Patchy cleaning of rigid gas filters - I. A probabilistic model

Filtration with ceramic filters is a major technology for removal of particulate emissions at high temperatures. In combination with injection of a dry sorbent (‘dry scrubbing’), ceramic filters are also used to remove gaseous contaminants. Such filters are regenerated by application of a reverse pulse of cleaning gas; this frequently leads to partial or ‘patchy’ cleaning, rather than complete simultaneous cake detachment. This paper presents a probabilistic model to describe, as a result of patchy cleaning, the area distribution of cake patches with different ages, the thickness distribution, the velocity distribution, and the pressure drop history. A generalised probability distribution has been derived. Different modes of patchy cleaning have been proposed and can be simulated by changing the value of a weighting factor contained in the generalised distribution. Incorporated into a fixed-bed reaction model, this model makes it possible to examine the effect of patchy cleaning on dry scrubbing of acid gases in filter cakes.