CN108889110B - Method for removing mercury from flue gas - Google Patents

Method for removing mercury from flue gas Download PDF

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CN108889110B
CN108889110B CN201810897328.6A CN201810897328A CN108889110B CN 108889110 B CN108889110 B CN 108889110B CN 201810897328 A CN201810897328 A CN 201810897328A CN 108889110 B CN108889110 B CN 108889110B
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mercury
flue gas
mercury removal
removing agent
sulfur
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CN108889110A (en
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王姣
赵凯
杜士帽
马小乐
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China ENFI Engineering Corp
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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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/77—Liquid phase processes
    • B01D53/79—Injecting reactants
    • 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
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B01D53/502—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound characterised by a specific solution or suspension
    • 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
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • B01D53/507—Sulfur oxides by treating the gases with other liquids
    • 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
    • B01D2251/00—Reactants
    • B01D2251/30—Alkali metal compounds
    • B01D2251/304—Alkali metal compounds of sodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/60—Inorganic bases or salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/60—Inorganic bases or salts
    • B01D2251/608—Sulfates
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • B01D2258/0283—Flue gases

Abstract

The invention provides a mercury removal method for flue gas. The mercury removal method comprises the following steps: the method comprises the following steps of carrying out mercury removal treatment on the flue gas by using a mercury removal agent, reacting the mercury removal agent with sulfur dioxide in the flue gas to generate a sulfur simple substance in the mercury removal treatment process, and treating mercury in the flue gas through the sulfur simple substance. The high-activity sulfur elementary substance with high dispersity generated in the reaction process of the mercury removing agent and sulfur dioxide in the flue gas can more effectively react with gaseous mercury in the flue gas to form mercury sulfide so as to remove the system, and redundant sulfur elementary substance formed by reaction can be discharged out of the system along with the product mercury sulfide. Therefore, the method is beneficial to mercury removal of the flue gas, and excessive hydrogen sulfide concentration is avoided due to the existence of the redundant elemental sulfur, so that the negative influence of the excessive hydrogen sulfide concentration on a subsequent sulfuric acid system is avoided.

Description

Method for removing mercury from flue gas
Technical Field
The invention relates to the technical field of flue gas mercury removal, in particular to a flue gas mercury removal method.
Background
At present, the mercury removal technology for flue gas mainly comprises a chlorination method, an activated carbon method, a sodium sulfide method, a selenium filtering method, a sulfuric acid washing method, a potassium iodide method, an ozone method, an SCR method and the like, and is used under different flue gas conditions. Wherein, the chlorination method, the iodine complexing-electrolysis method, the sulfuric acid washing method and the sodium sulfide method are used for the nonferrous smelting flue gas. The main application characteristics of the main flue gas mercury removal method are as follows:
a chlorination method: also known as the Boliden-Norzink mercury removal method, was originally introduced in China by the Boliden company. The method is used for removing gaseous zero-valent mercury in the smelting flue gas, and calomel can be produced or mercury simple substance can be obtained through electrolysis. Both products are not stable enough to be handled as end products and must be further processed into other products. However, the downstream application of mercury in the industry is less and less at present, which limits the application of the method.
The main chemical reactions taking place during mercury removal are as follows:
Hg0+HgCl2→Hg2Cl2↓ (calomel) (absorption process)
Hg2Cl2+Cl2→2HgCl2(Chlorination step)
HgCl2→Hg+Cl2(electrolytic Process)
If the by-product is calomel, the production does not have an electrolytic process and consumes a large amount of chlorine.
Activated carbon method: the activated carbon adsorption process was originally used for the emission of mercury from waste incineration. The activated carbon has strong adsorbability on a plurality of acid gases, so that the mercury in the flue gas cannot be selectively removed, and the application has certain limitation.
③ Potassium iodide method: the potassium iodide method is a method for removing mercury from smelting flue gas in Guangdong Shaoshao smelting plant, and is applied to the plant. However, the potassium iodide solution has high cost, so the method is not popularized and applied in other plants.
The main chemical reaction equation of the mercury removal process is as follows:
H2SO3+2Hg0(gaseous) +4H++8I-→2[HgI4]2-+S↓+3H2O (absorption Process)
[HgI4]2-→Hg0(liquid) + I2+2I-(electrolytic Process)
I2+H2SO3+H2O→2HI+H2SO4
The main chemical reaction equation for the treatment of the absorption cycle mother liquor is as follows:
3Hg+8HNO3→3Hg(NO3)2+2NO↑+4H2o (Mercury nitrate preparation)
K2[HgI4]+Hg(NO3)2＝2HgI2↓+2KNO3(precipitated mercuric iodide)
HgI2+2I-＝[HgI4]2-(dissolving mercuric iodide)
Fourthly, selenium filtering method: the method removes Hg in flue gas by utilizing the affinity between Hg and Se0. Since HgSe is a stable compound, it can be landfilled as a final product. However, the method has high cost and is mainly used for trace mercury in flue gasAnd (5) removing.
The chemical reaction equation of the mercury removal process is as follows:
Hg+Se→HgSe
sodium sulfide method: the technology is developed for Japan, and can remove Hg and simple substance in flue gas2+. The spraying of the sodium sulfide solution is difficult in quantification, and the spraying of the sodium sulfide into the hydrogen sulfide excessively generated has adverse effect on the conversion process of the smelting sulfuric acid system. Therefore, the method is mainly used for the pretreatment of a system for preparing sulfuric acid from smelting flue gas as a mercury removal technology by a chlorination method and a mercury removal technology by potassium iodide.
The main chemical reaction equation of the mercury removal process is as follows:
Na2S+SO2(in the gaseous state, or as CO)2)+H2O→Na2SO3(or is Na)2CO3)+H2S (acidification)
2Hg0(gaseous) +2H2S+O2→2HgS+2H2O (removal of Hg0)
Hg2++H2S→HgS+2H+(removal of Hg)2+)
The main disadvantages of the existing flue gas mercury removal technology can be divided into the following categories: the flue gas mercury removal effect is obvious, but the flue gas mercury removal effect can not adapt to a complex system, the mercury removal selectivity is poor, and the application range of the mercury removal technology is limited, such as: activated carbon method, ozone method. The absorbent for removing mercury from flue gas is high in cost, such as: potassium iodide process, selenium filtration process. The by-products from the mercury removal of flue gases do not yield stable compounds and are further treated. Without downstream industry cooperation, this technology is limited in its application, such as: a chlorination process. Mercury removal processes can have adverse effects on the process flow if not properly controlled, and therefore cannot be deeply mercury removed, often as a pre-mercury removal measure, such as: the sodium sulfide method.
Therefore, at present, sodium sulfide is used as a mercury removing agent and is mostly used for a system for producing sulfuric acid by smelting flue gas as pretreatment of mercury removing technology by a chlorination method and a potassium iodide method. However, the spraying of the sodium sulfide solution has a problem that it is difficult to quantify and it is easy to overdose. The spraying of the sodium sulfide into the excessively generated hydrogen sulfide has adverse effects on the conversion process of a sulfuric acid system, water generation, severe local overtemperature in the oxidation process and the like.
Disclosure of Invention
The invention mainly aims to provide a method for removing mercury from flue gas, which aims to solve the problem that in the prior art, sodium sulfide is adopted as a mercury removing agent to easily generate excessive hydrogen sulfide to cause adverse effects on the conversion process of a sulfuric acid system.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for removing mercury from flue gas, comprising the steps of: the flue gas is subjected to mercury removal treatment by using a mercury removal agent, and the mercury removal agent is a reagent capable of reacting with sulfur dioxide in the flue gas to generate a sulfur simple substance.
Further, the mercury removing agent includes any one or more of polysulfide, thiosulfate and organic sulfide.
Further, the polysulfide includes Na2SXOr CaSX，x＝1-6。
Further, the organic sulfide includes any one or more of ethanethiol, sodium dimethyldithiocarbamate and sodium dimercaptopropanesulfonate.
Further, the concentration of mercury in the flue gas is 10-800 mg/Nm3。
Further, the temperature of the mercury removal treatment is 25-200 ℃.
Further, in the step of mercury removal treatment, the mercury removal agent is dissolved in the solvent to prepare a mercury removal agent solution, and then the mercury removal agent solution is sprayed into the reactor with the flue gas to carry out mercury removal treatment, preferably, the flue gas and the mercury removal agent solution are in concurrent contact.
Further, the weight concentration of the mercury removing agent in the mercury removing agent solution is 5-25%.
Further, the spraying pressure of the mercury removing agent solution is 0.3-1.0 MPa.
Further, the flow velocity of the flue gas is 2-8 m/s.
Further, compressed air is introduced into the reactor, and the pressure of the compressed air is preferably 0.6-1.2 MPa.
The technical scheme of the invention provides a method for removing mercury from flue gas, which utilizes a mercury removing agent to remove mercury from flue gas, wherein in the process of removing mercury, the mercury removing agent reacts with sulfur dioxide in flue gas to generate elemental sulfur, and mercury in flue gas is treated by the elemental sulfur. The high-activity sulfur elementary substance with high dispersity generated in the reaction process of the mercury removing agent and sulfur dioxide in the flue gas can more effectively react with gaseous mercury in the flue gas to form mercury sulfide so as to remove the system, and redundant sulfur elementary substance formed by reaction can be discharged out of the system along with the product mercury sulfide. Therefore, the method is beneficial to mercury removal of the flue gas, and excessive hydrogen sulfide concentration is avoided due to the existence of the redundant elemental sulfur, so that the negative influence of the excessive hydrogen sulfide concentration on a subsequent sulfuric acid system is avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic structural diagram of a mercury removal device for flue gas provided by the invention; and
fig. 2 is a schematic top view of a cyclone flow deflector in the mercury removal device shown in fig. 1.
Wherein the figures include the following reference numerals:
10. a reactor body; 110. a flue gas channel; 20. an ejector; 30. a swirl flow deflector; 310. a guide vane; 40. a solids collection device; 50. and (5) flushing the device.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make the technical solutions of the present invention better understood, 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.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
As described in the background, the prior art using sodium sulfide as a mercury removing agent tends to generate excessive hydrogen sulfide which adversely affects the conversion process of the sulfuric acid system. The inventor of the present application researches the above problems and provides a method for removing mercury from flue gas, comprising the following steps: the method comprises the step of carrying out mercury removal treatment on flue gas by using a mercury removal agent, wherein the mercury removal agent is a reagent capable of reacting with sulfur dioxide in the flue gas to generate elemental sulfur. Preferably, the elemental sulfur generated during the mercury removal treatment is in excess compared to the mercury in the flue gas.
According to the mercury removal method, the mercury removal agent is used for removing mercury from the flue gas, so that the high-activity elemental sulfur with high dispersity generated in the reaction process of the mercury removal agent and sulfur dioxide in the flue gas can more effectively react with gaseous mercury in the flue gas to form mercury sulfide in the flue gas in the mercury removal treatment process, a system is removed, and redundant elemental sulfur formed in the reaction process can be discharged out of the system along with the product mercury sulfide. Therefore, the method is beneficial to mercury removal of the flue gas, and excessive hydrogen sulfide concentration is avoided due to the existence of the redundant elemental sulfur, so that the negative influence of the excessive hydrogen sulfide concentration on a subsequent sulfuric acid system is avoided.
An exemplary embodiment of a method for mercury removal from flue gas provided in accordance with the present invention will now be described in more detail. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art.
The method comprises the steps of utilizing a mercury removing agent to remove mercury from flue gas, enabling the mercury removing agent to react with sulfur dioxide in the flue gas to generate a sulfur simple substance through reasonably selecting the type of the mercury removing agent in the process of mercury removal treatment, enabling the sulfur simple substance to react with mercury in the flue gas to generate a chemical reaction in the process of mercury removal, and enabling hydrogen sulfide in the flue gas to react with mercury to remove the mercury.
The main chemical reaction equation of the mercury removal process is as follows:
2Hg0(gaseous) +2H2S+O2→2HgS+2H2O
Hg0(gaseous) + S → HgS
In a preferred embodiment, the mercury removing agent comprises any one or more of polysulfides, thiosulfates and organic sulfides, and the thiosulfates are preferably sodium thiosulfates. The mercury removing agent can comprise any two or three of polysulfide, thiosulfate and organic sulfide to form a composite mercury removing agent; determining the components in the composite mercury removing agent according to the concentration and fluctuation range of Hg in the flue gas, and determining the proportion of each component in the composite mercury removing agent according to the concentration of Hg in the flue gas.
The mercury removing agent is adopted to be fully contacted with the flue gas, at least one of the mercury removing agents and components in the flue gas are subjected to chemical reaction to generate elemental sulfur and hydrogen sulfide, then the elemental sulfur is subjected to chemical reaction with gaseous mercury in the flue gas and possibly existing bivalent mercury and is converted into mercury sulfide, the possibly generated hydrogen sulfide is subjected to chemical reaction with the gaseous mercury in the flue gas and is also converted into mercury sulfide, and finally the mercury in the flue gas is removed, wherein the mercury removing process mainly comprises the following chemical reactions:
2Hg0(gaseous) +2H2S+O2→2HgS+2H2O
Hg0(gaseous) + S → HgS
The composite mercury removing agent can be formed by multiple components, and the yield of the intermediate product hydrogen sulfide and the sulfur simple substance is controlled at a certain proportion by proportioning design of the components in the composite mercury removing agent, so that the high activity of hydrogen sulfide reaction can be utilized, and the risk of excessive hydrogen sulfide can be avoided; meanwhile, the generated elemental active sulfur (such as sulfur) can be discharged along with the product mercuric sulfide, and the negative influence on a system for preparing sulfuric acid from smelting flue gas can be avoided.
In order to ensure that the mercury removing agent can react to generate elemental sulfur and optional hydrogen sulfide after contacting with the flue gas, preferably, the mercury removing agent comprises polysulfide comprising Na2SXOr CaSXAnd x is 1-6; also, preferably, the above-mentioned organic sulfide includes any one or more of ethanethiol, sodium dimethyldithiocarbamate and sodium dimercaptopropanesulfonate.
In order to improve the mercury removal efficiency of the mercury removal agent on the flue gas, preferably, the concentration of mercury in the flue gas is 10-800 mg/Nm3(ii) a And, preferably, the temperature of the mercury removal treatment is 25 to 200 ℃.
In the step of mercury removal treatment, preferably, the mercury removal agent is dissolved in the solvent to prepare a mercury removal agent solution, and then the mercury removal agent solution is sprayed into the reactor through which the flue gas is introduced to perform the mercury removal treatment. The mercury removing agent is sprayed into the reactor, so that gas-liquid contact in the reactor can keep a smaller liquid-gas ratio, the gas-liquid mass transfer effect is increased by using the smaller liquid-gas ratio, the mercury removing agent can be fully contacted with mercury vapor in the flue gas, and the mercury removing efficiency of the mercury removing agent on the flue gas is improved; more preferably, the flue gas is contacted with the mercury removing agent solution in a concurrent flow manner. In the gas-liquid contact, the liquid amount is small, and the liquid is taken away by the gas in a countercurrent contact mode, so that the flow direction is changed.
Since the activity of the mercury removing agent solution is reduced due to too high concentration of the mercury removing agent solution, and the solubility of the mercury removing agent solution is reduced due to too high concentration of the mercury removing agent solution, in order to improve the mercury removing efficiency of the mercury removing agent on flue gas, the weight concentration of the mercury removing agent in the mercury removing agent solution is preferably 5-25%.
In the process of injecting the mercury removing agent solution into the reactor, as shown in fig. 1, the reactor used may include a reactor body 10 and an injector 20, the reactor body 10 includes a flue gas channel 110, and the injector 20 is disposed in the flue gas channel 110 and is used for injecting the mercury removing agent into the flue gas channel 110 to contact with the flue gas and remove mercury from the flue gas.
Further, the reactor may further include a rotational flow guide plate 30 and a solid collecting device 40, the rotational flow guide plate 30 is located on the rotational flow guide plate 30 on the side of the injector 20 close to the flue gas outlet, and the rotational flow guide plate 30 is used to generate turbulence to increase the gas-liquid contact time and contact probability and promote the gas-liquid reaction and the gas-liquid reaction, the rotational flow guide plate 30 includes a plurality of layers of rotatable guide vanes 310, and the rotation directions of adjacent guide vanes are opposite, as shown in fig. 2; the solid collecting device 40 is located on one side of the ejector 20 close to the flue gas outlet, and is used for collecting solid substances such as mercury sulfide and sulfur generated after the flue gas contacts with the mercury removing agent, and a flushing device 50 can be further arranged on the solid collecting device 40 to flush the solid collecting device 40. The reaction products of the flue gas and the mercury removing agent are separated from the gas by impinging on the solids collection means 40 to enlarge the solid particles in the reaction products.
In order to further improve the mercury removal efficiency of the mercury removal agent on the flue gas, preferably, the spraying pressure of the mercury removal agent solution is 0.3-1.0 MPa; preferably, the flow velocity of the flue gas is 2-8 m/s; and if the mercury removing agent is small in dosage and inconvenient to disperse, a compressed air dispersing mode can be adopted, namely compressed air is introduced into the reactor, and preferably the pressure of the compressed air is 0.6-1.2 MPa.
The method for removing mercury from flue gas provided by the present invention will be further described with reference to examples and comparative examples.
Example 1
The mercury removal method provided by the embodiment comprises the following steps:
80mg/Nm of elemental mercury in flue gas3Cigarette (D)The water content in the gas is nearly saturated, and the composite mercury removing agent adopts Na2S and Na2S2O3And preparing a mixed solution with water, wherein the mass concentration of the composite mercury removing agent in the solution is 4%, 1 high-pressure ejector is arranged in the mercury removing reactor, the flue gas is introduced into the reactor, the flow rate is 1.5m/s, the composite mercury removing agent is sprayed in through the high-pressure ejector and is in concurrent contact with the flue gas, the spraying pressure is 0.2MPa, and the reaction temperature for removing mercury from the flue gas is 23 ℃.
Example 2
The mercury removal method provided in this example is different from that of example 1 in that:
the mass concentration of the composite mercury removing agent in the mixed solution containing the composite mercury removing agent is 5 percent.
Example 3
The mercury removal method provided in this example is different from that of example 1 in that:
the mass concentration of the composite mercury removing agent in the mixed solution containing the composite mercury removing agent is 25 percent.
Example 4
The mercury removal method provided in this example is different from that of example 3 in that:
and introducing the flue gas into the reactor at the flow speed of 2m/s, spraying the composite mercury removing agent through a high-pressure sprayer and enabling the composite mercury removing agent to be in concurrent contact with the flue gas, wherein the spraying pressure is 0.3 MPa.
Example 5
The mercury removal method provided in this example is different from that of example 3 in that:
and introducing the flue gas into the reactor at the flow speed of 8m/s, spraying the composite mercury removing agent through a high-pressure sprayer and enabling the composite mercury removing agent to be in concurrent contact with the flue gas, wherein the spraying pressure is 1 MPa.
Example 6
The mercury removal method provided in this example is different from that of example 5 in that:
the reaction temperature for removing mercury from flue gas is 25 ℃.
Example 7
The mercury removal method provided in this example is different from that of example 5 in that:
the reaction temperature for removing mercury from flue gas is 200 ℃.
Example 8
The mercury removal method provided in this example differs from example 7 in that:
the concentration of mercury in the flue gas is 800mg/Nm3。
Example 9
The mercury removal method provided by the embodiment comprises the following steps:
elemental mercury in flue gas is 10mg/Nm3The water content in the smoke is close to saturation, and the composite mercury removing agent adopts sodium dimercaptopropane sulfonate and Na2S2O3And preparing a mixed solution with water, wherein the mass concentration of the composite mercury removing agent in the solution is 8%, 2 high-pressure ejectors are arranged in the mercury removing reactor, the flue gas is introduced into the reactor, the flow rate is 4m/s, the composite mercury removing agent passes through the high-pressure ejectors, the ejection pressure is 0.6MPa, the composite mercury removing agent is mixed with 0.4MPa compressed air and is ejected into the reactor and is in downstream contact with the flue gas, and the reaction temperature for removing mercury from the flue gas is 120 ℃.
Example 10
The mercury removal method provided by the embodiment comprises the following steps:
elemental mercury in flue gas 40mg/Nm3The water content of the flue gas is far lower than the saturated content, and Na is adopted as the composite mercury removing agent2S and sodium dimercaptosulphonate and water are prepared into a mixed solution, the mass concentration of the composite mercury removing agent in the solution is 8 percent, 1 high-pressure ejector is arranged in a mercury removing reactor, the flue gas is introduced into the reactor, the flow rate is 4m/S, the composite mercury removing agent and compressed air are ejected through the high-pressure ejector and are in concurrent contact with the flue gas, the ejection pressure is 0.4MPa, and the reaction temperature for removing mercury from the flue gas is 100 ℃.
Comparative example 1
The mercury removal method provided by the comparative example comprises the following steps:
80mg/Nm of elemental mercury in flue gas3The moisture in the smoke is close to saturation, and Na is adopted as a mercury removing agent2S and water are prepared into mixed solution, the mass concentration of the mercury removing agent in the solution is 10%, 1 high-pressure ejector is arranged in the mercury removing reactor, the flue gas is introduced into the reactor, the flow rate is 4m/S, the mercury removing agent is ejected through the high-pressure ejector and is in downstream contact with the flue gas, and the ejection pressure is 0.8MPand a, the reaction temperature of the flue gas for removing mercury is 38 ℃.
The concentrations of the respective components in the flue gas discharged from the reactors in the above examples 1 to 10 and comparative example 1 were analyzed after 0.2s to 1s of mercury removal from the flue gas, and the solid matters generated in the reactors were collected while performing content analysis, and the results are shown in the following table.
Figure BDA0001758520350000071
Figure BDA0001758520350000081
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
1. the mercury removing agent reacts with sulfur dioxide in the flue gas to generate high-activity elemental sulfur with high dispersity, the elemental sulfur can more effectively react with gaseous mercury in the flue gas to form mercury sulfide so as to be discharged out of the system, and redundant elemental sulfur formed by the reaction can be discharged out of the system along with the product mercury sulfide, so that mercury removal of the flue gas is facilitated, excessive concentration of hydrogen sulfide is avoided due to the existence of the redundant elemental sulfur, and negative influence of the excessive concentration of hydrogen sulfide on a subsequent sulfuric acid system is avoided;
2. the mercury removing agent is sprayed into the reactor, so that gas-liquid contact in the reactor can keep a smaller liquid-gas ratio, the gas-liquid mass transfer effect is increased by using the smaller liquid-gas ratio, the mercury removing agent can be fully contacted with mercury vapor in flue gas, and the mercury removing efficiency of the mercury removing agent on the flue gas is improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. The mercury removal method for the flue gas is characterized by comprising the following steps:
the flue gas is subjected to mercury removal treatment by using a mercury removal agent, the mercury removal agent is a reagent capable of reacting with sulfur dioxide in the flue gas to generate elemental sulfur,
the mercury removing agent comprises a plurality of polysulfide, thiosulfate and organic sulfide,
the concentration of mercury in the flue gas is 10-800 mg/Nm3，
The temperature of the mercury removal treatment is 25-200 ℃,
in the step of mercury removal treatment, the mercury removal agent is dissolved in a solvent to prepare a mercury removal agent solution, and then the mercury removal agent solution is sprayed into a reactor filled with the flue gas to carry out the mercury removal treatment,
the weight concentration of the mercury removing agent in the mercury removing agent solution is 5-25%.
2. The method of claim 1, wherein the polysulfide comprises Na2SXOr CaSX，x＝1-6。
3. The method of claim 1, wherein the organosulfide includes any one or more of ethanethiol, sodium dimethyldithiocarbamate and sodium dimercaptopropanesulfonate.
4. The mercury removal method of claim 1, wherein the flue gas is contacted with the mercury removing agent solution in a concurrent flow.
5. The mercury removal method of claim 1, wherein the injection pressure of the mercury removing agent solution is 0.3-1.0 MPa.
6. The mercury removal method of claim 5, wherein the flow velocity of the flue gas is 2-8 m/s.
7. The method of claim 5, wherein the reactor is further charged with compressed air.
8. The mercury removal method of claim 7, wherein the pressure of the compressed air is 0.6-1.2 MPa.
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