Moving bed granular filtration of fast pyrolysis char: Granular flow rate study

Moving bed granular filter (MBGF) shows a good promise for hot gas clean up of biomass fast pyrolysis to filter fine char particles. This research project examines the effect of granular flow rate on the performance of a MBGF at cold flow conditions.;In understanding the effect of granular flow rate on the MBGF performance, the filter's collection efficiency and char accumulation in the filter's are assessed at experiments of different granular residence times (tg). A process particle counter (PPC) is used to measure the filter's exiting particle concentration, knowing the inlet concentration values the collection efficiency can be calculated. Moreover, pressure drop measurement was used as a tool to assess char accumulation in the filter. For this purpose, pressure was measured in several locations within the filter's bed in order to evaluate dust accumulation level for each bed section. A correlation of pressure drop and accumulation of char dust has been developed and used to understand how char accumulates over time for the different bed regions.;Experiments indicate that the MBGF needs to be operated below a critical granular residence time (tg*), below which the filtration efficiency exceeds 99%. Operating above than tg* would cause the filter to "clog" and face decrease in efficiency. The filter is found to accumulate most of the dust at the interfacial region where dust-laden gas first meets the granular media. It was also found that the interfacial region is more efficient than the other bed regions.;Decreasing the granular residence time in the filter can be used to minimize the amount of accumulated char dust in the filter, which is advantageous for avoiding secondary reactions during fast pyrolysis' hot gas filtration.