![]() Today, CPIs produce around 10 5 different molecules at capacities ranging from less than one kilo to 300 million tons per year ( Amundson, 1988). The combination of mass and energy balances, fluid phase equilibria, and rate processes offer a generic methodology, which can, in principle, be applied to any type of molecule in the feed mixture for a rational design ( Noble and Agrawal, 2005). Process Systems Engineering toolboxes indeed offer the possibility of quickly simulating and investigating the performances of a separation system (most often including a set of unit operations). Thanks to intense research efforts and industrial practice and feedback, a large number of separation processes can today be rationally designed, scaled, and controlled ( Seider et al., 2009). Another indication of the importance of separation processes comes from the fact that they are classically considered to represent 60 to 80% of the CAPEX (equipment) and OPEX (energy requirement) of production costs in Chemical Process Industry (CPI) plants ( Humphrey and Keller, 1997). The spectacular increase of cost with dilution is explained as being a result of the increasing complexity and cost of separation processes in the downstream purification part. The importance of separation processes is highlighted by the so-called Sherwood plot ( Sherwood et al., 1975), which links the degree of dilution of a target molecule at the outlet of a production process to its price. With the emergence of chemical engineering concepts in the late nineteenth century, and the spectacular expansion of chemical plants after WWII driven by the oil and gas industry, separation processes are today classically considered as one of the pillars of chemical engineering ( Peppas and Harland, 1989). Depending on the classification type, a variety of 20 to 100 operations can be listed today, including mechanical, thermal, auxiliary phase, and membrane separation processes ( King, 1980). Through the ages, a large portfolio of techniques has gradually been invented and developed for multiphase, solid, gaseous, and liquid mixtures. For instance, silver extractions from ore thanks to mercury or alcohol dehydration with desiccant solids have been described in documents dating back from as early as the fifteenth century ( Aris, 1977). ![]() Thermal processes, such as evaporation or distillation, have been favored for a long time, but extractions based on an auxiliary phase (i.e., the use of a dedicated gas, liquid, or solid compound in order to generate a separation effect) have also been explored and used later on. Early target operations, such as salt recovery from brine or seawater by evaporation, ore treatment for metal extraction (e.g., iron, silver, lead, mercury, etc.), and the synthesis of chemical products like alum for the textile industry, have been reported for centuries 1. Separation processes have continuously been used and improved by mankind for the production of food, various products, and energy ( Hougen, 1977).
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