Carbon dioxide recovery system and method, as well as electric furnace exhaust gas treatment facility and method

Abstract

To provide a carbon dioxide recovery system and method which can efficiently recover carbon dioxide without increasing operation cost of a facility, where an amount of carbon dioxide contained in exhaust gas largely varies, and an electric furnace exhaust gas treatment facility and method.SOLUTION: A carbon dioxide recovery system which is used in a facility for discharging exhaust gas containing carbon dioxide and recovers the carbon dioxide from the exhaust gas includes: a carbon dioxide recovery device 15; an exhaust gas measurement device 9 which is configured to be capable of continuously measuring the concentration of the carbon dioxide contained in the exhaust gas, and the volume flow rate and the temperature of the exhaust gas; and a control device 17 which is configured to be capable of controlling the carbon dioxide recovery device 15 on the basis of the amount of the carbon dioxide contained in the exhaust gas calculated from the measurement result of the exhaust gas measurement device 9.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery system and method for recovering carbon dioxide from exhaust gas discharged from a facility that discharges exhaust gas containing carbon dioxide, and an electric furnace exhaust gas treatment facility and method for treating exhaust gas from an electric furnace that melts a metal raw material by an arc generated from an electrode.

Background Art

[0002] In an electric furnace that melts a metal raw material by an arc, it is required to minimize the time and power unit as much as possible. Therefore, in order to improve the heating efficiency, a carbonaceous material is charged. These carbonaceous materials react in the furnace and become carbon monoxide or carbon dioxide and are discharged outside the electric furnace as exhaust gas. In addition, carbon monoxide and carbon dioxide are also generated by the combustion and gasification of carbon-containing substances adhering to the scrap of the metal raw material, the self-dissolution of the carbon electrode, etc.

[0003] Carbon monoxide and unburned combustible substances (hydrocarbons, etc.) in the exhaust gas are usually burned in the subsequent equipment of the electric furnace and converted into carbon dioxide. Thereafter, the exhaust gas is discharged into the atmosphere after removing harmful substances, etc. as necessary. However, in recent measures against global warming, the recovery of carbon dioxide in exhaust gas is being demanded.

[0004] As a system for recovering carbon dioxide in exhaust gas, a carbon dioxide recovery system for recovering carbon dioxide from the exhaust gas of a boiler is disclosed in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The amount of exhaust gas generated in an electric furnace and the carbon content (such as carbon monoxide and carbon dioxide) contained therein vary greatly depending on the solubility of the scrap, the blowing of carbonaceous materials and oxygen, etc. In this regard, the carbon dioxide recovery system of Patent Document 1 targets the exhaust gas of a boiler and does not assume that the amount of exhaust gas and the amount of carbon dioxide in the exhaust gas vary greatly. Therefore, when applying the one disclosed in Patent Document 1 to the exhaust gas treatment of an electric furnace, it is conceivable to construct equipment that can always treat the maximum amount of fluctuating carbon dioxide and the like. In that case, the equipment for treating the maximum amount of carbon dioxide will be operated constantly, increasing the operating cost. On the other hand, in equipment that cannot treat the maximum amount of fluctuating carbon dioxide and the like, there is a problem that carbon dioxide is released into the atmosphere.

[0007] The present invention has been made to solve such problems, and in equipment where the amount of carbon dioxide contained in the exhaust gas fluctuates greatly, a carbon dioxide recovery system and method capable of efficiently recovering carbon dioxide without increasing the operating cost of the equipment, and an electric furnace exhaust gas treatment equipment and method are provided.

Means for Solving the Problems

[0008] (1) The carbon dioxide recovery system according to one aspect of the present invention is used in equipment that discharges exhaust gas containing carbon dioxide, and is for recovering carbon dioxide from the exhaust gas, a carbon dioxide recovery device, an exhaust gas measurement device configured to be able to continuously measure the concentration of carbon dioxide contained in the exhaust gas, the volume flow rate of the exhaust gas, and the temperature, and a control device configured to be able to control the carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the exhaust gas measurement device. It is characterized by comprising the above.

[0009] (2) Further, in the device according to (1) above, the carbon dioxide recovery device includes a plurality of recovery units and a plurality of regulating valves provided corresponding to each recovery unit, the control device is configured to individually control the opening and closing states of the plurality of regulating valves based on the measurement results of the exhaust gas measurement device, so that the number of the recovery units into which the exhaust gas is introduced can be changed according to the amount of carbon dioxide contained in the exhaust gas.

[0010] (3) Further, in the device according to (1) above, the carbon dioxide recovery device includes a wet absorption device that recovers carbon dioxide by a wet absorption method, the control device is configured to control the amount of the absorbent supplied to the wet absorption device based on the measurement results of the exhaust gas measurement device, so that the amount of the absorbent supplied to the wet absorption device can be changed according to the amount of carbon dioxide contained in the exhaust gas.

[0011] (4) The electric furnace exhaust gas treatment facility according to another aspect of the present invention is for treating the exhaust gas of an electric furnace that melts a metal raw material by an arc generated from an electrode, and is characterized by including the carbon dioxide recovery system according to any one of (1) to (3) above.

[0012] (5) Further, in the device according to (4) above, a combustion chamber that burns combustible substances contained in the exhaust gas, which is disposed upstream of the carbon dioxide recovery device in the flow direction of the exhaust gas, and an electric furnace side exhaust gas duct that guides the exhaust gas from the electric furnace to the carbon dioxide recovery device via the combustion chamber are provided, and the exhaust gas measurement device includes an electric furnace side measurement device configured to be able to perform the continuous measurement on the exhaust gas flowing in the electric furnace side exhaust gas duct, and the control device is preferably configured to be able to control the carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the electric furnace side measurement device.

[0013] (6) Further, in the device according to (5) above, it is preferable that the electric furnace side measuring device is configured to be able to perform the continuous measurement at a position downstream of the combustion chamber.

[0014] (7) Further, in the device according to (5) or (6) above, the electric furnace side measuring device is configured to be able to determine whether carbon monoxide is contained in the exhaust gas in addition to the continuous measurement at a position downstream of the combustion chamber. The control device is preferably configured to be able to change at least the temperature of the combustion chamber according to the presence or absence of the carbon monoxide in the exhaust gas by controlling a fuel supply device that supplies fuel to the combustion chamber based on the measurement result of the electric furnace side measuring device.

[0015] (8) Further, in the device according to any one of (5) to (7) above, a chimney for discharging the exhaust gas treated by the carbon dioxide recovery device to the outside, a chimney side exhaust gas duct for guiding the exhaust gas from the carbon dioxide recovery device to the chimney, a chimney side measuring device configured to be able to continuously measure the concentration of at least one of carbon monoxide and carbon dioxide contained in the exhaust gas flowing in the chimney side exhaust gas duct, a connection duct for connecting between the chimney side exhaust gas duct and the electric furnace side exhaust gas duct and returning the exhaust gas from the chimney side exhaust gas duct to the upstream side of the combustion chamber in the electric furnace side exhaust gas duct, a first on-off valve provided in the connection duct, and a second on-off valve provided downstream of the connection portion of the connection duct in the chimney side exhaust gas duct. The control device is preferably configured to be able to close the second on-off valve and open the first on-off valve to return the exhaust gas from the chimney side exhaust gas duct to the electric furnace side exhaust gas duct when it is determined based on the measurement result of the chimney side measuring device that at least one of carbon monoxide and carbon dioxide is contained in the exhaust gas at a concentration equal to or higher than a threshold value.

[0016] (9) A carbon dioxide recovery method according to another aspect of the present invention is a carbon dioxide recovery method used in a facility that discharges exhaust gas containing carbon dioxide, and for recovering carbon dioxide from the exhaust gas, comprising: continuously measuring the concentration of carbon dioxide contained in the exhaust gas, as well as the volume flow rate and temperature of the exhaust gas; and controlling a carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the continuous measurement.

[0017] (10) Further, in the method described in (9) above, the carbon dioxide recovery device includes a plurality of recovery units and a plurality of regulating valves provided corresponding to each recovery unit, individually controlling the opening and closing states of the plurality of regulating valves based on the measurement results of the continuous measurement; and preferably changing the number of the recovery units into which the exhaust gas is introduced according to the amount of carbon dioxide contained in the exhaust gas.

[0018] (11) Further, in the method described in (9) above, the carbon dioxide recovery device includes a wet absorption device for recovering carbon dioxide by a wet absorption method, controlling the amount of the absorbent supplied to the wet absorption device based on the measurement results of the continuous measurement; and preferably changing the amount of the absorbent supplied to the wet absorption device according to the amount of carbon dioxide contained in the exhaust gas.

[0019] (12) An electric furnace exhaust gas treatment method according to another aspect of the present invention is an electric furnace exhaust gas treatment method for treating the exhaust gas of an electric furnace that melts a metal raw material by an arc generated from an electrode, comprising: including the carbon dioxide recovery method described in any one of (9) to (11) above.

Advantages of the Invention

[0020] According to the present invention, since the carbon dioxide recovery device is controlled based on the amount of carbon dioxide contained in the exhaust gas, in a facility where the amount of carbon dioxide contained in the exhaust gas fluctuates greatly, it is possible to provide a carbon dioxide recovery system and method capable of efficiently recovering carbon dioxide without increasing the operating cost of the facility, as well as an electric furnace exhaust gas treatment facility and method.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0022] [Embodiment 1] The electric furnace exhaust gas treatment facility 1 according to the present embodiment is for treating the exhaust gas of the electric furnace 3 as shown in FIG. 1, and includes an electric furnace side exhaust gas duct 5, a combustion chamber 7, an electric furnace side measuring device 9, a cooling device 11, a dust collecting device 13, a carbon dioxide recovery device 15, a control device 17, and a chimney side exhaust gas duct 19. That is, the present embodiment is an electric furnace exhaust gas treatment facility provided with a carbon dioxide recovery system according to an embodiment of the present invention, and the electric furnace side measuring device 9 functions as an exhaust gas measuring device of the carbon dioxide recovery system of the present embodiment. Hereinafter, each component will be described in detail.

[0023] [Electric Furnace] The electric furnace 3 is a furnace that melts metal raw materials by the arc generated from the electrodes.

[0024] <Electric furnace side exhaust gas duct> The electric furnace side exhaust gas duct 5 guides the exhaust gas discharged from the electric furnace 3 to the carbon dioxide recovery device 15 via the combustion chamber 7, the cooling device 11, and the dust collection device 13.

[0025] <Combustion chamber> The combustion chamber 7 is arranged upstream of the carbon dioxide recovery device 15 in the flow direction of the exhaust gas, and burns combustible substances such as oil contained in the exhaust gas.

[0026] <Electric furnace side measuring device> The electric furnace side measuring device 9 is configured to be able to continuously measure the concentration of carbon dioxide contained in the exhaust gas flowing in the electric furnace side exhaust gas duct 5, as well as the volume flow rate and temperature of the exhaust gas. In this embodiment, it is arranged downstream of the combustion chamber 7 in the flow direction of the exhaust gas.

[0027] Such an electric furnace side measuring device 9 can be composed of a gas component measuring device that measures the concentration of carbon dioxide in the exhaust gas, a flow meter that measures the exhaust gas volume flow rate, and a thermometer using a thermocouple that measures the temperature of the exhaust gas.

[0028] As the gas component measuring device, for example, the gas component measuring device disclosed in Japanese Patent No. 6496341 can be applied. This gas component measuring device includes a cyclone device provided with a gas inlet, and a laser gas analyzer that measures the components of the target gas containing particulate matter introduced into the cyclone device from the gas inlet in the cyclone device. Even for a gas containing a large amount of dust, its components can be measured quickly and continuously.

[0029] By arranging the electric furnace side measuring device 9 on the downstream side of the combustion chamber 7, it is possible to measure after the combustion of unburned combustible substances (such as hydrocarbons) like oil content which is difficult to measure online (continuously) has ended, and the amount of carbon contained in the exhaust gas can be grasped more accurately. Also, by arranging it on the downstream side of the combustion chamber 7, the analysis target becomes only carbon dioxide, which also leads to a reduction in running costs. However, when the correlation between the carbon amounts before and after combustion is known, measurement may be performed on the exhaust gas before introduction into the combustion chamber 7.

[0030] The electric furnace side measuring device 9 is configured to be able to continuously measure the concentration of carbon dioxide contained in the exhaust gas, as well as the volume flow rate and temperature of the exhaust gas. Based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the electric furnace side measuring device 9 by the control device described later, the carbon dioxide recovery device 15 is controlled. Therefore, in an electric furnace facility where the amount of carbon dioxide contained in the exhaust gas varies greatly, efficient recovery of carbon dioxide can be achieved without increasing the operation cost of the facility. Note that the measurement location by the electric furnace side measuring device 9 is more preferably the downstream side of the dust collecting device 13 after dust has been collected.

[0031] <Cooling device> The cooling device 11 is, for example, a device that cools the exhaust gas by exchanging heat between the exhaust gas and cooling water.

[0032] <Dust collecting device> The dust collecting device 13 is a device that recovers solid components (dust) contained in the exhaust gas. For example, it recovers the solid components (dust) by filtering the exhaust gas with a filter.

[0033] <Carbon dioxide recovery device> The carbon dioxide recovery device 15 recovers carbon dioxide from the gas to be treated. In this embodiment, as shown in FIG. 1, the carbon dioxide recovery device 15 includes a plurality (three in this example) of recovery units 21 that separate and recover carbon dioxide, and a plurality of control valves 23 provided corresponding to each recovery unit 21.

[0034] As the carbon dioxide separation method, an optimal method may be selected or combined from chemical absorption methods (methods of chemically absorbing CO2 into an absorbent using a solvent such as an amine), solid absorption methods (methods of absorbing CO2 into a solid absorbent and separating it), physical adsorption methods (methods of adsorbing CO2 onto a solid adsorbent such as activated carbon), membrane separation methods (methods of separating using a membrane through which CO2 selectively permeates), etc. and used.

[0035] In this embodiment, as will be described later, the opening degree of each control valve 23 is adjusted by the control device 17, and the amount of exhaust gas supplied to each recovery unit 21 is adjusted.

[0036] <Control device> The control device 17 controls the carbon dioxide recovery device 15 based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the electric furnace side measuring device 9. Specifically, the control device 17 performs the following control. The control device 17 inputs the measurement results of the concentration of carbon dioxide contained in the exhaust gas flowing in the electric furnace side exhaust gas duct 5, the volume flow rate of the exhaust gas, and the temperature from the electric furnace side measuring device 9, and calculates the amount of carbon dioxide based on these. Then, it determines the recovery unit 21 necessary to process the calculated amount of carbon dioxide, and controls the control valve 23 provided corresponding to the determined recovery unit 21.

[0037] The calculation of the amount of carbon dioxide based on the measurement results of the electric furnace side measuring device 9 can be performed using the following formula. The molar emission amount M (mol / s) of carbon dioxide (CO2) per unit time is such that the molecular volume at 0°C and standard atmospheric pressure of an ideal gas = 0.0224 (m 3 / mol), therefore, M (mol / s) = K × C / 10 6×T / (273 + T) × P / 0.1013 × F / 0.0224 becomes However, K: coefficient C: Carbon dioxide concentration in the exhaust gas (ppm = 1 / 10 6 ) T: Exhaust gas temperature (°C) F: Exhaust gas flow rate (m 3 / s) P: Exhaust gas pressure (MPa) Therefore, the mass emission rate of carbon dioxide W (kg / s) is W (kg / s) = M / 0.044 (CO2: 44 g / mol) becomes

[0038] The coefficient K is a correction coefficient. By comparing the assumed weight of carbon dioxide calculated from the measurement results of the components, concentration, flow rate, etc. of the exhaust gas with the amount of carbon dioxide actually recovered by the recovery unit 21, and correcting the value of the coefficient K to make them match when there are differences between them, the calculation accuracy of the amount of carbon dioxide can be improved. Since the term related to pressure has no significant numerical difference compared to atmospheric pressure, it can be omitted and set to 1. However, when performing more accurate calculations, the value obtained from exhaust gas measurement and calculation can be used. When using the measured value for the pressure value, the electric furnace side measurement device 9 may be further equipped with a pressure gauge for measuring the pressure of the exhaust gas.

[0039] <Stack side exhaust gas duct> The stack side exhaust gas duct 19 is for guiding the exhaust gas after recovering the carbon dioxide discharged from the carbon dioxide recovery device 15 to the stack 25, and a blower 26 is provided in the stack side exhaust gas duct 19.

[0040] An example of the operation pattern of the electric furnace exhaust gas treatment facility 1 configured as described above will be described based on FIG. 2. FIG. 2 is a graph showing the relationship between the equipment operation time, the operation status of the carbon dioxide recovery device, and the amount of carbon dioxide. The horizontal axis in Fig. 2 represents the operation time of the facility, and the vertical axis represents the operation status of the carbon dioxide recovery device and the amount of carbon dioxide, respectively. Here, the operation status of the carbon dioxide recovery device means that the status where one of the three recovery units 21 is operating is regarded as 100%, the status where two units are operating is 200%, and the status where three units are operating is 300%. In other words, the vertical axis shows the amount of carbon dioxide generated normalized by the processing capacity of the recovery unit 21. Also, the curve in the figure shows the amount of carbon dioxide contained in the exhaust gas calculated from the results of continuous measurement by the electric furnace side measuring device 9, and the straight line of the arrow in the figure shows the operation pattern of the carbon dioxide recovery device.

[0041] As shown in Fig. 2, from the start of operation to the operation time t1, the amount of carbon dioxide is less than the amount that can be processed by one of the recovery units 21, that is, less than 100% shown on the vertical axis in the figure. Therefore, one of the recovery units 21 (recovery unit #1 in the figure) is operating. In other words, by the control of the control device 17, the opening / closing state of the regulating valve 23 corresponding to the recovery unit #1 is in the open state, and the opening / closing states of the regulating valves 23 corresponding to the recovery units #2 and 3 are in the closed state.

[0042] When the operation time reaches t1, since the amount of carbon dioxide exceeds 100%, the second recovery unit 21 (recovery unit #2 in the figure) starts operating. In other words, by the control of the control device 17, the opening / closing state of the regulating valve 23 corresponding to the recovery unit #2 is in the open state. During the operation time t1 to t2, since the amount of carbon dioxide is between 100% and 200%, two recovery units 21 (recovery units #1 and #2) are operating. In other words, by the control of the control device 17, the opening / closing states of the regulating valves 23 corresponding to the recovery units #1 and #2 are in the open state, and the opening / closing state of the regulating valve 23 corresponding to the recovery unit #3 is in the closed state. When the operation time reaches t2, since the amount of carbon dioxide falls below 100%, the recovery unit #2 stops operating and only the recovery unit #1 operates. In other words, by the control of the control device 17, the opening / closing state of the regulating valve 23 corresponding to the recovery unit #2 is in the closed state.

[0043] When the operation time reaches t3, the amount of carbon dioxide exceeds 100%, so the recovery unit #2 starts operating again. When the operation time further reaches t4, the amount of carbon dioxide exceeds 200%, so the third recovery unit 21 (recovery unit #3) starts operating. In other words, at the time point of t3, due to the control by the control device 17, the opening / closing state of the control valve 23 corresponding to the recovery unit #2 is set to the open state. At the time point of t4, due to the control by the control device 17, the opening / closing state of the control valve 23 corresponding to the recovery unit #3 is further set to the open state. When the operation time reaches t5, the amount of carbon dioxide is less than 200%, so the recovery unit #3 stops. Furthermore, when the operation time reaches t6, the amount of carbon dioxide is less than 100%, so the recovery unit #2 stops. After that, since the amount of carbon dioxide is 100% or less, only the recovery unit #1 operates. In other words, at the time point of t5, due to the control by the control device 17, the opening / closing state of the control valve 23 corresponding to the recovery unit #3 is set to the closed state. At the time point of t6, due to the control by the control device 17, the opening / closing state of the control valve 23 corresponding to the recovery unit #2 is further set to the closed state.

[0044] As described above, in the electric furnace exhaust gas treatment facility 1, during the operation of the electric furnace 3, the exhaust gas is continuously measured by the electric furnace side measuring device 9, and the exhaust gas is supplied to the required recovery unit 21 by the control device 17 for carbon dioxide recovery. Therefore, according to the present embodiment, by the efficient operation of the recovery unit 21, efficient recovery of carbon dioxide can be achieved while suppressing the operation cost.

[0045] More specifically, in the carbon dioxide recovery device, the processing capacity of a single device is limited. In a facility where the amount of carbon dioxide contained in the exhaust gas fluctuates greatly, in order to provide a recovery device that covers the entire range of fluctuations, it is necessary to use a recovery device that matches the maximum emission amount. During periods when the carbon dioxide emission amount is small, a considerably large portion of its capacity becomes wasted. However, as in this embodiment, the carbon dioxide recovery device 15 includes a plurality of recovery units 21 and a plurality of regulating valves 23 provided corresponding to each recovery unit 21. The control device 17 individually controls the opening and closing states of the plurality of regulating valves 23 based on the measurement results of the electric furnace side measuring device 9, so that the number of recovery units 21 into which the exhaust gas is introduced can be changed according to the amount of carbon dioxide contained in the exhaust gas. By being configured in this way, the processing capacity of each recovery unit 21 can be effectively utilized, the operating cost can be suppressed, and efficient recovery of carbon dioxide can be achieved.

[0046] As described above, as a carbon dioxide separation method, a chemical absorption method, a solid absorption method, a physical adsorption method, a membrane separation method, etc. are applicable. However, when it is assumed that the carbon dioxide concentration in the exhaust gas exceeds an appropriate concentration that can be processed, air may be mixed into the exhaust gas introduced into each recovery unit 21 to dilute the carbon dioxide concentration. Specifically, as in the modified example shown in FIG. 3, an air introduction duct 27 and an air regulating valve 29 are provided. When the carbon dioxide concentration exceeds the appropriate concentration based on the measurement results of the electric furnace side measuring device 9, the control device 17 may open the air regulating valve 29. Such a configuration is also applicable in Embodiments 2 to 4 described later.

[0047] [Embodiment 2] FIG. 4 is an explanatory diagram of the electric furnace exhaust gas treatment facility 31 according to Embodiment 2. The electric furnace exhaust gas treatment facility 31 of the present embodiment is the same as that of Embodiment 1 except that the recovery unit 21 described in Embodiment 1 is constituted by a wet absorption device 33. The wet absorption device 33 includes an absorption tower 37 provided with an injection nozzle 35 for injecting an absorbent that absorbs carbon dioxide, a CO2 recovery and concentration device 39 for recovering and concentrating the absorbent that has absorbed CO2, and an absorbent amount adjustment valve 41 provided in the supply pipe of the absorbent for adjusting the amount of the absorbent supplied to the injection nozzle 35.

[0048] The control device 17 adjusts the amount of the absorbent supplied to the wet absorption device 33 by controlling the absorbent amount adjustment valve 41 based on the measurement result of the electric furnace side measuring device 9. Thereby, the amount of the absorbent supplied to the wet absorption device 33 can be changed according to the amount of carbon dioxide. The absorbent that has absorbed carbon dioxide is recovered and concentrated in the CO2 recovery and concentration device 39, further liquefied and solidified, and externally carried out by a tank truck 43 or the like.

[0049] According to the present embodiment, not only the number of the recovery unit 21, that is, the wet absorption device 33, but also the amount of the absorbent of each wet absorption device 33 can be adjusted according to the amount of carbon dioxide contained in the exhaust gas, so that more efficient operation is possible.

[0050] In addition, although the above description has been made on the premise that there are a plurality of wet absorption devices 33, even when there is one wet absorption device 33, if the amount of the absorbent can be adjusted according to the amount of carbon dioxide contained in the exhaust gas, efficient operation is possible. In FIG. 4, an example of externally carrying out the absorbent that has absorbed carbon dioxide in a liquefied and solidified state after recovery and concentration is shown, but after concentration, treatment such as methanation may be performed within the site.

[0051] [Embodiment 3] The electric furnace exhaust gas treatment facility 45 of the present embodiment shown in Fig. 5 is the same as that of the first embodiment except that the electric furnace side measuring device 9 is configured to be able to determine whether carbon monoxide is contained in the exhaust gas in addition to the above continuous measurement at a position downstream of the combustion chamber 7. That is, as shown in Fig. 5, the electric furnace exhaust gas treatment facility 45 of the present embodiment is configured such that the electric furnace side measuring device 9 can determine whether carbon monoxide is contained in the exhaust gas, and the control device 17 controls the fuel supply device 47 that supplies fuel to the combustion chamber 7 according to the presence or absence of carbon monoxide in the exhaust gas, which is the measurement result of the electric furnace side measuring device 9, so that at least the temperature of the combustion chamber 7 can be changed according to the presence or absence of carbon monoxide in the exhaust gas.

[0052] When carbon monoxide is contained in the exhaust gas, it indicates that the remaining amount of unburned substances is large. In this case, for example, the fuel supplied to the combustion chamber 7 may be increased to raise the temperature of the combustion chamber 7. Also, according to the gas concentration distribution in the furnace, the fuel supplied to the burner at a specific position may be increased.

[0053] According to the present embodiment, the combustible substances contained in the exhaust gas in the combustion chamber 7 can be surely and efficiently burned.

[0054] The configuration added in the aspect of the present embodiment is also applicable to the second and fourth embodiments.

[0055] [Embodiment 4] As shown in Fig. 6, the electric furnace exhaust gas treatment facility 49 of this embodiment is configured to be able to continuously measure the concentration of at least one of carbon monoxide and carbon dioxide contained in the exhaust gas flowing in the chimney-side exhaust gas duct 19. It is the same as Embodiment 2 described with reference to Fig. 4, except that it further includes a chimney-side measuring device 51, a connection duct 53 that connects between the chimney-side exhaust gas duct 19 and the electric furnace-side exhaust gas duct 5 to return the exhaust gas from the chimney-side exhaust gas duct 19 to the upstream side of the combustion chamber 7 in the electric furnace-side exhaust gas duct 5, a first on-off valve 55 provided in the connection duct 53, and a second on-off valve 57 provided on the downstream side of the connection portion of the connection duct 53 in the chimney-side exhaust gas duct 19.

[0056] When the control device 17 determines based on the measurement result of the chimney-side measuring device 51 that at least one of carbon monoxide and carbon dioxide is contained in the exhaust gas at a concentration equal to or higher than the threshold value, it controls to close the second on-off valve 57 and open the first on-off valve 55. As a result, the exhaust gas containing carbon monoxide or carbon dioxide at a concentration equal to or higher than the threshold value is returned to the upstream side of the combustion chamber 7 in the electric furnace-side exhaust gas duct 5 and burned again in the combustion chamber 7.

[0057] When the exhaust gas flowing in the chimney-side exhaust gas duct 19 contains carbon monoxide, by returning this exhaust gas to the upstream side of the combustion chamber 7 and burning it, the carbon in the exhaust gas can be more reliably recovered as carbon dioxide. Also, when the exhaust gas flowing in the chimney-side exhaust gas duct 19 contains carbon dioxide, by returning this exhaust gas to the upstream side of the combustion chamber 7 and processing it again with the carbon dioxide recovery device 15, carbon dioxide can be more reliably recovered.

[0058] The configuration added in this embodiment is also applicable to Embodiments 1 and 3.

[0059] Although the present invention has been described using the embodiments above, the present invention is not limited to the configurations of these embodiments. The scope of the present invention is determined based on the description in the appended claims, and within that scope, all omissions, modifications, or improvements of some of the components shown in the embodiments are included in the present invention.

[0060] For example, in the above description, the control valve 23 is shown in a form that can adjust the opening degree by the control device 17, but the control valve 23 may be a valve that simply opens and closes the flow path by the control of the control device 17.

[0061] Also, in the above description, an example of adjusting the number of multiple recovery units 21 included in the carbon dioxide recovery device 15 arranged in parallel is shown, but a plurality of recovery units included in the carbon dioxide recovery device 15 may be arranged in series, and based on the amount of carbon dioxide calculated from the measurement result of the electric furnace side measuring device 9 and the capacity of each recovery unit 21, etc., the number of units to be used may be determined. In the case of series arrangement, for example, when the amount of carbon dioxide contained is more than the recovery capacity of the most upstream recovery unit, what could not be recovered by the most upstream recovery unit will be recovered by the downstream recovery unit. And a bypass duct leading to the downstream side of the carbon dioxide recovery device 15 is provided on the downstream side of each recovery unit, control valves are provided on the upstream side of each recovery unit and the bypass duct, and by controlling the opening and closing of the control valves on the downstream side of the required number of recovery units, the exhaust gas that has passed through the required number of recovery units is discharged from the chimney.

[0062] Also, the above embodiments show the case where the carbon dioxide recovery system of the present invention is used in an exhaust gas treatment facility for an electric furnace, which is a facility that discharges exhaust gas containing carbon dioxide and the amount of carbon dioxide contained in the exhaust gas fluctuates greatly. However, the carbon dioxide recovery system of the present invention is not limited to these forms. For example, it can also be suitably used in an exhaust gas treatment facility for a parallel flow regenerative lime calcining furnace that alternately performs heat storage and combustion in two shafts.

Explanation of Reference Numerals

[0063] 1 Electric furnace gas treatment equipment (Embodiment 1) 3 Electric furnace 5 Electric furnace side exhaust gas duct 7 Combustion chamber 9 Electric furnace side measuring device 11 Cooling device 13 Dust collecting device 15 Carbon dioxide recovery device 17 Control device 19 Chimney side exhaust gas duct 21 Recovery unit 23 Control valve 25 Chimney 26 Blower 27 Atmosphere introduction duct 29 Atmosphere control valve 31 Electric furnace gas treatment equipment (Embodiment 2) 33 Wet absorption device 35 Injection nozzle 37 Absorption tower 39 CO2 recovery and concentration device 41 Absorbent amount control valve 43 Tank lorry 45 Electric furnace gas treatment equipment (Embodiment 3) 47 Fuel supply device 49 Electric furnace gas treatment equipment (Embodiment 4) 51 Chimney side measuring device 53 Connection duct 55 First on-off valve 57 Second on-off valve

Claims

1. A carbon dioxide recovery system used in a facility that discharges exhaust gas containing carbon dioxide and recovers carbon dioxide from the exhaust gas, comprising: A carbon dioxide recovery device; An exhaust gas measurement device configured to be able to continuously measure the concentration of carbon dioxide contained in the exhaust gas, as well as the volume flow rate and temperature of the exhaust gas; A control device configured to be able to control the carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the exhaust gas measurement device; A carbon dioxide recovery system, characterized by comprising the above.

2. The carbon dioxide recovery device includes a plurality of recovery units and a plurality of regulating valves provided corresponding to each recovery unit, The control device is configured to individually control the opening and closing states of the plurality of regulating valves based on the measurement results of the exhaust gas measurement device, so that the number of recovery units into which the exhaust gas is introduced can be changed according to the amount of carbon dioxide contained in the exhaust gas. The carbon dioxide recovery system according to claim 1, characterized in that it is configured as such.

3. The carbon dioxide recovery device includes a wet absorption device that recovers carbon dioxide by a wet absorption method, The control device is configured to control the amount of absorbent supplied to the wet absorption device based on the measurement results of the exhaust gas measurement device, so that the amount of absorbent supplied to the wet absorption device can be changed according to the amount of carbon dioxide contained in the exhaust gas. The carbon dioxide recovery system according to claim 1, characterized in that it is configured as such.

4. An electric furnace exhaust gas treatment facility for treating the exhaust gas of an electric furnace that melts a metal raw material by an arc generated from an electrode, comprising: An electric furnace exhaust gas treatment facility, characterized by comprising the carbon dioxide recovery system according to any one of claims 1 to 3.

5. A combustion chamber disposed upstream of the carbon dioxide recovery device in the flow direction of the exhaust gas for burning combustible substances contained in the exhaust gas; An electric furnace side exhaust gas duct for guiding the exhaust gas from the electric furnace to the carbon dioxide recovery device via the combustion chamber; Comprising; The exhaust gas measuring device includes an electric furnace side measuring device configured to be able to perform the continuous measurement on the exhaust gas flowing in the electric furnace side exhaust gas duct; The control device is configured to be able to control the carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement result of the electric furnace side measuring device. The electric furnace exhaust gas treatment facility according to claim 4.

6. The electric furnace side measuring device is configured to be able to perform the continuous measurement at a position downstream of the combustion chamber. The electric furnace exhaust gas treatment facility according to claim 5.

7. The electric furnace side measuring device is configured to be able to determine whether carbon monoxide is contained in the exhaust gas in addition to the continuous measurement at a position downstream of the combustion chamber; The control device controls a fuel supply device that supplies fuel to the combustion chamber based on the measurement result of the electric furnace side measuring device, so that at least the temperature of the combustion chamber can be changed according to the presence or absence of the carbon monoxide in the exhaust gas. The electric furnace exhaust gas treatment facility according to claim 5.

8. A chimney for discharging the exhaust gas treated by the carbon dioxide recovery device to the outside; A chimney side exhaust gas duct for guiding the exhaust gas from the carbon dioxide recovery device to the chimney; A chimney side measuring device configured to be able to perform continuous measurement of the concentration of at least one of carbon monoxide and carbon dioxide contained in the exhaust gas flowing in the chimney side exhaust gas duct; A connection duct that connects between the chimney-side exhaust gas duct and the electric furnace-side exhaust gas duct and returns the exhaust gas from the chimney-side exhaust gas duct to the upstream side of the combustion chamber in the electric furnace-side exhaust gas duct, a first on-off valve provided in the connection duct, and a second on-off valve provided on the downstream side of the connection portion between the connection duct and the chimney-side exhaust gas duct are further provided. The control device is configured to close the second on-off valve and open the first on-off valve to return the exhaust gas from the chimney-side exhaust gas duct to the electric furnace-side exhaust gas duct when it is determined based on the measurement result of the chimney-side measuring device that at least one of carbon monoxide and carbon dioxide is contained in the exhaust gas at a concentration equal to or higher than a threshold value. The electric furnace exhaust gas treatment facility according to claim 5, characterized in that.

9. A carbon dioxide recovery method used in a facility for discharging exhaust gas containing carbon dioxide, the method for recovering carbon dioxide from the exhaust gas, Performing continuous measurement of the concentration of carbon dioxide contained in the exhaust gas, the volume flow rate of the exhaust gas, and the temperature, Controlling a carbon dioxide recovery device based on the amount of carbon dioxide contained in the exhaust gas calculated from the measurement results of the continuous measurement. A carbon dioxide recovery method characterized by including.

10. The carbon dioxide recovery device includes a plurality of recovery units and a plurality of adjustment valves provided corresponding to each recovery unit. Individually controlling the opening and closing states of the plurality of adjustment valves based on the measurement results of the continuous measurement, Changing the number of the recovery units into which the exhaust gas is introduced according to the amount of carbon dioxide contained in the exhaust gas. The carbon dioxide recovery method according to claim 9, characterized by including.

11. The carbon dioxide recovery device includes a wet absorption device that recovers carbon dioxide by a wet absorption method. Controlling the amount of the absorbent supplied to the wet absorption device based on the measurement results of the continuous measurement. The carbon dioxide recovery method according to claim 9, comprising changing the amount of the absorbent supplied to the wet absorption device according to the amount of carbon dioxide contained in the exhaust gas.

12. An electric furnace exhaust gas treatment method for treating the exhaust gas of an electric furnace that melts a metal raw material by an arc generated from an electrode, comprising: An electric furnace exhaust gas treatment method characterized by including the carbon dioxide recovery method according to any one of claims 9 to 11.

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