Filtration Performance of Coal Pyrolysis Flying Char Particles in a Granular Bed Filter

The filtration of flying char particles from coal pyrolysis vapors plays a very important role in enhancing yields and quality of pyrolysis oil. In this work, the performance of coal pyrolysis flying char particles in a granular bed filter (GBF) was studied in cold model experiments. A filtration model was developed using a macroscopic phenomenological method that describes the filtration of the GBF. The polynomial expression of the relative filter coefficient (F) and the nonlinear expression of the relative pressure drop ratio (G) were applied in the new model. The unsteady state of granular filtration was captured, demonstrating that the GBF performance could be predicted by the new model. Effects of superficial gas velocity, thickness of granular layer, and dust mass concentration on collection efficiency and pressure drop were analyzed. An excellent performance of the GBF was obtained and the total collection efficiency could reach a span between 98% and 99.9%. In the case of lower dust mass concentration, the total collection efficiency and pressure drop were slightly affected by the increasing dust mass concentration. The optimal operating conditions of the GBF were obtained: a superficial gas velocity of 0.2–0.6 m/s and a granular layer thickness of 0.07–0.11 m.