Experimental Study on the Improvement of Char Physicochemical Properties and Reactivity by Activation Process in CFB

Solid carbon can be transformed into activated char with higher reactivity through the activation process in a circulating fluidized bed (CFB) to improve the Boudouard reaction. A new technology for reducing CO₂, the activated-reduction technology, was proposed. In order to investigate the influence of relevant parameters (carbon dioxide addition, oxygen concentration, and O₂/C) of the activation process on the physicochemical properties and reactivity of activated char, the experiments were carried out on a bench-scale CFB. The relationship between the parameters and the reactivity of activated char is explored. The result shows that compared with the raw coal, the pore structure of activated char is developed, the number of active sites increases, the degree of graphitization decreases, and higher reactivity is possessed. For the activation process, less of the O₂/C and moderate oxygen concentration promote the increase in activated char reactivity, which is conducive to the reduction of CO₂. The results of the correlation discussion show that the reactivity is difficult to be characterized by a single simple parameter. The reactive specific surface area (RSSA) obtained by multiplying the mesoporous specific surface area and I _D3+D4/I _all has a good effect on describing the reactivity.