NAMS 2002 Workshop - ICOM 2008

Membrane Modeling III - Process Simulations – 2
Wednesday July 16, 10:15 AM-10:45 AM, O’ahu/Waialua
Effects of Long-Term Membrane Fouling on the Dynamic Operability of an
Industrial Whey Ultrafiltration Process
K. Yee (Speaker), UNESCO Centre for Membrane Science and Technology, Sydney, Australia
J. Bao, School of Chemical Sciences and Engineering, Sydney, Australia
D. Wiley, UNESCO Centre for Membrane Science and Technology, Sydney, Australia -
d.wiley@unsw.edu.au
1. Introduction
In the production of whey protein concentrate (WPC) by ultrafiltration (UF), the
flowrate and composition of the fresh whey feed often fluctuate. Automatic
feedback controllers are implemented in industry to maintain the WPC product
within its desired specifications. The manipulated variables of the automatic
controllers include the ratios of the retentate and permeate streams that are
recycled and mixed with the fresh feed, as well as the amount of diafiltration
water added to the process. By adjusting the manipulated variables, the
automatic controllers are able to mitigate the effects of fluctuations in feed
flowrate and composition.
In order to achieve an optimal economic return from WPC production, the
achievable control performance from a given process design needs to be
determined before the actual feedback controller is implemented. This intrinsic
property of the process design towards automatic control is called dynamic
operability. Based on the dynamic behaviour of manipulated variables from an
industrial whey UF process, the effects of the number of stages of the process
and recycle streams on dynamic operability have been investigated by the
authors [1, 2]. However, given that industrial whey UF processes usually operate
for 16 hours every day, the effects of long-term membrane fouling on dynamic
operability is not well understood. The aim of this study is therefore to investigate
the effects of long-term fouling on the dynamic operability of an industrial whey
UF process, and the implications on process operation. The study is based on
dynamic models of an industrial whey UF process developed by the UNSECO
Centre for Membrane Science and Technology.
2. Results and Discussion
Dynamic operability of the industrial whey UF process indicates that the required
adjustments in manipulated variables to deliver the same level of control
performance increase with time during the 16 hours of operation. Given the
physical constraints of the manipulated variables (e.g. recycle ratios are bounded