【作者】 孟丽莉；

【导师】 常丽萍；

【作者基本信息】 太原理工大学 ， 化学工艺， 2011， 硕士

【摘要】 褐煤在我国储量丰富,但因自身所具有的高水分、高挥发分、低热值等特性而使其品质降低、难以利用,对其进行热解提质显得尤为重要,在热解提质过程中煤中硫、氮的迁移变化也必须给予重视。基于此,本文以内蒙古锡盟高硫褐煤为研究对象,首先进行HCl/HF混酸脱除煤中固有的矿物质,然后分别将碱金属、碱土金属和过渡金属负载于原煤和脱矿物质煤中制得实验用脱矿物质和负载添加物的煤样,采用固定床程序升温热解-色谱法考察了煤中固有矿物质及添加物对锡盟褐煤热解过程中硫、氮气相产物的影响,主要实验研究结果如下：1)煤中固有矿物质对硫、氮变迁的影响酸处理脱矿物质煤样热解形成的含硫气体释放量明显高于原煤,表明煤中固有矿物质具有固硫作用,且该作用主要出现在500-800℃的温区内；脱矿物质煤的H2S和COS最大释放峰值温度不变显示了煤中矿物质的脱除没有改变有机体及硫化物的存在形态。矿物质对含氮气体总释放量的影响与硫一样也具有抑制作用,但改变了HCN和NH3的释放量随温度的变化趋势,固有矿物质在550-750℃范围内具有催化HCN转化为NH3的作用。2)负载于原煤及脱矿物质煤中的碱金属对硫、氮变迁的影响除负载于原煤的碳酸钾,所有负载的碱金属碳酸盐在煤热解过程中均具有一定的固硫作用,抑制了含硫气体的释放。碳酸钾在200-500℃的温度范围内对原煤热解过程中含硫气体的释放具有显著的促进作用,显示了在此温区存在着碳溶反应的催化作用。碱金属碳酸盐促进了原煤热解过程中含氮气体的释放,特别是碳酸钾的促进作用最明显；脱矿物质煤中负载的碱金属碳酸盐对总的含氮气体的释放存在一定的抑制作用,主要表现在对HCN释放的抑制,碳酸钾和碳酸锂促进了脱矿物质煤中NH3的生成,显示了HCN催化转化为NH3的二次反应的存在。3)负载于原煤及脱矿物质煤中的碱土金属对硫、氮变迁的影响无论是乙酸钙,还是草酸钙,对锡盟原煤和脱矿物质煤热解过程中含硫气体的释放都具有一定的抑制作用,主要是由于钙基添加物的固硫作用所致。对于含氮气体的释放,原煤中负载钙基添加物促进了NH3的生成,抑制了HCN的生成；脱矿物质煤中负载钙基添加物对含氮气体的释放抑制作用更为明显,显示了添加物与煤中固有矿物质的协同作用促进了煤中含氮基团的裂解和HCN催化转化为NH3的二次反应。4)负载于原煤及脱矿物质煤中的过渡金属对硫、氮变迁的影响乙酸铁和草酸铁的加入对原煤和脱矿物质煤热解过程中含硫气体的释放具有强于钙基添加物的抑制作用。对于含氮气体的影响,乙酸铁和草酸铁的作用不同,加入乙酸铁的原煤或脱矿物质煤热解过程中生成HCN和NH3的量均明显高于草酸铁,乙酸铁具有较强的促进含氮基团向NH3转化的能力,而草酸铁对HCN和NH3的形成却表现为抑制作用。5)煤中固有矿物质和添加物对硫、氮释放的相互作用对比原煤负载样和脱矿物质煤负载样热解过程中硫、氮释放的影响,发现原煤负载添加物对含硫气体释放的抑制作用大于脱矿物质煤,主要是由于原煤中固有矿物质与添加物共同作用所致；与含硫气体的影响相反,原煤负载添加物含氮气体的释放量高于脱矿物质煤,这主要是原煤中固有的矿物质和添加物的协同作用引起热稳定性相对较高的含氮官能团继续裂解所致。更多还原

【Abstract】 Brown coal resource is rich in China, but the features of high moisture, high volatile and low heat-value limit markedly its utilization range. So it is very important to improve the quality of brown coal through pyrolysis technique. Sulfur and nitrogen in the coal will partly release in the form of gasous products during the coal pyrolysis, which will cause environmental pollution. It is necessary to research the release of sulfur and nitrogen during coal pyrolysis. The brown coal from Ximeng mine in Inner Mongolia was used as the experimental sample. The salts of alkali metal, alkaline earth metal and transition metal were evenly mixed with raw coal and demineralized coal (the inherent mineral was removed by acid-washing). The effect of the minerals and additives added in raw coal and demineralized coal on the formation of S-containing gases and N-containing gases during temperature programmed pyrolysis was studied by the fixed-bed experimental setting. The gaseous products from coal pyrolysis were analyzed by gas chromatography and IC chromatography. The main results are shown as following: 1) The effect of inherent minerals on the release of sulfur and nitrogen during coal pyrolysisThe S-containing gases from the pyrolysis of demineralized coal are obviously higher than that of raw coal, which shows the inherent minerals in Ximeng brown coal have the desulfurization capacity and can restrain the formation and release of S-containing gases during pyrolysis. This action mainly presents the temperature range of 500-800℃. The same maximum peak temperature of H2S and COS from pyrolysis of demineralized coal and raw coal shows that the removing of minerals does not affect the sulfur and organic matrix in coal. The release amount of total N-containing gases from demineralized coal pyrolysis is also higher than that from raw coal pyrolysis, but the changes of HCN and NH3 release trend with temperature are different. The inherent minerals present the capacity of promoting HCN to NH3 in the temperature range of 550-750℃.2) The effect of alkali metal loaded in raw coal and demineralized coal on the release of sulfur and nitrogen during coal pyrolysisExcept for K2CO3 added in raw coal, the alkali metals added in raw coal and demineralized coal can prohibit the formation of S-containing gases. The additive of potassium carbonate in raw coal significantly promotes the release of S-containing gases at 300-500℃, which shows the catalysis action by potassium and carbon reaction. Alkali metals added in raw coal promote the release of N-containing gases during pyrolysis, and the role of potassium carbonate is also the most obvious. Alkali metals added in demineralized coal prohibit the release of N-containing gases, especially HCN. The results of Li2CO3 and K2CO3 promoting the release of NH3 show the secondary reaction of HCN conversion to NH3.3) The effect of alkaline earth metal loaded in raw coal and demineralized coal on the release of sulfur and nitrogen during pyrolysisWhether calcium acetate or calcium oxalate added in raw coal and demineralized coal can prohibit the release of S-containing gases during coal pyrolysis because the sulfur from coal pyrolysis can react with calcium in additives and is retained in the char. Calcium added in raw coal promotes the release of NH3 and prohibits the formation of HCN, and it is more apparent when calcium added in demineralized coal. These results show there exists the synergy reaction between inherent mineral and additives, which promotes the cracking of nitrogen group and secondary reaction of HCN conversion to NH3.4) The effect of transition metal loaded in raw coal and demineralized coal on the release of sulfur and nitrogen during coal pyrolysisIron acetate and iron oxalate added in raw coal and demineralized coal have the strong desulfurization capacity during coal pyrolysis, and this effect is bigger than that of calcium-based additives. Iron acetate and iron oxalate play a different role in the release of N-containing gases. The release amounts of NH3 and HCN for iron acetate added in raw coal and demineralized coal are higher than that of iron oxalate. Iron acetate has the strong promoting action on the transformation of nitrogen groups to NH3, but iron oxalate has the inhibition action on the formation of NH3 and HCN.5) The effect of inherent minerals and additives in coal on the release of sulfur and nitrogen during coal pyrolysisComparing the release amounts of sulfur and nitrogen during pyrolysis of raw coal and demineralized coal with additives, it can be found that the inhibition on the S-containing gases release of additives added in raw is more obvious than that in demineralized coal. This should be due to the interaction between inherent minerals and additives in coals. Contrary to the release of S-containing gases, the release amount of N-containing gases from pyrolysis of the raw coal with additives is higher than that of the demineralized coal with additives, this is mainly due to the synergy effect between minerals and additives promoting the relatively thermal stabile nitrogen groups in coal to be cracked.更多还原