(303g) A Methodology Supporting the Design of 4-Section and 5-Section Jo Systems in Multicomponent Separation. I-Case of Linear Adsorption

Several important chromatographic separation processes have been developed using the Simulated Moving bed (SMB) technology, providing the high purification potential of these continuous countercurrent methods. Most of the research on SMB technology is focused on operations with classical four-section SMB. In spite of the advantages associated with such configuration (high-purity products, low eluent consumption, continuous feed and production), it is limited to two outlet streams (extract and raffinate) allowing only the separation of binary mixtures. When the feed is a multicomponent mixture, one of the outlet streams will contain several components and the other will contain only one component (the weakest adsorbed components in raffinate or the strongest adsorbed component in extract). In the recent years, some alternatives have been suggested to perform multicomponent separation using SMB technology and several ideas were considered such as SMB with five sections, cascade of two SMBs in series, which, in this case, can be either separated or combined in a single device (SMB with eight sections and SMB with nine sections are examples), cascade of SMB systems for ternary and quaternary separations, and pseudo-SMB. It was showed by application of the equilibrium theory that neither a five section SMB nor an eight section SMB can separate three compounds into three pure fractions. The pseudo-SMB system represents the JO chromatographic separation device, which has been reported as adequate in the separation of mixtures such as separation of high purity maltitol from mixture of maltitol, monosaccharides and polysaccharides; high level purification of diethylnaphthalene isomers; fractionation of beet molasses into raffinose, sucrose, glucose, betaine. The JO chromatographic separation system uses a patented chromatographic separation technology developed by Organo Corporation. Very little has been published concerning JO technology and it is our task to contribute to the understanding and design of process units using such technology. The JO Separation system works partially using the concept of SMB technology, in a way that the unit configuration allow not only the recovery of the less retained component, A, and more adsorbable species, B, but also the recovery of an intermediate component (I) of intermediate affinity with adsorbent phase, which is interest for multicomponent separations. The JO system is a cyclic process consisting of two steps: (i) in step 1, which corresponds to the operation of a sequence of chromatographic columns (fixed beds), the intermediate species is collected; and (ii) in step 2, the concept of SMB is used but with no feed. ?X Step 1. The feed is introduced in the unit. The configuration system is a set of preparative chromatography columns connected in series, as the SMB in open loop. The fluid phase circulates through the columns packed with the solid adsorbent. The difference in affinity allows the chromatographic separation as it happens in a simple chromatographic column. In a particular point of the system, a stream of eluent is also introduced to elute the intermediate species I in the only outlet stream in step 1. ?X Step 2. Now the system operates in closed loop circuit and the solid movement is simulated by the change in the ports positions of the inlet (eluent stream) and outlet streams (extract and raffinate). There is no feed stream in the step 2. In this way, the JO process could seem as an operation in partial feed where feed stream (and other external streams) is added and withdrawn at constant rate. The countercurrent operation, leading to the high mass transfer driving forces, is accomplished by the simultaneous shift of the inlet and outlet streams, at fixed time intervals, called switching time (t*), in the fluid phase flow direction. The system operates in step 2 exactly as a SMB without feed. Each section of the system has a specific task in order to achieve high performance separation; a large number of operating variables should be designed and optimized. Due to its complex operation and configuration, modelling and simulation are tools which help in a deeper analysis of the system behaviour and performance. In this work, the design of JO process units is addressed. A decision-helping tool has been developed to aid in the analysis of equipment sizing and finding adequate operating conditions of units based on the JO technology. In order to achieve a good separation performance in the JO system, some criteria based on the propagation of species need to be satisfied. At the end of the step 2, species A and B must have been collected in their respective enriched streams and the intermediate species propagates until a position in which, during the step1, it can be recovered without large contamination. Step 1 can be designed as a loading step since the feed enters the system only during step 1. If the feed conditions are known - flow rate and species concentration in the feed - for a JO system, the operation variables such as step times, internal flow rates in each section, switching time (step 2) need to be determined to obey the required performance criteria. In the manuscript, a sequence of definitions is presented aiming at the attainment of the base operating conditions providing a high performance for the JO system. The velocities of propagating concentration (w) in step 1 and 2 of a JO system are taken considering the equilibrium theory. In step 1, the propagation of species occur only in the direction of the fluid phase while in step 2 the migration of species can occur in both directions: fluid flow and solid flow. The choice of working flow rates for step 2 of the JO process for ternary separation was based on two different strategies depending on the adsorptive properties of the species in the mixture mainly. The performance parameters of the system (purity, productivity, eluent consumption) for the separation of ternary mixture with different degree of difficultness of the separation are discussed. The integration of the chromatographic process in fixed bed and SMB at the 4-sections JO has been modelled using lumped mass transfer model and simulated by computational algorithm. The SMB model has been based upon the equivalent TMB model approach. An extension of the 4-sections JO system for ternary mixtures is developed to be used in the separation of mixtures with four components. The JO System designed for quaternary mixtures has five sections: a new section is introduced between the feed stream and intermediate collect stream of the 4-sections JO system. Therefore, two intermediate species will be recovered during step1 of an operation cycle. For 5-sections JO system, a set of equations to determine operational conditions for the JO system are needed to recover species appropriately. In step 1, tS1 is any time such that the concentration front of the intermediate specie with lower affinity does not move to eluent regeneration section, otherwise it will contaminate the product in raffinate stream during step 2. During this time, intermediate species must be eluted from sections placed in middle of system. Therefore, some design criteria for the operation of 4-sections JO system were revised and new migration rules were used to obtain operational conditions for the 5-sections JO. It has been possible to separate a four components mixture classified as moderate separation, achieving high-purity products in their enriched outlets.