Halogen injection mercury removal method and device for coal-fired flue gas

Abstract

The embodiment of the invention relates to the technical field of coal-fired flue gas demercuration, and provides a coal-fired flue gas halogen injection demercuration method and a coal-fired flue gas halogen injection demercuration device. A halogen injection newly-added hydrogen chloride concentration limit value can be determined by using a halogen injection newly-added hydrogen chloride concentration limit value calculation formula determined based on the environmental protection tax cost of mercury, and the halogen injection newly-added hydrogen chloride concentration in the coal-fired flue gas halogen injection mercury removal process is controlled according to the halogen injection newly-added hydrogen chloride concentration limit value. The mercury in the coal-fired gas can be removed without wasting halogen, and the balance between the environmental protection tax cost of the mercury and the mercury removal cost of the coal-fired gas is achieved, so that the total cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of mercury removal from coal-fired flue gas, and in particular to a method and device for mercury removal from coal-fired flue gas by halogen injection. Background Art

[0002] Mercury in coal-fired flue gas usually exists in three forms: elemental mercury Hg 0 , Oxidized mercury Hg 2+ and particulate mercury Hg p Among them, elemental mercury Hg 0 Insoluble in water, highly volatile, difficult to capture and remove, but can be partially oxidized to Hg in a selective catalytic reduction (SCR) denitrification reactor 2+ . Oxidized mercury Hg 2+ Easily absorbed by the slurry in the desulfurization device. Particle-state mercury Hg p When passing through the dust collector, most of it will be captured into fly ash. Therefore, it is necessary to remove elemental mercury Hg as much as possible. 0 , which can effectively reduce the final emission concentration of mercury.

[0003] Conventional methods for synergistic mercury removal usually use elemental mercury Hg 0 Converted to oxidized mercury Hg 2+ The oxidized mercury Hg is removed by the subsequent desulfurization device 2+ In the SCR denitration reactor, the denitration catalyst converts elemental mercury Hg 0 Oxidation to Hg 2+ The reaction equation is: in, Represents the active site of the catalyst. In this process, there are two key factors: the catalyst and the concentration of halogen elements. Under the condition that the mercury oxidation performance of the catalyst itself is constant, as the concentration of HCl / HBr in the flue gas increases, the catalyst's oxidation efficiency of elemental mercury increases rapidly. Therefore, by increasing the concentration of halogen elements in the SCR reactor, Hg 0 Converted to Hg 2+ proportion.

[0004] Halogen injection demercuration technology is based on existing ultra-low emission facilities such as SCR denitration, high-efficiency dust collector and wet desulfurization. By injecting halogen-containing (Cl, Br, I) solution into the upstream flue of SCR denitration, high-temperature hot flue gas is decomposed or gasified to increase the concentration of halogen-containing gas in the flue gas, thereby effectively improving the SCR denitration catalyst to elemental mercury Hg 0 The oxidizing capacity of the flue gas is improved, and finally the efficient synergistic removal of flue gas mercury pollutants is achieved. However, the halogen injection mercury removal technology has the problems of poor economic efficiency and unclear mercury removal efficiency.

[0005] At present, the mercury emissions of most coal-fired power plants are lower than the environmental protection standards. Although the mercury emissions of some coal-fired power plants meet the environmental protection standards, their mercury pollutant equivalents may exceed the particulate pollutant equivalents. This means that when coal-fired power plants pay environmental protection taxes according to the top three pollutant equivalents of the same pollution source, they may pay mercury taxes, thereby increasing the environmental protection tax costs. Therefore, in order to reduce the environmental protection tax costs, coal-fired power plants also need to use halogen injection demercuration technology to reduce mercury emissions, thereby reducing environmental protection taxes. However, the use of halogen injection demercuration technology also has operating costs. On this basis, how to balance the demercuration costs of coal-fired power plants and the environmental protection tax costs has become an urgent problem to be solved in this field. Summary of the invention

[0006] The present disclosure aims to solve at least one of the problems existing in the prior art and to provide a method and device for removing mercury from coal-fired flue gas by halogen injection.

[0007] In one aspect of the present disclosure, a method for removing mercury from coal-fired flue gas by halogen injection is provided, the method comprising:

[0008] Obtain the mercury content and chlorine content of coal in coal-fired units;

[0009] Based on the mercury content of the coal and the chlorine content of the coal, the limit value of the concentration of hydrogen chloride added by the injection of halogen is determined by using a predetermined calculation formula for the limit value of the concentration of hydrogen chloride added by the injection of halogen; wherein the calculation formula for the limit value of the concentration of hydrogen chloride added by the injection of halogen is determined based on the environmental protection tax cost of mercury;

[0010] According to the newly added hydrogen chloride concentration limit of the halogen injection, the halogen injection mercury removal technology is used to remove mercury in the coal-fired flue gas discharged from the coal-fired unit.

[0011] Optionally, the process of determining the calculation formula for the limit value of the concentration of hydrogen chloride added by the injection of halogen includes a halogen injection demercuration test, the halogen injection demercuration test is carried out in an SCR reactor, and the coal-fired flue gas is sequentially demercured by the SCR reactor, the dust collector, and the desulfurization device before being discharged through a chimney;

[0012] The step of determining the calculation formula for the limit value of the concentration of hydrogen chloride added by the injected halogen comprises:

[0013] When the coal-fired unit is operating normally, the coal is tested for mercury content and chlorine content, and the coal-fired flue gas is tested for mercury content and hydrogen chloride content at the inlet of the SCR reactor to obtain the corresponding relationship between the initial mercury content of the coal-fired flue gas and the mercury content of the coal, and the corresponding relationship between the initial hydrogen chloride concentration of the coal-fired flue gas and the chlorine content of the coal;

[0014] Defining a mercury oxidation conversion rate of the SCR reactor to convert elemental mercury into oxidized mercury, performing a mercury concentration test at the outlet of the SCR reactor, and determining a relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor;

[0015] During the halogen injection mercury removal test, a hydrogen chloride concentration test and a mercury oxidation conversion rate test are performed at the inlet of the SCR reactor, and a mercury concentration test is performed at the outlet of the desulfurization device to determine a relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration, and to determine a relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor;

[0016] According to the relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor, determining a relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor, and the mercury content of the coal;

[0017] Calculate the environmental tax on mercury emissions based on the mercury concentration at the outlet of the desulfurization device, and calculate the environmental tax on particulate matter emissions based on the concentration of particulate matter emitted from the chimney;

[0018] Assuming that the environmental protection tax on mercury emissions is less than or equal to the environmental protection tax on particulate matter emissions, the calculation formula for the newly added hydrogen chloride concentration limit of the injected halogen is derived.

[0019] Optionally, the initial mercury content of the coal-fired flue gas is expressed as: in, represents the initial total mercury concentration in coal-fired flue gas, represents the initial elemental mercury concentration in coal-fired flue gas, represents the initial oxidized mercury concentration in coal-fired flue gas, It represents the initial particulate mercury concentration in coal-fired flue gas;

[0020] The corresponding relationship between the initial mercury content of the coal-fired flue gas and the mercury element content of the coal-fired flue gas is expressed as: Wherein, α represents the mercury migration coefficient, and m(Hg) represents the mercury content of the coal;

[0021] The corresponding relationship between the initial hydrogen chloride concentration of the coal-fired flue gas and the chlorine content of the coal-fired flue gas is expressed as: HCl =α1×m(Cl); where c HCl represents the initial hydrogen chloride concentration of the coal-fired flue gas, α1 represents the chlorine migration coefficient, and m(Cl) represents the chlorine content of the coal.

[0022] Optionally, the relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor is expressed as: in, represents the concentration of oxidized mercury at the outlet of the SCR reactor, and η represents the mercury oxidation conversion rate.

[0023] Optionally, the relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration is expressed as: Among them, β represents the first coefficient, represents the total concentration of hydrogen chloride at the inlet of the SCR reactor and Indicates the concentration of hydrogen chloride added by the halogen injection in the halogen injection demercuration test;

[0024] The relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor is expressed as: in, represents the mercury concentration at the outlet of the desulfurization device and is also the mercury concentration emitted from the chimney, λ represents the second coefficient, represents the elemental mercury concentration at the outlet of the SCR reactor.

[0025] Optionally, the relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor is expressed as: in, represents the concentration of particulate mercury at the outlet of the SCR reactor and

[0026]

[0027] Optionally, the relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor and the mercury content of the coal is expressed as:

[0028]

[0029] Optionally, the calculation formula of the mercury emission environmental tax is: Among them, P 税，汞 represents the environmental tax on mercury emissions, V RG represents the flue gas volume flow rate, σ 汞 represents the pollution emission equivalent coefficient of mercury, and D represents the unit price of environmental protection tax;

[0030] The calculation formula for the particulate matter emission environmental tax is: Among them, P 税，颗粒物 represents the environmental tax on particulate matter emissions, c 颗粒物,烟囱 represents the concentration of particulate matter emitted from the chimney, σ 颗粒物 Represents the pollution emission equivalent coefficient of particulate matter.

[0031] Optionally, the calculation formula for the newly added hydrogen chloride concentration limit of the injected halogen is expressed as:

[0032]

[0033] Another aspect of the present disclosure provides a coal-fired flue gas halogen injection mercury removal device, the device comprising:

[0034] An acquisition module, used for acquiring the mercury content and chlorine content of coal in the coal-fired unit;

[0035] A determination module, configured to determine the concentration limit of hydrogen chloride added by injection of halogen based on the mercury content of the coal and the chlorine content of the coal, using a predetermined calculation formula for the concentration limit of hydrogen chloride added by injection of halogen; wherein the calculation formula for the concentration limit of hydrogen chloride added by injection of halogen is determined based on the environmental protection tax cost of mercury;

[0036] The mercury removal module is used to remove mercury in the coal-fired flue gas discharged by the coal-fired unit by adopting the halogen injection mercury removal technology according to the newly added hydrogen chloride concentration limit of the halogen injection.

[0037] Compared with the prior art, the present invention can obtain the mercury content and the chlorine content of the coal in the coal-fired unit, and determine the concentration limit of the injected halogen-added hydrogen chloride by using the calculation formula of the concentration limit of the injected halogen-added hydrogen chloride determined based on the environmental protection tax cost of mercury. According to the concentration limit of the injected halogen-added hydrogen chloride, the concentration of the injected halogen-added hydrogen chloride in the process of halogen injection demercuration of coal-fired flue gas is controlled, so that the mercury in the coal-fired fuel gas can be removed without wasting halogen, and the balance between the environmental protection tax cost of mercury and the cost of demercuration of coal-fired flue gas is achieved, thereby reducing the total cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0039] Figure 1 A flow chart of a method for removing mercury by halogen injection from coal-fired flue gas provided in one embodiment of the present disclosure;

[0040] Figure 2 A schematic structural diagram of a coal-fired flue gas halogen injection mercury removal device provided in another embodiment of the present disclosure. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present disclosure clearer, the embodiments of the present disclosure will be described in detail below in conjunction with the accompanying drawings. However, it can be understood by those skilled in the art that in each embodiment of the present disclosure, many technical details are proposed in order to enable readers to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed for protection in the present disclosure can also be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present disclosure. The various embodiments can be combined and referenced with each other without contradiction.

[0042] One embodiment of the present disclosure relates to a method for removing mercury from coal-fired flue gas by halogen injection, the process of which is as follows: Figure 1 As shown, including:

[0043] Step S110, obtaining the mercury content and the chlorine content of the coal in the coal-fired unit.

[0044] Specifically, step S110 can utilize an online element analysis device installed on a coal conveying device of the coal-fired unit to analyze in real time the mercury content and chlorine content of the coal conveyed to the coal-fired unit, thereby obtaining the mercury content and chlorine content of the coal.

[0045] Step S120, based on the mercury content and chlorine content of the coal, the concentration limit of hydrogen chloride added by the injected halogen is determined by using a predetermined calculation formula for the concentration limit of hydrogen chloride added by the injected halogen, wherein the calculation formula for the concentration limit of hydrogen chloride added by the injected halogen is determined based on the environmental protection tax cost of mercury.

[0046] Specifically, the environmental tax cost of mercury is mainly determined based on the mercury content of coal-fired flue gas emitted into the atmosphere. The calculation formula for the limit of hydrogen chloride concentration added by halogen injection takes the mercury content and chlorine content of coal as independent variables, and the concentration of hydrogen chloride added by halogen injection in the halogen injection demercuration technology as the dependent variable. The goal is to balance the environmental tax cost of mercury with the cost of demercuration of coal-fired flue gas. When the mercury content and chlorine content of coal are known, the corresponding limit of hydrogen chloride concentration added by halogen injection can be obtained.

[0047] Step S130, according to the newly added hydrogen chloride concentration limit of the halogen injection, the halogen injection mercury removal technology is used to remove mercury in the coal-fired flue gas discharged by the coal-fired unit.

[0048] Specifically, when the halogen injection mercury removal technology is used to remove mercury from coal-fired flue gas, the actual concentration of hydrogen chloride added by the halogen injection is controlled according to the concentration limit of hydrogen chloride added by the halogen injection determined in step S120, so as to achieve a balance between the environmental tax cost of mercury and the cost of mercury removal from coal-fired flue gas.

[0049] Compared with the prior art, the method for demercuring coal-fired flue gas by halogen injection provided in the embodiment of the present disclosure can obtain the mercury content and the chlorine content of the coal in the coal-fired unit, and determine the concentration limit of the newly added hydrogen chloride for injected halogen by using the calculation formula for the concentration limit of the newly added hydrogen chloride for injected halogen determined based on the environmental protection tax cost of mercury. The concentration of the newly added hydrogen chloride for injected halogen in the process of demercuring coal-fired flue gas by halogen injection can be controlled according to the concentration limit of the newly added hydrogen chloride for injected halogen, so as to realize the removal of mercury in the coal-fired fuel gas without wasting halogen, and achieve a balance between the environmental protection tax cost of mercury and the cost of demercuring coal-fired flue gas, thereby reducing the total cost.

[0050] The process of determining the calculation formula for the newly added hydrogen chloride concentration limit for injected halogen is described in detail below.

[0051] Specifically, after the coal delivered to the coal-fired unit is burned in the furnace, only a small part of the mercury contained in it will be transferred to the ash, and most of the mercury in the coal will be transferred to the corresponding coal-fired flue gas, which will reach the SCR reactor through the tail flue. In the SCR reactor, the halogen elements will transfer part of the elemental mercury Hg 0 Converted into oxidized mercury Hg 2+ At this time, the mercury in the coal-fired flue gas is mainly elemental mercury Hg 0 , Oxidized mercury Hg 2+ and particulate mercury Hg p After that, the coal-fired flue gas flows through the dust collector, where most of the particulate mercury Hg p Captured into fly ash, achieving particulate mercury Hg p After that, the coal-fired flue gas flows through the desulfurization device, where most of the oxidized mercury Hg 2+ It is absorbed by the slurry in the desulfurization device, so that the remaining coal-fired flue gas mainly consists of elemental mercury Hg 0 The remaining coal-fired flue gas is discharged into the atmosphere through the chimney, which makes the elemental mercury Hg in the remaining coal-fired flue gas 0 It has become the basis for calculating and testing the environmental tax on mercury emissions.

[0052] The research results show that the mercury content of the coal-fired flue gas at the furnace outlet is basically proportional to the mercury content in the coal entering the furnace, that is, if the mercury concentration in the coal entering the furnace is obtained, the mercury concentration of the coal-fired flue gas at the furnace outlet can be obtained. In the process of removing mercury from the coal-fired flue gas, the coal-fired flue gas at the furnace outlet enters the SCR reactor, and an oxidation reaction will occur in the SCR reactor to remove mercury from the coal-fired flue gas. The oxidation efficiency of the oxidation reaction is basically proportional to the concentration of halogen elements in the SCR reactor, that is, the more halogens are injected into the SCR reactor, the higher the demercuration efficiency. When the coal-fired flue gas passes through the dust collector and the desulfurization device, most of the particulate mercury Hg p and oxidized mercury Hg2+ All of them are removed, so it can be approximately considered that the mercury concentration of chimney emissions is the same as the elemental mercury Hg at the outlet of the SCR reactor. 0 is directly proportional to the concentration.

[0053] Based on the above, when the coal-fired unit is operating normally, the calculation formula for the limit of the concentration of hydrogen chloride added by the injection of halogen is determined by using the preliminary test and the halogen injection demercuration test. Among them, the halogen injection demercuration test is carried out in the SCR reactor, and the coal-fired flue gas is successively demercured by the SCR reactor, dust collector, and desulfurization device before being discharged through the chimney.

[0054] The steps to determine the calculation formula for the additional hydrogen chloride concentration limit for halogen injection include:

[0055] A preliminary test is carried out during normal operation of the coal-fired unit. The mercury and chlorine content of the coal are tested, and the mercury and hydrogen chloride content of the coal-fired flue gas are tested at the inlet of the SCR reactor to obtain the corresponding relationship between the initial mercury content in the coal-fired flue gas and the mercury content in the coal, as well as the corresponding relationship between the initial hydrogen chloride concentration in the coal-fired flue gas and the chlorine content in the coal.

[0056] Specifically, since the mercury content of the coal-fired flue gas at the furnace outlet is basically proportional to the mercury content in the coal entering the furnace, and the coal-fired flue gas at the furnace outlet will enter the SCR reactor, the mercury content of the coal-fired flue gas at the inlet of the SCR reactor is basically the same as the mercury content of the coal-fired flue gas at the furnace outlet, and the mercury content of the coal-fired flue gas at the inlet of the SCR reactor is also basically proportional to the mercury content in the coal entering the furnace.

[0057] The initial mercury content of coal-fired flue gas can be expressed as: in, It indicates the initial total mercury concentration of the coal-fired flue gas and also the total mercury concentration at the inlet of the SCR reactor, in μg / m 3 . It indicates the initial elemental mercury concentration in coal-fired flue gas, in μg / m 3 . It indicates the initial oxidized mercury concentration in coal-fired flue gas, in μg / m 3 . It indicates the initial particulate mercury concentration in coal-fired flue gas, in μg / m 3 This is because the coal-fired flue gas at the inlet of the SCR reactor usually contains three forms of mercury, namely elemental mercury Hg 0 , Oxidized mercury Hg 2+ and particulate mercury Hg pTherefore, the sum of the concentrations of various existing forms of mercury is the total mercury concentration of the coal-fired flue gas at the inlet of the SCR reactor, and the total mercury concentration is also the initial total mercury concentration of the coal-fired flue gas in the halogen injection mercury removal test of the coal-fired flue gas.

[0058] After the coal entering the furnace is burned, most of the mercury it contains is in the form of elemental mercury Hg. 0 The mercury content of the initial mercury content in the coal-fired flue gas entering the SCR reactor can be expressed as follows: Where α is the mercury migration coefficient, in μg / m 3 . m(Hg) represents the mercury content in coal, with the unit of mg / g.

[0059] The initial hydrogen chloride concentration of coal-fired flue gas is also basically proportional to the chlorine content of the coal. The corresponding relationship between the initial hydrogen chloride concentration of coal-fired flue gas and the chlorine content of the coal is expressed as: HCl =α1×m(Cl). HCl It represents the initial hydrogen chloride concentration of coal flue gas, in μL / L. α1 represents the chlorine migration coefficient, dimensionless. m(Cl) represents the chlorine content of coal, in mg / g.

[0060] The mercury oxidation conversion rate of the SCR reactor to convert elemental mercury into oxidized mercury is defined, the mercury concentration is tested at the outlet of the SCR reactor, and the relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor is determined.

[0061] Exemplarily, the relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor is expressed as: in, It represents the concentration of oxidized mercury at the outlet of the SCR reactor, in μg / m 3 η represents the mercury oxidation conversion rate, the unit is %.

[0062] Specifically, the mercury concentration at the outlet of the SCR reactor includes three forms of mercury, namely, elemental mercury Hg 0 , Oxidized mercury Hg 2+ and particulate mercury Hg p The total mercury concentration at the outlet of the SCR reactor is It can be expressed as: in, Indicates the elemental mercury concentration at the outlet of the SCR reactor, in μg / m 3 . Indicates the concentration of particulate mercury at the outlet of the SCR reactor, in μg / m 3 .

[0063] During the halogen injection mercury removal test, the hydrogen chloride concentration test and the mercury oxidation conversion rate test are carried out at the inlet of the SCR reactor, and the mercury concentration test is carried out at the outlet of the desulfurization device to determine the relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration, and to determine the relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor.

[0064] Specifically, since the mercury oxidation conversion rate in the SCR reactor is mainly positively correlated with the hydrogen chloride concentration in the SCR reactor, in the halogen injection demercuration test, the halogen injection device can be used to continuously adjust the amount of halogen injected into the SCR reactor, that is, the halogen injection amount, and the hydrogen chloride concentration test and the mercury oxidation conversion rate test at the inlet of the SCR reactor and the mercury concentration test at the outlet of the desulfurization device are carried out under different halogen injection amounts, so as to respectively determine the relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration and the relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor.

[0065] Exemplarily, the relationship between mercury oxidation conversion rate and hydrogen chloride concentration is expressed as: Where β represents the first coefficient and is dimensionless. represents the total concentration of hydrogen chloride at the inlet of the SCR reactor, in μL / L, and It indicates the concentration of hydrogen chloride added by halogen injection in the halogen injection demercuration test, in μL / L.

[0066] The relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor is expressed as: in, It indicates the mercury concentration at the outlet of the desulfurization device and is also the mercury concentration of chimney emissions, in μg / m 3 λ represents the second coefficient and is dimensionless.

[0067] According to the relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor, the relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor and the mercury content of the coal is determined.

[0068] Since the mercury in the coal-fired flue gas of the SCR reactor undergoes only a transformation in form while the total amount remains unchanged, the total mercury concentration at the inlet of the SCR reactor is equal to the total mercury concentration at the outlet of the SCR reactor, so: That is, the relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor is expressed as: At the same time, since the SCR reactor only converts part of the elemental mercury Hg 0 Converted into oxidized mercury Hg 2+, Particle Hg p There is basically no morphological change in the SCR reactor, so Therefore, there are:

[0069]

[0070] because Therefore, based on the above deduction, we have:

[0071]

[0072] Right now: Therefore, the relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor, and the mercury content of the coal can be expressed as

[0073] Obviously, the concentration of mercury in chimney emissions is Only related to the mercury content m(Hg) of the coal and the total concentration of hydrogen chloride at the inlet of the SCR reactor Related.

[0074] Calculate the environmental protection tax on mercury emissions and the environmental protection tax on particulate matter emissions separately.

[0075] At present, coal-fired power plants usually need to pay environmental protection taxes on mercury or particulate matter in the flue gas emitted from the chimney. If the coal-fired flue gas is not demercured, the mercury content in the chimney emissions will be too high, and the mercury emission environmental protection tax will need to be paid. If the efficiency of demercuring coal-fired flue gas using halogen injection demercuration technology is too high, the mercury concentration in the chimney emissions will be reduced, making the particulate matter concentration in the chimney emissions higher than the mercury concentration in the chimney emissions, and the particulate matter emission environmental protection tax will need to be paid. However, it is also costly to use halogen injection demercuration technology to demercurate coal-fired flue gas. Therefore, in order to reduce the total cost, the most economical operation mode for coal-fired power plants is to control the amount of halogen injected, so that the mercury emission environmental protection tax is less than the particulate matter emission environmental protection tax.

[0076] For example, the calculation formula of the environmental tax on mercury emissions is: Among them, P 税，汞 Represents the environmental protection tax on mercury emissions, in yuan / h. V RG Indicates the flue gas volume flow rate, in m 3 / h, where the flue gas here refers to standard dry flue gas and meets 6% O2. 汞 It represents the pollution emission equivalent coefficient of mercury. D represents the unit price of environmental protection tax, which is usually a fixed value.

[0077] The calculation formula for the environmental tax on particulate matter emissions is: Among them, P 税，颗粒物Indicates the environmental protection tax on particulate matter emissions, in yuan / h. 颗粒物,烟囱 Indicates the concentration of particulate matter emitted from chimneys, in mg / m 3 σ 颗粒物 Represents the pollution emission equivalent coefficient of particulate matter.

[0078] Assuming that the environmental protection tax on mercury emissions is less than or equal to the environmental protection tax on particulate matter emissions, the calculation formula for the new hydrogen chloride concentration limit for halogen injection is derived.

[0079] Specifically, let P 税，汞 ≤P 税，颗粒物 , then:

[0080]

[0081] Therefore, the calculation formula for the newly added hydrogen chloride concentration limit of halogen injection can be expressed as:

[0082]

[0083] Among them, the concentration of particulate matter emitted from chimneys is usually relatively stable, so c 颗粒物,烟囱 The value of can be taken as the average emission value of coal-fired power plants in recent period and considered as a constant. α, α1, β, and λ can all be obtained through the above-mentioned preliminary test and halogen injection demercuration test. 汞 , σ 颗粒物 The variables in the above formula for calculating the limit of hydrogen chloride concentration added by halogen injection are mainly the mercury content m(Hg) in the coal, the chlorine content m(Cl) in the coal, and the hydrogen chloride concentration added by halogen injection. When the mercury content m(Hg) and chlorine content m(Cl) of the coal are known, we can get The relationship with a certain value is the limit of hydrogen chloride concentration added by halogen injection.

[0084] Another embodiment of the present disclosure relates to a coal-fired flue gas halogen injection mercury removal device, such as Figure 2 As shown, it includes an acquisition module 210 , a determination module 220 , and a mercury removal module 230 .

[0085] The acquisition module 210 is used to acquire the mercury content and the chlorine content of the coal in the coal-fired unit.

[0086] The determination module 220 is used to determine the concentration limit of hydrogen chloride added by injection of halogen based on the mercury content and the chlorine content of the coal using a predetermined calculation formula for the concentration limit of hydrogen chloride added by injection of halogen. The calculation formula for the concentration limit of hydrogen chloride added by injection of halogen is determined based on the environmental protection tax cost of mercury.

[0087] The mercury removal module 230 is used to remove mercury from the coal-fired flue gas discharged from the coal-fired unit by adopting the halogen injection mercury removal technology according to the newly added hydrogen chloride concentration limit of the halogen injection.

[0088] The specific implementation method of the halogen injection mercury removal device for coal-fired flue gas provided in the embodiment of the present disclosure can be referred to the halogen injection mercury removal method for coal-fired flue gas provided in the embodiment of the present disclosure, which will not be repeated here.

[0089] Compared with the prior art, the halogen injection mercury removal device for coal-fired flue gas provided in the embodiment of the present disclosure can obtain the mercury content and the chlorine content of the coal in the coal-fired unit, and determine the concentration limit of the newly added hydrogen chloride injected by the halogen using the calculation formula for the concentration limit of the newly added hydrogen chloride injected by the halogen based on the environmental protection tax cost of mercury. The concentration of the newly added hydrogen chloride injected by the halogen in the process of halogen injection mercury removal by the halogen is controlled according to the concentration limit of the newly added hydrogen chloride injected by the halogen, thereby achieving the removal of mercury in the coal-fired fuel gas without wasting halogen, achieving a balance between the environmental protection tax cost of mercury and the cost of mercury removal from the coal-fired flue gas, thereby reducing the total cost.

[0090] Those skilled in the art will appreciate that the above-mentioned embodiments are specific embodiments for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present disclosure.

Claims

1. A method for removing mercury from coal-fired flue gas by halogen injection, characterized in that: The method comprises: Obtain the mercury content and chlorine content of coal in coal-fired units; Based on the mercury content of the coal and the chlorine content of the coal, the limit value of the concentration of hydrogen chloride added by the injection of halogen is determined by using a predetermined calculation formula for the limit value of the concentration of hydrogen chloride added by the injection of halogen; wherein the calculation formula for the limit value of the concentration of hydrogen chloride added by the injection of halogen is determined based on the environmental protection tax cost of mercury; According to the newly added hydrogen chloride concentration limit of the halogen injection, the halogen injection mercury removal technology is used to remove mercury in the coal-fired flue gas discharged from the coal-fired unit.

2. The method according to claim 1, characterized in that The process of determining the calculation formula of the additional hydrogen chloride concentration limit of the halogen injection includes a halogen injection demercuration test, which is carried out in an SCR reactor, and the coal-fired flue gas is sequentially demercured by the SCR reactor, the dust collector, and the desulfurization device before being discharged through a chimney; The step of determining the calculation formula for the limit value of the concentration of hydrogen chloride added by the injected halogen comprises: When the coal-fired unit is operating normally, the coal is tested for mercury content and chlorine content, and the coal-fired flue gas is tested for mercury content and hydrogen chloride content at the inlet of the SCR reactor to obtain the corresponding relationship between the initial mercury content of the coal-fired flue gas and the mercury content of the coal, and the corresponding relationship between the initial hydrogen chloride concentration of the coal-fired flue gas and the chlorine content of the coal; Defining a mercury oxidation conversion rate of the SCR reactor to convert elemental mercury into oxidized mercury, performing a mercury concentration test at the outlet of the SCR reactor, and determining a relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor; During the halogen injection mercury removal test, a hydrogen chloride concentration test and a mercury oxidation conversion rate test are performed at the inlet of the SCR reactor, and a mercury concentration test is performed at the outlet of the desulfurization device to determine a relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration, and to determine a relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor; According to the relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor, determining a relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor, and the mercury content of the coal; Calculate the environmental tax on mercury emissions based on the mercury concentration at the outlet of the desulfurization device, and calculate the environmental tax on particulate matter emissions based on the concentration of particulate matter emitted from the chimney; Assuming that the environmental protection tax on mercury emissions is less than or equal to the environmental protection tax on particulate matter emissions, the calculation formula for the newly added hydrogen chloride concentration limit of the injected halogen is derived.

3. The method according to claim 2, characterized in that The initial mercury content of the coal-fired flue gas is expressed as: in, represents the initial total mercury concentration in coal-fired flue gas, represents the initial elemental mercury concentration in coal-fired flue gas, represents the initial oxidized mercury concentration in coal-fired flue gas, It represents the initial particulate mercury concentration in coal-fired flue gas; The corresponding relationship between the initial mercury content of the coal-fired flue gas and the mercury element content of the coal-fired flue gas is expressed as: Wherein, α represents the mercury migration coefficient, and m(Hg) represents the mercury content of the coal; The corresponding relationship between the initial hydrogen chloride concentration of the coal-fired flue gas and the chlorine content of the coal-fired flue gas is expressed as: HCl =α1×m(Cl); where c HCl represents the initial hydrogen chloride concentration of the coal-fired flue gas, α1 represents the chlorine migration coefficient, and m(Cl) represents the chlorine content of the coal.

4. The method according to claim 3, characterized in that The relationship between the mercury oxidation conversion rate and the mercury concentration at the outlet of the SCR reactor is expressed as: in, represents the concentration of oxidized mercury at the outlet of the SCR reactor, and η represents the mercury oxidation conversion rate.

5. The method according to claim 4, characterized in that The relationship between the mercury oxidation conversion rate and the hydrogen chloride concentration is expressed as: Among them, β represents the first coefficient, represents the total concentration of hydrogen chloride at the inlet of the SCR reactor and Indicates the concentration of hydrogen chloride added by the halogen injection in the halogen injection demercuration test; The relationship between the mercury concentration at the outlet of the desulfurization device and the elemental mercury concentration at the outlet of the SCR reactor is expressed as: in, Chimney represents the mercury concentration at the outlet of the desulfurization device and is also the mercury concentration emitted from the chimney, λ represents the second coefficient, represents the elemental mercury concentration at the outlet of the SCR reactor.

6. The method according to claim 5, characterized in that The relationship between the mercury content at the inlet of the SCR reactor and the mercury content at the outlet of the SCR reactor is expressed as: in, represents the concentration of particulate mercury at the outlet of the SCR reactor and 7. The method according to claim 6, characterized in that The relationship between the mercury concentration at the outlet of the desulfurization device, the hydrogen chloride concentration at the inlet of the SCR reactor and the mercury content of the coal is expressed as follows:

8. The method according to claim 7, characterized in that The calculation formula for the mercury emission environmental tax is: Among them, P 税，汞 represents the environmental tax on mercury emissions, V RG represents the flue gas volume flow rate, σ 汞 represents the pollution emission equivalent coefficient of mercury, and D represents the unit price of environmental protection tax; The calculation formula for the particulate matter emission environmental tax is: Among them, P 税，颗粒物 represents the environmental tax on particulate matter emissions, c 颗粒物,烟囱 represents the concentration of particulate matter emitted from the chimney, σ 颗粒物 Represents the pollution emission equivalent coefficient of particulate matter.

9. The method according to claim 8, characterized in that The calculation formula for the newly added hydrogen chloride concentration limit of the injected halogen is expressed as:

10. A halogen injection mercury removal device for coal-fired flue gas, characterized in that: The device comprises: An acquisition module, used for acquiring the mercury content and chlorine content of coal in the coal-fired unit; A determination module, configured to determine the concentration limit of hydrogen chloride added by injection of halogen based on the mercury content of the coal and the chlorine content of the coal, using a predetermined calculation formula for the concentration limit of hydrogen chloride added by injection of halogen; wherein the calculation formula for the concentration limit of hydrogen chloride added by injection of halogen is determined based on the environmental protection tax cost of mercury; The mercury removal module is used to remove mercury in the coal-fired flue gas discharged by the coal-fired unit by adopting the halogen injection mercury removal technology according to the newly added hydrogen chloride concentration limit of the halogen injection.

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