【作者】 任晓莉；

【导师】 张卫江；

【作者基本信息】 天津大学 ， 化学工程， 2006， 博士

【摘要】 在化学工业中,硝酸厂、草酸厂、硝胺厂、炸药厂等一些生产和应用硝酸的企业排放的工艺尾气中含有大量的氮氧化物废气,这些氮氧化物废气的排放,不仅造成了资源的浪费,而且对人类和生态环境具有极大的危害,因此,从我国的国情出发,充分考虑企业的经济效益和社会效益,对常压湿法治理化学工业中的氮氧化物废气进行研究具有重要的理论和现实意义。氮氧化物可以与水反应生成硝酸,回收的硝酸可以返回生产车间继续使用,是符合绿色化工理念的氮氧化物废气治理技术,但是至今为止,用稀硝酸吸收氮氧化物废气回收硝酸的吸收过程的设计尚缺乏理论依据,为此,本文根据双膜理论,采用传质速率法,通过对氮氧化物废气吸收过程进行分析,建立了适合于氮氧化物废气治理的吸收模型,并对模型进行了实验验证,模拟结果和实验结果吻合良好,为氮氧化物废气回收硝酸的吸收设计提供了重要的理论依据。针对目前化学工业中普遍采用的碱液吸收氮氧化物废气的方法存在吸收效率较低、需要改进工艺条件的问题,本文在填料塔内对碱液吸收氮氧化物废气的工艺条件进行了比较系统的实验研究,结果表明当碱度为20～40g/L,喷淋密度为12m~3/(m~2·h),氧化度为50%时,吸收效果最好。本文以硝酸溶液、双氧水溶液和高锰酸钾溶液为氧化剂进行了湿法氧化碱吸收研究,结果表明,以高锰酸钾作氧化剂吸收效果最好,吸收率可以达到99%以上。本文对尿素溶液吸收氮氧化物废气的工艺条件进行了实验研究,得出适宜的操作条件如下:尿素溶液浓度为10%、pH值为1～3、温度为30℃、停留时间为10s。针对尿素溶液对氮氧化物废气中的一氧化氮气体脱除效果不理想的情况,本文提出在尿素溶液中添加双氧水溶液以提高氮氧化物的吸收效果,并进行了实验研究,结果表明,添加双氧水溶液的尿素溶液与仅用双氧水溶液或者仅用尿素溶液吸收氮氧化物废气的实验结果相比较,能够显著增强氮氧化物的吸收率。本文提出了碱液吸收塔+硫酸亚铁吸收塔、碱液吸收塔+活性炭吸附塔、以及硝酸溶液吸收塔+尿素溶液吸收塔两级联合治理氮氧化物废气的方法,并进行了对比研究,结果表明,碱液吸收塔+活性炭吸附塔对氮氧化物的吸收效果最好,优于其它三种方法,对于氮氧化物进口质量浓度为7000～10000mg/m~3的氮氧化物气体,氮氧化物吸收率可以达到99%以上,出口浓度低于100mg/m~3。更多还原

【Abstract】 In chemical industry, NOX gases are largely let off from nitric acid plants, oxalic acid plants, nitro amine plants, dynamite plants and other plants which manufacture or apply nitric acid, which not only waste useful resource, but also represents a serious hazard for the human being and ecosystem. As a result, considering social and economical benefit of the plants, studies on the treatment of nitrogen oxides by wet process at normal pressure appears to be an increasingly important theoretical and practical significance for the prevention of environmental pollutants.Nitrogen oxides can form nitric acid by absorption into water; reclaimed nitric acid can be used again by production shop, so nitrogen oxides absorption into water is the treatment technology which belongs to clean chemistry. But up to now, there is little theoretical guidance except for nitric acid manufacture model. Therefore, based on two-film theory, through the analysis of the absorption process, the mathematical model for nitrogen oxides from exhaust gases into nitric acid solution was established by the method of mass transfer velocity. Experimental validation showed that simulation results were consistent with experimental results. The model provides theoretical basis for absorption process design.In order to improve nitrogen oxides absorption effect, removal of nitrogen oxides with alkaline solutions in packed column was studied, the influence of absorbing agent concentration, spraying density, temperature, oxidativity on nitrogen oxides absorptivity were studied. The results showed that the optimum operating conditions were as follows: alkaline concentration 20~40g/L, spraying density 10~12m3/(m2·h), oxidativity of Nitrogen oxides 50%. The results provide credible parameters for improving absorptivity of nitrogen oxides. In addition, taking HNO3, H2O2 and KMnO4 as the oxidants, the method of oxidation-alkaline solutions absorption were investigated in this paper, the results showed that the absorptivity of NOX could enhance remarkably by using oxidants, and KMnO4 was the best of three oxidants, the absorptivity of nitrogen oxides can reach to 99%.The operational conditions of nitrogen oxides absorption into urea solutions were studied, the results showed that the optimum operational conditions were as follows: the concentration of urea solutions 10%, pH value 1～3, temperature 30℃, reaction time 10s. In order to enhance the effect of nitrogen oxides absorption, hydrogen更多还原