Combustion exhaust gas pretreatment equipment and pretreatment method

Abstract

This method suppresses the generation of condensate during the temperature reduction process when supplying combustion exhaust gas to a CO2 separation and recovery system, while preventing a decrease in the recovery efficiency of carbon dioxide in downstream equipment and avoiding the need for equipment expansion. [Solution] In a facility having a combustion device and a CO2 separation and recovery device 50, a water vapor separation device 20 equipped with a water vapor separation membrane for separating water from the combustion exhaust gas before introducing the water-containing combustion exhaust gas into the CO2 separation and recovery device 50, and a gas cooling device 30 for cooling the combustion exhaust gas from which the water has been reduced by the water vapor separation device 20 are provided in front of the CO2 separation and recovery device 50.

Description

Technical Field

[0001] The present invention relates to a pretreatment facility and method for combustion exhaust gas, and particularly to a pretreatment facility and method for combustion exhaust gas capable of reducing the amount of condensed water generated when supplying combustion exhaust gas having a moisture content of about 20% to a CO2 separation and recovery device.

Background Art

[0002] In facilities having combustion devices such as coal-fired power generation facilities, waste combustion treatment facilities, and biomass power generation facilities, the temperature of the exhaust gas generated by combustion is often 100°C or higher and has a predetermined moisture content. For example, the exhaust gas of a waste incineration facility often has a temperature of 160°C and a moisture content of about 20%.

[0003] In addition, the exhaust gas contains a predetermined amount of carbon dioxide, and the content rate is about 8 to 14%. Recently, the separation, recovery, and utilization of carbon dioxide from combustion exhaust gas have attracted attention for suppressing global warming.

[0004] Currently, for the carbon dioxide separation and recovery method that has been put into practical use, it is desirable from the viewpoints of efficient carbon dioxide separation and recovery and equipment protection to make the temperature of the exhaust gas introduced into the equipment generally 40°C or lower. Therefore, it is necessary to cool the exhaust gas at 100°C or higher to 40°C or lower.

[0005] As means for cooling the exhaust gas, a method of directly contacting the exhaust gas with cooling water for cooling and a method of indirectly cooling the pipe through which the exhaust gas flows from the outside are known. However, in both methods, since the amount of saturated water vapor in the gas decreases due to the temperature of the water vapor in the exhaust gas at 100°C or higher being cooled to 40°C or lower, as the temperature of the gas decreases, the moisture exceeding the amount of saturated water vapor becomes condensed water.

[0006] This condensed water comes into contact with trace amounts of acidic gases contained in the exhaust gas and dissolves, resulting in an acidic pH, so a separate wastewater treatment facility is required, increasing the installation cost and running cost of the wastewater treatment facility.

[0007] Furthermore, many waste incineration facilities employ a closed-loop wastewater system that does not discharge liquid water outside the facility. Instead, wastewater is introduced into the incinerator or exhaust gas treatment equipment to evaporate, and then discharged outside the system as water vapor in the exhaust gas, with the aim of reducing the exhaust gas temperature.

[0008] On the other hand, the amount of condensate generated when lowering the exhaust gas temperature as a pretreatment for the CO2 separation and recovery equipment exceeds the amount of wastewater required for the predetermined temperature adjustment. As a result, the generation of condensate prevents the aforementioned closed wastewater system from functioning, which is undesirable.

[0009] Therefore, a method like the one shown in Patent Document 1 has been proposed. In this method, in addition to a heat exchanger for reducing the temperature of the exhaust gas after it has passed through the acid gas removal equipment, a predetermined amount of air is added to adjust the gas volume and temperature to a range where water vapor in the reduced-temperature exhaust gas does not condense, thereby achieving temperature reduction. This is achieved by adding a device / process for heat exchange and air addition to the equipment configuration. Unlike the method of directly contacting the exhaust gas with cooling water, this method does not generate wastewater, eliminating the need for wastewater treatment equipment, and allowing the maintenance of a closed wastewater system.

[0010] Furthermore, another technique for reducing moisture is to use a desiccant such as silica gel. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2023-17690 [Patent Document 2] Patent No. 7490186 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] However, in the method proposed in Patent Document 1, the carbon dioxide concentration in the exhaust gas decreases as a result of adding air, thus reducing the carbon dioxide recovery efficiency. Furthermore, in order to install equipment that adds air while maintaining carbon dioxide recovery efficiency, the carbon dioxide separation and recovery equipment must be made larger, leading to increased installation costs and space requirements, thus creating new problems.

[0013] Furthermore, using a desiccant such as silica gel generates water during its regeneration process, requiring equipment to recover the water by heating, which is undesirable.

[0014] Furthermore, steam separation technology using steam separation membranes has already been used in thermal power plants and the like, for example, as described in Patent Document 2, to separate steam from exhaust gas after it has passed through a turbine and to effectively utilize the latent heat of steam.

[0015] However, using latent heat, as in the technology described in Patent Document 2, results in the generation of condensed water, which defeats the purpose.

[0016] The present invention aims to solve the aforementioned problems of the conventional approach and provides a combustion exhaust gas pretreatment facility and pretreatment method that can suppress the generation of condensate while preventing a decrease in the recovery efficiency of carbon dioxide recovery in downstream equipment and the expansion of equipment. [Means for solving the problem]

[0017] The present invention solves the above problem by providing a pretreatment system for combustion exhaust gas, characterized in that, in a facility having a combustion device and a CO2 separation and recovery device, the system comprises a water vapor separation device equipped with a water vapor separation membrane for separating water from combustion exhaust gas containing water before introducing the combustion exhaust gas into the CO2 separation and recovery device, and a gas cooling device for cooling the combustion exhaust gas from which the water has been reduced by the water vapor separation device.

[0018] Here, piping can be provided to return the water vapor separated by the water vapor separation device back to the facility's flue.

[0019] Furthermore, a condensation prevention means for preventing condensation of the water vapor separated by the water vapor separation device can be provided.

[0020] Furthermore, the condensation prevention means can be provided in the water vapor separation device or the piping.

[0021] Furthermore, the condensation prevention means can be the heat insulation or heating means provided in the water vapor separation device or the piping.

[0022] Furthermore, the heat insulation or heating means can be provided with a gas thermometer or a gas moisture rate analyzer and have a temperature control mechanism for preventing condensation of water vapor in the gas or acid dew point corrosion.

[0023] Furthermore, the temperature of the water vapor separation membrane device can be controlled to 120°C or higher.

[0024] Furthermore, in order to prevent the generation of condensed water due to condensation of the water vapor separated by the water vapor separation device, the temperature control or temperature and humidity monitoring of the water vapor separation device can be performed.

[0025] Furthermore, in order to prevent corrosion of equipment caused by the temperature of the acidic gas contained in trace amounts in the water vapor separated by the water vapor separation device falling below the acid dew point and generating a highly corrosive solution, temperature control can be performed to maintain the inside of the water vapor separation device at 120°C or higher.

[0026] That is, by providing means for heat-insulating or heating the water vapor separation membrane device and its peripheral piping as needed and providing a mechanism for controlling it within a predetermined temperature range, it is possible to avoid as much as possible the water vapor in the exhaust gas from cooling and becoming condensed water. Also, even at 100°C or higher, if the temperature is below the acid dew point temperature at which the acidic gas component condenses, the acidic gas component may liquefy inside the equipment and the corrosion of the equipment may progress. However, such corrosion problems can also be avoided. Furthermore, it is preferable that the water vapor remains in the gas phase and is returned to the exhaust gas flue and discharged from the chimney.

Advantages of the Invention

[0027] According to the present invention, when a water vapor separation membrane is used for a different purpose from that in Patent Document 2, that is, when combustion exhaust gas containing moisture is cooled by a gas cooling device and then inserted into a CO2 separation and recovery device, a water vapor separation device is inserted in the front stage of the gas cooling device, so that the moisture in the combustion exhaust gas can be reduced before the cooling treatment. As a result, even if the gas is cooled to, for example, 40°C or lower in the gas cooling device, the generation of condensed water can be prevented or the amount of generation can be reduced. That is, it is possible to reduce and suppress the amount of drainage and suppress the drainage treatment cost.

Brief Description of the Drawings

[0028] [Figure 1] Configuration diagram showing the overall configuration of the first embodiment of the present invention [Figure 2] Front view (A) and side view (B) showing the configuration of the water vapor separation device used in the first embodiment [Figure 3] Perspective view showing a water vapor separation membrane tube as well [Figure 4] Cross-sectional view showing the configuration of the gas cooling device as well [Figure 5] Configuration diagram showing the overall configuration of the second embodiment of the present invention [Figure 6] Configuration diagram showing the overall configuration of the third embodiment of the present invention [Figure 7] Configuration diagram showing the overall configuration of the fourth embodiment of the present invention [Figure 8] Configuration diagram showing the overall configuration of the fifth embodiment of the present invention

Modes for Carrying Out the Invention

[0029] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the content described in the following embodiments. In addition, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments may be combined as appropriate or may be appropriately selected and used.

[0030] In a first embodiment of the present invention, as shown in Figure 1, in a factory 10 equipped with a combustion device and a CO2 separation and recovery device 50, a water vapor separation membrane unit 20 equipped with a water vapor separation membrane for separating water from the combustion exhaust gas and a gas cooling device 30 for cooling the combustion exhaust gas from which the water has been reduced by the water vapor separation membrane unit 20 are provided upstream of the CO2 separation and recovery device 50 before introducing the combustion exhaust gas containing water into the CO2 separation and recovery device 50.

[0031] In Figure 1, 12 is a flue for guiding the combustion exhaust gas discharged from the factory 10 to the chimney 14.

[0032] As shown in Figure 2(A) front view and (B) side view, the water vapor separation membrane unit 20 has an internal water vapor separation membrane tube 22 made of, for example, an organosilica membrane, as shown in Figure 3. The water vapor from the combustion exhaust gas introduced into the water vapor separation membrane tube 22 (left side in Figure 3) is separated, and the dried exhaust gas is discharged from the opposite side (right side in Figure 3).

[0033] In Figure 2, 24 is the outlet for the separated steam, and 26 is a flange bolt hole. The steam separation membrane unit 20 is wrapped in insulating material 28, and the inlet piping 16 of the steam separation membrane unit 20 is also wrapped in insulating material 17, as shown in Figure 1.

[0034] As shown in Figure 4, the gas cooling device 30 allows, for example, exhaust gas containing water vapor-reduced CO2 to be introduced into a gas inlet 30A at the bottom of the gas cooling device 30. The gas cooling device 30 is equipped with a packing material-filled layer 33 filled with a packing material 32 for heat exchange, and cooling water flows down from a cooling water distribution plate 34 located above it and is collected in a condensate tank 36.

[0035] As the filler material 32, for example, a metal (e.g., stainless steel) pole ring can be used. It is desirable to use a pole ring with a diameter small enough that the differential pressure does not exceed a predetermined value.

[0036] The condensed water collected in the condensed water tank 36 is cooled by indirect cooling water via an indirect heat exchanger 44, for example, by a pump 42 of the cooling water supply equipment 40, and then supplied as direct cooling water to the upper part of the gas cooling device 30. In the gas cooling device 30, if the cooling water is continuously brought into direct contact with the high-temperature exhaust gas, the temperature of the direct cooling water will rise and the cooling efficiency will decrease, so the direct cooling water is cooled by the indirect heat exchanger 44 to prevent this.

[0037] As shown in Figure 4, in the gas cooling device 30, cooling water is sprayed to cool exhaust gas at 100°C or higher, for example, about 160°C, to about 40-60°C. The water comes into direct contact with the exhaust gas to cool its temperature, and the condensed water generated by the condensation of moisture in the exhaust gas is collected in a condensed water tank 36 that can hold the water for a short period of time.

[0038] At this time, if the acidic gases in the exhaust gas have been sufficiently removed, the pH of the condensed water will be near neutral. However, as the amount of acidic gas introduced into the gas cooling device 30 increases, the pH of the condensed water will decrease towards the acidic side. This phenomenon can be used to monitor the pH of the condensed water using a pH meter 46. Alternatively, the amount of an alkaline aqueous solution, such as a caustic soda solution, which is a pH adjuster injected when the pH shifts to the acidic side, can be monitored and controlled.

[0039] The exhaust gas, cooled to a predetermined temperature, for example, around 40-60°C, within the gas cooling device 30, is supplied to the CO2 separation and recovery device 50 through a gas outlet 30B located at the top of the gas cooling device 30, for example, via a cooling fan. After the CO2 is recovered in the CO2 separation and recovery device 50, the remaining exhaust gas is discharged from the chimney 14 via the flue 12.

[0040] In this embodiment, the steam separated by the steam separation membrane unit 20 is immediately returned to the flue 12 through a short steam discharge pipe (hereinafter simply referred to as the steam discharge pipe) 18. Therefore, condensation can be prevented by dilution with the exhaust gas flowing through the flue 12 before the steam separated by the steam separation membrane unit 20 condenses.

[0041] In this way, the gas from which most of the water vapor emitted from the water vapor separation membrane unit 20 has been removed has a reduced water content, thus reducing the amount of condensed water in the gas cooling device 30.

[0042] In this embodiment, the water vapor separation membrane unit 20 is wrapped with an insulating material 28 to prevent temperature drop, thereby avoiding problems such as the generation of condensed water and acid dew point corrosion within the water vapor separation membrane unit 20, and enabling continuous normal operation for a long period of time.

[0043] Furthermore, as illustrated in Figure 1, insulation materials 17 and 19 can be wrapped not only around the steam separation membrane unit 20, but also around its inlet piping 16 and steam discharge pipe 18 to prevent temperature loss.

[0044] The insulation material 19 for the steam exhaust pipe 18 can be omitted if the steam exhaust pipe 18 is sufficiently short.

[0045] Next, a second embodiment of the present invention will be described with reference to Figure 5.

[0046] This embodiment is similar to the first embodiment, but the steam discharge pipe 18 that discharges the steam separated by the steam separation membrane unit 20 is equipped with a heating device such as an electric heater 60. Other aspects are the same as the first embodiment, so a description will be omitted.

[0047] According to this embodiment, it is possible to reliably prevent the condensation of water vapor in the water vapor discharge pipe 18 while allowing it to be combined with the factory exhaust gas.

[0048] Furthermore, similar to the first embodiment, the inlet piping 16 and the steam separation membrane unit 20 can be kept warm with the insulating material 17 and insulating material 28 to prevent temperature drops.

[0049] Next, a third embodiment of the present invention will be described with reference to Figure 6 of the present invention.

[0050] In this embodiment, a thermometer 62 is installed in the steam discharge pipe 18 on the outlet side of the steam separation membrane unit 20, and a heating device such as an electric heater 60 is controlled to prevent condensation of steam in the steam discharge pipe 18 while allowing it to merge with the factory exhaust gas.

[0051] In this embodiment as well, the inlet piping 16 and the steam separation membrane unit 20 can be kept warm by the insulating material 17 and insulating material 28, thereby preventing a drop in temperature.

[0052] In the case of waste incineration facilities, the temperature of the flue exhaust gas is 160°C and the moisture content is about 20%. In this case, if the gas temperature can be maintained above the acid dew point of 120°C, highly corrosive condensate containing acidic gases will not be generated.

[0053] Therefore, in the fourth embodiment of the present invention, as shown in Figure 7, a thermometer 70 is provided on the inlet side of the water vapor separation membrane unit 20 to measure the inlet gas temperature of the water vapor separation membrane unit 20 and to control a heating device, such as an electric heater 72, provided in the water vapor separation membrane unit 20 so as to maintain a temperature of 120°C. This makes it possible to prevent the generation of highly corrosive condensate.

[0054] Furthermore, since the water vapor separation membrane unit 20 discharges gas with a high moisture content, it is desirable to control the heating device to maintain a temperature of 100°C or higher. Accordingly, in the fifth embodiment of the present invention, as shown in Figure 8, thermometers 70 and 80 are independently provided at the inlet and outlet of the water vapor separation membrane unit 20, and heating devices, such as electric heaters 72 and 82, are also independently provided and independently controlled to maintain a predetermined temperature.

[0055] According to this fifth embodiment, it is possible to reliably prevent the generation of highly corrosive condensed water containing acidic gases.

[0056] In the embodiments described above, electric heaters were used as heating devices, but the heating device is not limited to this, and may also use, for example, hot water, steam, or other similar devices.

[0057] Furthermore, it can not only control temperature but also monitor and control moisture content and humidity.

[0058] Furthermore, although the present invention was applied to combustion exhaust gas discharged from a factory in the above-described embodiment, the scope of application of the present invention is not limited to this, and can be similarly applied to facilities in general that have combustion equipment, such as coal-fired power plants, waste incineration plants, and biomass power plants. [Explanation of Symbols]

[0059] 10...Factory 12…Flute 14… Chimney 16... Inlet piping 17, 19, 28...Heat insulation material 18... Steam discharge (pipe) 20... Water vapor separation membrane unit 22... Water vapor separation membrane tube 30... Gas cooling system 50...CO2 separation and recovery device 60, 72, 82... Electric heaters 62, 70, 80…Thermometer

Claims

1. Combustion equipment and CO ２ In a facility equipped with a separation and recovery device, Combustion exhaust gas containing moisture is CO ２ A steam separation device equipped with a steam separation membrane for separating moisture from combustion exhaust gas before introducing it into a separation and recovery device, A gas cooling device for cooling the combustion exhaust gas from which moisture has been reduced by the water vapor separation device, A pretreatment device for combustion exhaust gas, characterized by being equipped with the following features.

2. The combustion exhaust gas pretreatment equipment according to claim 1, characterized in that it is equipped with piping for returning the water vapor separated by the water vapor separation device back to the flue of the facility.

3. The combustion exhaust gas pretreatment equipment according to claim 1, further comprising a condensation prevention means for preventing the condensation of water vapor separated by the water vapor separation device.

4. The combustion exhaust gas pretreatment equipment according to claim 3, characterized in that the condensation prevention means is provided in the water vapor separation device or piping.

5. The pretreatment equipment for combustion exhaust gas according to claim 4, characterized in that the condensation prevention means is a heat retention or heating means provided in the steam separation device or piping.

6. The pretreatment equipment for combustion exhaust gas according to claim 5, characterized in that the heat retention or heating means is equipped with a gas thermometer or a gas moisture content analyzer and has a temperature control mechanism for preventing condensation of water vapor in the gas or acid dew point corrosion.

7. The combustion exhaust gas pretreatment equipment according to claim 1, characterized in that the steam separation device is temperature-controlled to 120°C or higher.

8. The combustion exhaust gas is treated to reduce temperature before CO ２ In the pretreatment of combustion exhaust gas in the process of separating and recovering, A method for pretreatment of combustion exhaust gas, characterized by reducing the amount of water contained in the combustion exhaust gas before temperature reduction treatment by using a water vapor separation device equipped with a water vapor separation membrane, thereby reducing the amount of condensed water generated by the water in the combustion exhaust gas during temperature reduction treatment.

9. The pretreatment method for combustion exhaust gas according to claim 8, characterized in that the temperature of the water vapor separator is controlled or the temperature and humidity are monitored in order to prevent the generation of condensed water due to the condensation and condensation of the water vapor separated by the water vapor separator.

10. The pretreatment method for combustion exhaust gas according to claim 9, characterized in that temperature control is performed to maintain the inside of the steam separation device at 120°C or higher in order to prevent corrosion of the equipment caused by the temperature of the acidic gas contained in trace amounts in the steam separated by the steam separation device falling below the acid dew point and generating a highly corrosive solution.

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