Ben-Guang Rong

Design and synthesis of multicomponent thermally coupled distillation flowsheets

Abstract The design and synthesis of thermally coupled distillation flowsheets for separations of five-component mixtures are studied. Four types of possible configurations are identified when simple and complex columns are both considered in a flowsheet. A universal design procedure is developed for design of any types of the identified configurations based on the abstraction of the three basic units in the flowsheets. Two examples demonstrated that this shortcut design method can be used in design of any types of the identified multicomponent thermally coupled distillation flowsheets, as well as give very good initializations for rigorous simulation of such configurations. Moreover, with a proposed computer representation of all the types of the feasible configurations, a synthesis algorithm is developed for synthesizing of multicomponent complex distillation flowsheets with both simple and complex columns. It is practical by the proposed methods for optimal design of multicomponent distillation systems in an extended search space to include the complex distillation flowsheets for industrial problems.

The synthesis of thermally coupled distillation flowsheets for separations of five-component mixtures

Abstract The thermally coupled distillation flowsheets for separation of five-component mixtures are studied based on the total annual costs. Fourteen simple column sequences and some feasible thermally coupled configurations with side strippers and/or side rectifiers are considered. The costs of the flowsheets are calculated and compared for several real five-component mixtures with various relative volatility distributions and a wide range of feed compositions. Several heuristics are proposed for the synthesis of multicomponent thermally coupled distillation flowsheets.

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.

Techno-economic analysis of different pretreatment processes for lignocellulosic-based bioethanol production.

In this work, a method based on process synthesis, simulation and evaluation has been used to setup and study the industrial scale lignocellulosic bioethanol productions processes. Scenarios for pretreatment processes of diluted acid, liquid hot water and ammonia fiber explosion were studied. Pretreatment reactor temperature, catalyst loading and water content as well as solids loading in the hydrolysis reactor were evaluated regarding its effects on the process energy consumption and bioethanol concentration. The best scenarios for maximizing ethanol concentration and minimizing total annual costs (TAC) were selected and their minimum ethanol selling price was calculated. Ethanol concentration in the range of 2-8% (wt.) was investigated after the pretreatment. The best scenarios maximizing the ethanol concentration and minimizing TAC obtained a reduction of 19.6% and 30.2% respectively in the final ethanol selling price with respect to the initial base case.

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.

TRIZ-based creative retrofitting of complex distillation processes —An industrial case study

Publisher Summary This chapter discusses an integrated approach combining Theory of Inventive Problem Solving (TRIZ)-based theory, and thermodynamic analysis is proposed for the creativity support of the process retrofitting problem solving. Thermodynamic analysis could be applied to the search of potential retrofitting targets and possible solutions for further improvement. The presented approach and algorithm are applied for the retrofitting of the butadiene extractive distillation plant. When getting the optimal retrofit flowsheets, heat integration is carried out for the efficient use of energy in the proposed alternative flowsheets. Two optimal flowsheets have been obtained based on the different heat-matching strategies. One of the alternatives with the new structure and the heat-matching strategy is presented. Simulation results show that the saving of the consumption of steam utility for two optimal flowsheets are 23.7% and 27.7%, respectively as compared with the existing plant.

Methodology of conceptual process synthesis for process intensification

Abstract A systematic method based on conceptual process synthesis for process intensification is presented. Starting from the analysis of relevant physical and chemical phenomena, the various possible concepts and principles for the processing tasks are investigated. This includes the introduction of the new concepts and principles through the variations and manipulations of the key process phenomena. The various partial solutions for process and equipment intensification are then generated through phenomena-based reasoning. Next, the feasible conceptual process alternatives are synthesized by combining the generated partial solutions. The example for the intensification of the peracetic acid production process was demonstrated, which particularly illustrated the intensification of the conventional batch process to the on-site micro process through microreactor technology.

A conflict-based approach for process synthesis with wastes minimization

Abstract This paper presents a conflict-based analysis approach for process synthesis with wastes minimization for dealing with the conflicts of multi-objective nature in the early design stage. A three-level hierarchical procedure is proposed for carrying out the identification of waste sources, the generation of pollution prevention alternatives and mathematical optimization. It has been shown that the superstructure aimed at the wastes minimization can be systematically formulated on the basis of the proposed strategy. The proposed approach has an important potential for achieving a more efficient solution in the stage of mathematical optimization. The approach is illustrated by a case study: air-based direct oxidation process for the production of ethylene oxide.

Synthesis of Reactor/Separator Networks by the Conflict-based Analysis Approach

Abstract This paper presents a conflict-based analysis approach for the synthesis of reactor/separator superstructure towards the improvement of the quality and efficiency of the mathematical programming optimisation. A three-level hierarchical procedure is proposed for carrying out a combined method from the qualitative stage to the quantative optimisation stage. In the first stage, there is the systematic formulation of the superstructure on the basis of multi objective conflicts analysis and phenomena-relationship structure abstraction. It has an important potential for gaining a more efficient solution in the next stage of mathematical optimisation. The proposed approach is illustrated with the synthesis of the hydrodealkylation of toluene (HDA) process.