Study On Pyrolysis Kinetics And Gas Production Characteristics During Gasification Of Pine Sawdust In Fixed Bed Reactor

In the face of increasing serious fossil energy crisis, people have realized deeply theimportance of biomass energy and it will be a vital part of future sustainable energysystem. Synthesis gas produced via biomass catalytic gasification is considered to be oneof the thermo-chemical conversion processes with greatest research and developmentpotentiality. It is a research topic of strategic significance to invert biomass to clean en-ergy through biomass catalytic gasification technology and make full use of renewableresources.In this paper, it takes typical forestry processing residues-pine sawdust as the objectof study. Pyrolysis characteristics of the pine samples under NO₂and CO₂atmosphere werestudied separately with the method of non-isothermal thermogravimetric analysis. Py-rolysis dynamic characteristics of pine under different heating rates and CO₂concentra-tions were also studied with the purpose of providing data to support the biomass gasi-fication process design.The oxygen rich-steam gasification experiment of pine samples in a self-made fixedbed gasification reactor was carried out to study the influence produced by differentparticle sizes of raw material, gasifying reaction temperature, air flow, the concentrationof oxygen in oxygen-enriched air and water vapor flow on the content of each gascomponent and low calorific value. The experimental results indicated that: the effec-tiveness of gasification is better with smaller particle sizes of raw material; when the airflow is400ml/min, considering the hydrogen content and calorific value, the optimalgasification temperature is850°C and750°C respectively; the calorific value of pro-duced gas in oxygen-enriched gasification has increased compared to air gasification;when the reaction temperature is750°C, H₂and CO content reaches the maximum re-spectively when the oxygen concentration is40%and35%respectively. When the oxy-gen concentration remained unchanged at30%and the reaction temperature is750°C,the adequate water vapor flow will contribute to the H₂content and calorific value ofproduced gas. Excessive amount of water vapor on the contrary will lower the content ofH₂, thus affecting the calorific value of produced gas.Through the addition of secondary catalytic cracking reactor after the gasificationreactor, the changes of the component content of the gas production of pine samplesoxygen rich-steam gasification after catalytic cracking were investigated. Effects of the pyrolysis temperature and being loaded with different metal oxide additives on thecatalyst performance were studied respectively. According to the study, it is learned thatunder the action of NiO-Al₂O₃catalyst, with the catalytic pyrolysis temperature increase,H₂and CO content showed an increasing tendency, while the content of CH4, CO₂, C₂H₄,C₂H₆and C₃H₈decreased. Five kinds of metal oxide （Fe₂O₃,CuO, MgO, CeO₂,Cr₂O₃）were loaded on the NiO-Al₂O₃catalyst with co-impregnation method. Exploring theirinfluences on gas components, and then effects of being loaded with different metal oxideadditives on the NiO-Al₂O₃catalyst performance were reached. From the perspective ofhydrogen production, the effect degree of metal oxide additives on NiO-Al₂O₃catalystactivity has been ranked: Fe₂O₃> MgO> CeO₂> Cr₂O₃> CuO.