A multi-objective genetic algorithm for the design of pressure swing adsorption

Pressure Swing Adsorption (PSA) is a cyclic separation process, more advantageous over other separation options for middle scale processes. Automated tools for the design of PSA processes would be beneficial for the development of the technology, but their development is a difficult task due to the complexity of the simulation of PSA cycles and the computational effort needed to detect the performance at cyclic steady state. We present a preliminary investigation of the performance of a custom multi-objective genetic algorithm (MOGA) for the optimisation of a fast cycle PSA operation, the separation of air for N2 production. The simulation requires a detailed diffusion model, which involves coupled nonlinear partial differential and algebraic equations (PDAEs). The efficiency of MOGA to handle this complex problem has been assessed by comparison with direct search methods. An analysis of the effect of MOGA parameters on the performance is also presented

Design acceleration in chemical engineering

Nowadays, Chemical Engineering has to face a new industrial context with for example: the gradually falling of hydrocarbon reserves after 2020-2030, relocation, emerging of new domains of application (nano-micro technologies) which necessitate new solutions and knowledges… All this tendencies and demands accelerate the need of tool for design and innovation (technically, technologically). In this context, this paper presents a tool to accelerate innovative preliminary design. This model is based on the synergy between: TRIZ (Russian acronym for Theory of Inventive Problem Solving) and Case Based Reasoning (CBR). The proposed model offers a structure to solve problem, and also to store and make available past experiences in problems solving. A tool dedicated to chemical engineering problems, is created on this model and a simple example is treated to explain the possibilities of this tool

A Comprehensive Study of Sequential Simulated Moving Bed: Purification of Xylo-oligosaccharides and fructose-glucose

Chromatographic separation is a promising alternative for separation and purification of sugars in industry. Simulated moving bed (SMB) technique has been proven as an efficient chromatographic separation method due to its enhanced productivity and purity, reduced solvent consumption, convenient operating control, and improved separation performance for some systems with low resolution and selectivity. The sequential simulated moving bed (SSMB) is a modification of the conventional SMB process, which currently has some applications for sugar separation due to its low solvent consumption. This work mainly investigates the design strategy of the innovative SSMB process and explore its advantages and disadvantages over the SMB process based on the xylo-oligosaccharides (XOSs) and fructose-glucose systems. SSMB separation of XOSs, a functional food additive in the form of a oligomeric saccharide, was firstly conducted. DOWEX MONOSPHERETM 99/310 resin ionized with K+, which has better selectivity compared with Ca2+ and Na+ was used as the stationary phase.Breakthrough experiments showed that XOSs and the two major industrial impurities, xylose and arabinose, all exhibit linear isotherms. Transport-dispersive (TD) model parameters were determined by pulse experiments carried out at various flowrates. Finally, both the averaged and individual parameters of XOSs and XOS2-XOS7 were obtained. Lab-scale SSMB experiments and the corresponding simulations were carried out to validate the acquired TD model parameters and adsorption isotherms. After that, in order to investigate the optimal operating conditions of this process, the multi-objective optimizations were carried out for three cases with various objectives and constraints. It was found that, for a given SSMB unit, there exist a pareto curve for simultaneous maximization of purity and unit throughput. The flowrate ratios (m values), however, exhibit some trends that are different from those of conventional SMB and cannot be explained by the direct use of Triangle Theory with averaged m values. According to the literature, the fructose-glucose system is representative and have linear isotherms over a wide concentration range, which makes it an excellent example system to conduct some basic analysis and performance prediction. Therefore, the multi-objective optimization of SMB and SSMB processes was conducted and compared based on the fructose-glucose system. The results show that the solvent consumption of SSMB is always less than that of SMB unit

A Comprehensive Study Of Esterification Of Free Fatty Acid To Biodiesel In a Simulated Moving Bed System

Simulated Moving Bed (SMB) systems are used for separations that are difficult using traditional separation techniques. Due to the advantage of adsorption-based chromatographic separation, SMB has shown promising application in petrochemical and sugar industries, and of late, for chiral drug separations. In recent years, the concept of integration of reaction and in-situ separation in a single unit has achieved considerable attention. The simulated moving bed reactor (SMBR) couples both these unit operations bringing down the operation costs while improving the process performance, particularly for products that require mild operating conditions. However, its application has been limited due to complexity of the SMBR process. Hence, to successfully implement a reaction in SMB, a detailed understanding of the design and operating conditions of the SMBR corresponding to that particular reaction process is necessary. Biodiesel has emerged has a viable alternative to petroleum-based diesel as a renewable energy source in recent years. Biodiesel can be produced by esterification of free fatty acids (present in large amounts in waste oil) with alcohol. The reaction is equilibrium-limited, and hence, to achieve high purity, additional purification steps increases the production cost. Therefore, combining reaction and separation in SMBR to produce high purity biodiesel is quite promising in terms of bringing down the production cost. In this work, the reversible esterification reaction of oleic acid with methanol catalyzed by Amberlyst 15 resin to form methyl oleate (biodiesel) in SMBR has been investigated both theoretically and experimentally. First, the adsorption and kinetic constants were determined for the biodiesel synthesis reaction by performing experiments in a single column packed with Amberlyst 15, which acts as both adsorbent and catalyst. Thereafter, a rigorous model was used to describe the dynamic behaviour of multi-column SMBR followed by experimental verification of the mathematical model. Sensitivity analysis is done to determine robustness of the model. Finally, a few simple multi-objective optimization problems were solved that included both existing and design-stage SMBRs using non-dominated sorting genetic algorithm (NSGA). Pareto-optimal solutions were obtained in both cases, and moreover, it was found that the performance of the SMBR could be improved significantly under optimal operating conditions

Advances in simulated moving bed : new operating modes : new design methodologies and product (FlexSMB-LSRE) development

Tese de doutoramento. Engenharia Química e Biológica. Faculdade de Engenharia. Universidade do Porto. 200

Continuous chromatographic processes with a small number of columns: Comparison of simulated moving bed with Varicol, PowerFeed, and ModiCon

The Simulated Moving Bed process and its recent extensions called Varicol, PowerFeed and ModiCon are studied, in the case where a small number of columns are used, i.e. from three to five. A multiobjective optimization approach, using genetic algorithms and a detailed model of the multicolumn chromatographic process, is applied to optimize each process separately, and allow for comparison of the different operating modes. The non-standard SMB processes achieve better performance than SMB, due to the availability of more degrees of freedom in the operating conditions of the process, namely the way to carry out asynchronous switches for Varicol, and the different flow rates and feed concentration during the switching interval for PowerFeed and for ModiCon, respectively. We also consider the possibility of combining two non-standard operating modes in a new hybrid process, and evaluate also in this case the possible performance. Finally, a critical assessment of the results obtained and of the potential for practical implementation of the different techniques is reporte

Optimization of Chiral Separation of Nadolol by Simulated Moving Bed Technology

Simulated Moving Bed (SMB) technology has gained increasing attention as one of the most powerful techniques for chromatographic separations due to its cost-effectiveness and efficiency. Application of SMB technology is especially important in the pharmaceutical industry for production of enantiopure drugs, as required under strict FDA regulations, to avoid possible adverse effects of racemic drugs. In this study, the performance of the SMB process in separation of racemic nadolol on a perphenyl carbamoylated beta cyclodextrin (β-CD) stationary phase was investigated. The equilibrium dispersive model coupled with bi-Langmuir adsorption isotherm and lumped kinetic approximation, constitute the mathematical model used to simulate the dynamic behavior of SMB. Multi-objective optimization was carried out using a robust state-of-the-art optimization technique, non-dominated sorting genetic algorithm (NSGA). Two optimization problems were solved to simultaneously maximize productivity and purity of the product and minimize consumption of desorbent. The generated Pareto optimal solutions showed that selection of operating conditions can significantly affects the performance of SMB to meet the desired objectives

Compact SMB chromatography for binary separation

A thesis submitted for the degree of Doctor of PhilosophyThis thesis consists essentially of theoretical and experimental developments in the field of continuous chromatography using small-scale units. Continuous chromatographic separation processes based on the Simulated Moving Bed (SMB) technology were first patented and applied in 1961 for a large number of separations in the petrochemical industry and later for sugar separation. However, in the last two decades,due to the patent expiration, the process has been gaining great interest in the separation/purification of products in fine chemical and pharmaceutical industries. The conventional SMB comprises several identical columns which are serially connected in either a closed- or open-loop configuration. In order to simulate the movement of a solid bed in opposite direction to the fluid, the positions of the input and output streams are shifted downstream by one column, at fixed intervals, in the direction of fluid flow. With the development of new and efficient equipment and stationary phases, several new schemes of operating that differ from the conventional one have emerged. These include new concepts such as Varicol, ModiCon and PowerFeed processes, which rely on the periodic modulation of certain process parameters during the switching interval to enhance the efficiency of the separation. These advances are pushing the trend for units with a small number of columns, since the overall setup is more economical. However, when these newly schemes are applied in practice the process becomes more complex, because of the increased degrees of freedom that must be optimized. It is also less robust and more difficult to operate because it is more demanding on hardware. This additional complexity requires highly versatile SMB equipment, advanced optimization tools and robust control procedures. Experimental tools to experimentally reproduce the periodic state of multicolumn countercurrent chromatography with just one column are developed; they are economic and fast methods of experimentally exploring different column configurations and cyclic operation policies,ideally suited for applied research studies but may also be useful in the early stages of development, optimization, and validation of a new chromatographic separation. The feasibility of the proposed single-column system is experimentally demonstrated for several different column configurations, which include both synchronous and asynchronous port switchings and flow modulated schemes. Following the potentialities of these new operating schemes, a novel SMB system for binary separation that employs only two-columns is developed. The designed two-column process uses both the port switching and the flow rates modulation procedure. The process is very versatile since the cycle itself is optimized and adapted to the difficulty of the separation and process specifications. Furthermore, a simplified extension of the two-column setup which relies on a minimum pump number configuration and on a uniform flowrate scheme is built-up; additionally a further development on these simplified setup is applied which effectively enhances the process with only the cost of a small increase on the setup equipment. Potentialities of this new unit are illustrated comparing it to setups using the same amount of stationary phase.Fundação para a Ciência e Tecnologia (FCT/MCTES