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

Abstract

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 by 92 ℃ 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 at 350 ℃-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.

Keywords

• oil shale
• demineralization
• pyrolysis
• thermogravimetric analysis
• kinetic