A multi-zone coupled plasma reactor for treating fluorine-containing tail gas

Abstract

The utility model relates to a kind of for processing fluorine-containing tail gas multi-zone coupling plasma reactor, belong to environmental protection technology and cryogenic plasma application technical field.The reactor includes cylindrical cavity, and its inside is divided into pre-excitation zone, main reaction zone and depth conversion zone in turn along air flow direction.Pre-excitation zone carries out preliminary activation to tail gas using line-cylinder type discharge structure;Main reaction zone realizes catalysis-plasma synergic high-efficiency reaction using honeycomb porous metal electrode pair filled with supported solid catalyst;Depth conversion zone uses spiral flow channel discharge structure, ensure reaction completely.Each zone electrode pair is independently excited by a high-frequency power supply through switchable circuit.The utility model improves the processing efficiency and energy utilization rate of HF, SiF4 and other stable fluorides in wet-process phosphoric acid tail gas by multi-zone synergy and structured design, realizes efficient purification and resource recycling.

Description

Technical Field

[0001] This utility model relates to a multi-zone coupled plasma reactor for treating fluorine-containing tail gas, belonging to the field of industrial waste gas treatment technology. Background Technology

[0002] Fluorine-containing tail gas generated during industrial production processes such as wet-process phosphoric acid is complex in composition, highly corrosive, and contains chemically stable molecules such as silicon tetrafluoride (SiF4). Traditional treatment technologies such as alkaline absorption have problems such as low efficiency, easy clogging, and generation of secondary waste liquid.

[0003] Low-temperature plasma technology, as an advanced oxidation technology, has shown advantages in treating recalcitrant pollutants. However, conventional plasma reactors (such as flat-plate and cylindrical reactors) have significant shortcomings when treating fluorine-containing exhaust gases: poor discharge uniformity; insufficient contact between active particles and pollutant molecules, especially limited conversion efficiency for SiF4; low energy utilization efficiency, with some electrical energy being converted into ineffective heat energy; and a lack of targeted design, making it difficult to cope with highly corrosive environments. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a multi-zone coupled plasma reactor for treating fluorine-containing tail gas that has a reasonable structure, high processing efficiency, low energy consumption, and stable operation.

[0005] This utility model is achieved through the following scheme: a multi-zone coupled plasma reactor for treating fluorine-containing tail gas, comprising a cylindrical cavity, wherein the interior of the cylindrical cavity is sequentially divided into a pre-excitation zone, a main reaction zone, and a deep conversion zone along the gas flow direction; The pre-excitation zone is provided with a first discharge electrode pair, which consists of a rod-shaped inner electrode arranged along the axis of the cylindrical cavity and a first cylindrical outer electrode coaxially sleeved therewith, forming a wire-cylinder discharge structure. The main reaction zone is provided with a second discharge electrode pair, which is composed of at least one pair of parallel and opposite honeycomb porous metal electrodes, and the channels of the honeycomb porous metal electrodes are filled with a supported solid catalyst. A third discharge electrode pair is provided in the deep conversion zone. The third discharge electrode pair is composed of a spiral strip electrode and a cylindrical outer electrode that cooperates with it, forming a spiral flow channel discharge structure. A high-frequency power supply, the output of which is selectively connected to the first discharge electrode pair, the second discharge electrode pair, and the third discharge electrode pair via a switching or distribution circuit, and provides excitation to each electrode pair.

[0006] The pre-excitation zone is equipped with a first coil heat exchanger, and the deep conversion zone is equipped with a second coil heat exchanger.

[0007] The first coil heat exchanger covers the cylindrical outer electrode, and the second coil heat exchanger is wound around the outside of the cylindrical outer electrode.

[0008] The first coil heat exchanger and the second coil heat exchanger are provided with a cooling medium inlet and an outlet.

[0009] The honeycomb porous metal electrode channels have a pore diameter of 5-20 mm and a porosity of not less than 70%.

[0010] The supported solid catalyst uses γ-alumina or titanium dioxide as a support, and its active component is one or more of V2O5, O3 or CeO2.

[0011] The cavity sections corresponding to the pre-excitation zone, main reaction zone, and deep conversion zone are independent modules, and the modules are connected by flanges.

[0012] The beneficial effects of this utility model are as follows: 1. This utility model discloses a multi-zone coupled plasma reactor for treating fluorine-containing tail gas. Through the multi-zone coupling design of "pre-activation-main reaction-deep conversion", the discharge form is optimized for different reaction stages. In particular, the synergistic effect of the honeycomb catalytic electrode greatly improves the removal rate of stable fluorides such as SiF4.

[0013] 2. The present invention provides a multi-zone coupled plasma reactor for treating fluorine-containing tail gas. Through independent power supply to each zone, it can achieve on-demand power supply. The integrated heat exchanger effectively manages the heat of reaction and reduces the energy consumption of the system operation.

[0014] 3. The honeycomb electrode of the multi-zone coupled plasma reactor for treating fluorine-containing tail gas of this utility model has the functions of catalysis, discharge and flow conduction, and has high structural strength; the modular design makes the reactor highly adaptable and easy to maintain.

[0015] 4. The overall material selection and structural design of the multi-zone coupled plasma reactor for treating fluorine-containing tail gas of this utility model fully consider the strong corrosiveness and composition characteristics of fluorine-containing tail gas, resulting in a long equipment life and reliable operation. Attached Figure Description

[0016] Figure 1 This is a front view cross-sectional structural diagram of a multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to the present invention.

[0017] Figure 2 This is a front view schematic diagram of the electrode pair of a multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to the present invention.

[0018] Figure 3This is a side view of the first discharge electrode pair of a multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to the present invention.

[0019] Figure 4 This is a side view of the second discharge electrode pair of a multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to the present invention.

[0020] Figure 5 This is a side view of the third discharge electrode pair of a multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to the present invention.

[0021] In the figure: 1 is a cylindrical cavity, 2 is the pre-excitation zone, 3 is the main reaction zone, 4 is the deep conversion zone, 5 is the first discharge electrode pair, 5a is the rod-shaped inner electrode, 5b is the first cylindrical outer electrode, 6 is the second discharge electrode pair, 7 is the supported solid catalyst, 8 is the third discharge electrode pair, 8a is the spiral ribbon electrode, 8b is the cylindrical outer electrode, 9 is the high-frequency power supply, 10 is the first coil heat exchanger, and 11 is the second coil heat exchanger. Detailed Implementation

[0022] The following is combined Figure 1-5 The present invention will be further described below, but the scope of protection of the present invention is not limited to the contents described herein.

[0023] Identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. Furthermore, the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the purpose of illustrating the embodiments of this utility model.

[0024] For clarity, not all features of the actual embodiments will be described. In the following description, well-known functions and structures will not be described in detail, as they would confuse the present invention with unnecessary details. It should be understood that in the development of any actual embodiment, a great deal of implementation detail must be made to achieve the developer’s specific goals, such as changing one embodiment to another according to the limitations of the system or business. In addition, it should be understood that such development work may be complex and time-consuming, but is merely routine work for those skilled in the art.

[0025] Example 1: This example focuses on the design of the reactor for the tail gas generated by a large-scale wet-process phosphoric acid production unit. The reactor adopts a segmented structure. The cylindrical cavity is made of high-purity reaction-sintered silicon carbide ceramic, which has excellent resistance to hydrogen fluoride corrosion, high temperature resistance, and thermal conductivity. The total length of the cavity is 3 meters, and the inner diameter is 800 mm. The sections are sealed together by high-strength acid-resistant stainless steel flanges, forming a pre-excitation zone, a main reaction zone, and a deep conversion zone in sequence.

[0026] In actual operation, the process exhaust gas containing HF and SiF4, with a temperature range of 80-100℃, first enters the pre-excitation zone. This zone is equipped with rod-shaped inner electrodes and cylindrical outer electrodes made of Hastelloy C-276 material, forming a wire-cylinder discharge structure. A high-frequency power supply provides an excitation signal of 15kHz and 8kV to this electrode pair, generating uniform corona plasma to achieve preliminary activation and preheating of the exhaust gas. Simultaneously, a coil-type heat exchanger covering the outer electrode surface is circulated with factory circulating cooling water (inlet water temperature 25℃), controlling the reaction zone temperature below 50℃ and producing warm water at approximately 35℃ for reuse in the production process.

[0027] The pre-activated gas then enters the main reaction zone. This zone is centered around a pair of vertically opposed honeycomb porous metal electrodes. The electrode substrate is Inconel 625, and the honeycomb structure consists of square channels with a pore size of 12 mm and a porosity of 78%. A specialized catalyst, using mesoporous γ-alumina as a support and CeO2 and WO3 as active components, is loaded onto the inner walls of the channels via a sol-gel process. Under 20 kHz / 12 kV excitation provided by a high-frequency power supply, a strong dielectric barrier discharge is formed within the channels. Through the synergistic effect of plasma and catalyst, efficient cracking and conversion of HF and SiF4 are achieved.

[0028] Finally, the gas enters the deep conversion zone. This zone employs a titanium spiral ribbon electrode and a matching external electrode to form a spiral flow channel discharge structure, with the pitch gradually decreasing from 150mm at the inlet to 100mm at the outlet. A 10kV voltage is applied here by a high-frequency power supply to form a stable surface discharge, ensuring the complete removal of residual contaminants. A coil-type heat exchanger is also installed on the outer wall of this zone to further recover waste heat from the reaction.

[0029] The reactor described in this embodiment can process gas volumes up to 20,000 Nm³. 3 The system achieves a comprehensive fluoride removal rate consistently above 99.2% per hour and recovers approximately 150kW of heat energy per hour through a heat recovery system, demonstrating significant energy-saving effects.

[0030] Example 2: This example is designed for small and medium-sized phosphate plants or experimental research and development scenarios, emphasizing modularity, intelligence, and economical operation of the equipment. The reactor chamber is 1.2 meters long and 300 millimeters in inner diameter, made of polytetrafluoroethylene (PTFE). The sections are connected by quick-connect flanges with sealing rings, facilitating disassembly and reassembly.

[0031] The main features of this embodiment are reflected in three aspects: First, the honeycomb porous metal electrode in the main reaction zone adopts a replaceable modular design. Users can select electrode modules with different catalyst systems according to the silicon content in the exhaust gas (which directly affects the SiF4 ratio)—when the SiF4 content is high, a formulation loaded with V2O5-WO3 is selected to enhance the activation of Si-F bonds; when the exhaust gas is mainly HF, a formulation loaded with CeO2 can be used to optimize the cracking effect on HF bonds.

[0032] Secondly, the system is equipped with a high-frequency power supply with intelligent control functions. This power supply integrates a control unit and is linked to the fluoride ion concentration sensors at the reactor inlet and outlet, enabling it to automatically adjust the energy supply to each zone based on real-time changes in the inlet pollutant concentration. Under low-load conditions, the system can automatically shut down or reduce the power of the pre-excitation zone and the deep conversion zone, maintaining only the main reaction zone at its optimal energy efficiency point, thereby significantly reducing energy consumption at low loads.

[0033] Third, the thermal management system has been simplified. Two coil-type heat exchangers can be connected in series to the same cooling loop, simplifying the piping layout. For applications with small throughput and low temperature rise, only a single heat exchanger can be used or natural air cooling can be employed, further reducing system complexity and operating costs.

[0034] The reactor in this embodiment is suitable for 1,000-2,000 Nm³. 3 With a gas volume range of [number] / h, it excels at handling operating conditions with large gas volume fluctuations. Its modular structure facilitates maintenance and catalyst replacement, and combined with intelligent power regulation, it can save more than 30% of electricity compared to traditional continuous full-load operation, giving it a significant advantage for small and medium-sized enterprises that are sensitive to operating costs.

[0035] Although the technical solutions of this utility model have been described and enumerated in detail, it should be understood that modifications to the above embodiments or the adoption of equivalent alternatives are obvious to those skilled in the art. Such modifications or improvements made without departing from the spirit of this utility model are all within the scope of protection claimed by this utility model.

Claims

1. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas, comprising a cylindrical cavity (1), characterized in that, The cylindrical cavity (1) is divided into a pre-excitation zone (2), a main reaction zone (3) and a deep conversion zone (4) along the airflow direction. The pre-excitation zone (2) is provided with a first discharge electrode pair (5), which is composed of a rod-shaped inner electrode (5a) arranged along the axis of the cylindrical cavity (1) and a first cylindrical outer electrode (5b) coaxially sleeved therewith, forming a wire-cylinder discharge structure. The main reaction zone (3) is provided with a second discharge electrode pair (6), which is composed of at least one pair of honeycomb porous metal electrodes that are parallel to each other and opposite to each other. The pores of the honeycomb porous metal electrodes are filled with a supported solid catalyst (7). The deep conversion zone (4) is provided with a third discharge electrode pair (8), which is composed of a spiral strip electrode (8a) and a cylindrical outer electrode (8b) that cooperates with it, forming a spiral flow channel discharge structure; A high-frequency power supply (9) is provided. The output terminal of the high-frequency power supply (9) is selectively connected to the first discharge electrode pair (5), the second discharge electrode pair (6), and the third discharge electrode pair (8) through a switching or distribution circuit, and provides excitation to each electrode pair.

2. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 1, characterized in that, The pre-excitation zone (2) is equipped with a first coil heat exchanger (10), and the deep conversion zone (4) is equipped with a second coil heat exchanger (11).

3. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 2, characterized in that, The first coil heat exchanger (10) is wrapped around the first cylindrical outer electrode (5b), and the second coil heat exchanger (11) is wound around the outside of the cylindrical outer electrode (8b).

4. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 2, characterized in that, The first coil heat exchanger (10) and the second coil heat exchanger (11) are provided with a cooling medium inlet and an outlet.

5. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 1, characterized in that, The honeycomb porous metal electrode channels have a pore diameter of 5-20 mm and a porosity of not less than 70%.

6. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 1, characterized in that, The supported solid catalyst (7) uses γ-alumina or titanium dioxide as a support.

7. A multi-zone coupled plasma reactor for treating fluorine-containing tail gas according to claim 1, characterized in that, The cavity sections corresponding to the pre-excitation zone (2), the main reaction zone (3), and the deep conversion zone (4) are independent modules, and the modules are connected by flanges.

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