烟气脱硝过程中金属氧化物对半焦低温氧化特性的影响

发布时间：2018-02-15 10:44

本文关键词： 低温催化氧化半焦反应机制碳氧复合物　出处：《辽宁科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：煤炭是我国的主要能源,在煤炭利用过程中排放的NOX所引起的大气污染问题,严重的影响着大气环境和人类生活健康。为了缓解大气污染的严重程度,各国政府纷纷通过立法来控制NOX的排放量。由于活性半焦具有吸附效率高、价格低廉等特点,且半焦与NO的还原反应在脱硝过程中十分重要,因而活性半焦脱硝剂备受国内外学者的青睐。烟气中一般含有5%左右的O_2,这会提高活性半焦脱硝剂的脱硝效率。但同时多余的O_2会与活性半焦载体中的碳反应,造成载体的消耗,这种现象严重制约着半焦脱硝剂脱除烟气中NO的效率,提高烟气处理的成本。因此,研究半焦低温催化氧化特性有助于在实际应用中控制半焦载体的损耗。针对目前对半焦低温催化氧化反应机理的认识尚有不足之处,本论文采用超声波浸渍法使褐煤负载金属氧化物并制备成活性半焦。在模拟气氛下,利用固定床反应器,系统的研究了氧化温度、植入金属含量及金属种类、及其他气氛对半焦低温催化氧化特性的影响。利用傅立叶红外仪(FTIR)分析氧化前后半焦表面含氧官能团的变化;利用X射线衍射仪(XRD)分析氧化前后半焦中金属氧化物的晶体结构变化;利用电子显微镜(SEM)分析半焦表面的形貌结构。探讨了在半焦低温氧化过程中的低温氧化机制和金属氧化物的催化机制。实验结果表明:氧化温度的升高会促进半焦的氧化反应及金属氧化物的催化作用。氧化温度越高,半焦的氧化反应程度越剧烈,金属氧化物的催化作用越明显。在半焦中植入的金属含量及金属种类不同,金属氧化物的催化机制有所不同。F5催化剂较F10催化剂催化半焦氧化反应向氧化程度深的方向进行。Fe基氧化物催化半焦氧化反应生成CO,而Cu基氧化物催化半焦氧化反应生成CO_2。烟气中存在的CO_2气体对半焦低温氧化反应有一定的抑制作用。而NO对半焦氧化反应生成CO有促进作用,且CO参与脱硝过程,与NO反应生成CO_2和N_2。
[Abstract]:Coal is the main energy in our country. The air pollution caused by NOX emission in the process of coal utilization seriously affects the atmospheric environment and the health of human life. The governments of various countries have adopted legislation to control the emission of NOX. Because active char has the characteristics of high adsorption efficiency and low price, the reduction reaction between char and no is very important in denitrification process. Therefore, active semi-coke denitrification agent is favored by scholars at home and abroad. There is generally about 5% O _ 2 in flue gas, which will improve the denitrification efficiency of active semi-coke denitration agent. But at the same time, the excess O _ p _ 2 will react with carbon in active semi-coke carrier. This phenomenon seriously restricts the efficiency of no removal from flue gas by semi-coke denitration agent and increases the cost of flue gas treatment. To study the characteristics of char catalytic oxidation at low temperature is helpful to control the loss of char carrier in practical application. In this paper, activated semi-coke was prepared by impregnating lignite with metal oxide by ultrasonic impregnation. In a fixed bed reactor, oxidation temperature, metal content and metal species were systematically studied in a fixed bed reactor. FTIR was used to analyze the changes of oxygen-containing functional groups on the surface of semi-coke before and after oxidation. X-ray diffractometer (XRD) was used to analyze the crystal structure changes of metal oxides in semi-coke before and after oxidation. The morphology and structure of semi-coke surface were analyzed by electron microscopy (SEM). The mechanism of low-temperature oxidation and the catalytic mechanism of metal oxide were discussed. The experimental results showed that the increase of oxidation temperature would promote the semi-char. Oxidation of coke and catalysis of metal oxides. The higher the oxidation temperature, The more intense the oxidation reaction of the char, the more obvious the catalytic action of the metal oxide. The metal content and the metal type implanted in the char are different. The catalytic mechanism of metal oxides is different. F5 catalyst is better than F10 catalyst in the direction of oxidation degree of semicoke. Fe-based oxide catalyzes semicoke oxidation to produce CO.Cu-based oxide catalyzes semicoke oxidation. The CO_2 gas in flue gas can inhibit the oxidation of char at low temperature, while no can promote the oxidation of char to CO. Co was involved in the denitrification process and reacted with no to produce CO_2 and N2s.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701;O643.36

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