Studies On Coal Catalytic Pyrolysis Characteristics During Hydrogen-rich Atmosphere

In China, the energy situation of rich coal with lack of gas and oil, and the present status of serious environmental issues, give rise to recycling, energy and high efficiency utilization of coal with low pollution. Coal pyrolysis combustion technology developed by Zhejiang University is an effective way to solve the problem of energy shortage and environmental pollution. If coal directional pyrolysis can be realized and tar quality be improved, the higher economic and environmental benefits of the polygeneration technology will be achieved. Therefore, this paper launched researches on hydropyrolysis and catalytic pyrolysis of coal, for a purpose of increasing quality and quantity of tar and gas.First, by preparation of Ni/Al2O3with Ni loading (2%,5%,8%,10%), the effect of hydrogen-rich atmosphere and catalysts on Shaanxi Yanchang coal pyrolysis was investigated through TG-FTIR and Py-GC/MS. With catalysts and solid products analyzed by SEM, BET and XRD, the effects of heating rate, atmosphere and catalyst amount on coal pyrolysis characteristics were discussed. Coats-Redfern method was used to solve the kinetics parameters of coal pyrolysis under different atmospheres. Analysis result shows that, after700℃there is a turning point of weight loss on thermo-gravimetric curve of CH4atmosphere pyrolysis.In mixed gas atmosphere, H2restrains CH4from carbonizing but too much is likely adverse to volatile escaping. According to activation energy, the catalytic effect is order by:5%Ni>10%Ni>8%Ni>2%Ni.Besides, the effects of hydrogen-rich atmosphere, N1/Al;2O3or Mo/HZSM-5catalyst on pyrolysis characters were investigated in a tube furnace. Analysis result shows that, compared with N2atmosphere pyrolysis, the content of heavy components in tar during CH4atmosphere pyrolysis has increasd. H2atmosphere and mixed atmosphere contribute to producing light oil and removal of impurity atoms from tar. With Ni/Al2O3catalyst, the light component content of tar is as high as90%between500℃and800℃. With Mo/HZSM-5catalyst, the tar molecules tend to form heavy components such as benzenes. When the pyrolysis is isolated in relation to coal and catalysts, aromatization effect of Mo is reduced, and yield of aliphatic hydrocarbon in the tar increases. With temperature going up, all component gases release earlier and their largest release concentration improves.Hydrogenation has a delayed effect on the time of gas release, and catalystic process increases the largest release concentration of gases as well as shortens their high release time.