Research On NO_x Waste Gas Treatment In Thermal Power Plant Based On Gas-liquid Two Phase DBD

Nitrogen oxide (NOx) is one of the major air pollutants, it not only endangers the health of human beings and animals, but also destroys the ecological environment. Because the thermal power plant is the main source of NOx emissions, the control of NOx emissions from thermal power plants has become an urgent problem to be solved in electric-power industry. Compared with other nitrogen oxides processing technology, low temperature plasma technology has many advantages such as small floor area, low investment and no secondary pollution. At present, plate plate electrode is usually be adopted in the field of plasma exhaust treatment,while this paper studied the influence of the plasma produced from gas-liquid two phase dielectric barrier discharge(DBD) reactor on the removal of NOx under normal temperature and pressure environment.Hydroxide radical (OH) plays an important role in NOx removal, so the types and distribution characteristics of active groups in plasma were diagnosed by emission spectroscopy analysis, the effects of liquid composition, peak voltage, power frequency and relative humidity on OH radical were analyzed. The main conclusions are: the spectral intensity of OH radical increases with NaOH solution concentration, peak voltage and power frequency; with the increase of air relative humidity, the spectral intensity of OH radicals increases first and then decreases. Under the same experimental conditions, OH radicals spectral intensity of gas- liquid two phase DBD is far more than plate plate electrode DBD, so it is more adapt to the removal of NOx.Secondly, this paper studies the influence of peak voltage, gas residence time, NOx initial concentration, gas flow rate, the concentration of NaOH solution, and air relative humidity on the removal rate of NOx and the amount of NO2 formation of gas- liquid two phase DBD,compared and analyzed the NOx removal of gas- liquid two phase DBD and plate plate electrode under the same experimental conditions. The results show that: the removal rate of NOx is directly proportional to the peak voltage, and reaches the maximum value when the peak voltage is 21kV;the removal rate of NOx increases with the gas residence time, and the maximum value is reached when the gas stays more than 30s; NOx removal rate decreased with the increase of NOx concentration and gas flow rate; NOx removal rate increased with the NaOH solution concentration, and when the NaOH concentration is 1.5mol/L, the removal rate reached its maximum; the removal rate of NOx increased with the air relative humidity firstly and then decreased significantly, the NOx removal rate reached the peak when the relative humidity was 50%; amount of NO2 formation of dielectric barrier discharge whose ground electrode made of sodium hydroxide solution is far more less than traditional plate plate electrode. Under the same experimental conditions, NOx removal rate of gas-liquid two phase DBD was significantly greater than plate plate electrode DBD.The research results of this paper provide theoretical basis for the application of gas-liquid two-phase DBD in thermal power plant.