A NUMERICAL STUDY OF COAL DEVOLATILIZATION IN AN ENTRAINED-FLOW REACTOR

This paper reports a numerical study of the steady, turbulent reacting two-phase flow in an experimental axisymmetric bench-scale entrained-flow reactor using a readily available computer code. Emphasis is focused on the temperature history and heating rates of individual coal particles. This information, which is difficult to obtain experimentally, plays an important role in assessing coal devolatilization experiments. Numerical simulations are presented and analyzed for reactor temperatures in the range 1000-1650 K (1500-2500°F). The coal considered is of subbituminous type with a particle size range of 20-100 microns. The results illustrate the details of the coal devolatilization process as predicted by a two-competing thermal reaction model. In particular, the mechanism by which the particle temperature history affects this process is elucidated. It is shown that the measured trends of volatile yields with reactor temperature can be predicted with this simple model provided that the temperature history is known. The predicted gas component yields agree fairly well with measurements in the higher-temperature range ( > 1300 K). In the lower-temperature range, the equilibrium chemistry assumption seems not to be appropriate. © 1989.