Pyrolysis Characteristics And Mechanism Of Upgraded Low-rank Coal

The significance of low-rank coal thermal upgrading was explained in this paper. The binderless briquetting mechanism of low-rank coal was illustrated and the pyrolysis rules of low-rank coal and briquette were studied comparatively. The results indicated that the semicoke yield from the briquette was larger than that from the raw coal, and semicoke characteristics of the former were better than the latter. Tar yield and gas calorific value of briquette pyrolysis were equivalent to that of raw lignite pyrolysis, however, waste water output reduced dramatically. More amount of gas were obtained from briquette pyrolysis especially during heating stage above 550℃. Matlab simulation method was used to establish relational expressions of gases volume and pyrolysis conditions. It was found that pyrolysis gas volume and temperature present a power function relation in heating stage, while an arctangent function relation exists in holding period. The pyrolysis kinetics parameters of low-rank coal and briquette were calculated through Costs-Redfern method, and the pyrolysis mechanism of briquette was discussed. Bri-semicoke indexes such as volatile, strength, gasification reactivity, calorific value were comprehensively measured along with the changes of pyrolysis condition, and the results showed that the optimum pyrolysis temperature of briquette was 750℃.50kg-scale briquette and similar size block raw coal pyrolysis were carried out in a vertical batch furnace. The comparison result showed that briquette pyrolysis rate was faster than raw lignite at the same pyrolysis temperature, and, the yield of semicoke breeze was reduced obviously.