【作者】 林赫；

【导师】 岑可法； 倪明江； 骆仲泱；

【作者基本信息】 浙江大学 ， 工程热物理， 2002， 博士

【摘要】 本文首先评述了各种烟气脱硝技术，并阐述了电晕放电脱除烟气中NO_x的研究成果以及对放电机理的研究状况。 研究了以NH₃为自由基源物质的烟气脱硝过程。研究表明，烟气湿度对放电的发展起抑制作用，但适当的烟气湿度对提高氮氧化物脱除效率有促进作用，烟气含湿量在10％左右时，单位能量脱除的氮氧化物量最多，是脉冲电晕法的两倍。烟气温度对放电过程影响不明显，但是，烟气温度提高对氮氧化物的脱除不利。烟气流量对放电过程影响较小。氮氧化物脱除率随流量增加而降低，但是提高烟气流量可以提高能量的利用率，烟气在反应器内的停留时间为5～7.5s比较合适，通过进一步延长停留时间来达到进一步提高脱除率是不经济的。烟气中氮氧化物浓度的增加会降低脱除效率，但能量的利用效率会相应提高。减小电极间距将降低起晕电压和击穿电压，加大极间距有利于获得更高的放电功率。 用O₂+H₂O混合气体簇射结合碱液化学吸收，对烟气中氮氧化物的脱除进行了研究。如果水蒸气体积百分比适量，可以产生稳定的流光电晕。在反应器内，NO主要有两条转化途径，一是被氧化成NO₂，后又与OH自由基反应生成HNO₃，另一途径是与OH自由基反应，生成HNO₂。反应器内的主要反应产物为HNO₃，最高DeNO_x效率达70％以上。增加电极中氧气的湿度可提高反应器内的DeNO_x效率。NaOH溶液对NO的吸收率小于30％，而对NO₂的吸收率在90％以上。经过NaOH溶液吸收后，烟气总DeNO_x效率最高可达90％。Ca（OH）₂溶液对NO₂的吸收比较充分，因此，以传统湿法（半干法）烟气脱硫系统作为电晕放电氧化氮氧化物所产生的氧化产物的吸收系统是可行的。 采用模拟电荷法和复变换对静态边缘电场进行了模拟。通过模拟，从理论上证明本文实验方案是可行的，并且得到了静态电场的求解方法，为下一步的工作奠定了基础。在静电场模拟中，还求解出流光电晕放电的临界点，为蒙特卡罗法模拟流光电晕放电提供了基准点。 采用蒙特卡罗法针对本文实验系统进行了流光电晕放电的模拟。模拟结果表明，电子的能量在不同的空间位置分布不同，靠近正极，高能态电子数量有增加的趋势。空间电场因空间电荷的累积而扭曲，在靠近正极附近的区域，电场比拉普拉斯电场强度有所降低，而靠近负极处，电场强度相应增强。由于电场扭曲，流光电晕呈脉冲形式出现，电流也呈脉冲形式。 初步计算了自由基簇射过程中各种自由基的单位能量产率。计算结果证明，在自由基簇射系统中，烟气中N₂的分解率较小，而O₂和H₂O分解率相对较高。 计算了NO_x在反应器内的氧化效率，理论与实验值基本吻合。计算了功率浙江大学博士学位论文为2.5w时不同烟气流速条件下的NO:脱除效率，发现在一定的功率条件下，烟气停留时间增加使脱除率提高，但是，降低了能量利用效率。 预测了当喷嘴气体湿度变化时，反应器内NO、氧化效率的变化，发现当喷嘴气体含湿量为9%时，NO:氧化效率最高达90%以上。 结合传统湿法脱硫脱硝技术，提出了电晕氧化结合传统湿法同时脱除烟气中二氧化硫和氮氧化物的工艺流程。更多还原

【Abstract】 The thesis reviewed every kind of flue-gas DeNOx technologies firstly, and introduced both the research results of removal of the NOX from flue-gas with corona discharge technologies and the research work on discharge mechanism.The experiments on removal of NOX from the flue-gas using NH3 as radical resource were carried out. The results showed that water vapor restrains the discharge process, but proper content of water vapor in flue-gas will improve the removal efficiency, the quantity of NOX that removed by unit energy from the flue-gas that contained 10% of water vapor is the highest, and double that of pulsed corona technologies. The temperature of flue-gas affected on the discharge process a little, but high temperature would reduce the removal efficiency of NOX. The flow rate of flue-gas impacted on the discharge faintly. The higher the flow rate of flue-gas is, the higher energy efficiency would be obtained. It is moderate that the flue-gas residues in the reactor for 5-7 seconds. To improve the removal efficiency by the way of lengthening residence time of flue-gas in the reactor is not economical. The removal efficiency would be reduced if the concentration of the NOX increased, the energy efficiency enhanced on the other hand. The shorter distance between the anode and the cathode would result in both lower started corona voltage and lower breakdown voltage. Long distance is beneficial to obtaining high discharge power.Removal of NOX from flue-gas by H2O+O2 radical injecting integrating with alkali solution scrubbing is carried out. The steady streamer corona occurred when the water vapor feed into the nozzle electrodes was moderate. Some of the NO will convert into NO2 in the reactor. The NO2 react with OH radicals and convert into HNO3 at the end. The rest of NO in the reactor converts into HNO3 after reacting with OH radicals. Most of the reaction production in the reactor is HNO3. The highest DeNOx efficiency is above 70%. To increase the humidity of the oxygen that feed into the nozzles will improve the DeNOx efficiency. The NO absorbed by NaOH solution was little than 30%, the percent of NO, absorbed by NaOH solution was more than 90%. The overall DeNOx efficiency approached 90% after the flue gas absorbed by NaOH solution and the Ca(OH)2 solution absorbed the NO2 well also. This indicated that to remove the NOX, which is the production of corona discharge, by wet desulfurization system is feasible.The electrostatic field of the nozzle brim was simulated with simulation-charge technique and complex transformation. The experiment project was proved to befeasible by simulation process. The solution of electrostatic field was approached and this is the foundation of the subsequent research. The critical position, which was the start position of the Monte Carlo simulation of steamer corona discharge, was solved too.The streamer corona discharge in the experiment system was simulated with Monte Carlo simulation. The simulation result showed that the electron energy distribution of different positions is different. The quantity of higher-energy electrons near the anode is much more than other positions. The space electric field is distorted because of the charges accumulation. The electric field near the anode is lower than Laplace electric field, and the electric field near the cathode is higher than Laplace electric field. The streamer corona appears as pulse because of the distorted electric field, and the discharge current appears as pulse too.The unit energy yield of every kind of radicals in the radical injecting process was computed. The dissociated probability of the N2 in the flue-gas is low, but the dissociated probabilities of O2 and H2O are high comparatively.The oxidizing efficiency of NOx in reactor was forecasted, and the computed results are accordant with the experiment results. The removal efficiency of NOx was computed in different velocity flue-gas at a constant power of 5 watt. It was founded that the removal efficiency of NOX increases with the residues ti更多还原