JP3421804B2 - Discharge gas treatment method and treatment apparatus utilizing heat cycle - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to exhaust gas NOx treatment using discharge-excited chemical reaction, VOC polluted air treatment, and gas treatment such as ozone generation.

[0002]

2. Description of the Related Art Discharge is performed in a gas near atmospheric pressure, and N,
Development of a method for generating active species such as O and OH and treating pollutants such as NOx and VOC (volatile organic compounds) contained in gas by utilizing chemical reactions involved in them is under way. . A device that produces ozone in a similar manner is commercially available as an ozonizer.

In the gas treatment apparatus utilizing such a discharge-excited chemical reaction, it is possible to improve the generation efficiency of active species and the applied voltage by lowering the gas pressure. Proposals have already been made regarding a method of improving performance by applying such reduced-pressure discharge. (The Institute of Electrical Engineers of Japan, A, 116-9, P791 (1996), JP-A-11-475.
44) In these methods, although a method such as gas injection is devised, as for the pressure reduction of the discharge vessel, as shown in FIG. This is a system in which the processing gas is processed in the discharge vessel and exhausted.

[0004]

The gas treatment method applying such a reduced pressure discharge has a problem that the energy required for the pressure reduction is large and a large amount of electric power is required to drive the vacuum pump. However, this point has not been sufficiently studied so far.
When the gas to be processed has a pressure of atmospheric pressure or higher, depressurization to atmospheric pressure does not require energy injection, and energy is required when depressurizing to atmospheric pressure or lower. Therefore, in the following, a case will be considered in which the gas to be treated is at atmospheric pressure and the pressure is reduced.

In this case, the energy required for decompression can be estimated by treating the decompression process as adiabatic expansion. That is, the minimum energy required for adiabatic expansion is given by the amount of enthalpy reduction of the gas to be treated from thermodynamic considerations. For example, the required energy for adiabatic expansion of nitrogen gas at room temperature from 1 atm to 0.5 atm is 54 J / g. This energy has a concentration of 300 pp
When it is used for processing the gas component of m, the energy consumption for processing one molecule is 52 eV. When NOx treatment is performed by atmospheric pressure discharge, the energy required to treat one NOx molecule is 20 to 200 eV / molecule, so it is not easy to produce an effect that exceeds the energy required to reduce pressure.

[0006]

In order to solve the above-mentioned problems, the present invention according to claim 1 reduces the pressure by expanding the gas to be treated, discharges it under reduced pressure, and then compresses it. A part of the work required for this compression process is recovered in the expansion process, and then the cycle of releasing the energy injected / heated by the discharge is repeated. is there.

In order to achieve the above object, the invention according to claim 2 is to perform a compression process by expanding the gas to be treated.
A pressure reducer that collects a part of the required work , and after passing through the pressure reducer
The processing container that discharges under a reduced pressure to process the gas to be processed, and the gas processed in the processing container is compressed and exhausted to discharge
A discharge gas treatment device utilizing a heat cycle, which is characterized by comprising a compressor for radiating the energy injected / heated by.

[0008]

First, the basic principle of the present invention will be described. In the present invention, the cycle of expansion (decompression) → discharge → compression → heat dissipation is repeated. The energy injected and heated by the discharge is released by the heat dissipation process.

This cycle is one of the heat pump cycles.
It is a seed and corresponds to performing the heating process by electric discharge. The most practical use of the Brayton cycle is as a heat pump cycle for gas treatment. in this case,
The cycle is adiabatic expansion → isobaric heating (discharge) → adiabatic compression → isobaric cooling. In this case, work is performed in the compression process, and a part of the work amount is recovered in the expansion process. Considering an ideal case, the ratio of the discharge input Ein and the work amount Win input from the outside is calculated by using the compression / expansion pressure ratio β and the constant pressure specific heat / constant volume specific heat γ of the gas to be treated.

[Equation 1] Given in.

For example, when the normal temperature nitrogen gas is decompressed to 1/2 atm, Win / Ein becomes 0.22. That is, the pressure can be reduced to 1/2 by putting about 1/5 of the energy of the discharge input into the decompression work. Along with this, it is possible to improve the generation efficiency of active species and halve the applied voltage, and it can be expected that the total energy efficiency will be improved.

FIG. 1 shows an embodiment of the present invention. FIG. 1 shows an embodiment using a mechanism similar to that of a gas turbine engine.
The difference from the gas turbine engine is that the arrangement of the turbine and the compressor is reversed in order to reduce the pressure in the central discharge vessel.

In the apparatus shown in FIG. 1, the motor 1 drives the compressor 2 to reduce the pressure in the discharge vessel 3. Discharge is performed in the discharge vessel 3 under reduced pressure, and gas treatment such as NOx removal is performed by a discharge-excited chemical reaction. The turbine 4 is driven when the atmospheric pressure target gas flows into the reduced pressure discharge vessel 3. The drive shaft 5 is directly connected to the turbine 4 and the compressor 2, and the driving force obtained by the turbine 4 is used to drive the compressor 2. As a result, the load on the motor 1 for reducing the pressure inside the discharge vessel 3 can be reduced. Discharge vessel 3
The gas that has been subjected to the discharge treatment is pressurized to the atmospheric pressure by the compressor 2 and is discharged.

[0013]

Since the present invention is configured as described above,
The invention according to claim 1 and claim 2 improves the generation efficiency of active species and reduces the applied voltage by performing discharge under reduced pressure in gas treatment such as NOx removal and ozone generation using discharge-excited chemical reaction. Is possible. As a result, it is possible to improve the overall energy efficiency of the gas treatment device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a gas treatment device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a conventional low pressure discharge gas treatment apparatus.

[Explanation of symbols]

1 motor 2 compressor 3 discharge vessel 4 turbine 5 drive shaft

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Claims (2)

(57) [Claims] 1. A gas to be treated is decompressed by expanding it, discharged under reduced pressure and then compressed, and a part of the work required for this compression process is recovered in the expansion process.
A discharge gas treatment method using a heat cycle, characterized in that a cycle of releasing the energy injected / heated by discharge is repeated. 2. Compressing by expanding the gas to be treated
A pressure reducer that recovers a part of the work required for the process, and a pressure reducer
After the passage, a processing container that discharges under reduced pressure to process the gas to be processed, and the gas processed in the processing container is compressed and exhausted ,
A discharge gas treatment device using a heat cycle, which comprises a compressor that radiates the energy injected / heated by electric discharge.