Massimiliano Errico

Modified simple column configurations for quaternary distillations

Abstract Distillation is the most energy demanding, capital intensive and widely used separation method. For quaternary distillation, the conventional simple column configurations employ three columns to achieve four products with any specified purity. In this paper, the modified simple column configurations are studied which use two columns to accomplish four-component separations with any specified purity. The modified simple column configurations have the significant process intensification feature that they use less number of columns and heat exchangers. To study the performance of the modified simple column configurations different four-component mixtures with different feed compositions were analyzed. The performance was studied in terms of energy, capital cost saving and column sections function. It was demonstrated that for the composition cases considered the proposed configurations have similar or better energy performance than the traditional simple column sequences, however significant capital cost reductions are achieved in all the cases studied.

The importance of the sequential synthesis methodology in the optimal distillation sequences design

Abstract The sequential design method is presented as a complementary tool of the systematical synthesis procedure that allows to define a clear connection among the different types of distillation column sequences. In particular, the connection with the simple column subspace is considered, since this subspace represents the comparison reference for all the alternatives considered. The sequential design procedure, based on the correspondence between the functionality of the columns section among the simple columns and the derived sequences, is compared with a mathematical based optimization algorithm. The separations of a four-component near ideal mixture and the azeotropic ethanol–water mixture are considered as case studies and the designs obtained applying both methods have been compared. The results confirmed that the sequential design method is a fast and reliable tool in the optimal design of the column sequence.

Synthesis and design of new hybrid configurations for biobutanol purification

Abstract The development of new technologies for biobutanol production by fermentation has resulted in higher butanol concentrations, less by-products and higher volumetric productivities during fermentation. These new technology developments have the potential to provide a production process that is economically viable in comparison to the petrochemical pathway for butanol production. New alternative hybrid configurations based on liquid–liquid extraction and distillation for the biobutanol purification were presented. The alternatives are designed and optimized minimizing two objective functions: the total annual cost (TAC) as an economical index and the eco-indicator 99 as an environmental function. All the new configurations presented reduced the TAC compared to the traditional hybrid configuration, in particular a thermally coupled alternative exhibited a 24.5% reduction of the TAC together with a 11.8% reduction of the environmental indicator. Also intensified sequences represented a promising option in the reduction of the TAC but with some penalty in the eco-indicator.

Influence of the reaction conditions on the enzyme catalyzed transesterification of castor oil: a possible step in biodiesel production

The identification of the influence of the reaction parameters is of paramount importance when defining a process design. In this work, non-edible castor oil was reacted with methanol to produce a possible component for biodiesel blends, using liquid enzymes as the catalyst. Temperature, alcohol-to-oil molar ratio, enzyme and added water contents were the reaction parameters evaluated in the transesterification reactions. The optimal conditions, giving the optimal final FAME yield and FFA content in the methyl ester-phase was identified. At 35°C, 6.0 methanol-to-oil molar ratio, 5wt% of enzyme and 5wt% of water contents, 94% of FAME yield and 6.1% of FFA in the final composition were obtained. The investigation was completed with the analysis of the component profiles, showing that at least 8h are necessary to reach a satisfactory FAME yield together with a minor FFA content.

A deterministic algorithm for the synthesis of maximum energy recovery heat exchanger network

Abstract This paper presents a general mathematical optimization model and the related deterministic algorithm for synthesizing heat-exchanger networks (HEN). The methodologies commonly used to solve a HEN problem are based on heuristic methods. These algorithms reach a presumed best solution with respect to the investigated set of process streams, whereas our approach determines the optimal configuration. In this paper the proposed method is applied to the solution of a few simple HEN synthesis problems and the results are compared with those obtained utilizing heuristic or meta-heuristic methods. HENs problem is represented by a general mathematical model that can be applied to small and medium sized problems and is solved by using a deterministic method with a reasonably brief computation time. Notably, this approach can represent a unique general model of a wide class of heat-exchanger networks, independently of their specific physical configuration.

Design and optimization of modified non-sharp column configurations for quaternary distillations

Abstract The possible structural changes of a non-sharp quaternary distillation configuration are considered. For the reference configuration composed of four columns, different alternatives are generated following the process intensification principle to reduce the number of equipment units. The intensified systems with three or two columns are obtained, including the dividing wall columns. Simulator Aspen Plus V8.0 was used to design and simulate all the systems for a hydrocarbon mixture. The intensified structures showed relevant energy savings compared to the reference case. The most promising alternatives were optimized by means of the differential evolution (DE) method minimizing the total annual cost (TAC). It was observed that the intensified systems were able to reduce both the energy consumption and the number of equipment units. The best intensified system has a TAC of 11.98% lower than the optimized reference case.

Alternative Hybrid Liquid-Liquid and Distillation Sequences for the Biobutanol Separation

Abstract Recent technologies for biobutanol production by fermentation have resulted in higher final biobutanol concentrations, less fermentation by-products and higher volumetric productivities during fermentation, together with less energy intensive separation and purification techniques. These new technology developments have the potential to provide a production process for biobutanol that is economically viable in comparison to the petrochemical pathway for butanol production. This study compares four different possible process designs for purification of biobutanol by means of a multiobjective optimization process having two objective functions: the total annual cost (TAC) as an economical function and the associated eco-indicator 99 as an environmental function.

New intensified distillation systems for quaternary Petlyuk configuration

Abstract While dividing-wall column for ternary Petlyuk configuration has received wide applications in industries, the dividing-wall column for quaternary Petlyuk configuration has not reached the same applications due to its complexity in both design and control. In this work, the synthesis on the alternative intensified distillation systems than Petlyuk configuration for four-component distillation was investigated. First, the simple column configuration for the separation sequence of Petlyuk configuration is presented. Then four strategies are introduced to change the structure of the simple column configuration in terms of both condensers/reboilers and column sections. These strategies can be used to synthesize the alternative intensified configurations from the simple column configuration of the separation sequence. The objective of this work is to give the synthesis method to generate the new intensified distillation systems for quaternary Petlyuk configuration. In total, five new alternative intensified systems are obtained each with only two columns. The alternative intensified systems are amenable to be easier in both design and control due to the simplicity in the structures. The synthesis method together with the new generated alternative configurations are presented in this work. The numerical design and optimization, as well as dynamics and control of these new alternative configurations are underway.

Optimal synthesis and design of extractive distillation systems for bioethanol separation: from simple to complex columns

Abstract Bioethanol has been considered as a green fuel and a valid alternative to reduce the dependence on fossil distillates. The development of an optimal separation process is considered as a key element in the design of an efficient process able to be cost effective and competitive. Despite many separation techniques are today available, distillation is up to now the frontrunner technology in most of the plants. In particular extractive distillation is considered as an energy efficient method to produce pure ethanol overcoming the purity limitations imposed by the water-ethanol azeotrope. The subspace of simple distillation configurations was generated considering the possibility to employ partial or total condensers to transfer the non-product mixtures between the columns, moreover different numbers of columns are considered. Once the most promising sequences are obtained, the complex columns are investigated. The complex column subspace is generated introducing one or more thermal couplings and considering the possibility to intensify the process combining the column sections performing the same separation task. All the configurations considered, simulated by means of Aspen Plus V 7.3, are compared considering the total condenser and reboiler duty as energy index. The capital costs and the solvent consumption are also taken into account in the final selection. Among all the complex configurations considered the two-column sequence can reduce the capital cost above 10% compared to the best simple column sequence. The performances for different solvents are also taken into account in the process alternatives comparison.

Castor Oil Transesterification Catalysed by Liquid Enzymes: Feasibility of Reuse under Various Reaction Conditions

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