Pyrolysis characteristics of Xinjiang Baishihu vitrinite-rich coal with high alkali content

The fixed bed furnace,Gray-King assay device and thermogravimetric analyzer were used to investigate the pyrolysis characteristics and products distribution of Baishihu vitrinite-rich coal (BS1 and BS2 coal). Furthermore,the different sodium forms in these coals were studied by the sequential chemical extraction experiment,and the influence of pretreatment on pyrolysis products and kinetics of Baishihu coal was also discussed. The results showed that the tar yield achieved its maximum content at 600 ℃ ,and gas yield increased with temperature increasing. The tar yield of vitrinite-rich BS1 and BS2 coal was obviously higher than Zhundong coal with high inertinite content. The tar yield of BS1 and BS2 coal from fixed bed pyrolysis was 13. 98% and 13. 75% respectively,which is markedly higher than 1.61% of Zhundong coal. The pyrolysis gas of Baishihu coal was mainly composed of H2 ,CH4 and CO;tar with low density,and high H / C atom ratio and diesel distillate content. The water soluble sodium ( H2 O-Na) was the main form of sodium in BS1 and BS2 coal,accounting for 79. 58% and 85. 38% respectively. The ammonium acetate soluble sodium (AcNH4 -Na) accounted for only 10. 32% and 8. 06% in BS1 and BS2 coal,but had a greater inhibitory effect on tar production than H2 O-Na. After pretreated by H2 O,AcNH4 and HCl,the activation energy and pre-expo-nential factor decreased,the first pyrolysis reactivity increased but second reactivity decreased and then promoted high-er tar yield content,so the tar yield of BS2 coal by Gray-King assay increased from 14. 80% to 15. 45% ,17. 18% and 16. 92% ,respectively.