Fibrous-bed coalescers are frequently used for separation of the suspension. The effectiveness of the process depends on the flow condition through the packed bed and its structure. The population balance equation was used for analysis of the evolution of the distribution of droplet diameter in the raw suspension due to the coalescence and breakage of droplets passing different sequences of the coalescer structures distinguished by the packing density of fibers in the layers of the coalescers. The results of calculations show the values of particular parameters, like droplet concentration, the mean diameter of the droplet and droplet size distribution in the population as the results of the process. The proposed model can be useful for the designing of the coalescer structures for their particular applications. (C) 2011 Elsevier Ltd. All rights reserved.