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Evonik Industries currently loses approximately 50 tons of polyether product to wastewater washes annually. Evonik has requested an industrially viable solution to maximize the recovery of the lost product in the current process. It was required that the solution have a one year payback period, and be in compliance with current regulatory policies. Literature sources showed that salt is a commonly used agent to force the separation of polyether-water mixtures. Using this information, a method was developed using a salt already present in the process to induce a phase separation and to recover the polyether. An empirical multilinear refractive index model was developed to determine the polyether content in treated samples, while thermogravimetric analysis (TGA) was used to determine the salt content. A series of preliminary tests followed trends observed in academia, which claimed that salt composition and temperature had an effect on the amount of polyether recovered. A design of experiment (DoE) was performed on three classes of Evonik’s polyether to determine the optimum conditions for product recovery on a bench scale. Using the optimal recovery region from the DoE, a scale up was performed, and two other tests were performed to examine the effect of reducing the water used in the washes. In both cases, 88-99% of the polymer could be recovered, although the reduced-water trials required an order of magnitude less salt than the full-wash trials. From these results, it is expected approximately $130,000 of product could be recovered annually with an initial investment of $46,500.
Chemical and life science engineering, Polyether, Salt-Induced Phase Separation, Refractive Index, Polymer-Water System
Chemical Engineering | Engineering
B. F. Gupton
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