On-line particle sizing of pneumatically conveyed biomass particles using piezoelectric sensors

In recent years the firing of biomass at existing or new power plants has been widely adopted as one of the main technologies for reducing greenhouse gas emissions from power generation. The particle size distribution of pneumatically conveyed biomass correlates closely with combustion efficiency and pollutant emissions and should therefore be monitored continuously.

In this paper, an instrumentation system based on a polyvinylidene difluoride (PVDF) piezoelectric film sensor is proposed, to achieve on-line continuous measurement of biomass particle size distribution. The sensor is attached to an impact bar protruding into the biomass particle flow. The relationship between the resulting impact signals and particle size is modelled mathematically, allowing particle size distribution to be inferred. Experimental work, undertaken with willow chips and miscanthus chips, has allowed both the effectiveness of the on-line particle sizing system and the validity of the mathematical model to be evaluated. The results indicate that the system has good linearity and repeatability.