Modelling media movement during cleaning of pulse-jet fabric filters

Pulse-jet fabric filters are one of the most common items of plant for remo ving particles from process gases. During operation, a cake of dust builds up on the outside of the filter fabric. The growth of this cake increases t he pressure drop of the filter and makes periodic cleaning necessary. The c ake is generally removed by injecting a short pulse of gas into the clean s ide of the filter in a direction which is the reverse of the normal flow. T his pulse causes the cake to be thrown off the surface of the fabric. The d ynamics of the fabric motion during this type of cleaning pulse are modelle d and compared with experimental measurements performed on an industrial sc ale pilot plant filter. Building upon earlier work, a picture of how the ca ke is removed from the fabric during the cleaning process is presented. Equ ations describing the propagation of the cleaning pulse down the filter and the acceleration that it produces are presented. The pulse is transmitted in a wavelike manner causing the fabric to expand so rapidly that it propel s the cake off the fabric surface. The fabric expansion controls the cleani ng process. The model is extended to consider cage design and to allow for the slackness of fit between the bag and the supporting cage. Good agreemen t is demonstrated between theoretical prediction and experimental results.