With the rapid development of the low-rank coal chemistry industry, the production of semi-coke has ever been increasing. However, the semi-coke is difficult to burnout and the NOx generation during semi-coke combustion is high. Therefore, the co-combustion of semi-coke and bituminous coal in utility boiler is considered as a promising approach to realize the efficient utilization of the semi-coke. Here, the co-combustion features of bituminous coal and semi-coke blends were investigated in a 660 MW utility boiler. The results show that the NOx generation decreases firstly and then increases with the rises of the load and the fraction of semi-coke. The effects of load and blending ratio of semi-coke are both obvious on burnout behavior than those on NOx generation. With the rise of oxygen concentration, the NOx generation rises and the unburned carbon in fly ash decreases. The Na-bearing mineral are better-preserved with the higher oxygen concentration. The experimental results may provide guidance for the realization of the utilization of the semi-coke in the utility boiler.
Keywords co-combustion, semi-coke, 660 MW utility boiler, blends, bituminous coal