Wall Recession Rates in Cavity-Growth Modeling

摘要

The predictions of resource utilization obtained from cavity-growth models depend on the methods used to represent the recession rates of the walls of the cavity. Under many circumstances the cavity is largely filled with a bed char rubble. Examination of the mechanisms for recession at walls adjacent to these char beds indicates that the recession rates are controlled by convective heat transfer from the bed to the walls coupled with the thermomechanical breakdown of the walls. A recession-rate representation has been developed, based on this concept, for use in cavity-growth simulation programs. This representation characterizes wall breakdown by either a failure temperature or by a thickness of char layer at failure, and determines rates from a model of heat transfer under these conditions. It gives recession rates that are functions of gas temperature and mass flow rate in the cavity, and depend on effective particle size in the char bed. Wall recession rates calculated for WIDCO, Hoe Creek, and Hanna coals are in the range of 0.1 to 0.8 m/day at a 1300 K cavity temperature, and are consistent with the general rates observed for field tests. 27 references, 10 figures, 1 table. (ERA citation 09:042609)