A pharmaceutical suspension is synthesized such that a significant amount of salt is formed during neutralization. This micro-fine suspension is washed out of salt by diafiltration and further concentrated. Initial salt concentration is about 10 % and the active ingredient is around 3.5 %. The desired final concentration is almost no salt (< 0.1 %) and 7.5 % active ingredient.

The fineness of the suspension requires microfiltration. With conventional crossflow technology a further concentration of the suspension is impossible due to the high viscosity. Therefore, dynamic crossflow filtration is required. Systems with rotating ceramic discs have too low throughput and require 100 m² filter area. Hence the BoCross Dynamic Filter is the only available technology for this challenging separation task.

Three 8 m² BoCross Dynamic Filters are applied for thickening and washing of this viscous suspension achieving the target values of 7.8 % active ingredient and 0.1 % salt.