JP2024058173A - Exhaust gas treatment equipment - Google Patents

Abstract

[Problem] To easily and appropriately recover carbon dioxide from exhaust gas. [Solution] An exhaust gas treatment device 1 includes a dust collector 32 provided in a flue 9 through which exhaust gas flows, a chemical supply unit 22 that supplies a powdered CO2 treatment chemical that chemically reacts with carbon dioxide to a chemical supply position P2 located upstream of the dust collector 32 in the flue 9, and a collected material heating unit 41 that recovers material captured by the dust collector 32 and heats the material to a temperature at which carbon dioxide is extracted from the CO2 treatment chemical. This makes it possible to easily and appropriately recover carbon dioxide from exhaust gas. [Selected Figure] Figure 1

Description

The present invention relates to an exhaust gas treatment device.

In recent years, there has been an increasing demand for carbon dioxide (CO ₂ ) capture from combustion exhaust gas in coal-fired power plants and waste incineration facilities. In the conventional amine-based chemical absorption method for carbon dioxide capture, it is necessary to lower the exhaust gas temperature to about 40° C. due to the performance constraints of organic chemicals. Even in processes using inorganic alkaline chemicals, etc., from the viewpoints of reactivity, reaction rate, and recycling of chemicals after carbon dioxide absorption, many processes involve contacting the exhaust gas with an absorption liquid in which the chemicals are dissolved in liquid.

In addition, Patent Document 1 discloses a method in which fly ash is brought into contact with exhaust gas discharged from a waste incinerator, and alkaline components such as Ca(OH) ₂ and CaO contained in the fly ash are reacted with carbon dioxide in the exhaust gas to carbonate the fly ash. This makes it possible to lower the pH of the fly ash and suppress the elution of heavy metals. In the exhaust gas treatment system of Patent Document 2, a first-stage bag filter and a second-stage bag filter are provided. A mixture of a reaction product generated by the reaction between the acid gas removal agent blown into the second-stage bag filter and the acid gas components in the exhaust gas and an unreacted acid gas removal agent not used in the reaction is discharged from the second-stage bag filter. The mixture is supplied to a duct upstream of the first-stage bag filter and is effectively utilized in the first-stage bag filter. In "3.2 Carbonation of Ca(OH) ₂ " of Non-Patent Document 1, carbonation of Ca(OH) ₂ was performed in a low-humidity and high-humidity carbon dioxide atmosphere. As a result, as shown in the upper part of FIG. 3, in a low-humidity atmosphere, the carbonation rate of Ca(OH) 2 increases when the initial moisture content of the Ca(OH) ₂ is from 0% to 30%, and decreases when the initial moisture content is from 30% to 60%.

JP 2022-53873 A Japanese Patent No. 6413038

Yukio Noma and Akiko Takada, "Carbonation of High Alkaline Fly Ash and Leaching Characteristics of Treated Fly Ash," Journal of the Japan Society of Waste Management, 1997, vol. 8, No. 4, pp. 129-137

However, in the above-mentioned carbon dioxide capture technology, lowering the temperature of the exhaust gas to 40°C requires large equipment and energy, and in fact, it may be necessary to reheat the exhaust gas. In addition, the process of contacting the exhaust gas with the absorption liquid requires treatment of the waste liquid, making the process complicated. Therefore, a new method for easily and appropriately capturing carbon dioxide from exhaust gas is required.

The present invention has been developed in consideration of the above problems, and aims to easily and appropriately recover carbon dioxide from exhaust gas.

Aspect 1 of the present invention is an exhaust gas treatment device that includes a dust collector provided in a flue through which exhaust gas flows, a chemical supply unit that supplies a powdered chemical that chemically reacts with carbon dioxide to a chemical supply position located upstream of the dust collector in the flue, and a captured material heating unit that recovers material captured by the dust collector and heats the captured material to a temperature at which carbon dioxide is extracted from the chemical.

Aspect 2 of the present invention is an exhaust gas treatment device according to aspect 1, further comprising another dust collector provided upstream of the chemical supply position in the flue, and another chemical supply unit that supplies a powdered alkaline chemical upstream of the other dust collector in the flue.

Aspect 3 of the present invention is an exhaust gas treatment device according to aspect 2, in which the collected material heated in the collected material heating section is regenerated as the chemical and reused in the chemical supply section.

Aspect 4 of the present invention is an exhaust gas treatment device according to aspect 3, in which the chemical agent is a metal hydroxide, and the collected material is regenerated as the chemical agent by a hydration reaction of the collected material heated in the collected material heating section.

Aspect 5 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4, further comprising a water vapor supply section that supplies water vapor into the collected material heating section, and a separation section that separates water and carbon dioxide from the carbon dioxide-containing water vapor discharged from the collected material heating section.

Aspect 6 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4, further comprising an inert gas supply section that supplies an inert gas into the collected material heating section, and a separation section that separates the inert gas and carbon dioxide from the carbon dioxide-containing gas discharged from the collected material heating section.

Aspect 7 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4, further comprising a water vapor supply section that supplies water vapor into the collected material heating section, an inert gas supply section that supplies an inert gas into the collected material heating section, a separation section that separates water and carbon dioxide from the gas discharged from the collected material heating section, and another separation section that separates the inert gas and carbon dioxide from the gas.

Aspect 8 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4 (or any one of aspects 1 to 7), in which the temperature of the exhaust gas in the dust collector is 100 to 200°C.

Aspect 9 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4 (or any one of aspects 1 to 8), in which a portion of the collected material collected by the dust collector is supplied to the drug supply position without passing through the collected material heating section.

Aspect 10 of the present invention is an exhaust gas treatment device according to any one of aspects 1 to 4 (or any one of aspects 1 to 9), in which a portion of the exhaust gas that has passed through the dust collector is returned to the upstream side of the dust collector in the flue.

Aspect 11 of the present invention is an exhaust gas treatment device that includes a first dust collector provided in a flue through which exhaust gas flows, a first chemical supply unit that supplies a powdered alkaline chemical upstream of the first dust collector in the flue, a second dust collector provided downstream of the first dust collector in the flue, and a second chemical supply unit that supplies a powdered chemical that chemically reacts with carbon dioxide to a chemical supply position in the flue between the first dust collector and the second dust collector, and the temperature of the exhaust gas in the second dust collector is 100 to 200°C.

The present invention makes it possible to easily and effectively recover carbon dioxide from exhaust gas.

1 is a block diagram showing a configuration of an exhaust gas treatment device according to a first embodiment. FIG. 6 is a block diagram showing a configuration of an exhaust gas treatment device according to a second embodiment. FIG. 11 is a block diagram showing a configuration of an exhaust gas treatment device according to a third embodiment. FIG. 13 is a block diagram showing a configuration of an exhaust gas treatment device according to a fourth embodiment. FIG. 13 is a block diagram showing the configuration of an exhaust gas treatment device according to a fifth embodiment. FIG. 13 is a block diagram showing another example of an exhaust gas treatment device.

First Embodiment
FIG. 1 is a block diagram showing the configuration of an exhaust gas treatment device 1 according to a first embodiment of the present invention. The exhaust gas treatment device 1 is provided in an incineration facility that incinerates waste such as municipal waste. In this embodiment, the exhaust gas treatment device 1 is provided in a flue 9, which is a gas flow path that connects an incinerator and a chimney in the incineration facility. In FIG. 1, a part of the flue 9 is shown by a thick solid line. In the incineration facility, exhaust gas (combustion gas) generated in the incinerator is discharged into the flue 9 by an induced draft fan (not shown), and is guided to the chimney via the exhaust gas treatment device 1. In the exhaust gas treatment device 1, a predetermined treatment is performed on the exhaust gas flowing through the flue 9.

The exhaust gas treatment device 1 includes a first chemical supply unit 21, a second chemical supply unit 22, a first dust collector 31, a second dust collector 32, a fly ash storage tank 311, a collected matter heating unit 41, a hydration regeneration unit 42, a chemical tank 43, and a _CO2 gas tank 49. As described later, the first chemical supply unit 21 and the second chemical supply unit 22 supply a predetermined chemical into the flue 9. In the flue 9, from the upstream side to the downstream side in the flow direction of the exhaust gas (i.e., from the incinerator to the chimney), a chemical supply position P1 by the first chemical supply unit 21 (hereinafter referred to as the "first chemical supply position P1"), the first dust collector 31, a chemical supply position P2 by the second chemical supply unit 22 (hereinafter referred to as the "second chemical supply position P2"), and the second dust collector 32 are provided in this order.

The first chemical supply unit 21 has, for example, a table feeder, and injects a powdered alkaline chemical into the flue 9 at the first chemical supply position P1. That is, the first chemical supply unit 21 supplies an alkaline chemical to the exhaust gas flowing through the flue 9. The alkaline chemical is a chemical for desalination and desulfurization, and includes, for example, slaked lime (calcium hydroxide (Ca(OH) ₂ )). The alkaline chemical may include other calcium-based chemicals (calcium-containing chemicals) such as dolomite hydroxide [Ca(OH) ₂ ·Mg(OH) ₂ ], or may include chemicals other than calcium-based chemicals.

The first dust collector 31 is a filter type (bag filter) that collects fly ash contained in the exhaust gas using a filter cloth. The alkaline chemicals supplied by the first chemical supply unit 21 are also collected on the filter cloth. The fly ash and alkaline chemicals are deposited on the filter cloth. The first dust collector 31 is a chemical collector that collects alkaline chemicals in the flue 9. Inside the first dust collector 31, when the exhaust gas passes through the filter cloth, a reaction occurs between the alkaline chemicals deposited on the filter cloth and the acidic gases contained in the exhaust gas, and the acidic gases are removed from the exhaust gas. Examples of the acidic gases include hydrogen chloride (HCl) and sulfur oxides (SOx). The removal of acidic gases by alkaline chemicals also occurs in the flue 9.

In the first dust collector 31, the fly ash and alkaline chemicals deposited on the filter cloth are removed by a backwashing operation using compressed gas. In the backwashing operation, compressed gas (pulse jet) is supplied to the filter cloth from the downstream side to the upstream side in the flow direction of the exhaust gas. The compressed gas is, for example, compressed air. A fly ash storage tank 311 is connected to the first dust collector 31, and the fly ash and alkaline chemicals removed from the filter cloth, i.e., the material collected by the first dust collector 31, are discharged to and stored in the fly ash storage tank 311. The exhaust gas that has passed through the first dust collector 31 contains almost no fly ash. Although not shown, the fly ash and alkaline chemicals removed from the first dust collector 31 may be recirculated to the flue 9 (for example, upstream of the first dust collector 31), in which case a known fly ash recirculation device can be used.

The second chemical supply unit 22 has, for example, a table feeder, and injects a powdered inorganic chemical into the flue 9 at the second chemical supply position P2. That is, the second chemical supply unit 22 supplies the chemical to the flue gas flowing through the flue 9. The chemical is used to recover carbon dioxide (CO ₂ ) gas in the flue gas, and is hereinafter referred to as a "CO ₂ treatment chemical." The CO ₂ treatment chemical is a substance that chemically reacts with carbon dioxide, and is, for example, an alkaline chemical such as magnesium hydroxide (Mg(OH) ₂ ), magnesium oxide (MgO), calcium hydroxide, or calcium oxide (CaO). The CO ₂ treatment chemical may be the same as the alkaline chemical supplied from the first chemical supply unit 21 to the flue 9, or may be different. In the following description, the CO ₂ treatment chemical is assumed to be magnesium hydroxide.

The second dust collector 32 is a filter type (bag filter) and collects the _CO2 treatment agent supplied by the second chemical supply unit 22 with a filter cloth. The _CO2 treatment agent is deposited on the filter cloth. The second dust collector 32 is a chemical collector that collects the _CO2 treatment agent in the flue 9. A small amount of fly ash contained in the flue gas may be collected by the filter cloth of the second dust collector 32. Inside the second dust collector 32, when the flue gas passes through the filter cloth, a reaction occurs between the _CO2 treatment agent deposited on the filter cloth and the _CO2 gas contained in the flue gas. In this treatment example in which the _CO2 treatment agent is magnesium hydroxide, a carbonation reaction represented by (Mg(OH) ₂ + _CO2 → _MgCO3 + _H2O ) occurs, and the _CO2 gas is removed from the flue gas. In other words, the _CO2 gas in the flue gas is absorbed by the _CO2 treatment agent. In the flue gas flowing into the second dust collector 32, acidic gases that react more easily with the _CO2 treatment agent than _CO2 gas are removed, so that it is possible to efficiently remove _CO2 gas from the flue gas. Note that a carbonation reaction also occurs when other metal hydroxides such as calcium hydroxide or metal oxides such as magnesium oxide or calcium oxide are used as the _CO2 treatment agent.

In addition, in the incineration facility, a temperature reducing section 51 is provided upstream of the second dust collector 32 in the flue 9 (upstream of the first dust collector 31 in the example of FIG. 1), and the temperature of the exhaust gas is reduced to a predetermined temperature range. The temperature reducing section 51 is, for example, a temperature reducing tower that sprays water on the exhaust gas, or a heat exchanger such as a boiler. The temperature of the exhaust gas flowing into the second dust collector 32 is, for example, 60 to 250 ° C., preferably 100 to 200 ° C. In this way, the relative humidity of the exhaust gas flowing into the second dust collector 32 is relatively high due to the temperature reduction of the exhaust gas by the temperature reducing section 51. As a result, in the second dust collector 32, moisture is present on the surface of the CO ₂ treatment agent, and the carbonation reaction can be efficiently promoted. Removal of CO ₂ gas by the CO ₂ treatment agent also occurs in the flue 9. Depending on the design of the exhaust gas processing device 1, the temperature reducing section 51 may be provided between the first dust collector 31 and the second dust collector 32. Furthermore, in the temperature reducing section 51, moisture (water vapor) may be mixed into the exhaust gas.

Incidentally, the above-mentioned non-patent document 1, "Carbonation of High Alkaline Fly Ash and Dissolution Characteristics of Treated Fly Ash" by Yukio Noma and Akiko Takada (Journal of the Japan Society of Waste Management, vol. 8, No. 4, pp. 129-137, 1997), shows that in a low-humidity carbon dioxide atmosphere, the carbonation rate of Ca(OH) ₂ increases when the initial moisture content of Ca(OH) ₂ is 0% to 30%, and decreases when the initial moisture content is 30% to 60%. Therefore, in order to promote the removal of _CO2 gas by the _CO2 treatment agent (i.e., carbonation of the _CO2 treatment agent), it is considered preferable that the weight of moisture of about 10 to 30% of the weight of the _CO2 treatment agent supplied to a given volume of flue gas is contained in the given volume of flue gas inside the second dust collector 32.

In the second dust collector 32, the _CO2 treatment agent (including the _CO2 treatment agent after carbonation) and the like accumulated on the filter cloth are brushed off by a backwashing operation similar to that of the first dust collector 31. A collected material heating section 41 is connected to the second dust collector 32, and the _CO2 treatment agent and the like brushed off from the filter cloth, i.e., the material captured by the second dust collector 32, is discharged to and collected by the collected material heating section 41. The collected material mainly contains unreacted _CO2 treatment agent and the _CO2 treatment agent after carbonation (in this processing example, Mg(OH) ₂ and _MgCO3 ).

The collected material heater 41 is an electric heater, a steam heat exchange heater, or the like, and heats the collected collected material. The temperature of the collected material heated by the collected material heater 41 is higher than the temperature of the flue gas in the second dust collector 32. The lower limit of the heating temperature of the collected material is, for example, 250°C, preferably 300°C, and more preferably 350°C. The upper limit of the heating temperature of the collected material is, for example, 600°C, preferably 500°C, and more preferably 400°C. By heating the collected material, _CO2 gas is extracted from the _CO2 treatment agent after carbonation. In this treatment example, decarbonation represented by ( _MgCO3 →MgO + _CO2 ) occurs by heating the collected material to 350 to 400°C. The extracted _CO2 gas is discharged and stored in the _CO2 gas tank 49. In this way, _CO2 gas is recovered from the flue gas using the _CO2 treatment agent. In the heating by the collected material heating unit 41, unreacted _CO2 treatment agent (Mg(OH) ₂ ) may be converted to MgO. When other metal hydroxides or metal oxides are used as the _CO2 treatment agent, _CO2 gas is similarly extracted by heating. The heating temperature of the collected material in the collected material heating unit 41 may be appropriately changed as long as it is a temperature at which _CO2 gas can be extracted from the _CO2 treatment agent after carbonation.

The collected material after heating by the collected material heating section 41 is sent to the hydration regeneration section 42. In this processing example, the collected material mainly contains magnesium oxide (such as the CO ₂ treatment agent after decarbonation). The collected material may also contain unreacted CO ₂ treatment agent (magnesium hydroxide). In the hydration regeneration section 42, magnesium oxide is reacted with water (by hydration) to generate magnesium hydroxide powder. In other words, the CO ₂ treatment agent after decarbonation is hydrated and regenerated as a CO ₂ treatment agent. The generation of magnesium hydroxide by hydration of magnesium oxide may be performed by a well-known method. The same applies when other metal hydroxides are used as the CO ₂ treatment agent. When a metal oxide is used as the CO ₂ treatment agent, the metal oxide may be generated (regenerated) by heating the CO ₂ treatment agent after carbonation. In FIG. 1, the regenerated CO ₂ treatment agent is described as a "regenerated agent" (similarly in other figures).

Thereafter, the regenerated _CO2 treatment agent (magnesium hydroxide powder) is sent to and stored in the agent tank 43. Unused _CO2 treatment agent is supplied to the agent tank 43 as necessary. The second agent supply unit 22 takes out the _CO2 treatment agent from the agent tank 43, and supplies the _CO2 treatment agent to the flue gas flowing through the flue 9, as described above. Note that in the captured material heating unit 41 and the hydration regeneration unit 42, it is sufficient that at least a portion of the captured material is regenerated as a _CO2 treatment agent.

As described above, the exhaust gas treatment device 1 includes the dust collector 32 (second dust collector 32), the chemical supply unit 22 (second chemical supply unit 22), and the collected material heating unit 41. The dust collector 32 is provided in the flue 9 through which the exhaust gas flows. The chemical supply unit 22 supplies a powdered CO ₂ treatment chemical that chemically reacts with carbon dioxide to the chemical supply position P2 located upstream of the dust collector 32 in the flue 9. The collected material heating unit 41 recovers the collected material collected by the dust collector 32 and heats the collected material to a temperature at which carbon dioxide is extracted from the CO ₂ treatment chemical. This makes it possible for the exhaust gas treatment device 1 to easily and appropriately recover carbon dioxide from the exhaust gas without excessively lowering the temperature of the exhaust gas and without using an absorbing liquid (solution) that is difficult to treat.

Preferably, the temperature of the exhaust gas in the dust collector 32 is 100 to 200° C. This increases the relative humidity of the exhaust gas flowing into the dust collector 32, allowing the carbonation reaction of the _CO2 treatment agent to proceed efficiently, and making it possible to remove a large amount of carbon dioxide from the exhaust gas.

Preferably, the exhaust gas treatment device 1 further includes another dust collector 31 (first dust collector 31) and another chemical supply unit 21 (first chemical supply unit 21). The dust collector 31 is provided upstream of the chemical supply position P2 in the flue 9. The chemical supply unit 21 supplies a powdered alkaline chemical to the upstream side of the dust collector 31 in the flue 9. This allows the upstream dust collector 31 to remove acid gas and fly ash contained in the exhaust gas in advance, and the downstream dust collector 32 to efficiently recover carbon dioxide. Note that, depending on the design of the exhaust gas treatment device 1, the other dust collector 31 and the other chemical supply unit 21 may be omitted.

Preferably, (at least a part of) the captured material heated in the captured material heating section 41 is regenerated as a _CO2 treatment agent and reused in the agent supply section 22. In this way, by reusing the _CO2 treatment agent, it is possible to reduce the running costs of the exhaust gas treatment device 1. In this case, it is preferable that the _CO2 treatment agent is a metal hydroxide, and that the captured material heated in the captured material heating section 41 is regenerated as a _CO2 treatment agent through a hydration reaction. This makes it possible to easily realize reuse of the _CO2 treatment agent.

Incidentally, when reusing the CO ₂ treatment agent, a part of the CO ₂ treatment agent is altered (degraded) into chlorides and sulfate compounds due to trace amounts of hydrogen chloride, sulfur oxides, etc. remaining in the exhaust gas (not removed by the first dust collector 31). Since such altered CO ₂ treatment agent is not regenerated by the treatment by the collected matter heating unit 41 and the hydration regeneration unit 42, when the amount of altered CO ₂ treatment agent increases, the amount of CO ₂ gas recovered decreases. Therefore, in a preferred exhaust gas treatment device 1, for example, a CO ₂ concentration sensor that measures the concentration of CO ₂ gas extracted from the CO ₂ treatment agent after carbonation is provided between the collected matter heating unit 41 and the CO ₂ gas tank 49. Then, when the concentration falls below a predetermined value (i.e., when the recovery rate of CO ₂ gas decreases), part or all of the CO ₂ treatment agent in the collected matter heating unit 41 is discharged to the outside and disposed of, and a lot of new (unused) CO ₂ treatment agent is used.

In the above process, a _CO2 concentration sensor may be provided downstream of the second dust collector 32 in the flue 9, and a decrease in the _CO2 gas recovery rate may be detected based on the measurement value of the sensor. Also, a collected matter distribution section (see collected matter distribution section 46 in FIG. 4 described later) may be disposed between the second dust collector 32 and the collected matter heating section 41, and the collected matter distribution section may discharge a part or all of the collected matter ( _CO2 treatment agent) from the second dust collector 32 to the outside. As described above, in the flue gas treatment device 1, the amount of the _CO2 treatment agent to be reused is adjusted based on the _CO2 gas recovery rate, thereby making it possible to stably recover _CO2 gas from the flue gas.

Second Embodiment
Fig. 2 is a block diagram showing the configuration of an exhaust gas treatment device 1 according to a second embodiment of the present invention. The exhaust gas treatment device 1 in Fig. 2 differs from the exhaust gas treatment device 1 in Fig. 1 in that the hydration regeneration unit 42 is omitted and water is supplied to the second chemical supply unit 22. The other configurations are the same as those in Fig. 1, and the same reference numerals are used for the same configurations.

In the second chemical supply unit 22, a metal hydroxide (magnesium hydroxide) is generated by hydration of the metal oxide (e.g., magnesium oxide) after decarbonation, and the _CO2 treatment chemical is regenerated. That is, the second chemical supply unit 22 also serves as a hydration regeneration unit. In the exhaust gas treatment device 1 of FIG. 2, the running costs required for recovering carbon dioxide in the exhaust gas can be reduced by reusing the _CO2 treatment chemical. Depending on the configuration of the exhaust gas treatment device 1, the _CO2 treatment chemical may be regenerated in the chemical tank 43.

Third Embodiment
Fig. 3 is a block diagram showing the configuration of an exhaust gas treatment device 1 according to a third embodiment of the present invention. In the exhaust gas treatment device 1 of Fig. 3, compared to the exhaust gas treatment device 1 of Fig. 1, the hydration regeneration unit 42 is omitted, and a steam supply unit 44 and a condenser 45 are added. The other configuration is the same as in Fig. 1, and the same components are denoted by the same reference numerals.

The water vapor supply unit 44 is connected to the collected material heating unit 41 and continuously supplies water vapor into the collected material heating unit 41. As described above, in the collected material heating unit 41, the collected material is heated to extract _CO2 gas from the _CO2 treatment agent after carbonation. At this time, the water vapor flowing as a sweep gas in the collected material heating unit 41 reduces the partial pressure of _CO2 gas in the collected material heating unit 41, making it possible to promote decarbonation at a relatively low temperature. In addition, hydration of the _CO2 treatment agent (mainly magnesium oxide in this case) after decarbonation with water vapor is also promoted, and the _CO2 treatment agent (magnesium hydroxide) is regenerated. In the exhaust gas treatment device 1 of FIG. 3, the collected material heating unit 41 also serves as a hydration regeneration unit. The regenerated _CO2 treatment agent is sent to the agent tank 43 and stored therein. In the collected material heating unit 41, the dehydration reaction of the unreacted _CO2 treatment agent (magnesium hydroxide) contained in the collected material is also suppressed.

On the other hand, the extracted _CO2 gas is mixed with water vapor and sent to the condenser 45. Hereinafter, the water vapor mixed with _CO2 gas is referred to as " _CO2- containing water vapor". In the condenser 45, the water contained in the _CO2- containing water vapor is condensed (i.e., condensed) by cooling. In other words, water is removed from the _CO2- containing water vapor to obtain concentrated _CO2 gas. The condenser 45 is provided with a gas extractor having a vacuum pump or the like, and the concentrated _CO2 gas is extracted by the gas extractor and stored in the _CO2 gas tank 49. The condensed water (condensate) is sent to a condensate tank not shown.

As described above, the exhaust gas treatment device 1 in Fig. 3 further includes a water vapor supply unit 44 that supplies water vapor into the collected material heating unit 41, and a separation unit (condenser 45 in the example of Fig. 3) that separates water and carbon dioxide from the carbon dioxide-containing water vapor discharged from the collected material heating unit 41. This makes it possible to promote the _CO2 generation reaction (decarbonation) by reducing the _CO2 partial pressure, promote the hydration of the _CO2 treatment agent after decarbonation (metal oxide after _CO2 desorption), and suppress dehydration of the unreacted _CO2 treatment agent in the collected material heating unit 41.

3, a gas other than water vapor may be supplied into the collected material heating section 41, and in one example, an inert gas supply section that supplies an inert gas (nitrogen, helium, argon, etc.) into the collected material heating section 41 is provided instead of the water vapor supply section 44. In this case, a separation section (for example, a separation section that separates carbon dioxide by a membrane separation method) that separates the inert gas and carbon dioxide from the carbon dioxide-containing gas discharged from the collected material heating section 41 is provided. In such an exhaust gas treatment device 1, it is possible to promote a _CO2 generation reaction (decarbonation) by reducing the _CO2 partial pressure, and it is also possible to reduce the effects of corrosion due to moisture, etc.

In addition, both an inert gas supply unit that supplies an inert gas into the collected material heating unit 41 and a water vapor supply unit 44 that supplies water vapor can be provided. In this case, a separation unit that separates the inert gas and carbon dioxide from the carbon dioxide-containing gas discharged from the collected material heating unit 41, and a separation unit that separates water and carbon dioxide are provided. By supplying these gases into the collected material heating unit 41, it is possible to promote the CO ₂ generation reaction (decarbonation). The inert gas supply unit and the water vapor supply unit 44 may be provided as a single gas supply unit, and the mixed gas may be supplied into the collected material heating unit 41. In this case, the exhaust gas treatment device 1 can also be considered to have an inert gas supply unit and a water vapor supply unit 44.

The order in which the separation section that separates inert gas and carbon dioxide, and the separation section that separates water and carbon dioxide can be installed varies depending on the technology selected, so there is no particular order. For example, a separation section that separates inert gas and carbon dioxide (PSA, zeolite membrane, etc.) could be installed after a separation section that separates water and carbon dioxide (dehumidifier, condenser, etc.), or a separation section that separates inert gas and carbon dioxide (amine membrane, device using chemical absorption method, etc.) could be installed after a separation section that separates water and carbon dioxide (condenser, etc.).

Fourth Embodiment
Fig. 4 is a block diagram showing the configuration of an exhaust gas treatment device 1 according to a fourth embodiment of the present invention, and shows only the components provided downstream of the first dust collector 31 in the flue 9 (similar to Figs. 5 and 6 described below). The exhaust gas treatment device 1 in Fig. 4 has a collected matter distribution section 46 added to it, compared to the exhaust gas treatment device 1 in Fig. 1. The other components are similar to those in Fig. 1, and the same components are denoted by the same reference numerals.

The collected matter distributor 46 is disposed between the second dust collector 32 and the collected matter heater 41. The collected matter distributor 46 has, for example, a conveyor and a gate, and while transporting the collected matter brushed off from the filter cloth of the second dust collector 32 by the conveyor, distributes and supplies the collected matter to the collected matter heater 41 and the second chemical supply unit 22 by opening and closing the gate. The distribution ratio of the collected matter may be constant, or may be changed based on the amount of the collected matter stored in the collected matter heater 41 or the second chemical supply unit 22, etc. In the collected matter heater 41, the collected matter is heated to extract _CO2 gas from the collected matter, and the _CO2 treatment chemical is regenerated by the hydration regeneration unit 42 and stored in the chemical tank 43. In the second drug supply section 22, the _CO2 treatment drug from the drug tank 43 and the collected material supplied from the collected material distribution section 46 (i.e., the collected material containing the _CO2 treatment drug after carbonation) are mixed and supplied to the second drug supply position P2.

4 , a portion of the material collected by the second dust collector 32 is supplied to the second chemical supply position P2 without passing through the material heating section 41. This makes it possible to reduce the amount of new _CO2 treatment chemical used, and therefore the running costs of the exhaust gas treatment device 1 can be reduced.

Fifth Embodiment
Fig. 5 is a block diagram showing the configuration of an exhaust gas treatment device 1 according to a fifth embodiment of the present invention. In the exhaust gas treatment device 1 of Fig. 5, a recirculation damper 52 is added compared to the exhaust gas treatment device 1 of Fig. 1. The other configuration is similar to that of Fig. 1, and the same reference numerals are used for the same configuration.

The recirculation damper 52 is provided downstream of the second dust collector 32 in the flue 9. In the recirculation damper 52, a part of the flue gas discharged from the second dust collector 32 is taken out as recirculated flue gas and returned to the upstream side of the second dust collector 32 via the recirculation line 521. The recirculation damper 52 is an exhaust gas recirculation section. Inside the second dust collector 32, the recirculated flue gas passes through a filter cloth (i.e., a filter cloth on which a _CO2 treatment agent is deposited) together with the flue gas flowing into the second dust collector 32 from the first dust collector 31. This removes the _CO2 gas contained in the flue gas and the recirculated flue gas. The flue gas not taken out by the recirculation damper 52 flows through the flue 9 toward the chimney.

As described above, in the exhaust gas treatment device 1 of FIG. 5, a portion of the exhaust gas that has passed through the second dust collector 32 is returned to the upstream side of the second dust collector 32 in the flue 9. In this way, by repeatedly passing a portion of the exhaust gas through the second dust collector 32, the carbon dioxide recovery rate in the exhaust gas treatment device 1 can be improved.

As shown in Fig. 6, both the collected matter distributor 46 and the recirculation damper 52 may be added to the exhaust gas treatment device 1. In the exhaust gas treatment device 1 of Fig. 6, the amount of a new _CO2 treatment agent used can be reduced and the carbon dioxide recovery rate can be improved.

Various modifications are possible with the exhaust gas treatment device 1.

In the above-mentioned exhaust gas treatment device 1, _CO2 gas is extracted from the _CO2 treatment agent after carbonation in the collected material heating unit 41, but from the viewpoint of removing carbon dioxide from the exhaust gas by carbonation of the _CO2 treatment agent, the collected material heating unit 41 may be omitted. In this case, the exhaust gas treatment device 1 includes a first dust collector 31 provided in the flue 9 through which the exhaust gas flows, a first chemical supply unit 21 that supplies a powdered alkaline chemical to the upstream side of the first dust collector 31 in the flue 9, a second dust collector 32 provided downstream of the first dust collector 31 in the flue 9, and a second chemical supply unit 22 that supplies a powdered chemical ( _CO2 treatment chemical) that chemically reacts with carbon dioxide to a chemical supply position P2 located between the first dust collector 31 and the second dust collector 32 in the flue 9, and the temperature of the exhaust gas in the second dust collector 32 is preferably 100 to 200 ° C. This allows the carbonation reaction of the _CO2 treatment agent to proceed efficiently, making it possible to remove a large amount of carbon dioxide from the exhaust gas.

On the other hand, from the viewpoint of selectively recovering (removing) carbon dioxide from the exhaust gas, it is important that the exhaust gas treatment device 1 is provided with a collected material heating section 41 that removes _CO2 gas from the _CO2 treatment chemical after carbonation. In this case, even if the first dust collector 31 and the first chemical supply section 21 are omitted, the _CO2 gas contained in the exhaust gas is absorbed to a certain extent by the _CO2 treatment chemical in the second dust collector 32. Then, the _CO2 gas is removed from the _CO2 treatment chemical by the collected material heating section 41.

The first dust collector 31 and the second dust collector 32 may be dust collectors other than bag filters, such as electrostatic dust collectors or cyclones.

Regeneration and reuse of the _CO2 treatment agent contained in the capture product may only be performed on an as-needed basis.

The exhaust gas treatment device 1 may also be used in facilities other than incineration facilities, such as thermal power plants.

The configurations in the above embodiment and each modified example may be combined as appropriate as long as they are not mutually inconsistent.

Reference Signs List 1 Exhaust gas treatment device 9 Flue 21 First chemical supply section 22 Second chemical supply section 31 First dust collector 32 Second dust collector 41 Collected material heating section 44 Steam supply section 45 Condenser P2 Second chemical supply position

Claims (11)

An exhaust gas treatment device,
A dust collector installed in a flue through which exhaust gas flows;
A chemical supply unit that supplies a powdered chemical that chemically reacts with carbon dioxide to a chemical supply position located upstream of the dust collector in the flue;
a collected matter heating unit that recovers the collected matter collected by the dust collector and heats the collected matter to a temperature at which carbon dioxide is extracted from the agent;
An exhaust gas treatment device comprising: The exhaust gas treatment device according to claim 1,
Another dust collector provided upstream of the chemical supply position in the flue;
Another chemical supply unit that supplies a powdered alkaline chemical to the upstream side of the other dust collector in the flue;
The exhaust gas treatment device further comprising: The exhaust gas treatment device according to claim 2,
The exhaust gas treatment device according to claim 1, wherein the collected material heated in the collected material heating section is regenerated as the chemical agent and reused in the chemical agent supplying section. The exhaust gas treatment device according to claim 3,
The exhaust gas treatment device according to claim 1, wherein the chemical agent is a metal hydroxide, and the collected material is regenerated as the chemical agent by a hydration reaction of the collected material heated in the collected material heating section. The exhaust gas treatment device according to any one of claims 1 to 4,
a water vapor supplying section for supplying water vapor into the collected material heating section;
A separation section that separates water and carbon dioxide from the carbon dioxide-containing water vapor discharged from the collected material heating section;
The exhaust gas treatment device further comprising: The exhaust gas treatment device according to any one of claims 1 to 4,
an inert gas supply unit for supplying an inert gas into the collected material heating unit;
a separation section that separates an inert gas and carbon dioxide from the carbon dioxide-containing gas discharged from the collected material heating section;
The exhaust gas treatment device further comprising: The exhaust gas treatment device according to any one of claims 1 to 4,
a water vapor supplying section for supplying water vapor into the collected material heating section;
an inert gas supply unit for supplying an inert gas into the collected material heating unit;
a separation section that separates water and carbon dioxide from the gas discharged from the collected material heating section;
Another separation section for separating an inert gas and carbon dioxide from the gas;
The exhaust gas treatment device further comprising: The exhaust gas treatment device according to any one of claims 1 to 4,
The exhaust gas treatment device is characterized in that the temperature of the exhaust gas in the dust collector is 100 to 200°C. The exhaust gas treatment device according to any one of claims 1 to 4,
2. An exhaust gas treatment device comprising: a part of the matter collected by the dust collector being supplied to the chemical supply position without passing through the collected matter heating section. The exhaust gas treatment device according to any one of claims 1 to 4,
An exhaust gas treatment device, characterized in that a portion of the exhaust gas that has passed through the dust collector is returned to the upstream side of the dust collector in the flue. An exhaust gas treatment device,
A first dust collector provided in a flue through which exhaust gas flows;
A first chemical supply unit that supplies a powdered alkaline chemical to the upstream side of the first dust collector in the flue;
A second dust collector provided downstream of the first dust collector in the flue;
A second chemical supply unit that supplies a powdered chemical that chemically reacts with carbon dioxide to a chemical supply position located between the first dust collector and the second dust collector in the flue;
Equipped with
The exhaust gas treatment device is characterized in that the temperature of the exhaust gas in the second dust collector is 100 to 200°C.

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