Chemicals
A soft approach E
stablished in 1987 as the exclu- sive distributor of select bromine- based compounds produced by the Dead Sea Bromine Group of Israel, MORRE-TEC Industries of Union, NJ is today a leading producer of special- ity chemicals and unique products for the nutritional, food, personal care and biotech industries. With a 2,325 sq metre facility designed to operate under ISO 9000-2008 and cGMP standards, the company is also a provider of custom blending, grinding, and repackaging services for non-hazardous and food grade chemicals and natural products. One of the company’s services is a pat-
Oversize agglomerates ejected from the sifter are recycled through the vortex mill.
ented process for micronising, or reducing to uniform micron size, solid particles without damaging their crystalline structure. The process is currently being used to produce a proprietary product called Microphyte plant extract, a solid phytosterol that is insoluble in water but, once reduced to an average 3 micron size, will form a stable emulsion that will not settle out. When added to liquid nutritional products, it acts to lower cholesterol levels in the blood. A key step in the proprietary process is “soft milling” of the initial plant extract, which reduces incoming particles averaging 40 microns in diameter to particles averaging 2-5 microns. However, particles agglomerat- ing into flakes on the walls of the vortex mill, and further compacting in the product collector “were balling up and sitting on top” of the original circular vibra- tory screener, says Paul F. Caskey, vice president, administration and operations. To solve this problem, MORRE-TEC installed a Kason Centri-Sifter centrifugal screener that removes the oversize particles.
SOFT MILLING PREVENTS PARTICLE DEGRADATION
The plant extract is delivered to the MORRE- TEC facility in 907 kg bulk bags, which are gravity discharged into a horizontal feeder equipped with a dust collector to prevent valuable product from escaping into the atmosphere. The material is then fed by compressed air through a special airlock into the micronisation chamber. The patented micronisation technol- ogy, licensed from Super Fine of Israel, is known as Vortex Mill- ing. “Unlike jet milling, which relies on collision and abrasion to reduce particle size, the process creates rapid serial changes within a vortex chamber to replicate tornado-like conditions that cause the particles to fracture along their
46 June 2012 Solids and Bulk Handling
www.solidsandbulk.co.uk
Flakes removed from 2-5 micron crystalline particles with centrifugal sifter from Kason
weakest fissure lines,” explains Leonard Glass, President of MORRE-TEC Industries. “Since the particles never actually touch each other, they are reduced to their optimum size without being exposed to destructive forces that can affect crystal morphology.” The process is effective because every
particle has inherent structural weak points. “When exposed to the proper aerody- namic conditions, the particle will fracture at its weakest point,” says Glass. “The air pressure within the vortex chamber oscil- lates from extremely high to extremely low within a matter of micro-seconds, creating a pressure differential inside and outside the particle that causes it to crack. The process continues until each particle reaches its strongest crystalline structure.” Because the process relies on pressure
differential rather than abrasion, the hard- ness of the material has no significant effect on its ability to fracture. “Materials that soften with heat can be micronised without external cooling since no exothermic heat is generated by friction,” says Glass. “In fact, the process is slightly endothermic and works well for materials that are sensi- tive to heat and would otherwise require cryogenic cooling. Materials that contain water of hydration within their crystalline structure can be milled with no detrimental drying effect, while the process yields an extremely narrow particle size distribution.”
CENTRIFUGAL FORCE PREVENTS AGGLOMERATION
Once the particles have been micronised, they are transported by compressed air up a pneumatic line into a product collector from which they are metered through a rotary airlock into the inlet spout of the centrifugal sifter. A feed screw directs them into the cylin- drical sifting chamber, where rotating, helical paddles that never make actual contact with the 25 mesh (707 micron) stainless steel screen, continuously propel them against and through apertures in the screen.
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