JPH10216476A - Waste gas treatment and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove metal mercury vapor at a high removal rate from waste gases contg. the metal mercury vapor at an ultra-low concn. of <=10μg/Nm<2> . SOLUTION: This method consists in introducing the waste gases contg. the metal mercury vapor and sulfur dioxide into the cooling tower 60 of a two-tower type desulfurizing equipment 11 where the waste gases are subjected to dust removing and cooling by bringing the gases into contact with cooling water, then introducing the gases into the absorption tower 12 of the two-tower type desulfurizing equipment 11 where the gases are desulfurized by bringing the gases into contact with the circulating liquid of the absorbing liquid and introducing the desulfurized waste gases into a wet electrical dust precipitator 20 where the gases are subjected to a dust removal treatment by bringing the gases into contact with water. In such a case, mercury removing agents are added to at least any among the circulating water of the cooling tower 60, the cooling water of the cooling tower 60, the circulating liquid of the absorption tower 12, the liquid absorbent of the absorption tower 12, the supply water of the wet electrical dust precipitator 20, the circulating water of the wet electrical dust precipitator 20, the water in the main unit of the wet electrical dust precipitator 20 and the waste gases in the inlet of the wet electrical dust precipitator 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating an exhaust gas containing mercury containing metallic mercury vapor as a main component.
In particular, the present invention relates to a method and an apparatus for treating an exhaust gas from a discharge source having an extremely large amount of an exhaust gas having an ultra-low concentration of an order of 10 μg / Nm ³ or less.

[0002]

2. Description of the Related Art Conventionally, as a method for removing mercury contained in exhaust gas from a refuse treatment plant, a wet-type smoke-cleaning treatment apparatus, a method of blowing activated carbon powder into the exhaust gas, and collecting the mercury with a bag filter have already been put into practical use. I have. However, about 90% of the mercury in the exhaust gas from the refuse treatment plant is in the form of mercury chloride, and is easily absorbed by water, so that it can be removed by wet smoke washing. In contrast, metallic mercury vapor is hardly absorbed by water, and therefore cannot be easily removed by the wet smoke washing technology used in the flue gas treatment of a landfill.

[0003] Japanese Patent Application Laid-Open No. 7-204432 discloses an exhaust gas treatment method for spraying slaked lime into exhaust gas from a municipal solid waste incineration plant, filtering the collected dust with a dust filter, and removing harmful substances using a bag filter. Spraying activated carbon with slaked lime in the exhaust gas on the upstream side,
An exhaust gas treatment method is described in which acid gas is neutralized by slaked lime and mercury and dioxin are adsorbed by activated carbon and collected and removed by a bag filter.

Japanese Patent Application Laid-Open No. Hei 7-308542 discloses lead concentrate or artificially synthesized lead sulfide (PbS).
Gaseous or mist-like mercury accompanies a packed bed of absorbent made of a mixture of iron sulfide such as pyrite (FeS ₂ ) produced naturally or a mixture with synthesized iron sulfide supported on a porous material carrier. A method for removing mercury in exhaust gas, which adsorbs and removes mercury by passing the exhaust gas, is described.

[0005]

In the conventional method of blowing activated carbon, mercury is removed by the activated carbon powder layer pre-coated on the bag filter. However, when dust is collected by an electric dust collector, the activated carbon is blown into the pre-coated layer. Is not formed, and no mercury removing effect can be obtained. Furthermore, the mercury concentration in the exhaust gas from the landfill is 100 to 500.
μg / Nm ^3, which is different from that of an exhaust gas having an ultra-low concentration of 10 μg / Nm ³ or less as in the present invention. Incidentally, the above-mentioned Japanese Patent Application Laid-Open No. 7-30854
The method of removing mercury from exhaust gas described in Japanese Patent Publication No. 2 also targets exhaust gas having a high mercury concentration of 1.0 mg / Nm ³ (see Examples in the publication).

The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for mercury contained in an exhaust gas having a very low concentration of 10 μg / Nm ³ or less, which is discharged from a discharge source. In particular, it is an object of the present invention to provide an exhaust gas treatment method and apparatus for removing metallic mercury vapor.

[0007]

In order to achieve the above object, an exhaust gas treatment method according to the present invention comprises introducing an exhaust gas containing metallic mercury vapor and sulfurous acid gas into an absorption tower of a single-column desulfurization apparatus, wherein After the desulfurization treatment by contacting with the circulating liquid, the desulfurization exhaust gas is introduced into a wet electric precipitator, and is contacted with water to remove the dust.In the exhaust gas treatment method, the circulating liquid in the absorption tower, the absorption liquid in the absorption tower, and the wet electric precipitator are used. The mercury removing agent is added to at least one of feed water, circulating water of the wet electrostatic precipitator, water in the main body of the wet electric precipitator, and exhaust gas at the inlet of the wet electric precipitator (see FIGS. 1 and 2). ). As the absorbing solution, a calcium carbonate slurry, slaked lime slurry, quick lime slurry, magnesium hydroxide solution, caustic soda solution, ammonia solution, calcium carbonate solution, slaked lime solution, quick lime solution and the like are used.

Further, in the exhaust gas treatment method of the present invention, after the exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into an absorption tower of a single-column desulfurization apparatus and brought into contact with a lime slurry circulating liquid to perform desulfurization treatment, An exhaust gas treatment method for introducing dust into a wet electrostatic precipitator and contacting it with water to remove dust is characterized in that the exhaust flue gas from the wet electrostatic precipitator is brought into contact with a fixed, moving or fluidized bed of a mercury remover ( FIG.
reference).

Further, in the exhaust gas treatment method of the present invention, an exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into an absorption tower of a single-column desulfurization apparatus, brought into contact with a circulating liquid of an absorbent, and subjected to desulfurization treatment. Wastewater treatment method for introducing wastewater into a wet-type electrostatic precipitator and contacting it with water to remove dust, the circulating liquid in the absorption tower, the absorption liquid in the absorption tower, the supply water for the wet-type electrostatic precipitator, the circulating water for the wet-type electric precipitator, A mercury-removing agent is added to at least one of the water in the main body and the exhaust gas at the inlet of the wet-type electrostatic precipitator, and the exhaust gas from the wet-type electrostatic precipitator is brought into contact with a fixed, moving or fluidized bed of the mercury-removing agent. (See FIGS. 1 and 2).

Further, in the exhaust gas treatment method of the present invention, an exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into a cooling tower of a two-tower type desulfurization apparatus, and brought into contact with cooling water to remove dust and cool. In an exhaust gas treatment method in which the gas is introduced into an absorption tower of a desulfurization device and is brought into contact with a circulating liquid of an absorption liquid to perform desulfurization treatment, the desulfurization exhaust gas is introduced into a wet electric dust collector and brought into contact with water to perform dust removal treatment. , Cooling water for cooling tower, circulating liquid for absorption tower, absorption liquid for absorption tower, supply water for wet electric precipitator, circulating water for wet electric precipitator, water in the body of wet electric precipitator,
And a mercury removing agent is added to at least one of the exhaust gas at the entrance of the wet-type electrostatic precipitator (FIG. 3,
(See FIG. 2).

Further, in the exhaust gas treatment method of the present invention, an exhaust gas containing a metal mercury vapor and a sulfurous acid gas is introduced into a cooling tower of a two-column desulfurization apparatus, and brought into contact with cooling water to remove dust and cool. After being introduced into the absorption tower of the desulfurization unit and subjected to desulfurization treatment by contact with the circulating liquid of the absorption liquid, the desulfurization exhaust gas is introduced into the wet electric dust collector, and is contacted with water to perform the dust removal treatment. It is characterized by contacting the exhaust gas with a fixed bed, a moving bed or a fluidized bed of a mercury removing agent (see FIG. 3).

Further, in the exhaust gas treatment method of the present invention, the exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into a cooling tower of a two-column desulfurization apparatus, and is brought into contact with cooling water to remove dust and cool. In an exhaust gas treatment method in which the gas is introduced into an absorption tower of a desulfurization device and is brought into contact with a circulating liquid of an absorption liquid to perform desulfurization treatment, the desulfurization exhaust gas is introduced into a wet electric dust collector and brought into contact with water to perform dust removal treatment. , Cooling water for cooling tower, circulating liquid for absorption tower, absorption liquid for absorption tower, supply water for wet electric precipitator,
A mercury-removing agent is added to at least one of the circulating water of the wet-type electrostatic precipitator, the water in the main unit of the wet-type electrostatic precipitator, and the exhaust gas at the entrance of the wet-type electrostatic precipitator. It is characterized by being brought into contact with a fixed bed, a moving bed or a fluidized bed (see FIG. 3).

In these exhaust gas treatment methods, mercury removing agents to be added include sodium hypochlorite, copper chloride, manganese chloride, iron chloride, chelating agents, hydrogen peroxide, activated carbon,
Sulfur, alumina, silica, aluminum silicate, activated carbon or aluminum silicate impregnated with any of sulfur, iodine, iron chloride, chelating agent and amalgam forming metal, iron sulfide, lead sulfide, calcium chloride, and coal ash Alternatively, a combination of a plurality of types is used. In this case, the solid additive is made into a powder, and is added to a circulating liquid or the like as a powder, as a slurry, or as an aqueous solution. In addition, when adding to exhaust gas, the above-mentioned powder, slurry, or aqueous solution is sprayed.

As a mercury removing agent for forming a fixed bed, a moving bed or a fluidized bed, activated carbon, activated coke, alumina, silica, aluminum silicate, activated carbon or aluminum silicate, sulfur / iodine / iron chloride / chelating agent / amalgam forming agent One or a combination of a plurality of types of metal-impregnated, copper-copper-dispersed activated carbon, lead sulfide, and pyrite are used, and metal mercury vapor is dry-removed before a chimney. In the case of a fixed bed, two or more towers may be installed in parallel, and removal and heating / regeneration may be repeated. In addition, it is preferable that the moving bed be configured so that removal and regeneration are performed in parallel. As the chelating agent, a liquid chelating agent such as sodium diethylthiocarbamate (DDTC) or the like is used. In some cases, the liquid chelating agent is used in combination with cupric chloride. Further, a chelate resin or the like having a dithiocarbamate group (= N—CS ₂ H) as a chelate forming group can be used. As the polymer base of the chelating agent, polystyrene is the most common, but phenol, epoxy, vinyl chloride and the like are also used. Representative examples of the chelating group to be introduced include a carboxylic acid type (—COOH), a polyamine type (—CH ₂ CH ₂ NH—), and an aminocarboxylic acid type (—N
(CH ₂ COOH) _2), hydroxamic type (-CONH
OH), oxime _{(-C (NH 2) NOH)} , β- diketone (-COCH ₂ COCH _3), phosphoric acid (-P
O (OH) ₂ ), aminophosphate type (—NH—CH ₂ —P
O (OH) ₂ ), dithiocarbamic acid type (-NH-CS
SH), dithioic acid type (-CSSH), thiol type (-
SH) and thiourea type (—NHC (NH ₂ ) S).
Most of the electron donating atoms use N, S, O, P, and those having practicality are limited in view of easiness of synthesis, durability, adsorption performance and the like.

The exhaust gas treatment apparatus of the present invention includes a single-column desulfurization apparatus having an absorption tower for introducing an exhaust gas containing metallic mercury vapor and sulfurous acid gas and bringing the exhaust gas into contact with a circulating liquid of an absorbent to perform desulfurization treatment. A wet-type electrostatic precipitator that introduces desulfurized exhaust gas from the desulfurization exhaust gas and makes it contact with water to perform dust-removal treatment, and a circulating liquid pipe of the absorption tower, a main body of the absorption tower, a supply water pipe of the wet-type electrostatic precipitator, A mercury removing agent adding means is connected to at least one of a circulating water pipe of the wet electric precipitator, a main body of the wet electric precipitator, and an exhaust gas duct at the inlet of the wet electric precipitator (see FIGS. 1 and 2).

Further, the exhaust gas treatment apparatus of the present invention comprises a single-column desulfurization apparatus having an absorption tower for introducing an exhaust gas containing metallic mercury vapor and sulfurous acid gas and bringing the exhaust gas into contact with a circulating liquid of an absorbent to perform desulfurization treatment. A wet-type electrostatic precipitator that introduces the desulfurized exhaust gas from the tower-type desulfurization device and contacts the water to remove the dust, and in the exhaust gas treatment device, a fixed bed of a mercury remover is provided in an exhaust gas duct downstream of the wet-type electrostatic precipitator; It is characterized by providing a mercury removing agent layer comprising a moving bed or a fluidized bed (see FIG. 1).

Further, the exhaust gas treatment apparatus of the present invention includes a single-column desulfurization apparatus having an absorption tower for introducing an exhaust gas containing metallic mercury vapor and sulfurous acid gas and bringing the exhaust gas into contact with a circulating liquid of an absorbent to perform desulfurization treatment. Supply of the circulating liquid pipe of the absorption tower, the main body of the absorption tower, and the wet-type electrostatic precipitator in the exhaust gas treatment apparatus including a wet-type electrostatic precipitator that introduces the desulfurized exhaust gas from the tower-type desulfurization apparatus and performs dust removal treatment by contact with water. A mercury remover addition means is connected to at least one of a water pipe, a circulating water pipe of the wet-type electrostatic precipitator, a main body of the wet-type electrostatic precipitator, and an exhaust gas duct at the entrance of the wet-type electrostatic precipitator. It is characterized by having a mercury removing agent layer comprising a fixed bed, a moving bed or a fluidized bed of the removing agent (see FIG. 1).

Further, the exhaust gas treatment apparatus of the present invention includes a cooling tower that introduces exhaust gas containing metal mercury vapor and sulfur dioxide gas and removes and cools it by contacting with water, and a lime slurry circulating liquid that introduces the cooled exhaust gas and An exhaust gas treatment device comprising a two-column desulfurization device having an absorption tower for contacting and desulfurizing, and a wet-type electrostatic precipitator for introducing desulfurized exhaust gas from the two-column desulfurization device and contacting with water to remove the dust. , The circulating water pipe of the cooling tower, the main body of the cooling tower, the circulating liquid pipe of the absorption tower, the main body of the absorption tower, the supply water pipe of the wet electric precipitator, the circulating water pipe of the wet electric precipitator, the main body of the wet electric precipitator, and the wet electric precipitator inlet A mercury remover adding means is connected to at least one of the exhaust gas ducts (see FIGS. 3 and 2).

Further, the exhaust gas treatment apparatus of the present invention comprises a cooling tower for introducing exhaust gas containing metallic mercury vapor and sulfur dioxide gas and bringing it into contact with water to remove and cool dust, and a circulating liquid for introducing the cooled exhaust gas and absorbing liquid. Exhaust gas treatment comprising a two-column desulfurization device having an absorption tower for performing desulfurization treatment by contacting with water, and a wet-type electrostatic precipitator for introducing desulfurization exhaust gas from the two-column desulfurization device and contacting with water to remove dust. In the device, a fixed bed of mercury remover is installed in the exhaust gas duct downstream of the wet electrostatic precipitator,
It is characterized in that a mercury removing agent layer composed of a moving bed or a fluidized bed is provided (see FIG. 3).

The exhaust gas treatment apparatus of the present invention further comprises a cooling tower for introducing exhaust gas containing metallic mercury vapor and sulfurous acid gas and bringing it into contact with water to remove and cool dust, and a circulating liquid for introducing the cooled exhaust gas and absorbing liquid. Exhaust gas treatment comprising a two-column desulfurization device having an absorption tower for performing desulfurization treatment by contacting with water, and a wet-type electrostatic precipitator for introducing desulfurization exhaust gas from the two-column desulfurization device and contacting with water to remove dust. In the apparatus, a circulating water pipe of a cooling tower, a main body of a cooling tower, a circulating liquid pipe of an absorption tower, a main body of an absorption tower, a supply water pipe of a wet electric dust collector, a circulating water pipe of a wet electric dust collector, a main body of a wet electric dust collector, and a wet electric dust collector A mercury removing agent addition means is connected to at least one of the exhaust gas ducts at the inlet, and further, a mercury removing agent comprising a fixed bed, a moving bed or a fluidized bed of the mercury removing agent is connected to the exhaust gas duct downstream of the wet electrostatic precipitator. It is characterized in that a layer (see FIG. 3).

[0021]

FIG. 1 shows an exhaust gas treatment apparatus according to a first embodiment of the present invention, which has a single-column desulfurization apparatus. In FIG. 1, the metal mercury vapor concentration is 0.
An ultra-low concentration exhaust gas of 5 to 10 μg / Nm ³ is introduced into a gas heater (not shown) to preheat air to cool the exhaust gas, and after being subjected to dust removal by an electric dust collector (not shown), It is introduced into the absorption tower 12 of the single-column desulfurization apparatus 10.
In the absorption tower 12, the exhaust gas comes into contact with the lime slurry circulating liquid to absorb and remove SOx. Reference numeral 14 denotes an absorption liquid circulation pump, and reference numeral 16 denotes a circulation liquid pipe. The exhaust gas thus desulfurized is introduced into the wet electric precipitator 20 through the mist eliminator 18 and subjected to the wet dedusting treatment.
The gas is introduced into the gas / gas heater 22 and indirectly exchanges heat with the air to preheat the air, and the exhaust gas is cooled and discharged from the chimney 24. 26 is a fan.

FIG. 2 shows details around the wet-type electrostatic precipitator 20. From the makeup water tank 28 to the makeup water pump 30
The new water is sprayed onto the upper part of the dust collector main body 34 through the supply water pipe 32, and the water collected in the lower part in the dust collector main body 34 is stored in the drainage tank 36, flows into the circulating water tank 38, and flows into the circulating water pump 40. Is sprayed onto the upper portion of the dust collector main body 34 via the circulating water pipe 42, and the exhaust gas and water come into contact with each other to be subjected to dust collection processing. Caustic soda or an aqueous solution of caustic soda for neutralization is supplied to the circulating water tank 38, and the drainage tank 3
Blow water is withdrawn from 6 and sent to a desulfurization cooling tower or a wastewater treatment device if a desulfurization cooling tower is provided. 44 is a stirrer and 46 is a strainer.

The above shows the configuration of a conventional exhaust gas treatment apparatus. In the above configuration, the circulating liquid pipe 1 of the absorption tower 12
6, mercury in at least one of the main body 13 of the absorption tower 12, the supply water pipe 32 of the wet electric precipitator 20, the circulating water pipe 42 of the wet electric precipitator 20, the main body 34 of the wet electric precipitator 20, and the exhaust gas duct 48 at the entrance of the wet electric precipitator. The removing agent adding means 50 is connected, and an aqueous solution, slurry, powder or the like of a mercury removing agent (additive) is added or sprayed. 1 and 2
Here, as an example, a case where an aqueous solution or slurry is supplied from an additive tank 52 by an additive pump 54 is shown. The additive is not limited to the discharge side of the circulating liquid pump, but may be supplied to the suction side or the inside of the apparatus body.

The gas downstream of the wet electric dust collector 20
Exhaust gas duct 56 between gas heater 22 and chimney 24
In addition, a mercury removing agent layer 58 composed of a fixed bed, a moving bed or a fluidized bed of the mercury removing agent is provided to dry remove mercury vapor in front of the chimney 24. The mercury remover layer 58 may be combined with the mercury remover adding means 50 described above, or only the mercury remover layer 58 may be provided without providing the mercury remover adding means.

FIG. 3 shows an exhaust gas treatment apparatus according to a second embodiment of the present invention, which has a two-column desulfurization apparatus. In FIG. 3, the metal mercury vapor concentration is 0.5 to 10
μg / Nm ³ ultra-low-concentration exhaust gas is introduced into a gas heater (not shown) to preheat air to cool the exhaust gas. It is introduced into the cooling tower 60 of the type desulfurization device 11. In the cooling tower 60, the exhaust gas comes into contact with the circulating water to remove dust and
Cooled. 62 is a circulating water pump, 64 is a circulating water pipe, 6
Reference numeral 6 denotes a water extraction pump, and the extracted water is sent to a wastewater treatment device. The cooled exhaust gas passes through the mist eliminator 68 and is introduced into the absorption tower 12 of the two-column desulfurization apparatus 11. Other configurations and operations are the same as those in FIGS. 1 and 2.

In these configurations, the circulating water pipe 64 of the cooling tower 60, the main body 61 of the cooling tower 60, the circulating liquid pipe 16 of the absorption tower 12, the main body 13 of the absorption tower 12, the supply water pipe 32 of the wet electric precipitator 20, the wet electric A mercury remover adding means 50 is connected to at least one of the circulating water pipe 42 of the dust collector 20, the main body 34 of the wet electrostatic precipitator 20, and the exhaust gas duct 48 at the entrance of the wet electrostatic precipitator, and an aqueous solution of the mercury remover (additive), slurry Or powder or the like is added or sprayed. The configuration and operation of the mercury removing agent layer 58 and other components are the same as those of the first embodiment. Table 1 shows an example of the approximate values of the atmospheric gas in each facility in the apparatus shown in FIGS.

[0027]

[Table 1]

[0028]

EXAMPLES Examples and comparative examples of the present invention will be described below. Example 1 In this example, a mercury removal effect confirmation test was performed in a cooling tower of a two-tower type desulfurization apparatus. Bypass part of the combustion exhaust gas containing metallic mercury vapor, tower diameter 250mm, height 500
The mercury-removing effect was investigated by introducing water containing sodium hypochlorite as a mercury-removing agent from the lower part of the absorption tower test apparatus of 0 mm and from the 3000 mm height of the upper part of the absorption tower. In order to increase the gas-liquid contact area in the absorption tower, 10
Glass beads of mmφ were filled to a height of 2500 mm. Table 2 shows test conditions and measurement results of gas properties at the inlet and outlet of the absorption tower.

[0029]

[Table 2]

Comparative Example 1 A test was conducted in Example 1 except that no mercury removing agent was supplied. Table 2 shows test conditions and measurement results of gas properties at the inlet and outlet of the absorption tower.

Example 2 In this example, a test was conducted to confirm the effect of removing mercury in an absorption tower of a two-column desulfurizer. Bypass a part of exhaust gas containing metal mercury vapor, tower diameter 250mm, height 5000mm
Introduced from the lower part of the absorption tower test equipment of the above, and a slurry in which sulfur powder was added as a mercury remover to a water slurry containing limestone as a desulfurizing agent was supplied from a height of 3000 mm above the absorption tower, and the mercury removal effect was examined. Was. The absorption tower was filled with glass beads having a diameter of 10 mm up to a height of 2500 mm in order to increase the gas-liquid contact area. Table 3 shows the test conditions and the results of gas property measurement at the inlet and outlet of the absorption tower.

[0032]

[Table 3]

Comparative Example 2 In Example 2, a test was conducted without supplying a mercury removing agent. Table 3 shows the test conditions and the results of gas property measurement at the inlet and outlet of the absorption tower.

Example 3 In this example, a test was conducted to confirm the effect of removing mercury in an absorption tower of a two-column desulfurization apparatus. Bypass a part of exhaust gas containing metal mercury vapor, tower diameter 250mm, height 5000mm
Liquid chelating agent (sodium diethyl thiocarbamate (DDTC)) as a mercury remover from the lower part of the absorption tower test device at a height of 3000 mm above the absorption tower
Water to which was added was supplied to examine the mercury removal effect. In order to increase the gas-liquid contact area in the absorption tower, 10
Glass beads of mmφ were filled to a height of 2500 mm. Table 4 shows the test conditions and the results of gas property measurement at the inlet and outlet of the absorption tower.

[0035]

[Table 4]

Comparative Example 3 In Example 3, a test was conducted without supplying a mercury removing agent. Table 4 shows the test conditions and the results of gas property measurement at the inlet and outlet of the absorption tower.

Examples 4, 5, and 6 In this example, a test for confirming the mercury removal effect in a mercury remover-filled layer was performed. Part of the gas after desulfurization treatment of the exhaust gas containing metal mercury vapor was bypassed and introduced into the mercury remover pellet packed layer to examine the mercury removal effect. As a mercury removing agent, copper was selected as an example of a metal that forms amalgam with mercury, and activated carbon honeycomb (Example 4) in which copper was dispersed and supported, alumina honeycomb with sulfur added (Example 5), chelating agent (diethylthio) A zeolite honeycomb impregnated with sodium carbamate (DDTC) (Example 6) was used. Table 5 shows the test conditions and the results of gas property measurement at the inlet and outlet of the packed bed.

[0038]

[Table 5]

[0039]

As described above, the present invention has the following effects. (1) Conventionally, as a method of removing mercury (mainly mercury chloride) contained in exhaust gas from a refuse incineration plant, a wet smoke cleaning technology, an activated carbon blowing / bag filter dust collection technology, and the like have been put into practical use. The technology can remove mercury chloride but not metallic mercury. According to the method and apparatus of the present invention, metallic mercury vapor can be efficiently removed from exhaust gas. (2) Metallic mercury vapor can be removed at a high removal rate from an ultra-low concentration exhaust gas having a metallic mercury vapor concentration of 10 μg / Nm ³ or less.

[Brief description of the drawings]

FIG. 1 is a flow sheet of an exhaust gas treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a flow sheet showing details around a wet electric precipitator in FIGS. 1 and 3;

FIG. 3 is a flow sheet of an exhaust gas treatment apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1 tower type desulfurization apparatus 11 2 tower type desulfurization apparatus 12 Absorption tower 13 Absorption tower main body 14 Absorption liquid circulation pump 16 Circulating liquid pipe 18, 68 Mist eliminator 20 Wet electric dust collector 22 Gas / gas heater 24 Chimney 26 Fan 28 Makeup water tank 30 Supply water pump 32 Supply water pipe 34 Dust collector body 36 Drain tank 38 Circulating water tank 40 Circulating water pump 42 Circulating water pipe 44 Stirrer 46 Strainer 48, 56 Exhaust gas duct 50 Mercury remover adding means 52 Additive tank 54 Additive pump 58 Mercury removal Agent layer 60 Cooling tower 61 Cooling tower body 62 Circulating water pump 64 Circulating water pipe 66 Water extraction pump

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Motoko Inai 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries Inside Akashi Plant (72) Inventor Shigeharu Ito 3-1-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe-shi Kawasaki Heavy Industries, Ltd. Kobe Plant (72) Inventor Kazuto Marui 3-1-1, Higashi Kawasaki-cho, Chuo-ku, Kobe City Kawasaki Heavy Industries, Ltd. Kobe Plant

Claims (14)

[Claims] 1. An exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into an absorption tower of a single-column desulfurizer, and is brought into contact with a circulating liquid of an absorbent to perform desulfurization treatment. Then, the desulfurized exhaust gas is introduced into a wet-type electrostatic precipitator. In the exhaust gas treatment method of dedusting by contacting with water, the circulating liquid of the absorption tower, the absorption liquid of the absorption tower, the supply water of the wet electric precipitator, the circulating water of the wet electric precipitator, the water in the main body of the wet electric precipitator, and the wet type An exhaust gas treatment method comprising adding a mercury removing agent to at least one of exhaust gas at the entrance of an electrostatic precipitator. 2. An exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into an absorption tower of a single-column desulfurizer, and is brought into contact with a circulating liquid of an absorbent to perform desulfurization treatment. Then, the desulfurized exhaust gas is introduced into a wet-type electrostatic precipitator. An exhaust gas treatment method for dedusting by contacting the exhaust gas with a fixed bed, a moving bed or a fluidized bed of a mercury remover, wherein the exhaust gas from a wet type electrostatic precipitator is brought into contact. 3. The exhaust gas treatment method according to claim 1, further comprising contacting the exhaust gas discharged from the wet type electrostatic precipitator with a fixed bed, a moving bed, or a fluidized bed of a mercury remover. 4. An exhaust gas containing metallic mercury vapor and sulfurous acid gas is introduced into a cooling tower of a two-column desulfurization unit, brought into contact with cooling water to remove dust and cool, and then introduced into an absorption tower of a two-column desulfurization unit. After the desulfurization treatment by contacting with the circulating liquid of the absorbing liquid, the desulfurization flue gas is introduced into the wet-type electrostatic precipitator and brought into contact with water to remove the dust. The mercury remover is added to at least one of the tower circulating liquid, the absorption liquid of the absorption tower, the supply water of the wet electric precipitator, the circulating water of the wet electric precipitator, the water in the body of the wet electric precipitator, and the exhaust gas at the entrance of the wet electric precipitator. An exhaust gas treatment method characterized by being added. 5. An exhaust gas containing a metal mercury vapor and a sulfurous acid gas is introduced into a cooling tower of a two-column desulfurization apparatus, brought into contact with cooling water to remove dust and cool, and then introduced into an absorption tower of a two-column desulfurization apparatus. After the desulfurization treatment by contacting with the circulating liquid of the absorbing liquid, the desulfurization flue gas is introduced into the wet-type electrostatic precipitator, and is contacted with water to remove the dust. An exhaust gas treatment method comprising contacting with a fixed bed, a moving bed or a fluidized bed. 6. The exhaust gas treatment method according to claim 4, further comprising contacting the exhaust gas discharged from the wet electrostatic precipitator with a fixed bed, a moving bed, or a fluidized bed of a mercury remover. 7. As a mercury removing agent to be added, sodium hypochlorite, copper chloride, manganese chloride, iron chloride, a chelating agent,
Hydrogen peroxide, activated carbon, sulfur, alumina, silica, aluminum silicate, activated carbon or aluminum silicate
7. Any one of iodine, iron chloride, chelating agent, amalgam-forming metal, iron sulfide, lead sulfide, calcium chloride, coal ash, or a combination thereof. An exhaust gas treatment method according to any of the above items. 8. As a mercury removing agent for forming a fixed bed, a moving bed or a fluidized bed, activated carbon, activated coke, alumina,
Silica, aluminum silicate, activated carbon or aluminum silicate impregnated with any of sulfur, iodine, iron chloride, chelating agent and amalgam-forming metal, one or a combination of metal copper dispersed activated carbon, lead sulfide and pyrite The exhaust gas treatment method according to any one of claims 2, 3, 5, and 6, wherein 9. A single-column desulfurizer having an absorption tower for introducing an exhaust gas containing metallic mercury vapor and sulfurous acid gas and contacting it with a circulating liquid of an absorbing solution to perform desulfurization treatment, and a desulfurized exhaust gas from the single-column desulfurizer. A circulating liquid pipe of an absorption tower, a main body of an absorption tower, a supply water pipe of a wet-type electrostatic precipitator, and a circulating water pipe of a wet-type electric precipitator. An exhaust gas treatment apparatus, wherein a mercury remover adding means is connected to at least one of a main body of the wet electric precipitator and an exhaust gas duct at an inlet of the wet electric precipitator. 10. A single-column desulfurizer having an absorption tower for introducing an exhaust gas containing metallic mercury vapor and sulfur dioxide gas and contacting it with a lime slurry circulating liquid to perform a desulfurization treatment, and desulfurizing exhaust gas from the single-column desulfurizer. A wet-type electrostatic precipitator that removes dust by bringing it into contact with water and removing the mercury from a fixed, moving, or fluidized bed of a mercury-removing agent in an exhaust gas duct downstream of the wet-type electrostatic precipitator. An exhaust gas treatment device comprising an agent layer. 11. The apparatus for removing mercury in exhaust gas according to claim 9, further comprising a mercury removing agent layer comprising a fixed bed, a moving bed, or a fluidized bed of the mercury removing agent in an exhaust gas duct downstream of the wet electrostatic precipitator. Exhaust gas treatment equipment. 12. A cooling tower for introducing and exhausting exhaust gas containing metallic mercury vapor and sulfurous acid gas and bringing it into contact with water to remove and cool, and an absorption device for introducing the cooled exhaust gas and contacting it with a circulating liquid of an absorbing solution to perform desulfurization treatment. A circulating water pipe of a cooling tower in an exhaust gas treatment device comprising: a two-tower desulfurization device having a tower; and a wet-type electrostatic precipitator for introducing desulfurization exhaust gas from the two-tower desulfurization device and bringing it into contact with water to remove dust. , Cooling tower body, absorption tower circulating liquid pipe,
The mercury removing agent addition means is connected to at least one of a main body of the absorption tower, a supply water pipe of the wet electric precipitator, a circulating water pipe of the wet electric precipitator, a main body of the wet electric precipitator, and an exhaust gas duct at an inlet of the wet electric precipitator. Exhaust gas treatment equipment. 13. A cooling tower for introducing and exhausting exhaust gas containing metal mercury vapor and sulfurous acid gas and bringing it into contact with water to remove and cool, and an absorption device for introducing the cooled exhaust gas and contacting it with a circulating liquid of an absorbing solution to perform desulfurization treatment. A flue gas treatment device comprising: a two-column desulfurization device having a tower; and a wet-type electrostatic precipitator that introduces desulfurized exhaust gas from the two-tower desulfurization device and contacts the water to remove dust. An exhaust gas treatment apparatus, characterized in that a mercury removing agent layer comprising a fixed bed, a moving bed or a fluidized bed of a mercury removing agent is provided in the exhaust gas duct of (1). 14. An exhaust gas treating apparatus according to claim 12, further comprising a mercury removing agent layer comprising a fixed bed, a moving bed, or a fluidized bed of the mercury removing agent in an exhaust gas duct downstream of the wet type electrostatic precipitator. apparatus.