Research On Decompositions Of Ammonia And Hvdrogen Sulfide Of Simulated Sludge Drying Waste Gas By Non-thermal Plasma

As thermal drying has the advantages of stabilizing the sludge and reducing the volume of sludge, it is a necessary intermediate common to all disposal methods. However it is the emissions of odorous gas pollutants produced during the drying process that restricts the development of sludge drying. Among all the gas pollutants emitted from sludge drying, the concentrations of NH3and H2S are two orders of magnitude higher than the other pollutants. At present, chemical adsorption and bio filtration are the most common methods for odor controlling. While both of them have limitations in treating pollutants with complicated compounds and have exorbitant operating cost. Non-thermal plasma, as a novel waste gas control technology, has been widely investigated by researchers from all around the world and their studies have demonstrated that gas pollutants can be decomposed by non-thermal plasma efficiently under atmospheric pressure.In this research, a novel non-thermal arc plasma was applied in treating gas pollutants. The simulated sludge drying waste gas consists of NH3and H2S, the concentrations of which were300mg/m3and200mg/m3. Influences of applied voltage and gas flow on pollutants removal efficiencies, energy utilization and the concentrations of byproducts were investigated; and comparison of pollutants removal efficiencies, energy utilization and the concentrations of byproducts from decomposition of single pollutant and gas mixture was also made. A preliminary study on the decomposition of NH3by dielectric barrier discharge was conducted as well. The main conclusions consist of the following three parts:(1) When treating single NH3and H2S, both of them can be effectively removed by the non-thermal arc plasma, and the removal efficiencies of both NH3and H2S increased with the increase of applied voltage. When applied voltage was11kV, the removal efficiency of NH3decreased with the increase of gas flow rate, a removal efficiency of100%was obtained at the gas flow rate of8-16L/min; and the best energy utilization-10.26g/kWh was gained at the gas flow rate of10L/min. At the voltage of11kV, the removal efficiency of H2S kept100%when gas flow increased from8L/min to16L/min. The best energy utilization the value of which was6.83g/kWh was achieved when the gas flow rate was16L/min.(2) At the voltage of11kV, the removal efficiency of H2S from the mixture was the same with that of single H2S; while the best removal efficiency of NH3from gas mixture was92.5%, which was a little lower than that of single NH3. It is obvious that, after mixing, the concentrations of NO and SO2decreased; and the energy utilization was60.6%and133.3%higher after mixing, respectively.(3) When dealing with NH3in the same background gas, the removal efficiency of NH3increased with the increase of applied voltage; while under the same voltage, removal efficiency of NH3from the mixture of NH3and N2was much more higher that from the mixture of NH3and Ar. When background gas was Ar, at the voltage of11kV, the efficiency of NH3dramatically decreased with the increase of gas flow rate.