CN110575739A - Method for removing metallic mercury in flue gas - Google Patents

Method for removing metallic mercury in flue gas Download PDF

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Publication number
CN110575739A
CN110575739A CN201910945255.8A CN201910945255A CN110575739A CN 110575739 A CN110575739 A CN 110575739A CN 201910945255 A CN201910945255 A CN 201910945255A CN 110575739 A CN110575739 A CN 110575739A
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flue gas
mercury
wet electrostatic
activated carbon
adsorbent
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王腾飞
杨腾
郜玉森
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Datang Yuncheng Power Generation Co Ltd
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Datang Yuncheng Power Generation Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/64—Heavy metals or compounds thereof, e.g. mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75—Multi-step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/81—Solid phase processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8665—Removing heavy metals or compounds thereof, e.g. mercury
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/02—Plant or installations having external electricity supply
    • B03C3/16—Plant or installations having external electricity supply wet type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/102—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/60—Heavy metals or heavy metal compounds
    • B01D2257/602—Mercury or mercury compounds

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Treating Waste Gases (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

The invention provides a method for removing metallic mercury in flue gas, which comprises the following steps: step 1, enabling flue gas containing metal mercury to enter an SCR (selective catalytic reduction) reactor, reacting with a demercuration catalyst in the SCR reactor, and oxidizing a part of gaseous elemental mercury in the flue gas into bivalent mercury to obtain flue gas A; step 2, enabling the flue gas A to enter a low-low temperature electric precipitator, and removing granular mercury in the flue gas A to obtain flue gas B; step 3, enabling the flue gas B to enter a desulfurizing tower, and removing bivalent mercury in the flue gas B to obtain flue gas C; and 4, reacting the flue gas C with the adsorbent at the air inlet of the wet electrostatic dust collector to obtain flue gas D, and allowing the flue gas D to enter the wet electrostatic dust collector to remove granular mercury and gaseous elemental mercury in the flue gas D. Therefore, the invention has the advantage of effectively removing mercury in the flue gas.

Description

Method for removing metallic mercury in flue gas
Technical Field
The invention belongs to the technical field of thermal power generation, and particularly relates to a method for removing metallic mercury in flue gas.
Background
With the popularization of the ultra-low emission standard in the thermal power industry, more and more pollutant emissions of coal-fired power plants reach the ultra-low emission target, and the ultra-low emission limit standard is implemented for years, so that the atmospheric environment is improved. However, the implementation of the ultra-low emission limit standard does not fundamentally eliminate haze, and particularly in winter, a part of areas can form haze with a certain scale under the condition of low environmental temperature and poor smoke diffusion condition, and the dispute of people, particularly the environmental protection boundary, on the haze cause is also triggered. Although experts say that for the reason of causing haze, the experts propose 32429that the particles PM2.5 which have the greatest influence on the human body in the haze are achieved, and the finer inhalable particles directly pass through alveoli and enter the blood of the human body, so that irreparable harm is caused to the human body. For the exhaust gas of a thermal power plant, PM2.5 mainly forms aerosol nuclei of secondary products such as sulfate and nitrate, which are generated by combining sulfur trioxide and NOx aerosol with metal particles in the atmosphere except smoke dust.
At present, smoke dust and NOx of a thermal power plant are subjected to ultra-low or even ultra-low emission, and sulfur trioxide emission control is urgent; the harm of heavy metals, particularly mercury, in flue gas to the ecological environment is also attracting more and more attention. Mercury is a toxic heavy metal element and is volatile, persistent, and bioaccumulating. The mercury in the atmosphere can enter a human body along with the air through the respiration effect, and can also be deposited into soil and water and finally absorbed by the human body at the terminal along a food chain through an ecosystem, so that mercury pollution has great harm to human beings, animals and plants, fetal development deformity, nervous system abnormality and adult cardiovascular diseases can be caused, and the development of fetuses, infants and adults and the health of adults are seriously harmed. The newly revised and issued 'atmospheric pollutant emission standard of thermal power plant' (GB13223-2011) in China clearly stipulates that the mercury emission concentration of flue gas of the coal-fired power plant is not more than 0.03mg/Nm for the first time3. The mercury emission in the coal burning process accounts for more than 30 percent of the total global emission, so the mercury emission control of the coal burning unit is particularly important, and the coal burningMost of mercury is discharged with flue gas, wherein fly ash accounts for 23.1-26.9%, flue gas accounts for 56.3-69.7%, and mercury entering ash accounts for only about 2%. Therefore, the key to controlling the mercury pollution of the coal is to control the emission of mercury in the flue gas to the atmosphere. As the mercury emission monitoring is carried out later in China and other factors, the regulation of the emission standard on the mercury emission limit value is relatively loose, and the mercury emission standard limit value is more strict with the deepening of people on the understanding of the mercury pollution hazard and the deep research on the mercury removal technology.
However, mercury exists in flue gas in different forms, such as gaseous elemental mercury Hg0Gaseous divalent mercury Hg2+Solid particulate mercury HgpWhen different coal types are combusted under certain conditions, the proportions of forms of mercury released into the atmosphere are different, and the mercury in different forms has different physical and chemical properties. Therefore, no method can effectively and simultaneously remove mercury in various forms in the smoke gas, so that the mercury pollution phenomenon is still serious, and the health of people is threatened.
Disclosure of Invention
the invention provides a method for removing metallic mercury in flue gas, which can effectively remove the content of the metallic mercury in the flue gas.
the technical scheme of the invention is realized as follows: a method for removing metallic mercury in flue gas comprises the following steps:
Step 1, enabling flue gas containing metal mercury to enter an SCR (selective catalytic reduction) reactor, reacting with a demercuration catalyst in the SCR reactor, and oxidizing a part of gaseous elemental mercury in the flue gas into bivalent mercury to obtain flue gas A;
step 2, enabling the flue gas A to enter a low-low temperature electric precipitator, and removing granular mercury in the flue gas A to obtain flue gas B;
Step 3, enabling the flue gas B to enter a desulfurizing tower, and removing bivalent mercury in the flue gas B to obtain flue gas C;
And 4, reacting the flue gas C with the adsorbent at the air inlet of the wet electrostatic dust collector to obtain flue gas D, and allowing the flue gas D to enter the wet electrostatic dust collector to remove granular mercury and gaseous elemental mercury in the flue gas D.
In a preferred embodiment, a desorption interface is arranged at the air inlet of the wet electrostatic dust collector, an adsorbent storage is arranged on one side of the wet electrostatic dust collector, a first pipeline is communicated between the adsorbent storage and the desorption interface, and the adsorbent in the adsorbent storage is injected into the air inlet of the wet electrostatic dust collector through the desorption interface.
The flue gas firstly passes through an SCR reactor and reacts with a demercuration catalyst in the SCR reactor to perform catalytic oxidation on elemental mercury in the flue gas, a part of gaseous elemental mercury in the flue gas is oxidized into bivalent mercury, then the flue gas passes through a low-low temperature electric precipitator and is used for removing dust in the flue gas, wherein the flue gas comprises granular mercury, most of the granular mercury is removed in the low-low temperature electric precipitator, then the flue gas passes through a desulfurizing tower and the bivalent mercury in the flue gas is removed, finally, the flue gas firstly reacts with an adsorbent before passing through a wet electrostatic precipitator to further remove the mercury in the flue gas, and the flue gas further removes the dust and the gaseous elemental mercury in the flue gas after entering the wet electrostatic precipitator, wherein the dust comprises the granular mercury.
As a preferred embodiment, the demercuration catalyst comprises titanium dioxide as a carrier and a catalytic active component loaded on the carrier, wherein the catalytic active component comprises a main active component manganese oxide and a promoter niobium.
as a preferred embodiment, the preparation method of the demercuration catalyst comprises the following steps:
step 1, adding water into a precursor of manganese nitrate of a main active component manganese oxide, stirring for dissolving, adding a precursor of niobium pentoxide, namely niobium nitrate, and uniformly stirring to obtain a composite impregnation solution A;
Step 2, soaking the titanium dioxide powder of the carrier into the composite dipping solution A in the step 1, and continuously stirring for 4-6h under the heating of a water bath at the temperature of 60 ℃ to prepare a composite dipping solution B;
And 3, drying the composite impregnation solution B at 110 ℃ for 10-12h, grinding, placing the ground composite impregnation solution B into a muffle furnace, heating to 350-500 ℃, roasting for 4-6h, taking out the composite impregnation solution B after roasting, and naturally cooling to room temperature to obtain the demercuration catalyst.
In a preferred embodiment, the mass ratio of manganese oxide to niobium pentoxide in the composite impregnation solution a is 1:1 to 10: 1.
Because sulfur dioxide can be adsorbed on the active sites of the demercuration catalyst, in order to avoid the influence of the sulfur dioxide in the flue gas on the demercuration catalyst, the demercuration catalyst and the demercuration catalyst are stored together and injected into the SCR reactor, the sulfur in the flue gas can be removed firstly, and the sulfur content is reduced, so that the catalytic effect of the demercuration catalyst is ensured, and gaseous elementary mercury is catalyzed into bivalent mercury as much as possible for convenient adsorption and removal through the catalytic oxidation action of the demercuration catalyst.
In a preferred embodiment, the adsorbent is sulfur-loaded activated carbon powder.
in a preferred embodiment, the activated carbon powder is divided into two parts before being injected into the wet electrostatic precipitator, wherein one part is soaked by zinc chloride, the other part is soaked by manganese dioxide, and the two parts after soaking are uniformly mixed, dried and stored in the adsorbent storage.
As a preferred embodiment, a spray gun is arranged on one side of the desorption port, a nozzle is arranged on the spray gun, the spray gun is communicated with the nozzle, the nozzle is fixedly arranged on the desorption port, and the first pipeline is communicated with the spray gun and the adsorbent storage.
in a preferred embodiment, one end of the first pipeline is communicated with the spray gun, the other end of the first pipeline is communicated with the air blower, and the adsorbent storage device is arranged between the air blower and the spray gun.
As a preferred embodiment, one side of the adsorbent storage device is connected with a weight-loss feeder
As a preferred embodiment, the demercuration catalyst comprises titanium dioxide as a carrier and a catalytic active component loaded on the carrier, wherein the catalytic active component comprises a main active component manganese oxide and a promoter niobium.
When the activated carbon powder is sprayed, positive pressure air is blown by a blower to be mixed with the activated carbon powder, and the mixture is conveyed to an air inlet of the wet electrostatic precipitator in a gas-solid two-phase flow mode. Before the flue gas enters the wet electrostatic dust collector, mercury in the flue gas can react with halide in the activated carbon and is adsorbed by the activated carbon, and then the flue gas is covered by the wet electrostatic dust collector, and the mercury collected in the fly ash can not be released again, so that the aim of removing mercury is fulfilled.
Furthermore, the activated carbon powder is impregnated by a zinc chloride solution, and the mercury has larger surface tension and contact angle on the activated carbon powder, so that the activated carbon powder is impregnated by a magnesium chloride solution to change the microporous structure of the surface of the activated carbon powder and the structure of functional groups on the surface, thereby improving the mercury adsorption capacity of the activated carbon powder, and the sulfur-loaded activated carbon is adopted to ensure that the mercury is easy to react with sulfur to generate stable compound mercury sulfide, thereby improving the mercury adsorption effect and preventing the mercury from escaping twice, the effective adsorption time of the activated carbon can be greatly increased by impregnating the activated carbon powder by manganese dioxide, which is about 3 times of the original activated carbon, the principle is that the penetration rate of the activated carbon is greatly reduced by using the activated carbon powder impregnated by manganese dioxide, thereby greatly improving the adsorption capacity of the activated carbon powder, and the activated carbon powder not only generates physical adsorption, a strong chemisorption process also occurs.
meanwhile, positive pressure air is blown in by the fan, so that the activated carbon can be contacted with granular mercury to be adsorbed more closely, and the adsorption efficiency and the mercury removal rate are improved.
after the technical scheme is adopted, the invention has the beneficial effects that:
1. The flue gas firstly passes through an SCR reactor and reacts with a demercuration catalyst in the SCR reactor to perform catalytic oxidation on elemental mercury in the flue gas, a part of gaseous elemental mercury in the flue gas is oxidized into bivalent mercury, then the flue gas passes through a low-low temperature electric precipitator and is used for removing dust in the flue gas, wherein the flue gas comprises granular mercury, most of the granular mercury is removed in the low-low temperature electric precipitator, then the flue gas passes through a desulfurizing tower and the bivalent mercury in the flue gas is removed, finally, the flue gas firstly reacts with an adsorbent before passing through a wet electrostatic precipitator to further remove the mercury in the flue gas, and the flue gas further removes the dust and the gaseous elemental mercury in the flue gas after entering the wet electrostatic precipitator, wherein the dust comprises the granular mercury.
2. When the activated carbon powder is sprayed, positive pressure air is blown by a blower to be mixed with the activated carbon powder, and the mixture is conveyed to an air inlet of the wet electrostatic precipitator in a gas-solid two-phase flow mode. Before the flue gas enters the wet electrostatic dust collector, mercury in the flue gas can react with halide in the activated carbon and is adsorbed by the activated carbon, and then the flue gas is covered by the wet electrostatic dust collector, and the mercury collected in the fly ash can not be released again, so that the aim of removing mercury is fulfilled.
3. The active carbon powder is impregnated by the zinc chloride solution, and the mercury has larger surface tension and contact angle on the active carbon powder, so the active carbon powder is impregnated by the magnesium chloride solution to change the microporous structure on the surface of the active carbon powder and the functional group structure on the surface, thereby improving the mercury adsorption capacity of the active carbon powder, while the sulfur-carrying active carbon is adopted, so the mercury is easy to react with sulfur to generate stable compound mercury sulfide, thereby the mercury adsorption effect can be improved, and the mercury can be prevented from escaping twice, the effective adsorption time of the active carbon can be greatly increased by impregnating the active carbon powder by manganese dioxide, which is about 3 times of the original active carbon, the principle is that the penetration rate of the active carbon is greatly reduced by using the impregnated active carbon powder, thereby the adsorption capacity of the active carbon powder is greatly improved, and the active carbon powder can not only generate physical adsorption, a strong chemisorption process also occurs.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of the present invention.
In the figure, 1-SCR reactor; 2-low temperature electric dust collector; 3-a desulfurizing tower; 4-wet electrostatic precipitator; 5-a sorbent reservoir; 6-loss-in-weight feeder; 7-a blower; 8-first conduit.
Detailed Description
the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
as shown in fig. 1, a method for removing metallic mercury from flue gas includes the following steps:
step 1, enabling flue gas containing metal mercury to enter an SCR reactor 1, reacting with a demercuration catalyst in the SCR reactor 1, and oxidizing a part of gaseous elemental mercury in the flue gas into bivalent mercury to obtain flue gas A;
Step 2, enabling the flue gas A to enter a low-low temperature electric dust remover 2, and removing granular mercury in the flue gas A to obtain flue gas B;
Step 3, enabling the flue gas B to enter a desulfurizing tower 3, and removing bivalent mercury in the flue gas B to obtain flue gas C;
and 4, reacting the flue gas C with the adsorbent at the air inlet of the wet electrostatic dust collector 4 to obtain flue gas D, and allowing the flue gas D to enter the wet electrostatic dust collector 4 to remove granular mercury and gaseous elemental mercury in the flue gas D.
A desorption interface is arranged at the air inlet of the wet electrostatic dust collector 4, an adsorbent storage device 5 is arranged on one side of the wet electrostatic dust collector 4, a first pipeline 8 is communicated between the adsorbent storage device 5 and the desorption interface, and the adsorbent in the adsorbent storage device 5 is injected into the air inlet of the wet electrostatic dust collector 4 through the desorption interface.
the flue gas firstly passes through the SCR reactor 1 and reacts with a demercuration catalyst in the SCR reactor 1 to perform catalytic oxidation on elemental mercury in the flue gas, a part of gaseous elemental mercury in the flue gas is oxidized into bivalent mercury, then the flue gas passes through the low-low temperature electric dust remover 2 to remove dust in the flue gas, wherein the flue gas comprises granular mercury, most of the granular mercury is removed in the low-low temperature electric dust remover 2, then the flue gas passes through the desulfurizing tower 3 to remove the bivalent mercury in the flue gas, finally the flue gas firstly reacts with an adsorbent before passing through the wet type electrostatic dust remover 4 to further remove the mercury in the flue gas, and after entering the wet type electrostatic dust remover 4, the dust and the gaseous elemental mercury in the flue gas are further removed, wherein the dust comprises the granular mercury.
The demercuration catalyst comprises titanium dioxide serving as a carrier and a catalytic active component loaded on the carrier, wherein the catalytic active component comprises a main active component manganese oxide and an active auxiliary agent niobium, and the preparation method of the demercuration catalyst comprises the following steps:
Step 1, adding water into a precursor of manganese nitrate of a main active component manganese oxide, stirring for dissolving, adding a precursor of niobium pentoxide, namely niobium nitrate, and uniformly stirring to obtain a composite impregnation solution A;
Step 2, soaking the titanium dioxide powder of the carrier into the composite dipping solution A in the step 1, and continuously stirring for 4-6h under the heating of a water bath at the temperature of 60 ℃ to prepare a composite dipping solution B;
And 3, drying the composite impregnation solution B at 110 ℃ for 10-12h, grinding, placing the ground composite impregnation solution B into a muffle furnace, heating to 350-500 ℃, roasting for 4-6h, taking out the composite impregnation solution B after roasting, and naturally cooling to room temperature to obtain the demercuration catalyst.
The mass ratio of manganese oxide to niobium pentoxide in the composite impregnation solution A is 1:1-10:1, as sulfur dioxide can be adsorbed on active sites of the demercuration catalyst, in order to avoid the influence of the sulfur dioxide in the flue gas on the demercuration catalyst, the demercuration catalyst and the demercuration catalyst are stored together and injected into the SCR reactor 1, sulfur in the flue gas can be removed firstly, the sulfur content is reduced, the catalytic effect of the demercuration catalyst is ensured, and the catalytic oxidation of the demercuration catalyst catalyzes gaseous mercury into bivalent mercury as much as possible, so that the absorption and the removal are convenient.
the injected adsorbent is activated carbon powder. The activated carbon powder is divided into two parts before being injected into the wet electrostatic dust collector 4, wherein one part is soaked by zinc chloride, the other part is soaked by manganese dioxide, the two parts of the impregnated activated carbon powder are uniformly mixed and then dried, and the dried activated carbon powder is stored in the adsorbent storage 5 and is sulfur-loaded activated carbon powder.
And a spray gun is arranged on one side of the desorption interface, a nozzle is arranged on the spray gun, the spray gun is communicated with the nozzle, the nozzle is fixedly arranged on the desorption interface, and the first pipeline 8 is communicated with the spray gun and the adsorbent storage 5. One end of the first pipeline 8 is communicated with the spray gun, the other end of the first pipeline 8 is communicated with the air feeder 7, the adsorbent storage device 5 is arranged between the air feeder 7 and the spray gun, and one side of the adsorbent storage device 5 is connected with the weight-loss feeder 6.
when the activated carbon powder is sprayed, positive pressure air is blown by the blower 7 to be mixed with the activated carbon powder, and the mixture is conveyed to the air inlet of the wet electrostatic precipitator 4 in a gas-solid two-phase flow mode. Before the flue gas enters the wet electrostatic dust collector 4, mercury in the flue gas can react with halide in the activated carbon and is adsorbed by the activated carbon, then the flue gas is covered by the wet electrostatic dust collector 4, and the mercury collected from the fly ash can not be released again, so that the purpose of removing mercury is achieved.
furthermore, the activated carbon powder is impregnated by a zinc chloride solution, and the mercury has larger surface tension and contact angle on the activated carbon powder, so that the activated carbon powder is impregnated by a magnesium chloride solution to change the microporous structure of the surface of the activated carbon powder and the structure of functional groups on the surface, thereby improving the mercury adsorption capacity of the activated carbon powder, and the sulfur-loaded activated carbon is adopted to ensure that the mercury is easy to react with sulfur to generate stable compound mercury sulfide, thereby improving the mercury adsorption effect and preventing the mercury from escaping twice, the effective adsorption time of the activated carbon can be greatly increased by impregnating the activated carbon powder by manganese dioxide, which is about 3 times of the original activated carbon, the principle is that the penetration rate of the activated carbon is greatly reduced by using the activated carbon powder impregnated by manganese dioxide, thereby greatly improving the adsorption capacity of the activated carbon powder, and the activated carbon powder not only generates physical adsorption, a strong chemisorption process also occurs.
Meanwhile, positive pressure air is blown in by the fan, so that the activated carbon can be contacted with granular mercury to be adsorbed more closely, and the adsorption efficiency and the mercury removal rate are improved.
By taking 40% of gaseous elementary mercury and 60% of ionic and granular mercury, 80-90% of oxidation state bivalent mercury in the flue gas can be removed by the desulfurizing tower 3, and the removing effect on the gaseous mercury in the flue gas is obvious; the wet electrostatic dust collector 4 has a removing effect on the granular mercury and has a removing efficiency of 20-30% on the ionic mercury in the flue gas, the removing efficiency of the ionic mercury and the granular mercury can reach 96-97% by using the SCR reactor 1, the desulfurizing tower 3 and the wet electrostatic dust collector 4 to remove the mercury jointly, and the emission concentration of the mercury can reach 0.015mg/Nm3Already greatly lower than the national standard of 0.03mg/Nm3However, when the mercury removal catalyst is matched, the emission concentration of mercury can reach less than 0.0045mg/Nm3Then the activated carbon powder is matched for adsorption, so that the emission concentration of mercury can reach less than 0.0036mg/Nm3respectively soaking activated carbon powder in zinc chloride solution and manganese dioxide solution, and blowing under positive pressure of blower 7 to make the emission concentration of mercury reach less than 0.0025mg/Nm3Far below the national standard, and reaches the advanced level in the world.
the present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. a method for removing metallic mercury in flue gas is characterized by comprising the following steps:
Step 1, enabling flue gas containing metal mercury to enter an SCR (selective catalytic reduction) reactor, reacting with a demercuration catalyst in the SCR reactor, and oxidizing a part of gaseous elemental mercury in the flue gas into bivalent mercury to obtain flue gas A;
Step 2, enabling the flue gas A to enter a low-low temperature electric precipitator, and removing granular mercury in the flue gas A to obtain flue gas B;
Step 3, enabling the flue gas B to enter a desulfurizing tower, and removing bivalent mercury in the flue gas B to obtain flue gas C;
And 4, reacting the flue gas C with the adsorbent at the air inlet of the wet electrostatic dust collector to obtain flue gas D, and allowing the flue gas D to enter the wet electrostatic dust collector to remove granular mercury and gaseous elemental mercury in the flue gas D.
2. The method for removing metallic mercury from flue gas as claimed in claim 1, wherein a removal interface is provided at an air inlet of the wet electrostatic precipitator, an adsorbent storage is provided at one side of the wet electrostatic precipitator, a first pipeline is provided between the adsorbent storage and the removal interface, and the adsorbent in the adsorbent storage is injected into the air inlet of the wet electrostatic precipitator through the removal interface.
3. The method for removing metallic mercury in flue gas according to claim 1, wherein the demercuration catalyst comprises titanium dioxide as a carrier and a catalytically active component loaded on the carrier, and the catalytically active component comprises a main active component manganese oxide and a promoter niobium.
4. The method for removing metallic mercury in flue gas according to claim 3, wherein the preparation method of the demercuration catalyst comprises the following steps:
Step 1, adding water into a precursor of manganese nitrate of a main active component manganese oxide, stirring for dissolving, adding a precursor of niobium pentoxide, namely niobium nitrate, and uniformly stirring to obtain a composite impregnation solution A;
Step 2, soaking the titanium dioxide powder of the carrier into the composite dipping solution A in the step 1, and continuously stirring for 4-6h under the heating of a water bath at the temperature of 60 ℃ to prepare a composite dipping solution B;
and 3, drying the composite impregnation solution B at 110 ℃ for 10-12h, grinding, placing the ground composite impregnation solution B into a muffle furnace, heating to 350-500 ℃, roasting for 4-6h, taking out the composite impregnation solution B after roasting, and naturally cooling to room temperature to obtain the demercuration catalyst.
5. The method for removing metallic mercury in flue gas according to claim 4, wherein the mass ratio of manganese oxide to niobium pentoxide in the composite impregnation solution A is 1:1-10: 1.
6. The method for removing metallic mercury in flue gas according to claim 2, wherein the adsorbent is sulfur-loaded activated carbon powder.
7. The method according to claim 6, wherein the activated carbon powder is divided into two parts before being injected into the wet electrostatic precipitator, one part is soaked with zinc chloride, the other part is soaked with manganese dioxide, the two parts after soaking are uniformly mixed and then dried, and the dried activated carbon powder is stored in the adsorbent storage.
8. The method for removing metallic mercury from flue gas as claimed in claim 2, wherein a spray gun is arranged on one side of the removal port, a nozzle is arranged on the spray gun, the spray gun is communicated with the nozzle, the nozzle is fixedly arranged on the removal port, and the first pipeline is communicated with the spray gun and the adsorbent storage.
9. The method according to claim 8, wherein one end of the first pipeline is communicated with a spray gun, the other end of the first pipeline is communicated with a blower, and the adsorbent storage device is arranged between the blower and the spray gun.
10. The method according to claim 9, wherein a weight-loss feeder is connected to one side of the adsorbent storage.
CN201910945255.8A 2019-09-30 2019-09-30 Method for removing metallic mercury in flue gas Pending CN110575739A (en)

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