Study of Pilot Plant Acetone Use Reduction

Rohm and Haas Electronic Materials made a commitment to reduce acetone usage by 10% site-wide by 2006. Although this goal has already been reached, options for reduction need to be explored continuously. Reductions were made in several areas of the Raw Materials Pilot Plant, where acetone is used as a primary cleaning solvent. The Pilot Plant uses fresh acetone after every batch for all cleanouts and qualifications. The goal of this project was to reduce the amount of acetone used for cleaning. This involved first targeting the areas where the potential for reduction was the greatest. Starting with a general mass balance it was determined that cleanout acetone accounts for 55% of the total amount of acetone used, and vessel qualifications were found to account for 14% of the total acetone usage. The cleanout acetone was used to clean a filter press unit (to remove solids from the filter cloth) and to clean the reaction vessels. Measurement of filter press cleanout acetone showed that it was possible to recycle the same acetone to cleanout the filter press up to 4 times after a specific polymer was produced, resulting in 75% reduction. The acetone used to clean the reaction vessels could not be simply recycled. This is because it picked up the remaining traces of batch solvent. The acetone also dissolves any polymer material remaining in the vessel. A review of the process indicated that the acetone volume used per cleanout could not be reduced directly. It was decided that the acetone used for cleaning the reaction vessels and the filter press had to be distilled to a specified purity for reuse. Trials were performed to confirm the distillation effectiveness. Further investigation confirmed that a simple flash distillation using the exiting equipment was adequate, thus saving on capital cost and floor space. Vessel qualification is a procedure to consistently make high quality product and minimize offgrade material. The Pilot Plant cleans each of the reaction vessels in between products to check for metals contamination. The vessels and associated piping are rinsed with acetone. Samples of acetone are collected at various stages of the cleaning (qualification) process and analyzed for metals to determine if the vessel is qualified (i.e., clean enough) to proceed with the batch. If the metals content in acetone is too high, the qualification process is repeated until the metals levels are low enough to proceed with the next batch. To reduce the use of acetone the entire qualification process was reviewed. This included evaluating whether a qualification is necessary for every product, and also whether alternate cleaning methods could be used. This paper will discuss the work done and the results obtained. The project was successful in that it helped the company exceed its acetone use reduction commitment, while potentially saving over $50,000 per year based on the current acetone purchasing and disposal costs.

Acknowledgment: The authors would like to acknowledge the support from Rohm and Haas Electronic Materials, and from the UNH Pollution Prevention Internship Program. We would also like to thank the staff at Rohm and Haas for their help in the project. Special thanks to Jeff Upton at Rohm and Haas for his input in the project and in writing the abstract.