Set up of an experimental apparatus for the study of fragmentation of solid fuels upon severe heating

fragmentation of solid fuels under severe heating conditions. The devise is a modified heated strip reactor, capable to reach 2000°C in less than 0.2s. Particles are laid on the strip and pyrolysed under inert or moderately oxidizing conditions. The char particles and their fragments, generated upon pyrolysis, can be recovered and analysed to assess the fragmentation propensity of the fuel. Some preliminary experiments have been carried out on two biomass samples in order to assess the temperature time history of particles in the experimental apparatus. In particular biomass particles of approximately 2-3 mm have been used. The temperature of the heated strip reactor in such preliminary tests was varied between 1000 and 1600°C, while the strip nominal heating rate was kept at 104°C/s and the holding time was set at the value of 10s. A near infrared fast camera (38000 frames/sec) has been used to measure the temperature of the heated strip and of the particles during the tests. A heat up model was developed and validated against experimental results. The model was then used to estimate the temperature gradients across particles of biomass and of coal as well. Results show that the strip of the reactor reaches the set temperature in less than 0.2s. When particles are laid on the strip, their bottom surface, which is in physical contact with the strip, immediately reaches the set temperature value. For 1mm coal particles the upper surface can be considered at the same temperature as well. Under the most severe conditions tested (strip temperature of 1600°C , biomass particles of 2mm thickness) the temperature difference between the bottom and the upper face is 200°C after 3s and drops to 100°C after 10 s. On the whole the experimental apparatus simulates uniform heating of the particles with reasonable approximation. In the next future the apparatus will be further upgraded to operate at pressures up to 20 bar.