【作者】 杨剑；

【导师】 刘清才； 董凌燕；

【作者基本信息】 重庆大学 ， 冶金工程， 2008， 博士

【摘要】 我国电力生产以燃煤发电为主,由于中国煤炭资源的特点是高灰分、高硫,因此近年来燃煤电厂SO2的污染问题日益突出。烟气脱硫是控制燃煤电厂SO2排放的有效方法。湿式石灰石-石膏烟气脱硫工艺是当今燃煤电厂应用最为广泛的烟气脱硫技术。在该工艺中,亚硫酸氢钙的氧化程度关系到烟气中硫分的最终脱除程度,因此,开展烟气脱硫氧化过程的研究,对优化脱硫系统设计、提高脱硫效率、保证脱硫装置稳定可靠运行和降低运行成本具有重要作用。本文以相似原理为基础,对烟气脱硫氧化实验模拟装置进行了设计研究。针对典型300 MW级烟气脱硫装置,采用10:1的缩放比例,独创的圆盘式空气喷吹方式,使空气在浆液中的布置更加均匀。经CFD模拟及实验验证表明,该氧化模拟装置搅拌均匀、传质性能较好,能应用于烟气脱硫氧化过程的实验研究。利用建立的氧化模拟装置进行了亚硫酸盐的非催化氧化研究。结果表明,非催化氧化的适宜条件为:亚硫酸钙初始浓度0.01 mol·L^-1、浆液pH值为3.5、浆液初始温度为55℃、氧分压60.8 kPa、搅拌转速6 r·s^-1。在实验条件范围内,非催化氧化过程对HSO₃^-的反应级数为1,溶解氧级数为0,非催化氧化活化能为71.43kJ·mol^-1。该过程的速率控制步骤为HSO₃^-的二级电离。研究了Mn²⁺、Fe²⁺催化剂对亚硫酸氢钙氧化过程的催化作用。锰催化动力学实验表明,氧化反应对锰离子为0.5级响应,对亚硫酸氢盐为1级响应,对溶解氧为0级响应,锰催化氧化反应的活化能为40.72 kJ·mol^-1,该反应的速率控制步骤为锰离子引发SO₃^2-*基团的过程。铁催化动力学实验表明,氧化反应对铁离子为0.5级响应,对亚硫酸氢盐为1级响应,对溶解氧为0级响应,铁催化氧化反应的活化能为54.52 kJ·mol^-1,该反应的速率控制步骤为铁离子引发SO₃^2-*基团的过程,该机理与锰催化氧化反应机理基本相同,说明两种催化剂的催化效果相似。首次对Mn²⁺和Fe²⁺联合催化氧化过程进行了系统研究。在实验条件范围内,锰铁联合催化氧化反应对锰离子为0.25级响应,对铁离子为0.25级响应,对亚硫酸氢盐为1级响应,对溶解氧为0级响应,锰铁联合催化氧化反应的活化能为43.73 kJ·mol^-1。锰铁联合催化氧化反应的速率控制步骤为锰离子和铁离子分别引发SO₃^2-*基团的过程,符合平行反应机理。建立了烟气脱硫氧化过程的动力学模型,其主要表达式为:该模型能较好地对氧化过程进行分析和描述。计算结果表明,非催化氧化反应、锰催化氧化反应、铁催化氧化反应和锰铁联合催化氧化反应的活化能分别为73.08kJ·mol^-1、42.11kJ·mol^-1、53.85kJ·mol^-1、44.80kJ·mol^-1,该计算结果与氧化动力学实验得到的实验值相对误差分别为2.32 %、3.40 %、1.22 %、2.46%。对石膏结晶过程研究结果表明,浆液中杂质的存在能引起晶体形态的改变,搅拌转速的改变也能引起晶体形态的改变,一方面是由于搅拌转速降低会导致亚硫酸氢钙的氧化效率下降,从而使溶液中硫酸钙的浓度降低,引起石膏结晶的推动力降低;另一方面,较低的搅拌转速使池中的浆液不能较好地混合,导致浆液池中各部分浓度不均匀,从而改变了各晶面的相对生长速度,明显地引起晶体形态的改变。本文的主要创新点:①针对典型300 MW烟气脱硫机组,建立了浆液池氧化模拟装置,首次进行了锰铁联合催化氧化亚硫酸氢钙研究。②系统研究了Mn²⁺和Fe²⁺两种催化剂对亚硫酸氢钙氧化过程的催化作用,首次获得了催化氧化反应的速率控制步骤为Mn²⁺引发SO₃^2-*基团的过程。③建立了烟气脱硫氧化过程动力学模型,其主要表达式为:更多还原

【Abstract】 The power generation in China is mostly generated by coal-fired plant. As the coals resources containing high quantity of ash and sulfur, the pollution of sulfur dioxide, which produced by coal-fired power plant, becomes severe nowadays. The flue gas desulfurization （FGD） is an effective way to control the emitted sulfur dioxide. The wet FGD process is the most extensively used technology for desulfurization. In that technology, the oxidation ratio of calcium bisulfite determines the removal ratio of SO₂ in the flue gas. So the study of oxidation is of significance.Aim at the typical 300 MW FGD absorber, the simulant device has been set up, based on similarity principle. The similarity ratio of the device was set to 10:1. So its inside diameter was 1.2 m and height was 1.2 m. The device also has been equipped with a dial type air jet to make air uniformity in the slurry. The results of simulations and experiments indicated that, the simulant device is of preferable mass transfer performance. So the device could be used in the experimental research of the oxidation process.The uncatalyzed oxidation experiments have been executed in the simulant device. The bisulfite was obtained by the reaction of analytic calcium oxide, distilled water and sulfur dioxide. The optimal experimental conditions, have been gained by orthogonal experiments, which the bisulfite concentration was 0.01 mol·L^-1, the pH was 3.5, the temperature of slurry was 55℃, the oxygen partial pressure was 60.8 kPa and the stir speed was 0.01 mol·L^-1. The uncatalyzed oxidation experimental results indicated that the reaction order of bisulfite was 1, the reaction order of dissolved oxygen was 0 and the activation energy was 71.43kJ·mol^-1. The rate determine step of uncatalyzed oxidation was the secondary ionization of bisulfite.The oxidation process which was catalyzed by manganese or ferrous ion has been researched. The manganese catalyzed experiments indicated that, the reaction order of manganese ion was 0.5, the bisulfite was 1 and the dissolved oxygen was 0. The activation energy was 40.72 kJ·mol^-1. The rate determine step of manganese catalyzed oxidation was the generation of free radical initiated by manganese ion. The ferrous catalyzed experiments indicated that, the reaction order of ferrous ion was 0.5, the bisulfite was 1 and the dissolved oxygen was 0. The activation energy was 54.52 kJ·mol^-1. The rate determine step of ferrous catalyzed oxidation was the generation of free radical initiated by ferrous ion.The catalyzed oxidation experiments have been executed first time when manganese and ferrous ion existed simultaneously. The manganese-ferrous catalyzed experiments indicated that, the reaction order of manganese ion was 0.25, the ferrous ion was 0.25, the bisulfite was 1 and the dissolved oxygen was 0. The activation energy was 43.73 kJ·mol^-1. The rate determine step of manganese-ferrous catalyzed oxidation was the generation of free radical initiated by manganese ion and ferrous ion. It agreed the parallel reaction mechanism.The dynamic model of oxidation process has been established, based on the experimental results. The main expression was as follows:The calculation results indicated that the model could preferably explain the oxidation process. The results also indicated that, the activation energy of uncatalyzed oxidation, manganese catalyzed oxidation, ferrous catalyzed oxidation and manganese-ferrous catalyzed oxidation were 73.08kJ·mol^-1, 42.11kJ·mol^-1, 53.85kJ·mol^-1 and 44.80kJ·mol^-1 respectively. The relative errors between these calculation results and the experimental results were 2.32 %, 3.40 %, 1.22 % and 2.46% respectively.The crystallization process of desulfurization gypsum has been researched experimentally. The results indicated that, the optimal residence time was eight hours. Besides, the impurities could change the crystal form, which might be related to the crystal plane absorbing the impurities. The last, the stir speed could change the crystal form. That was because descending the stir speed could reduce the calcium bisulfate concentration in one hand, in another hand the low stir speed could make the grow speed of crystal plane differently.The originality innovations of the thesis are as follows. （1） The simulant device has been set up aim at the typical 300 MW FGD absorber. Based on the device, the catalyzed oxidation experiments have been executed first time when manganese and ferrous ion existed simultaneously. （2） The oxidation process which was catalyzed by manganese or ferrous ion has been systemically researched. The rate determine step of manganese catalyzed oxidation has been obtained the first time, which was the generation of free radical initiated by manganese ion or ferrous ion. （3） The dynamics model of oxidation process has been established. The main expression of it was as follows:更多还原