Study On Detoxification And Kinetics Laws Of Chromite Ore Processing Residue Based On Biomass Tar

The pollution of Cr(VI)is becoming one of the greatest environmental problems in the world. More than 6 million tons chromium salg exist in China and the number is rising year by year, Cr(VI)brings lots of damages to soil, water and atmosphere due to the lack of storage management and the processing technology is backward.Biomass resource has the characteristics of reserves rich, easy access and renewable,according to the present situation of the chromium slag treatment technology, the study propose a new way of chromium slag detoxificication with biomass tar, which called by-products of biomass gasification. Mix chromium salg and biomass tar to make composite pellet for experimental study on pyrolysis, Cr(VI) could effectively be converted into Cr(III), which called treat wastes by wastes.then contrast the data to provide a theoretical basis and technical support for the following-up industry.Firstly, when pyrolysing the pellets, factors which influence the process as temperature, grain size of chromium residue and pellets, proportion of chromium residue and biomass tar should be tracked, then by means of data from orthogonal experiment to get the best condition. At the last, after the study of thermodynamics and kinetics, the main results are listed in the follwing paper.1.The size of pellet shows largest influence on the degree of reduction, when the size remained at 2.5mm, pellet has the biggest specific surface area, the highest degree of reduction is 93.12%, the degree of reduction increases first and then decreases with the rising of pyrolysis temperature, experimental quality work best at400℃. The effect of pyrilysis time for reduction degree increases and then decreases,when the cost of energy consumption taking into account, pyrolysis time should remains at 10 min. Increasing the content of biomass tar can improve the reduction degree, Excess biomass tar will lead to a decline in quality and the reduction degree of pellet. The propotion of chromium slag and tar which contained in pellet should be remained at 2.29:1. The smaller chromium slag particle size is, the higher reduction degree will be. The best condition of reduction reaction describe as below, dry the pellet for 40 min and the pyrolysis time is 10 min at 400 ℃, the particle size of chromium slag remained 0.074 mm.2.The reaction process is a first order reaction and the activation energy is about17KJ/mol with in a range of 573.15K-773.15 K. Gibbs function in the reductionprocess is a large negtive number shows that it is easy to react, meanwhile, the equilibrium constant is a large number and the procedure will react thorough.Chromium slag reduction is mainly based on solid-solid reaction.