Exhaust gas pretreatment facility, exhaust gas treatment facility, and CO2 separation / recovery method for exhaust gas pretreatment facility

Abstract

This exhaust gas pretreatment facility is disposed on the entrance side of a CO2 separation / recovery facility for separating and recovering CO2 from combustion exhaust gas. By comprising a layered double hydroxide (LDH) reaction tower filled with LDH and a gas cooling tower that cools the combustion exhaust gas discharged from the LDH reaction tower with cooling water, the removal of acidic gas components contained in the exhaust gas is efficiently performed with low equipment costs and operating costs during the separation and recovery of CO2 from the exhaust gases emitted by waste incinerators and coal-fired power plants.

Description

[Technical Field]

[0001] This invention relates to an exhaust gas pretreatment device, an exhaust gas treatment device, and a CO2 separation and recovery method for the exhaust gas pretreatment device, particularly to an exhaust gas pretreatment device suitable for use in incineration facilities containing waste or coal-fired power generation facilities, an exhaust gas treatment device equipped with the exhaust gas pretreatment device, and a CO2 separation and recovery method for the exhaust gas pretreatment device, which can remove and reduce acidic gases in the exhaust gas to a predetermined concentration while separating and recovering carbon dioxide (CO2) contained in combustion exhaust gas. [Previous Technology]

[0002] In the operation of waste incineration facilities or coal-fired power generation facilities that have equipment for incinerating waste containing garbage and recovering heat from the waste to generate electricity, the exhaust gas ultimately discharged from the chimney contains a significant amount of CO2. In recent years, preventing global warming has become increasingly important, and reducing CO2 emissions is a crucial issue.

[0003] Several examples currently exist in Japan of facilities that recover CO2 from exhaust gas at waste incineration plants. These CO2 recovery methods include chemical absorption and physical adsorption. Chemical absorption involves using an aqueous solution of an amine with CO2-absorbing properties to separate CO2 from the exhaust gas. The amine solution containing the absorbed CO2 is then heated, causing CO2 to detach from the amine solution and be recovered. Physical adsorption involves maintaining CO2 at a predetermined high pressure, causing CO2 to adsorb onto an adsorbent with CO2-absorbing properties, and then depressurizing to detach CO2 from the adsorbent and recover it. Both chemical absorption and physical adsorption methods target exhaust gas at 40-60°C; therefore, exhaust gas exceeding 100°C must be pre-cooled in a gas cooling tower involving direct water contact.

[0004] Here, the amine aqueous solution in the chemical absorption method and the adsorbent in the physical adsorption method are known to have their CO2 absorption or adsorption hindered by the acidic gases such as sulfur dioxide (SO2) contained in the exhaust gas. In particular, SO2 has a higher affinity for amine aqueous solutions or adsorbents than CO2. Taking the chemical absorption method as an example, if the amine aqueous solution containing CO2 is not heated to a temperature higher than that of CO2, SO2 cannot be removed. Therefore, in cases where the temperature of the amine aqueous solution cannot be raised to the SO2 removal temperature for economic reasons, the amine aqueous solution will remain in a state containing SO2, resulting in a decrease in CO2 absorption capacity, which is not ideal. Furthermore, hydrogen chloride (HCl), which is also contained as an acidic gas, may have adverse effects such as corrosion of equipment, so it should not be introduced into the CO2 separation and recovery equipment. Moreover, even in the case of heating the amine aqueous solution containing acidic gases such as SO2 to the CO2 removal temperature, SO2 will still be removed, albeit in trace amounts. Thus, the recovered CO2 contains acidic gas components as impurities. When the recovered CO2 is reused as a raw material in the manufacture of other products, the quality of the recovered CO2 products may be reduced, or there may be catalyst poisoning or deterioration, which may affect the manufacturing process. Therefore, it is not ideal.

[0005] Therefore, equipment is necessary to remove and reduce acidic gases in exhaust gas to a predetermined concentration. Examples of acidic gas removal methods include dry treatment, such as spraying an alkaline desalination agent like quicklime upstream of a dust collector, and wet treatment, such as circulating an alkaline aqueous solution like caustic soda towards the exhaust gas. Chemical absorption methods are often used where the acidic gas content in the exhaust gas introduced into CO2 separation and recovery equipment is below 3 ppm; therefore, wet treatment, with its excellent acidic gas removal capabilities, is employed. However, if wet treatment is chosen, a large amount of wastewater is generated after exhaust gas treatment. Therefore, the equipment required for wastewater treatment becomes large-scale, and a suitable discharge location must be secured, leading to increased costs, making it less than ideal.

[0006] Furthermore, Patent Document 1 discloses a method for removing acidic gases from exhaust gas using dry treatment. In this case, a large amount of desalination agent must be blown in to reduce the concentration of acidic gases to a low level. In addition to increasing costs, this results in a large amount of desalination residue that must be landfilled, leading to a less than ideal problem of reduced remaining lifespan of the landfill.

[0007] Furthermore, in cases where exhaust gas is cooled by a gas cooling tower, methods have been disclosed to reduce the amount of condensate generated by the condensation of moisture contained in the exhaust gas. These methods include indirect air cooling or mixing with ambient temperature air. However, this method increases the volume of exhaust gas introduced into the CO2 separation and recovery equipment, requiring a larger scale of the equipment and increasing installation costs and space requirements, thus proving less than ideal. In addition, the CO2 concentration in the exhaust gas decreases, resulting in a reduction in CO2 recovery efficiency in the CO2 separation and recovery process, further leading to the problem of equipment expansion, which is also less than ideal. [Prior Art Documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2023-17514 [Summary of the Invention]

[0009] [Problem to be Solved by the Invention] A layered double hydroxide (LDH) is a material capable of reducing the HCl or SOx contained in incineration exhaust gas to the low levels required by CO2 separation and recovery equipment. This LDH is composed of magnesium (Mg) or aluminum (Al) and hydroxide (OH), and is formed by positively charged crystals stacked in layers. This layer contains negatively charged ions and interlayer water. Generally, these negative ions are most stable in the case of carbonate ions, and carbonate-type LDH exists naturally. When exhaust gas containing acidic gases comes into contact with this carbonate-type LDH, in the case of HCl, a reaction occurs where carbonate ions in the LDH interlayer replace chloride ions in the HCl, thus removing the acidic gases. Utilizing this property, by circulating exhaust gas through a layer filled with an appropriate amount of LDH, an acidic gas removal effect equivalent to or better than that of wet treatment methods can be obtained.

[0010] The concentration of acidic gases in combustion exhaust, for example in waste incineration facilities, is typically 200-300 ppm of HCl before treatment. In general waste incineration facilities, dry treatment is commonly used, where an alkaline desalting agent, such as quicklime, is blown into the upstream side of the dust collector, causing it to deposit on the filter cloth inside the dust collector, thereby removing acidic gases. Generally, quicklime is blown in to reduce the HCl concentration in the exhaust gas from the dust collector outlet to below 50 ppm. When a portion of this exhaust gas is entirely directed to a CO2 separation and recovery unit, the acidic gases must be removed to below 3 ppm; however, in this case, an LDH (Low-density hydrant) with acidic gas removal capabilities equivalent to or greater than those of wet treatment methods can be used. By allowing only the exhaust gas containing acidic gases to flow through the LDH-coated packing layer without generating wastewater, the concentration of acidic gases can be reduced to the level required by the CO2 separation and recovery equipment, thus completing the removal of acidic gases as a pretreatment step before CO2 separation and recovery. In this case, a gas cooling tower is installed on the tail end side of the LDH reaction tower containing the LDH packing layer. The resulting condensate contains almost no acidic gas components. Therefore, there is virtually no decrease in the pH of the condensate due to acidic gas components, thus reducing the amount of alkaline aqueous solutions such as caustic soda solution required for pH adjustment before effluent discharge, thereby reducing wastewater volume.

[0011] Furthermore, since no air needs to be added for cooling the gas, it is possible to supply gas to the CO2 separation and recovery equipment without increasing the exhaust volume. This is ideal as it eliminates the need to enlarge the size of the CO2 separation and recovery equipment and the required installation space. Because no additional installation space is required, it is also beneficial for adding to existing waste incineration facilities that lack sufficient unused space.

[0012] The present invention was made in view of the above-mentioned situation, and the first objective is to provide an exhaust gas pretreatment device that can efficiently remove acidic gases contained in exhaust gas when CO2 separation and recovery devices are installed in waste incineration facilities or coal-fired power generation facilities, and can be carried out with low equipment costs and operating costs.

[0013] Furthermore, the present invention provides an exhaust gas pretreatment device as a second objective, which can easily add CO2 separation and recovery equipment to existing waste incineration facilities or coal-fired power generation facilities.

[0014] Furthermore, the present invention provides an exhaust gas pretreatment device as a third objective, which includes a CO2 separation and recovery device in the main pipeline from the incinerator or boiler to the chimney.

[0015] Furthermore, the present invention provides a fourth objective: a CO2 separation and recovery method for an exhaust gas pretreatment device, suitable for the regeneration or replacement of LDH (Liquid Dehydrogenation). [Technical Means for Solving the Problem]

[0016] The present invention relates to an exhaust gas pretreatment device, which is disposed at the inlet side of a CO2 separation and recovery device that separates and recovers CO2 from combustion exhaust gas; the exhaust gas pretreatment device is characterized by comprising: an LDH reaction tower filled with layered double hydroxide LDH; and a gas cooling tower for cooling the combustion exhaust gas discharged from the aforementioned LDH reaction tower with cooling water. The aforementioned first problem is solved by an exhaust gas pretreatment device;

[0017] Here, making the aforementioned LDH into granules with a diameter of, for example, 0.5 to 4 mm, preferably 1.0 to 2.5 mm, can improve air permeability.

[0018] Furthermore, the aforementioned LDH reaction tower is filled in such a way that the aforementioned LDH moves from top to bottom, enabling the regeneration of the aforementioned LDH after adsorption is completed, and supplying it from the upper part of the aforementioned LDH reaction tower, and enabling the aforementioned LDH to be recycled. Furthermore, the upper part of the aforementioned LDH reaction tower is equipped with an LDH supply device for replenishing LDH with acid gas removal capabilities, and the lower part of the LDH reaction tower is equipped with an LDH extractor for extracting LDH that has completed adsorption of acid gases, and an LDH discharge device for discharging the extracted LDH. Moreover, the extraction rate of the aforementioned LDH extractor can be controlled according to the pH of the condensate in the condensate tank of the gas cooling tower, or the supply amount of pH adjusting agent supplied to the condensate tank.

[0019] Furthermore, by placing the regeneration tank for the aforementioned regeneration at the lower part of the aforementioned LDH reaction tower, the equipment can be miniaturized.

[0020] Furthermore, the aforementioned exhaust pretreatment equipment is installed in the bypass pipeline of the main pipeline from the incinerator or boiler to the chimney, thereby solving the aforementioned second problem.

[0021] Furthermore, the aforementioned exhaust pretreatment equipment is installed along the main pipeline from the incinerator or boiler to the chimney, thereby solving the aforementioned third problem without the need for a bypass pipeline.

[0022] Furthermore, the present invention addresses the fourth issue by monitoring the pH value of the cooling water in the gas cooling tower in the CO2 separation and recovery method using the aforementioned exhaust pretreatment equipment, and regenerating or replacing the aforementioned LDH when it is below a predetermined value.

[0023] Alternatively, in the CO2 separation and recovery method using the aforementioned exhaust gas pretreatment equipment, the present invention monitors the amount of pH adjuster added, determined by the pH value of the cooling water in the aforementioned gas cooling tower, and regenerates or replaces the aforementioned LDH when the pH value exceeds a predetermined value, thereby similarly solving the aforementioned problems. [Effects of the Invention]

[0024] According to the present invention, HCl gas, or SO2 and other gases that are more selectively bonded to the adsorbent than CO2, can be efficiently removed from the CO2 separation and recovery equipment without using wet treatment methods or the like. Furthermore, the pH of the exhaust condensate discharged from the gas cooling tower located on the tail side of the LDH reaction tower can be maintained at approximately neutral, thus reducing the amount of pH adjusters such as caustic soda solution that are conventionally used, thereby lowering equipment and operating costs.

Implementation Method

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the present invention is not limited to the contents described in the following embodiments and examples. Also, the constituent elements of the embodiments and examples described below include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that are equivalent. Moreover, the constituent elements disclosed in the embodiments and examples described below can be appropriately combined and appropriately selected for use.

[0027] First, the exhaust treatment system using the present invention will be described.

[0028] The exhaust treatment system, as shown in Figure 1, has: a main pipeline 10 (represented by a thick solid line), which is connected to the chimney 18 via a dust collector 14 and (not shown) a denitrification reaction tower, an induced draft fan 16, etc., through which exhaust gas is discharged to the atmosphere.

[0029] In the aforementioned exhaust gas treatment system, in the first embodiment of the present invention, a bypass line 20 (shown as a thick dashed line) is provided between the dust collector 14 sprayed with a desalination agent such as quicklime and the flue on the tail side of the induced draft fan 16 and the chimney 18, so that part or all of the exhaust gas is drawn to the bypass line 20 by the suction fan 70. The bypass line 20 is equipped with the exhaust gas pretreatment device 30 of the present invention, the aforementioned suction fan 70, and a conventional CO2 separation and recovery device 80. The CO2 separation and recovery device 80 is equipped with a flue 82 for recovering the separated and recovered CO2 and a flue 84 for returning the exhaust gas after CO2 removal to the main line 10.

[0030] The aforementioned exhaust gas pretreatment device 30 mainly comprises the LDH reaction tower 32 and the gas cooling tower 50 of the present invention. The exhaust gas drawn into the exhaust gas pretreatment device 30 first flows into the LDH reaction tower 32.

[0031] The aforementioned LDH reaction tower 32, as detailed in Figure 2, includes an inlet 32A for exhaust gas containing acidic gases and an outlet 32B for exhaust gas after acidic gas removal. The exhaust gas introduced into the LDH reaction tower 32 is introduced from the exhaust gas inlet 32A at the bottom of the aforementioned LDH reaction tower 32, and the exhaust gas after acidic gas removal is discharged through the exhaust gas outlet 32B at the top of the aforementioned LDH reaction tower 32. Furthermore, even if the gas is introduced from the top and discharged from the bottom, the acidic gas removal efficiency will not change, so either method is acceptable.

[0032] Inside the aforementioned LDH reaction tower 32, there is an LDH packing layer 34, which is filled with a predetermined amount of LDH particles 33 with a predetermined particle size, for example, a diameter of 0.5~4 mm, preferably a diameter of 1.0~2.5 mm, in a space velocity SV (= gas flow rate / packing volume: unit h-1) = (1,000~10,000 h-1, preferably 1,500~3,000 h-1). Here, if the space velocity SV is small, the LDH packing amount increases relative to the gas flow rate, and acidic gases can be removed for a longer time by filling once. On the other hand, if the LDH packing amount is increased, the acidic gas treatment equipment will become bulky, which is not ideal from the viewpoint of minimizing equipment cost or installation area. In order to reduce equipment cost, it is preferable to increase the space velocity SV so that the LDH packing amount = packing volume is reduced. Therefore, acid gas treatment equipment designed with a space velocity (SV) in the range of 1,000 to 10,000 h⁻¹, preferably 1,500 to 3,000 h⁻¹, is the most suitable for balancing the guarantee of treatment time with the minimization of equipment cost or installation area.

[0033] Furthermore, if the particle size of LDH particles 33 is small, the gaps during filling will be small, thereby increasing the pressure difference between the inlet and outlet gases of the LDH reaction tower 32. This leads to an increase in the power consumption of the suction fan 70, which is not ideal. However, on the other hand, due to the increased specific surface area of ​​the LDH material, the desired result of improved acid gas removal efficiency can be achieved. In the embodiment, when the particle size of LDH is 3.0 mm, the pressure difference between the inlet and outlet gases of the LDH reaction tower 32 is 0.4~0.5 kPa. A pressure difference of about 1.0 kPa is sufficient to avoid causing problems with the power consumption of the suction fan 70, therefore, a particle size of 1.0 mm to 2.5 mm for LDH is preferred.

[0034] An LDH supply device 36 for supplementing LDH with acid gas removal capability is provided at the upper part of the aforementioned LDH reaction tower 32, and an LDH discharge device 38 for discharging LDH that has completed adsorption of acid gases is provided at the lower part of the LDH reaction tower.

[0035] An example of the movement state of the LDH particles 33 within the aforementioned LDH reaction tower 32 is shown in Figure 3. The LDH particles 33 supplied from above to the LDH reaction tower 32 are extracted by the LDH extractor 35 located at the bottom, and move from top to bottom within the LDH reaction tower 32. At this time, they react with the exhaust gas supplied from below, while clean gas is discharged from above.

[0036] The extraction amount of the LDH extractor 35 of the aforementioned LDH discharge device 38 is, as will be explained later, controlled, for example, according to the pH of the condensate tank 56 of the gas cooling tower 50, or the supply amount of pH adjuster (such as an alkaline aqueous solution like caustic soda solution) supplied to the condensate tank 56.

[0037] The LDH discharged from the aforementioned LDH discharge device 38 is introduced into a regeneration tank 40 which is supplied with an alkaline aqueous solution, such as a caustic soda aqueous solution. After regeneration, it is dried by a dryer 42 and then supplied to the aforementioned LDH supply device 36 for recycling. In this way, the amount of expensive LDH used can be reduced.

[0038] Next, as shown in FIG2, the exhaust gas flowing through the LDH reaction tower 32 and removed from the acidic gas is introduced into the gas inlet 50A of the gas cooling tower 50 located on the tail side of the LDH reaction tower 32.

[0039] The aforementioned gas cooling tower 50 is equipped with a filling material filling layer 53 filled with filling material 52 for heat exchange. Cooling water flows down from the cooling water dispersion plate 54 above the filling material filling layer 53 and is collected by the condensate tank 56.

[0040] The aforementioned packing material 52 is, for example, made of metal, preferably a stainless steel Pall ring. Furthermore, since the amount of acidic gas is reduced by the LDH reaction tower 32 located at the front end, expensive materials such as SUS316 or 316L are not required; the more inexpensive SUS304 can be used. The Pall ring should also be small in radius to ensure that the pressure differential does not exceed a predetermined value.

[0041] The condensate collected in the condensate tank 56 is, for example, cooled by indirect cooling water via an indirect heat exchanger 64 through a pump 62 of the cooling water supply device 60, and then supplied as direct cooling water to the upper part of the aforementioned gas cooling tower 50. Here, if the direct cooling water is continuously exposed to high-temperature exhaust gas in the gas cooling tower 50, the temperature of the direct cooling water will rise and the cooling efficiency will decrease. Therefore, to prevent this from happening, the direct cooling water is cooled by the indirect heat exchanger 64.

[0042] As shown in Figure 2, the gas cooling tower 50 sprays cooling water that is used to cool exhaust gas at a temperature of 100°C or above, for example, around 160°C, to around 40~60°C. The water comes into direct contact with the exhaust gas to cool the exhaust gas temperature and is collected in a condensate tank 56 that can retain the water in the exhaust gas for a short time to form condensate.

[0043] At this time, if the acidic gas is sufficiently removed by the LDH reaction tower 32, the pH of the condensate will be around neutral. If the adsorption capacity of the acidic gas by the LDH particles 33 decreases and the amount of acidic gas introduced into the aforementioned gas cooling tower 50 increases, the pH of the condensate will decrease towards the acidic side. Utilizing this phenomenon, the pH of the condensate can be monitored by a pH meter 66, thereby managing the regeneration or replacement period of the LDH particles 33. Alternatively, the amount of alkaline aqueous solution, such as a caustic soda aqueous solution, added as a pH adjuster when the pH shifts to the acidic side can be monitored and managed, thereby also managing the regeneration or replacement period of the LDH particles 33. Here, if a gas cooling tower 50 is installed upstream of the LDH reaction tower 32, the exhaust gas containing acidic gas is cooled by direct contact with the cooling water, so the acidic components will transfer to the condensate and the pH will decrease towards the acidic side. As a result, the amount of alkaline aqueous solutions such as caustic soda solution used for neutralization will increase, leading to increased costs and a larger amount of condensate, which is not ideal.

[0044] The exhaust gas cooled to a predetermined temperature, such as 40-60°C, in the aforementioned gas cooling tower 50 is supplied to the CO2 separation and recovery device 80 via the exhaust fan 70 from the gas outlet 50B located at the top of the gas cooling tower 50. The CO2 recovered by the CO2 separation and recovery device 80 is discharged from the flue 82, and the remaining exhaust gas is returned to the chimney 18 of the main pipeline 10 via the flue 84.

[0045] Next, the second embodiment of the present invention will be shown in FIG4. This second embodiment is a miniaturized device provided in the exhaust gas pretreatment equipment 30 provided in the bypass pipeline 20 in the same manner as the first embodiment, with the regeneration tank 40 located directly below the LDH reaction tower 32.

[0046] In this embodiment, the LDH particles 33 that are regenerated in the regeneration tank 40 are discharged outside the LDH reaction tower 32 by the LDH discharge device 38, dried by the dryer 42, and then supplied to the LDH supply device 36 for recycling.

[0047] Other components and functions are the same as in the first embodiment, so the description is omitted.

[0048] Next, the third embodiment of the present invention, in which the LDH reaction tower 32 and the gas cooling tower 50 are provided in the main pipeline 10 instead of the bypass pipeline 20, is shown in FIG5.

[0049] Other components and functions are the same as in the first embodiment, so the description is omitted.

[0050] Thus, according to this embodiment, the present invention can be implemented without the need to install a bypass pipeline 20.

[0051] In the aforementioned embodiments, a regeneration tank 40 and a dryer 42 are provided, thus enabling the LDH granules 33 to be regenerated and recycled, resulting in high economic efficiency. Alternatively, the regeneration tank 40 or the dryer 42 can be omitted, and the LDH granules 33 can be discarded after use.

[0052] In the foregoing embodiment, the LDH filling the LDH reaction tower 32 is LDH particles 33, and a moving layer is formed in the LDH reaction tower 32. However, it is not necessary to use LDH particles 33, and it is also possible not to form a moving layer in the LDH reaction tower 32.

[0053] Furthermore, the composition of the gas cooling tower 50 is not limited to the use of an indirect heat exchanger 64.

[0054] The temperature of the exhaust gas in each location is only one example.

[0055] Furthermore, in the foregoing description, the present invention is applied to the pretreatment of CO2 separation and recovery of exhaust gas from waste incineration facilities such as municipal solid waste. However, the application of the present invention is not limited to this. For example, it can also be applied to the pretreatment of CO2 separation and recovery of exhaust gas from coal-fired power generation facilities. [Industrial Applicability] The present invention provides an exhaust gas pretreatment device that can efficiently remove acidic gases from the exhaust gas when separating and recovering carbon dioxide (CO2) contained in the combustion exhaust gas of waste incineration facilities or coal-fired power generation facilities containing waste, and can be carried out with low equipment and operating costs. [Simplified Explanation of the Diagram]

[0025] [Figure 1] shows the overall structure of the first embodiment of the present invention. [Figure 2] shows an enlarged cross-sectional view of the specific components of the first embodiment. [Figure 3] also shows a cross-sectional view of the operation inside the LDH reaction tower. [Figure 4] shows the overall structure of the second embodiment of the present invention. [Figure 5] shows the overall structure of the third embodiment of the present invention.

Claims

1. An exhaust gas pretreatment device, disposed at the inlet side of a CO2 separation and recovery device that separates and recovers CO2 from combustion exhaust gas; the exhaust gas pretreatment device is characterized by comprising: an LDH reaction tower filled with layered double hydroxide LDH; and a gas cooling tower for cooling the combustion exhaust gas discharged from the aforementioned LDH reaction tower by means of cooling water.

2. The exhaust gas pretreatment apparatus as described in claim 1, wherein, The aforementioned LDH is granular.

3. The exhaust gas pretreatment equipment as described in claim 2, wherein, The diameter of the LDH particles mentioned above is 0.5~4 mm, preferably 1.0~2.5 mm.

4. The exhaust gas pretreatment apparatus as described in claim 1, wherein, The aforementioned LDH reaction tower is filled in such a way that the aforementioned LDH moves from top to bottom, which enables the adsorption to be completed and the regeneration of the aforementioned LDH to be supplied from the top of the aforementioned LDH reaction tower.

5. The exhaust gas pretreatment equipment as described in claim 4, wherein, The upper part of the aforementioned LDH reaction tower is equipped with an LDH supply device that replenishes LDH with acid gas removal capabilities, and the lower part of the LDH reaction tower is equipped with an LDH extractor that extracts LDH that has completed adsorption of acid gases, and an LDH discharge device that discharges the extracted LDH.

6. The exhaust gas pretreatment apparatus as described in claim 5, wherein, The extraction rate of the aforementioned LDH extractor is controlled according to the pH of the condensate in the condensate tank of the gas cooling tower, or the amount of pH adjuster supplied to the condensate tank.

7. The exhaust gas pretreatment apparatus as described in claim 4, wherein, The regeneration tank used for the aforementioned regeneration is located at the bottom of the aforementioned LDH reaction tower.

8. An exhaust gas treatment device, wherein the exhaust gas pretreatment device described in claim 1 is installed in a bypass pipeline of the main pipeline from the incinerator or boiler to the chimney.

9. An exhaust gas treatment device, wherein the exhaust gas pretreatment device described in claim 1 is located along the main pipeline from the incinerator or boiler to the chimney.

10. A method for CO2 separation and recovery of an exhaust gas pretreatment device, wherein, in the CO2 separation and recovery method of the exhaust gas pretreatment device described in any one of claims 1 to 7, the pH value of the cooling water of the aforementioned gas cooling tower is monitored, and when it is lower than a predetermined value, the aforementioned LDH is regenerated or replaced.

11. A method for CO2 separation and recovery of an exhaust gas pretreatment device, comprising, in using the CO2 separation and recovery method of the exhaust gas pretreatment device described in any one of claims 1 to 7, monitoring the amount of pH adjuster added based on the pH value of the cooling water of the aforementioned gas cooling tower, and regenerating or replacing the aforementioned LDH when the pH value exceeds a predetermined value.

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