Study On Pyrolysis Of Biomass (Rice Husk) By Microwave Heating

Biomass is an important renewable energy. China is affluent in biomass resources, since it is a big agricultural country. Rice husks as a major by-product in the rice milling industry are abundant in china with an annual production of more than 0.36 billion tons. It has great significance for raising peasant's income and reducing environmental pollution to seek a reasonable way for the rice husk utilization.Pyrolysis is an indispensable process in biomass gasification and combustion and controlled pyrolysis at different conditions can also be a means of preparing activated carbon or bio-oil. Research on biomass pyrolysis rule is of great significance for its conversion to other forms of energy carriers.This paper deals with the pyrolysis characteristics with samples of rice husk on a bench scale microwave pyrolysis installation, the frequency employed is 2450MHz and the power capacity can be adjusted from zero to 4kW proportionally. A serial three phase U-shaped tube train immersed in the ice-water mixture bath is used for cooling and collecting the condensable components. The gas product from rice husk pyrolysis is collected at different periods. Gas and liquid is analyzed by GC and GC-MS. Rice husk diameter, microwave power and N₂ flow rate are investigated, which affect the yield and composition of gas, liquid and solid. Volume percentage of gas components is also affected. The gases produced from pyrolysis consist mainly of H₂, CH₄, CO and CO₂. The main components of liquid products were phenolic compounds, among which 2,3-dihydro-benzofuran, 2-furanmethanol, phenol, 9-octadecenoic acid (Z)-4-methyl-phenol , naphthalene and n-hexadecanoic acid were enriched components. The oxygen content of bio-oil was high, and ca.60% water exists in the liquid products. The solid residue mainly contains residual carbon and amorphous silica.All of the three inorganic additives have increased yields of gaseous products greatly and decreased yields of liquid products and solid products more or less. Of the three additives employed,that is, cacium oxide, magnesium oxide and dolomite, micirowave catalytic pyrolysis with magniseum oxide led to the highest gaseous product yield when the dosage of additives are less than 40% of the rice husk sample. When the dosage of additive is between 80% and 100%, dolomite gave the highest gaseous product yield which is up to 60.67% when the dosage of dolomite is 100%.Compared with blank experiment when the dosage of additives was fixed at 100%, the yield of hydrogen and carbon oxide was increased by 278% and 58% respectively using magnesium oxide and that was increased by 141% and 102% respectively using calcium oxide and by 75%å’Œ141% by dolomite. In addition, experiment showed that reuse of dolomite could also lead to excellent catalytic role. The yield of hydrogen and carbon oxide was increased by 85% and 201% respectively by employing equal amount of residuce dolomite for pyrolysis.