharged from a boiler such as a thermal power plant.

  In recent years, the relationship between an increase in the amount of carbon dioxide in the atmosphere and an increase in atmospheric temperature due to the so-called greenhouse effect has been regarded as a problem. For example, exhaust gas from a thermal power plant with a coal-fired boiler is pointed out as one of the sources Has been.

  As a countermeasure, a carbon dioxide recovery device (sublimator) is known that cools exhaust gas containing carbon dioxide to solidify the carbon dioxide into dry ice and recovers carbon dioxide from the exhaust gas by recovering the dry ice. Yes (see, for example, Patent Document 1 and Patent Document 2).

  This conventional carbon dioxide recovery device has a heat transfer tube (for example, a fin tube) for flowing a refrigerant (for example, liquid nitrogen) below the solidification temperature of carbon dioxide inside, and a container for indirectly heat-exchanging the exhaust gas and the refrigerant. It is prepared for.

  The separated solid carbon dioxide (dry ice) is separated from the exhaust gas by a cyclone, and is heated and pressurized by, for example, a dry ice melting machine formed separately from the container and liquefied.

JP 2005-279640 A JP 2007-69057 A

  However, in the above prior art, in order to liquefy solid carbon dioxide, a means for heating or pressurizing solid carbon dioxide is required separately, and heating energy by a heater or the like and power for pressurization are required. Therefore, energy consumption required for liquefaction of solid carbon dioxide was large.

  Therefore, it has been desired to provide means capable of reducing energy required for liquefying solid carbon dioxide recovered from exhaust gas and improving the energy efficiency of the entire system.

  The present invention has been made in view of the above, and can reduce the energy required for liquefying solid carbon dioxide recovered from exhaust gas, and can improve the energy efficiency of the entire system. The purpose is to provide.

  In order to achieve the above object, the present invention provides the following carbon dioxide recovery system from exhaust gas.

  (1) A system for recovering carbon dioxide from exhaust gas comprising a carbon dioxide recovery device that cools and solidifies carbon dioxide from exhaust gas discharged from a boiler and recovers it as solid carbon dioxide, wherein the solid carbon dioxide and liquid carbon dioxide are A pressure vessel configured to be storable, and the carbon dioxide recovery device and the pressure vessel are connected to each other, and an introduction path for introducing the solid carbon dioxide from the carbon dioxide recovery device to the pressure vessel, and opening and closing the introduction path An inlet passage opening / closing means for connecting, a discharge passage for discharging the liquid carbon dioxide from the pressure vessel connected to the pressure vessel, a discharge passage opening / closing means for opening / closing the discharge passage, and a monitoring for monitoring an internal state of the pressure vessel. And a control means for controlling opening and closing of the introduction path opening and closing means and the discharge path opening and closing means based on a monitoring result by the monitoring means, The control means closes the discharge path opening / closing means and opens the introduction path opening / closing means to introduce and store the solid carbon dioxide in the pressure vessel, and to store a predetermined amount of the solid carbon dioxide based on the monitoring result When it has been determined that the introduction path opening and closing means and the discharge path opening and closing means are closed and the pressure vessel is sealed, and based on the monitoring result, it is determined that the solid carbon dioxide has changed to the liquid carbon dioxide Further, the liquid carbon dioxide is discharged by opening the discharge path opening / closing means.

  When the control means determines that a predetermined amount of solid carbon dioxide has been stored in the pressure vessel based on the monitoring result of the monitoring means, the control means closes the introduction path opening / closing means and the discharge path opening / closing means to bring the pressure container into a sealed state. Then, the solid carbon dioxide in the pressure vessel is naturally heated, for example, at room temperature. That is, the solid carbon dioxide is pressurized and liquefied by this natural heating.

  Therefore, according to the invention of (1), since heating energy by a heater or the like is not required to liquefy solid carbon dioxide (dry ice), energy required for liquefying carbon dioxide recovered from exhaust gas is reduced. This can increase the energy efficiency of the entire system.

  (2) In the invention of (1), a plurality of the pressure vessels are provided, and the control means is provided when the solid carbon dioxide is stored in some of the pressure vessels among the plurality of pressure vessels. The solid-state carbon dioxide is liquefied in the pressure vessel, and the solid-state carbon dioxide is stored and liquefied alternately in the pressure vessels. It is preferable to control the opening and closing of the means.

  According to the invention of (2), since storage and liquefaction of solid carbon dioxide are alternately performed in each pressure vessel, liquid carbon dioxide can be continuously generated.

  (3) In the invention described in (1) or (2), the monitoring means includes a solid carbon dioxide amount detecting means for detecting the amount of the solid carbon dioxide in the pressure vessel, and a temperature inside the pressure vessel. It is preferable to include temperature detection means for detecting the pressure and pressure detection means for detecting the pressure inside the pressure vessel.

  According to the invention of (3), the control means can easily detect the amount of solid carbon dioxide stored in the pressure vessel by the solid carbon dioxide amount detection means, and can be obtained by the temperature detection means and the pressure detection means. Since the phase state of carbon dioxide in the pressure vessel can be easily detected from the obtained temperature and pressure information, the introduction path opening / closing means and the discharge path opening / closing means can be controlled to open / close at appropriate timing.

  According to the present invention, energy required for liquefying solid carbon dioxide recovered from exhaust gas can be reduced, and the energy efficiency of the entire system can be increased.

It is the schematic which shows the carbon dioxide collection system which concerns on this embodiment. It is a figure which shows an example of the thermal material balance calculation result in each point of FIG. It is a graph which shows the relationship between the saturation pressure of carbon dioxide, and temperature.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

<Overview of the entire carbon dioxide recovery system>
FIG. 1 is a schematic diagram showing a carbon dioxide recovery system 10 according to the present embodiment. As shown in FIG. 1, the carbon dioxide recovery system 10 is for recovering carbon dioxide from exhaust gas discharged from, for example, a thermal power plant having a coal-fired boiler 11.

  The carbon dioxide recovery system 10 cools and solidifies carbon dioxide from exhaust gas discharged from the boiler 11 and recovers it as solid carbon dioxide (dry ice), and exhaust gas discharged from the boiler 11. An exhaust gas supply path (lines L1, L2, L3, and L4, which will be described later) for supplying to the sublimator 35, and an exhaust gas discharge path (lines L10a, L10b, L11, and L12, which will be described later) that guide the exhaust gas that has passed through the sublimator 35 to the chimney 50. And heat exchangers 13, 14, 15, and 32, a condenser 16 that condenses and removes moisture contained in the exhaust gas, and dryers 20 and 24 that further remove moisture contained in the exhaust gas that has passed through the capacitor 16.

<Explanation of sublimator>
The sublimator 35 is a device that solidifies the carbon dioxide by cooling the exhaust gas containing carbon dioxide discharged from the boiler 11 and collects it as dry ice. The sublimator 35 includes a heat transfer tube for flowing a refrigerant (for example, liquid nitrogen) having a temperature equal to or lower than the solidification temperature of carbon dioxide inside, and is configured to indirectly exchange heat between the exhaust gas and the refrigerant.

  The refrigerant to be circulated through the heat transfer pipe in the sublimator 35 is supplied by the cooler 37 via the refrigerant pipe 38. At the bottom of the sublimator 35, a discharge unit 36 that selectively discharges dry ice generated by the sublimator 35 to a pair of carbon dioxide storage liquefaction tanks 41 and 44 described later is provided. The discharge unit 36 controls the discharge destination of the dry ice by a control device 60 described later. In addition, the liquefaction process of the dry ice produced | generated by the sublimator 35 is mentioned later.

<Description of exhaust gas supply route>
The exhaust gas supply path is a path for supplying the exhaust gas discharged from the boiler 11 to the sublimator 35. That is, the exhaust gas supply path includes a line L1 from the flue 11a of the boiler 11 to the condenser 16, a line L2 from the condenser 16 to the dryers 20, 24, a line L3 from the dryers 20, 24 to the heat exchanger 32, A line L4 extending from the heat exchanger 32 to the sublimator 35.

  The line L1 includes a blower 12 for leading the exhaust gas from the flue 11a and a desulfurization treatment device and a denitration treatment device (not shown) for separating and removing sulfur oxides, nitrogen oxides, etc. contained in the exhaust gas. Is provided. In FIG. 1, the flue 11 a from the boiler 11 includes a bypass line connected to the chimney 50 without passing through the lines L1 to L12. This bypass line is communicated when a malfunction or the like occurs in the component devices (for example, the sublimator 35) included in the lines L1 to L14, and is not communicated during normal operation.

<Explanation of exhaust gas discharge route>
The exhaust gas discharge path is a path through which the exhaust gas that has passed through the sublimator 35 is guided to the chimney 50 and released to the atmosphere. That is, the exhaust gas discharge path includes a line L10a from the sublimator 35 to the heat exchanger 32, a line L10b from the heat exchanger 32 to the heat exchanger 15, a line L11 from the heat exchanger 15 to the heat exchanger 13, A line L12 extending from the heat exchanger 13 to the chimney 50.

<Description of heat exchanger>
The heat exchangers 13, 14, and 15 are provided in a line L1 that is an exhaust gas supply path. The heat exchanger 13 exchanges heat between the high-temperature exhaust gas flowing from the flue 11a and the low-temperature exhaust gas flowing through the line L11 via the heat exchanger 15. Further, the heat exchanger 14 exchanges heat of the exhaust gas that has passed through the heat exchanger 13 with cold seawater. The heat exchanger 15 exchanges heat between the exhaust gas that has passed through the heat exchanger 14 and the low-temperature exhaust gas that has flowed through the line L10b.

  The heat exchanger 32 exchanges heat between the exhaust gas flowing from the line L3 and the low-temperature exhaust gas flowing through the line L10a via the sublimator 35.

<Description of capacitor>
The condenser 16 is provided downstream of the heat exchanger 15 and upstream of the dryers 20 and 24. The condenser 16 condenses and removes moisture contained in the exhaust gas that has passed through the heat exchanger 15. That is, the capacitor 16 is provided to remove moisture from the exhaust gas as much as possible before dehumidifying the exhaust gas by the downstream dryers 20 and 24 and reduce the load when the dryers 20 and 24 dehumidify. The condensed water is discharged out of the system through the drain port 16a.

<Description of dryer>
A pair of dryers 20, 24 are provided on the downstream side of the capacitor 16 provided in the line L1. The dryers 20 and 24 further remove moisture contained in the exhaust gas that has passed through the capacitor 16. The dryers 20 and 24 include a moisture adsorbent that adsorbs moisture in the exhaust gas and discharges and regenerates moisture adsorbed when heated. For example, activated alumina is preferably used as the moisture adsorbent.

  The pair of dryers 20 and 24 is configured such that when one is adsorbing moisture, the other can release (regenerate) the adsorbed moisture. That is, it is configured so that continuous dehumidification can be performed by the dryers 20 and 24 during operation of the boiler 11.

  The pair of dryers 20, 24 and the capacitor 16 are connected by a line L2. The line L2 is branched into a line L2a connected to the dryer 20 and a line L2b connected to the dryer 24. The line L2a is provided with a valve 21 that opens and closes the flow path. The line L2b is provided with a valve 27 that opens and closes the flow path.

  For convenience of explanation, the valve 21 is in an open state and is displayed in white. Further, the valve 27 is in a closed state and is displayed in black. Such a display method is the same for the other valves 22, 25, 26, 28, 29, 30 and valves 42, 43, 45, 46 described later.

  The dryers 20 and 24 are connected to the heat exchanger 32 by a line L3. The line L3 branches into a line L3a connected to the dryer 20 and a line L3b connected to the dryer 24. The line L3a is provided with a valve 22 (opened state in FIG. 1) for opening and closing the flow path. The line L3b is provided with a valve 28 (a closed state in FIG. 1) for opening and closing the flow path.

<Description of regeneration exhaust gas supply route>
The regeneration exhaust gas supply path includes a line L13 connecting the line L12 to the line L3. The line L13 supplies a part of the hot exhaust gas flowing through the line L12 that has passed through the heat exchanger 13 to the dryers 20 and 24 in order to regenerate the moisture adsorbent of the dryers 20 and 24.

  The line L13 branches into a line L13a connected to the dryer 24 (line L3b) and a line L13b connected to the dryer 20 (line L3a). The line L13a is provided with a valve 25 (opened state in FIG. 1) for opening and closing the flow path. The line L13b is provided with a valve 29 (opened state in FIG. 1) for opening and closing the flow path.

<Description of exhaust gas recirculation route>
The exhaust gas recirculation path includes a line L14 that connects the line L2 to the line L12. The line L14 returns the exhaust gas supplied from the line L13 and passed through the dryers 20 and 24 to the line L12. The line L14 is branched into a line L14a connected to the dryer 24 (line L2b) and a line L14b connected to the dryer 20 (line L2a).

  The line L14a is provided with a valve 26 (opened state in FIG. 1) for opening and closing the flow path. The line L14b is provided with a valve 30 (a closed state in FIG. 1) for opening and closing the flow path.

<Description of configuration for storing and liquefying dry ice>
Further, the carbon dioxide recovery system 10 includes a pair of carbon dioxide storage liquefaction tanks (pressure vessels) 41 and 44 configured to be able to store dry ice and liquid carbon dioxide, and the sublimator 35 to the carbon dioxide storage liquefaction tanks 41 and 44. Lines (introduction paths) L5 and L7 for introducing dry ice, valves (introduction path opening / closing means) 42 and 45 for opening and closing the lines L5 and L7, and lines (exhaust paths) L6 and L8 for discharging liquid carbon dioxide from And valves (discharge path opening / closing means) 43 and 46 for opening and closing the lines L6 and L8.

  The carbon dioxide recovery system 10 includes a dry ice amount detection sensor (monitoring means, solid carbon dioxide amount detection means) 62 for monitoring the internal state of the carbon dioxide storage liquefaction tanks 41 and 44, a temperature sensor (monitoring means, temperature detection means). ) 63 and a pressure sensor (monitoring means, pressure detecting means) 64.

  Further, the carbon dioxide recovery system 10 includes a control device (control means) 60 that controls opening and closing of the valves 42 and 45 and the valves 43 and 46 based on the monitoring results of the dry ice amount detection sensor 62, the temperature sensor 63, and the pressure sensor 64. Prepare.

  The pair of carbon dioxide storage liquefaction tanks 41 and 44 is provided in order to continuously generate liquid carbon dioxide by using one for storing dry ice and using the other for liquefying dry ice. The storage and liquefaction of dry ice are alternately performed in the carbon dioxide storage liquefaction tanks 41 and 44 by the opening / closing control of the valves 42, 43, 45 and 46 by the controller 60.

  The line L5 connects the discharge part 36 and the upper end part of the carbon dioxide storage liquefaction tank 41. The line L7 connects the discharge part 36 and the upper end part of the carbon dioxide storage liquefaction tank 44. The lines L5 and L7 are provided with valves 42 and 45 for opening and closing the flow paths, respectively.

  The line L6 is connected to the lower end of the carbon dioxide storage liquefaction tank 41 and discharges liquefied carbon dioxide. The line L8 is connected to the lower end of the carbon dioxide storage liquefaction tank 44 and discharges liquefied carbon dioxide.

  The lines L6 and L8 are provided with valves 43 and 46 for opening and closing the flow paths, respectively. The lines L6 and L8 are connected to a line L9 for sending liquefied carbon dioxide out of the system. The line L9 includes a pressure pump (not shown) for sending liquefied carbon dioxide out of the system.

  The carbon dioxide storage liquefaction tanks 41 and 44 detect a dry ice amount detection sensor 62 that detects the amount of dry ice stored in the tank, a temperature sensor 63 that detects the temperature inside the tank, and a pressure inside the tank. And a pressure sensor 64.

  The control device 60 determines whether or not a predetermined amount of dry ice has been stored in the carbon dioxide storage liquefaction tanks 41 and 44 based on the output result from the dry ice amount detection sensor 62.

  Further, the control device 60 determines whether or not the dry ice in the carbon dioxide storage liquefaction tanks 41 and 44 has been liquefied based on the temperature data obtained from the temperature sensor 63 and the pressure data obtained from the pressure sensor 64. That is, as shown in FIG. 3, the control device 60 stores in advance data indicating the relationship between the saturation pressure of carbon dioxide and the temperature. From the data and the temperature data and pressure data, dry ice is stored. Determine whether it has liquefied.

  In addition, the control device 60 controls the discharge unit 36 to discharge the dry ice from the sublimator 35 to one of the carbon dioxide storage liquefaction tanks 41 and 44.

<Description of the action and effect of the entire carbon dioxide recovery system>
Next, the operation (action and effect) of the carbon dioxide recovery system 10 will be described with reference to FIGS. Here, FIG. 2 is a figure which shows an example of the thermal mass balance calculation result in each point (point P1-point P14) of FIG.

  That is, FIG. 2 shows the phase type, temperature, pressure, average molecular weight, molar flow rate, and composition of the exhaust gas at each point (points P1 to P14) in FIG. FIG. 3 is a graph showing the relationship between the saturation pressure of carbon dioxide and the temperature.

  As shown in FIGS. 1 and 2, the exhaust gas discharged from the boiler 11 flows from the flue 11 a through the line L <b> 1 toward the heat exchanger 13. The exhaust gas has a temperature of about 110 ° C. at a point P1 of the line L1, and is heated and pressured by being sucked in at 12. The exhaust gas has a temperature of about 128.6 ° C. at a point P 2 that is the inlet of the heat exchanger 13.

  The exhaust gas introduced into the heat exchanger 13 is heat-exchanged with the low-temperature exhaust gas flowing through the line L11 (the temperature is about 9.4 ° C. at the point P11), so that the outlet temperature at the point P3 is about 60 ° C. And in the heat exchanger 14, the exit temperature in the point P4 will be about 15 degreeC by exchanging heat with seawater, for example. In addition, the inlet temperature of seawater at this time is about 15 ° C., and the outlet temperature is about 21.7 ° C.

  Subsequently, in the heat exchanger 15, the outlet temperature at the point P5 becomes about 5 ° C. by exchanging heat with the low-temperature exhaust gas flowing through the line L10b (the temperature is about −18.9 ° C. at the point P10). As shown in FIG. 2, the exhaust gas flowing through the line L1 is a gas from the point P1 to the point P3, but at the points P4 and P5, the moisture is mixed by about 11.4% and is in a gas-liquid mixed state. .

  Therefore, the capacitor 16 removes moisture from the exhaust gas as condensed water. As a result, at the point P6 in the line L2 on the downstream side of the capacitor 16, the moisture ratio can be reduced to about 0.7%.

  Thus, by removing most of the moisture contained in the exhaust gas on the outlet side of the condenser 16, that is, on the inlet side (upstream side) of the dryers 20, 24, the load when dehumidifying with the dryers 20, 24 is reduced. Can be reduced. The condensed water removed by the condenser 16 (the temperature is about 5 ° C. at the point P14) is discharged out of the system from the drain port 16a.

<Description of actions and effects in dryer>
The exhaust gas that has passed through the condenser 16 travels through the line L2, and further travels through the lines L2a and L2b. In FIG. 1, since the dryer 20 is used for moisture adsorption and the dryer 24 is used for regeneration of the moisture adsorbent, the valves 27, 28, 29, and 30 are closed and the valve 21 is closed. , 22, 25, 26 are opened. Therefore, the exhaust gas is introduced into the dryer 20 through the line L2a.

  The exhaust gas is adsorbed by the moisture adsorbent filled in the dryer 20, flows through the line L <b> 3 a, and is introduced into the heat exchanger 32. Since activated alumina is used as the moisture adsorbent of the dryer 20, the moisture contained in the exhaust gas can be completely removed as shown in the composition at the point P7 (see FIG. 2).

  Further, since the moisture of the exhaust gas is easily removed by the adsorption of the moisture adsorbent, energy for cooling the dehumidifying refrigerant such as a conventional bubbling dryer is unnecessary. For this reason, energy required for removing moisture from the exhaust gas can be reduced, and carbon dioxide can be efficiently recovered. The regeneration of the moisture adsorbent in the dryer 24 will be described later.

  The exhaust gas introduced into the heat exchanger 32 has a temperature of about 5 ° C. at the point P 7, but exchanges heat with the low-temperature exhaust gas having a temperature of about −117 ° C. at the point P 9 that has flowed through the line L 10 a through the sublimator 35. As a result, the temperature at the point P8 decreases to about -78 ° C. As a result, the temperature of the exhaust gas can be lowered before the exhaust gas is introduced into the sublimator 35, and the cooling load in the sublimator 35 can be reduced.

  The exhaust gas introduced from the line L4 into the sublimator 35 contacts a heat transfer tube that flows a refrigerant (for example, liquid nitrogen) that is equal to or lower than the solidification temperature of carbon dioxide, and indirectly exchanges heat with the refrigerant flowing in the heat transfer tube. Under the conditions of a temperature of about −117 ° C. and a pressure of 0.107 MPa (see point P9 in FIG. 2), the carbon dioxide in the exhaust gas is cooled and solidified into dry ice as shown in FIG. Dry ice is stored in the sublimator 35.

  At this time, since the moisture has already been completely removed from the exhaust gas introduced into the sublimator 35, the generated dry ice does not contain moisture. Therefore, dry ice that does not contain moisture is less likely to adhere to the heat transfer tube in the sublimator 35, and it is possible to suppress a decrease in heat transfer efficiency.

  The dry ice stored in the sublimator 35 is selectively sent from the discharge unit 36 to the carbon dioxide storage liquefaction tanks 41 and 44. And it stores in the carbon dioxide storage liquefaction tanks 41 and 44, and is liquefied. The dry ice liquefaction process will be described later.

  The exhaust gas that has passed through the sublimator 35 passes through the line L10a and is introduced into the heat exchanger 32. At the point P9 of the line L10a, the composition of carbon dioxide in the exhaust gas is about 1.7%, so that it can be seen that the carbon dioxide can be almost recovered by the sublimator 35.

  The exhaust gas introduced into the heat exchanger 32 has a temperature of about −117 ° C. at the point P9, but is to exchange heat with the exhaust gas flowing through the line L3 through the dryer 20 (the temperature is about 5 ° C. at the point P7). As a result, the temperature at the point P10 rises to about −18.9 ° C.

  The exhaust gas that has passed through the heat exchanger 32 is introduced into the heat exchanger 15 through the line L10b. In this heat exchanger 15, the exhaust gas is heated to the temperature of about 9.4 ° C. (see point P 11) by exchanging heat with the exhaust gas that has passed through the heat exchanger 14 (temperature is about 15 ° C. at point P 4).

<Description of dryer regeneration>
The exhaust gas that has passed through the heat exchanger 15 is introduced into the heat exchanger 13 through the line L11. In this heat exchanger 13, the exhaust gas is heat-exchanged with the high-temperature exhaust gas discharged from the boiler 11 (the temperature is about 128.6 ° C. at the point P2), so that the temperature is about 104.7 ° C. (see the point P12). To rise.

  The exhaust gas at 100 ° C. or higher (hot air from which moisture and carbon dioxide have been removed) is suitable as a heat source for regenerating the moisture adsorbent containing the moisture in the dryers 20 and 24, so that part of the exhaust gas is removed by the line L13. Introduced into the dryers 20,24.

  That is, as the heat source for regenerating the dryers 20 and 24, the heat of the exhaust gas immediately before being released to the atmosphere is used, so that the heating energy for regeneration is not necessary. Thereby, energy required for removing moisture from the exhaust gas can be reduced, and carbon dioxide can be efficiently recovered.

  As described above, in FIG. 1, since the dryer 20 is used for moisture adsorption and the dryer 24 is used for regeneration of the moisture adsorbent, the valves 27, 28, 29, and 30 are closed and the valve 21 is closed. , 22, 25, 26 are opened. Therefore, the exhaust gas flowing through the line L13 passes through the line L13a and is introduced into the dryer 24.

  In the dryer 24, the moisture adsorbent containing moisture is exposed to high-temperature exhaust gas (the temperature is about 104.7 ° C. at the point P12), moisture is removed, and regeneration is performed. The exhaust gas introduced into the dryer 24 and used to regenerate the moisture adsorbent is recirculated to the line L12 through the lines L14a and L14, and is released from the chimney 50 to the atmosphere.

  As described above, the case where the dryer 20 is used for moisture adsorption and the dryer 24 is used for regeneration of the moisture adsorbent has been described. However, under a predetermined condition, the dryer 24 is used for moisture adsorption, and the dryer 20 is used for moisture. The exhaust gas flow path is switched to be used for adsorbent regeneration.

  Here, the predetermined condition refers to a case where the moisture adsorption capability (dehumidification capability) of the dryer 20 is lowered and the regeneration of the dryer 24 is completed. Since the target dehumidification amount with respect to a predetermined exhaust gas flow rate and the dehumidification / regeneration capability of the dryers 20 and 24 are known, for example, the valves 27, 28, 29, and 30 are opened at predetermined intervals, and the valves 21, 22, 25 are opened. , 26 are closed, the flow path can be switched.

  As described above, the moisture removal of the exhaust gas is performed by using the dryer 20 or the dryer 24 in which the dehumidifying ability is regenerated by alternately switching the moisture adsorption and the moisture adsorbent regeneration in the pair of dryers 20 and 24. Can be performed continuously, and carbon dioxide can be efficiently recovered.

<Description of storage and liquefaction of dry ice>
Next, the operation of the carbon dioxide recovery system 10 relating to liquefaction of dry ice will be described. In FIG. 1, the carbon dioxide storage liquefaction tank 41 stores dry ice (the temperature is about −117 ° C. at point P13), and the carbon dioxide storage liquefaction tank 44 stores the stored dry ice at room temperature (for example, about 15 ° C.). ) After being naturally liquefied, it is shown discharged to the line L9 via the line L8.

  As described above, the valves 42, 43, 45, 46 are opened and closed by the control device 60. That is, when storing the dry ice generated by the sublimator 35 in the carbon dioxide storage liquefaction tank 41, the valve 42 is opened and the valve 43 is closed. And the dry ice discharged | emitted from the discharge part 36 is introduce | transduced into the carbon dioxide storage liquefaction tank 41 from the line L5, and is stored.

  The control device 60 determines whether or not a predetermined amount of dry ice has been stored in the carbon dioxide storage liquefaction tank 41 based on the output result from the dry ice amount detection sensor 62. When it is determined that a predetermined amount of dry ice is stored in the carbon dioxide storage liquefaction tank 41, the carbon dioxide storage liquefaction tank 41 is hermetically closed by closing the valve 42, and dry ice liquefaction described later is performed.

  On the other hand, in the carbon dioxide storage liquefaction tank 44, dry ice stored in advance is liquefied naturally. That is, in the carbon dioxide storage liquefaction tank 44, dry ice is stored in advance with the valve 45 opened and the valve 46 closed.

  The control device 60 determines whether or not a predetermined amount of dry ice has been stored in the carbon dioxide storage liquefaction tank 44 based on the output result from the dry ice amount detection sensor 62. When it is determined that a predetermined amount of dry ice has been stored in the carbon dioxide storage liquefaction tank 44, the carbon dioxide storage liquefaction tank 44 is closed by closing the valve 45.

  Then, since the dry ice just stored in the carbon dioxide storage liquefaction tank 44 has a temperature of about −117 ° C., it is heated by air outside the carbon dioxide storage liquefaction tank 44 at room temperature (for example, about 15 ° C.). It will be warmed. That is, even without heating by a heat source such as a heater, the dry ice is gradually self-pressurized (for example, about 50 MPa) and liquefies naturally (see FIG. 3).

  Thus, since the energy for heating by a heater etc. is not required in order to liquefy dry ice, the energy efficiency of the carbon dioxide recovery system 10 whole can be improved. In addition, you may use the waste heat of the cooler 37 as a heat source for a heating for promoting liquefaction of dry ice.

  The control device 60 determines whether the dry ice in the carbon dioxide storage liquefaction tank 44 has been liquefied based on the temperature data obtained from the temperature sensor 63 and the pressure data obtained from the pressure sensor 64. That is, the control device 60 determines whether or not dry ice has been liquefied from data indicating the relationship between the saturation pressure of carbon dioxide and the temperature (see FIG. 3) and the temperature data and pressure data.

  When the control device 60 determines that the dry ice is liquefied in the carbon dioxide storage liquefaction tank 44, as shown in FIG. 1, the control device 60 opens the valve 46 and discharges the liquid carbon dioxide to the line L9 via the line L8. .

  When all the liquid carbon dioxide in the carbon dioxide storage liquefaction tank 44 is discharged, the carbon dioxide storage liquefaction tank 44 is used for storing dry ice, while the carbon dioxide storage liquefaction tank 41 is used for liquefying dry ice.

  That is, the control device 60 closes the valve 46 and opens the valve 45 to store dry ice in the carbon dioxide storage liquefaction tank 44.

  Further, as described above, the control device 60 closes the valve 42 and the valve 43, and the carbon dioxide storage liquefaction tank 41 also liquefies dry ice on the same principle as that of the carbon dioxide storage liquefaction tank 44. I do.

  Whether or not the dry ice is liquefied in the carbon dioxide storage liquefaction tank 41 is obtained from the temperature data obtained from the temperature sensor 63 and the pressure sensor 64 in the same manner as the carbon dioxide storage liquefaction tank 44 described above. Judgment based on pressure data.

  When it is determined that the dry ice has been liquefied, the control device 60 opens the valve 43 and discharges liquid carbon dioxide to the line L9 via the line L6.

  As described above, the control device 60 determines the storage amount of dry ice and the liquefaction timing of dry ice based on the information obtained from the dry ice amount detection sensor 62, the temperature sensor 63, and the pressure sensor 64 to determine the valves 42, 43, 45 and 46 are opened and closed, and dry ice storage and liquefaction are alternately repeated. Thereby, liquid carbon dioxide can be continuously generated. In addition, the liquefied carbon dioxide discharged | emitted out of the system from the line L9 is stored and conveyed suitably and can be utilized effectively.

  As described above, according to the carbon dioxide recovery system 10 according to this embodiment, since energy for heating by a heater or the like is not required to liquefy dry ice, the energy efficiency of the carbon dioxide recovery system 10 as a whole. Can be improved.

  Also, a pair of carbon dioxide storage liquefaction tanks 41 and 44 are provided, and storage and liquefaction of dry ice are alternately performed in the respective carbon dioxide storage liquefaction tanks 41 and 44, so that liquid carbon dioxide is continuously generated. can do.

  Moreover, according to the carbon dioxide recovery system 10, the following effects are also achieved.

  That is, since the moisture of the exhaust gas can be easily removed by the adsorption of the moisture adsorbent of the dryers 20 and 24, energy for cooling the dehumidifying refrigerant such as a conventional bubbling dryer is unnecessary.

  Further, since the heat of the exhaust gas immediately before being released to the atmosphere is used as a heat source for regenerating the dryers 20 and 24, the heating energy for regeneration is not necessary. Therefore, energy required for removing moisture from the exhaust gas can be reduced, and carbon dioxide can be efficiently recovered. For example, according to the carbon dioxide recovery system 10 according to the present embodiment, it has been confirmed that the carbon dioxide recovery rate is about 90%.

  Further, by using activated alumina, which has a large moisture adsorption capacity and is a general-purpose moisture adsorbent, moisture can be efficiently removed from exhaust gas at low cost.

  Further, since the moisture in the exhaust gas introduced into the sublimator 35 has already been completely removed by the dryers 20 and 24, the generated dry ice does not contain moisture. Therefore, dry ice that does not contain moisture is less likely to adhere to the heat transfer tube in the sublimator 35, and it is possible to suppress a decrease in heat transfer efficiency. Thereby, carbon dioxide can be efficiently recovered.

  Further, the moisture removal of the exhaust gas is continuously performed by using the dryer 20 or the dryer 24 in which the dehumidifying ability is regenerated by alternately switching the moisture adsorption and the moisture adsorbent regeneration in the pair of dryers 20 and 24. Carbon dioxide can be efficiently recovered.

  Further, by providing the capacitor 16, most of the moisture contained in the exhaust gas can be removed on the outlet side of the capacitor 16, that is, on the inlet side (upstream side) of the dryers 20, 24. The load at the time of dehumidification can be reduced.

  In addition, by providing the heat exchanger 32, the temperature of the exhaust gas can be lowered before the exhaust gas is introduced into the sublimator 35, and the cooling load in the sublimator 35 can be reduced. Therefore, carbon dioxide can be efficiently recovered.

  In the above embodiment, the carbon dioxide recovery system 10 has been described as including two carbon dioxide storage liquefaction tanks 41 and 44 as pressure vessels. However, the present invention is not limited to this, and the scale of the boiler 11 and the liquefaction should be liquefied. Depending on the amount of carbon dioxide, three or more carbon dioxide storage liquefaction tanks may be provided.

  Moreover, in the said embodiment, although an example of the thermal material balance calculation result in each point P1-P14 was shown in FIG. 2, embodiment which concerns on this invention is not limited to these numerical values.

10 Carbon dioxide recovery system 11 Boiler 42, 45 Valve (Introduction path opening / closing means)
43, 46 Valve (Discharge path opening / closing means)
35 Sublimator (carbon dioxide recovery device)
41,44 Carbon dioxide storage liquefaction tank (pressure vessel)
60 Control device (control means)
62 Dry ice amount detection sensor (monitoring means, solid carbon dioxide amount detection means)
63 Temperature sensor (monitoring means, temperature detection means)
64 Pressure sensor (monitoring means, pressure detecting means)
L5 and L7 lines (introduction route)
L6, L8 line (discharge path)

Claims (3)

A carbon dioxide recovery system from exhaust gas equipped with a carbon dioxide recovery device that cools and solidifies carbon dioxide from exhaust gas discharged from a boiler and recovers it as solid carbon dioxide,
A pressure vessel configured to store the solid carbon dioxide and liquid carbon dioxide;
Connecting the carbon dioxide recovery device and the pressure vessel, and introducing the solid carbon dioxide from the carbon dioxide recovery device to the pressure vessel;
An introduction path opening and closing means for opening and closing the introduction path;
A discharge path connected to the pressure vessel for discharging the liquid carbon dioxide from the pressure vessel;
A discharge path opening and closing means for opening and closing the discharge path;
Monitoring means for monitoring the internal state of the pressure vessel;
Control means for controlling opening and closing of the introduction path opening and closing means and the discharge path opening and closing means based on a monitoring result by the monitoring means;
With
The control means includes
Closing the discharge path opening and closing means, introducing and storing the solid carbon dioxide in the pressure vessel by opening the introduction path opening and closing means,
When it is determined that a predetermined amount of the solid carbon dioxide has been stored based on the monitoring result, the introduction path opening / closing means and the discharge path opening / closing means are closed to seal the pressure vessel,
When it is determined that the solid carbon dioxide has changed to the liquid carbon dioxide based on the monitoring result, the carbon dioxide recovery from the exhaust gas is characterized by opening the discharge path opening / closing means and discharging the liquid carbon dioxide. system. A plurality of the pressure vessels,
The control means is configured to perform liquefaction of the solid carbon dioxide in another pressure vessel when the solid carbon dioxide is stored in some of the pressure vessels among the plurality of pressure vessels, and 2. The exhaust gas according to claim 1, wherein the introduction path opening / closing means and the discharge path opening / closing means are controlled to be opened and closed so that storage and liquefaction of solid carbon dioxide are alternately performed in each of the pressure vessels. Carbon dioxide capture system. The monitoring means includes
Solid carbon dioxide content detection means for detecting the amount of solid carbon dioxide in the pressure vessel;
Temperature detecting means for detecting the temperature inside the pressure vessel;
Pressure detecting means for detecting the pressure inside the pressure vessel;
The system for recovering carbon dioxide from exhaust gas according to claim 1 or 2, characterized by comprising:

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