Optimal design and scheduling of ecofriendly process for the production of natural tocopherols present in residue from the vegetable oil refinery

Abstract

This paper addresses the optimal design of molecular distillation (MD) process for the treatment of a residue of the edible oils refining industry. This work focuses on optimizing the number of units and their size, performing the scheduling of the separation tasks assigned to each unit with the objective of treating a residue with the minimum number of process equipment at a specific size to process a certain annual production of ODD (Oil Deodorization Distillate). The MD is considering clean technology because only consumption electric energy and not generate highly polluting waste. The stream of ODD has a high organic contaminant load. This requires more than one distillation stage to obtain tocopherols as a product (four stage for this study case). Here, to evaluate the process with minimum number stage a first screening was done using the traditional model of constant size factors, but afterwards the best candidate alternative was optimized as regards to the flow rates to be recycled to previous stages. The objective is to add value to a residual stream of oil refining processes, resorting to MD technology, given that MD is a very expensive technology, and in this particular case where its size is small, limited by manufacturer. For all scheduling alternatives analyzed, the best economic performance yields a Profit of 381,360 $/yr with two MD equipment and optimizing the material balances and recycles. This process is with an assignment of tasks to units that yields one larger equipment to perform the first three separation stages, and a quite small equipment to perform the last separation stage. This process has even better economic performance than the same process without reflux recirculation optimization. The process with one unit yielded technically infallible results. The process with three units showed less favorable economic performance.