ADSORPTIVE SEPARATION STUDY ON A CONTINUOUS SIMULATED COUNTER-CURRENT UNIT

Abstract

This research study has demonstrated the practical feasibility and efficiency of a continuous mode of adsorptive separation by means of a simulated moving bed process. High quality product streams are obtained with purity and recovery rate close to or above 90% (w/v). A product stream with concentration of solute higher than the feed is also achieved in this study. Enrichment of 30% is attained under non-isothermal operation of the separation process. Two types of homogeneous mixture, namely glucose and fructose as well as monoethanolamine and methanol, are successfully separated by the adsorptive separation unit. The former, which has a linear and non-interacting adsorption relationship, helps to elucidate the important features of the simulated moving bed process while the latter, which has a non-linear and coupling adsorption relationship, provides a more general representation of most homogeneous mixtures. The study has also achieved the objectives of providing a fundamental understanding of the principle of operation as well as theoretical modellings of the process. Operation constraints are theoretically derived and experimentally demonstrated. A dimensionless parameter y which specifies the net flow directions of solute along every section of the separation cascade is developed. Two theoretical models, namely The Linear Continuous Counter-current Model and The Equilibrium Stage Model, are derived to represent the experimental separation profiles at cyclic steady state. It is shown that the Linear Continuous Counter-current Model has the advantage of speed and simplicity but is only adequate for linear system while The Equilibrium Stage Model involves more complex computations but is adequate for both linear and non-linear coupling systems. Experimental and theoretical simulated concentration profiles at cyclic steady state are presented. A brief comparison on three types of adsorbents, based on their selectivity for fructose in separating a mixture of glucose and fructose is presented. The adsorbents include : Linde X and Y sieve as well as Duolite C204 ion exchange resin in ca++ form. Davison Y sieve and Duolite C204 ion exchange resin both in ca++ form are used as adsorbents for the various separation studies. Detailed adsorption kinetics and flow dynamics studies on these two adsorbents are experimentally carried out and discussed. Theoretical and empirical adsorption relationship of glucose and fructose mixture as well as monoethanolamine and methanol mixture on the above two adsorbents are derived. Flow dynamic parameters such as DL and k are also established experimentally.