Use of Single-Column Models for Efficient Computation of the Periodic State of a Simulated Moving-Bed Process

in Wiley InterScience (www.interscience.wiley.com).The simulated-moving bed (SMB) is now a well established adsorption process for obtaining high-purity products at a similarly high-recovery. In principle the SMB process can be applied to gases, and has been, but application has been limited. Here, we reexamine the SMB process for separation of gaseous components in the light of recent developments in novel cyclic operating schemes and advanced optimization tools. A novel single-column experimental setup is employed to demonstrate the feasibility of the process, explore the effect of its major operating parameters, and illustrate the performance enhancements that are obtained by using an advanced cyclic operation scheme, such as the asynchronous shifting of the inlet/outlet ports. The experimental feasibility and effectiveness of gas-phase SMB are assessed by running and comparing optimized configurations for the separation of CH 4 /CO 2 over activated carbon using nitrogen as carrier gas. For this separation, the asynchronous configuration always outperforms the classical SMB scheme, both in productivity and eluent consumption, except at very low-feed throughput where both schemes are coincident. At higher-feed flow rates, the asynchronous scheme quickly diverges from a four-zone, closed-loop configuration towards a three-zone, open-loop process with a 50.6% increase in feed throughput, and 10% reduction on eluent gas consumption.

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“…1 references solely column j , and that it is identical to the original node balance, except that y

_{italici,j −1}^{out}

( t ) was replaced by y

_{italicij}^{out}

( t ′). This substitution is legitimate, because it does not change the steady periodic solution 37, 38…”

Section: Methodsmentioning

confidence: 99%

Synchronous and asynchronous SMB processes for gas separation

2007

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“…This model, which is described in Appendix B, retains all of the essential properties of the full Parex model—including the bed‐head dead volumes and bed lines—but is computationally much more efficient because its CSS solution can be efficiently computed using a full‐discretization approach. Although this approach has been previously used in simpler SMB models with a small number of columns, it was never applied to the industrial‐scale, 24‐column Parex process.…”

Section: Influence Of the Dead Volumes On The Performance Of The Parementioning

confidence: 99%

Effect of dead volumes on the performance of an industrial‐scale simulated moving‐bed Parex unit for p‐xylene purification

2015

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The cyclic steady state (CSS) of the industrial-scale, seven-zone, simulated moving-bed (SMB) unit for p-xylene (p-x) purification (Parex unit) with three types of dead volumes-bed lines, push-around and pump-around circulation lines, and bed heads-is analyzed. In particular, the effects of the size and level of hydrodynamic dispersion of each dead volume on process performance and on its CSS are studied in detail. The circulation lines change the CSS behavior from t Ã -periodic to Nt Ã -periodic, where t Ã is the switching interval and N512 is the number of columns in each adsorbent chamber. A high level of axial dispersion in the bed lines, characterized by P eclet numbers smaller than 100, affects the p-x purity. Moreover, the bed lines lower the average p-x concentration in the extract, which reduces the p-x recovery. If the small time lags introduced by the circulation lines are neglected, it is possible to develop a detailed process model that considers the operation of the Parex unit over a single switching interval as opposed to a full cycle, and whose CSS solution can be efficiently computed using a full-discretization approach. Finally, it is shown that the volume of the bed heads influences significantly the performance of the Parex unit, and that its impact on the location of the operating point with respect to the boundaries of the separation region can be approximately taken into account using the standard true moving-bed-SMB equivalence rules if they are corrected for the presence of extra interparticle fluid.

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“…Hereby, the evaluation of the processes typically requires time-consuming numerical determinations of the cyclic steady-state concentration profiles. Various suggestions to obtain these results faster and more efficiently have been made (e.g., [20][21][22]). This interesting aspect as well as new and promising concepts to control SMB processes [e.g., [23][24][25][26], will not be further discussed here.…”

Section: Classical Simulated Moving Bed Chromatographymentioning

confidence: 99%

New Developments in Simulated Moving Bed Chromatography

2008

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Chromatographic separation processes are widely used to isolate and purify value added products. Most frequently, such separation processes are performed exploiting the principles of injecting samples of the feed mixture in a repetitive periodic manner and collecting the target products batchwise. In the early 1960s, an alternative operation principle based on using several columns connected in series and exploiting a continuous countercurrent movement between the mobile and stationary phases initiated significant improvements in performing specific separation processes in the petrochemical and sugar industries. In the last decade, the so-called simulated moving bed (SMB) chromatography has rapidly entered the pharmaceutical industry. In particular enantioseparations using chiral stationary phases have become a strong driving force to develop more sophisticated concepts of continuous chromatography. Currently, the growing interest in efficient methods for the downstream processing of biomolecules enhances interest in SMB processes. This paper gives a brief overview of the new suggestions and trends. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [accessed July 4, 2008

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Use of Single-Column Models for Efficient Computation of the Periodic State of a Simulated Moving-Bed Process

Cited by 34 publications

References 55 publications

Synchronous and asynchronous SMB processes for gas separation

Synchronous and asynchronous SMB processes for gas separation

Effect of dead volumes on the performance of an industrial‐scale simulated moving‐bed Parex unit for p‐xylene purification

New Developments in Simulated Moving Bed Chromatography

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