CaO对褐煤和无烟煤热解产物分布及煤焦结构的影响

Effect of calcium oxide on pyrolysis products distribution and char structure of lignite and anthracite

为研究CaO对不同变质程度煤在催化热解过程中的作用规律,以锡林郭勒褐煤和宁夏石嘴山无烟煤为研究对象,利用实验室小型固定床反应器,研究了CaO对褐煤和无烟煤热解特性及煤焦结构的影响,运用X射线衍射(XRD)及傅里叶红外光谱(FT-IR)对比研究了不同温度下褐煤、无烟煤添加CaO前后热解半焦微晶结构以及脂肪结构、芳构化、富氧程度等红外结构参数的变化规律。试验结果表明:在900℃时,添加质量分数2%Ca O的褐煤煤样H2累积产率最大,达39.11 m L/g;添加CaO后煤样在高温热解阶段生成CO的累积产率大于未添加CaO煤样的量。与加入CaO相比,温度对芳香层片间距和芳香层片直径影响更大;热解温度为900℃时,随着CaO的加入,褐煤半焦芳香层片堆积高度和晶层数逐渐增大;而对于无烟煤半焦来说,则与之相反;加入CaO的褐煤和无烟煤热解半焦的微晶结构偏离石墨化程度大于未加入Ca O的热解半焦。褐煤半焦的脂肪结构、芳构化、富氧程度等红外结构参数普遍高于无烟煤半焦。高温时,缩合反应程度增大,CaO促进半焦的转化率提高,导致芳构化参数变大;原煤中C O基团很少,高温下通过CaO促进芳环裂解和CO2反应生成C=O基团,进而导致半焦中富氧程度呈升高趋势。

In order to explore the effect of calcium oxide on the catalytic pyrolysis characteristics of different rank coals,the changes of the pyrolysis products distribution and the char structure were analyzed based on Inner Mongolia Xilinguole lignite and Ningxia Shizuishan anthracite were carried out with a fixed bed reactor. By means of X-ray diffraction（ XRD） and Fourier transform infrared spectroscopy（ FTIR）,the variance of microcrystalline structure,aliphatic structure,aromatization and oxygen-enriched efficiency of char prepared by pyrolysis of lignite and anthracite under different temperatures before and after addition of calcium oxide were investigated. The research results showed that the H2 cumulative yield of 2%CaO added in ingnite at 900 ℃ was the largest,reaching 39. 11 m L / g. The CO cumulative yield of coal sample with calcium oxide was greater than that of without calcium oxide in high temperature pyrolysis stage. Compared with the addition of calcium oxide,the temperature had a greater influence on the aromatic layer spacing and the diameter of the aromatic layer. The value of lignite char aromatic layer stack height and the layer number increased gradually with the adding of calcium oxide at 900 ℃,but anthracite char was on the contrary. The structural deviation degree of graphitization of the microcrystalline structure of char prepared by pyrolysis of lignite and anthracite with the addition of calcium oxide was higher than that of the char without the addition of calcium oxide. The aliphatic structure,aromatization and oxygen-enriched efficiency infrared structure parameters of lignite char was generally higher than that of anthracite char. At high temperature,the degree of the condensation reaction was increased,and the conversion rate of the char was enhanced with the addition of CaO,which led to the aromatization parameters increased. The CO groups content in raw coal was rare,and the C=O groups was generated through reaction between the calcium oxide promoted aromatic ring cracking under high temperature and CO2,which led to oxygen-enriched efficiency in char increased gradually.