Carbon dioxide recovery system

Abstract

To provide a carbon dioxide recovery system that can reduce energy consumption while preventing deterioration in efficiency in recovering carbon dioxides.SOLUTION: A carbon dioxide recovery system 10 is provided with: a gas generation source in which amounts of carbon dioxides included in exhausted gas are reduced when the source is in a first state more than when the source is in a second state; a carbon dioxide recovery device 15a equipped with a solution heating device 29 that heats a solution absorbing carbon dioxides so that carbon dioxides are diffused from the solution absorbing carbon dioxides having absorbed the carbon dioxides included in the gas; and a carbon dioxide recovery control device 16 that identifies a second time point at which the gas, exhausted from the gas generation source at a first time point at which the gas generation source identified using data concerning control of the gas generation source is switched from the second state to the first state, reaches the carbon dioxide recovery device 15a, and powers up the heating device at a third time point that is prior to the identified second time point.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide capture system. [Background technology]

[0002] The carbon dioxide capture systems disclosed in Patent Documents 1 and 2 include a predetermined device that discharges a gas containing carbon dioxide, and a carbon dioxide capture device that captures the carbon dioxide contained in the gas discharged from the device. The carbon dioxide capture device applied to this carbon dioxide capture system includes a carbon dioxide absorption tower and a carbon dioxide stripper tower, and is configured such that the gas supplied from the device is brought into gas-liquid contact with a carbon dioxide absorbing solution (aqueous amine solution) in the carbon dioxide absorption tower to absorb the carbon dioxide contained in the gas into the carbon dioxide absorbing solution, and the carbon dioxide stripper tower is heated to strip the carbon dioxide from the carbon dioxide absorbing solution.

[0003] In such carbon dioxide capture systems, there is a demand for improving energy efficiency (the ratio of the amount of carbon dioxide captured to the energy consumed) and preventing or suppressing a decrease. The carbon dioxide capture system of Patent Document 1 is equipped with multiple carbon dioxide capture devices and is configured to adjust the amount of gas distributed to the multiple carbon dioxide capture devices according to the flow rate of gas discharged from a specific device. With this configuration, the flow rate of gas introduced into each carbon dioxide capture device is maintained within an appropriate range, resulting in good energy efficiency. In addition, the carbon dioxide capture system of Patent Document 2 is configured to maintain a constant carbon dioxide capture rate by varying the amount of carbon dioxide absorbing solution circulated according to fluctuations in the gas flow rate.

[0004] However, it takes a certain amount of time for the temperature inside the carbon dioxide stripper to reach a target temperature (specifically, the temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution) after the amount of heat given to the carbon dioxide absorbing solution in the carbon dioxide stripper is changed (adjusted). For this reason, in a configuration in which the amount of heat is adjusted according to fluctuations in the flow rate of gas discharged from a specified device or the carbon dioxide concentration of the gas, the temperature inside the carbon dioxide stripper cannot follow fluctuations in the amount of carbon dioxide contained in the carbon dioxide absorbing solution (or fluctuations in the circulation amount of the carbon dioxide absorbing solution). For this reason, during the period from when the flow rate of the gas or the carbon dioxide concentration of the gas changes until the temperature inside the carbon dioxide stripper reaches the target temperature, energy efficiency (the ratio of the amount of carbon dioxide recovered to the energy consumed) decreases. Patent Document 1 and Patent Document 2 do not disclose a configuration for preventing or suppressing the decrease in energy efficiency during this period. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-187536 A [Patent Document 2] JP 2013-158685 A Summary of the Invention

[0006] (Problem to be solved by the invention) In view of the above circumstances, one object of the present invention is to provide a carbon dioxide capture system that can reduce energy consumption while preventing or suppressing a decrease in efficiency of carbon dioxide capture.

[0007] (Means for solving the problem) In order to achieve the above object, the carbon dioxide capture system according to the present invention comprises: a gas generation source that discharges a gas containing carbon dioxide, the gas generation source being configured such that a flow rate per unit time of the discharged gas or an amount of carbon dioxide contained in the gas is reduced while the gas generation source is in a first state compared to while the gas generation source is in a second state different from the first state; A gas generation source control device including data including information regarding a time point when the gas generation source is switched between the first state and the second state, and configured to switch the gas generation source to one of the first state and the second state based on the data; a carbon dioxide recovery apparatus including: a carbon dioxide absorption tower configured so that carbon dioxide contained in the gas discharged from the gas generation source is absorbed into a carbon dioxide absorbing solution; a carbon dioxide stripping tower configured so that carbon dioxide is stripped from the carbon dioxide absorbing solution; and a heating device configured so that the carbon dioxide absorbing solution having absorbed carbon dioxide can be heated to adjust the internal temperature of the carbon dioxide stripping tower to a temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution; a carbon dioxide recovery control device that uses the data to identify a first time point that is a time point at which the gas generation source is switched from the first state to the second state, identifies a second time point that is a time point at which the gas discharged from the gas generation source at the identified first time point reaches the carbon dioxide recovery device, and starts heating the carbon dioxide absorbing solution by the heating device at a third time point that is earlier than the identified second time point so that the internal temperature of the carbon dioxide stripper becomes a temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution at the second time point; Equipped with.

[0008] According to the carbon dioxide capture system of the present invention, based on data including information on the time (which can also be called the period, date, or time) when the gas generation source is switched between the first state and the second state, the heating device starts heating the carbon dioxide absorbing solution at a time before the time when the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas discharged from the gas generation source after the gas generation source is switched from the first state to the second state' reaches the carbon dioxide stripper tower. This makes it possible to bring the internal temperature of the carbon dioxide stripper tower closer to the 'temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution' by the time when the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas generated after the gas generation source is switched from the first state to the second state' reaches the carbon dioxide stripper tower. Therefore, it is possible to prevent or suppress a decrease in the carbon dioxide capture rate after the 'time when the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas generated after the gas generation source is switched from the first state to the second state' reaches the carbon dioxide stripper tower.' Therefore, according to the carbon dioxide capture system of the present invention, it is possible to reduce the energy consumption of the carbon dioxide capture device (i.e., the total energy consumption of the carbon dioxide capture system) without decreasing the carbon dioxide capture rate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of the carbon dioxide capture device. [Diagram 3] FIG. 3 is a graph illustrating the operation of the carbon dioxide capture system according to the first embodiment. [Figure 4] FIG. 4 is a graph illustrating the operation of the carbon dioxide capture system according to the modified example of the first embodiment. [Diagram 5] FIG. 5 is a diagram showing a schematic configuration of a carbon dioxide capture device in a carbon dioxide capture system according to the second embodiment. [Figure 6]FIG. 6 is a graph illustrating the operation of the carbon dioxide capture system according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First Embodiment FIG. 1 is a diagram showing a schematic configuration of a carbon dioxide capture system 10 according to a first embodiment. As shown in FIG. 1, the carbon dioxide capture system 10 includes a melting furnace 11, a melting furnace control device 12, a pretreatment device 13, a pretreatment control device 14, a carbon dioxide capture device 15a, a carbon dioxide capture control device 16, a process control device 17, and a gas path 18. Hereinafter, the carbon dioxide capture device 15a may be abbreviated as "capture device 15a", and the carbon dioxide capture control device 16 may be abbreviated as "capture control device 16". The melting furnace 11 and the capture device 15a are connected by a gas path 18. The pretreatment device 13 is disposed on the gas path 18. The melting furnace control device 12, the pretreatment control device 14, the capture control device 16, and the process control device 17 each include a computer including a CPU, a ROM, a RAM, a storage device, and an I / F (interface). The melting furnace control device 12, the pretreatment control device 14, the capture control device 16, and the process control device 17 are connected to each other so as to be able to transmit and receive signals via the I / F.

[0011] The melting furnace 11 is an example of the gas source of the present invention. The melting furnace 11 includes, for example, a furnace body (not shown) into which a solid metal material can be charged and which can store the molten metal material, and a combustion burner 111 capable of heating the metal material charged into the furnace body by burning fuel. The melting furnace 11 is configured to be able to melt the metal material charged into the furnace body by the combustion heat of the combustion burner 111, and is configured to maintain the molten metal material in a liquid state by keeping it warm by the combustion heat. The combustion exhaust gas of the combustion burner 111 is an example of the gas containing carbon dioxide of the present invention. Hereinafter, it may be simply referred to as gas.

[0012] The combustion burner 111 is configured to be able to change the amount of heat generated by combustion per unit time (hereinafter, sometimes referred to as "output of the combustion burner 111"). Specifically, the combustion burner 111 can reduce the output when maintaining the liquid state by keeping the molten metal material warm, compared to the output when melting the solid metal material. Hereinafter, the output when melting the solid metal material may be referred to as "high output", and the output when keeping the molten metal warm may be referred to as "low output". Note that the configuration of the melting furnace 11 is not particularly limited, and melting furnaces of various conventionally known configurations may be applied. A state in which the output of the combustion burner 111 is low output is an example of a first state, and a state in which the output of the combustion burner 111 is high output is an example of a second state.

[0013] The melting furnace control device 12 controls the melting furnace 11. A computer program for controlling the melting furnace 11 is stored in advance in the ROM of the computer of the melting furnace control device 12. Data including information regarding the time point at which the output of the combustion burner 111 of the melting furnace 11 is switched (in other words, the time point at which the output is switched between the first state and the second state) is stored in the storage device of the computer of the melting furnace control device 12. Hereinafter, this data may be referred to as melting furnace control data. The CPU of the computer of the melting furnace control device 12 reads out the computer program stored in the ROM, expands it in the RAM, and executes it. At this time, the CPU refers to the melting furnace control data stored in the storage device. As a result, the melting furnace control device 12 controls the output of the combustion burner 111 of the melting furnace 11 in accordance with the melting furnace control data (switches the output of the combustion burner 111 to either high output or low output).

[0014] As the melting furnace control data, for example, production plan data of the melting furnace 11 or data of a control command value of the combustion burner 111 of the melting furnace 11 is applied. The production plan data of the melting furnace 11 includes information indicating the time when the solid metal material to be melted is fed into the melting furnace 11 (in other words, the time when the output of the combustion burner 111 of the melting furnace 11 is set to high output) (note that "time" can also be referred to as a period, date, or time). Also, the control command value of the combustion burner 111 is a value in which the output of the combustion burner 111 of the melting furnace 11 (or a value for defining the output of the combustion burner 111 of the melting furnace 11) is linked to time.

[0015] The pretreatment device 13 is configured to perform a predetermined pretreatment on the gas discharged from the melting furnace 11. The pretreatment device 13 includes a dust collector 131, a cooler 132, and a gas pump 133. The dust collector 131 removes foreign matter such as dust from the gas discharged from the melting furnace 11 as a pretreatment. The cooler 132 cools the gas as a pretreatment to a temperature suitable for the absorption of carbon dioxide in the carbon dioxide absorption tower 22 of the recovery device 15a described later. The gas pump 133 sucks the gas discharged from the melting furnace 11 and delivers it to the carbon dioxide absorption tower 22 of the recovery device 15a. The configurations of the dust collector 131, the cooler 132, and the gas pump 133 are not particularly limited, and various conventionally known configurations can be applied.

[0016] The pre-processing control device 14 is configured to control the pre-processing device 13. A computer program for controlling the pre-processing device 13 is stored in advance in the ROM of the computer of the pre-processing control device 14. The CPU of the computer of the pre-processing control device 14 reads the computer program from the ROM, expands it in the RAM, and executes it. In this way, the control of the pre-processing device 13 by the pre-processing control device 14 is realized.

[0017] Fig. 2 is a diagram showing a schematic configuration of the recovery device 15a. As shown in Fig. 2, the recovery device 15a includes a carbon dioxide concentration meter 21a, a carbon dioxide absorption tower 22, a carbon dioxide stripper tower 23, a first solution path 24, a second solution path 25, a first heat exchanger 26, a first solution pump 27, a second solution pump 28, a solution heating device 29, and a condenser 30. In the following description, the carbon dioxide concentration meter 21a may be abbreviated as "concentration meter 21a", the carbon dioxide absorption tower 22 may be abbreviated as "absorption tower 22", and the carbon dioxide stripper tower 23 may be abbreviated as "stripping tower 23".

[0018] Concentration meter 21a is configured to be able to continuously measure the carbon dioxide concentration of the gas before it flows into stripping tower 23 in real time. Concentration meter 21a is connected to recovery control device 16. Recovery control device 16 continuously acquires the measurement results of the carbon dioxide concentration of the gas by concentration meter 21a in real time. Note that concentration meter 21a may be placed in a position where it can measure the carbon dioxide concentration of the gas before it flows into stripping tower 23, and a specific placement position is not limited. However, concentration meter 21a is preferably placed closer to absorption tower 22 than pretreatment device 13 (downstream of pretreatment device 13 in terms of the gas flow direction) to avoid being affected by the heat of the gas and the heat and dust generated by melting furnace 11.

[0019] The absorption tower 22 is configured so that the amine aqueous solution, which is an example of a carbon dioxide absorbing solution, absorbs carbon dioxide (in other words, so that carbon dioxide is removed from the gas) by gas-liquid contact between the gas and the amine aqueous solution. Inside the absorption tower 22, an upper filler 221 and a lower filler 222, which are members for promoting gas-liquid contact between the gas and the amine aqueous solution, are arranged. The upper filler 221 is arranged near the top of the absorption tower 22, and the lower filler 222 is arranged below it. One end of the gas path 18 is connected to the bottom of the absorption tower 22 (or its vicinity) and below the lower filler 222, and one end of a gas discharge path 31 is connected to the top of the absorption tower 22 (or its vicinity) and above the upper filler 221. The gas discharge path 31 is a path for discharging the gas from the absorption tower 22, and the other end is, for example, open to the atmosphere. One end of a first solution path 24, which will be described later, is connected to the bottom (or vicinity) of the absorption tower 22, below the lower filler 222, and one end of a second solution path 25, which will be described later, is connected to the upper part of the absorption tower 22, between the upper filler 221 and the lower filler 222.

[0020] The stripper tower 23 is configured to heat the amine aqueous solution to strip carbon dioxide from the amine aqueous solution. Inside the stripper tower 23, an upper filler 231 and a lower filler 232 are disposed as members for promoting gas-liquid contact between the amine aqueous solution and water vapor described later. The upper filler 231 is disposed near the top, and the lower filler 232 is disposed below it. The other end of the first solution path 24 is connected to the upper part of the stripper tower 23 between the upper filler 231 and the lower filler 232, and the other end of the second solution path 25 is connected to the bottom part (or its vicinity) of the stripper tower 23 and below the lower filler 232. In addition, the stripper tower 23 is disposed with a thermometer 233 capable of continuously measuring the internal temperature (temperature of the internal atmosphere) of the stripper tower 23 in real time. The thermometer 233 is connected to the recovery control device 16. The recovery control device 16 continuously acquires the actual measured value of the internal temperature of the stripper tower 23 measured by the thermometer 233 in real time.

[0021] The solution heating device 29 is configured to suck the amine aqueous solution from the inside of the stripper tower 23, heat the sucked amine aqueous solution, and return the heated amine aqueous solution and water vapor generated by heating to the inside of the stripper tower 23. The solution heating device 29 includes a third solution path 291, a medium circulation path 292, a medium pump 293, a medium heating device 294, and a second heat exchanger 295. The third solution path 291 is a path (e.g., a pipe) through which the amine aqueous solution can flow, and both ends of the path are connected to the stripper tower 23. The medium circulation path 292 is a closed-loop path through which a heating medium (e.g., oil) that is a fluid for heating the amine aqueous solution can circulate. The medium pump 293 is provided on the medium circulation path 292 and circulates the heating medium by operating. The medium heating device 294 is provided on the medium circulation path 292 and heats the heating medium circulating through the medium circulation path 292 by operating. The second heat exchanger 295 is provided on the medium circulation path 292 and the third solution path 291, and heats the aqueous amine solution by exchanging heat between the heating medium flowing through the medium circulation path 292 and the aqueous amine solution flowing through the third solution path 291.

[0022] The solution heating device 29 is configured to be switchable between an operating state and a standby state. In the operating state, the amine aqueous solution flowing through the third solution path 291 is heated to maintain the internal temperature of the stripping tower 23 at a temperature at which a reaction occurs in which carbon dioxide is stripped from the amine aqueous solution. Hereinafter, this temperature may be referred to as the "strip temperature." The specific value of the stripping temperature is appropriately set according to the composition of the amine aqueous solution to be applied. In the standby state, the amount of heat per unit time given to the amine aqueous solution flowing through the third solution path 291 is smaller than in the operating state. Specifically, the output of the medium pump 293 (flow rate of the heating medium per unit time) and the output of the medium heating device 294 (amount of heat given to the heating medium per unit time) are low. The energy consumed by the medium pump 293 and the medium heating device 294 in the standby state is smaller than the energy consumed in the operating state. When the solution heating device 29 is switched from the operating state to the standby state, the internal temperature of the stripping tower 23 drops to a temperature lower than the stripping temperature.

[0023] In this embodiment, the output of the medium pump 293 and the medium heating device 294 during the standby state is not 0, but continues to operate at an output greater than 0. This makes it possible to reduce energy consumption during the standby state, and also shorten the time required for the internal temperature of the stripping tower 23 to reach the stripping temperature when the solution heating device 29 is switched from the standby state to the operating state.

[0024] One end of the carbon dioxide discharge path 32 is connected to the top of the stripper tower 23 (or nearby), above the upper filler 231. A condenser 30 (a cooler and a gas-liquid separator) is arranged on the carbon dioxide discharge path 32. The condenser 30 is configured to separate water vapor from the mixture of water vapor and carbon dioxide discharged from the stripper tower 23. The condenser 30 is connected to the stripper tower 23 by a condensed water path 33. The condensed water path 33 is configured so that condensed water generated in the condenser 30 flows back above the upper filler 231 of the stripper tower 23.

[0025] The first solution path 24 is a path for feeding the aqueous amine solution from the absorption tower 22 to the stripper tower 23. One end of the first solution path 24 is connected to the bottom of the absorption tower 22, and the other end of the first solution path 24 is connected to the upper part of the stripper tower 23. A first solution pump 27 and a first heat exchanger 26, which will be described later, are provided on the first solution path 24. When the first solution pump 27 is operated, the aqueous amine solution accumulated at the bottom of the absorption tower 22 is fed to the stripper tower 23 through the first solution path 24. A known electric pump is used as the first solution pump 27.

[0026] The second solution path 25 is a path for feeding the aqueous amine solution from the stripper tower 23 to the absorption tower 22. One end of the second solution path 25 is connected to an upper part of the absorption tower 22, and the other end of the second solution path 25 is connected to a bottom part of the stripper tower 23. A second solution pump 28 and a first heat exchanger 26, which will be described later, are provided on the second solution path 25. When the second solution pump 28 is operated, the second solution pump 28 feeds the aqueous amine solution accumulated at the bottom part of the stripper tower 23 to the absorption tower 22 through the second solution path 25. A known electric pump can be used as the second solution pump 28.

[0027] The first heat exchanger 26 is disposed in an intermediate portion of each of the first solution path 24 and the second solution path 25. The first heat exchanger 26 is configured to exchange heat between the amine aqueous solution flowing through the first solution path 24 and the amine aqueous solution flowing through the second solution path 25. Specifically, the first heat exchanger 26 is configured to heat the amine aqueous solution flowing through the first solution path 24 and to cool the amine aqueous solution flowing through the second solution path 25.

[0028] The configurations of the absorption tower 22, the stripper tower 23, the first solution path 24, the second solution path 25, the solution heating device 29, the condenser 30, and the first heat exchanger 26 are not particularly limited, and various conventionally known configurations can be applied. Furthermore, the type of amine contained in the amine aqueous solution used in the recovery device 15a is not particularly limited, and various amines that are applied to known carbon dioxide recovery devices can be applied.

[0029] The process control device 17 cooperates with the melting furnace control device 12, the pre-treatment control device 14, and the capture control device 16 to control the carbon dioxide capture system 10. A computer program for controlling the carbon dioxide capture system 10 in cooperation with the melting furnace control device 12, the pre-treatment control device 14, and the capture control device 16 is stored in advance in the ROM of the computer of the process control device 17. The CPU of the computer of the pre-treatment control device 14 reads the computer program from the ROM, expands it into the RAM, and executes it. In this way, control of the carbon dioxide capture system 10 is realized.

[0030] Next, the basic operation of the carbon dioxide capture system 10 will be described.

[0031] The melting furnace control device 12 controls the melting furnace 11 based on the melting furnace control data stored in the storage device. Specifically, the melting furnace control device 12 identifies the time to switch the output of the combustion burner 111 of the melting furnace 11 from the melting furnace control data, and switches the output of the combustion burner 111 of the melting furnace 11 when the identified time arrives.

[0032] The carbon dioxide concentration of the gas discharged from the melting furnace 11 varies depending on the state of the melting furnace 11, specifically, whether the output of the combustion burner 111 is high or low. The carbon dioxide concentration of the gas discharged from the melting furnace 11 while the output of the combustion burner 111 is low (in other words, while the melting furnace 11 is in the first state) is lower than the carbon dioxide concentration of the gas discharged from the melting furnace 11 while the output of the combustion burner 111 is high (in other words, while the melting furnace 11 is in the second state). For example, the carbon dioxide concentration of the gas while the output of the combustion burner 111 is high is in the range of about 6 to 8 Vol%, and the carbon dioxide concentration of the gas while the output of the combustion burner 111 is low is about 1 Vol%.

[0033] The gas that has flowed into the absorption tower 22 through the gas path 18 moves from the bottom to the top inside the absorption tower 22. The aqueous amine solution that has flowed into the absorption tower 22 through the second solution path 25 flows down inside the absorption tower 22 from the top to the bottom. Then, the aqueous amine solution and the gas undergo gas-liquid contact (countercurrent contact) in the lower filler 222 arranged inside the absorption tower 22, whereby the carbon dioxide contained in the gas is absorbed into the aqueous amine solution. That is, the carbon dioxide is removed (separated) from the gas.

[0034] Note that the reaction in which the aqueous amine solution absorbs carbon dioxide (the reaction in which the amine combines with carbon dioxide) occurs in a temperature range of, for example, 40 to 50° C., and therefore the gas flowing into the inside of the absorption tower 22 through the gas path 18 is adjusted to a temperature suitable for the occurrence of the reaction by the cooler 132 of the pretreatment device 13 arranged on the gas path 18. In addition, the aqueous amine solution flowing in from the second solution path 25 is also adjusted to a temperature suitable for the occurrence of the reaction when passing through the first heat exchanger 26.

[0035] The gas from which carbon dioxide has been removed (sometimes referred to as off-gas) passes through the upper packing 221 and is discharged to the outside of the absorption tower 22 through the gas discharge path 31. The gas from which carbon dioxide has been removed is cooled while passing through the upper packing 221. As a result, water vapor contained in the gas is condensed and removed from the gas.

[0036] The aqueous amine solution that has absorbed carbon dioxide accumulates at the bottom of the absorption tower 22. The aqueous amine solution accumulated at the bottom of the absorption tower 22 is fed to the stripper tower 23 through the first heat exchanger 26 via the first solution path 24 by the operation of the first solution pump 27. The aqueous amine solution fed from the absorption tower 22 to the stripper tower 23 through the first solution path 24 is heated (or can be said to be preheated) by heat exchange with the aqueous amine solution flowing through the second solution path 25 in the first heat exchanger 26, and then flows into the stripper tower 23 from its upper part.

[0037] The aqueous amine solution that has flowed into the stripper tower 23 passes through the lower filler 232 and accumulates at the bottom of the stripper tower 23. A part of the aqueous amine solution that has accumulated at the bottom of the stripper tower 23 is heated by the solution heating device 29. The aqueous amine solution heated by the solution heating device 29 and the water vapor generated by heating flow into the inside of the stripper tower 23. As a result, the internal temperature of the stripper tower 23 is maintained at the stripping temperature. As a result, the aqueous amine solution flowing down from the top is heated, and carbon dioxide is stripped from the aqueous amine solution.

[0038] A mixture of water vapor generated by heating the amine aqueous solution and carbon dioxide stripped from the amine aqueous solution passes through the upper filler 231 of the stripper tower 23 and flows out of the stripper tower 23 through the carbon dioxide discharge path 32 connected to the top of the stripper tower 23. Then, water vapor is removed from this mixture in the condenser 30 arranged on the carbon dioxide discharge path 32. The condensed water generated in the condenser 30 is sent to the upper filler 231 of the stripper tower 23 through the condensed water path 33. As a result, the condensed water is used to cool the mixture passing through the upper filler 231.

[0039] The amine aqueous solution accumulated at the bottom of the stripper tower 23 is fed toward the absorption tower 22 through the second solution path 25 by the operation of the second solution pump 28. The amine aqueous solution flowing through the second solution path 25 exchanges heat with the amine aqueous solution flowing through the first solution path 24 in the first heat exchanger 26. This cools the amine aqueous solution fed from the stripper tower 23 through the second solution path 25 toward the absorption tower 22. The amine aqueous solution that has passed through the first heat exchanger 26 then flows into the absorption tower 22 from its upper portion. The amine aqueous solution fed to the inside of the absorption tower 22 flows down inside the absorption tower 22, absorbing carbon dioxide contained in the gas during that time.

[0040] In this manner, the aqueous amine solution circulates through the absorption tower 22, the first solution path 24, the stripper tower 23, and the second solution path 25 in this order. A part of the aqueous amine solution accumulated in the stripper tower 23 is heated by the solution heating device 29. While circulating, the aqueous amine solution repeats a reaction in which it absorbs carbon dioxide contained in the gas in the absorption tower 22 and strips the absorbed carbon dioxide in the stripper tower 23.

[0041] Next, the operation of the carbon dioxide capture system 10 when the output of the combustion burner 111 of the melting furnace 11 changes will be described. Fig. 3 is a graph explaining the operation of the carbon dioxide capture system 10 when the output of the combustion burner 111 of the melting furnace 11 changes. Here, the operation of the carbon dioxide capture system 10 when the output of the combustion burner 111 of the melting furnace 11 switches from high output to low output, and then switches from low output to high output (back to high output) is shown.

[0042] The horizontal axis of each graph is time. "CO2 concentration" is the actual measured value of the carbon dioxide concentration of the gas measured by the concentration meter 21a of the recovery device 15a. "Medium flow rate" is the flow rate per unit time of the heating medium flowing through the medium circulation path 292 of the solution heating device 29. The larger the value, the greater the output of the medium pump 293 of the solution heating device 29 (the energy consumption of the medium pump 293). "Stripping tower temperature" is the actual measured value of the internal temperature (temperature of the internal atmosphere) of the stripping tower 23. "CO2 capture amount" is the amount of carbon dioxide captured by the carbon dioxide capture system 10 per unit time. "CO2 capture rate" is the ratio indicated by the amount of carbon dioxide emitted in the stripping tower 23 to the amount of carbon dioxide absorbed in the aqueous amine solution.

[0043] The time before time P1 in each graph is the time when the output of the combustion burner 111 of the melting furnace 11 is high, and time P1 is the time when the output of the combustion burner 111 of the melting furnace 11 is switched from high to low. At time P1, gas discharged from the melting furnace 11 before time P1, i.e., when the output of the combustion burner 111 is high, is present in the gas path 18. Therefore, at time P1, the actual carbon dioxide concentration of the gas measured by the concentration meter 21a does not decrease.

[0044] Time point P2 is the time point when the actual carbon dioxide concentration of the gas measured by concentration meter 21a starts to decrease. When a certain time A1 has elapsed from time point P1, the gas generated in melting furnace 11 starts to flow into absorption tower 22 after time point P1, and the actual carbon dioxide concentration of the gas measured by concentration meter 21a starts to decrease. This time A1 is determined according to the specific configuration of carbon dioxide capture system 10 (e.g., the length of gas path 18, etc.), the capacity of gas pump 133 of pretreatment device 13 (i.e., the gas flow rate), etc.

[0045] The time point P2 may be a time point when the actual carbon dioxide concentration of the gas becomes less than a predetermined threshold value. In this case, the carbon dioxide concentration while the combustion burner 111 of the melting furnace 11 is at high output and while it is at low output may be measured in advance, and the intermediate value between these carbon dioxide concentrations may be set in advance as the predetermined threshold value (the predetermined threshold value may be stored in advance in the storage device of the computer of the recovery control device 16).

[0046] Time P3 is the time when time A2 has elapsed from time P2. When time A2 has elapsed from time P2, the aqueous amine solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time P1" in the absorption tower 22 starts to flow into the stripper tower 23. Note that this time A2 is determined depending on the configuration (e.g., the length of the first solution path 24) and operation (the output of the first solution pump 27) of the recovery device 15a.

[0047] At time P3, the recovery control device 16 switches the solution heating device 29 from an operating state to a standby state. Therefore, the internal temperature of the stripping tower 23 starts to decrease from time P3. Then, at time P4, when a certain time τ1 has elapsed from time P3, the internal temperature of the stripping tower 23 reaches a temperature lower than the stripping temperature. This time τ1 is determined according to the specific configurations of the solution heating device 29 and the stripping tower 23.

[0048] When the solution heating device 29 switches from an operating state to a standby state at time P3, the internal temperature of the stripper tower 23 decreases at a predetermined rate with time due to the residual heat of the heating medium and the aqueous amine solution, etc. On the other hand, after time P3, the amount of carbon dioxide contained in the aqueous amine solution flowing into the stripper tower 23 decreases. For this reason, the carbon dioxide recovery rate temporarily increases between time P3 and time P4. FIG. 3 shows an example in which the carbon dioxide recovery rate is the same value after time P3 and before time P2, but since the carbon dioxide recovery rate is a value according to the internal temperature of the stripper tower 23, it may show a trend different from that shown in this graph.

[0049] Time point P5 is the time point when the output of the combustion burner 111 of the melting furnace 11 is switched from low to high. Note that time point P5 is an example of the first time point of the present invention. The recovery control device 16 identifies this time point P5 based on the melting furnace control data. Note that the recovery control device 16 acquires the melting furnace control data from the melting furnace control device 12 via the process control device 17. At this time point P5, gas discharged from the melting furnace 11 during the time when the output of the combustion burner 111 is low is present in the gas path 18. Therefore, at time point P5, the actual carbon dioxide concentration measured by the concentration meter 21a of the recovery device 15a does not change.

[0050] Time P7 is the time when the actual measurement value of the carbon dioxide concentration by the concentration meter 21a rises, and is the time after the time A3 has passed from time P5. When a certain amount of time has passed from time P5, the gas generated in the melting furnace 11 after time P5 starts to flow into the absorption tower 22. Therefore, the actual measurement value of the carbon dioxide concentration by the concentration meter 21a rises. This certain amount of time is time A3. Time A3 is determined according to the configuration of the carbon dioxide capture system 10 (e.g., the length of the gas path 18, etc.) and the capacity of the gas pump 133 of the pretreatment device 13 (i.e., the gas flow rate). When a certain amount of time has passed from time P7, the amine aqueous solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time P5" in the absorption tower 22 starts to flow into the stripper tower 23. This certain amount of time is time A4. Time A4 is determined according to the configuration of the capture device 15a. Time point P8 is a time point after the lapse of time A4 from time point P7, and is the time point when the aqueous amine solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time point P5" in the absorption tower 22 starts to flow into the stripper tower 23. Time point P8 is an example of the second time point in the present invention.

[0051] The capture control device 16 switches the solution heating device 29 from the standby state to the operating state at time P6 before time P8 so that the internal temperature of the stripping tower 23 is maintained at the stripping temperature (in other words, returned to the stripping temperature) at time P8. Note that time P5 can be identified from the melting furnace control data. Time A3 from time P5 to time P7, time A4 from time P7 to time P8, and time τ2 between time P6 and time P8 are determined according to the configuration of the carbon dioxide capture system 10. Therefore, the capture control device 16 can identify time P6 based on time P5, time A3, time A4, and time τ2. Note that time P6 is an example of a third time point in the present invention.

[0052] The recovery control device 16 can identify the time P6 before the time P6 actually arrives by identifying the time P5 from the melting furnace control data. Therefore, the recovery control device 16 can switch the solution heating device 29 from the standby state to the operating state when the time P6 arrives.

[0053] The times A1, A2, A3, A4, and τ2 are stored in advance in the storage device of the computer of the recovery control device 16. However, the recovery control device 16 may calculate the times A1, A2, A3, A4, and τ2. For example, the times A1 and A3 can be calculated from the length of the gas path 18 and the flow rate of the gas in the gas path 18. The times A2 and A4 can be calculated from the length of the first solution path 24 of the recovery device 15a and the flow rate of the amine aqueous solution in the first solution path 24. The time τ2 can be calculated from the capacity of the solution heating device 29, the heat capacity of the stripping tower 23, and the difference in the internal temperature of the stripping tower 23 between when the solution heating device 29 is at low output and when it is at high output. For this reason, the computer memory device of the recovery control device 16 stores formulas or tables for calculating these times A1, A2, A3, A4, and τ2, and these formulas or tables are used to calculate these times A1, A2, A3, A4, and τ2.

[0054] The recovery control device 16 may determine the time τ2 according to the difference (temperature difference) between the internal temperature of the stripping tower 23 at time P6 (or immediately before) and the dissipation temperature (i.e., the target value of the internal temperature of the stripping tower 23 at time P8). That is, the larger the temperature difference, the longer the time from "the time when the solution heating device 29 is switched from the standby state to the operating state" to "the time when the internal temperature of the stripping tower 23 reaches the dissipation temperature". Therefore, the recovery control device 16 shortens the time τ2 as the temperature difference becomes smaller, and lengthens the time τ2 as the temperature difference becomes larger. According to this configuration, by shortening the time τ2 when the temperature difference is small, it is possible to reduce wasteful energy consumption. Also, by lengthening the time τ2 (in other words, by advancing the time P6) when the temperature difference is large, it is possible to prevent the occurrence of a situation in which "the internal temperature of the stripping tower has not reached the dissipation temperature" at the time point P8 arrives. That is, it is possible to prevent a decrease in the carbon dioxide recovery rate.

[0055] In this way, the recovery control device 16 uses the melting furnace control data to identify the time P5 at which the combustion burner 111 of the melting furnace 11 switches from low output to high output. Furthermore, the recovery control device 16 identifies the time P8 at which the amine aqueous solution that has absorbed the "carbon dioxide contained in the gas discharged from the melting furnace 11 after the identified time P5" reaches the stripping tower 23. Then, the recovery control device 16 switches the state of the solution heating device 29 from a standby state to an operating state at a time P6 prior to the time P8 so that the internal temperature of the stripping tower 23 returns to the stripping temperature at the identified time P8. With this configuration, even if the carbon dioxide concentration of the gas fluctuates, the energy consumption of the recovery device 15a (i.e., the overall energy consumption of the carbon dioxide recovery system 10) can be reduced without reducing the carbon dioxide recovery rate.

[0056] That is, the carbon dioxide concentration of the gas generated in the melting furnace 11 while the output of the combustion burner 111 of the melting furnace 11 is low is lower than the carbon dioxide concentration of the gas generated while the output of the combustion burner 111 of the melting furnace 11 is high. Therefore, the amount of carbon dioxide that can be recovered from the gas generated while the output of the combustion burner 111 of the melting furnace 11 is low (in other words, the amount of carbon dioxide absorbed in the amine aqueous solution) is less than the amount of carbon dioxide that can be recovered from the gas generated while the output of the combustion burner 111 of the melting furnace 11 is high. Therefore, if the solution heating device 29 is kept in operation regardless of whether the output of the combustion burner 111 is high or low, the energy consumed by the solution heating device 29 becomes excessive compared to the amount of carbon dioxide recovered while the output of the combustion burner 111 of the melting furnace 11 is low, resulting in a waste of energy.

[0057] On the other hand, it takes time τ2 for the internal temperature of the stripper tower 23 to return to the stripping temperature after the solution heating device 29 is switched from the standby state to the operating state. For this reason, in the control of switching the output of the medium pump 293 of the solution heating device 29 and the medium heating device 294 from the standby state to the operating state (i.e., control based on the actual value of the carbon dioxide concentration measured by the concentration meter 21a) at time P7 (i.e., at the time when the actual value of the carbon dioxide concentration measured by the concentration meter 21a becomes high), time P8 may arrive before time τ2 has elapsed from time P7 (i.e., "gas discharged from the melting furnace 11 at the time after time P7" flows into the stripper tower 23). For this reason, in this case, the recovery rate of carbon dioxide decreases from time P8 until the internal temperature of the stripper tower 23 returns to the stripping temperature. The dashed line in the graph indicates the change in the flow rate of the heating medium and the internal temperature of the stripper tower 23 when the solution heating device 29 is switched from the standby state to the operating state at time P7.

[0058] According to the carbon dioxide capture system 10 of the first embodiment, when the carbon dioxide concentration of the gas decreases (time point P2), the state of the solution heating device 29 is switched from an operating state to a standby state, thereby reducing the energy consumption of the solution heating device 29. In addition, according to the carbon dioxide capture system 10, the internal temperature of the stripping tower 23 can be returned to the stripping temperature at "time point P8 at which the 'amine aqueous solution that has absorbed carbon dioxide from the gas with an increased carbon dioxide concentration' is predicted to reach the stripping tower 23 when the carbon dioxide concentration of the gas increases again," which is determined by the melting furnace control data. Therefore, it is possible to prevent or suppress a decrease in the carbon dioxide capture rate at the time after time point P8. Therefore, according to the carbon dioxide capture system 10 of the first embodiment, the energy consumption of the capture device 15a can be reduced without decreasing the carbon dioxide capture rate.

[0059] Furthermore, the carbon dioxide capture system 10 according to the first embodiment is suitable for cases where it is difficult to install a concentration meter 21a for measuring the carbon dioxide concentration of the gas in the melting furnace 11 or in its vicinity. That is, if the concentration meter 21a is installed in the melting furnace 11 or in its vicinity and the carbon dioxide concentration of the gas immediately after it is discharged from the melting furnace 11 can be measured, then by switching the state of the solution heating device 29 based on the carbon dioxide concentration immediately after it is discharged from the melting furnace 11, it may be possible to control the internal temperature of the stripping tower 23 to return to the stripping temperature before the aqueous amine solution that has absorbed carbon dioxide from "the gas generated in the melting furnace 11 after the output of the combustion burner 111 is switched from low output to high output" reaches the stripping tower 23. More specifically, if the "time required for the gas discharged from the melting furnace 11 to reach the absorption tower 22 and for the 'amine aqueous solution that has absorbed carbon dioxide from the reaching gas' to reach the stripper tower 23" is longer than the "time required for the internal temperature of the stripper tower 23 to return to the stripper temperature after the solution heating device 29 is switched from a standby state to an operating state," the internal temperature of the stripper tower 23 can be returned to the stripper temperature before "the gas discharged from the melting furnace 11 reaches the absorption tower 22 and the amine aqueous solution that has absorbed carbon dioxide from the reaching gas reaches the stripper tower 23," by switching the state of the solution heating device 29 from a standby state to an operating state after the point at which the carbon dioxide concentration of the gas immediately after being discharged from the melting furnace 11 changes.

[0060] However, since the gas immediately after being discharged from the melting furnace 11 is at a high temperature, it is difficult to measure the carbon dioxide concentration of the gas immediately after being discharged from the melting furnace 11. In addition, the melting furnace 11 and its surrounding environment may not be suitable for installing the concentration meter 21a due to the influence of the atmospheric temperature, dust, etc. In such a case, the carbon dioxide concentration of the gas immediately after being discharged from the melting furnace 11 cannot be measured. According to the first embodiment, even in such a case, the recovery control device 16 controls the output of the medium pump 293 and the output of the medium heating device 294 of the solution heating device 29 based on the melting furnace control data, thereby reducing the energy consumption of the recovery device 15a without reducing the carbon dioxide recovery rate.

[0061] Depending on the configuration of the carbon dioxide capture system 10, the "time required for the gas discharged from the melting furnace 11 to reach the absorption tower 22 and for the aqueous amine solution that has absorbed carbon dioxide from the gas that has reached the absorption tower 22 to reach the stripper tower 23" may be shorter than the "time required for the internal temperature of the stripper tower 23 to return to the stripper temperature after the state of the solution heating device 29 is switched from the standby state to the operating state." For example, this corresponds to a case where the melting furnace 11 and the capture device 15a are arranged close to each other and the gas path 18 is short. In such a case, in a configuration in which the solution heating device 29 is controlled based on the actual measured value of the carbon dioxide concentration by the concentration meter 21a, even if the carbon dioxide concentration of the gas immediately after being discharged from the melting furnace 11 can be measured, the internal temperature of the stripper tower 23 cannot be returned to the stripper temperature before "the gas discharged from the melting furnace 11 reaches the absorption tower 22 and the aqueous amine solution that has absorbed carbon dioxide from the gas that has reached the absorption tower 22 reaches the stripper tower 23."

[0062] Even in such a case, according to the carbon dioxide capture system 10 according to the first embodiment, the internal temperature of the stripper tower 23 can be returned to the stripping temperature by the time "the gas discharged from the melting furnace 11 reaches the absorption tower 22, and the aqueous amine solution that has absorbed carbon dioxide from the gas that has reached the stripper tower 23." Therefore, the energy consumption of the carbon dioxide capture system 10 can be reduced without reducing the carbon dioxide capture rate.

[0063] In the above embodiment, the solution heating device 29 is controlled so that the internal temperature of the stripper tower 23 returns to the stripping temperature before the amine aqueous solution that absorbed carbon dioxide from the "gas generated in the melting furnace 11 after the output of the combustion burner 111 was switched from low output to high output" reaches the stripper tower 23, but the present invention is not limited to such a configuration. For example, the recovery control device 16 may be configured to switch the solution heating device 29 from the standby state to the operating state before the time point P7 at which the actual measurement value of the carbon dioxide concentration by the concentration meter 21a increases. With such a configuration, the internal temperature of the stripper tower 23 can be made higher at the time point when the amine aqueous solution that absorbed carbon dioxide from the "gas generated in the melting furnace 11 after the output of the combustion burner 111 was switched from low output to high output" reaches the stripper tower 23, compared to a configuration in which the solution heating device 29 is switched from the standby state to the operating state based on the actual measurement value of the carbon dioxide concentration by the concentration meter 21a. Therefore, the energy consumption of the recovery device 15a can be reduced.

[0064] (Modification) Next, a modified example of the first embodiment will be described. Fig. 4 is a diagram showing the operation of the carbon dioxide capture system 10 according to the modified example. The carbon dioxide capture system 10 according to the modified example is configured to switch the solution heating device 29 from an operating state to a standby state based on the melting furnace control data. Fig. 4 is a graph explaining the operation of the carbon dioxide capture system 10 according to the modified example. Note that time points P4 to P8 are the same as in the above embodiment.

[0065] The recovery control device 16 identifies the time when the output of the combustion burner 111 of the melting furnace 11 is switched from high output to low output from the melting furnace control data. The time Q1 is the "time when the output of the combustion burner 111 of the melting furnace 11 is switched from high output to low output" identified from the melting furnace control data. The time Q1 is an example of a fourth time point of the present invention. Before the time Q1, the output of the combustion burner 111 of the melting furnace 11 is high output. Then, the recovery control device 16 identifies the time when a certain time B1 has passed from the time Q1 as the time Q2 when the "gas generated in the melting furnace 11 after the time Q1" reaches the stripping tower 23, and further identifies the time when a certain time B2 has passed from the time Q2 as the time Q3 when the amine aqueous solution that has absorbed carbon dioxide from the "gas generated in the melting furnace 11 after the time Q1" reaches the stripping tower 23. Then, the recovery control device 16 switches the solution heating device 29 from the operating state to the standby state at the time Q3. Time point Q3 is an example of a fifth time point according to the present invention.

[0066] In this way, the recovery control device 16 may identify the time when the solution heating device 29 is switched from the operating state to the standby state based on the melting furnace control data. Even with such a configuration, the same effects as those of the above embodiment can be achieved. Note that time B1 and time B2 are determined according to the specific configuration of the carbon dioxide recovery system 10. Furthermore, time B1 and time B2 are stored in advance in a storage device of the computer of the recovery control device 16. Also, the recovery control device 16 may calculate time B1 and time B2.

[0067] In this case, the recovery control device 16 may set the time when the solution heating device 29 is switched from the operating state to the standby state to a time before the time Q3 for the following reason. When the solution heating device 29 is switched from the operating state to the standby state, the internal temperature of the stripping tower 23 does not drop immediately but gradually. Therefore, until a certain amount of time has passed since the solution heating device 29 was switched from the operating state to the standby state, the internal temperature of the stripping tower 23 is within the range of the stripping temperature. Therefore, the carbon dioxide recovery rate does not decrease during this period. Therefore, by switching the solution heating device 29 from the operating state to the standby state at a time before the time Q3, the amount of energy consumed by the solution heating device 29 can be further reduced without decreasing the carbon dioxide recovery rate.

[0068] Second Embodiment Next, a second embodiment will be described. The carbon dioxide capture system 10 according to the second embodiment uses an actual measured value of the gas flow rate to control switching between the operating state and the standby state of the solution heating device 29. Note that the same reference numerals as in the first embodiment are used for components common to the first embodiment, and descriptions thereof may be omitted.

[0069] FIG. 5 is a diagram showing a schematic configuration of the capture device 15b of the carbon dioxide capture system 10 according to the second embodiment. As shown in FIG. 5, the capture device 15b of the second embodiment includes a gas flowmeter 21b, but does not need to include a concentration meter 21a. In addition, the gas pump 133 of the pretreatment device 13 is configured to be able to change the output (the flow rate per unit time of the gas flowing through the gas path 18). Specifically, the gas pump 133 is configured to be able to switch the output between high output and low output. The high output is an output that can suck in the entire amount of gas generated from the melting furnace 11 while the output of the combustion burner 111 is high output from the melting furnace 11. The low output is an output lower than the high output, and can suck in the entire amount of gas generated from the melting furnace 11 while the output of the combustion burner 111 is low output from the melting furnace 11, but cannot suck in the entire amount of gas generated from the melting furnace 11 while the output of the combustion burner 111 is high output from the melting furnace 11. Other than that, the same configuration as in the first embodiment can be applied. The gas flow meter 21b is disposed downstream of the gas flow from the pretreatment device 13, and is configured to be able to continuously measure in real time the flow rate per unit time of the gas fed to the absorption tower 22 of the capture device 15b. Note that the carbon dioxide capture system 10 according to the second embodiment may have the same configuration as the first embodiment, except that the capture device 15b applied differs from that of the first embodiment as described above.

[0070] 6 is a graph explaining the operation of the carbon dioxide capture system 10 when the output of the combustion burner 111 of the melting furnace 11 changes. "Gas flow rate" is the actual value of the flow rate of gas per unit time measured by the gas flowmeter 21b of the capture device 15b (hereinafter, may be simply referred to as "gas flow rate"). The rest is the same as in the first embodiment.

[0071] The time before time point R1 in each graph is the time when the output of the combustion burner 111 of the melting furnace 11 is high, and time point R1 is the time when the output of the combustion burner 111 of the melting furnace 11 is switched from high to low. The pretreatment control device 14 switches the output of the gas pump 133 from high to low in response to (for example, approximately simultaneously with) the switching of the output of the combustion burner 111 from high to low. Note that since gas is compressible, the actual measured value of the gas flow rate by the gas flowmeter 21b does not immediately decrease at time point R1.

[0072] Time point R2 is the time point when the actual gas flow rate measured by the gas flow meter 21b starts to decrease. When a certain time C1 has elapsed from time point R1, the actual gas flow rate measured by the gas flow meter 21b decreases. This time C1 is determined according to the specific configuration of the carbon dioxide capture system 10 (e.g., the length of the gas path 18, etc.) and the capacity of the gas pump 133 of the pretreatment device 13 (i.e., the gas flow rate), etc.

[0073] The time point R2 may be a time point when the actual measured value of the gas flow rate falls below a predetermined threshold value. In this case, the steady gas flow rate while the gas pump 133 is at high output and the steady gas flow rate while the gas pump 133 is at low output may be measured in advance, and the intermediate value between these flow rates may be set in advance as the predetermined threshold value (the predetermined threshold value may be stored in advance in the storage device of the computer of the collection control device 16).

[0074] Time point R3 is a time point when time C2 has elapsed from time point R2. When time C2 has elapsed from time point R2, the aqueous amine solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time point R1" in the absorption tower 22 starts to flow into the stripper tower 23. Note that this time C2 is determined depending on the configuration (e.g., the length of the first solution path 24) and operation (the output of the first solution pump 27) of the recovery device 15b.

[0075] At time R3, the recovery control device 16 switches the solution heating device 29 from an operating state to a standby state. Therefore, the internal temperature of the stripper tower 23 starts to decrease from time R3. Then, at time R4, which is a certain time τ1 after time R3, the internal temperature of the stripper tower 23 reaches a temperature lower than the stripping temperature.

[0076] Time point R5 is the time point when the output of the combustion burner 111 of the melting furnace 11 is switched from low output to high output. Note that time point R5 is an example of the first time point of the present invention. The recovery control device 16 identifies this time point R5 by the melting furnace control data. The pretreatment control device 14 switches the output of the gas pump 133 from low output to high output according to (for example, approximately at the same time) the time point when the output of the combustion burner 111 of the melting furnace 11 is switched from low output to high output. Even if the output of the gas pump 133 is switched from low output to high output, the flow rate of the gas in the gas path 18 does not increase immediately due to the resistance of the gas flow in the gas path 18. Therefore, at time point R5, the actual measurement value of the gas flow rate by the gas flowmeter 21b of the recovery device 15b does not change.

[0077] Time R7 is the time when the actual measurement value of the gas flow rate by the gas flow meter 21b rises, and is the time after the time C3 has passed from time R5. When a certain amount of time has passed from time R5, the gas generated in the melting furnace 11 starts to flow into the absorption tower 22 after time R5. Therefore, the actual measurement value of the gas flow rate by the gas flow meter 21b rises. This certain amount of time is time C3. Time C3 is determined according to the configuration of the carbon dioxide capture system 10 (for example, the length of the gas path 18, etc.) and the capacity of the gas pump 133 of the pretreatment device 13. In particular, time C3 becomes longer as the distance between the gas pump 133 of the gas path 18 and the melting furnace 11 increases. When a certain amount of time has passed from time R7, the amine aqueous solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time R5" in the absorption tower 22 starts to flow into the stripper tower 23. This certain amount of time is time C4. Time C4 is determined according to the configuration of the capture device 15b. Time point R8 is a time point after the lapse of time C4 from time point R7, and is the time point when the aqueous amine solution that has absorbed "carbon dioxide contained in the gas generated in the melting furnace 11 after time point R5" in the absorption tower 22 starts to flow into the stripper tower 23. Time point R8 is an example of the second time point in the present invention.

[0078] The capture control device 16 switches the solution heating device 29 from the standby state to the operating state at time R6 before time R8 so that the internal temperature of the stripping tower 23 is maintained at the stripping temperature at time R8. Note that time R5 can be identified from the melting furnace control data. The time C3 from time R5 to time R7, the time C4 from time R7 to time R8, and the time τ2 between time R6 and time R8 are determined according to the configuration of the carbon dioxide capture system 10. Therefore, the capture control device 16 can identify time R6 based on time R5, time C3, time C4, and time τ2. Note that time R6 is an example of a third time point in the present invention.

[0079] The recovery control device 16 can identify the time point R5 from the melting furnace control data, and can identify the time point R6 before the time point R6 actually arrives. Therefore, the recovery control device 16 can switch the solution heating device 29 from the standby state to the operating state when the time point R6 arrives.

[0080] The times C1, C2, C3, C4, and τ2 are stored in advance in a storage device of the computer of the collection control device 16. However, the collection control device 16 may calculate the times C1, C2, C3, C4, and τ2 in the same manner as in the first embodiment.

[0081] According to the carbon dioxide capture system 10 according to the second embodiment, it is possible to achieve the same effects as those of the first embodiment.

[0082] <Summary of the embodiment> The carbon dioxide capture system 10 according to this embodiment is a gas generation source (melting furnace 11) that discharges a gas containing carbon dioxide, the gas generation source (melting furnace 11) being configured such that, while in a first state, the flow rate per unit time of the discharged gas or the amount of carbon dioxide contained in the gas is smaller than while in a second state different from the first state; a gas generation source control device (melting furnace control device 12) that includes data (melting furnace control data) including information regarding the time point when the gas generation source (melting furnace 11) is switched between the first state and the second state, and that is configured to switch the gas generation source (melting furnace 11) between the first state and the second state based on the data (melting furnace control data); carbon dioxide recovery devices 15a, 15b including an absorption tower 22 configured so that carbon dioxide contained in the gas discharged from the gas generation source (melting furnace 11) is absorbed into a carbon dioxide absorbing solution, a carbon dioxide stripping tower 23 configured so that carbon dioxide is stripped from the carbon dioxide absorbing solution, and a heating device (solution heating device 29) configured so that the carbon dioxide absorbing solution having absorbed carbon dioxide can be heated to adjust the internal temperature of the carbon dioxide stripping tower 23 to a temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution; and a carbon dioxide recovery control device 16 that uses the data (melting furnace control data) to identify a first point in time (points P5, R4) at which the gas generation source (melting furnace 11) switches from the first state to the second state, identifies a second point in time (points P8, R8) at which the gas discharged from the gas generation source (melting furnace 11) at the identified first point in time (points P5, R5) reaches the carbon dioxide recovery devices 15a, 15b, and starts heating the carbon dioxide absorbing solution by the heating device (solution heating device 29) at a third point in time (points P6, R6) that is earlier than the identified second point in time.

[0083] According to this embodiment, the energy consumption of the carbon dioxide capture system 10 can be reduced without decreasing the carbon dioxide capture rate. That is, when the carbon dioxide concentration of the gas decreases or the gas flow rate decreases, the output of the medium pump 293 and the output of the medium heater 294 of the heating device (solution heater 29) are reduced (switched from the operating state to the standby state), thereby reducing the energy consumption of the solution heater 29. Then, based on data (melting furnace control data) including information regarding the time of switching between the first state and the second state of the gas generation source (melting furnace 11), the heating device (solution heater 29) is switched from the standby state to the operating state at a time before "the time when the carbon dioxide absorbing solution that absorbed carbon dioxide from 'the gas generated after the time when the gas generation source (melting furnace 11) was switched from the first state to the second state' reaches the carbon dioxide stripper 23". With this configuration, a decrease in the carbon dioxide recovery rate can be prevented or suppressed after "the point at which the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas generated after the gas generation source (melting furnace 11) is switched from the first state to the second state' reaches the carbon dioxide stripping tower 23."

[0084] In this case, the effect of preventing or suppressing a decrease in the carbon dioxide recovery rate can be enhanced by returning the internal temperature of the carbon dioxide diffusion tower 23 to the "temperature at which carbon dioxide is diffused from the carbon dioxide diffusion solution" by the time "the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas generated after the gas generation source (melting furnace 11) is switched from the first state to the second state' reaches the carbon dioxide diffusion tower 23."

[0085] The carbon dioxide capture system 10 according to this embodiment is The carbon dioxide recovery control device 16 determines the length of time (time τ2) between the second point (time P8, time R8) and the third point (time P6, time R6) depending on the difference between the internal temperature of the carbon dioxide diffusion tower 23 when the gas generation source (melting furnace 11) switches from the first state to the second state and the temperature at which the carbon dioxide absorbing solution undergoes a reaction to diffuse carbon dioxide.

[0086] According to such a configuration, it is possible to enhance the effect of reducing the amount of energy consumed. That is, the time from when the heating device (solution heating device 29) starts heating and raising the temperature of the carbon dioxide absorbing solution (from when the standby state is switched to the operating state) until the internal temperature of the carbon dioxide stripper tower 23 reaches the "temperature at which the carbon dioxide absorbing solution strips carbon dioxide" varies depending on the difference between the "internal temperature of the carbon dioxide stripper tower 23 at the time when the gas generation source (melting furnace 11) is switched from the first state to the second state" and the "temperature at which the reaction of the carbon dioxide absorbing solution stripping carbon dioxide occurs." More specifically, as this difference increases, the time until the internal temperature of the carbon dioxide stripper tower 23 reaches the "temperature at which the carbon dioxide absorbing solution strips carbon dioxide" becomes longer. Therefore, by determining the length of time (τ2) between the second point (point P8, point R8) and the third point (point P6, point R6) in accordance with the temperature difference, it is possible to reduce unnecessary energy consumption and prevent the occurrence of a situation in which the internal temperature of the carbon dioxide diffusion tower 23 has not reached the "temperature at which the carbon dioxide diffusion solution undergoes a reaction to diffuse carbon dioxide" at the "point at which the carbon dioxide diffusion solution, which has absorbed carbon dioxide from the gas generated after the gas generation source (melting furnace 11) is switched from the first state to the second state, reaches the carbon dioxide diffusion tower 23."

[0087] In the carbon dioxide capture system 10 according to this embodiment, The gas generation source is a melting furnace 11 for melting a metal material, The data is production plan data including the time points at which the metal material is melted in the melting furnace 11, or control data for the combustion burner 111 including temporal fluctuations in the output of the combustion burner 111.

[0088] According to such a configuration, it is possible to improve the accuracy of the time when the heating device (solution heating device 29) is switched from the standby state to the operating state.

[0089] In the carbon dioxide capture system 10 according to this embodiment, The carbon dioxide recovery control device 16 uses the data (melting furnace control data) to identify a fourth point in time (point Q1) at which the gas generation source (melting furnace 11) switches from the second state to the first state, identifies a fifth point in time (point Q3) at which the gas discharged from the gas generation source (melting furnace 11) at the identified fourth point in time (point Q1) reaches the carbon dioxide recovery devices 15a, 15b, and at the identified fifth point in time (point Q3), reduces the amount of heat per unit time that the heating device (solution heating device 29) imparts to the carbon dioxide absorbing solution by the heating device (solution heating device 29) to be less than the amount of heat per unit time that was imparted to the carbon dioxide absorbing solution prior to the fifth point in time.

[0090] According to such a configuration, based on data (melting furnace control data) including information regarding the time point when the gas generation source (melting furnace 11) switches between the first state and the second state, it is possible to bring closer (or coincide) with the time point when the temperature of the carbon dioxide stripper 23 starts to decrease, relative to the time point when the carbon dioxide absorbing solution that has absorbed carbon dioxide from the 'gas generated after the gas generation source (melting furnace 11) switches from the second state to the first state' reaches the carbon dioxide stripper 23. This makes it possible to further enhance the effect of reducing the energy consumption of the heating device (solution heating device 29) without reducing the carbon dioxide recovery rate.

[0091] Although the embodiments and modifications of the present invention have been described above, the technical scope of the present invention is not limited to the above-mentioned embodiments and modifications. Various modifications of the present invention are possible without departing from the spirit of the present invention, and such modifications are also included in the technical scope of the present invention.

[0092] For example, in each of the above embodiments, the melting furnace 11 is shown as the gas generation source, but the gas generation source is not limited to the melting furnace 11. The gas generation source may be any device or facility that generates a gas containing carbon dioxide. For example, in addition to the melting furnace 11, a heat treatment device such as a carburizing furnace may be used as the gas generation source. [Explanation of symbols]

[0093] 10...carbon dioxide capture system, 11...melting furnace, 12...melting furnace control device, 13...pretreatment device, 14...pretreatment control device, 15a, 15b...carbon dioxide capture device, 16...carbon dioxide capture control device, 17...process control device, 22...carbon dioxide absorption tower, 23...carbon dioxide stripper tower, 29...solution heating device

Claims

1. a gas generation source that discharges a gas containing carbon dioxide, the gas generation source being configured such that a flow rate per unit time of the discharged gas or an amount of carbon dioxide contained in the gas is reduced while the gas generation source is in a first state compared to while the gas generation source is in a second state different from the first state; A gas generation source control device including data including information regarding a time point when the gas generation source is switched between the first state and the second state, and configured to switch the gas generation source to one of the first state and the second state based on the data; a carbon dioxide recovery apparatus including: a carbon dioxide absorption tower configured so that carbon dioxide contained in the gas discharged from the gas generation source is absorbed into a carbon dioxide absorbing solution; a carbon dioxide stripping tower configured so that carbon dioxide is stripped from the carbon dioxide absorbing solution; and a heating device configured so that the carbon dioxide absorbing solution having absorbed carbon dioxide can be heated to adjust the internal temperature of the carbon dioxide stripping tower to a temperature at which carbon dioxide is stripped from the carbon dioxide absorbing solution; a carbon dioxide capture control device that uses the data to identify a first time point that is a time point at which the gas generation source is switched from the first state to the second state, identifies a second time point that is a time point at which the gas discharged from the gas generation source at the identified first time point reaches the carbon dioxide capture device, and starts heating the carbon dioxide absorbing solution by the heating device at a third time point that is a time point earlier than the identified second time point; A carbon dioxide capture system comprising:

2. 2. The carbon dioxide capture system of claim 1, The carbon dioxide recovery control device determines the length of time between the second point in time and the third point in time depending on the difference between the internal temperature of the carbon dioxide diffusion tower when the gas generation source is switched from the first state to the second state and the temperature at which a reaction occurs in which the carbon dioxide absorbing solution diffuses carbon dioxide.

3. The carbon dioxide capture system according to claim 1 or 2, the gas generation source is a melting furnace that melts a metal material by combustion heat of a combustion burner, A carbon dioxide capture system, wherein the data is production planning data including a time point at which a metal material is melted in the melting furnace, or combustion burner control data including a temporal fluctuation in the output of the combustion burner.

4. 2. The carbon dioxide capture system of claim 1, The carbon dioxide capture control device uses the data to identify a fourth point in time at which the gas generation source switches from the second state to the first state, identifies a fifth point in time at which the gas discharged from the gas generation source at the identified fourth point in time reaches the carbon dioxide capture device, and at the identified fifth point in time, reduces the amount of heat per unit time that the heating device imparts to the carbon dioxide absorbing solution compared to the amount of heat per unit time that was imparted to the carbon dioxide absorbing solution prior to the fifth point in time.

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