Flexible design and operation of a two-step UF/NF-system for product recovery from rinsing waters in batch production

Water and concentrated product solution can be recovered from rinsing waters of the batch production of surfactants and detergents. This investigation is focused on anionic and non-ionic surfactant solutions. Two different membrane processes have been investigated experimentally. For the concentration of the product solution the ultrafiltration is investigated. The ultrafiltration process is modelled on the basis of a gel layer resistance approach. The model is validated using the experimental data. The simulation is used to calculate the optimal design and operation parameters for a multi-stage UF concentration plant. Under economic constraints, an optimal number of feed-and-bleed-stages can be found. For the water purification, a nanofiltration step has to be implemented for some surfactant solutions. Depending on the separation characteristic, CIP-batches are treated with a single (UF) or two-step membrane process (NF/UF).