Model predictions and experimental results on self-heating prevention of stockpiled coals

The spontaneous combustion of coal stockpiles is a serious economic and saf ety problem. This phenomenon is herein analysed using a TNO-model modified to predict the spontaneous heating behaviour of coal piles built with "Mezc la", a mixture of low rank coals from Teruel (Spain). The simulation carrie d out with the mathematical model for this coal showed that the pile porosi ty or voidage and wind speed play an important role, although voidage is de cisive and controls the effect of the wind velocity. To reduce the negative effects of both factors, five test coal piles (2000-3000 t) were built and several measures were applied to four of them: periodic compaction, use of a low angle slope. protection of the stockpiled coal with an artificial wi nd barrier and covering it with an ash-water slurry. The heat losses were e xperimentally determined and it was found that the mathematical model gave predictions of the right order of magnitude of time, site of spontaneous co mbustion and magnitude of calorific losses. All the methods of protection a pplied to decrease the self-heating of coal were effective, but the experim ental results indicate that the most economical way to avoid the heat losse s is the use of an ash-water slung to cover the coal pile. (C) 2000 Elsevie r Science Ltd. All rights reserved.