A full-scale experimental and modeling investigation of dust explosions in a roller mill

摘要

Combustion of biomass is becoming an increasingly important energy source. This is especiallytrue for wood pellets, as several power companies have decided to use this fuel instead of coal.In this process the wood pellets are ground in big mills and, from there, pneumaticallytransported to the burners in the boiler where they are consumed. The grinding of biomass andcoal represents an explosion hazard, which can potentially result in considerable damage to thepower plant upon propagation of the explosion from the mill into other parts of the installation.An experimental investigation was performed aiming at understanding the potential damage thatcan occur due to an accidental dust explosion in a mill under worst case conditions. The testswere performed in a roller mill (capacity 36 metric tons coal/hour; internal volume 23.2 m3)connected to a coal feeder located on top of the mill.Test conditions were predefined using the CFD-based dust explosion simulation tool DESC.DESC was used to estimate the flow conditions inside the roller mill during normal operatingconditions. In the full-scale tests these flow conditions have been simulated by the use of a dustinjection system.In total 25 tests were performed and a number of parameters were varied, including dust type(wood dust and coal dust), dust concentration and dust cloud location.