Spiral Jet Mill

Midous NP, Hoek L, Pailleres J, Authelin R. 1999. Micronization of pharmaceutical substances in a spiral jet mill. Powder Technol. 104 113-120. 

Jet Mill. Jet mills are an alternative to hammer or pin milling, where the primary mode of action is the mechanical impact with the particle. With jet milling, microni-zation is accomplished through the action of fluid energy, resulting in particle-particle collisions and the subsequent reduction in size. Spiral jet mills, loop jet mills and fluidized bed jet mills are examples of fluid energy mills. 

The impact of accelerated solid particles with walls or other particles is used in jet mills (Fig. 14.13). Velocities of 500 to 1200 ms-1 are reached in a driving gas or vapor jet [31], In a spiral jet mill, particles are sucked through an injector into a... 

Within this grouping of mills are several different designs including the pancake jet mill (horizontal milling chamber), the loop Jet mill (also known as oval milts), spiral jet mill, oppo.sed-jet mills (opposed jet streams), and classifier mills (Fig. 23). 

Spiral Jet Mill The original design of the spiraljet mill, also called a pancake mill, is shown in Fig. 21-71. This design was first described by Andrews in 1936 and patented under the name Micronizer. A number of nozzles are placed in the outer wall of the mill through which the grinding medium, a gas or steam, enters the mill. 

A spiral jet mill combines both grinding and classification by the same jets. The vortex causes coarse particles of the mill contents to be transferred to the outer zone, as fines can leave through the central outlet. The solid feed is brought into the mill by an air pusher. The outlet is placed in the center of the mill chamber. The working principle of this mill was extensively investigated by Rumpf... 

A process that facilitates size reduction beyond that achieved with either rotor-milling or ball-milling is jet-milling. A t5q)ical laboratory-scale spiral jet mill, the Hosokawa Alpine Aeroplex 50AS, is shown in Fig. 5. The process uses a high-pressure jet of gas to draw the particles into the main body... 

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