Device for treating waste gas by microwave plasma

Abstract

The invention provides a device for treating waste gas by microwave plasma, and belongs to the field of environment protection. The device mainly comprises a microwave plasma generator, a gas to be treated entering device, a gas detection system and a tail gas treatment system, wherein the gas to be treated is introduced into the gas to be treated entering device in a tangential air flow mode to form rotational air flow to pass through a gap of a coaxial metal pipe; heat released by a plasma torch performs preheating on the gas passing through the gap of a coaxial pipe through the coaxial inner metal pipe wall heat transfer; then, the gas is added to a discharging pipe outlet position of the microwave plasma generator from the opening end of the gas to be treated entering device to be effectively mixed with the plasma torque formed by discharging of the spiral air flow injected from the gas injection unit of the microwave plasma generator; chemical reaction is taken; waste gas is removed. The device provided by the invention has the advantages that the investment cost is low; the system structure is simple; the stable and durable operation of the microwave waste gas treatment device is maintained under the condition of reducing the energy consumption; the waste gas removal efficiency is improved.

Description

technical field [0001] The invention belongs to the field of environmental protection and relates to a harmful waste gas treatment technology, in particular to a device for treating waste gas by using microwave plasma. Background technique [0002] In recent years, the problem of environmental pollution has become more and more serious, especially air pollution. Many industrial production emissions, such as perfluorinated gas in the semiconductor industry, have strong infrared absorption in the atmosphere, CF 4 The ability to absorb infrared is CO 2 Therefore, it will aggravate the greenhouse effect, increase the global average temperature, and become the main cause of climate anomalies; secondly, the flue gas produced by coal furnace combustion, including sulfide and nitrogen oxides, stimulates the human respiratory system and damages the human body. Good health, but also produce acid rain, destroy the earth's ecological environment, cause photochemical pollution and so o...

AI Technical Summary

Problems solved by technology

However, the existing technology of this method still has practical problems such as the mutual constraints of stability control and processing efficiency, low power unit utilization, and further cost reduction.

[0005] In recent years, many scholars at home and abroad have carried out research on the removal of gas by microwave plasma torch. The most common method is to obtain a stable plasma torch through microwave discharge of the working gas in the plasma discharge tube, and then use the waste gas to be treated as A certain proportion is passed into the main discharge area where the electromagnetic wave of the plasma discharge tube is coupled with the plasma, so as to obtain a higher removal efficiency, but this will also bring some problems, for example, because the waste gas to be treated is added to the main discharge area In the middle, the gas discharge in this area is greatly affected, and in some cases it will even lead to the instability of the discharge, and even serious extinguishment of the plasma discharge

In addition, the decomposition of the waste gas to be treated in the plasma discharge will produce some by-products attached to the wall of the discharge tube in some cases, and when these by-products have a strong absorption of microwaves, they will significantly attenuate the microwaves. During the action, the deposition on the tube wall will seriously affect the coupling efficiency of the microwave plasma. As time goes by, the coupling becomes worse and worse, and finally leads to the quenching of the plasma discharge.

For example, the harmless treatment system using microwave plasma to decompose Freon introduced in the patent No. CN20150986U provides a mild decomposition condition, complete reaction, no pollution, energy saving, low cost and easy industrial application, but because The decomposition of freon is carried out in the discharge tube of the plasma reactor. Substances such as carbon that may be produced by the decomposition of freon adhere to the inner wall of the discharge tube. The direct result is that the microwave coupling efficiency is reduced and the discharge is affected.

In addition, the public number CN102824829A patent introduces an application technology for the removal of carbon tetrafluoride and nitrogen oxide gas by using catalyst-assisted microwave plasma. This technical solution reduces energy consumption and also achieves a stable removal effect, but The catalyst needs to be replaced regularly, which brings problems such as high operating costs and cumbersome operating procedures

[0006] Based on the above technical methods and implementation plans for waste gas treatment, it can be concluded that there are the following main problems in the method of microwave plasma torch removal of waste gas: (1) because the waste gas is added to the main discharge area of ​​the plasma torch from the inlet upstream of the discharge tube It may cause the problem of discharge instability; (2) The by-products deposited on the inner wall of the discharge tube seriously affect the microwave coupling efficiency; (3) Due to the change of the gas composition, the coupling condition changes in real time and the matching condition is difficult to achieve the best condition, resulting in the unit energy low utilization

Microwave plasma torch treatment of waste gas is a new technology developed in the 1990s. At present, more researches are on the combined use of microwave plasma torch and catalyst. There is no research on waste gas and working gas in microwave plasma torch. Relevant reports on the technical improvement of the way of coupling and entry to further improve the efficiency of exhaust gas removal

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