| Abstract: | Because there has been a recent increase in the use of low calorific coal compared to standard coal, it is crucial to control
the char flame length governing the burning life-time of coal in a coal-fired utility boiler. The main objective of this study
is to develop a simplified model that can theoretically predict the flame length for burning coal in a laboratory-scale entrained
laminar flow reactor (LFR) system. The char burning behavior was experimentally observed when sub-bituminous pulverized coal
was fed into the LFR under burning conditions similar to those in a real boiler: a heating rate of 1000 K/s, an oxygen molar
fraction of 7.7 %, and reacting flue gas temperatures ranging from 1500 to 2000 K. By using the theoretical model developed
in this study, the effect of particle size on the coal flame length was exclusively addressed. In this model, the effect of
particle mass was eliminated to compare with the experimental result performed under a constant mass feeding of coal. Overall,
the computed results for the coal flame length were in good agreement with the experimental data, particularly when the external
oxygen diffusion effect was considered in the model. |
