CALCULATION OF PERMEATE FLUX AND REJECTION IN SIMULATION OF ULTRAFILTRATION AND REVERSE-OSMOSIS PROCESSES

A method for calculation of ultrafiltration and reverse osmosis processes has been developed to enable the calculation of permeate flux and rejection at different pressures and concentrations. The method has been combined with a process simulation program which calculates all streams of the process. Permeate flux and rejection in membrane processes are dependent on pressure and concentration of the solution. This dependence has to be known in the simulation of these processes. Normally a considerably large number of time consuming experiments have to be made to find the dependence of permeate flux and rejection on pressure and concentration. In this work the minimum experimental information was determined to enable the calculation of permeate flux and rejection. Two calculation procedures, one based on the finely porous model and the other on the statistical-mechanical model, were used. In these models permeate flux and rejection are described by four quantities. The values of these quantities are constant for each separation system having the same solution, membrane and temperature. A method of obtaining the values of these quantities from experiments is described and the minimum experimental information was determined to enable the calculation of permeate flux and rejection over the entire operating range of the process.