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Case History
A custom processor uses a pancake jet mill to economically reduce materials to fine sizes.

Dan Higgins, CTSP sales and marketing manager, stands next to the pancake jet mill that the custom processor uses to mill products to fine sizes.

CTSP Corp. is a custom processor in Belle Meade, N.J., that provides many powder processing services for customers in the plastics, food, and pharmaceutical industries.  Founded in September 1991, the company has grown to 35 employees and operates 24 hours a day, 5 days a week.

CTSP's services include various types of ambient and cryogenic milling and grinding, blending, classifying, and finishing steps such as packaging and warehousing.

CTSP sales and marketing manager Dan Higgins said customers use the processor's services when their processing capabilities are limited.  A customer may also want certain materials handled off site to avoid cross contamination at their plant.  Higgins said the main reason customers contract custom processors is economics.

"We work with many customers that are either developing a new product or improving an existing product," Higgins said.  "We provide an economical resource for milling powders during the product refinement stage.  This allows customers to use their production capabilities for existing products, while they explore new markets.  Instead of installing an unfamiliar process and learning to efficiently operate it, customers can concentrate on their unique product technology.  Other customers may have a process that can only run 6 hours a day, so it may not be smart for them to go out and purchase thousands of dollars worth or equipment.  It's easier and less expensive for them to get it done at a custom processor."

CTSP president Art Tigera said a custom processor allows the customer greater freedom to focus on their specialty.

"I think what makes us unique is we offer a tremendous amount of flexibility, " Tigera said.  "We conform to our customers' needs.  We are flexible enough to meet the most demanding requirements with respect to processing, packaging, and paperwork."

To remain successful, a custom processor must keep pace with material processing demands.  This includes purchasing equipment that can perform to the highest standards.

Loop Jet Mills aren't so fine

When CTSP was established, their jet milling needs were met by torroidal jet mill, also known as loop jet mills.  One customer's product needs brought current market demands to CTSP's attention.  The customer needed to mill a fluoropolymer with a feed sized of 1,000 microns to a final mean particle size between 3.5 and 4.5 microns.  CTSP's loop jet mills were effective at deagglomerating and milling powders to sizes of larger than 10 microns.  However, the finest mean particle size they could consistently achieve was 6 to 7 microns.

"We also realized that more and more milling applications, such as the resin, cosmetic, and ceramic industries, require a consistent, fine grind that's free of grit and oversize particles," Higgins said.

Faced with the fineness limitation of their existing loop mills and the need to service future markets, Higgins said CTSP would lose customers if they didn't provide finer grinding services.  "It was obvious that we needed to find another fine grinding technology."

Custom processor searches for a better way to grind

The custom processor narrowed their search to two manufacturers who offered a spiral jet mill, also called a pancake jet mill .  CTSP gave the manufactures a sample of material for initial evaluation at their facilities.  After favorable results, the equipment was brought to CTSP for on-site production tests using the fluoropolymer.

Finer, faster jet milling meets customer needs

At CTSP, both mill achieved the required product fineness of 3.5 to 4.5 microns, but on mill's capacity was 150lb/h - 50 percent higher than the other's.  The two jet mills were operated with 450 scfm of compressed air at 120 psig.

To compare the jet mils' results with their current operations, CTSP duplicated the tests using one of their loop jet mills.  The mill operated with 350 scfm of compressed air at 120 psig.  It achieved the required fineness, but at a capacity of 50 lb/h - 300 percent lower than the top-performing pancake jet mill.  The message was clear: CTSP needed to add a pancake jet mill to their facility.

In February 1996, CTSP installed a Sturtevant 15-inch industrial Micronizer ® pancake jet mill.

The mill uses a single circular grinding chamber.  In operation, the raw material is metered into the chamber through a feed funnel and venturieductor.  Jet nozzles are precisely aligned around the chambers's periphery to produce high-velocity compressed-air, inert gases, or steam jet pulses that create a vortex.  The tangential angle of the jet flow causes the particles to rotate, subjecting them to continuous particle -on-particle impact and reduction.  Centrifugal force retains larger particles in the grinding area while centripetal force drags the presized fines toward the center, where they discharge through an outlet tube for collection in a process baghouse.

Because the pancake jet mill uses compressed air as the grinding medium, the mill has no moving parts and no media to contaminate the product.  The mill creates no heat during the milling process, requires no lubrication, and is easy to access and clean.  At CTSP, the mill operates with 450 scfm of compressed air at rates between 50 and 300lb/h.  It can reduce particles to less than 1 micron.

The mill's installation went smoothly.  "Startups are startups but I think this was the best I've seen," Tigera said.  "The mill got up, started running, and away we went."

The new jet mill has allowed CTSP to meet customer requests for smaller particle sizes.  "This mill can get certain products to a [size] level that the loop mill never achieved," Tigera said.

Besides meeting smaller particle size requirements, CTSP has increased efficiency using the pancake jet mill.  While CTSP continues to use the loop jet mill for many applications, the pancake jet mill has allowed the custom processor to mill materials to very fine sizes at faster rates for their customers.
Tigera said the mill has allowed 50 percent capacity increases with some material and increases as high as 200 to 300 percent with others.  These improved processing capabilities have allowed the custom processor to attract new customers.

"It's a time-versus-throughput curve - the loop jet mill, in some cases, may be able to grind materials to the required fineness, but the [processing] time is much longer," Tigera said.  "In other words, the rate is much lower, and therefore the cost is much higher."

The pancake jet mill uses compressed air and particle-on-particle impact to grind materials in the circular grinding chamber.

An unexpected benefit was the extra technical support offered by the jet mill manufacturer.  "The manufacturer's personnel have always been extremely helpful with tips on tweaking the equipment for the unusual specifications required by some of our products," Higgins said.

"When we originally became involved with the manufacturer, we purchased [their jet mill] because of its superior performance," Higgins said.  "From a cost standpoint they were very competitive.  But they also overwhelmed us with support.  Their knowledge and experience is as important to us as the equipment.  Quite frankly, we'll go to them first for any mill we're considering to see if they make it before we buy elsewhere.  We could not be more pleased with a manufacturer."

CTSP has since purchase two more pancake jet mills from the manufacturer, including a ceramic-lined 24-inch mill.  "That opened up a whole new market for us," Higgins said.  "Now we're handling abrasive materials on a routine basis."

"We also purchased a laboratory size 4 inch mill from them.  With this small mill, the sample is collected in an easy-to-clean exhaust bag, instead of a large baghouse.  The lab mill's air consumption - 55 scfm - is so low that we can test small quantities of powders using nitrogen or argon inert gases."  Besides the pancake jet mills, CTSP also purchased a mechanical impact mill with an internal air classifier from the manufacturer.

Tigera said the company is pleased with their pancake jet mills.  "It was a good purchase," he said.  "The mill does what it is suppose to do."

PBE

Reprinted from Powder and Bulk Engineering , May 1998

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