HF tail gas treatment device and method coupled with desulfurization system of thermal power generating unit

Abstract

The invention discloses an HF tail gas treatment device coupled with a desulfurization system of a thermal power generating unit and a method. The HF tail gas treatment device comprises a pretreatment system, a waste gas collection device, an acid-resistant pipeline, a Venturi tube, a boiler smoke outlet and a wet desulfurization tower, an outlet of the pretreatment system is communicated with an inlet of the Venturi tube, a smoke outlet of the boiler is communicated with the inlet of the Venturi tube, an outlet of the Venturi tube is communicated with a gas inlet of the wet desulfurization tower, and the device and the method can efficiently remove HF tail gas and are low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and industrial waste gas treatment, and relates to an HF tail gas treatment device and method coupled with a desulfurization system of a thermal power unit. Background Art

[0002] With the rapid development of the new energy industry and the electric vehicle market, the recycling and utilization of waste energy storage lithium-ion batteries has received increasing attention. When pre-treating waste lithium batteries, tail gas containing harmful gases such as hydrogen fluoride (HF) is often produced. HF is a highly toxic and corrosive acidic gas. If it is directly discharged without effective treatment, it will not only seriously corrode equipment and pipelines, but also cause serious harm to the atmospheric environment and human health. Therefore, reliable purification measures need to be taken to remove it. Current environmental protection regulations are increasingly stringent on the emission limits of fluorine-containing waste gases, and usually require that the HF concentration in the treated tail gas be less than 1 mg / m 3 , which places high efficiency requirements on processing technology.

[0003] Existing HF tail gas treatment technologies are mainly divided into two categories: wet and dry. The wet process has a high HF removal rate, but it often requires the construction of a special absorption tower and a supporting spray system, which requires large equipment investment and high operating costs, and will produce secondary pollutants such as fluorine-containing wastewater. The dry technology avoids wastewater treatment, has low operating costs, and the solid by-product CaF2 generated by the reaction is easy to recycle. However, the dry process usually requires preheating of the tail gas to prevent condensation, which increases energy consumption; at the same time, special reactors and dust removal equipment still need to be added, which inevitably requires land and investment, and has high requirements for operation and control. Overall, whether it is a wet or dry method, the existing scheme requires the addition of a set of independent HF treatment equipment, which brings a greater economic burden and engineering complexity to the waste gas treatment. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a HF tail gas treatment device and method coupled with a desulfurization system of a thermal power unit, which can efficiently remove HF tail gas at a low cost.

[0005] To achieve the above-mentioned purpose, the present invention discloses an HF tail gas treatment device coupled with a desulfurization system of a thermal power unit, comprising a pretreatment system, an exhaust gas collection device, an acid-resistant pipeline, a venturi tube, a boiler smoke outlet and a wet desulfurization tower; the outlet of the pretreatment system is connected to the inlet of the venturi tube, the boiler smoke outlet is connected to the inlet of the venturi tube, and the outlet of the venturi tube is connected to the gas inlet of the wet desulfurization tower.

[0006] The further improvement of the HF tail gas treatment device coupled with the desulfurization system of the thermal power unit according to the present invention is:

[0007] Furthermore, the gas outlet of the wet desulfurization tower is connected to the inlet of the chimney through a wet dust collector.

[0008] Furthermore, the wet desulfurization tower includes a tower body, in which a demister, a spray assembly and a slurry pool are sequentially arranged from top to bottom.

[0009] Furthermore, the gas inlet of the wet desulfurization tower is arranged on the side of the tower body and is located between the slurry pool and the spray assembly.

[0010] Furthermore, it also includes a feeding system, and the outlet of the feeding system is connected to the slurry pool.

[0011] Furthermore, the outlet of the slurry pool is connected to the inlet of the spray assembly via a circulation pump.

[0012] Furthermore, the gas outlet at the top of the tower body is connected to the inlet of the monitoring system, the output end of the monitoring system is connected to the input end of the control unit, and the output end of the control unit is connected to the control end of the circulation pump and the control end of the feeding system.

[0013] Furthermore, the outlet of the pretreatment system is connected to the inlet of the venturi tube via the waste gas collection device and the acid-resistant pipe.

[0014] Furthermore, the pretreatment system includes a box body and a feeding and crushing system, a heating and drying system, and a screening and sorting system arranged in the box body.

[0015] The present invention discloses a method for treating HF tail gas coupled with a desulfurization system of a thermal power unit, comprising the following steps:

[0016] The HF tail gas output by the pretreatment system is evenly mixed with the boiler flue gas. The mixed flue gas enters the wet desulfurization tower from bottom to top. In the wet desulfurization tower, the slurry contacts the HF-containing flue gas in reverse, dissolving the HF in the alkaline slurry droplets and undergoing a neutralization reaction. The HF is converted into a stable salt compound and remains in the liquid phase.

[0017] The present invention has the following beneficial effects:

[0018] The HF tail gas treatment device and method coupled to the desulfurization system of a thermal power unit, as described in the present invention, directly utilizes existing desulfurization absorption towers, spray slurry circulation systems, and other equipment in thermal power plants to treat HF ​​tail gas. No large-scale scrubbers or dust collectors are required, significantly reducing equipment investment and floor space. This also reduces system complexity, facilitating project implementation and maintenance. The HF removal efficiency can reach over 99%, and the HF concentration in the tail gas after purification is consistently below 1 mg / m3. 3, surpassing stringent environmental emission standards. Compared to the approximately 95% to 98% removal rate achieved by conventional dry-process powder spraying devices, the present invention maintains a higher purification rate even under high-concentration HF conditions, ensuring environmental safety. Furthermore, the present invention does not require additional exhaust gas heating pretreatment, effectively saving energy. Absorbents such as limestone are inexpensive, and the power plant's existing slurry circulation system can process HF in batches, eliminating the need for the addition of large amounts of additional chemical reagents. Compared to building a separate wet-process unit, the present invention consumes less water and electricity during operation, resulting in improved economics. Furthermore, the fluorine-containing byproducts generated by the HF conversion process are directly incorporated into the byproduct stream of the power plant's desulfurization system for treatment, eliminating the generation of additional solid waste or wastewater discharge. The CaF2 generated during the utilization of the limestone slurry is mixed into the desulfurization gypsum in a stable solid state and can be safely disposed of through conventional solid waste disposal routes. Finally, it should be noted that the present invention, by innovatively integrating the treatment of fluorine-containing exhaust gas from used batteries with the desulfurization system of a thermal power plant, provides an efficient, economical, and environmentally friendly HF exhaust treatment solution, overcoming the shortcomings of existing technologies and achieving the goals of improving HF removal efficiency and reducing treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 It is a structural diagram of the present invention;

[0021] Figure 2 This is a structural diagram of the wet desulfurization tower 30.

[0022] Among them, 10 is the pretreatment system, 11 is the feeding and crushing system, 12 is the heating and drying system, 13 is the screening and sorting system, 14 is the exhaust gas collection device, 20 is the acid-resistant pipe, 21 is the Venturi tube, 30 is the wet desulfurization tower, 31 is the spray assembly, 32 is the slurry pool, 40 is the demister, 50 is the monitoring system, 60 is the control unit, 70 is the wet dust collector, 80 is the chimney, and 90 is the feeding system. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0025] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0027] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0028] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0031] Example 1

[0032] refer to Figure 1 The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to the present invention is characterized in that it includes a pretreatment system 1, a venturi tube 21, a boiler smoke exhaust port and a wet desulfurization tower 30; the outlet of the pretreatment system 1 is connected to the inlet of the venturi tube 21, the boiler smoke exhaust port is connected to the inlet of the venturi tube 21, and the outlet of the venturi tube 21 is connected to the gas inlet of the wet desulfurization tower 30.

[0033] Accordingly, the HF tail gas treatment method coupled with the desulfurization system of a thermal power unit according to the present invention comprises the following steps:

[0034] The HF tail gas output by the pretreatment system 1 is evenly mixed with the boiler flue gas. The mixed flue gas enters the wet desulfurization tower 30 from bottom to top. In the wet desulfurization tower 30, the slurry contacts the HF-containing flue gas in reverse direction, dissolving the HF in the alkaline slurry droplets and undergoing a neutralization reaction. The HF is converted into a stable salt compound and remains in the liquid phase.

[0035] Example 2

[0036] refer to Figure 1 and Figure 2The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to the present invention includes a pretreatment system 1, a feeding and crushing system 11, a heating and drying system 12, a screening and sorting system 13, an exhaust gas collection device 14, an acid-resistant pipeline 20, a venturi tube 21, a wet desulfurization tower 30, a spray assembly 31, a slurry pool 32, a mist eliminator 40, a monitoring system 50, a control unit 60, a wet dust collector 70, a chimney 80 and a feeding system 90; the pretreatment system 1 includes a box body and the feeding and crushing system 11, the heating and drying system 12 and the screening and sorting system 13 arranged in the box body.

[0037] The outlet of the pretreatment system 1 is connected to the inlet of the venturi tube 21 through the exhaust gas collection device 14 and the acid-resistant pipe 20, the boiler smoke exhaust port is connected to the inlet of the venturi tube 21, the outlet of the venturi tube 21 is connected to the gas inlet of the wet desulfurization tower 30, and the gas outlet of the wet desulfurization tower 30 is connected to the inlet of the chimney 80 through the wet dust collector 70.

[0038] The wet desulfurization tower 30 includes a tower body, in which a demister 40, a spray assembly 31 and a slurry pool 32 are arranged in sequence from top to bottom. The gas inlet of the wet desulfurization tower 30 is arranged on the side of the tower body and is located between the slurry pool 32 and the spray assembly 31. The outlet of the feeding system 90 is connected to the slurry pool 32, and the outlet of the slurry pool 32 is connected to the inlet of the spray assembly 31 through a circulation pump. The gas outlet at the top of the tower body is connected to the inlet of the monitoring system 50, and the output end of the monitoring system 50 is connected to the input end of the control unit 60, and the output end of the control unit 60 is connected to the control end of the circulation pump and the control end of the feeding system 90.

[0039] The pretreatment system 1 is provided with a waste gas collection device 14. The HF tail gas collected by the waste gas collection device 14 is introduced into the flue gas system of the boiler of the adjacent coal-fired unit through the acid-resistant pipe 20, and is mixed with the boiler flue gas at the inlet of the wet desulfurization tower 30. Specifically, the original flue gas generated by the boiler combustion is sent into the gas inlet of the wet desulfurization tower 30 by the induced draft fan after dust removal and dust reduction. The HF tail gas output from the acid-resistant pipe 20 is quickly mixed with the boiler flue gas through the venturi tube 21. In this way, the originally high concentration of HF gas is diluted by a large amount of boiler flue gas, avoiding the local high concentration of HF causing corrosion to the equipment or impact on the absorbent.

[0040] The mixed flue gas enters the wet desulfurization tower 30 from bottom to top. Figure 2As shown, a three-layer spray assembly 31 is provided inside the wet desulfurization tower 30, with a number of nozzles evenly distributed on the spray pipeline of each layer. A slurry pool 32 is provided at the bottom of the wet desulfurization tower 30. The slurry pool 32 contains alkaline absorption slurry. In this example, a limestone-gypsum slurry with a mass fraction of 15% is used. The slurry is pumped out from the slurry pool 32 by a circulation pump and transported to each layer of spray assembly 31 in turn. It is then sprayed down from the nozzle to form a dense curtain of droplets, which contacts the rising HF-containing flue gas in the opposite direction. HF, as a highly corrosive acidic gas, has extremely high solubility and reactivity under wet conditions. When HF enters the spray area with the flue gas, it immediately dissolves in the alkaline slurry droplets and undergoes a neutralization reaction, being converted into a stable salt compound and remaining in the liquid phase.

[0041] For limestone slurry, HF mainly reacts with the CaCO3 and Ca(OH)2 components therein as follows: CaCO3+2HF→CaF2+CO2+H2O to generate insoluble calcium fluoride (CaF2) precipitate and by-products carbon dioxide and water.

[0042] Through multi-stage spray contact, the device of the present invention can ensure that most of the HF is captured and neutralized by the absorbent. A demister 40 is installed at the top of the wet desulfurization tower 30. It consists of multiple layers of corrugated blades and is used to intercept small droplets of slurry entrained in the air flow. After the purified flue gas passes through the demister 40, most of the droplets are removed. Then the clean gas enters the chimney 80 through the wet dust collector 70 and is discharged into the atmosphere. The HF concentration in the tail gas after treatment is far less than 1mg / m 3 (The outlet HF concentration of this device is about 0.5 mg / m 3 ), indicating that the HF removal rate is over 99%, meeting the most stringent environmental emission standards.

[0043] The present invention utilizes the existing slurry circulation system of the absorption tower to dispose of the fluorine-containing reaction products formed by HF. When the absorbent is limestone slurry, the generated CaF2 is suspended in the slurry as fine solid particles, a portion of which co-precipitates with gypsum crystals at the bottom of the slurry tank 32. As the slurry is continuously circulated, fluoride ions gradually accumulate in the slurry. To prevent excessive F- concentrations in the slurry from causing absorbent passivation or scaling, the system incorporates a slurry discharge and replenishment mechanism: a suitable amount of fluoride-rich slurry is discharged from the slurry tank 32 via a drain valve, while an equal amount of fresh limestone slurry or clean water and absorbent are added to maintain the F- concentration within a safe range, for example, below several hundred mg / L, to prevent the formation of large-scale CaF2 coatings on the absorbent surface. The discharged fluorine-containing slurry can be transported to the power plant's existing desulfurization wastewater treatment unit, where lime milk is added to further precipitate calcium fluoride solids, which are then dehydrated along with solid byproducts such as desulfurization gypsum. Through the above measures, the device of the present invention effectively avoids the adverse effects of fluoride ion enrichment on desulfurization efficiency during long-term operation, and realizes the coordinated control of simultaneous and efficient removal of HF and SO2.

[0044] To monitor the effectiveness of HF removal in real time, a monitoring system 50 is installed in the clean flue gas duct at the outlet of the wet desulfurization tower 30. The monitoring system 50 uses ion-selective electrodes to detect fluoride ions or infrared spectroscopy to detect HF gas concentration. It continuously reads the HF content in the flue gas every minute and transmits the data to a control unit 60. The control unit 60, comprised of a programmable logic controller (PLC) or industrial computer, is pre-programmed with a threshold for HF emission concentration and a corresponding coordinated control strategy. When the monitoring system 50 detects that the outlet HF concentration is approaching the threshold, the control unit 60 issues a command to increase the flow rate of the circulation pump or activate the backup spray layer to enhance HF absorption capacity. If necessary, the control unit 60 can also control the dosing system 90 to add additional slaked lime slurry or sodium hydroxide solution to the slurry to increase the slurry alkalinity and further enhance the HF neutralization and absorption rate. If an abnormal condition causes the desulfurization system's processing capacity to decline, for example, a sudden change in power plant load that causes a simultaneous increase in SO2 concentration and HF load, the control unit 60 can coordinate a temporary reduction in the amount of HF tail gas introduced, for example, through a valve on the acid-resistant pipeline 20, to ensure that outlet emissions continue to meet standards. Under normal operating conditions, the system parameters are automatically adjusted under the coordination of the control unit 60 to maintain optimal HF removal efficiency and minimum chemical consumption, thereby achieving safe and efficient long-term operation.

[0045] From the description of the above embodiments, it can be seen that the present invention cleverly integrates the HF purification process of waste lithium battery pre-processed tail gas into the existing desulfurization process of coal-fired power plants. Experimental simulation results show that under typical working conditions (for example, a 1000Nm 3 / h of HF tail gas, with an initial HF concentration of about 100 mg / m 3, introducing a flue gas volume of 200,000 Nm 3 / h power plant absorption tower treatment), the HF volume concentration in the mixed flue gas is only about 0.5ppm, and the measured HF concentration at the outlet of the absorption tower is <0.2ppm, achieving a removal rate of >99.5%, and having no significant impact on the desulfurization efficiency of the wet desulfurization tower 30. It can be seen that the present invention can significantly improve the purification efficiency of HF tail gas without significantly increasing equipment investment and operating costs, and has outstanding economic and environmental benefits. For in-service coal-fired power plants, only a small amount of modification to the existing desulfurization system is required (addition of tail gas introduction pipelines and control systems) to undertake the HF tail gas treatment task of the nearby waste battery recycling device, reflecting a strong engineering application value.

[0046] It should be noted that the above embodiments are intended to better illustrate the technical solutions of the present invention. Any equivalent substitutions or modifications made within the spirit and principles of the present invention are intended to be covered by the scope of protection of the present invention. The device structure and process steps of the present invention can be adjusted according to specific application requirements. For example, the number of spray stages, absorbent ratio, and control parameters can be optimized for power plants of different sizes and HF tail gas concentrations. All of these are within the scope of the present invention.

[0047] Those skilled in the art will readily identify other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0048] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0049] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A HF tail gas treatment device coupled with a desulfurization system of a thermal power unit, characterized in that: The invention comprises a pretreatment system (1), a venturi tube (21), a boiler exhaust port and a wet desulfurization tower (30); the outlet of the pretreatment system (1) is connected to the inlet of the venturi tube (21), the boiler exhaust port is connected to the inlet of the venturi tube (21), and the outlet of the venturi tube (21) is connected to the gas inlet of the wet desulfurization tower (30).

2. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 1, characterized in that: The gas outlet of the wet desulfurization tower (30) is connected to the inlet of the chimney (80) through the wet dust collector (70).

3. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 1, characterized in that: The wet desulfurization tower (30) comprises a tower body, wherein a demister (40), a spray assembly (31) and a slurry pool (32) are sequentially arranged in the tower body from top to bottom.

4. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 3, characterized in that: The gas inlet of the wet desulfurization tower (30) is arranged on the side of the tower body and is located between the slurry pool (32) and the spray assembly (31).

5. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 3, characterized in that: The invention also comprises a feeding system (90), wherein the outlet of the feeding system (90) is connected to the slurry pool (32).

6. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 5, characterized in that: The outlet of the slurry pool (32) is connected to the inlet of the spray assembly (31) via a circulation pump.

7. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 6, characterized in that: The gas outlet at the top of the tower body is connected to the inlet of the monitoring system (50), the output end of the monitoring system (50) is connected to the input end of the control unit (60), and the output end of the control unit (60) is connected to the control end of the circulation pump and the control end of the feeding system (90).

8. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 1, characterized in that: The outlet of the pretreatment system (1) is connected to the inlet of the venturi tube (21) via the waste gas collecting device (14) and the acid-resistant pipe (20).

9. The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 1, characterized in that: The pretreatment system (1) comprises a box body, and a feeding and crushing system (11), a heating and drying system (12), and a screening and sorting system (13) arranged in the box body.

10. A method for treating HF tail gas coupled with a desulfurization system of a thermal power plant, characterized in that: The HF tail gas treatment device coupled with the desulfurization system of a thermal power unit according to claim 1 comprises the following steps: The HF tail gas outputted from the pretreatment system (1) is uniformly mixed with the boiler flue gas. The mixed flue gas enters the wet desulfurization tower (30) from bottom to top. In the wet desulfurization tower (30), the slurry contacts the HF-containing flue gas in reverse direction, dissolving the HF in the alkaline slurry droplets and causing a neutralization reaction. The HF is converted into a stable salt compound and remains in the liquid phase.

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