Flow measurement of biomass and blended biomass fuels in pneumatic conveying pipelines using electrostatic sensor-arrays

Key parameters such as particle velocity, concentration of solid particles, and stability of pulverized fuel flow in fuel injection pipelines are useful to power plant operators to detect fuel supply problems at an early stage. This paper presents the use of a novel multichannel instrumentation system with circular and arc-shaped electrostatic sensor arrays for the online continuous measurement of mean and local characteristics of blended biomass flow. Experimental tests were conducted on a pneumatic conveying test rig under various flow conditions on both horizontal and vertical pipes. The biomass fuels tested include willow, wood, and bark. A ground grain (flour) was used to replicate a biomass of finer particles. The results suggest that, due to the physical differences between the constituent biomass fuels, the characteristics of the flow depend on the proportion of larger biomass particles in the blend. It is found that pure flour particles travel faster and carry more electrostatic charge than those of larger biomass particles. As more biomass particles are added to the flow, the overall velocity of the flow slows down, the electrostatic charge level decreases, and the flow becomes less stable compared to the pure flour flow. Particles in the vertical pipe are found to be more evenly distributed, and the particle velocity profile across the pipe cross section is more regular when compared to those in the horizontal pipe.