Regeneration tower, control device and control method

Abstract

To provide a method for stabilizing control of a CO2 recovery device having a regeneration tower with a thermosiphon part.SOLUTION: A regeneration tower for a CO2 recovery device includes: a first regeneration part that stores absorbing liquid to be supplied from an absorption tower to the regeneration tower of the CO2 recovery device; a second regeneration part provided below the first regeneration part; and a thermosiphon part that is piping connected from the lower part of the first regeneration part via a heat exchanger to the upper part of the second regeneration part. The absorbing liquid is supplied from the first regeneration part through the thermosiphon part to the second regeneration part. In pipelines disposed in the liquid phase portion on the preceding flowing side of the heat exchanger out of the pipelines constituting the thermosiphon part, the volume of the pipeline provided in a range where liquid level height of the absorbing liquid fluctuates and disposed horizontally is smaller than that allowed to fluctuate of the absorbing liquid stored in the second regeneration part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a regeneration tower, a control device, and a control method. [Background technology]

[0002] A CO2 capture device circulates an absorbing liquid between a regenerator and an absorber, and captures CO2 from exhaust gas discharged from a boiler, a gas turbine, or the like. In order to efficiently regenerate the absorbing liquid, a regenerator is provided that is equipped with a plurality of regenerator sections in the vertical direction and configured to supply the absorbing liquid stored in the upper regenerator section to the lower regenerator section. For example, according to Patent Document 1, the regenerator section of each stage has, from the top, a liquid dispersion section, a packing section, and a tray section, and the absorbing liquid is taken into the regenerator section through the liquid dispersion section and supplied to the lower packing section. CO2 is released from the absorbing liquid while it flows down through the packing section, and the absorbing liquid from which CO2 has been released falls into the tray section. In general, in order to supply the absorbing liquid stored in the upper regenerator section to the lower regenerator section, the absorbing liquid is transported by a pump and the flow rate of the absorbing liquid is adjusted by a flow control valve. In response to this, Patent Document 1 discloses a configuration in which a supply pipe is provided to guide the absorbing liquid stored in the tray section of the first regenerator on the upper side to a liquid dispersion section provided at the top of the second regenerator on the lower side, and a heat exchanger is provided on the supply pipe. According to this configuration, the absorbing liquid can be circulated from the tray section to the liquid dispersion section of the second regenerator using the density difference between the absorbing liquid upstream and downstream of the heat exchanger as a driving force (thermosiphon effect), and the absorbing liquid can be supplied to the second regenerator. According to the technology of Patent Document 1, the absorbing liquid can be supplied from the first regenerator on the upper side to the second regenerator on the lower side without using a pump. Hereinafter, the absorbing liquid supply pipe equipped with a heat exchanger provided to supply the absorbing liquid from the regenerator on the upper side to the regenerator on the lower side may be referred to as a thermosiphon section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5968450 Summary of the Invention [Problem to be solved by the invention]

[0004] Fluctuations in the load on the CO2 capture unit cause fluctuations in the flow rate of the absorbing solution circulating through the supply pipe (thermosiphon section). Fluctuations in the flow rate of the absorbing solution can cause the liquid level of the absorbing solution stored at the bottom of the regeneration tower to exceed the allowable range, which can lead to unstable control of the CO2 capture unit.

[0005] The present disclosure provides a regenerator, a control device, and a control method that can solve the above problems. [Means for solving the problem]

[0006] The regeneration tower of the present disclosure is a regeneration tower of a CO2 recovery equipment, and includes a first regeneration section for storing an absorbing liquid supplied to the regeneration tower from an absorption tower of the CO2 recovery equipment, a second regeneration section provided below the first regeneration section, and a thermosiphon section which is a pipe connected from the lower part of the first regeneration section to the upper part of the second regeneration section via a heat exchanger, and the second regeneration section is supplied with the absorbing liquid from the first regeneration section through the thermosiphon section, and the volume of the pipes constituting the thermosiphon section, which are arranged horizontally within the range in which the liquid level of the absorbing liquid fluctuates in the liquid phase portion upstream of the heat exchanger, is smaller than the volume of the absorbing liquid stored in the second regeneration section that is allowed to fluctuate.

[0007] The control device disclosed herein is a control device for a CO2 recovery device including the above-mentioned regeneration tower and absorption tower, and calculates the valve openings of the first flow rate control valve and the second flow rate control valve to optimize the liquid level of the thermosiphon section so that the liquid level of the tower bottom is constant, based on a first model that represents the relationship between a fluctuation in the liquid level of the thermosiphon section, a first flow rate based on a valve opening of a first flow rate control valve that adjusts the first flow rate, which is the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower, and a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a second model that represents the relationship between a fluctuation in the tower bottom liquid level, which is the liquid level of the absorbing liquid stored in the second regeneration section, and the second flow rate based on a valve opening of a second flow rate control valve that adjusts the second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate.

[0008] The control method of the present disclosure is a control method for a CO2 recovery apparatus having a first regeneration section that stores an absorbing liquid supplied from an absorption tower to a regeneration tower of a CO2 recovery apparatus, a second regeneration section provided below the first regeneration section, and a thermosiphon section that is a pipe connected from a lower part of the first regeneration section to an upper part of the second regeneration section via a heat exchanger, the second regeneration section including a regeneration tower to which the absorbing liquid is supplied from the first regeneration section through the thermosiphon section, and an absorption tower, the control method including: Based on a first model that represents the relationship between the first flow rate and the circulation flow rate of the absorption liquid flowing through the thermosiphon section, and a second model that represents the relationship between fluctuations in the tower bottom liquid level, which is the liquid level of the absorption liquid stored in the second regeneration section, and the second flow rate based on a valve opening of a second flow control valve that adjusts the second flow rate, which is the flow rate of the absorption liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate, the valve openings of the first flow control valve and the second flow control valve that optimize the liquid level in the thermosiphon section so that the tower bottom liquid level is constant are calculated, and the first flow control valve and the second flow control valve are controlled with the calculated valve openings. Effect of the Invention

[0009] According to the above-described regenerator, control device, and control method, it is possible to stabilize the control of a CO2 recovery device including a regenerator provided with a thermosiphon unit. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a CO2 capture device according to an embodiment. [Diagram 2] FIG. 1 is a diagram illustrating an example of a general thermosiphon unit. [Figure 3A] FIG. 1 is a first diagram showing a configuration example of a thermosiphon unit according to a first embodiment. [Figure 3B] FIG. 2 is a second diagram showing an example of the configuration of the thermosiphon unit according to the first embodiment. [Figure 4] 5A to 5C are diagrams illustrating a method for calculating the fluctuation range of the liquid level according to the first embodiment. [Diagram 5] FIG. 11 is a diagram illustrating an example of a mathematical expression model according to a second embodiment. [Figure 6] 10 is a flowchart showing an example of control according to the second embodiment. [Figure 7] 13 is a flowchart showing an example of control according to the third embodiment. [Figure 8] FIG. 13 is a diagram illustrating an example of setting a flow rate set value according to an operating load according to the fourth embodiment. [Figure 9] 13 is a flowchart showing an example of control according to the fourth embodiment. [Figure 10] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a CO2 recovery apparatus according to the present disclosure will be described with reference to the drawings. First Embodiment (composition) FIG. 1 shows an example of a schematic configuration of a CO2 recovery device 100 according to each embodiment. As shown in FIG. 1, the CO2 recovery system 100 includes a control device 1, an absorption tower 2, a regeneration tower 3, a heat exchanger 4, and the like. Exhaust gas 80 discharged from an industrial combustion facility such as a boiler or a gas turbine is cooled and sent to the absorption tower 2 of the CO2 recovery system 100. In the absorption tower 2, the exhaust gas 80 comes into contact with an absorbing liquid, and the CO2 in the exhaust gas 80 is absorbed by the absorbing liquid through a chemical reaction. The absorbing liquid that has absorbed the CO2 is called a rich solution. The exhaust gas 80 after the CO2 is removed in the absorption tower 2 is discharged outside the system. The rich solution is pressurized by a pump 21 and sent to the heat exchanger 4 through a pipe 53. In the heat exchanger 4, the rich solution is heated by a lean solution that has been regenerated in the regeneration tower 3 and has a higher temperature than the rich solution, and is supplied to the regeneration tower 3 through a pipe 54.

[0012] The rich solution supplied to the regenerator 3 is supplied from the upper part of the regenerator 3 to the inside of the regenerator 3. The rich solution releases CO2 by an endothermic reaction inside the regenerator 3. For example, the regenerator 3 includes a first regenerator 31 on the upper side and a second regenerator 32 on the lower side, and the rich solution is first supplied to the first regenerator 31 and releases CO2 in the first regenerator 31. The rich solution is supplied from the first regenerator 31 to the second regenerator 32 through a pipe 33 connecting the lower part of the first regenerator 31 and the upper part of the second regenerator 32, and further releases CO2 in the second regenerator 32. A heat exchanger 34 is provided in the pipe 33, and the heated fluid and the absorbing solution flowing through the pipe 33 exchange heat in the heat exchanger 34. As a result, the absorbing solution flowing through the pipe 33 is heated. The heated fluid passing through the heat exchanger 34 can be the lean absorbing solution, steam condensate, exhaust gas, CO2, etc. in the CO2 recovery device 100. When the absorbing liquid passes through the heat exchanger 34, the temperature rises and part of the CO2 becomes gaseous. Therefore, the density of the heated absorbing liquid becomes smaller than the state before passing through the heat exchanger 34 (state before heating), and when it leaves the heat exchanger 34, it rises to a position higher than the heat exchanger 34. The absorbing liquid is then supplied to the upper part of the second regenerating section 32 along the pipeline of the pipe 33. The pipe 33 in FIG. 1 is an example of a thermosiphon section. The rich solution supplied to the second regenerating section through the pipe 33 (thermosiphon section) becomes a lean solution, which is an absorbing liquid from which almost all of the CO2 has been removed, by the time it reaches the lower part of the regenerating tower 3 (the lower part of the second regenerating section 32). The lean solution is pressurized by the pump 35 and sent to the heat exchanger 4 through the pipe 51. The lean solution sent to the heat exchanger 4 through the pipe 51 is cooled by the rich solution in the heat exchanger 4 and is supplied to the absorption tower 2 through the pipe 52. In this way, the absorbing liquid circulates between the absorption tower 2 and the regenerating tower 3. From the top of the regenerator 3, CO2 gas 81 accompanied with water vapor released from the rich solution in the regenerator 3 is discharged.

[0013] A rich solution control valve 61 is provided in the pipe 54. The control device 1 controls the opening of the rich solution control valve 61 to control the amount of rich solution sent to the regenerator 3 per unit time. A lean solution control valve 62 is provided in the pipe 52. The control device 1 controls the opening of the lean solution control valve 62 to control the amount of lean solution sent to the absorption tower 2 per unit time. The liquid level position of the lean solution accumulating at the bottom of the regenerator 3 (referred to as the bottom liquid level height of the regenerator 3) is determined by the balance between the flow rate of the absorption solution supplied from the pipe 33 to the second regenerator and the flow rate of the lean solution draining from the bottom of the regenerator 3. The flow rate supplied from the pipe 33 to the second regenerator is affected by the flow rate of the rich solution flowing into the regenerator 3. For example, when the flow rate of the rich solution flowing into the regeneration tower 3 increases, the flow rate of the absorption solution supplied to the second regeneration section through piping 33 increases, and if the flow rate of the lean solution flowing out from the bottom of the tower does not change, the liquid level at the bottom of the regeneration tower 3 increases.

[0014] A pump 21 for sending out the rich solution is provided on the piping 53. The control device 1 controls the pump 21 to pump the rich solution accumulated at the bottom of the absorption tower 2 to the heat exchanger 4 and the regeneration tower 3. A pump 35 for sending out the lean solution is provided on the piping 51. The control device 1 controls the pump 35 to pump the lean solution accumulated at the bottom of the regeneration tower 3 to the heat exchanger 4 and the absorption tower 2. The control device 1 also acquires information such as the flow rate per unit time of the lean solution measured by the flowmeter 71, the flow rate per unit time of the rich solution measured by the flowmeter 72, the load (output) of industrial combustion equipment such as a boiler or a gas turbine, and the liquid level at the bottom of the regeneration tower 3, and controls the pump 21, the pump 35, the opening of the rich solution control valve 61, the lean solution control valve 62, and the like, so that the liquid level at the bottom of the regeneration tower 3 is within a predetermined range based on this information. Information on the liquid level at the bottom of the regeneration tower 3 may be predicted by a mathematical model together with information on the liquid level at the inlet piping of the piping 33 (thermosiphon section) (sometimes referred to as the liquid level at the inlet side) (second embodiment), or a liquid level meter 73 may be provided to measure the liquid level at the bottom of the tower, and the measurement value measured by the liquid level meter 73 may be obtained (third embodiment).

[0015] An example of a general thermosiphon unit is shown in FIG. 2. Pipe 33 (thermosiphon unit) shown in FIG. 2 includes horizontal pipe 331, vertical pipe 332, horizontal pipe 333, vertical pipe 334, horizontal pipe 335, vertical pipe 336, and horizontal pipe 337. Here, the liquid level on the inlet side of the absorbing liquid flowing through pipe 33 (liquid level of the absorbing liquid in pipe 332 arranged in the liquid phase part upstream of heat exchanger 34 among the pipes constituting the thermosiphon unit) varies depending on the operating load of CO2 recovery device 100. The range of this variation is defined as liquid level variation range 200 shown in FIG. 2. In the configuration example of FIG. 2, horizontal pipe 333 is included in liquid level variation range 200. Then, when the liquid level fluctuates across the horizontal pipe 333, that is, during the time period when the liquid level changes between H1, which is slightly higher than the horizontal pipe 333, and H2, which is slightly lower than the horizontal pipe 333, only the amount of absorbent held in the horizontal pipe 333 changes, and the liquid level on the inlet side of the pipe 33 does not change. As a result, the head difference between the inlet side and the outlet side does not change, and the change in the circulation flow rate of the absorbent circulating through the pipe 33 temporarily stops, resulting in wasted time in control. More specifically, for example, when the operating load of the CO2 recovery apparatus is in a load range where the liquid level is between H1 and H2, even if the opening degree of the rich solution control valve 61 etc. is changed in an attempt to control the bottom liquid level of the regenerator 3 within an appropriate range, only the amount of absorption liquid held by the horizontal pipe 333 changes, and the head on the inlet side of the piping 33 does not change. Until the head changes (until the liquid level becomes higher than H1 or lower than H2), the change in the opening degree of the rich solution control valve 61 etc. does not affect the change in the circulation flow rate of the absorption liquid circulating through the piping 33, and the adjustment of the bottom liquid level of the regenerator 3 by controlling the opening degree of the rich solution control valve 61 etc. may not be as expected.

[0016] Therefore, in this embodiment, (1) in the range of normal operating load of the CO2 recovery device, the head (liquid level) of the inlet pipe of the pipe 33 (thermosiphon unit) is calculated in advance from the balance of the absorption liquid flow rate, temperature, and pressure, and a configuration is adopted in which there is no horizontal pipe in the fluctuation range (a vertical pipe is preferable, but an inclined pipe arranged in a direction inclined with respect to the vertical direction may be used). An example of such a configuration is shown in Figs. 3A and 3B. The configuration example of Fig. 3A is a configuration based on the configuration shown in Fig. 2, in which the vertical pipe 332a is extended downward, the vertical pipe 334a is shortened by that amount, and the horizontal pipe 333a is provided outside (below) the fluctuation range 200 of the liquid level, so that the horizontal part is not included in the fluctuation range 200 of the liquid level. The configuration shown in Fig. 3B is a configuration based on the configuration shown in Fig. 2, in which the horizontal pipe 333 in Fig. 3 is changed to an inclined pipe 333b, and the length of the vertical pipe 334 is adjusted to form a vertical pipe 334b. The configuration in Figure 3A is more preferable, but by using a configuration such as that in Figures 3A and 3B, it is possible to avoid a situation in which the head on the inlet side of pipe 33 does not change and the liquid circulation flow rate stops changing when the liquid level fluctuates to cross the horizontal pipe 333.

[0017] Alternatively, (2) even if the horizontal pipe is installed within the range of fluctuation of the liquid level, by reducing its volume, it is possible to reduce the effect of the head of the inlet side of the pipe 33 not changing when the liquid level fluctuates so as to cross the horizontal pipe 333, and the change in the circulation flow rate of the absorbing liquid stopping. For example, when the cross-sectional area of ​​the bottom of the regenerator 3 is A and the fluctuation range (control target range) of the liquid level at the bottom of the regenerator 3 under normal load is ΔL, the horizontal pipe (for example, the horizontal pipe 333 in FIG. 2) is installed so that the volume of the horizontal pipe installed so as to be included in the liquid level fluctuation range 200 is smaller than A×ΔL. If the flow is ideally performed without delay in the pipes other than the horizontal pipe, the time during which the head does not change and the absorbing liquid is held in the horizontal pipe portion becomes dead time, and the volume of the horizontal pipe portion appears as a fluctuation in the liquid level at the bottom of the regenerator 3. Therefore, by making the volume of the horizontal pipe portion smaller than A×ΔL, the effect of the amount of absorbent held in the horizontal pipe on the liquid level at the bottom of the regenerator 3 can be kept within the control target range.

[0018] Next, a method of calculating the fluctuation range 200 of the liquid level height will be described with reference to FIG. 4. In the piping 33 (thermosiphon section) illustrated in FIG. 4, WL1 is the flow rate of the absorbing liquid flowing into the heat exchanger 34, WL2 is the flow rate of the absorbing liquid flowing out of the heat exchanger 34, WL3 is the flow rate of the absorbing liquid flowing through the riser pipe (piping 336 in the case of the configuration of FIG. 3), and WG3 is the flow rate of gas such as CO2 flowing through the riser pipe. In this case, the mass conservation equation (1) in FIG. 4 holds. In addition, if Q is the amount of heat given to the absorbing liquid from the heated fluid in the heat exchanger 34, CP is the specific heat of the absorbing liquid, WL is the above WL1 or WL2, T2 is the temperature of the absorbing liquid at the outlet of the heat exchanger 34, and T1 is the temperature of the absorbing liquid at the inlet of the heat exchanger 34, then the energy conservation equation (2) in FIG. 4 holds. In addition, WL is the above WL3, T2, and T3 are the temperature of the absorbing liquid at the outlet of the heat exchanger 34, the temperature of the absorbing liquid in the riser pipe, and Y CO2H2OIf P1 is the latent heat of vaporization of the gas flowing through the riser pipe, the energy conservation equation (3) in Fig. 4 is established. If P1 is the pressure of the absorbing liquid at the inlet of the heat exchanger 34, ρ1 is the density of the absorbing liquid at the inlet of the heat exchanger 34, g is the gravitational constant, L1 is the liquid level, ρ2 is the density of the absorbing liquid in the single-layer section (part containing only the absorbing liquid) after the outlet of the heat exchanger 34, LS is the liquid level in the single-layer section in the riser pipe based on the outlet of the heat exchanger 34, ρ3 is the density of the two-phase section of the absorbing liquid and gas up to the top of the riser pipe based on the end point of the single-layer section in the riser pipe, and LT is the height to the top of the riser pipe based on the end point of the single-layer section in the riser pipe, the momentum conservation equation (4) in Fig. 4 is established. By inputting various parameters into these static balance calculation equations (1) to (4), the liquid level L1 can be calculated. Therefore, the liquid level fluctuation range 200 can be calculated by inputting the values ​​of various parameters at the minimum and maximum operating loads of the CO2 recovery device 100 into formulas (1) to (4) and calculating the liquid level at the minimum and maximum operating loads. When the CO2 recovery device 100 is designed, the liquid level fluctuation range 200 is calculated, and the piping 33 is configured so that a horizontal pipe is not provided in this range, thereby making it possible to avoid a temporary stop in the change in the circulation flow rate of the absorbing liquid caused by the horizontal pipe. Alternatively, the effect of a temporary stop in the change in the circulation flow rate of the absorbing liquid can be reduced by making the volume of the horizontal pipe provided in the liquid level fluctuation range 200 smaller than A×ΔL. Note that the calculation method of the liquid level fluctuation range 200 described here is an example. For example, the liquid level fluctuation range 200 may be estimated with reference to experiments or past performance data.

[0019] (effect) As described above, according to the first embodiment, changes in the circulation flow rate of the absorption liquid in the thermosiphon section due to fluctuations in the liquid level in the thermosiphon section are temporarily stopped, thereby avoiding or reducing the occurrence of wasted time in control and stabilizing the control of the CO2 recovery apparatus.

[0020] The control of the second to fourth embodiments will be described below on the premise of the configuration of the first embodiment. By adopting the configuration of the first embodiment for the thermosiphon section of the regenerator 3, for example, it is possible to eliminate the instability in control caused by the fluctuation of the liquid level of the thermosiphon section under the normal operating load of the CO2 capture device, but when the operating load becomes a non-steady load, a similar problem may occur. In order to reduce the influence of the temporary stop of the change in the circulation flow rate of the absorption liquid caused by the liquid level of the thermosiphon section under the non-steady operating load, it is effective to combine the control of the second to fourth embodiments described below. Note that the control of the second to fourth embodiments is also effective when the configuration of the first embodiment is not adopted for the thermosiphon section of the regenerator 3.

[0021] Second Embodiment In the second embodiment, control is performed to keep the fluctuation of the liquid level at the bottom of the regenerator 3 within a target management range. The control device 1 expresses the relationship between the inflow rate of the absorbing liquid flowing into the regenerator 3, the outflow rate of the absorbing liquid flowing out of the regenerator 3, the liquid level at the bottom of the regenerator 3, the inflow rate of the absorbing liquid into the thermosiphon section, the outflow rate of the absorbing liquid from the thermosiphon section, and the liquid level of the absorbing liquid in the inlet pipe of the thermosiphon section as a mathematical model, and simulates the liquid level fluctuation (head difference) on the inlet side of the thermosiphon section and the liquid level fluctuation at the bottom of the regenerator 3. An example of the mathematical model expressing these relationships is shown in FIG. level1 is the liquid level in the thermosiphon, x level2 is the liquid level at the bottom of the regeneration tower 3, x head is the head of the outlet pipe of the thermosiphon section (pipes 336 and 337 in Figure 2), ρ is the density of the absorption liquid, and x rich is the inflow flow rate of the absorbing liquid flowing into the regenerator 3, and x lean is the outflow rate of the absorbing liquid flowing out from the regeneration tower 3, and x f1 is the outflow rate of the absorbing liquid from the thermosiphon section to the second regeneration section 32, u rich the opening degree of the rich solution control valve 61, u lean is the opening degree of the lean solution control valve 62, CV rich is a proportional constant showing the relationship between the valve opening degree and the flow rate of the rich solution control valve 61, CV leanLet a be a proportional constant showing the relationship between the valve opening degree of the lean solution control valve 62 and the flow rate, a1 be the ratio of the absorbing liquid that reaches the bottom of the first regenerator 31 without vaporizing after flowing into the regenerator 3, a2 be the ratio of the absorbing liquid that reaches the bottom of the second regenerator 32 without vaporizing after flowing into the second regenerator 32, g be the gravity constant, A1 be the cross-sectional area of ​​the thermosiphon section, A2 be the cross-sectional area of ​​the regenerator 3, and J1 be a predetermined constant according to the head difference between the inlet side and the outlet side of the thermosiphon section, and then the formulas (5) to (9) in FIG. 5 are established. The formulas (5) to (9) are the above-mentioned mathematical models. The formula (5) is a state space model that represents the fluctuation of the liquid level at the inlet side of the thermosiphon section per unit time, and the formula (6) is a state space model that represents the fluctuation of the liquid level at the bottom of the regenerator 3 per unit time. The liquid level at the bottom of the regenerator 3 is likely to deviate from the target management range when the operating load of the CO2 recovery device 100 is not steady. For example, the control device 1 uses this mathematical model to determine the opening degree u of the rich solution control valve 61 so that the liquid level at the bottom of the regenerator 3 is constant. rich and the opening degree u of the lean solution control valve 62 lean The valves are controlled at the opening degree found by searching for the valve position. At this time, the liquid level at the bottom of the regenerator 3 is equal to the inflow flow rate x rich and the outflow rate from regeneration tower 3 x lean However, in the case of a regenerator 3 having a thermosiphon section, the circulation flow rate of the absorbing liquid in the thermosiphon section affects the liquid level at the bottom of the regenerator 3. For example, a temporary halt in the change in the circulation amount of the absorbing liquid in the thermosiphon section has a large effect on the liquid level at the bottom of the regenerator 3. Therefore, for example, the liquid level and circulation flow rate in the thermosiphon section are predicted using equations (5) to (9), and the predicted result is used to predict the liquid level at the bottom of the regenerator 3. For example, the control device 1 adjusts the opening degree u of the rich solution control valve 61 using a control method that optimizes the liquid level fluctuation in the thermosiphon section so that the liquid level at the bottom of the regenerator 3 is constant. rich and the opening degree u of the lean solution control valve 62 lean The optimizing control method may be, for example, but is not limited to, model predictive control or linear quadratic Gaussian.

[0022] (operation) An example of control according to the second embodiment is shown in Fig. 6. The flowchart in Fig. 6 shows the flow of control when the operating load of the CO2 recovery apparatus 100 becomes a non-steady state value. First, the operating load of the plant (CO2 capture device) changes (step S1). As the operating load changes, the set values ​​of the inflow flow rate and outflow flow rate of the absorbing solution to the regenerator 3 change (step S2). The control device 1 calculates the inflow flow rate of the absorbing solution to the regenerator 3 and the outflow flow rate of the absorbing solution from the regenerator 3 according to the changed load. Next, the control device 1 calculates a control input according to the change in the operating load (step S3). For example, the control device 1 calculates the opening degree u of the rich solution control valve 61 according to the changed operating load. rich and the opening degree u of the lean solution control valve 62 lean The control device 1 also calculates the rotation speeds of the pumps 21 and 35 according to the changed operating load. Next, the valve openings of the inflow and outflow flow rate control valves of the regenerator 3 are changed (step S4). For example, the control device 1 calculates the opening u of the rich solution control valve 61 calculated in step S3. rich and the opening degree u of the lean solution control valve 62 lean The control device 1 adjusts the opening of each valve 61, 62 so that the opening becomes equal to the rotation speed calculated in step S3. The control device 1 also operates the pumps 21, 35 at the rotation speed calculated in step S3. This changes the inflow and outflow flow rates of the regenerator 3 (step S5). The control up to this point is similar to the control in a general CO2 capture device. In addition to the processing in steps S1 to S5, in this embodiment, an optimization calculation is performed using the above-mentioned mathematical model. Specifically, the control device 1 predicts the momentary fluctuation in the liquid level in the inlet piping of the thermosiphon section using equations (5), (7), and (8) (step S6). For example, the control device 1 uses the opening u of the rich solution control valve 61 calculated in step S3 to rich And from equation (8), x rich Calculate the result and substitute equation (7) into equation (5) to get x head1 Set a given value to x level1 Next, the control device 1 uses the formulas (6), (7), and (9) to predict the fluctuation in the bottom liquid level of the regenerator 3 from moment to moment (step S7). For example, the control device 1 predicts the fluctuation in the bottom liquid level of the regenerator 3 from moment to moment based on the opening degree u lean And from equation (9), xlean Calculate the result and substitute equation (7) into equation (6) to get x head1 Set a given value to x level2 Next, the control device 1 calculates the control input values ​​(valve openings of the rich solution control valve 61 and the lean solution control valve 62) (step S8). The control device 1 calculates the valve openings of the rich solution control valve 61 and the lean solution control valve 62 such that the bottom liquid level of the regenerator 3 falls within the target control range, using optimal control such as model predictive control or linear quadratic Gaussian. For example, the control device 1 uses the mathematical models of Equations (5) to (9) to repeatedly predict the liquid level fluctuations in the thermosiphon section when the openings of the valves 61 and 62 are changed, and the liquid level fluctuations at the bottom of the regenerator 3, and calculates the liquid level fluctuations dx level2 The opening degree u of the rich solution control valve 61 that realizes the liquid level at the inlet side of the thermosiphon section such that / dt is 0 rich and the opening degree u of the lean solution control valve 62 at that time. lean Next, the control device 1 searches for the opening degree u of the rich solution control valve 61 calculated in step S8. rich and the opening degree u of the lean solution control valve 62 lean The opening of each valve 61, 62 is adjusted so that the liquid level at the inlet piping of the thermosiphon section is equal to or lower than the opening of the regenerator inlet flow control valve (step S4). For example, when the liquid level at the inlet piping of the thermosiphon section is excessively high, the opening of the regenerator inlet flow control valve is decreased, and when the liquid level is excessively low, the opening of the valve is increased. This allows the liquid level at the bottom of the regenerator 3 to be controlled within the target control range.

[0023] (effect) As described above, according to the second embodiment, even without measuring the liquid level in the thermosiphon section, the liquid level change when the operating load changes is predicted, and the fluctuation in the liquid level at the bottom of the regenerator 3 resulting from the liquid level change in the thermosiphon section is predicted. Then, the opening degree u of the rich solution control valve 61 is set so that the liquid level at the bottom of the regenerator 3 is kept constant. rich and the opening degree u of the lean solution control valve 62 leanThe liquid level at the bottom of the regenerator 3 can be stabilized by calculating the above and controlling each valve. A method of measuring the liquid level at the bottom of the regenerator and controlling the inflow and outflow rates of the regenerator 3 using the measurement results has been used in the past for a general regenerator, but in the case of a regenerator 3 equipped with a thermosiphon unit, it is desirable to take into account the circulation flow rate of the thermosiphon unit. According to this embodiment, the liquid level at the bottom of the regenerator 3 reflecting the prediction of the circulation flow rate of the thermosiphon unit is predicted, and the inflow and outflow rates of the absorbing liquid to the regenerator 3 can be controlled based on the prediction. The second embodiment can also be applied to a CO2 recovery device in which the thermosiphon unit does not have the piping structure described in the first embodiment.

[0024] <Third embodiment> In the third embodiment, the liquid level at the bottom of the regeneration tower 3 is measured by the liquid level gauge 73, and the opening degree u of the rich solution control valve 61 is adjusted based on the measurement result. rich and the opening degree u of the lean solution control valve 62 lean By adjusting the above, the liquid level at the bottom of the regenerator 3 is stabilized. Specifically, the liquid level at the bottom of the regenerator 3 is monitored, and when the operating load of the CO2 recovery device 100 becomes an unsteady value, if the liquid level at the bottom of the regenerator 3 exceeds an upper threshold value or falls below a lower threshold value, it is determined that the change in the circulation amount of the absorption liquid in the thermosiphon section has temporarily stopped, and the set values ​​of the inflow flow rate and outflow flow rate of the regenerator 3 are increased or decreased to temporarily increase or decrease the inflow flow rate or outflow flow rate by a certain amount. For example, if the liquid level at the bottom of the regenerator 3 increases or decreases by 5% from the steady state, the inflow flow rate set value of the regenerator 3 is controlled to increase or decrease.

[0025] An example of control according to the third embodiment is shown in Fig. 7. The flowchart in Fig. 7 shows the flow of control when the operating load of the CO2 recovery apparatus 100 becomes a non-steady state value. First, the operating load of the plant (CO2 capture device) changes (step S11). As the operating load changes, the set values ​​of the inflow flow rate and outflow flow rate of the absorbing solution to the regenerator 3 change (step S12). The control device 1 calculates the set value of the inflow flow rate of the absorbing solution to the regenerator 3 and the set value of the outflow flow rate of the absorbing solution from the regenerator 3 according to the changed operating load. For example, the control device 1 has a table or the like in which the operating load and the set values ​​of the inflow flow rate and outflow flow rate are associated with each other, and calculates the set values ​​of the inflow flow rate and the outflow flow rate based on this table. Next, the control device 1 calculates the control input associated with the change in the operating load (step S13). For example, the control device 1 calculates the opening degree u of the rich solution control valve 61 according to the changed operating load based on the set value of the inflow flow rate calculated in step S12. rich Based on the set value of the outflow rate calculated in step S12, the opening degree u of the lean solution control valve 62 according to the changed operating load is calculated. lean The control device 1 also calculates the rotation speeds of the pumps 21 and 35 according to the changed operating load. Next, the valve openings of the inflow and outflow flow rate control valves of the regenerator 3 are changed (step S14). For example, the control device 1 calculates the opening u of the rich solution control valve 61 calculated in step S14. rich and the opening degree u of the lean solution control valve 62 lean The opening degree of each valve 61, 62 is adjusted so that the flow rate is equal to or less than the upper limit of the threshold value and the lower limit of the threshold value. In addition, the control device 1 operates the pumps 21, 35 at the rotation speed calculated in step S14. This causes the inflow and outflow flow rates of the regenerator 3 to change (step S15). In addition, the liquid level of the inlet pipe of the thermosiphon section changes (step S16). The liquid level gauge 73 measures the liquid level at the bottom of the regenerator 3 (step S17) and sends the measured value to the control device 1. The control up to this point is similar to the control in a general CO2 recovery device. In addition to the processing of steps S11 to S17, in this embodiment, a flow rate setting value increase / decrease process is performed based on the measured value measured by the liquid level gauge 73. For example, the control device 1 acquires the measured value measured by the liquid level gauge 73 and compares the liquid level at the bottom indicated by the measured value with the upper threshold value and the lower threshold value. If the measured value of the liquid level at the bottom is within a range below the upper threshold value and above the lower threshold value (step S18; No), the process from step S13 is repeated.

[0026] When the liquid level at the bottom of the tower is greater than the upper threshold or less than the lower threshold (step S18; Yes), the control device 1 increases or decreases the set value of the inflow flow rate and the set value of the outflow flow rate of the absorbing liquid into the regenerator 3 by a predetermined amount (step S19). For example, the control device 1 has a control table in which the set value of the inflow flow rate and the set value of the outflow flow rate of the absorbing liquid into the regenerator 3 are set in correspondence with the extent to which the liquid level at the bottom of the regenerator 3 is greater than the upper threshold or less than the lower threshold, and the control device 1 may increase or decrease the set value of the inflow flow rate and the set value of the outflow flow rate by referring to this control table. The set values ​​may be increased or decreased for only one of the inflow flow rate or the outflow flow rate, or for both the inflow flow rate and the outflow flow rate. For example, when the liquid level at the bottom of the tower is greater than the upper threshold, the circulating flow rate of the absorbing liquid in the thermosiphon section is considered to be high, so the control device 1 decreases the set value of the inflow flow rate or increases the set value of the outflow flow rate (or performs both). On the other hand, when the liquid level at the bottom of the regenerator 3 is less than the lower limit of the threshold, the controller 1 increases the set value of the inflow flow rate, decreases the set value of the outflow flow rate, or performs both. When the set values ​​of the inflow flow rate and / or the outflow flow rate of the regenerator 3 are increased or decreased, the controller 1 repeats the process from step S13. As a result, the liquid level at the bottom of the regenerator 3 is controlled, for example, within the target control range.

[0027] (effect) As described above, according to the third embodiment, the liquid level at the bottom of the regeneration tower 3 is monitored, and the opening degree u of the rich solution control valve 61 is controlled so that the liquid level at the bottom of the regeneration tower 3 does not deviate from the target control range. rich and the opening degree u of the lean solution control valve 62 lean By controlling the above, the liquid level at the bottom of the regenerator 3 can be stabilized. For example, since the regenerator 3 is often originally provided with a liquid level gauge 73, according to the third embodiment, even in the case of a regenerator 3 equipped with a thermosiphon unit, the liquid level at the bottom of the regenerator 3 can be stabilized without adding any equipment. The third embodiment may be used in combination with the second embodiment. The third embodiment can also be applied to a CO2 capture device in which the thermosiphon unit does not have the piping structure described in the first embodiment.

[0028] <Fourth embodiment> In the fourth embodiment, control is performed to avoid a situation in which the bottom liquid level of the regenerator 3 deviates from the target management range. Specifically, at the plant operating load where the installation height of the horizontal pipe of the thermosiphon section (horizontal pipe 333 in FIG. 2) is approximately equal to the head (liquid level on the inlet side) required for the establishment of the thermosiphon, the inflow flow rate and outflow flow rate of the regenerator 3 are increased or decreased by a certain amount. For example, while the CO2 recovery device 100 is operating at an operating load where the liquid level on the horizontal pipe of the thermosiphon section and the inlet side are approximately equal, the set values ​​of the inflow flow rate and the outflow flow rate are kept constant without being changed according to the operating load, and when such an operating load is removed, the flow rate set value is discontinuously changed to avoid an unstable state.

[0029] FIG. 8 shows an example of setting the flow rate set value according to the operating load of the plant. The vertical axis of the graph in FIG. 8 shows the set value of the inflow flow rate or outflow flow rate, the horizontal axis shows the operating load of the plant (CO2 recovery device 100), and the line R1 shows the flow rate set value according to the operating load. As shown in the figure, the operating load and the flow rate set value are proportional to each other when the operating load is outside the range of L1 to L2. If the CO2 recovery device 100 is operated at a flow rate set value based on the same proportional relationship as outside the range of L1 to L2, the operating load range of L1 to L2 is a load band in which the liquid level on the inlet side of the thermosiphon unit is at the same level as the horizontal pipe. In the fourth embodiment, when the operating load of the plant is in the range of L1 to L2, the set value of the inflow flow rate and / or the outflow flow rate is discontinuously changed to move the liquid level on the inlet side of the thermosiphon unit away from the height of the horizontal pipe. For example, when the operating load reaches L1 from a state smaller than L1, the control device 1 maintains the flow rate set value at C1 based on the graph in FIG. 8. Then, when the operating load of the plant reaches L2, the control device 1 discontinuously changes the flow rate set value from C1 to C2. Also, for example, when the operating load reaches L2 from a state greater than L2, the control device 1 maintains the flow rate set value at C2. Then, when the operating load of the plant reaches L1, the control device 1 discontinuously changes the flow rate set value from C2 to C1. The range of operating loads L1-L2 within which the flow rate set value is maintained is determined by prior calculation or trial operation. In this way, by changing the set value of the inflow flow rate or outflow flow rate so as to prevent the liquid level on the inlet side of the thermosiphon section from becoming the same level as the horizontal section, a situation in which the liquid level at the bottom of the regenerator 3 becomes unstable is avoided.

[0030] An example of control according to the fourth embodiment is shown in Fig. 9. The flowchart in Fig. 9 shows the flow of control when the operating load of the CO2 recovery apparatus 100 becomes an unsteady value. First, the operating load of the plant (CO2 recovery device) changes (step S21). With the change in the operating load, the set values ​​of the inflow flow rate and outflow flow rate of the absorbing liquid in the regenerator 3 change (step S22). The control device 1 calculates the inflow flow rate of the absorbing liquid to the regenerator 3 and the outflow flow rate of the absorbing liquid from the regenerator 3 according to the changed operating load. Here, in this embodiment, a correction process of the flow rate set value is performed. First, the control device 1 judges whether the changed operating load is an operating load of the plant such that the liquid level height of the inlet pipe of the thermosiphon unit and the height of the horizontal part of the thermosiphon unit are almost equal (step S23). For example, the control device 1 has information exemplified in FIG. 8, and makes this judgment by comparing L1 and L2 of this information with the changed operating load. If the operating load of the plant is not such that the liquid level height of the inlet pipe of the thermosiphon unit and the height of the horizontal part of the thermosiphon unit are almost equal (step S23; No, if not in the range of L1 to L2 in FIG. 8), proceed to step S25. If the changed operating load is included in the operating load as in the above condition (step S23; Yes, in the range of L1 to L2 in FIG. 8), the control device 1 corrects the set values ​​of the inflow flow rate and the outflow flow rate of the regenerator 3 (step S24). For example, in the example of FIG. 8, when the operating load is increased, the control device 1 maintains the flow rate set value at L1, and when the operating load is decreased, the control device 1 maintains the flow rate set value at L2. Next, the control device 1 calculates a control input accompanying the change in the operating load (step S25). For example, the control device 1 calculates the opening degree u of the rich solution control valve 61 according to the changed operating load based on the set values ​​of the inflow flow rate and the outflow flow rate calculated in step S22. rich and the opening degree u of the lean solution control valve 62 lean In step S24, when the set value is corrected, the control device 1 calculates the opening degree u corresponding to the corrected set value. rich and opening u lean The control device 1 also calculates the rotation speeds of the pumps 21 and 35 according to the changed operating load. Next, the valve openings of the inflow and outflow flow rate control valves of the regenerator 3 are changed (step S26). For example, the control device 1 calculates the opening u of the rich solution control valve 61 calculated in step S25. rich and the opening degree u of the lean solution control valve 62 leanThe control device 1 adjusts the opening of each valve 61, 62 so that the above-mentioned rotation speed is satisfied. The control device 1 also operates the pumps 21, 35 at the rotation speed calculated in step S25. This causes the inflow and outflow flow rates of the regenerator 3 to change (step S27). The liquid level of the inlet pipe of the thermosiphon section also changes (step S28). The liquid level gauge 73 also measures the liquid level at the bottom of the regenerator 3 (step S29) and sends the measured value to the control device 1. The control device 1 then repeats the process from step S25. For example, the control device 1 calculates the opening of the rich solution control valve 61 and the opening of the lean solution control valve 62 to bring the liquid level at the bottom of the regenerator 3 closer to the target value according to the difference between the measured value and the target value of the liquid level at the bottom of the regenerator 3, and controls the valves 61, 62 based on the calculation result. This causes the liquid level at the bottom of the regenerator 3 to be controlled, for example, within a management target range.

[0031] (effect) According to the fourth embodiment, the presence or absence of the liquid hold amount in the horizontal pipe of the thermosiphon section is continuously switched (there is no time period in which the liquid level on the inlet side of the thermosiphon section is the same height as that of the horizontal pipe, and it continuously switches from H1 to H2 or from H2 to H1 in FIG. 2), so it is possible to prevent the liquid level at the bottom of the regenerator 3 from becoming unstable. The fourth embodiment may be combined with the second and third embodiments. The fourth embodiment can also be applied to a CO2 recovery device in which the thermosiphon section does not have the piping structure described in the first embodiment.

[0032] FIG. 10 is a diagram showing an example of a hardware configuration of a controller according to each embodiment. A computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input / output interface 904, and a communication interface 905. The above-mentioned control device 1 is implemented in the computer 900. The above-mentioned functions are stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from the auxiliary storage device 903, loads it in the main storage device 902, and executes the above-mentioned processing according to the program. The CPU 901 also secures a storage area in the main storage device 902 according to the program. The CPU 901 also secures a storage area in the auxiliary storage device 903 for storing data being processed according to the program.

[0033] A program for realizing all or part of the functions of the control device 1 may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. In addition, if a WWW system is used, the term "computer system" also includes a homepage providing environment (or display environment). In addition, the term "computer-readable recording medium" refers to a portable medium such as a CD, DVD, or USB, or a storage device such as a hard disk built into a computer system. In addition, if the program is distributed to the computer 900 via a communication line, the computer 900 that receives the program may deploy the program in the main storage device 902 and execute the above processing. In addition, the above program may be for realizing part of the above-mentioned functions, or may be capable of realizing the above-mentioned functions in combination with a program already recorded in the computer system.

[0034] In another embodiment, the control device 1 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0035] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and gist of the invention.

[0036] <Additional Notes> The regenerator, the control device, and the control method described in each embodiment can be understood, for example, as follows.

[0037] (1) A regeneration tower according to a first aspect is a regeneration tower of a CO2 recovery equipment, and includes a first regeneration section for storing an absorbing liquid supplied from an absorption tower of the CO2 recovery equipment to the regeneration tower, a second regeneration section provided below the first regeneration section, and a thermosiphon section which is a pipe connected from the lower part of the first regeneration section to the upper part of the second regeneration section via a heat exchanger, wherein the absorbing liquid is supplied to the second regeneration section from the first regeneration section through the thermosiphon section, and the volume of a horizontally arranged pipe provided within a range where the liquid level of the absorbing liquid fluctuates in a pipe arranged in the liquid phase portion upstream of the heat exchanger among the pipes constituting the thermosiphon section is smaller than the volume allowed to fluctuate for the absorbing liquid stored in the second regeneration section. This makes it possible to suppress fluctuations in the liquid level in the regeneration tower equipped with a thermosiphon section, thereby stabilizing the control of the CO2 capture device.

[0038] (2) A regenerator according to a second aspect is the regenerator of (1), in which the horizontally disposed pipe is not provided in a range where the liquid level of the absorbing liquid fluctuates. This temporarily stops the change in the circulating flow rate of the absorbing liquid in the thermosiphon section, eliminating any dead time in control and stabilizing the control of the CO2 capture device.

[0039] (3) A regeneration tower according to a third aspect is a regeneration tower according to (2), in which piping constituting the thermosiphon section is arranged in a vertical direction or in a direction inclined with respect to the vertical direction within a range in which the liquid level height of the absorption liquid fluctuates. This temporarily stops the change in the circulating flow rate of the absorbing liquid in the thermosiphon section, eliminating any dead time in control and stabilizing the control of the CO2 capture device.

[0040] (4) A control device according to a fourth aspect is a control device for a CO2 recovery device including the regeneration tower and an absorption tower according to (1) to (2), and calculates valve openings of the first flow rate control valve and the second flow rate control valve that optimize the liquid level of the thermosiphon section so that the liquid level of the tower bottom is constant, based on a first model that represents a relationship between a fluctuation in the liquid level of the thermosiphon section, a first flow rate based on a valve opening of a first flow rate control valve that adjusts a first flow rate, which is the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower, and a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a second model that represents a relationship between a fluctuation in a tower bottom liquid level, which is the liquid level of the absorbing liquid stored in the second regeneration section, a second flow rate based on a valve opening of a second flow rate control valve that adjusts a second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate. This makes it possible to stabilize the liquid level at the bottom of the regeneration tower.

[0041] (5) A control device according to a fifth aspect is a control device for a CO2 recovery device including the regeneration tower of (1) to (2) and an absorption tower, and when the measured value of the liquid level height in the second regeneration section exceeds a predetermined threshold, the valve opening of the first flow control valve is decreased by a first predetermined amount and / or the valve opening of the second flow control valve is increased by a second predetermined amount, and when the measured value of the liquid level height in the second regeneration section falls below a predetermined threshold, the valve opening of the first flow control valve is increased by a third predetermined amount and / or the valve opening of the second flow control valve is decreased by a fourth predetermined amount. This makes it possible to stabilize the liquid level at the bottom of the regeneration tower.

[0042] (6) A control device according to a sixth aspect is a control device for a CO2 recovery apparatus including the regeneration tower and an absorption tower according to (1) to (2), and when the operating load of the CO2 recovery apparatus falls within a predetermined range in which it is assumed that the liquid level of the absorption liquid in the piping arranged in the liquid phase portion upstream of the heat exchanger and the height of the position of the piping constituting the thermosiphon section arranged in the horizontal direction are the same height, the control device does not change the valve opening degree of the first flow control valve and the second flow control valve. This makes it possible to stabilize the liquid level at the bottom of the regeneration tower.

[0043] (7) A control method according to a seventh aspect is a control method for a CO2 recovery apparatus including a first regeneration unit that stores an absorbing liquid supplied from an absorption tower of a CO2 recovery apparatus to the regeneration tower, a second regeneration unit provided below the first regeneration unit, and a thermosiphon unit that is a pipe connected from a lower part of the first regeneration unit to an upper part of the second regeneration unit via a heat exchanger, the second regeneration unit including a regeneration tower to which the absorbing liquid is supplied from the first regeneration unit through the thermosiphon unit, and an absorption tower, the control method including the step of: controlling a first flow rate, which is a flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower, based on a fluctuation in the liquid level in the thermosiphon unit and a valve opening degree of a first flow rate control valve. and a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a second model that represents the relationship between the second flow rate based on a valve opening of a second flow control valve that adjusts a second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate, the valve openings of the first flow control valve and the second flow control valve that optimize the liquid level in the thermosiphon section so that the liquid level in the tower bottom is constant are calculated based on a first model that represents the relationship between the first flow rate based on a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a fluctuation in a tower bottom liquid level, which is the liquid level of the absorbing liquid stored in the second regeneration section, and a valve opening of a second flow control valve that adjusts a second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate.

[0044] (8) A control method according to an eighth aspect is a control method for a CO2 recovery apparatus including a first regeneration unit that stores an absorbing liquid supplied from an absorption tower of a CO2 recovery apparatus to the regeneration tower, a second regeneration unit provided below the first regeneration unit, and a thermosiphon unit that is a piping connected from a lower part of the first regeneration unit to an upper part of the second regeneration unit via a heat exchanger, and the second regeneration unit includes a regeneration tower to which the absorbing liquid is supplied from the first regeneration unit through the thermosiphon unit, and an absorption tower, wherein when a measured value of the liquid level in the second regeneration unit exceeds a predetermined threshold, a valve aperture of a first flow rate control valve is decreased by a first predetermined amount and / or a valve aperture of the second flow rate control valve is increased by a third predetermined amount and / or a valve aperture of the second flow rate control valve is decreased by a fourth predetermined amount.

[0045] (9) A control method according to a ninth aspect is a control method for a CO2 recovery apparatus having a first regeneration section that stores an absorbing liquid supplied from an absorption tower of a CO2 recovery apparatus to the regeneration tower, a second regeneration section provided below the first regeneration section, and a thermosiphon section that is a piping connected from the lower part of the first regeneration section to the upper part of the second regeneration section via a heat exchanger, wherein the second regeneration section includes a regeneration tower to which the absorbing liquid is supplied from the first regeneration section through the thermosiphon section, and an absorption tower, wherein when the operating load of the CO2 recovery apparatus falls within a predetermined range in which it is assumed that the liquid level of the absorbing liquid in the piping arranged in the liquid phase portion upstream of the heat exchanger and the position of the piping constituting the thermosiphon section arranged in the horizontal direction are at the same height, the valve opening degree of the first flow control valve and the second flow control valve is not changed. [Explanation of symbols]

[0046] 1. Control device 2. Absorption tower 3...Regeneration Tower 4...Heat exchanger 21 Pump 31...1st playback part 32...2nd playback part 33, 331, 332, 333, 334, 335, 336, 337...Piping 34...heat exchanger 35 Pump 51, 52, 53, 54...Piping 61...Rich solution control valve 62 Lean solution control valve 71, 72...flow meter 73...Liquid level gauge 100...CO2 capture equipment 900...Computer 901··CPU 902...Main memory 903...Auxiliary storage device 904 Input / Output Interface 905 Communication Interface

Claims

1. CO ２ A regeneration tower of a recovery device, The CO ２ A first regeneration section that stores an absorbing liquid supplied from an absorption tower of a recovery device to the regeneration tower, and a second regeneration section that is provided below the first regeneration section; A thermosiphon section which is a pipe connected from a lower part of the first regeneration section to an upper part of the second regeneration section via a heat exchanger; having The second regeneration unit is supplied with the absorbing liquid from the first regeneration unit through the thermosiphon unit, Among the piping constituting the thermosiphon section, a piping arranged in a liquid phase portion upstream of the heat exchanger is provided in a range in which the liquid level of the absorption liquid fluctuates, and the volume of the piping arranged in a horizontal direction is smaller than the volume of the absorption liquid stored in the second regeneration section that is allowed to fluctuate. Regeneration tower.

2. The horizontally disposed pipe is not provided in a range where the liquid level of the absorption liquid varies. The regeneration tower according to claim 1.

3. A pipe constituting the thermosiphon unit is arranged in a range in which the liquid level of the absorption liquid fluctuates, the pipe being arranged in a vertical direction or in a direction inclined with respect to the vertical direction. The regenerator according to claim 2.

4. A CO2 purifier comprising the regeneration tower according to claim 1 or 2 and an absorption tower. ２ A control device for a recovery device, a first model expressing a relationship between a fluctuation in the liquid level of the thermosiphon section, a first flow rate based on a valve aperture of a first flow rate control valve that adjusts a first flow rate, which is the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower, and a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a second model expressing a relationship between a fluctuation in a tower bottom liquid level, which is the liquid level of the absorbing liquid stored in the second regeneration section, a second flow rate based on a valve aperture of a second flow rate control valve that adjusts a second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate, the valve apertures of the first flow rate control valve and the second flow rate control valve are calculated to optimize the liquid level of the thermosiphon section so that the tower bottom liquid level is constant. Control device.

5. A CO2 purifier comprising the regeneration tower according to claim 1 or 2 and an absorption tower. ２ A control device for a recovery device, When the measured value of the liquid level in the second regeneration section exceeds a predetermined threshold value, a valve opening degree of a first flow control valve that adjusts the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower is decreased by a first predetermined amount, and / or a valve opening degree of a second flow control valve that adjusts the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower is increased by a second predetermined amount, When the measured value of the liquid level in the second regeneration unit falls below a predetermined threshold, the valve opening degree of the first flow rate control valve is increased by a third predetermined amount and / or the valve opening degree of the second flow rate control valve is decreased by a fourth predetermined amount. Control device.

6. A CO2 purifier comprising the regeneration tower according to claim 1 or 2 and an absorption tower. ２ A control device for a recovery device, The CO ２ when the operating load of the recovery device falls within a predetermined range in which it is assumed that the liquid level of the absorption liquid in the piping arranged in the liquid phase portion upstream of the heat exchanger and the height of the arrangement position of the piping constituting the horizontally arranged thermosiphon unit are the same height, the valve openings of a first flow control valve that adjusts the flow rate of the absorption liquid supplied from the absorption tower to the regeneration tower and a second flow control valve that adjusts the flow rate of the absorption liquid supplied from the regeneration tower to the absorption tower are not changed; Control device.

7. CO ２ A CO recovery system including a regeneration tower, a second regeneration tower, and a thermosiphon unit, which is a pipe connected from a lower part of the first regeneration tower to an upper part of the second regeneration tower via a heat exchanger, and a regeneration tower to which the absorbing solution is supplied from the first regeneration tower through the thermosiphon unit. ２ A method for controlling a recovery device, comprising the steps of: a first model expressing a relationship between a fluctuation in the liquid level of the thermosiphon section, a first flow rate based on a valve opening of a first flow control valve that adjusts a first flow rate, which is the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower, and a circulation flow rate of the absorbing liquid flowing through the thermosiphon section, and a second model expressing a relationship between a fluctuation in a tower bottom liquid level, which is the liquid level of the absorbing liquid stored in the second regeneration section, a second flow rate based on a valve opening of a second flow control valve that adjusts a second flow rate, which is the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower, and the circulation flow rate, the valve openings of the first flow control valve and the second flow control valve that optimize the liquid level of the thermosiphon section so that the tower bottom liquid level is constant are calculated, and the first flow control valve and the second flow control valve are controlled with the calculated valve openings. Control methods.

8. CO ２ A CO recovery system including a regeneration tower, a second regeneration tower, and a thermosiphon unit, which is a pipe connected from a lower part of the first regeneration tower to an upper part of the second regeneration tower via a heat exchanger, and a regeneration tower to which the absorbing solution is supplied from the first regeneration tower through the thermosiphon unit. ２ A method for controlling a recovery device, comprising the steps of: When the measured value of the liquid level height of the absorbing liquid stored in the second regeneration section exceeds a predetermined threshold value, a valve opening degree of a first flow control valve that adjusts the flow rate of the absorbing liquid supplied from the absorption tower to the regeneration tower is decreased by a first predetermined amount, and / or a valve opening degree of a second flow control valve that adjusts the flow rate of the absorbing liquid supplied from the regeneration tower to the absorption tower is increased by a second predetermined amount, When a measured value of the liquid level of the absorbing liquid stored in the second regeneration section falls below a predetermined threshold, the valve opening degree of the first flow rate control valve is increased by a third predetermined amount and / or the valve opening degree of the second flow rate control valve is decreased by a fourth predetermined amount. Control methods.

9. CO ２ A CO recovery system including a regeneration tower, a second regeneration tower, and a thermosiphon unit, which is a pipe connected from a lower part of the first regeneration tower to an upper part of the second regeneration tower via a heat exchanger, and a regeneration tower to which the absorbing solution is supplied from the first regeneration tower through the thermosiphon unit. ２ A method for controlling a recovery device, comprising the steps of: The CO ２ when the operating load of the recovery device falls within a predetermined range in which it is assumed that the liquid level of the absorption liquid in the piping arranged in the liquid phase portion upstream of the heat exchanger and the position of the piping constituting the horizontally arranged thermosiphon unit will be at the same height, the valve openings of a first flow control valve that adjusts the flow rate of the absorption liquid supplied from the absorption tower to the regeneration tower and a second flow control valve that adjusts the flow rate of the absorption liquid supplied from the regeneration tower to the absorption tower are not changed; Control methods.

Images