JP4775858B2 - Method for regenerating copper-based absorbent and method for removing mercury from source gas - Google Patents

Description

  The present invention relates to a method and a raw material for recycling a used copper-based absorbent in which mercury contained in a raw material gas is absorbed by contacting a raw material gas containing mercury such as a gasified gas such as coal produced by gasifying coal. The present invention relates to a method for removing mercury in gas.

  Coal exists in a large area of the world, has a large amount of recoverable reserves, and has a stable price, so it plays an important role in securing energy and stabilizing energy prices. High-efficiency power generation using gas with high stability of supply and low price per calorific value, and using the resulting coal gasification gas as fuel for power generation equipment such as gas turbines, fuel cells, and gas engines Various techniques have been proposed (see, for example, Patent Document 1). However, the coal gasification gas contains impurities that adversely affect the power generation equipment and the environment, and it is indispensable to realize these high-efficiency power generation technologies in advance.

  Coal may contain a small amount of mercury, and when such coal is gasified, mercury may also be vaporized and mixed into the coal gasification gas as impurities. Since mercury has a high vapor pressure and cannot be removed by filtration with a filter or the like, a remover that absorbs or adsorbs mercury is used. As a method for removing mercury contained in combustion exhaust gas having a temperature from room temperature to several tens of degrees, a method using activated carbon as a remover is known. Moreover, as a technique for absorbing mercury contained in a high-temperature gasification gas, a precipitate produced by a precipitation method from a solution containing copper is filtered, washed and dried, and further heated once at 150 ° C. to 400 ° C. A method using a copper-based absorbent mainly composed of copper, such as a gaseous mercury removing agent containing the obtained gaseous mercury-absorbing substance (see, for example, Patent Document 2) has been proposed. This copper-based absorbent absorbs mercury contained in the gasification gas by contacting coal gasification gas, biomass gasification gas, or the like, and removes mercury from the gasification gas or the like. Since the copper-based absorbent has an amount capable of absorbing mercury, that is, an absorption capacity, the mercury absorption performance is gradually lost with the use of mercury removal. For this reason, the copper-based absorbent whose mercury absorption performance has been lost is replaced with a new copper-based absorbent. However, since a method for regenerating the copper-based absorbent has not been established, the used copper-based absorbent is discarded, and there is a problem that a large amount of waste containing mercury is generated. The problem of consuming new copper-based absorbents arises, which is a problem in terms of increasing the production and processing costs of copper-based absorbents and effectively using resources. Such a problem exists not only in the coal gasification gas but also in other source gases containing mercury.

JP 2000-48844 A JP 2005-161255 A

  In view of such circumstances, an object of the present invention is to provide a method for regenerating a copper-based absorbent that can regenerate a used copper-based absorbent whose mercury absorption performance has been lost by use.

  As a result of studies conducted by the present inventors to solve the above-mentioned problems, the used copper-based absorbent that has absorbed mercury in the raw material gas has an atmosphere containing oxygen after the steam treatment in which the treatment is performed in an atmosphere containing steam. It was found that by performing an oxidation treatment in which the mercury can be absorbed again, the present invention was completed.

  In the first aspect of the present invention, the used copper-based absorbent that has absorbed mercury contained in the raw material gas by contacting the raw material gas containing mercury with the copper-based absorbent has a temperature of the used copper-based absorbent. After the steam treatment in which the mercury is released from the used copper-based absorbent by treatment in an atmosphere containing steam at a temperature of 240-300 ° C., the temperature of the used copper-based absorbent is 240-300 ° C. The present invention provides a method for reclaiming a copper-based absorbent, characterized in that the treatment is performed in an atmosphere containing oxygen to oxidize the used copper-based absorbent.

  In such a first aspect, after the treatment of the spent copper absorbent in an atmosphere containing water vapor at a temperature of 240 to 300 ° C. to release mercury, the spent copper absorbent in an atmosphere containing oxygen is used. By treating and oxidizing the agent at a temperature of 240 to 300 ° C., the used copper-based absorbent can be regenerated so that it can absorb mercury again. As a result, the regenerated copper-based absorbent can be used again for removing mercury in the raw material gas, so the amount of used copper-based absorbent waste and the amount of new copper-based absorbent used must be reduced. Can do.

  A second aspect of the present invention is the copper-based absorbent regeneration method according to the first aspect, wherein the raw material gas is a coal gasification gas generated by gasifying coal. .

  In the second aspect, the copper-based absorbent for coal gasification gas that absorbs mercury from the coal gasification gas can be regenerated.

  The third aspect of the present invention is characterized in that the used copper-based absorbent absorbs mercury in the raw material gas by contacting the raw material gas substantially free of sulfur compounds and halides. The method for regenerating a copper-based absorbent according to the first or second aspect.

  In the third aspect, since the raw material gas does not substantially contain a sulfur compound and a halide, the copper-based absorbent used for removing mercury in the raw material gas is metallic copper. The mercury absorption performance can be recovered by converting the used copper-based absorbent into an oxide after removing the mercury from the used copper-based absorbent.

  According to a fourth aspect of the present invention, the used copper-based absorbent is a catalyst that absorbs mercury in the raw material gas by contacting the raw material gas at 160 to 220 ° C. 3. The method for regenerating a copper-based absorbent according to any one of the aspects 3.

  In the fourth aspect, it is possible to regenerate the copper-based absorbent used in the system for removing mercury from the raw material gas at a higher temperature than when using a conventional activated carbon of 160 to 220 ° C. as the remover.

  According to a fifth aspect of the present invention, the copper-based absorbent is an absorbent containing only a copper compound, or a copper compound and a carrier component, or a molding aid, and is contained in an unused copper-based absorbent. The copper compound is copper oxide or metal copper, and is in the method for regenerating a copper-based absorbent according to any one of the first to fourth aspects.

  In the fifth aspect, the copper compound alone, or an absorbent containing a copper compound and a carrier component or a molding aid, and the copper compound contained in the unused copper-based absorbent is copper oxide or metallic copper. The system absorbent can be regenerated.

  In the sixth aspect of the present invention, after the raw material gas is brought into contact with the copper-based absorbent and mercury in the raw material gas is absorbed by the copper-based absorbent, the used copper-based absorbent that has absorbed the mercury is used. A raw material gas which is regenerated by the method for regenerating a copper-based absorbent according to any one of the first to fifth aspects and contacts the regenerated spent copper-based absorbent with the raw material gas again to absorb mercury. It is in the mercury removal method.

  In the sixth aspect, the waste and usage amount of the copper-based absorbent is reduced by regenerating the used copper-based absorbent that has absorbed the mercury in the raw material gas and using it again for removing the mercury in the raw material gas. Can be reduced.

Hereinafter, the present invention will be described in more detail.
The copper-based absorbent to be regenerated by the regeneration method of the present invention is made by contacting a source gas containing mercury at a concentration higher than 0.1 μg / m ³ N at, for example, 160 to 220 ° C. Absorbed copper-based absorbent. In the present specification, a copper-based absorbent whose mercury absorption performance is lost by contacting the raw material gas to absorb mercury is referred to as a used copper-based absorbent. The copper-based absorbent may be an absorbent mainly composed of copper, for example, an absorbent containing only a copper compound, or a copper compound and a carrier component, or a molding aid, and unused copper. Examples of the copper compound contained in the system absorbent include copper oxide and metallic copper. Examples of the carrier component include alumina, silica, titania, zirconia, zeolite, and glass fiber. Further, examples of the molding aid include ethylene glycol and clay mineral. Although the manufacturing method of a copper-type absorber is not specifically limited, For example, as a specific example of the manufacturing method of the copper-type absorber which consists of a copper oxide and a support component (silica), the aqueous solution of copper chloride, copper sulfate, or copper nitrate is used. Examples thereof include a method in which a sodium hydroxide aqueous solution is added to a mixed aqueous solution to which silica sol is added, and the resulting precipitate is filtered, washed, dried and fired.

  The raw material gas is not particularly limited as long as it contains mercury. For example, coal gasification gas generated by gasifying coal, heavy oil, sludge, biomass, waste, etc. are gasified. Various gasification gases produced by the above method can be mentioned. In particular, the method for regenerating a copper-based absorbent of the present invention can be suitably applied to a copper-based absorbent that has absorbed mercury in a raw material gas that is substantially free of sulfur compounds and halides. Note that the source gas substantially free of sulfur compounds and halides means that when the concentration of sulfur compounds and halides in the source gas absorbs mercury from the source gas, the copper-based absorbent is copper sulfide or halogenated. It means that it is not to become copper. For example, the concentration of the sulfur compound is 1 ppm or less and the concentration of the halide is 1 ppm or less. Of course, a raw material gas containing no sulfur compound and halide may be used.

  In the method for regenerating a copper-based absorbent according to the present invention, first, a used copper-based absorbent is used after being treated in an atmosphere containing water vapor at a temperature of the used copper-based absorbent of 240 to 300 ° C. Mercury is released from the copper-based absorbent to remove mercury from the used copper-based absorbent. In this way, mercury is removed from the used copper-based absorbent by placing the used copper-based absorbent in an atmosphere containing water vapor and setting the temperature of the used copper-based absorbent to 240 to 300 ° C. The release is called steam treatment. In addition, mercury may be completely released from the used copper-based absorbent by this steam treatment, but the absorbed mercury may not be completely released, for example, 90% by weight or more of the absorbed mercury. Should just be released.

  The water vapor treatment may be performed in an atmosphere containing water vapor, but for example, it is preferably performed in a nitrogen gas atmosphere containing about 1 to 20% (volume) of water vapor. In addition, it is necessary to perform in the atmosphere which does not contain oxygen.

The steam treatment temperature needs to be such that the temperature of the used copper-based absorbent is 240 to 300 ° C. This is because if it is less than 240 ° C., mercury cannot be sufficiently released from the used copper-based absorbent, and the mercury absorption performance cannot be recovered. On the other hand, when the temperature is higher than 300 ° C., the copper-based absorbent may be sintered and deteriorated, and the mercury absorption performance may be deteriorated. The temperature of the used copper-based absorbent can be adjusted by the temperature of the processing gas such as water vapor or nitrogen, the temperature setting of the reaction vessel, or the like.
The steam treatment time is not particularly limited as long as mercury can be released from the copper-based absorbent.

Thereafter, the used copper-based absorbent is treated in an atmosphere containing oxygen so that the temperature of the used copper-based absorbent becomes 240 to 300 ° C., and the used copper-based absorbent is oxidized to form copper oxide (CuO, Cu ₂ O, etc.). To be. In this manner, the used copper-based absorbent is oxidized by placing the used copper-based absorbent in an atmosphere containing oxygen and setting the temperature of the used copper-based absorbent to 240 to 300 ° C. This is called oxidation treatment. The mercury absorption performance that absorbs mercury in the raw material gas and removes mercury from the raw material gas is restored by converting the used copper-based absorbent into an oxide after releasing the mercury of the used copper-based absorbent by steam treatment. can do. In detail, first, when a raw material gas containing mercury is brought into contact with a copper-based absorbent, the copper-based absorbent absorbs and removes mercury in the raw material gas, but the copper-based absorbent can absorb mercury. Due to the quantity, i.e. absorption capacity, the mercury absorption performance is gradually lost with the use for mercury removal. At the same time, part of the copper present as copper oxide is reduced by the source gas to become metallic copper (Cu), and its mercury absorption capacity is lower than that of copper oxide. descend. When this used copper-based absorbent is treated in an atmosphere containing water vapor at a temperature of 240 to 300 ° C., mercury absorbed from the raw material gas is released (water vapor treatment). After releasing mercury by steam treatment, if the temperature of the used copper-based absorbent is set to 240 to 300 ° C. in an atmosphere containing oxygen, mercury remaining after the steam treatment is released, and metal The copper compound in the used copper-based absorbent that has become copper is oxidized to become copper oxide. As a result, mercury absorption performance can be recovered.

  It should be noted that the used copper is not a two-step treatment in which an oxidation treatment is performed after the steam treatment as in the copper absorbent regenerating method of the present invention, but in a one-step treatment in an atmosphere containing water vapor and oxygen. It is not possible to recover the mercury absorption performance of the system absorbent well. This is presumably because the oxidation of metallic copper contained in the used copper-based absorbent proceeds rapidly, and mercury in the absorbent is taken in without being released. Further, in the regeneration using only the steam treatment, if mercury removal and regeneration of the source gas are repeated, the mercury-absorbing performance of the copper-based absorbent gradually decreases. This is presumably because in the regeneration using only the steam treatment, the copper compound contained in the copper-based absorbent remains metallic copper, and its mercury absorption performance is lower than that of copper oxide.

  The oxidation treatment may be performed in an atmosphere containing oxygen. For example, it may contain water vapor or nitrogen, but is preferably performed in a gas atmosphere containing, for example, about 0.5 to 20% (volume) of oxygen.

  The oxidation treatment temperature needs to be such that the temperature of the used copper-based absorbent is 240 to 300 ° C. This is because if the temperature is less than 240 ° C., the used copper-based absorbent cannot be sufficiently oxidized and the mercury absorption performance cannot be recovered. On the other hand, when the temperature is higher than 300 ° C., the copper-based absorbent may be sintered and deteriorated, and the mercury absorption performance may be deteriorated. The temperature of the used copper-based absorbent can be adjusted by the temperature of the processing gas such as oxygen or water vapor, the temperature setting of the reaction vessel, the oxygen concentration of the gas to be oxidized, or the like.

  The oxidation treatment time is not particularly limited as long as it can oxidize the used copper-based absorbent that has been subjected to the steam treatment.

The copper-based absorbent regenerated by the method for regenerating a copper-based absorbent of the present invention, as shown in the examples described later, is used with respect to raw material gas containing mercury such as coal gasification gas. Mercury absorption performance comparable to that of a system absorbent. That is, the copper-based absorbent regenerated by the regeneration method of the present invention has sufficient mercury absorption performance, so that it can be used again as a copper-based absorbent for removing mercury in the raw material gas. Specifically, as shown in FIG. 1, a raw material containing mercury as shown in FIG. 1, which shows a method of repeatedly using a copper-based absorbent by sequentially removing mercury in a raw material gas and regenerating a used copper-based absorbent. A purified gas (for example, mercury concentration Hg: 0.1 μg / m ³ _N or less) is obtained by bringing the gas into contact with a copper-based absorbent at, for example, 160 to 220 ° C., and absorbing mercury in the raw material gas into the copper-based absorbent. After the mercury removal, the used copper-based absorbent that has absorbed the mercury by removing the mercury is regenerated by the method for regenerating a copper-based absorbent of the present invention. Specifically, the used copper-based absorbent is steam-treated and then oxidized. Then, mercury is removed from the raw material gas by removing the mercury from the raw material gas by bringing the raw material gas into contact with the spent copper-based absorbent regenerated by the steam treatment and the oxidation treatment to absorb mercury. In this way, the amount of waste and the amount of copper-based absorbent used to remove mercury in the raw material gas is reduced by regenerating the copper-based absorbent and repeatedly using it to remove mercury in the raw material gas. can do.

  The copper-based absorbent regeneration method of the present invention uses a raw material gas such as coal, heavy oil, sludge, biomass, waste, and other gasification gas as a fuel gas for power generation equipment such as a gas turbine, a fuel cell, and a gas engine. It can be applied to mercury removal equipment for power generation facilities. A power generation facility using a mercury removing apparatus that removes mercury from a raw material gas using a copper absorbent regenerated by the copper absorbent regenerating method of the present invention will be described below. An example of coal gasification combined power generation (IGCC), which uses coal gasification gas produced in a coal gasification furnace as raw material gas, burns the raw material gas to drive the gas turbine, and drives the steam turbine by the generated heat. To do.

FIG. 2 shows a schematic system of an integrated coal gasification combined cycle (IGCC) system equipped with a dry gas purification system. In addition, FIG. 2 is equipped with the mercury removal apparatus from coal gas which does not contain a sulfur compound and a halide substantially. As shown in FIG. 2, a raw material gas (coal gasification gas) containing mercury, dust, sulfur compounds and halides obtained by burning and gasifying coal in a coal gasification furnace 1 is cooled by a gas cooler. After that, dust is removed by the filter 2 (operation temperature 400 ° C. to 600 ° C.). The source gas from which the dust has been removed by the filter 2 is removed by absorbing halides such as HCl and HF by the halide removing device 3 filled with a sodium-based absorbent (operation temperature 400 ° C. to 500 ° C. ). The raw material gas from which the halide has been removed is sent to a desulfurization apparatus 4 filled with a desulfurizing agent, and sulfur compounds such as H ₂ S and COS are absorbed and removed (operation temperature 400 ° C. to 500 ° C.). In addition, the raw material gas which passed through the halide removal apparatus 3 and the desulfurization apparatus 4 does not contain a halide and a sulfur compound substantially.

  Next, the raw material gas from which dust, halides and sulfur compounds have been removed is lowered in temperature by the heat exchanger 5 and then sent to a mercury removing device 6 filled with a copper-based absorbent to remove mercury vapor. (Operating temperature 160 ° C to 220 ° C).

  The raw material gas from which mercury has been removed by the mercury removing device 6 is heated by the heat exchanger 5 and then sent to the gas turbine 21 as fuel gas. The fuel gas is burned together with the compressed air in the gas turbine 21 to drive the combustion turbine, and the combustion gas obtained by burning the unburned components in the catalytic combustor 22 is introduced into the expansion turbine 23 to drive the expansion turbine. The generator 24 is activated to generate power.

  High-temperature exhaust gas from the expansion turbine 23 is sent to an exhaust heat recovery boiler (HRSG) 25 to recover heat and generate steam. Then, the steam generated in the exhaust heat recovery boiler 25 is sent to the steam turbine 26, and the generator 27 is operated by the driving of the steam turbine 26 to generate power. Further, the exhaust gas heat recovered by the exhaust heat recovery boiler 25 is discharged from the chimney 28.

  In the dry gas purification system shown in FIG. 2, dust is filtered and removed by the filter 2, halide is removed by the halide removal device 3, sulfur compounds are removed by the desulfurization device 4, and mercury vapor is removed by the mercury removal device. 6 is removed. Thereby, the raw material gas which gasified coal can be applied to the fuel gas of the gas turbine 21, and it can refine | purify to the level which can discharge | emit the gas after combustion from a chimney as it is.

  In FIG. 2, when removing the mercury from the raw material gas by bringing the raw material gas into contact with the copper-based absorbent 12, the used copper-based absorbent that absorbs the mercury from the raw material gas and loses the mercury absorption performance. 12 is extracted from the mercury removing device 6 and regenerated by the above-described method for regenerating a copper-based absorbent of the present invention to recover the mercury absorption performance. The mercury removing device 6 is filled again and used. Since the copper-based absorbent is regenerated and reused in this way, the amount of waste and the amount of copper-based absorbent 12 used when removing mercury from the source gas can be reduced. Note that the steam and oxygen necessary for the method for regenerating a copper-based absorbent according to the present invention include coal gasification combined power generation such as steam generated in the exhaust heat recovery boiler 25 and oxygen produced by a gasifier air separator. An existing utility can be used in the system, and the present invention can be implemented without providing a new device.

  In the above example, a method of once removing the used copper-based absorbent 12 from the mercury removing device 6 and regenerating at a place other than the mercury removing device 6 is shown. The mercury removal device 6 may be regenerated while being filled with the copper-based absorbent by a method such as alternate use by path switching. As shown in the examples to be described later, in the copper-based absorbent regeneration method of the present invention, the mercury absorption performance can be completely recovered in a shorter time, for example, about 80 minutes, than the time that can be used for removing mercury from the source gas. By switching the flow path of the raw material gas when the mercury removing device filled with the regenerated copper-based absorbent is put on standby and the performance of the mercury removing device used for removing the raw material gas begins to deteriorate, Mercury can be continuously removed from the source gas.

  Further, in the dry gas purification system of FIG. 2, the filter 2, the halide removing device 3, the desulfurizing device 4, and the mercury removing device 6 are shown in this order from the upstream side. However, mercury may be removed from coal gas containing sulfur compounds and halides. For example, as shown in FIG. 3, from the upstream side, filter 2, mercury removing device 6, halide removing device 3, desulfurization is performed. The device 4 may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples at all.

Example 1
<Preparation of copper absorbent>
To the aqueous solution of copper nitrate trihydrate (2 mol / L), an amount that makes the silica content of the absorbent capable of obtaining a silica sol about 30% by weight was added. When the mixed aqueous solution was heated to about 60 ° C., an aqueous sodium hydroxide solution (4 mol / L) was added little by little until the pH of the aqueous solution became weakly alkaline while stirring. The produced precipitate was filtered, washed, dried and fired to prepare a copper-based absorbent composed of copper oxide and silica components.

<Mercury removal with unused copper-based absorbent>
Simulated raw material gas (gas composition is H ₂ : 8%, CO: 20) assuming coal gasification gas at 220 ° C. and atmospheric pressure (0.1 MPa) to 2 g of the unused copper-based absorbent prepared above. %, CO ₂ : 5%, H ₂ O: 5%, N ₂ : balance, Hg: 62 μg / m ³ N) at a source gas flow rate of 1.0 L / min to bring mercury in the source gas into copper Absorbed in a system absorbent. Note that a part of the copper compound contained in the used copper-based absorbent that absorbed mercury in the raw material gas was metallic copper. The time (elapsed time) when the copper-based absorbent and the raw material gas were contacted, the total amount of mercury absorbed by the copper-based absorbent (mercury absorption amount), and the mercury concentration in the raw material gas after passing through the copper-based absorbent The relationship with (exit mercury concentration) is shown in FIG. In FIG. 4, the thick line indicates the mercury absorption amount, and the thin line indicates the outlet mercury concentration.
As shown in FIG. 4, the outlet mercury concentration increased with the passage of time, and reached about 58 μg / m ³ N at 590 minutes. Since the mercury concentration of the raw material gas before removing mercury was 62 μg / m ³ N, the copper-based absorbent at the elapsed time of 590 minutes had almost lost its mercury absorption performance. It was confirmed that it became an agent. Further, the amount of mercury absorbed from the raw material gas by the copper-based absorbent during the mercury removal was about 21 μg.

<Regeneration of used copper absorbent>
Next, the used copper-based absorbent that has absorbed mercury in the raw material gas is placed in a gas (H ₂ O: 10% and N ₂ : balance) containing water vapor and nitrogen, and used. Mercury was released so that the temperature of the used copper-based absorbent was 260 ° C. (water vapor treatment). The regeneration gas flow rate was 1.0 L / min and the atmospheric pressure (0.1 MPa).
Thereafter, the used copper-based absorbent subjected to the steam treatment is placed in a gas containing oxygen (H ₂ O: 10%, O ₂ : 10%, and N ₂ : balance), and the temperature of the used copper-based absorbent is set. Was oxidized at 260 ° C. (oxidation treatment). The used copper-based absorbent that was subjected to this oxidation treatment at a regeneration gas flow rate of 1.0 L / min and atmospheric pressure (0.1 MPa) was copper oxide (CuO, Cu ₂ O, etc.).
The time (elapsed time) when the copper-based absorbent was steamed and oxidized, the total amount of mercury released by the copper-based absorbent (mercury released), and the mercury concentration in the gas that passed through the copper-based absorbent (exit mercury concentration) 5) is shown in FIG. In FIG. 5, the thick line indicates the amount of mercury released, and the thin line indicates the outlet mercury concentration. Further, (1) shows the result of the steam treatment, and (2) shows the result of the oxygen treatment.
As shown in FIG. 5, mercury absorbed by the used copper-based absorbent by the water vapor treatment was released at a concentration exceeding a maximum of 800 μg / m ³ N, and a slight amount of mercury was released by the subsequent oxidation treatment. The total amount of mercury released was about 20 μg, and it was confirmed that 95% or more of the mercury absorbed by the copper-based absorbent was released.

(Example 2)
<Mercury removal with recycled used copper-based absorbent>
Simulated raw material gas (gas composition is assumed to be coal gasification gas at 220 ° C. and atmospheric pressure (0.1 MPa) at 2 g of the used copper-based absorbent that has been subjected to steam treatment and oxidation treatment obtained in Example 1. H ₂ : 8%, CO: 20%, CO ₂ : 5%, H ₂ O: 5%, N ₂ : balance, Hg: 62 μg / m ³ N) are brought into contact at a raw material gas flow rate of 1.0 L / min. The mercury in the raw material gas was absorbed by the used copper-based absorbent. The time (elapsed time) when the spent copper-based absorbent and the raw material gas are contacted, the total amount of mercury absorbed by the copper-based absorbent (mercury absorption amount), and the raw material gas after passing through the copper-based absorbent. FIG. 6 shows the relationship with the mercury concentration (exit mercury concentration). In FIG. 6, the thick line indicates the mercury absorption amount, and the thin line indicates the outlet mercury concentration.
As shown in FIG. 6, the behavior of the used copper-based absorbent (Example 2) regenerated by the copper-based absorbent regeneration method of the present invention is almost the same as that of the unused copper-based absorbent shown in FIG. The mercury absorption performance was fully recovered.

(Comparative Example 1)
Instead of the used copper-based absorbent obtained by performing the water vapor treatment and the oxidation treatment obtained in Example 1 in this order, the example except that only the water vapor treatment was performed and the oxidation treatment was not performed during the regeneration of the used copper-based absorbent. The operation of Example 2 was performed using a used copper-based absorbent similar to that in Example 1.
Specifically, a used copper-based absorbent that absorbs mercury in the raw material gas is placed in a gas containing water vapor and water vapor (H ₂ O: 10%, N ₂ : balance) and used. Mercury was released so that the temperature of the copper absorbent was 240 ° C. (water vapor treatment). The gas flow rate was 1.0 L / min and atmospheric pressure (0.1 MPa).
The time (elapsed time) when the copper-based absorbent was steam-treated, the total amount of mercury released by the copper-based absorbent (mercury release amount), and the mercury concentration in the gas that passed through the copper-based absorbent (exit mercury concentration) The relationship is shown in FIG. In FIG. 7, the thick line indicates the amount of released mercury, and the thin line indicates the outlet mercury concentration. As shown in FIG. 7, mercury absorbed by the used copper-based absorbent by the steam treatment was released at a concentration exceeding 650 μg / m ³ N at maximum. The total amount of mercury released was about 19 μg, and it was confirmed that 90% or more of the mercury absorbed by the copper-based absorbent was released.
Simulated raw material gas (gas composition is H ₂ :) assuming a coal gasification gas at 220 ° C. and atmospheric pressure (0.1 MPa) to 2 g of the used copper-based absorbent that was not oxidized only by the steam treatment. 8%, CO: 20%, CO ₂ : 5%, H ₂ O: 5%, N ₂ : balance, Hg: 62 μg / m ³ N) at a source gas flow rate of 1.0 L / min, Mercury in the gas was absorbed into the used copper-based absorbent. The time (elapsed time) when the spent copper-based absorbent and the raw material gas are contacted, the total amount of mercury absorbed by the copper-based absorbent (mercury absorption amount), and the raw material gas after passing through the copper-based absorbent. FIG. 8 shows the relationship with the mercury concentration (exit mercury concentration). In FIG. 8, the thick line indicates the mercury absorption amount, and the thin line indicates the outlet mercury concentration.
As shown in FIG. 8, in Comparative Example 1 in which regeneration was not performed by only steam treatment as regeneration, mercury was absorbed again, but the mercury concentration increased from an earlier elapsed time compared to unused copper-based absorbent. It became about 65 μg / m ³ N in 370 minutes. During the mercury removal, the amount of mercury absorbed by the copper-based absorbent from the raw material gas was about 14 μg, and the mercury absorption capacity was reduced to about 70% compared to the unused copper-based absorbent. That is, the mercury absorption performance of the used mercury absorbent could not be completely recovered by only the steam treatment.
After that, the second regeneration was performed only by the steam treatment, and the source gas was removed again from the copper-based absorbent that had undergone the second regeneration. The results are shown in FIG. As shown in FIG. 9, the mercury absorption performance is further reduced to about 60 μg / m ³ N after 170 minutes, and the amount of mercury absorbed by the copper-based absorbent from the raw material gas during the mercury removal is as follows. The mercury absorption performance was further reduced by about 7 μg.

(Comparative Example 2)
Rather than performing the water vapor treatment and the oxidation treatment shown in Example 1 stepwise, the same operation as in Example 1 was performed except that the oxidation treatment and the water vapor treatment were performed simultaneously.
Specifically, used copper-based absorbent that has absorbed mercury in the raw material gas is in a gas containing oxygen, nitrogen and water vapor (H ₂ O: 5%, O ₂ : 4%, N ₂ : balance). Then, mercury was released so that the temperature of the used copper-based absorbent became 240 ° C. The gas flow rate was 1.0 L / min and atmospheric pressure (0.1 MPa).
The time (elapsed time) when the copper-based absorbent was oxidized and steamed simultaneously, the total amount of mercury released by the copper-based absorbent (mercury released), and the regeneration gas after passing through the copper-based absorbent FIG. 10 shows the relationship with the mercury concentration (exit mercury concentration). In FIG. 10, the thick line indicates the mercury emission amount, and the thin line indicates the outlet mercury concentration. As shown in FIG. 10, mercury absorbed by the used copper-based absorbent was released at a concentration exceeding a maximum of 950 μg / m ³ N, but the concentration immediately decreased. The total amount of mercury released was about 7 μg, and only about 33% of the mercury absorbed by the copper-based absorbent was released, and the mercury could not be released sufficiently. That is, it has been found that when the steam treatment and the oxidation treatment are performed simultaneously, mercury remains in the used copper-based absorbent, and the used copper-based absorbent cannot be regenerated.

  The present invention can be used in an industrial field in which mercury is removed from a raw material gas containing mercury such as coal gasification gas.

It is a figure which shows the mercury removal method in source gas. 1 is a schematic system diagram of a dry gas purification system for coal gasification combined power generation. 1 is a schematic system diagram of a dry gas purification system for coal gasification combined power generation. It is a figure which shows the behavior which removes mercury from raw material gas using an unused copper-type absorber. It is a figure which shows the mercury release behavior in the reproduction | regeneration processing of the copper-type absorber of Example 1. FIG. It is a figure which shows the behavior which removes mercury from source gas using the copper-type absorber of Example 2. It is a figure which shows the mercury release behavior in the reproduction | regeneration processing of the copper-type absorber of the comparative example 1. FIG. It is a figure which shows the behavior which removes mercury from source gas using the copper-type absorber of the comparative example 1. It is a figure which shows the behavior which removes mercury from source gas using the copper-type absorber reproduced | regenerated twice of the comparative example 1. FIG. It is a figure which shows the mercury release behavior in the reproduction | regeneration process of the copper type absorber of the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coal gasifier 2 Filter 3 Halide removal apparatus 4 Desulfurization apparatus 5 Heat exchanger 6 Mercury removal apparatus 12 Copper type absorbent 21 Gas turbine 22 Catalytic combustor 23 Expansion turbine 24, 27 Generator 25 Waste heat recovery boiler 26 Steam Turbine 28 Chimney

Claims (5)

The used copper-based absorbent that has absorbed mercury in the raw material gas by bringing the raw material gas containing mercury into contact with a copper-based absorbent mainly composed of copper oxide and capable of absorbing mercury is used as the temperature of the used copper-based absorbent. being a ratio of 240 to 300 ° C., after steam treated in an atmosphere containing no unrealized oxygen steaming to release mercury from the used copper sorbent, temperature of the used copper sorbent A method for reclaiming a copper-based absorbent, characterized by performing an oxidation treatment by oxidizing the used copper-based absorbent by treatment in an atmosphere containing oxygen at a temperature of 240 to 300 ° C.   The method for regenerating a copper-based absorbent according to claim 1, wherein the raw material gas is a coal gasification gas generated by gasifying coal. 3. The copper-based absorbent according to claim 1, wherein the used copper-based absorbent is one that absorbs mercury in the raw material gas by contacting the raw material gas at 160 to 220 ° C. 3. How to play. The copper-based absorbent is an absorbent containing only a copper compound, or a copper compound and a carrier component, or a molding aid, and the copper compound contained in an unused copper-based absorbent contains metallic copper. The method for regenerating a copper-based absorbent according to any one of claims 1 to 3 . The raw material gas is brought into contact with a copper-based absorbent and mercury in the raw material gas is absorbed by the copper-based absorbent, and then the used copper-based absorbent that has absorbed the mercury is any one of claims 1 to 4. A method for removing mercury in a raw material gas, comprising regenerating the copper-based absorbent as described in the above item, and bringing the raw material gas into contact with the regenerated used copper-based absorbent again to absorb mercury.

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