Flue gas treatment method for improving mercury removal efficiency of coal-fired power plant

Abstract

The invention discloses a flue gas treatment method for improving the mercury removal efficiency of a coal-fired power plant, and solves the problems that the cost of an adsorbent is high, the adsorption effect is limited, solid waste treatment is difficult, secondary pollution and equipment corrosion risks exist, multi-pollutant treatment lacks and is poor in synergism, so that resource waste is caused, medicament use cannot be dynamically optimized, and waste of resources is caused. The mercury removal efficiency and the resource utilization economy are influenced.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental treatment, and in particular relates to a flue gas treatment method for improving mercury removal efficiency in a coal-fired power plant. Background Art

[0002] As the global industrialization process continues to advance, energy demand has increased dramatically, and coal-fired power generation has played an important role in the power supply system. However, coal-fired power plants emit a large amount of pollutants into the atmosphere during operation, among which mercury pollution has received increasing attention.

[0003] Mercury is a heavy metal pollutant with high toxicity, persistence and bioaccumulation. In the flue gas of coal-fired power plants, mercury exists mainly in three forms: gaseous elemental mercury (Hg 0 ), gaseous divalent mercury (Hg 2+ ) and particulate mercury (Hg p ). Hg 0 It has high volatility and chemical stability, stays in the atmosphere for a long time, can be transmitted over long distances, and can circulate around the globe, posing a potential threat to the ecological environment and human health. 2+ It is easily soluble in water and can be partially removed by processes such as wet flue gas desulfurization (FGD), but its proportion in the total mercury is relatively low. p It can be captured to a certain extent in particulate matter control equipment such as electrostatic precipitators (ESP) or bag filters.

[0004] In traditional flue gas treatment of coal-fired power plants, the complexity of mercury forms makes it difficult to remove mercury efficiently with a single demercuration technology, especially the difficulty in removing gaseous elemental mercury. In addition, traditional adsorbents are costly, have limited adsorption effects, are difficult to treat solid waste, and have risks of secondary pollution and equipment corrosion. The lack of synergy in multi-pollutant treatment results in a waste of resources and makes it impossible to dynamically optimize the use of reagents, affecting the efficiency of mercury removal and the economic efficiency of resource utilization. Therefore, a flue gas treatment method with high mercury removal efficiency is urgently needed. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a flue gas treatment system with improved mercury removal efficiency in a coal-fired power plant.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a flue gas treatment system with improved mercury removal efficiency in a coal-fired power plant, characterized in that: the flue gas treatment system comprises a flue gas conditioning module, a catalytic oxidation unit, a coarse adsorption unit, a fine adsorption unit, a mercury recovery unit, and a measurement and control unit;

[0009] The flue gas regulation module includes an intelligent control system and an oxidant injection device;

[0010] The catalytic oxidation unit includes a staged oxidation module and a photochemical oxidation module;

[0011] The crude adsorption unit uses primary adsorption material and arranges the adsorbent in a loose packing manner;

[0012] The fine adsorption unit adopts a high-efficiency adsorbent;

[0013] The mercury recovery unit includes a pyrolysis process device and a chemical elution device;

[0014] The measurement and control unit includes a real-time detection component, an online monitoring device and a feedback mechanism.

[0015] As a preferred embodiment of the flue gas treatment system of the present invention, the oxidant injection device comprises potassium iodide, potassium iodate and potassium periodate or bromide and chloride.

[0016] As a preferred solution of the flue gas treatment system of the present invention, the primary adsorption material includes modified coal fly ash and industrial by-products.

[0017] As a preferred solution of the flue gas treatment system of the present invention, the flue gas adjustment module, catalytic oxidation unit, coarse adsorption unit, fine adsorption unit, mercury recovery unit, and measurement and control unit are connected through pipelines.

[0018] As a preferred solution of the flue gas treatment system of the present invention, the high-efficiency adsorbent includes but is not limited to at least one of brominated activated carbon and sulfided activated carbon.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a flue gas treatment method for a coal-fired power plant with improved mercury removal efficiency, which is characterized by comprising:

[0020] The flue gas discharged from the boiler is introduced into the flue gas conditioning module, the preliminary treatment environment is adjusted, and the oxidant is injected;

[0021] The flue gas enters the staged oxidation module, passes through the selective catalytic reduction device and the SCR catalyst, and then enters the photochemical oxidation module;

[0022] Use coarse and fine adsorbent materials to treat flue gas;

[0023] Regeneration of adsorbent materials and recovery of mercury;

[0024] Detection, control and feedback.

[0025] As a preferred embodiment of the flue gas treatment method of the present invention, the preliminary treatment environment is adjusted, wherein the temperature of the preliminary treatment environment is 50-80°C, the humidity is 10%-15%, and the flow rate is 8-12m / s.

[0026] As a preferred embodiment of the flue gas treatment method of the present invention, the process is carried out through a selective catalytic reduction device, wherein the catalyst in the selective catalytic reduction device comprises at least one of a manganese-based, vanadium-based or titanium-based composite catalyst.

[0027] As a preferred solution of the flue gas treatment method of the present invention, the photochemical oxidation module is a UV light or electron beam irradiation technology.

[0028] As a preferred solution of the flue gas treatment method of the present invention, the detection is real-time monitoring of the mercury concentration in the flue gas emissions.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention achieves efficient oxidation of mercury by constructing a hierarchical oxidation and adsorption synergistic treatment technology system, combining SCR catalytic oxidation and photochemical oxidation. The hierarchical adsorption unit significantly reduces the load of the high-efficiency adsorbent. At the same time, the thermal decomposition and chemical elution cycle regeneration of the adsorbent can reduce resource waste. Combined with online monitoring and intelligent closed-loop control, the use of oxidants and adsorbents is dynamically optimized, achieving ultra-efficient removal of mercury in flue gas from coal-fired power plants, synergistic treatment of multiple pollutants, and economical and environmentally friendly resource utilization.

[0031] (2) The recycling and reduction of waste volume of the adsorbent of the present invention significantly reduce the demand for solid waste treatment and alleviate the long-term impact on the environment. At the same time, the graded oxidation treatment can reduce the filtration pressure of the fine adsorption unit during use, thereby reducing the replacement frequency of the fine adsorption unit. The coarse adsorption unit uses low-cost primary adsorption materials, thereby having the effect of reducing filtration costs during use.

[0032] (3) Through the synergistic effect of graded oxidation and adsorption technology, as well as intelligent dynamic regulation, the mercury removal system of the present invention can stably maintain the mercury removal efficiency at the standard of meeting emission standards for a long time. This efficient and stable mercury removal performance not only meets the ultra-low emission standards, but also has the function of adjusting various parameters of the equipment in real time through detection equipment, which not only greatly reduces operating costs and resource consumption, but also has the effect of intelligent dynamic regulation according to different flue gas concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0034] Figure 1 This is a flow chart of the flue gas treatment method provided by the present invention. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0038] The industrial by-product used in the embodiment of the present invention is a product obtained by pyrolysis treatment after the smoke is treated by a fine adsorption unit and reaches the upper adsorption line.

[0039] The modification method of the modified coal fly ash used in the embodiment of the present invention is to grind the coal fly ash mechanically and then spray bromine on the surface.

[0040] Example 1

[0041] This embodiment provides a flue gas treatment system with improved mercury removal efficiency in a coal-fired power plant, including a flue gas conditioning module, a catalytic oxidation unit, a coarse adsorption unit, a fine adsorption unit, a mercury recovery unit, and a measurement and control unit;

[0042] The flue gas regulation module includes an intelligent control system and an oxidant injection device;

[0043] Among them, the intelligent control system can regulate the conditions of the treatment environment, including temperature, humidity and flow rate, and the oxidant injection device can inject potassium iodide, potassium iodate and potassium periodate or bromide and chloride;

[0044] The catalytic oxidation unit includes a staged oxidation module and a photochemical oxidation module;

[0045] The staged oxidation module includes a selective catalytic reduction device and a catalyst injection device, and the photochemical oxidation module uses UV light or electron beam irradiation technology; the catalyst is an SCR catalyst;

[0046] The crude adsorption unit uses primary adsorption materials, including modified coal fly ash and industrial byproducts, and arranges the adsorbent in a loose packing manner;

[0047] The fine adsorption unit uses brominated activated carbon or sulfided activated carbon as a high-efficiency adsorbent;

[0048] The mercury recovery unit uses a pyrolysis process to recover liquid mercury, uses a chemical elution technique to remove residues on the adsorbent surface, and returns the regenerated adsorbent to the crude adsorption unit for continued use or as an industrial raw material for recycling;

[0049] The measurement and control unit includes real-time detection components, online monitoring equipment and feedback mechanism;

[0050] Among them, the real-time monitoring component detects various information of the flue gas, and the online monitoring equipment monitors the mercury concentration in the flue gas emissions in real time. If the emission concentration exceeds the standard, the feedback mechanism will be triggered. The parameters of the treatment equipment are adjusted through the feedback mechanism to optimize the flue gas treatment process to ensure that the emission meets the standard. Specifically, when the emission concentration exceeds the standard, the parameters in the system are adjusted to meet the emission standards. Among them, increasing the amount of oxidant injection can improve the mercury oxidation efficiency and reduce the mercury in the flue gas to achieve standard emissions.

[0051] Example 2

[0052] This embodiment provides a flue gas treatment method for improving mercury removal efficiency in a coal-fired power plant, comprising the following steps:

[0053] (1) Pretreatment: First, perform preliminary treatment, introduce the flue gas discharged from the boiler into the flue gas conditioning module, and adjust the preliminary treatment environment (temperature 50-80°C, humidity 10%-15%, flow rate 8-12m / s) through the intelligent control system.

[0054] This temperature range can create ideal reaction conditions for the oxidation of mercury and effectively reduce other components in the flue gas, including SO2, NO x The interference of temperature and humidity ensures that the reaction rate between the oxidant and mercury is maximized. Within this range, the oxidation efficiency is significantly improved, while avoiding excessively high temperatures that cause the oxidant to decompose or excessively low temperatures that inhibit the reaction activity;

[0055] Flue gas humidity can promote the dissolution and distribution of oxidants, increase the contact area between mercury and oxidants, and thus improve the reaction efficiency. In addition, appropriate humidity helps to capture divalent mercury in flue gas and facilitate the subsequent adsorption process. Humidity regulation optimizes the kinetic conditions of the oxidation reaction, increases the oxidation reaction rate, and avoids the risk of equipment corrosion caused by excessive humidity or oxidant reaction failure under low humidity conditions.

[0056] In the pretreatment stage, oxidants (potassium iodide, potassium iodate and potassium periodate or bromide, chloride) need to be sprayed. Iodine-based oxidants have strong stability and adaptability and can maintain efficient oxidation performance under various flue gas conditions. Bromine-based and chlorine-based oxidants are suitable for use under medium temperature and high humidity conditions and can effectively capture Hg in flue gas. 0 At the same time, the mercury concentration in the flue gas is detected, and the input amount is controlled according to the mercury concentration. When the mercury concentration is high, the input amount is gradually increased;

[0057] (2) Catalytic oxidation unit: After the pre-treated flue gas enters the staged oxidation module, it first passes through the optimized selective catalytic reduction device, and then the mercury is oxidized by the commercial SCR catalyst. After the oxidized mercury, the flue gas enters the photochemical oxidation module (UV light or electron beam irradiation technology), where the catalyst can 0 Converted to Hg 2+ , photochemical oxidation is used to convert unoxidized Hg 0 Converted to Hg 2+ and Hg P , the oxidation rate of mercury can be improved through this two-stage graded oxidation mechanism.

[0058] The optimized selective catalytic reduction device specifically uses manganese-based, vanadium-based or titanium-based composite catalysts to enhance the versatility of the catalyst. Manganese-based catalysts provide good oxidation ability, vanadium-based catalysts have efficient denitrification performance, and titanium-based catalysts improve the durability and anti-poisoning ability of the catalyst. By compositely optimizing the composite catalyst, the synergistic effect of denitrification and mercury oxidation is achieved in the same catalyst, thereby improving the overall treatment efficiency.

[0059] Effect of UV light: Through the irradiation of high-energy UV light, strong oxidizing active species such as O3 and OH free radicals are generated. These active species can quickly react with Hg in the flue gas. 0 Reaction, oxidizing it to divalent mercury Hg 2+ or particulate mercury Hg P UV light technology has the characteristics of rapid response and can replenish Hg that is not completely oxidized during the SCR oxidation process. 0 , effectively improving the overall oxidation efficiency.

[0060] The role of electron beam irradiation: Electron beam technology bombards flue gas with high-energy electrons to generate a large number of active chemical groups such as O2- , HO2, these groups and Hg 0 A chemical reaction occurs to complete the oxidation process of mercury. Electron beam technology can operate efficiently at a low temperature <300°C, which is particularly suitable for terminal flue gas treatment and significantly improves the oxidation efficiency under low temperature conditions. Photochemical oxidation technology has strong adaptability and can be flexibly adjusted according to changes in flue gas composition. It is a powerful supplement to the efficient flue gas mercury removal process.

[0061] (3) The crude adsorption unit first uses primary adsorption materials to capture Hg in the flue gas 2+ and Hg P For coal-fired power plants, modified fly ash from power plants can be used. Its adsorption efficiency for mercury is limited, which can achieve resource recycling and reduce environmental impact. The adsorbent in this stage is arranged in a loose packing manner to reduce airflow resistance and increase the contact area between the adsorbent and the flue gas;

[0062] The crude adsorption unit significantly reduces the mercury load in the flue gas and reduces the processing pressure of the subsequent fine adsorption unit. In addition, the crude adsorption unit can also reduce the fine adsorption load. The crude adsorption unit removes most of the simple forms of mercury compounds, freeing up more adsorption capacity for high-cost fine adsorption materials to focus on the deep capture of residual mercury.

[0063] (4) Fine adsorption unit: After the crude adsorption, the residual mercury is introduced into the fine adsorption unit and treated in depth using high-efficiency adsorbents. High-efficiency adsorbents include brominated activated carbon and sulfided activated carbon, which are used for deep treatment with large specific surface area and chemical mercury capture performance, so that the flue gas emission mercury concentration reaches the ultra-low emission standard;

[0064] (5) Mercury recovery unit: The adsorbent is first volatilized and recovered by catalytic pyrolysis or urea pyrolysis, allowing the mercury to be collected in the form of liquid metal for industrial use. Subsequently, the residual mercury on the surface of the adsorbent is removed by chemical elution technology using dilute acid (the hydrogen ions in the acid react with the mercury compounds on the adsorbent to dissolve it and detach it from the adsorbent surface). After the residual mercury is removed, the blocked pores of the adsorbent are unblocked, and its specific surface area and chemical activity are restored, that is, the adsorption performance is restored. The regenerated adsorbent is then returned to the crude adsorption unit for continued use or as an industrial raw material for recycling;

[0065] (6) Measurement and control unit: By detecting various information of flue gas through real-time monitoring components and monitoring the mercury concentration in flue gas emissions in real time through online monitoring equipment, the mercury concentration in flue gas emissions, initial concentration and key parameters in the reaction process (oxidant dosage, adsorbent dosage, reaction conditions, etc.) can be obtained. If the emission concentration is found to exceed the standard, the system automatically triggers the feedback mechanism, and adjusts the parameters of the treatment equipment through the feedback mechanism to optimize the flue gas treatment process to ensure that emissions meet the standards;

[0066] Among them, the real-time monitoring components are sensor detection equipment, and the online monitoring equipment includes cold atomic absorption spectrometer mercury analyzer, cold atomic fluorescence spectrometer mercury analyzer and differential absorption spectrometer; the feedback mechanism is that when the emission concentration exceeds the standard, in order to meet the emission requirements, the parameters in the system are adjusted to meet the emission standards. For example, increasing the amount of oxidant injection can improve the mercury oxidation efficiency and reduce the mercury in the flue gas to achieve standard emissions.

[0067] Example 3

[0068] This embodiment uses the method of embodiment 2 to treat flue gas, including the following steps:

[0069] (1) Pretreatment: The flue gas discharged from the boiler is introduced into the flue gas conditioning module, the preliminary treatment environment is adjusted (temperature 50-80°C, humidity 10%-15%, flow rate 8-12m / s), and the oxidant ammonium bromide is injected. At this time, the mercury concentration in the flue gas is detected to be 25.75μg / m 3 , control the input amount to 5kg / h;

[0070] (2) Catalytic oxidation: The flue gas enters the graded oxidation module, passes through a selective catalytic reduction device containing MnO2, V2O5, and TiO2 in a mass ratio of 4:6:90, and then oxidizes the mercury through a commercial SCR catalyst. The oxidized flue gas enters the photochemical oxidation module. The photochemical oxidation module of this embodiment uses UV light (UV light wavelength 185nm and / or 254nm, power 100-500W, time 2-5s) or electron beam irradiation technology, wherein when the electron irradiation technology is used, the electron beam energy is 0.3-1.5MeV, the irradiation dose is a lower dose (1-5kGy) suitable for low-concentration mercury flue gas, and a higher dose (10-20kGy) is used for high-concentration mercury flue gas or higher oxidation efficiency requirements, the residence time is 0.1-2 seconds, which is adjusted according to the irradiation dose and flue gas concentration; the flow rate needs to be uniform to ensure that the electron beam is in full contact with the flue gas.

[0071] (3) Rough adsorption: using modified coal fly ash distributed in a honeycomb array to capture Hg in flue gas 2+ and Hg P ;

[0072] (4) Fine adsorption: Use brominated activated carbon and sulfided activated carbon to deeply treat flue gas;

[0073] (5) Mercury recovery: First, put the used brominated / sulfided activated carbon into the pyrolysis equipment to remove loose particles and dust to avoid affecting the pyrolysis efficiency. Control the temperature to 450-600°C (400-600°C for brominated activated carbon and 450-650°C for sulfided activated carbon), introduce inert gas, maintain the pyrolysis time for 30-120 minutes, and introduce catalyst at the same time. Gases such as Br2, SO2 or H2S generated during the pyrolysis process need to be removed by secondary adsorption or tail gas treatment equipment; pyrolysis products such as HgBr2 or HgS can be recovered by condensation or stabilized by capture devices. Finally, the adsorbent is cooled to room temperature after pyrolysis, and the retained amount of bromine or sulfide is checked. If the activity is good, it can be directly recycled.

[0074] (6) Measurement and control: Real-time monitoring of mercury concentration in flue gas emissions. The mercury concentration in the treated flue gas is 0.80 μg / m 3 .

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 3 is that (ammonium bromide) in step (1) is replaced by (ammonium chloride, 5 kg / h), and the remaining steps are the same as those in Example 3. The mercury concentration of the flue gas after treatment is 3.43 μg / m 3 .

[0077] The present invention realizes low-cost and ultra-efficient removal of mercury in flue gas from coal-fired power plants by constructing a hierarchical oxidation and adsorption synergistic treatment technology system. It can also realize the recycling of adsorbents and reduce the amount of solid waste treatment. Through measurement and control, long-term stable and low mercury emissions can be achieved.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A flue gas treatment system for improving mercury removal efficiency in a coal-fired power plant, characterized in that: The flue gas treatment system includes a flue gas conditioning module, a catalytic oxidation unit, a rough adsorption unit, a fine adsorption unit, a mercury recovery unit, and a measurement and control unit; The flue gas regulation module includes an intelligent control system and an oxidant injection device; The catalytic oxidation unit includes a staged oxidation module and a photochemical oxidation module; The crude adsorption unit uses primary adsorption material and arranges the adsorbent in a loose packing manner; The fine adsorption unit adopts a high-efficiency adsorbent; The mercury recovery unit includes a pyrolysis process device and a chemical elution device; The measurement and control unit includes a real-time detection component, an online monitoring device and a feedback mechanism.

2. The flue gas treatment system according to claim 1, characterized in that: The oxidant injection device, wherein the oxidant includes potassium iodide, potassium iodate and potassium periodate or bromide and chloride.

3. The flue gas treatment system according to claim 1, characterized in that: The primary adsorption material includes modified coal fly ash and industrial by-products.

4. The flue gas treatment system according to claim 1, characterized in that: The flue gas adjustment module, the catalytic oxidation unit, the rough adsorption unit, the fine adsorption unit, the mercury recovery unit, and the measurement and control unit are connected through pipelines.

5. The flue gas treatment system according to claim 1, characterized in that: The high-efficiency adsorbent includes but is not limited to at least one of brominated activated carbon and sulfided activated carbon.

6. A flue gas treatment method for improving mercury removal efficiency in a coal-fired power plant, characterized in that: include, The flue gas discharged from the boiler is introduced into the flue gas conditioning module, the preliminary treatment environment is adjusted, and the oxidant is injected; The flue gas enters the staged oxidation module, passes through the selective catalytic reduction device and the SCR catalyst, and then enters the photochemical oxidation module; Use coarse and fine adsorbent materials to treat flue gas; Regeneration of adsorbent materials and recovery of mercury; Detection, control and feedback.

7. The flue gas treatment method according to claim 6, characterized in that: The preliminary treatment environment is adjusted, wherein the temperature of the preliminary treatment environment is 50-80° C., the humidity is 10%-15%, and the flow rate is 8-12 m / s.

8. The flue gas treatment method according to claim 6, characterized in that: The selective catalytic reduction device is used, wherein the catalyst in the selective catalytic reduction device includes at least one of a manganese-based, vanadium-based or titanium-based composite catalyst.

9. The flue gas treatment method according to claim 6, characterized in that: The photochemical oxidation module is a UV light or electron beam irradiation technology.

10. The flue gas treatment method according to claim 6, characterized in that: The detection is to monitor the mercury concentration in the flue gas emissions in real time.

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