JP5106479B2 - Method and apparatus for suppressing mercury re-release in desulfurization equipment - Google Patents

Description

  The present invention relates to a method for suppressing mercury re-emission from a desulfurization apparatus, which is achieved by absorbing and removing divalent mercury from boiler exhaust gas containing metallic mercury and divalent mercury together with sulfur oxide, hydrogen chloride, hydrogen fluoride and the like. And the apparatus.

  In order to prevent air pollution, wet limestone-gypsum desulfurization devices have been widely put into practical use as devices for removing sulfur oxides in exhaust gas. FIG. 5 shows the structure and system of the internal oxidation system of this desulfurization apparatus. Exhaust gas 1 from a boiler or the like is introduced from the gas inlet duct 3 into the desulfurization apparatus 4a, and from a spray nozzle 6a installed in the absorbent liquid spray section 5 via a spray header 9 installed in the desulfurization apparatus 4a from the absorbent liquid circulation pipe 19. By contacting the droplets of the absorbent to be sprayed, the sulfur oxides in the exhaust gas 1 are absorbed on the surface of the spray droplets together with the soot, hydrogen chloride, hydrogen fluoride and other acidic gases in the exhaust gas 1. The mist accompanying the gas is removed by the mist eliminator 10, and the clean exhaust gas 2 is reheated as necessary through the gas outlet duct 11 and discharged from the chimney.

  Limestone 15 which is an absorbent of sulfur oxide is converted into limestone slurry in a limestone slurry tank 16, and is supplied by a limestone slurry pump 17 from the absorbent supply pipe 20 into the desulfurization apparatus 4a by a flow control valve 18a according to the amount of sulfur oxide absorbed. The The absorption liquid is pressurized by the desulfurization apparatus circulation pump 8a, passes through the spray header 9 in the desulfurization apparatus 4a from the absorption liquid circulation pipe 19, is supplied to the absorption liquid spray section 5, and is sprayed from the spray nozzle 6a. The sulfur oxide removed from the exhaust gas in the desulfurization apparatus 4a reacts with limestone in the absorption liquid to become calcium sulfite as an intermediate product, and the oxidized air 21 is transferred to the desulfurization apparatus 4a by an oxidation air blower (not shown). Oxidized air 21 supplied and supplied to the desulfurizer tank unit 7 is oxidized into gypsum to become a final product (gypsum).

  In this way, by directly supplying the oxidized air 21 into the desulfurization apparatus, the entire reaction is promoted by simultaneously proceeding the absorption reaction of the sulfur oxide in the exhaust gas and the oxidation reaction of the generated calcium sulfite, and the desulfurization performance is improved. improves. At that time, the oxidized air 21 supplied to the desulfurizer 4a is refined by the oxidizing stirrer 22 to increase the utilization rate of the oxidized air. Thereafter, the absorbent slurry is extracted by the extraction pump 12a in accordance with the amount of the generated gypsum, sent to the gypsum dewatering equipment 13a, and recovered as powder gypsum 14a.

  FIG. 6 shows the structure and system of the outside oxidation system of the desulfurization apparatus 4a. The difference between the structure and system of the outside oxidation system and that of the inside oxidation system is that a dust removing tower 31 for cooling and removing the exhaust gas 1 is installed at the inlet of the desulfurization apparatus 4b. In the desulfurization apparatus 4b, direct oxidation air is used. An oxidation tower 27 is installed to oxidize calcium sulfite in the limestone slurry extracted from the desulfurization apparatus 4b to form gypsum, in which an absorption liquid mainly composed of calcium sulfite is brought into gas-liquid contact with the exhaust gas. It is a point.

  6 is a reaction in which the absorption liquid discharged from the circulation tank unit 7 is guided to the pH adjustment tank 33 and sulfuric acid is supplied to the pH adjustment tank 33 to oxidize calcium sulfite to form gypsum. . Such an external oxidation system is rarely used at present because of increased equipment costs and utility costs.

The exhaust gas of the boiler that burns fossil fuel contains a trace amount of mercury components derived from raw materials. Mercury components in exhaust gas exist in the form of metallic mercury (HgO) and divalent mercury (Hg ²⁺ ), and metallic mercury is released into the atmosphere without being collected, but divalent mercury is water-soluble. Because it is expensive, it is absorbed and removed by wet flue gas desulfurization equipment installed in the boiler downstream. It is known that divalent mercury absorbed and removed by wet flue gas desulfurization equipment is reduced to metallic mercury and re-released into exhaust gas under certain conditions (for example, oxidation process of calcium sulfite). .

  In recent years, the heavy metal emission regulations have been strengthened mainly in the United States, and mercury has also been designated as a regulated substance. In order to suppress the discharge of mercury from the wet flue gas desulfurization apparatus, it is necessary to prevent the re-release of mercury into the exhaust gas. So far, methods for removing mercury from the exhaust gas have been studied.

As a conventional technique, there has been proposed a method for removing mercury components in exhaust gas by adjusting the amount of oxidized air or adding an oxidant into the desulfurization apparatus and controlling the oxidation-reduction potential of the absorption liquid (see Patent Document 1). ).

  Further, a method has been proposed in which a cooling device for spraying a coolant is installed on the upstream side of the desulfurization device, and bivalent mercury is absorbed and removed in the form of mercury chloride (see Patent Document 2).

  Similarly, there has been proposed a method in which a dust removing tower is installed on the upstream side of the desulfurization apparatus, and a slurry made of calcium sulfite in the dust removal tower tank is introduced into the tank of the desulfurization apparatus and is oxidized and recovered as gypsum slurry (Patent Document 3). reference).

  Further, Patent Document 4 discloses a method for removing mercury by adding a mercury removing agent such as sodium hypochlorite and hydrogen peroxide into the cooling water supplied to the cooling tower on the upstream side of the desulfurization apparatus.

  Further, Patent Document 5 discloses that calcium hydroxide is added as a metal fixing agent to waste water that has absorbed mercury in exhaust gas.

JP 2004-313833 A JP 2007-7580 A Japanese Patent Laid-Open No. 62-225226 Japanese Patent Laid-Open No. 10-216476 JP 2003-1267 A

The technique described in Patent Document 1 has a problem that consumption of oxidant and utility cost increase due to consumption of oxidant by reducing gas such as sulfur dioxide (SO ₂ ) in exhaust gas. Further, in the technique described in Patent Document 2, it is considered that the pH of the coolant is extremely low because hydrogen fluoride and hydrogen chloride in the exhaust gas are absorbed into the coolant together with the divalent mercury, which is very expensive. It is not an economically effective means because it is necessary to install a material cooling device.

  Furthermore, in the technique described in Patent Document 3, mercury collected in the dust removal tower tank is reduced in the tank of the desulfurization apparatus and released again into the exhaust gas as metallic mercury, so that consideration is given to suppressing mercury re-release. Absent.

  The technology described in Patent Document 4 describes that mercury removing agents such as sodium hypochlorite and hydrogen peroxide are supplied to the cooling tower on the upstream side of the desulfurization apparatus, but a large amount of mercury removing agent is used. There is a need to.

  Furthermore, the technique described in Patent Document 5 is also a method aimed only at mercury removal, and the viewpoint of exhaust gas desulfurization is missing.

  The object of the present invention is to eliminate the disadvantages of the prior art and to suppress low-cost and efficient mercury re-release that prevents divalent mercury in the absorption liquid from being reduced to metallic mercury and re-released into the exhaust gas. It is to provide a mercury re-release suppression device and method.

In order to achieve the above object, the invention described in claim 1 is characterized in that mercury from a wet flue gas desulfurization apparatus that absorbs and removes sulfur oxides contained in exhaust gas using an absorbing liquid comprising a slurry containing limestone. In the re-emission control method, sulfurous acid generated in the mercury removal device by supplying an absorption liquid made of slurry containing limestone into the mercury removal device to which exhaust gas installed upstream of the wet flue gas desulfurization device is introduced. the absorbing solution containing calcium contacting exhaust gas and the gas-liquid, a mercury re-emission method for suppressing Ru by fixing mercury into the calcium sulfite. In addition, an antioxidant (inhibitor) can be added to the mercury removal device as necessary.

  According to a second aspect of the present invention, a metal fixing agent is supplied to the mercury removing device, and an oxidizing agent containing air or hydrogen peroxide solution is supplied to the absorbing solution containing calcium sulfite extracted from the mercury removing device. This is a method for suppressing mercury re-release.

  The invention as set forth in claim 3 is characterized in that the supply amount of the absorbing liquid composed of slurry containing limestone to the mercury removing device and the inside of the mercury removing device so that the concentration of metallic mercury in the gas at the outlet of the desulfurization device falls within the range of the regulation value. The mercury re-release suppression method according to claim 1, wherein the amount of circulating liquid of the absorption liquid is adjusted to be minimized.

According to a fourth aspect of the present invention, there is provided an apparatus for suppressing mercury re-emission from a wet flue gas desulfurization apparatus that absorbs and removes sulfur oxides contained in exhaust gas by using an absorption liquid comprising a slurry containing limestone. A mercury removing device in which exhaust gas is introduced to the upstream side of the smoke desulfurization device is installed, and the mercury removing device is provided with an absorption liquid supply system composed of a slurry containing limestone, and a circulation system of the absorbing liquid. It is the mercury re-release suppression apparatus which comprised mercury by adhering to the said calcium sulfite by the gas-liquid contact of the absorption liquid containing calcium sulfite produced | generated in the inside, and waste gas .

  According to the fifth aspect of the present invention, the mercury removal apparatus is provided with a metal fixing agent supply system, an oxidation tower for storing an absorption liquid containing calcium sulfite from the mercury removal apparatus is provided, and air or hydrogen peroxide water is provided in the oxidation tower. The mercury re-emission suppression device according to claim 4, further comprising an oxidant supply system including

According to the sixth aspect of the present invention, an apparatus for measuring the concentration of metallic mercury in the outlet exhaust gas is provided in the outlet exhaust gas flow path of the desulfurization apparatus so that the measured value of the metallic mercury concentration of the metallic mercury concentration measuring apparatus falls within the regulation value range. A control device for adjusting the absorption liquid supply amount in an absorption liquid supply system comprising slurry containing limestone to the mercury removal apparatus and the circulation liquid amount of the absorption liquid in the circulation system of the absorption liquid of the mercury removal apparatus. The mercury re-emission suppression device according to claim 4, wherein

(Function)
In the present invention, by supplying limestone into a mercury removal device installed on the upstream side of the desulfurization device, and making the gas-liquid contact between the absorption liquid mainly composed of calcium sulfite and the exhaust gas in the mercury removal device, Efficiently absorbs divalent mercury in the exhaust gas and prevents the introduction of divalent mercury into the desulfurization unit, thereby suppressing the reduction of divalent mercury to metallic mercury and the release of metallic mercury into the exhaust gas in the desulfurization unit Is possible.

  Moreover, compared with the technique (patent document 2) which distributes the cooling water of a prior art by supplying limestone to the mercury removal apparatus, since the pH in the mercury removal apparatus can be maintained high, corrosion of the mercury removal apparatus is suppressed. It is possible to install a mercury removal device with an inexpensive material. Furthermore, by adding an antioxidant (inhibitor) to the mercury removal unit as necessary, natural oxidation of calcium sulfite due to oxygen in the exhaust gas can be prevented, and the re-release of mercury associated with sulfite oxidation can be suppressed. Is possible.

In addition, a metal fixing agent is supplied into the mercury removing device, a part of the absorption liquid mainly composed of calcium sulfite is continuously extracted from the mercury removing device and supplied to the oxidation tower by a pump, and air or hydrogen peroxide solution (H By supplying an oxidizing agent such as ₂ O ₂ ) to the oxidation tower, it is possible to oxidize calcium sulfite to gypsum while suppressing the re-release of divalent mercury, and to fix divalent mercury efficiently in gypsum. is there. A chelate compound or the like is used as the metal fixing agent. The produced gypsum is dehydrated by a dehydrator and recovered as solid gypsum, whereby divalent mercury can be discharged out of the system.

  In addition, a mercury concentration measuring device is installed at the outlet of the desulfurization unit, and the amount of limestone supplied to the mercury removal unit and the absorption liquid circulation in the mercury removal unit so that the metal mercury concentration in the gas at the desulfurization unit outlet falls within the range of the regulation value. By adjusting the liquid amount to be a minimum, it is possible to reduce the cost of the outside oxidation equipment, and it is also possible to reduce the amount of gypsum containing divalent mercury.

  According to the present invention, it is possible to suppress mercury re-emission at low cost and high efficiency. That is, according to the first and fourth aspects of the present invention, limestone is supplied into a mercury removal device installed on the upstream side of the desulfurization device, and the absorption liquid and exhaust gas mainly composed of calcium sulfite are gasified in the mercury removal device. By making the liquid contact, the mercury removal device efficiently absorbs the divalent mercury in the exhaust gas and prevents the introduction of the divalent mercury into the desulfurization device, thereby reducing the divalent mercury to metallic mercury in the desulfurization device and It is possible to suppress the release of metallic mercury into the exhaust gas.

  Also, by supplying limestone to the mercury removing device, the pH in the mercury removing device can be maintained high, so that corrosion of the mercury removing device can be suppressed, and it is possible to install the mercury removing device with an inexpensive material. is there.

According to the second and fifth aspects of the invention, in addition to the effects of the first and fourth aspects, the metal fixing agent is supplied into the mercury removing device, and the absorption liquid containing calcium sulfite in the mercury removing device is provided. A part is extracted into an oxidation tower, and an oxidizing agent such as air or hydrogen peroxide (H ₂ O ₂ ) is supplied to oxidize calcium sulfite to gypsum while suppressing rerelease of divalent mercury. It is possible to efficiently fix valence mercury in gypsum.

  According to the third and sixth aspects of the invention, in addition to the effects of the first and fourth aspects, the supply amount of limestone to the mercury removing device and the mercury removing device according to the mercury concentration in the exhaust gas at the outlet of the desulfurizer It is possible to reduce the cost of external oxidation equipment and to reduce the amount of gypsum containing divalent mercury by adjusting the amount of the circulating fluid in the inside to be minimized. It is.

It is a figure which shows the structure and system | strain of the absorption tower of the wet desulfurization apparatus of one Example of this invention. It is a figure which shows the other structure and system | strain example of the wet desulfurization apparatus of one Example of this invention. It is a figure which shows the other structure and system | strain example of the wet desulfurization apparatus of one Example of this invention. It is a figure which shows the experimental data regarding this invention. It is a figure which shows the structure and system | strain of the oxidation system in a tower | column of the conventional wet desulfurization apparatus. It is a figure which shows the structure and system | strain of the outside oxidation system of the conventional wet desulfurization apparatus.

  The present invention will be described in detail with reference to the drawings. The present invention is not limited to the following examples. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  A schematic structure of a wet flue gas desulfurization apparatus according to the present embodiment is shown in FIG. In FIG. 1, exhaust gas 1 from a boiler or the like containing sulfur metal, hydrogen chloride and hydrogen fluoride together with metal mercury and divalent mercury is introduced into a mercury removal device 25 installed on the upstream side of the desulfurization device 4a. Thereafter, it passes through the desulfurization apparatus 4a and is discharged as clean exhaust gas 2.

Although FIG. 1 shows an example in which the exhaust gas 1 is introduced from the side wall of the mercury removing device 25, the introduction location and introduction method of the exhaust gas 1 are not limited to the location and method shown in FIG. The mercury removing device 25 is supplied with an absorbing liquid made of limestone slurry in the limestone slurry tank 16 by a limestone slurry pump 17 provided in the absorbing solution supply pipe 20 and reacts with sulfur oxides absorbed in the mercury removing device 25. It becomes calcium sulfite. The absorption liquid containing calcium sulfite is pressurized by a circulation pump 8b provided in an absorption liquid circulation pipe 23 connected to the mercury removal apparatus 25 and sprayed again into the mercury removal apparatus 25 from the spray nozzle 6b to come into gas-liquid contact with the exhaust gas 1. . Moreover, you may add the antioxidant (inhibitor) 26 in the mercury removal apparatus 25 as needed. Further, a metal fixing agent 36 such as a chelate compound is supplied to the mercury removing device 25.
The circulating flow rate of the absorbing liquid can be adjusted or stopped by the adjusting valve 18c provided in the absorbing liquid circulation pipe 23.

  In the mercury removing apparatus 25, a part of the absorption liquid containing a large amount of calcium sulfite, which is the reaction product, is continuously extracted by the extraction pump 12b and supplied to the oxidation tower 27. In the oxidation tower 27, calcium sulfite is oxidized to gypsum by supplying an oxidant 28 such as air or hydrogen peroxide water, and then the gypsum slurry in the oxidation tower 27 is extracted and supplied to the dehydrator 13 b by the pump 12 c. The gypsum slurry is dehydrated by the machine 13b and recovered as solid gypsum 14b. The filtrate discharged from the dehydrator 13b is returned to the mercury removing device 25 again by the extraction pump 12d.

  In FIG. 1, exhaust gas 1 from a boiler or the like containing metal mercury and divalent mercury together with sulfur oxide, hydrogen chloride and hydrogen fluoride is introduced into a mercury removal device 25 installed on the upstream side of the desulfurization device 4 to remove mercury. By spraying an absorption liquid mainly composed of calcium sulfite from the spray nozzle 6b in the device 25, divalent mercury having high water solubility is absorbed into the absorption liquid together with sulfur oxide, hydrogen chloride and hydrogen fluoride in the exhaust gas 1. .

  FIG. 4 shows the test results comparing the amount of mercury fixed in calcium sulfite and gypsum. In the test, calcium sulfite or gypsum was added to an aqueous solution containing a predetermined concentration of mercury, and the amount of mercury fixed in calcium sulfite or gypsum after bubbling air to the prepared aqueous solution for a certain time was measured. As a result of comparing the amount of mercury fixed in calcium sulfite and gypsum as shown in FIG. 4, the amount of mercury fixed in calcium sulfite was about 40 times larger than the amount of mercury fixed in gypsum. From this test result, it was confirmed that the divalent mercury was fixed to calcium sulfite, thereby reducing the reduction to metallic mercury and the re-release of mercury into the exhaust gas. Since the divalent mercury is fixed to the calcium sulfite in the mercury removing device 25, it is possible to suppress the re-release of mercury. In this embodiment, limestone slurry is supplied from the limestone slurry tank 16 into the mercury removing device 25. For this reason, compared with the technique (patent document 2) which sprays the cooling water of a prior art, since pH in the mercury removal apparatus 25 can be maintained high, corrosion of the mercury removal apparatus 25 can be suppressed, and it is an inexpensive material It is possible to install a mercury removal device 25. Further, if necessary, an antioxidant (inhibitor) 26 may be added to the mercury removing device 25 to prevent re-release of mercury due to natural oxidation by oxygen in the exhaust gas of calcium sulfite in the absorption liquid. A metal fixing agent 36 such as a chelate compound is supplied to the mercury removing device 25, and a part of the absorption liquid mainly composed of calcium sulfite containing divalent mercury in the mercury removing device 25 is continuously extracted by the pump 12b. To the oxidation tower 27.

By adding an oxidizing agent 28 such as air or hydrogen peroxide water (H ₂ O ₂ ) to the oxidation tower 27, calcium sulfite is oxidized to gypsum while suppressing re-release of mercury caused by the oxidation reaction of calcium sulfite. It is possible to make it. The gypsum slurry generated in the oxidation tower 27 is supplied to the dehydrator 13b by the extraction pump 12c, dehydrated by the dehydrator 13b, and recovered as solid gypsum 14b containing divalent mercury. The filtrate discharged from the dehydrator 13b is returned to the mercury removing device 25 again by the extraction pump 12d.

  The exhaust gas treated by the mercury removing device 25 is introduced into the desulfurization device 4a through the duct 34, and the limestone 15 as the sulfur oxide absorbent is converted into a limestone slurry in the limestone slurry tank 16, and the limestone slurry is obtained. The pump 17 supplies the desulfurization apparatus 4a through the absorbent supply pipe 20 with the flow rate adjusting valve 18a according to the amount of sulfur oxide absorbed. Limestone slurry staying in the lower part of the desulfurization apparatus 4a is sprayed from the spray nozzle 6a of the spray header 9 provided in the empty column part in the desulfurization apparatus 4a via the absorption liquid circulation pipe 19 by the limestone slurry pump 8a. A desulfurization reaction is performed.

  Further, the absorption liquids of the mercury removal device 25 and the desulfurization device 4a are stirred by the stirrer 24 and the stirrer 22 for oxidation, respectively. Absorbing liquid oxidation air 21 is supplied from around the rotating shaft of the oxidation stirrer 22 that stirs the absorption liquid of the desulfurization apparatus 4a, and the air 21 is refined in the absorption liquid by a fan to promote the oxidation reaction.

  Comparing the invention of this embodiment with the prior art, first, in the desulfurization apparatus 4b of the outside oxidation system shown in FIG. 6, mercury is used to bring the absorption liquid mainly composed of calcium sulfite into contact with the exhaust gas 1 as in the invention of this embodiment. However, when the by-product is recovered as gypsum, the amount of calcium sulfite to be oxidized is large in the outside oxidation system shown in FIG. There are problems such as an increase in equipment costs and a large amount of gypsum containing mercury. However, in the system of the present embodiment, as shown in FIGS. 1 and 2, by combining the mercury removal device 25 and the desulfurization device 4a of the in-column oxidation method, compared with the desulfurization device 4b of the outside oxidation method shown in FIG. Since the amount of slurry supplied to the outside oxidation facility is small, the outside oxidation facility can be reduced in scale, and the equipment cost can be reduced.

  Further, the present embodiment has an advantage that the amount of gypsum containing mercury as a by-product is smaller than that of the prior art shown in FIG. Further, in the method of this embodiment, the amount of slurry containing mercury is small as compared with the case where the re-release of mercury is suppressed by adding the metal fixing agent 36 to the tank portion 7 of the conventional desulfurization apparatus 4a of FIG. There is an advantage that the amount of the metal fixing agent 36 added is small and the amount of the gypsum 14b containing the metal fixing agent 36 as a by-product is small.

  According to this embodiment, the equipment and utility costs can be reduced as compared with the prior art, and the re-release of mercury in the desulfurization apparatus can be efficiently suppressed.

  A schematic structure of the wet flue gas desulfurization apparatus according to the present embodiment is shown in FIG. In addition, the member and apparatus which have the same function demonstrated in FIG. 1 of Example 1 attach | subject the same code | symbol, and abbreviate | omit the description.

  In FIG. 2, a mercury concentration measurement device 30 is provided at the outlet of the desulfurization device 4a, and a control system is constructed in which the opening degree of the control valves 18b and 18c is automatically adjusted according to the concentration detected by the mercury concentration measurement device 30. The supply amount of the limestone slurry to the mercury removing device 25 and the amount of the circulating fluid in the mercury removing device 25 are minimized so that the metal mercury concentration in the exhaust gas 2 at the outlet of the device 4a falls within the range of the regulation value. Further, the control device 30 controls the opening degree of the control valve 18b and the control valve 18c.

  By controlling the opening degree of the control valve 18b and the control valve 18c, the amount of calcium sulfite generated in the mercury removing device 25 is minimized, so the amount of gypsum 14b containing divalent mercury is minimized. Furthermore, the amount of the metal fixing agent 36 added to the oxidation tower 27 and the addition of the oxidizing agent 28 such as air or hydrogen peroxide necessary for the oxidation of calcium sulfite can be minimized. is there. According to this embodiment, it is possible to efficiently suppress mercury re-release with reduced utility costs.

  A schematic structure of the wet flue gas desulfurization apparatus according to the present embodiment is shown in FIG. In addition, the member and apparatus which have the same function demonstrated in FIG. 1 of Example 1 attach | subject the same code | symbol, and abbreviate | omit the description.

A Venturi scrubber 37 shown in FIG. 3 is installed as a mercury removing device, the absorbing liquid in the Venturi scrubber 37 is supplied to the venturi scrubber tank section 38, the absorbing liquid is pressurized by the circulation pump 8b, and the venturi scrubber 37 is again supplied from the circulation pipe 23. To circulate.

  If the venturi scrubber 37 is installed as a mercury removing device, the size of the duct 34 between the venturi scrubber 37 and the desulfurization device 4a can be reduced, which is economical.

  INDUSTRIAL APPLICABILITY The present invention is effective as a measure for suppressing mercury re-release from a desulfurization apparatus that efficiently processes combustion exhaust gas containing a mercury component at low cost.

DESCRIPTION OF SYMBOLS 1 Exhaust gas 2 Clean exhaust gas 3 Inlet duct 4a, 4b Desulfurization apparatus 5 Absorbing liquid spray part 6a, 6b Spray nozzle 7 Desulfurization apparatus tank part 8a, 8b Circulation pump 9 Spray header 10 Mist eliminator 11 Outlet duct
12a, 12b, 12c, 12d Extraction pump 13a Gypsum dewatering equipment 13b Dehydrator 14a, 14b Gypsum 15 Limestone 16 Limestone slurry tank 17 Limestone slurry pumps 18a, 18b, 18c Flow control valve 19 Absorbing liquid circulation piping 20 Absorbing liquid supply piping 21 Oxidation Air 22 Oxidizing stirrer 23 Absorbing liquid circulation pipe 24 Stirrer 25 Mercury removing device 26 Antioxidant 27 Oxidizing tower 28 Oxidizing agent 30 Mercury concentration measuring device 31 Dust removing tower 34 Duct 36 Metal fixing agent 37 Venturi scrubber 38 Venturi scrubber tank section

Claims (6)

In the method for suppressing mercury re-emission from a wet flue gas desulfurization device that absorbs and removes sulfur oxides contained in exhaust gas by using an absorption liquid composed of a slurry containing limestone,
Supplying an absorption liquid made of slurry containing limestone into a mercury removal apparatus to which exhaust gas installed upstream of the wet flue gas desulfurization apparatus is introduced, and an absorption liquid containing calcium sulfite generated in the mercury removal apparatus contacting exhaust gas and the gas-liquid, mercury re-emission suppressing wherein the Rukoto by fixing mercury into the calcium sulfite.   2. The mercury re-emission according to claim 1, wherein a metal fixing agent is supplied to the mercury removing device, and an oxidizing agent containing air or hydrogen peroxide solution is supplied to the absorbing solution containing calcium sulfite extracted from the mercury removing device. Suppression method.   The supply amount of the absorption liquid composed of slurry containing limestone to the mercury removal apparatus and the circulation amount of the absorption liquid in the mercury removal apparatus so that the concentration of metallic mercury in the gas at the outlet of the desulfurization apparatus is within the range of the regulation value. 2. The method for suppressing mercury re-emission according to claim 1, wherein the method is adjusted to be minimized. In the mercury re-emission suppression device from the wet flue gas desulfurization device that absorbs and removes the sulfur oxides contained in the exhaust gas using the absorbent composed of slurry containing limestone,
The mercury removal device in which an exhaust gas is introduced into the upstream side of the wet flue gas desulfurization apparatus is installed, the supply system of the absorbent consisting slurry containing limestone in the aqueous silver removing device, the circulation system of the absorption liquid is provided, mercury A mercury re-release suppression apparatus characterized in that mercury is fixed to the calcium sulfite by gas-liquid contact between an absorption liquid containing calcium sulfite generated in the removal apparatus and exhaust gas .   A mercury fixing device is provided with a metal fixing agent supply system, an oxidation tower for storing an absorption liquid containing calcium sulfite from the mercury removal device is provided, and an oxidizing agent supply system containing air or hydrogen peroxide water is provided in the oxidation tower. The mercury re-emission suppression device according to claim 4.   A mercury mercury concentration measuring device in the outlet exhaust gas is installed in the outlet exhaust gas passage of the desulfurization device, and the mercury removal device contains a slurry containing limestone so that the measured value of the metallic mercury concentration of the metallic mercury concentration measuring device is within the range of the regulation value. And a control device for adjusting the absorption liquid supply amount in the absorption liquid supply system and the circulation amount of the absorption liquid in the absorption liquid circulation system of the mercury removing device. The mercury re-emission suppression device according to claim 4.

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