Sandoz Crop Protection Corporation, Jefferson County, TX
Herbicide, Methazole


This was an entirely new process that yielded a very high purity product with extremely low toxicity. The herbicide is temperature sensitive. Temperature must be carefully controlled or the prod­uct turns brownish and loses its efficacy. Most dryers had to be ruled out because they use elevated temperatures. The particles tend to stick together, so the product needs continuous and gentle agitation, but because the crystals are subject to dusting, it was necessary to minimize particle attrition. Tests showed that single or double-cone batch drying under vacuum would be too slow to handle the proposed commercial production. Paddle and screw type dryers caused too much product dusting and attri­tion. Sandoz selected a Wyssmont rotary tray dryer. The system uses a heated nitrogen atmosphere that is recycled. The drying system has met the design rate on throughput and all product quality specifications: purity, dryness, caking, dusting, and unifor­mity. The trays can be easily cleaned between production runs. The unit requires minimal operator· attention and simple maintenance procedures.


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