An Integrated System for Synthesis of Pure Amorphous Silica, Furfural and other Chemicals from Biomass

摘要

The biomass namely rice husk and straw contains a high percentage of finely divided amorphous silica. This silica is a cheap source of a number of value added chemical products like pure silica, silicon, furfural and various silicates. Amorphous silica itself is widely used as filler in the rubber industry. An integrated system for production of pure silica, furfural and a low calorie gas is likely to be economically feasible and unique. The thermogravimetric analysis (TGA) of raw and mineral acid treated rice husk and straw in still air reveals that their thermal decomposition occurs in three main stages namely (ⅰ) drying, (ⅱ) fast devolatilization and flaming combustion of volatiles, and (ⅲ) slow combustion of fixed carbon. Almost all the metallic impurities are removed by treatment of husk and straw with 1(N) mineral acids at about 75℃ for about 1 h. Pure white amorphous silica and low calorie gas could be produced on decomposition of acid treated rice husk and straw in a vertical electric furnace with a natural draught when a 20 cm deep bed of these biomass of about 6% moisture (wb) were subjected to a furnace temperature of 450℃ for about 3 h. During the process of acid treatment of husk furfural can be synthesized chemically using 7% concentrated HCl at a moderately high temperature and pressure of about 4 kg/cm~2.