| In recent years,the emission of atmospheric pollutant has gradually become a global environmental problem.Especially the emission of NO X has multiple hazards.It can lead to the formation of acid rain and photochemical smog,damage the vegetation and buildings,acidify the rivers and lakes and other water,and even endanger human health.Many studies on the treatment of atmospheric pollutants showed that non-thermal plasma is an efficient method for NOX removal.non-thermal plasma can realize the treatment of various pollutants si multaneously at atmospheric pressure.Furthermore,the investment cost and operation cost are relatively low.Due to the above reasons,this technology has attracted the attention of scholars both at home and abroad.This paper introduced the basic theory and chemical process of strong ionization discharge.According to the above theories,relevant chemical reaction equations of NO removal was selected.With N2 as carrier gas,the chemical reaction kinetics models of two kinds of simulated flue gas system,including NO/N2/O2 system and NO/N2/O2/H2 O system were established,based on different flue gas composition.And then MATLAB was used to write programs to conduct numerical simulation.By adjusting the concentration of the key material in the flue gas system,the micro physical and chemical reaction process in the plasma and the effects of the various factors on the removal of NO by strong ionization discharge under different flue gas systems were investigated in this paper.The main transformation and removal path of NO in the above two flue gas systems were pointed out.In addition,the effects of NO initial concentration,water content,oxygen content,discharge voltage and frequency on the recycling removal of NO by strong ionization discharge were resea rched through some tests.The methods to improve the removal efficiency of NO were concluded and the components of NO removal products were analyzed.The main results of this paper are as follows:?1?For the simulated flue gas system NO/N2/O2,the influence of reaction rate constants on NO removal,the influence of oxygen content on the generation of key free radicals during the process of NO removal and the influence of these free radicals on the removal of NO were investigated.The change of the concentration of nitrogen oxides in the process of NO removal in the simulated flue gas system was also investigated.The simulation results showed that,the effects of different reaction rate constants on the removal of NO were different.Improving the reaction rate constant k4 and reducing the reaction rate constant k6,k7 and k18 can promote the recycling removal of NO.Therefore,the appropriate methods should be selected to improve k4 and reduce k6,k7 and k18 during the experiment.When the simulation time was between 0 second and 50×10-6 seconds,the generation number of O free radical increased with the increase of oxygen content,while the generation number of N free radical decreased.During the simulation time 050×10-6 seconds,with the decreased particle number concentration of NO,particle number concentration of N 2O remained almost constant and generate little,particle number concentration of NO 2 and NO3 correspondingly increased.Furthermore,the particle number concentration of NO 3 increased obviously.?2?For the simulated flue gas system NO/N2/O2/H2 O,the influence of water content on the formation of O,H and OH radicals and the influence of water content on the removal of NO were mainly investigated.Also the products of NO removal in aqueous system were inspected.The simulation results are as follows: When the simulation time was between 0 second and 50×10-6 seconds,with the increase of water content,the generation of O free radicals declined while the amount of H and OH radicals increased and it is conducive to the oxidative removal of NO.The addition of water vapor in the reaction system has significantly improved on the removal efficiency of NO.Compared to the reaction system without water.Under the condition of adding water vapor,NO was finally oxidized into HNO3,which was green,pollution-free and recyclable.?3?Corresponding NO recycling removal tests were conducted through a set of test device,which was by strong ionization discharge.The influence factors such as the initial concentration of NO,moisture content,oxygen content,discharge voltage and frequency were mainly studied.All these tests were conducted under the total flow rate of simulated flue gas were 4L/min and temperature were 30?.Test results are as follows:?a?When the oxygen content was 15%,the moisture content was 14% in the aqueous system,the rest of gas was N2,the discharge voltage was 1.6kV and discharge frequency was 4.8 kHz,with the increase of initial NO concentration,NO removal rate decreased.When the initial concentration of NO in water-contained gas system was 250 ppm,the removal rate of NO was up to 87.1%;?b?When the initial concentration of NO was about 250 ppm,the rest of gas was N2,the discharge voltage was 1.6kV and discharge frequency was 4.8 kHz,the NO removal efficiency increased with the increase of water cut under the condition that the oxygen content was 15% and the NO removal efficiency increased with increasing oxygen content under the condition that the moisture content was 14%;?c?When the oxygen content was 15%,the moisture content is 14% in the aqueous system and the rest of gas was N2,the NO removal efficiency increased firstly and then decreased with the increase of the discharge voltage under the condition that the discharge frequency was 4.8 kHz.When the discharge voltage was lower than 2.4kV,the NO removal efficiency increased with the increase of discharge voltage.When the discharge voltage is higher than 2.4kV,the NO removal efficiency began to decline.However,the effect of discharge frequency on NO removal is weak and the removal efficiency of NO increased slowly with the increase of frequency.?d?The product of NO removal was analyzed by ion chromatography.The results showed that the product of NO removal was HNO3.The strong ionization discharge method studied in this paper is rather effective for the treatment of NO with low concentration.From the study,it can be concluded that by increasing the water content and oxygen content,controlling the discharge voltage and frequency in a reasonable range which can improve the removal efficiency of NO.The product test results showed that the final product of NO removal by strong ionization discharge was HNO3,so the path of NO removal was oxidation.The results of this study can provide an important theoretical basis and experimental reference for the engineering application of NO removal by strong ionization discharge method. |
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