How does jet milling compare with other methods of grinding such as a ball mill or a hammer mill?
Well designed, high speed mechanical mills can grind some friable materials into the low micron size range but wear and product contamination is a serious problem as is attritional heat. Practically, the high speed mechanical mill (hammer etc. mill) cutoff is 200 mesh with a typical mid range of 80 mesh. Abrasive products will seriously erode most hammer mills adding metallic contamination to the product. Materials that degrade with heat or have low melt temperatures are a problem in hammer mills because of the heat generated in the mill. In 1936 the first commercially practical jet mill was introduced. Called the Micronizer, it was the predecessor to our current Micron-Master design. Up to that time, dry grinding in the sub-sieve range of 625 to 2500 theoretical mesh size range was impractical. In a jet mill the temperature of the air leaving the jets is cooled to about 200 degs F due to the Joules Thompson effect and the product leaves no warmer than the air used for the grinding. (F
