CHANGES IN PRESSURE LOSS AND FACE VELOCITY OF CERAMIC CANDLE FILTERS CAUSED BY REVERSE CLEANING IN HOT COAL-GAS FILTRATION

Hot coal gas filtration using ceramic candle filters with off-line cle aning showed rapid changes in pressure loss and face velocity during f ilter cleaning, due to the injection of cleaning gas and the decrease of filtration area. These changes had the capacity to affect facilitie s which are sensitive to pressure change and filter durability. From t his point of view, on-line pulse jet cleaning was thought to be prefer able to offline cleaning but still caused some changes. Numerical calc ulations showed that a smaller system pressure loss before cleaning an d a short pulse duration were most effective in reducing those changes . Some properties of the pulse jet cleaning were also investigated bot h experimentally and by numerical calculations. In a long candle, the cleaning pressure, which is the pressure difference in the filter and residual dust layer, varied along the filter, and a diffuser or an ent rance region was necessary to accomplish cleaning throughout the filte r. A one dimensional numerical model could estimate the cleaning press ure as a function of reservoir pressure, filter permeability, etc. (C) 1998 Elsevier Science S.A. All rights reserved.