CHARACTERIZATION OF CERAMIC CANDLE FILTERS UTILIZED FOR EMISSION CONTROL DURING COAL GASIFICATION

摘要

High temperature ceramic candle filters are a key component in advanced coal based gas turbine cycles such as Integrated Gasification Combined Cycle (IGCC) and Pressurized Fluidized Bed Combustion (PFBC). The filters protect the downstream heat exchanger and gas turbine components from particle fouling and erosion effects and cleans the gas to meet the particulate emission requirements. However, these filters are found to have sudden functional and physical failures prior to their designed life time. Thus, identification of the causes that led to the early failure of these filters is an important issue in coal gasification technology. An experimental investigation has been carried out to provide a systematic study on the characterization of candle filters. Several new and used filers were tested to provide insights into variations of filter permeability and the effect on permeability when iron oxide, used as sorbent, is present in the dust cake layer. Results show that used filters develop non-uniform permeability distribution both axially and circumferentially which is likely to cause asymmetric flow pattern in the filter chamber. The presence of iron oxide in the dust cake was found to improve the overall permeability and was also easier to dislodge by back pulse cleaning mechanism.