酸洗脱矿对油页岩热解失重特性及动力学的影响

Effect of demineralization on pyrolysis characteristics and kinetics of two Chinese oil shales

通过逐级酸洗脱除桦甸和巴里坤油页岩中的矿物质,采用热重分析仪对油页岩原样和脱矿样进行热解,基于热失重特性和热解动力学考察酸洗对油页岩热解的影响。结果表明:经过盐酸酸洗脱除碳酸盐后,两种油页岩在150℃~510℃失重的初始温度分别降低92℃和40℃,且最大失重速率降低、失重量减少,说明碳酸盐在低温下能抑制小分子化合物的释放,在高温下能促进干酪根的分解失重。再经氢氟酸-盐酸酸洗脱除硅酸盐后,桦甸油页岩的最大失重速率增大,说明硅酸盐在高温下可抑制干酪根的分解失重。对于两种油页岩在350℃~510℃的热解反应,逐级脱除碳酸盐和硅酸盐使表观活化能分别减小10 k J/mol和增大30 k J/mol,说明碳酸盐增大了失重反应速率对温度的敏感度,而硅酸盐减小了失重反应速率对温度的敏感度,且硅酸盐的影响比碳酸盐显著。

Step-wise acid washing was applied to eliminate the indigenous minerals of Huadian and Balikun oil shales. The pyrolysis experiments of raw and demineralized oil shales were carried out by using a thermogravimetric analyzer. The effects of demineralization on pyrolysis were investigated by comparing the thermal weight loss characteristics and kinetic parameters of different oil shale samples. Results showed that after removal of carbonate minerals,the onset temperature of weight loss was decreased by92 ℃ and 40 ℃,respectively,and the maximum weight loss rate and weight loss were reduced. These indicated that carbonate minerals inhibited the release of small organic molecules at low temperatures and promoted the thermal decomposition of kerogen at high temperatures. Further de-silicate of carbonate-free oil shale increased the maximum weight loss rate of Huadian oil shale,which suggested that silicate minerals suppress kerogen pyrolysis at high temperatures. As to the pyrolysis reaction of oil shale at350 ℃-510 ℃,de-carbonate decreased and de-silicate increased the apparent activation energy value by about 10 kJ/mol and 30 kJ/mol,respectively. This indicated that carbonates increased while silicates decreased the temperature sensitivity of weight loss rate and silicates played a more pronounced effect than carbonates.