预氧化对煤比表面积及孔径分布影响的实验研究
Effect of Pre-oxidation on Coal Specific Surface Area and Pore Size Distribution
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摘要: 为探讨煤氧化后煤样的微观物理结构变化特征,采用液氮吸附实验分别对六家褐煤、四台褐煤、同忻烟煤和白芨沟无烟煤进行比表面积和孔隙结构测试,得出煤样比表面积、孔径分布及孔体积等随预氧化温度和预氧化时间的变化规律。结果表明:各煤矿预氧化煤样比表面积值具有相同的变化规律:50 ℃预氧化煤样>原始煤样>120 ℃预氧化煤样>200 ℃预氧化煤样,且预氧化温度一定时,预氧化时间越长,煤样比表面积越小;各煤矿预氧化煤样孔径均集中分布于2~10 nm范围内,煤样50-6(在50 ℃下预氧化6 h)具有最高的累计孔体积终值,而煤样200-24(在200 ℃下预氧化24 h)累计孔体积终值最低;煤样50-6内部孔隙网络最为发达,同条件下更易与氧气结合发生煤氧复合反应,自燃危险性最高,煤样200-24则相反,自燃危险性最低。Abstract: In order to explore the micro structure variation features of coal after pre-oxidation, the liquid nitrogen adsorption experiment was adopted to measure the specific surface area and pore structure of Liujia lignite, Sitai lignite, Tongxin bituminous coal and Baijigou anthracite, the variation laws of specific surface area, pore size distribution and pore volume with coal sample pre-oxidation temperature and pre-oxidation time were obtained. The results show that the specific surface area of oxidized coal samples from different coal mines has the same change law: pre-oxidized coal samples at 50 ℃>original coal samples >pre-oxidized coal samples at 120 ℃> pre-oxidized coal samples at 200 ℃, and the longer the pre-oxidized time is, the smaller the specific surface area will be. The pore size of pre-oxidized coal samples from four coal mines is concentrated in the range of 2-10 nm. Coal samples 50-6(pre-oxidized at 50 ℃ for 6 h) have the highest cumulative pore volume value, while coal samples 200-24(pre-oxidized at 200 ℃ for 24 h) have the lowest cumulative pore volume final value. The internal pore network of coal sample 50-6 is the most developed, it is easier to react with oxygen under the same conditions, thus has the highest spontaneous combustion risk, while the coal sample 200-24, on the contrary, has the lowest spontaneous combustion risk.
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