Self-heating and autoignition of coal in rock silos

Storing solid fuels like coal in large quantity is known to involve a risk of spontaneous combustion. In comparison to conventional open stockpiles, closed storage may in principle decrease this risk by more limited ingress of air, but the risk can also be enhanced for example by reduced access for preventive or mitigating action. The risk of self-heating until ignition is considered here for a unique underground rock storage of a coal-fired power plant. The main adverse consequence of non-functioning storage is interrupted district heating that is more difficult to replace in winter than lost electricity supply. To predict the risk of spontaneous combustion with reasonable confidence, material modelling of coal properties has been applied with verification by comparison to actual field evidence. Fire risk management is discussed in terms of the available early warning indicators and options for cooling, extinguishing and prioritised use of stored fuel.