VELOCITY-MEASUREMENTS IN A CERAMIC CANDLE FILTER ELEMENT UNDERGOING PULSE CLEANING

Ceramic candle filters have been developed for cleaning high-temperatu re gas streams. They have demonstrated high collection efficiencies un der normal operating conditions, but the brittle materials can fail su ddenly with disastrous consequences. Reverse pulse cleaning has been s hown to introduce severe thermal stressing of the material. Modelling of the flows to estimate the life of the element is difficult due to n on-uniformities in the material. It is important to obtain experimenta l measurements of flows in the candle to provide input to stress model s. In addition it is essential to ensure uniform cleaning of the filte r and knowledge of the pulse cleaning flow processes are also importan t for this. This paper reports velocity measurements obtained using a hot-wire probe located at different positions along the length of a ce ramic candle filter. The data have been analysed to estimate the outfl ow along the length of the candle filter to investigate the cleaning p otential of different configurations and operating parameters. The eff ect of pulse length on cleaning performance was investigated for cases with and without a venturi educer. It was found that the maximum peak mean velocity was produced at a pulse duration of 0.2 s. Longer durat ion pulses did not have a significant influence on the maximum velocit y levels inside the filter.