Predicting the pressure drop across hot gas filter (CTF) installed in a commercial size PFBC system

Abstract

The 71 MWe PFBC combined cycle power plant at Wakamatsu, Electric Power Development Company (EPDC) (funded by the Ministry of International Trade and Industry (MITI) and the Center of Coal Utilization Japan (CCUJ)) achieved 11,500 h accumulative operation while establishing extremely low dust emission (<1 mg/m3 N) with a hot gas cleaning system combining cyclones and ceramic tube filter (CTF). Two different configurations of cyclones and CTF were examined in Phases 1 and 2, where several coals and domestic limestone as absorbents were used.The pressure drop across the filter (ΔPc) was continuously observed to predict its maximum value (ΔPmax) under operating conditions. The ΔPmax value consisted of irreversible (ΔPbase) and reversible (ΔPown) drops with cleaning as the following equation shows,ΔPmax=ΔPbase+ΔPown=f(facevelocity,gasviscosity,thickness/permeability,dustconcentration)+dΔPc/dt×twhere: dΔPc/dt, mean rate of ΔPc increase during cleaning interval; t, reverse cleaning interval time.The pressure drop across the regenerator (ΔPregenerator) was monitored to calculate the changing face velocity of each compartment according to the Fanning equation. Both pressure drops (ΔPbase and ΔPown) were successfully estimated by the face velocity calculated for both phases. Dust concentration to the filter in both phases was found to improve the predictability of the base line one (ΔPbase).The conditioned filter material was proven to be stable, showing a constant drop depending on the operating condition. The particle size of ashes on the filter must be considered in order to obtain better prediction of the maximum pressure drop in the future.