Influence of cohesion and adhesion on detachment parameters of consolidated filter cakes in pulse jet cleaning

Filtration plants for solid-gas stream filtration are widely used in the industry in order to reduce the amount of particulate for process requirements or to obtain adequate atmosphere emissions. One of the technological problems in these systems is the formation of powder cakes on the filter which affects the filtration performance; therefore, the filter has to be cleaned and the cake removed in order to keep the pressure drop to a suitable level for the filtration process. In the present work, attention is paid on the identification and on the analysis of the critical parameters for the cake detachment from bag filters using pulse-jet cleaning. The influence of the powder cake properties on the detachment parameters is studied. To detach the powder cake from the filter, the applied stress must be equal or above a critical value defined as the detachment stress. It is the force necessary to remove the cake from the filter and to break the cake itself. The detachment stress is retrieved through pressure measurements on an air stream across a filter on which the cake is built. Also the pressure rate is registered and investigated as a critical parameter. The cohesion of the cake and the adhesion between the cake and the filter are measured at different consolidation states of the cake. Then, the detachment parameters behavior with respect to this variation is analysed. Three cake consolidation levels and three different types of powders are considered: limestone, aluminium oxide and hematite. A needlefelt filter fabricated of polyimide is used. The process of detachment was observed and presented. From the analysis of the results, the pressure rate cannot be defined as a critical parameter for the process. The detachment pressure seems to be independent on the cohesion and the adhesion stress and therefore on the consolidation stress. . Instead, a further analysis on the influence of the particle shape and size could be performed.