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Emission spectrum diagnosis of the reaction process temperature of the plasma cleaning system

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09 Nov,2020

Emission spectrum diagnosis of the reaction process temperature of the plasma cleaning system:

Emission spectrum diagnosis of the reaction process:

 

There are many chemical reactions in atmospheric plasma of plasma cleaning system. These chemical reactions can be used to synthesize high value-added chemical raw materials, modify the surface of materials and degrade environmental pollutants. Chemical reactions vary, but they are essentially recombinations of atoms or groups of atoms into products. The electrons, ions, excited atoms, molecules and free radicals in plasma are very active reaction species, which can change the chemical reaction path effectively in the process of chemical reaction. Spectroscopic diagnosis can directly obtain the type and intensity of the active species in the plasma and provide experimental basis for revealing the chemical reaction mechanism.

 

The main product of CH4 in atmospheric pressure DC discharge plasma is C2H2. CH3, CH, H, C2 and C active species can be found in the CH4 plasma from the emission spectrometric diagram of CH in the atmospheric pressure DC discharge plasma. According to the spectral detection results, C-H fracture of CH4 directly occurs in the plasma, and CH active species is the main reaction intermediate species.

 

Emission spectrum diagnosis of system temperature:

 

In atmospheric plasma, the electron temperature of plasma is difficult to be measured due to the interference of probe and other diagnostic techniques. However, the temperature of plasma system at atmospheric pressure can be achieved by studying the rotational temperature of gas molecules. It is a convenient and feasible method to collect the plasma gas temperature data by emission spectrum, which will not affect the discharge process and can obtain the discharge temperature accurately. High gas density in the atmospheric pressure plasma, frequent collision of gas molecules and ions, not only makes the ion balance the number of particles on the rotational level, and translational temperature reach equilibrium with the gas molecules and the rotation of the molecules can reach thermal equilibrium and the translational energy of the particles of relaxation time is very short, it is generally believed rotational temperature and gas temperature in the process of discharging is close to equal, therefore plasma cleaning system can be calculated by measuring the high rotation spectrum of rotational temperature, so as to estimate the gas temperature of plasma.

 

Spcair is a software that calculates the isomeric spectrum based on the particle number distribution on the energy level satisfying boltzmann distribution. Since its characteristic parameters include each characteristic temperature of the plasma, the plasma temperature at atmospheric pressure can be easily obtained by comparing the actual measured spectrum and the calculated spectrum of the plasma.

 

To determine plasma temperatures, the oscillatory and rotational temperatures of chlorine molecules were determined by spectrometric measurements of the second positive N2(C3π) emission spectra compared with those simulated using Speair. The second positive band N2(C3π) emission spectra of nitrogen molecules and the second positive band emission spectra of ammonia molecules were obtained by dielectric barrier discharge at atmospheric pressure at discharge voltage 25.4kV, discharge frequency 13.8kHz and flow rate of N2 at 100ml/min. It can be seen from the result diagram that the fitting spectrum is very consistent with the experimental spectrum. Specair can directly obtain that the rotation temperature of the gas under the above experimental conditions is 520K, and the plasma temperature is also 520K. When the discharge voltage is 30kV and 33kV respectively at the same discharge frequency, the plasma temperature is 580K and 600K.

Emission spectrum diagnosis of the reaction process temperature of the plasma cleaning system

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