Pyrolysis Characteristics Of Two Kinds Of Desert Shrubs And Co-pyrolysis Interaction Of Them With Coal Blends

Desert Shrubs widely planted in the Northwest China as a shrub species, though the research of biomass thermo-chemical conversion-thermal cracking, it can benefits the use of waste resources, the optimization of energy structure and the protecting of ecological environment. The pyrolysis process of Desert Shrubs including Salix psammophila and Korshinsk Peashrub, kenetic data, and their formation characteristics of products were investigated by thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TG-FTIR) methods. The results showed that:the pyrolysis process is divided into three stages which are physical changes, fast pyrolysis and coke pyrolysis. And the volatile characteristic of Salix is better than Caragana, and the pyrolysis reaction was more easily carried out. The rise of heating rate led to more release of volatile matter in the second stage, but are unfavorable to the pyrolysis of coke component in the third stage and coke yield at 800℃ were reduced. Decrease of the particle size and the gas phase residence time are all increase char yield. Kinetic analysis was carried out to analyze pyrolysis of Salix psammophila and Korshinsk Peashrub with the Coats-Redfern and FWO methods, which indicated that activation energies(E) of fast pyrolysis stage were ranged within 102.75～135.81 KJ·mol-1 and 126.32～158.40KJ·mol-1 respectively,and it was suitable for Avrami-Erofeev equation. The pyrolysis gaseous products are mainly H2O, CO2, CO, CH4, alkanes and carbonyl compounds, and the volatile of CO, CO2 in the late carbonization stage are mainly from pyrolysis of conjugated carbonyl in the lignin. The coke residue IR spectrum showed, C-O and C-O-C bonds of glycosidic finkages and sugar rings structure in hemicellulose and cellulose have been broken, and the absorption band of benzene ring skeleton stretching vibration partly disappear.In the whole process of weight loss the volatilization of volatile matter was mainly ascribed to the pyrolysis of functional groups containing oxygen. The influence rule of the thermal cracking of mixture along with alkali metal salts catalyst were further discussed.The co-pyrolysis characteristics and interaction effect of four coals abound in Inner Mongolia with two desert shrub were investigated using a thermo-gravimetric apparatus. The influence results of different coal and different mixing proportion in Salix cheilophila blend and Korshinsk Peashrub blend are exactly opposite. The experimental results show that the interaction effects of co-pyrolysis process can be divided into 4 stages:Firstly, the temperature period of violent weight loss of biomass correspond to the first and second stage, the inhibition on biomass volatile is precede to that of promotion of coal pyrolysis by volatile substances of biomass; Thirdly, in the temperature period of biomass coke pyrolysis, the interactions between biomass coke and coal were influenced by biomass species, and biomass coke promoted or inhibited the coal pyrolysis respectively; Finally, in the high temperature section of co-pyrolysis process, biomass ash minerals promoted coal pyrolysis. The mechanism of ignition of the mixture of desert shrubs and coals were changed with the oxygen concentration increasing, that pyrolysis with nitrogen carrier gas is transformed into heterogeneous of the whole combustion; Excessive high oxygen content induce the release of volatile matter of the mixture, and high concentration of O2 has strong effect on the ejection of the volatile matter with the high biomass-to-coal ratio.