碱金属碳酸盐对褐煤程序升温热解过程中H2S和NH3生成的影响

以内蒙古锡盟褐煤为研究对象,通过HCl/HF洗脱煤中固有矿物质,采用机械混合法对原煤和脱矿物质煤分别负载3%的Li₂CO₃、Na₂CO₃和K₂CO₃,利用固定床程序升温热解-色谱分析法考察了煤中固有矿物质以及负载的碱金属碳酸盐对煤热解过程中H₂S和NH₃生成的影响。结果表明,煤中所固有矿物质对锡盟褐煤热解过程中H₂S和NH₃的生成和释放均有抑制作用,但对H₂S和NH₃生成的影响不同;矿物质的脱除不改变煤中有机结构及硫的存在形态,H₂S的释放温区没有发生改变,而HCN的二次反应是NH₃生成的主要来源之一,酸洗脱矿物质改变了煤中孔结构特性,从而影响不同温度段NH₃的释放。原煤及脱矿物质煤负载的碱金属碳酸盐对其热解过程中H₂S和NH₃的生成都有一定的影响,K₂CO₃除外, 负载到原煤的其他碱金属碳酸盐都抑制了H₂S的生成;Na₂CO₃除外,负载到脱矿物质煤的其他碱金属碳酸盐都促进了NH₃的生成。

Effect of alkali carbonates on the formation of H2S and NH3 during temperature programmed pyrolysis of brown coal

Using a brown coal from Ximeng mine in Inner Mongolia as raw sample,3% the carbonates of lithium,sodium or potassium were evenly mixed with raw coal and demineralized coal(the inherent mineral was removed by acid-washing).The effects of the minerals and the alkali carbonates added in raw coal on the formation of H2S and NH3 during temperature programmed pyrolysis was studied by a fixed-bed reactor and gas chromatography.The results show that the inherent mineral in Ximeng brown coal can restrain the formation and release of H2S and NH3 during pyrolysis.The temperature range of maximum H2S release from demineralized coal is same to that of raw coal because the organic structure of coal and the form of sulfur are not changed.But the behavior of NH3 is obviously changed in the different temperature range because the secondary reaction of HCN is also one of main sources for NH3 formation,which is affected by the pore structure change of coal demineralized by acid-washing.The alkali carbonates added have different effects on the formation of NH3 and H2S during pyrolysis.Except for K2CO3,the presence of alkali carbonates can prohibit the formation of H2S.They can promote the formation of NH3,except for Na2CO3 added in demineralized coal.