Ethanol is attracting the attention of researchers because of its potential in reducing the dependence on crude oil together with the possible reduction in the pollution associated with the combustion process. The ethanol dehydration process is significant in terms of its production cost. Recently, new distillation sequences have been proposed for the separation of pure ethanol from the fermentation broth. Extending the concept of thermally coupled structures and column sections recombination, already successfully applied to ideal mixtures, it was possible to generate new distillation sequences for azeotropic mixtures. Those configurations are proven to exhibit lower energy consumption together with reduced capital cost compared to the classical sequence proposed in the literature. The aim of this work is the study of the controllability properties under closed-loop operation. Simulation results indicate that the presence of a side stream in extractive distillation sequences does not necessarily provide operational disadvantages; additionally, results also suggest that control properties are ruled by the kind of solvent used.

BACKGROUND Bioethanol is a green fuel considered to be a sustainable alternative to petro‐derived gasoline. The transport sector contributes significantly to carbon dioxide emission and consequently has a negative impact on the air quality and is responsible for the increase of the greenhouse effect. The availability of environment‐friendly and economical fuels is a worldwide priority. The separation process is a significant technology in the production of fuel grade ethanol in terms of both operating and capital costs. In the present work an alternative distillation sequence for bioethanol separation is presented. The steady state performance and the dynamic beavior are analyzed compared with the classical configuration reported in the literature. RESULTS Ethanol–water azeotropic separation represents a challenge for bioethanol purification. Usually a three column sequence is used to obtain fuel grade bioethanol by extractive distillation. In order to reduce bioethanol purification cost a two column separation sequence is proposed. This configuration shows a 10% saving in capital costs together with higher ethanol recovery and better control properties compared with the classical three column sequence. CONCLUSIONS Based on the steady state and dynamic results obtained, the two‐column configuration represents a valid alternative to the classical configuration for the separation of bioethanol. © 2014 Society of Chemical Industry

BACKGROUND: Butanol produced from fermentation has attracted the interest of research groups because its physicochemical properties show several enhancements over bioethanol. Recent studies have proposed alternative methods to separate and purify biobutanol from a fermentation broth. These alternatives offer energy and economic savings; in addition, a reduction in environmental impact is observed. However few studies have analyzed the control properties of the process which involves separation of an acetone-butanol-ethanol (ABE) mixture.

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In this work, we present the multiobjective optimization of the Siemens Process, the Intensified FBR Union Carbide Process, and the Hybrid Process (the three processes to obtain solar-grade silicon), including considerations of safety, economic, and environmental impact at the design stage of the process. Safety is considered through the individual risk index, the economy through the return on investment, and the environmental impact using the eco-indicator 99. The design of the Siemens Process turned out to be the one that showed the best safety, profitability, and environmental indexes, despite having the lowest solar-grade silicon production capacity, a fourth of that of the Hybrid Process. The results showed similar profitability values for the Hybrid and Siemens processes. In general, because of the high demand of the product of interest and under the premise of a safe process, the Hybrid Process can be chosen as a promising option for its industrial implementation.

Alkoxysilanes are silicon compounds containing a Si-OR bond. The applications of tetraalkoxysilanes cover a wide range depending if the Si-OR bond remains intact or is hydrolyzed. Currently, tetraethoxysilane (TEOS) is the most prominent derivative of such silicon compound family. The best known and used method of synthesis of TEOS is the esterification reaction of SiCl4, following the old Von Ebelman’s route (1846). Tetramethoxy- and tetraethoxysilane are obtained by a technology developed in the 1990’s involving the catalyzed direct synthesis of silicon metal and either methanol or ethanol. However, there is few information about novel technologies to produce TEOS, either improved current technology or proposed new approaches. In this work, the reactive distillation (RD) is suggested to produce TEOS as an intensified technology. In general, the concept of process intensification may overcome the traditional process, since it allows design technology with reduction on equipment size, improvement in energy and mass transfer, and reduction in capital cost. Therefore, this work will approach TEOS production by means of two systems, the conventional reaction including the product separation (reaction/separation) and a reactive distillation. In order to evaluate both ways to produce TEOS, the two systems were evaluated considering the total annual cost (TAC) and return of investment (ROI) as economic indexes and the Eco-indicator 99 as an environmental index. As a result, the reactive distillation shows better performance as concern to TAC values; however, when purities above 99.5% wt are obtained, the reaction/separation system overcomes the RD as concern to ROI values. Moreover, when the environmental impact is measured, the RD showed a bigger impact near 30% in comparison with the reaction/separation system.

Thermally coupled distillation columns (TCDC) are used to reduce energy requirements on the separation of liquid mixtures, which also reduces the environmental impact. The Petlyuk column is one of the TCDC with the highest reductions on heat duty. The use of distillation trains with Petlyuk columns is proposed to purify a multicomponent hydrocarbon mixture. Different sequences are studied, varying the location and number of Petlyuk columns to achieve separation of the components. Studied sequences are then optimized and compared in terms of energy requirements, environmental impact, and dynamic performance. The stream on which the component with the highest feed composition is separated has a great influence on the total heat duty and environmental impact. Nevertheless, the correlation between location and number of Petlyuk columns in the sequences and their control properties is low.