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Recently renewed interest in the optimal design of sustainable processing systems has emerged as consequence of pollution issues and global climate changes. The replacement of hazardous industrial solvents widely used for azeotropic separations is clearly a challenging research area for new products design. However, as important as product design is, the design of the optimal processing configuration where the azeotropic separation will take place is also a key issue. As a matter of fact, the strong interaction between product and process design indicates that better optimal processing conditions can be attained by solving both problems simultaneously rather than sequentially. In the present work, we take advantage of this natural interaction for the optimal simultaneous design of both ionic liquids and an extractive distillation column for the high purity separation of the ethanol/water azeotropic mixture for deploying ethanol as a biofuel. The problem is formulated as a steady-state disjunctive mixed-integer nonlinear programming (MINLP) problem. The results indicate that new green solvents constitute a good replacement for hazardous solvents. Because ionic liquids are expensive solvents, it is worth it to explore the deployment of advanced optimization tools for profit maximization of sustainable processing systems. Through the use of the proposed MINLP formulation, improved ethanol/water separation configurations deploying ionic liquids were attained. Because ethanol features high purity, it can be used for biofuel applications.

Carbon capture has been recognized as an attractive alternative to reduce CO2 emissions. The most feasible technology that can be developed at a commercial-scale in a short-term period is CO2 capture by absorption since it is an end-pipe technology that can be installed in existing coal-based power plants and will not require retrofit of the power plant. The most studied CO2 capture process is absorption using monoethanolamine (MEA) and represents the benchmark solvent because of the favorable properties it has shown such as fast kinetics, high absorption capacity, good solubility in water, and low price. On the other hand, this solvent is susceptible to thermal and chemical degradation, and it is also corrosive. Nevertheless, the main drawback of this solvent is the energy consumption needed for solvent recovery (almost >90% of the plant’s operating cost). Ionic liquids (IL) are new alternative solvents for CO2 capture. Experimental results have shown that IL feature chemical and thermal stability, and good CO2 absorption capacity. In this work, a theoretical IL is used as physical solvent for developing a new flow-sheet of a CO2 capture plant. A techno-economic analysis was carried out to evaluate the feasibility of the proposed design. The results show that the IL-based plant features lower energy demand compared to a traditional MEA-based plant. Moreover, the dynamic analysis performed in this study provides insight on the degree of nonlinearity and the dynamics of the process, which are essential tools to design suitable control schemes. The results show that the plant can accommodate perturbations in the flue gas flow rate up to ±10% while meeting CO2 recovery and purity targets.

Nowadays there is a world concern on the impact and effect of large CO2 atmospheric concentrations on human health. Fossil‐fuel combustion processes in power plants are among the major contributors to this issue. Hence, it becomes important to develop new clean and sustainable processes aimed to reduce the amount of CO2 released to atmosphere by combustion processes in power plants. One of the best feasible manners to achieve this purposes lies in the use of a closed‐loop control system able to keep the amount of green‐house gases under specification even in the presence of unexpected scenarios. Of course, CO2 capture has been extensively researched in the past. However, in this regard the industrial practice has consisted in using Amines leading to sustainability and safety issues. Hence, it makes sense to seek for new and potentially environmental friendly process design to address CO2 reduction from power plants but applying a new type of sustainable stripping solvents. In this work we address the sustainable CO2 reduction issue from a process control point of view applying a previous design proposed by our research team based on the deployment of Ionic Liquids (IL) as potential green solvents and developing an efficient and decentralized multiloop control system. We demonstrate that the closed‐loop system is able to maintain the CO2 concentration levels under specification by testing in presence of several demanding scenarios. Overall, from an economic, sustainable and control point of view it looks feasible to replace the traditional amines‐based CO2 capture process by other alternatives based on the application of IL as potential green solvents. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3298–3309, 2016

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