Semicontinuous processes with chemical reaction

Thomas A. Adams, University of Pennsylvania


Semicontinuous distillation has been proposed as an alternative for performing multiple separations using a single distillation column, using a design strategy that combines elements of both traditional batch and continuous schemes. This dissertation expands upon the semicontinuous concept, exploring new and unique processes using semicontinuous principles. In particular, the integration of reaction into the system is examined, such as reaction in an auxiliary unit, inside of a middle vessel, or within the column itself. In addition to semicontinuous distillation, the newly postulated column operations include semicontinuous reactive distillation and semicontinuous reactive liquid-liquid extraction. These processes are examined using case studies for the production of ethyl lactate from ethanol and lactic acid, the production of 2,4-dimethyl-1,3,dioxolane from acetaldehyde and propylene glycol, and the recovery of dilute 1,3-propanediol from an aqueous fermentation broth. Rigorous simulations and economic analyses have been performed for these processes where the feasibility, controllability, operability, and profitability are examined in comparison with traditional alternative configurations. Custom software and process models were developed to facilitate the simulation of these unique designs. Due to their hybrid system characteristics, several new optimization algorithms have been proposed and explored for quality and speed. The proposed systems are shown to be economically preferable to traditional batch or continuous schemes for a wide range of production rates, due to the large reduction in capital expenses. Control systems are designed to ensure that weeping and flooding are prevented in the distillation columns throughout the highly dynamic cycles. A single column is used for multiple separations simultaneously, multiple separations in sequence, and even to cycle between vapor-liquid distillation and liquid-liquid extraction operations. Thus, semicontinuous applications, particularly when intensified with reaction, are feasible and economically-preferred choices for a wide variety of process applications.

Subject Area

Chemical engineering

Recommended Citation

Adams, Thomas A., "Semicontinuous processes with chemical reaction" (2008). Dissertations available from ProQuest. AAI3309385.