Determination of Time Optimal Diafiltration for an Ultrafiltration Process

An ultrafiltration process (UFP) associated with the Hanford Department of Energy facility separates sodium solution from radioactive solids, which are then individually immobilized. An oversight of the UFP design and operation has identified several areas to improve the capacity of the UFP. This paper presents the development of a time optimal controller for an ultrafiltration process (UFP). The current mode of operation is a form of diafiltration where feed rates into the UFP are matched with the permeate rates (permeate matching diafiltration). Another approach advocated in this paper is to allow the control parameters into the UFP to vary with time and is termed time optimal diafiltration. It will be shown that permeate matching diafiltration and time optimal diafiltration are equivalent in terms of dewatering times, but not in terms of feedback. An empirical model for optimal time was then developed.