Pyrolysis Of Agricultural Stalks And Liquefaction In Water

Some typical agricultural wastes, including com, durra, rice and legume stalks, and the main components of biomass, including hemicellulose, cellulose and lignin, were pyrolyzed with thermal gravimetric analysis method with or without catalyst addition. Meanwhile, liquefaction of the stalks was investigated in a semi-continuous apparatus with a non-isothermal technique in sub-and supercritical water. And for comparison, liquefaction of corn stalk was carried out in methanol, ethanol and the blending of methanol/water or ethanol/water. Based on the research, the catalytic liquefaction of biomass and the co-liquefaction of biomass and coal were also investigated in water.(1) The collection, disposal and analysis were completed based on ASTM methods and thermogravimetric analysis was used to study the pyrolysis characteristics of selected stalks and their main components, hemicellulose, cellulose, lignin and benzene/ethanol extractables in the stream of N2 with/without sodium carbonate or potassium carbonate as catalyst. Four kinds of methods, Coats-Redfern, Doyle, Kissinger and Distributed Activation Energy Model (DAEM), were used to determine the kinetic parameters. The results indicated that the kinetic parameters were different with different methods. DAEM is an efficient method to provide more information of the pyrolysis of biomass samples.(2) Liquefaction of various stalks was carried out in semi-continuous apparatus with non-isothermal method to investigated the general properties under different conditions such as temperature, pressure, flow rate of solvent and heating rate etc. near sub-critical water. Based on the research, the liquefaction of the individual and blending of different samples are studied in water. The experiments show that water is a great potential solventand reactant in dealing with biomass to gain liquid products at high pressure and an appropriate temperature. A little higher conversion and yield of liquid products can be obtained with blending feedstocks than the individual sample.(3) A series of experiments were also carried out in methanol, ethanol or the blending of methanol/water, ethanol/water for the comparison with the case in water. The main pyrolysis range of stalks is in the range of sub-and supercritical states of water, so water is a potential and effective solvent for biomass liquefaction, in which high conversion and more liquid yield can be obtained than that in methanol or ethanol. With addition of methanol or ethanol, the conversion and liquid yield can be increased and the quality of liquid is improved. However, high temperature can lead to the decomposition of methanol and ethanol.(4) Catalytic liquefaction of corn stalk in water shows that catalyst plays a positive effect on the liquefaction at relatively higher temperature and can not only increase liquid product yield, but also improve the liquid product quality. With catalyst, more bio-oil and less gas can be obtained than that without using catalyst.(5) The co-liquefaction of biomass and coal is studied in water with rice stalk and Xiaolongtan (XLT) coal as test samples. Since the main pyrolysis range of biomass and coal are vast different, and the heating rate is too slow, no evidence of synergistic effects was found for the test samples in the semi-continuous liquefaction process.