Membrane Process for solvent Reclamation and Reuse

Many commercial hydrophilic solvents form azeotropes or have vapor-liquid equilibrium (VLE) pinch points with water, which making solvent recovery by conventional distillation difficult. Solvents that form such azeotropes or have such pinch points include isopropyl alcohol (IPA), acetone, methyl ethyl ketone (MEK), ethyl acetate, ethanol, butanol and tetrahydrofuran. Molecular sieve drying is possible, but requires intensive energy consumption for vaporization of the solvent/water mixture, and is generally not economical for situations where water concentration is more than 5 wt%. The process to be developed in this project uses pervaporative dehydration to reclaim and reuse solvents on-site. Membranes newly developed at MTR will be used. Compared to conventional membranes, the new membranes have superior thermal and chemical stability, and can deliver better solvent/water separations. The membrane modules will be adapted for counter-flow sweep operation to further extend the range of water concentrations that can be separated economically. In the Phase I project, the feasibility of the process will be determined, using IPA as a model solvent. IPA was chosen because it is widely used as a drying agent in the chemical, semiconductor, and electronics industries, and in the production of precision metal parts. Currently, the spent IPA is disposed of as hazardous waste, at a cost of about $20/gal. Virgin, high-purity IPA costs $10/gal, so the total cost of IPA used as a cleaning/drying agent is in the range of $30/gal. A considerable economic and environmental driving force exists to recover and reuse the IPA solvent. By the end of Phase I, at least one potential customer interested in participating in a Phase II IPA field test will be identified. Following successful field trials in Phase II, a commercialization plan will be developed to bring the new membrane technology to market. IPA recovery is our introductory target application, but once developed and demonstrated, the technology will be applicable to a wide variety of similar solvent recovery applications.