Recycling vs. reprocessing. Optimization of a gossypol production process

• Three processes to obtain gossypol from the cottonseed soapstock were compared.
• This study was conducted to increase product yield of base process.
• We analyzed two process design heuristics. Recycle vs. reprocess of exit stream.
• The results show that implementing a recycle obtained the maximum yields of product.
• However, reprocessing the exiting stream exhibits the best economical performance.

Three processes to obtain GAA from the soapstock residue of oil refineries were compared in this work. The first process is the originally proposed by Dowd and Pelitire (2001. Ind. Crops Prod. 14, 113) in which the mother liquor from the last crystallization step still contains an appreciable amount of gossypol which is lost as a process residual stream. The second process recycles the mother liquor to the hydrolysis first step of the process, following the heuristic of the traditional process design procedure by Douglas (1988. Conceptual Design of Chemical Processes. McGraw Hill, New York, NY), which increases product yield. While the third process adds a new downstream processing line to reprocess the mother liquor. This last alternative renders a slightly lower product yield than Process 2 but requires a smaller investment cost, exhibiting the best economic performance.The alternative of incorporating a recycle to reprocess unreacted material (in this case the bound gossypol present in the crystallization mother liquor) is the usual approach in traditional process design. However, in this particular study case, it does not succeed in rendering the process alternative with the best economic performance: the recycle stream flow impacts on the equipment sizes, increasing investment cost far beyond the alternative that adds smaller units to reprocess the mother liquor stream.