Production Of NO_x By Arc Discharge And Its Oxidation On Concentrated Ammonium Sulfite

Coal is the primary source of energy in China. It is reported that nearly seventy percent of energy comes from the burning of coal in China, in2012. Sulfur dioxide (SO2) and nitrogen oxide (NOX) in the atmosphere are mainly come from coal-fired flue gas. SO2and NOx could lead to acid rain, and furthermore affect the atmospheric environment. In addition, they do harm to human body, plants, and buildings.There are diverse desulfurization and denitration technologies for flue gas. Wet ammonia-based desulfurization technology could capture SO2effectively. While it can lower the operating capital for that the final by-product ammonium sulfate is a good fertilizer. However, the oxidation of the concentrated ammonium sulfite to ammonium sulfate is hard to be achieved. Conventional ammonium sulfite oxidation techniques are based on air-forced oxidation processes. Its main drawbacks are low oxidation rate and relatively high energy consumption. Operation and construction cost would greatly rise if the solution is diluted for oxidation. In this paper, we studied the reaction of concentrated ammonium sulfite and NOx (the main effective components was NO2), which can be generated by arc discharge in air.The difference of discharge forms and mechanism of NOx formation in air arc discharge was analyzed. The experiment devices of air arc discharge and ammonium sulfite oxidation were designed, respectively. And the experiment mainly have two parts:producing NOx and ammonium sulfite oxidation. The results and discussion were also analyzed.In this paper, NOx was generated by a high frequency AC power source and a pair of needle-needle stainless steel electrodes. Several parameters which could influence the NOx concentration and the ratio of NO2/NOx were investigated. They mainly contains as discharge gap, air flux, humidity, and oxygen content. Discharge gas products were analyzed by fiber optic spectrometer and FTIR for better understanding. Results showed that NOx concentration and N02/NOx could be increased by larger discharge gap or lower gas flux and humidity. The maximum value of NO2concentration and N02/NOx were obtained when oxygen content was50%and60%, respectively.The NOX producted by air arc discharge was used for oxidizing concentrated ammonium sulfite. NOx injection methods, gas phase parameters (gas flow, gas concentration, etc.) and solution parameters (solution concentration and pH), which could impact the oxidation process were studied. Results showed that aeration was the best way for injection and oxidation. When the concentration of ammonium sulfite was above1.0mol/L, the air oxidation effect could be negligible; while using NOX, the maximum oxidation effect appeared when gas flow was1.75L/min. The solution concentration significantly impacted the oxidation rate and1.2mol/L was the best value. The best oxidation rate was obtained at pH6.5. And solution pH decreased with increasing reaction time.