The Micronizer brand jet mill was patented in 1934 by Norwood H. Andrews and was the first fluid energy mill to use superheated steam as a source of energy to reduce materials to sub-sieve range. Five jets were configured to pulverize minerals and other materials. The Micronizer gained wide commercial acceptance because other attrition mills could not attain the low micron sizes that the Micronizer could reach.
- 1934 – Sturtevant developed the first jet mill technology, the Steam Pulverizer used opposed jet milling: Sturtevant Patent (US 1,948,609)
- 1936 – Spiral jet milling was invented by Sturtevant (US 2,032,827). Sturtevant and its customers consider the Micronizer to be superior to the Steam Pulverizer and the fluid bed machine was taken off the market.
- 1945 – The vortex classifier is introduced inside the Micronizer to prevent grit
- 1948 – Both International Pulverizing and Micronizer Company are consolidated into Sturtevant
- 1955 – 10 years after both the end of WWII and the commercial manufacturing boom of Penicillin. 6 Micronizers were sold that year just for penicillin manufacturing.
- 1957 – First Micronizer developed to jet mill graphite for pencils
- 1967 – First Micronizer sold for inhalable Albuterol (Salbutamol)
- 1976 – First full cryogenic Micronizer system developed for NASA
- 1983 – Sturtevant develops the process to jet mill neodymium rare earths in collaboration with Hitachi
- 1992 – Sturtevant invents the Micronizer with an open grinding air manifold, revolutionizing jet milling again
- 2003 – Sturtevant Patents the world’s smallest jet mill, the Qualification Micronizer
- Today – More Micronizers used in pharmaceuticals, ceramics, metals, defense and TiO2 than any other jet mill manufacturer.
Principles of Operation
The Micronizer brand jet mill utilizes fluid energy compressed air, gas or superheated steam to grind and classify, in a single chamber with no moving parts. Activated by high pressure air, the particles are accelerated into a high speed rotation in a shallow grinding chamber. As the particles impact on one another their size is reduced. Centrifugal force holds larger particles in the grinding rotation area until they have achieved the desired fine particle size. Centripetal force drags the desired particles towards the static classifier where they are allowed to exit upon achieving the correct particle size. The final particle size is controlled by varying the rate of the feed and propellant pressure.