Plasma Generation Based On Back Corona Discharge And Its Catalysis Application For Volatile Organic Comdpounds Removal

Volatile organic compounds (VOCs) is an important air pollutant. The total anthropogenic source VOCs emission in China is very large, and the VOCs pollution in typical industry is very serious. For the large flow and low concentration of VOCs, the application of traditional control technology is restricted by the factors such as investment, operation cost and removal efficiency. The non-plasma catalysis technology is considered to be one of the promising technologies for VOCs treatment. There are several techniques to generate non-thermal plasmas, such as corona discharge, pulsed corona, dielectric barrier discharge (DBD), electron beam and microwave, etc.. Nowadays, the plasma generation techniques are still difficult to satisfy both the conditions of high energy efficiency and the economic and reliable power supply. By-products such as CO, ozone, NOx and aerosol can be produced in the plasma VOCs treatment process. By combined with the catalyst, plasma catalysis can control the gas phase by-products, but the aerosol produced in the plasma process can induce the deactivation of catalyst.On the problems of plasma generation technology and VOCs treatment, plasma generation method powered by DC power source is studied in this work. For this method, the plasma is generated on honeycomb catalyst in the process of back corona discharge. Based on the back corona plasma generation method, a hybrid VOCs treatment system consists of back corona discharge reactor combined with a tubular DBD reactor up-stream and catalyst bed down-stream is proposed.The main research contents and results are as follows:(1) The characteristics of the back corona discharge on honeycomb catalyst and the discharge mechanism are investigated in this section. Based on back corona discharge on honeycomb catalyst, the plasmas are generated both of along the surface and in the channel of honeycomb catalyst. Middle auxiliary electrode can limit the development of current and produce uniform back corona plasma. The changing and adjusting of voltage value in middle auxiliary electrode is benefit the generation of back corona plasma.By using the negative corona discharge, stable back corona discharge can be realized. The factors of honeycomb pore size, catalyst type, thickness of honeycomb, and humidity can affect the back corona plasma generation. A flow velocity of1.99m/s of ionic wind can be realized in BCD at an applied voltage of30kV and a discharge current density of12.7?A/cm2. And at the downstream of honeycomb catalyst, flow velocity of0.5m/s still can be achieved.The ozone generation of back corona discharge on catalyst is directly proportional to the discharge current. For AgMnOx/Al203catalyst,94.8%toluene removal efficiency is observed at the specific input energy of286J/L. The total particle weight removal efficiency is about94%at the applied voltage of30kV and discharge current of358?A.(2) For removal of n-hexane in two-stage plasma catalysis reactor, the influences of catalyst type, energy density, humidity, and temperature are investigated in this section. The AgMnOx catalyst has a higher performance of n-hexane removal efficiency, plasma catalysis synergy effect, the removed amount of the n-hexane at the same ozone consumption, the ozone demand factor.(3) The hybrid plasma catalysis reactor mainly consists of3stages that are the tubular DBD reactor, back corona discharge reactor and catalyst bed. This hybrid process can overcome the adverse effect of aerosols produced in the process of plasma catalysis for VOCs removal. The ionic wind due to the back corona discharge can be actively used to reduce the pressure drop of the reactor.The G-value of ozone generation and toluene removal in tubular DBD reactor is about4.08molecules/heV and0.40molecules/heV, respectively. The C-C and C-H are the main components of aerosols produced in plasma process for VOCs removal. Both of ozone decomposition and toluene removal efficiency are improved by combined with back corona discharge on catalyst.(4) The main reaction of VOCs removal is radical reaction process in plasma. The amount of the pollutant removed is directly proportional to the plasma energy density.