Kinetics Study Of A Near Zero Emission Coal Utilization Technology With Combined Gasification And Combustion

Coal is the main primary energy source in China, which will remains for a long time in the future. As the traditional coal utilization technology has two fate defaults: low efficiency and heavy pollution, it is necessary to develop a new technology with high efficiency and low pollution emission including carbon dioxide. Zhejiang University has developed an innovative near zero emission coal utilization technology with combined gasification and combustion. In this system, coal or other flexible fuels mixed with CO₂ absorbents such as CaO will be partly gasified by steam to produce rich-hydrogen gas, meanwhile CO₂ will be sbosorbed by CaO in a pressurized circulating fluidized bed reactor. The product gas will be utilized in SOFC to produce electricity power or transported to other hydrogen users. The unreacted char will be oxidated in combustion furnace to release energy for CaCO₃ calcination.This thesis introduced the current state of other similar zero emission system worked over by some institute in foreign countries. And the contents in this thesis focused on three aspects: (1) experiments in the pressured thermal balance; (2) kinetics modeling, including gasification, carbonation, combustion and calcination progress; (3) bench-scale system design.Carbonation experiment in high pressure conditions has been carried out in a pressured thermalbalance to find out the Carbonation reaction characters. Also, limestone calcination experiment in high CO₂ pressure has been conducted.The CO₂ partial pressure has significant negative effect on the calciantion process. Activation energy distribution has been obtained in the range of atmosphere to 0.5MPa.A mathematical kinetic model of coal gasification with CaO carbonation and combustion with calcination has been developed. This model was used to predict the production gas components and reaction rate in, different conditions. Based on the simulation result we compared the effects of different pressure and temperature, and advanced an optimal operating parameter's range, which would be helpful in the next research stage especially for the bench-scale experiments.In this thesis a bench-scale experiments system has been disgned including two circulating fluidized bed reactors, on which gasification and combustion experiments under 0～5MPa,750～100℃ could be carried out.