Experiments Research And Mechanism Analysis Of Biomass Carbonization By Catalytic Pyrolysis

As the increasing in quantity of solid biomass waste, soil pollution and degradation problems increasingly serious, reasonable development and utilization of biomass resources, research and development of new effective soil restoration agent have become the current urgent research subject. Biochar to increase soil carbon library, improve soil fertility and maintain soil ecosystem balance is of great significance, therefore is becoming more and more attention all over the world. Thermal conversion technology is the most effective way to realize the biomass utilization,and catalytic pyrolysis is regarded as the most effective method of change of biomass pyrolysis conditions and pyrolysis product distribution and properties, the mechanism of catalytic pyrolysis and carbonized technology of biomass (rice straw and bamboo waste) were systematically researched in this paper, the main research contents and results were as:1.The physical and chemical properties of biomass materials were analyzed, the results showed that bamboo waste have relatively high content of cellulose and lignin, and more hemicellulose in the rice straw. The industrial analysis showed that volatile content of bamboo waste is about86%, and ash content of rice straw is15%. Two kinds of raw materials in the content of N, S are trace.2. Three components of biomass as raw material to carry out thermogravimetric experiment, and the effects of seven additives (KOH, TiO2, CuCl, CaCl2, FeCl2, KCl and NaCl) and heating rate were investigated, and calculated the pyrolysis kinetics parameters. Results show that the pyrolysis rate of cellulose is highest, and lignin pyrolysis is relatively slow. The initial pyrolysis temperature of hemicellulose is lowest. KOH can significantly increase the yield of solid products of cellulose and lignin pyrolysis, CuCl mainly can reduce xylan pyrolysis temperature and increase xylan pyrolysis rate, CaCl2can reduce xylan and lignin pyrolysis temperature, and FeCl2can decrease the glycan pyrolysis temperature. With the increase of heating rate, the pyrolysis curve moves to the high temperature and weight loss rate increased.3. The rice straw and bamboo waste as raw material, the effects of KOH, TiO2, and heating rate have investigated by thermogravimetric experiment, and calculated the pyrolysis kinetic parameters, at using TG-FTIR to analyse the characteristics of volatile products of pyrolysis separation of the two kinds of raw materials. Results show that: the initiation temperature of bamboo waste pyrolysis is lower and pyrolysis rate is faster. The yield of solid production of rice straw pyrolysis is high, and the yield of gas and liquid of bamboo waste pyrolysis is high. The apparent activation energy of pyrolysis reaction of bamboo waste is between172-233KJ/mol, and rice straw is between152-233KJ/mol. KOH can change thermogravimetric curve of biomass. The volatility of pyrolysis products of two kinds of biomass are mainly for CO, CO2, H2O, CH4, alkanes and lipid, C-O-C compounds and aldehydes and organic acids, volatile products of bamboo waste is high.4. The rice straw and bamboo waste as raw materials, pyrolysis carbonization experiment was carried out on self-made pyrolysis reactor. The results showed that the yield of bamboo biochar is between28-35%, and the yield of rice straw charcoal is between41-52%, conventional pyrolysis way more suitable for biomass carbonization. With the increase of pyrolysis temperature, carbon yield decreases. Adding TiO2can slightly increase the yield of biochar, and a small amount of KOH can promote the yield of biochar, the yield of biochar decline when the content KOH is higher than30%. Pyrolysis temperature is lower, the greater the influence of additives on the yield of biochar. Two kinds of additives are inhibiting the production of liquid products, but KOH can improve the yield of gas of bamboo waste pyrolysis.5. The following conclusion is obtained by analyzing the physical and chemical properties of biochar:with the increase of pyrolysis temperature, the carbon content of biochar increases, and the content hydrogen and oxygen is reduced, and carbon content of bamboo biochar is much higher than rice straw charcoal. Biocharl contain a variety of minerals, the content of mineral elements in rice straw charcoal were higher than in bamboo charcoal; Both kinds of biomass carbon shows alkaline, TiO2can reduce biomass charcoal pH, and KOH is opposite. Biochar contain a variety of surface functional groups, including O-H, C-O, aromatic ring of C=C, etc., the aliphatic functional groups is lost gradually and aromatic functional groups is increasesed as the temperature rise of carbonization,. There were inorganic carbonate roots in biochar when adding KOH, Rice straw charcoal surface is porous, and the surface of the biochar is loose with the higher the temperature, the holes are more apparent, TiC^can promote the degree of cracking on the surface of the biochar. Pyrolysis process did not affect TiO2crystal structure, biochar contain inorganic and organic sylvite by adding KOH. That KOH catalytic biomass pyrolysis can get a rich potassium of biochar soil restoration agent, TiO2catalytic biomass pyrolysis can get a kind of biochar environmental protection material containing photocatalyst.6. There are four major constituents of biomass pyrolysis gas H2, CO, CH4and CO2, the highest content of CO2with low pyrolysis temperature. With pyrolysis temperature increasing, the content of CH4and combustible gas increased obviously. Adding the KOH can significantly increase the yield of H2, so the quality of the pyrolysis gas get improved.7. Chemical composition of rice straw bio-oil is mainly composed of ketones, phenols and alkane, furfural, furfural alcohol and fat. Bamboo bio-oil is the main composition of phenolic compounds, and ketones, alkanes compounds, and a small amount of alcohol, acid and lipid. Both additive improves the bio-oil phenolics relative content.Using the proposed ideas, namely, choosing the appropriate quantity additives and biomass pyrolysis can obtain different types of biochar composite products, at the same time, the conditions of pyrolysis and quality of by-products can be improved significantly.