BOC Edwards, Wilmington, Mass., completed the design of an ultrahigh purity ammonia-gas production system using a low-grade liquid ammonia feedstock. The system is capable of producing up to 150 tons annually of Grade 6.0+ liquid ammonia having a moisture content of less than 0.3 ppm. The system uses a vapor phase transfer operation for removal of metallic impurities and oil, which are common contaminants in raw anhydrous ammonia streams. Moisture is removed using a chemical/mechanical dryer unit. While the system was designed for large-scale plant production, the same design can be used for lower flow rates in end-user plant production schemes.