| Jet mills are powered by a pressurized gas such as compressed air, nitrogen, or superheated steam. Compressed air is by far the most common input energy source for jet mills with input demand ranging from 7 scfm (1" mill) to 2900 scfm (42" mill), delivered at 100 psi.
Nitrogen is used when processing materials must be maintained in an inert atmosphere to protect from oxidation and for those that are hygroscopic. The effect is to keep the powder very dry, preventing caking adherence on interior contact surfaces. Nitrogen is also used to lower the temperature at the material into its glass transition zone. Soaking and feeding powders at extremely cold temperatures in this way has an embrittling effect on the particles, enhancing fracturing.
Superheated steam from a boiler provides the highest level of energy input and is often used in production lines that run 24x7 continuous operation. Steam can be used to process the most difficult to grind or convey materials or can be used to deagglomerate chemically engineered products. Lightweight and high-velocity steam power can be the most efficient form of input energy. Superheated steam also ensures a very dry medium for accelerating particles in a jet mill at very high energy levels.
In rare instances Argon gas has been used on pyrophoric materials to prevent spontaneous ignition.
In most applications, compressed air is used and a stand-alone air compressor sized properly for the application generally provides this air supply. A standard rule-of-thumb for estimating compressor hp rating is that one hp will produce about 4 scfm of air [4 scfm / hp]. For example, an 8" jet mill requiring 100 scfm of air would require a 25 hp air compressor.
Air compressors should supply air that is dry and free of oil. Most compressor manufacturers can specify either a refrigerated or a desiccant type dryer that matches customer application flow rate, pressure, and moisture requirements. Generally, air supply should be delivered with a dew point of less than 35 F with less than 1 or 2 PPM of oil. Oil- injected screw compressors require in-line oil filters to achieve this specification. Oil free compressors are available at higher cost but may be required for certain sanitary processes.
Oil-free compressors are generally high-efficiency multistage units and may be used to supply air at high temperatures by retaining the heat of compression.
Jet pulverizer applications engineers make it a point to ensure that the customer understands the requirement for an adequate and properly conditioned air supply. Generally, customers either have sufficient installed compressed air capacity available at their facility or they make plans to increase plant capacity to accommodate the demand of their new jet mill. Upon request, however, Jet Pulverizer Co. will include a suitable air compressor in the jet mill system package quotation. Compressors recommended by Jet Pulverizer Co. are selected from those offered by various manufacturers on the basis of service and resource factors, and the individual features they offer. | 
