Yoshiaki Kawajiri

Comparison of various ternary simulated moving bed separation schemes by multi-objective optimization

Over the past decade, many modifications have been proposed in simulated moving bed (SMB) chromatography in order to effectively separate a binary mixture. However, the separation of multi-component mixtures using SMB is still one of the major challenges. In addition, the performance of SMB system highly depends on its operating conditions. Our study address this issue by formulating a multi-objective optimization problem that maximizes the productivity and purity of intermediate eluting component at the same time. A number of optimized isocractic ternary SMB operating schemes are compared both in terms of productivity and amount of desorbent to feed ratio. Furthermore, we propose a generalized full cycle (GFC) formulation based on superstructure formulation encompassing numerous operating schemes proposed in the literature. We also demonstrate that this approach has a potential to find the best ternary separation strategy among various alternatives.

Large scale optimization strategies for zone configuration of simulated moving beds

Simulated moving bed (SMB) processes are widely used in sugar, petrochemical, and pharmaceutical industries. However, systematic optimization of SMB, especially finding the optimal zone configuration including the standard and modified non-standard configurations, is still a challenging problem. This paper proposes a simultaneous, fully discretized approach with an SMB superstructure using an interior-point solver. To find the optimal structure, two superstructures are analyzed to develop standard and non-standard configurations. In case studies of the linear and bi-Langmuir isotherms, optimal zone configurations have been successfully obtained without introducing discrete variables. Finally, the effect of the number of columns on the optimal throughput is investigated.

Optimization of simulated moving bed chromatography with fractionation and feedback: part I. Fractionation of one outlet.

A novel modification of simulated moving bed (SMB) technology, referred to as fractionation and feedback SMB (FF-SMB), has been introduced recently. This concept is based on fractionating one or both outlet streams and feeding the off-spec fractions back into the unit alternatingly with the original feed mixture. In this paper, the optimization problem of FF-SMB realizing one outlet fractionation is considered. A mathematical optimization framework based on a detailed process model is presented which allows to evaluate quantitatively the potential of this operating scheme. Detailed optimization studies have been carried out for a difficult separation characterized by small selectivity and low column efficiency. The results reveal that the proposed fractionation and feedback regime can be significantly superior to the classical SMB chromatography, in terms of both feed throughput and desorbent consumption. The effect of the feeding sequence on the performance of FF-SMB is also examined.

Simultaneous modeling and optimization of nonlinear simulated moving bed chromatography by the prediction–correction method

This work demonstrates a systematic prediction-correction (PC) method for simultaneously modeling and optimizing nonlinear simulated moving bed (SMB) chromatography. The PC method uses model-based optimization, SMB startup data, isotherm model selection, and parameter estimation to iteratively refine model parameters and find optimal operating conditions in a matter of hours to ensure high purity constraints and achieve optimal productivity. The PC algorithm proceeds until the SMB process is optimized without manual tuning. In case studies, it is shown that a nonlinear isotherm model and parameter values are determined reliably using SMB startup data. In one case study, a nonlinear SMB system is optimized after only two changes of operating conditions following the PC algorithm. The refined isotherm models are validated by frontal analysis and perturbation analysis.

Systematic optimization and experimental validation of ternary simulated moving bed chromatography systems.

Over the past several decades, many modifications have been proposed in SMB chromatography in order to effectively separate a binary mixture. However, the separation of a multi-component mixture using SMB is still one of the major challenges. Recently, a computational study was performed which compared various existing isocratic ternary separation operating schemes (including the JO process) in terms of the maximum throughput attained, and Generalized Full Cycle strategy was proposed based on a systematic design, which was found to have significant improvement over existing strategies [Agrawal and Kawajiri (2012)]. Nevertheless, the operating strategies were not experimentally validated. In this study, we validate both JO and Generalized Full Cycle SMB systems experimentally. A simultaneous optimization and model correction scheme has been implemented to arrive at the optimal operating condition which satisfies the optimal productivity as well as the desired purity and recovery of products experimentally.

Pumping liquid metal at high temperatures up to 1,673 kelvin

Heat is fundamental to power generation and many industrial processes, and is most useful at high temperatures because it can be converted more efficiently to other types of energy. However, efficient transportation, storage and conversion of heat at extreme temperatures (more than about 1,300 kelvin) is impractical for many applications. Liquid metals can be very effective media for transferring heat at high temperatures, but liquid-metal pumping has been limited by the corrosion of metal infrastructures. Here we demonstrate a ceramic, mechanical pump that can be used to continuously circulate liquid tin at temperatures of around 1,473–1,673 kelvin. Our approach to liquid-metal pumping is enabled by the use of ceramics for the mechanical and sealing components, but owing to the brittle nature of ceramics their use requires careful engineering. Our set-up enables effective heat transfer using a liquid at previously unattainable temperatures, and could be used for thermal storage and transport, electric power production, and chemical or materials processing.

Optimization of startup and shutdown operation of simulated moving bed chromatographic processes

This paper presents new multistage optimal startup and shutdown strategies for simulated moving bed (SMB) chromatographic processes. The proposed concept allows to adjust transient operating conditions stage-wise, and provides capability to improve transient performance and to fulfill product quality specifications simultaneously. A specially tailored decomposition algorithm is developed to ensure computational tractability of the resulting dynamic optimization problems. By examining the transient operation of a literature separation example characterized by nonlinear competitive isotherm, the feasibility of the solution approach is demonstrated, and the performance of the conventional and multistage optimal transient regimes is evaluated systematically. The quantitative results clearly show that the optimal operating policies not only allow to significantly reduce both duration of the transient phase and desorbent consumption, but also enable on-spec production even during startup and shutdown periods. With the aid of the developed transient procedures, short-term separation campaigns with small batch sizes can be performed more flexibly and efficiently by SMB chromatography.

Optimization of reactive simulated moving bed systems with modulation of feed concentration for production of glycol ether ester

In this article, we extend the simulated moving bed reactor (SMBR) mode of operation to the production of propylene glycol methyl ether acetate (DOWANOL™ PMA glycol ether) through the esterification of 1-methoxy-2-propanol (DOWANOL™ PM glycol ether) and acetic acid using AMBERLYST™ 15 as a catalyst and adsorbent. In addition, for the first time, we integrate the concept of modulation of the feed concentration (ModiCon) to SMBR operation. The performance of the conventional (constant feed) and ModiCon operation modes of SMBR are analyzed and compared. The SMBR processes are designed using a model based on a multi-objective optimization approach, where a transport dispersive model with a linear driving force for the adsorption rate has been used for modeling the SMBR system. The adsorption equilibrium and kinetics parameters are estimated from the batch and single column injection experiments by the inverse method. The multiple objectives are to maximize the production rate of DOWANOL™ PMA glycol ether, maximize the conversion of the esterification reaction and minimize the consumption of DOWANOL™ PM glycol ether which also acts as the desorbent in the chromatographic separation. It is shown that ModiCon achieves a higher productivity by 12-36% over the conventional operation with higher product purity and recovery.

Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst

Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested.

Bayesian estimation of parametric uncertainties, quantification and reduction using optimal design of experiments for CO 2 adsorption on amine sorbents

Abstract Uncertainty quantification plays a significant role in establishing reliability of mathematical models, while applying to process optimization or technology feasibility studies. Uncertainties, in general, could occur either in mathematical model or in model parameters. In this work, process of CO2 adsorption on amine sorbents, which are loaded in hollow fibers is studied to quantify the impact of uncertainties in the adsorption isotherm parameters on the model prediction. The process design variable that is most closely related to the process economics is the CO2 sorption capacity, whose uncertainty is investigated. We apply Bayesian analysis and determine a utility function surface corresponding to the value of information gained by the respective experimental design point. It is demonstrated that performing an experiment at a condition with a higher utility has a higher reduction of design variable prediction uncertainty compared to choosing a design point at a lower utility.