Experimental Study On Biomass Pyrolysis Characteristics In The Presence Of Oxygen

China has a rich resource of biomass, while the distribution of which is dispersed. And most of the agriculture and forest residues were directly burned in the open air each year, which led to energy waste and environmental problems. In this scene, developing a small scale, distributed energy system based on gasification technology is meaningful to both solve the energy and environmental problems in the countryside, and promote rural economic development.Our research team is devoted to develop a two stage biomass gasifier, which has good feedstock adaption and produces low tar content gas. But during the R&D stage, we had to face the problem of leaking air in the pyrolysis stage, making pyrolysis actually carried out in an oxidative environment. The main subject of this paper is to study the pyrolysis of wood under oxidizing atmosphere. Experiments are directed to investigate the mechanism of oxidative pyrolysis. And the numerical method is used to simulate partial oxidation of the pyrolysis product gas.Firstly, in accordance with the oxygen concentration gradient in the pyrolysis stage of the gasifier, oxidative pyrolysis behaviors under different oxygen concentration were investigated using thermogravimetric-mass spectrometry technique, while paying close attention to the gas formation and thermal activity. The results showed that, generally, oxidizing atmosphere could moderately enhanced the devolatization, the maximum devolatization rate increased, and corresponding temperature was lower compared to inert pyrolysis. In addition, the calculation of heat based on DSC curve showed that heat value of devaluation process of inert pyrolysis was 176.1 kJ/kg.Secondly, ,we used a continuous feeding pipe reactor to investigate the product distribution and character of pyrolysis product under different oxygen concentration which is more close to the real situation in the two stage gasifier. The results showed that in general, an increase in pyrolysis oxygen concentration results in an increase of total gas yield, The concentration of CO and CO₂ in product gas increased while CH4 and H2 decreased when the oxygen concentration increased in detail. Increase in pyrolysis oxygen concentration led to low tar yield, of which the oxygen contained compound increased especially phenol. Compared with the inert environment, there is low -OH and more PAH functional groups in the char generated by oxidative pyrolysis. Finally, in order to investigate the influences of pyrolysis gas composition on partial combustion, experimental investigation were done using a tube reactor as the partial combustion zone and numerical simulation approach was used to investigate the in detail the partial oxidation zoon. Experimental results showed that when the pyrolysis oxygen concentration increased, the CO₂ concentration in the product gas increased, while CH₄ concentration and total tar yield decreased. And the numerical simulation results fitted satisfactorily to the experimental data.