Stugy In Mechanism Of Low-Temperature Roasting Reduction Of Low Grade Pyrolusite By Three Major Components Of Agriculture And Forestry Byproducts

Pyrolusite reduction technology includes direct reduction leaching and roasting reduction leaching, where many kinds of reducing agents are used in pyrolusite reduction processes. Recently, agriculture and forestry byproducts have been investigated as as an environment-friend, energy-saving and low-cost reducing agent for roasting reduction of pyrolusite.First, bagasse pith, a fibrous residue from the bagasse paper or board of separating bagacillo, was used as a reducing agent to roast low-grade pyrolusite. Optimal conditions were determined to be bagasse pith to manganese ore weight ratio of0.62:1, roasting temperature of350℃for60min, leaching stirring speed of200r·min-1, sulfuric acid concentration of3.0mol·L-1and leaching temperature of60℃for40min. Liquid/solid ratio is6mL·g-1. The leaching rate of manganese was up to97%at the optimal conditions.Secondly, the reduction processes of pyrolusite by agriculture and forestry byproducts major components (cellulose, hemicelluloses and lignin) were investigated by using TG-FTTR and PY-GC/MS. FT-IR and PY-GC/MS results indicate that various reductive volatiles (such as aldehydes, ketones, alcohols, acids etc.) were produced in the pyrolysis of three components, which directly reduced MnO2in ore to MnO and were oxidized to CO2.Dollimore method was applied to investigate the kinetics of the investigated reduction processes. Cellulose or lignin reduction of pyrolusite is controlled by three dimensional diffusion processes, while hemicelluloses reduction of pyrolusite is controlled by interface chemical reaction. The values of apparent activation energy are calculated to be112.034KJ·mol-1for cellulose reduction of pyrolusite,64.280KJ·mol-1for hemicellulose reduction of pyrolusite and83.904KJ·mol-1for lignin reduction of pyrolusite. The integral kinetic equation2for cellulose or lignin reduction of pyrolusite, and (1-α)-1for hemicelluloses reduction of pyrolusite.