| An attractive feature of pressurized fluidized bed combustion (PFBC) technology is power generation by the expansion of high temperature high pressure (HTHP) flue gas through a gas turbine. However, the flue gas must be clean enough to meet the tolerance limits of the turbine so that the particles and alkali in the gas would not reduce the life of turbine and the plant availability. For removing those impurities, the conventional gas cleanup devices used at low temperature and atmospheric environment conditions are no longer suitable, and therefore the HTHP gas cleanup systems are required. Unfortunately, none of those HTHP gas cleanup systems currently under development has reached commercialization stage and none of them has emerged as the most favorable for PFBC application.;For this dissertation, a review of the performance characteristics of some selected HTHP gas cleanup devices that show promise for commercial application is presented. The sub-pilot plant research performed here deals with three HTHP gas cleanup systems, namely, the Ceramic Cross Flow filter (CXF), the Screenless Granular bed filter (GBF) and High Temperature High Pressure Electrostatic Precipitator (ESP). The particle and alkali removal efficiencies, particle size and alkali content variation during the cleanup process, pressure and temperature drop across the filter are determined from the experiments to evaluate the performance of the filters. Two kinds of particle and alkali sampling methods, namely, grab and impactor techniques for particle and NYU total and METC/INEL monitoring methods for alkali, are introduced and shown in fairly good agreement with each other. A model based on the minimum porosity principle for wide range size distribution particles are developed to predict the pressure drop across the dust cake formed in CXF filtration process with 30% difference from the experiment results. The results show that all three filters have either design or operation problems which need to be improved even though CXF and GBF have the potential to protect the gas turbine from particulate with the particle capture efficiency of more than 90%. Further researches are needed to understand the mechanism of the filters and have accurate prediction of performance. |
