(631c) Separation Performance of a Coupled Cyclone with Built-in Circulating Granular Bed Filter(C-CGBF)

Many current industrial processes including the fluidized catalysts cracking (FCC), the biomass gasification (BG), the integrated gasification combined cycle (IGCC) and the pressurized fluidized bed combustion (PFBC), need an effective hazardous particles removal technique for protecting the downstream components from abrasion/erosion/fouling, improving the system efficiency as well as meeting the environmental emission requirements. Cyclones, wet scrubbers and electrical precipitators are generally used for separating dust particles . Recent researches suggest that ceramic filters and granular bed filters maybe the most promising technologies for hot gas clean-up. However, single separation device usually cannot meet the stringent demands in high temperature high pressure (HTHP) gas purification. In order to improve the efficiency and operation stability, various separation processes/mechanisms were commonly combined or coupled in new designs.

In this study, a coupled cyclone separator with built-in circulating granular bed filter (C-CGBF) was proposed for HTHP dry gas cleaning, combining the centrifugation with the filtration in one device. Owing to the pre-separation in the cyclone shell, the filtration load of the built-in granular bed is efficiently reduced; while the fine particles entrained by the cross-flow gas can be further captured by the granular bed. As a result, the gas-solids separation is evidently strengthened. The purpose of this study was to evaluate the gas-solids separation performance of the C-CGBF. The pressure drop and collection efficiency were measured and analyzed in a pilot-scale cold-model experimental apparatus. The influences of the operating regime, the inlet dust concentration and the inlet gas flow rate on the performance of the C-CGBF were investigated.

Experimental results revealed that the pressure drop of the C-CGBF increased linearly with time under the fixed bed (FB) operating regime if introducing dust particles. On the other hand, a steady-state pressure drop with high collection efficiency, typically exceeding 95%, was achieved under the moving bed (MB) operation. Both the pressure drop and the collection efficiency increased with the inlet dust concentration. The collection efficiency declined when the inlet gas flow rate was increased from 800 to 1400 m³/h. The dusts hold-up in the granular bed and the filter cake formed on the outer screen wall of the built-in granular bed contributed to the high collection efficiency, as well as the increase of the pressure drop. Compared with the dusts depositing in the bed, the filter cake had the advantage that it did not clog the collector granules. In addition, the filter cake was also restrained by the self-cleaning of the swirling flow, especially at high inlet gas flow rate. The separating performance of the C-CGBF is anticipated to be improved by paying attention to the control of the filter cake in the future. The contribution ratio of the cyclone shell to the total collection efficiency was around 80% under the MB. Increasing the inlet dust concentration and the inlet gas flow rate improved the contribution of the cyclone shell. The majority of the particles captured by the cyclone shell were larger than 10 μm.