Experimental Study And Numerical Simulation Of The Liquid Compound Additives Removing NO

Nitrogen oxide?NO_X?is the main gaseous pollutant emitted from coal-fired power station.Among the existing technologies about removing NO in flue gas,selective non-catalytic reduction?SNCR?technology is widely used in power plant boilers because of its simple system and low cost.However,SNCR technology requires a high temperature and a narrow denitrification temperature window.When the boiler is operated at a low load,the NO removal efficiency will obviously decrease so that it can't meet the increasingly strict emission standards.Therefore,in order to improve the NO removal efficiency of flue gas and develop a cheap and easy-to-obtain liquid compound additive which can widen the temperature window of removing NO in flue gas at moderate temperature,the influence of liquid compound additives on the NO removal process was studied by experiment and numerical simulation through simulating the actual flue gas environment.In this research,the effects of liquid additives ethanol and methanol on the NO reduction in flue gas NO removal reaction and the emission of secondary pollutants?N₂O,NO₂ and NH₃?were studied experimentally in an electrically heated tubular flow reactor.The initial NO concentration was 410 ppm?equivalent to mass concentration500mg/m³?,and the oxygen content was 3%.The ammonia-nitrogen ratio was 1.25,and N₂ was used as equilibrium gas.When no additive was added,the NO conversion was less than 10%during 700-800?with urea as reducing agent.When ethanol was added,the optimum molar ratio of ethanol to NO was 0.6,and the NO conversion was29%-56%during 700-800?.When methanol was added,the optimum molar ratio of methanol to NO was 0.8,and the NO conversion efficiency is increased by about 40%compared with that without methanol in the temperature range of 600-700?.Then,the effect of liquid compound additive?ethanol,methanol and sodium sulfate?on the reduction of NO was studied,which showed that the role of methanol in the compound additive was mainly reflected in the range of 650-750?to improve the NO conversion efficiency,which was beneficial to widening the temperature window on the low-temperature side.Ethanol can promote NO conversion efficiency after 800?,and sodium sulfate can slightly improve NO conversion efficiency overall.Considering the oxidation effect of methanol additive in flue gas NO removal process can't be ignored,the process of flue gas NO removal with methanol as additive and without reducing agent was studied experimentally.The initial concentration of NO and SO₂ were both 410 ppm and the oxygen content was 3%.It was found that when molar ratio of methanol to NO was1.25,the NO conversion efficiency was 88.6%at 650?,and NO conversion efficiency was over 75%at the range of 600-700?.Besides,the optimum reaction temperature shifted 50?to the low temperature side.Adding SO₂ inhibited the oxidation of NO by methanol.Finally,the NO conversion process was simulated and analyzed by using CHEMKIN4.1 software.The urea2000 mechanism proposed by Rota et al was mainly supplemented with the related sub-reaction mechanism to simulate the NO conversion process with additives,and the mechanism was simplified and adjusted by means of sensitivity analysis.In the process of ethanol-urea NO removal reaction,many intermediate groups such as NNH,NCO,NH₂ and HO₂ can play a certain role in the removal of NO,but also inevitably produce a little N₂O?NO₂ and other secondary pollutants.