MODELING THE FLOW AND THE DEPOSITION OF FILLERS IN PACKED-BEDS OF PULP FIBERS

The process of flow through a packed bed of pulp fibres and the deposi tion on the fibres of fillers passing through the bed has been modelle d theoretically. The flow is described by a residence time distributio n and is assumed to be completely segregated so that the bed can be di vided into a number of sections, each characterized by a constant flui d velocity. For each section, the transport of fillers is governed by two partial differential equations describing particle transport and t he deposition kinetics. The transport through the bed is found by inte grating over all sections, using the residence time distribution of th e flow through the bed. From this model one can calculate the concentr ation of fillers at the exit of the bed as a function of time, and the number of fillers deposited on the fibres. It was fouund that particl e deposition is controlled by four dimensionless parameters that can b e estimated for any bed by knowing the flow conditions and the deposit ion kinetics. The effect of these parameters on the amount of fillers depositing in the bed and passing through it are presented.