A device manufacturer was producing glass powders suitable for use in electrical applications, using batch style ball mills with YSZ media. The process was slow, dusty, of variable end quality, and labor intensive. While this method was satisfactory for maintaining the powder iron free, the grinding media itself was a contaminant to the powder.
Problems in the downstream calcining, slurrying and spray drying operations indicated that the particle distribution of the ball milled powder was too broad. In order to reach the mean particle size, the media mills produced too much very fine powder, while also leaving too much coarse powder.
As the customer looked for a means to improve the ball milled powder, Applicon invited them to consider replacing the ball mills. The capital budget did not initially support the larger project, but eventually the customer determined that a completely new milling system was preferable, if it would reduce labor and improve quality.
Their search for more automated powder production considered vibratory media milling; high kinetic energy mechanical milling; and fluid bed jet milling.
The first method would save labor, but like ball milling, there would be an ongoing cost for expensive ceramic media, and still that slight reduction of quality cause by fines or "stones" from broken media. The mechanical mill, despite construction with carbide wear surfaces, failed immediately from intense abrasive wear. The jet mill tests were most promising, for both particle distribution and wear. Applicon was contracted for the turnkey system, using our AIM-Jet fluid bed jet mill for final powder production.
As with most older facilities, the customer's plant was challenged for floor space. They could not give up the ball milling area until the new pulverizing system was fully operable, so there was very little space for any new system. Because space was so tight, it was crucial that the installation of the new milling system be accomplished with minimum disruption of the existing production flow.
After working out the basic system flow, Applicon set about shrinking the system footprint, keeping the height under the existing roof purlins, and also considering how to allow safe access for inspection and maintenance. The design effort produced a compact, serviceable system that neatly fit into a space adjacent to the existing calciner.
Applicon designed the system to receive coarse glass frit 5 to 25 mm as quenched, which is fed through our jaw crusher, producing crushed glass with 5 mm top size. That in turn is fed to an Applicon high reduction roll crusher, also designed for very abrasive service, yielding -2 mm x 0 glass sand to feed to the pulverizer. The glass sand is metered by weight to our AIM-Jet mill, where the particles are pulverized to powder, "glass on glass" within the fluid bed, using only compressed gas.
Our modular system design allowed much of the system to be pre-assembled in our shop, and reduced the field installation and electrical wiring to only six days.
This continuous pulverizing system accomplished these goals for the customer
• Produced a finer mean size, and narrower particle size distribution
• Reduced labor dramatically, while also increasing output
• Virtually eliminated airborne dust, and powder loss
• Eliminated the cost of, and contamination by, ceramic media
• Virtually eliminated replacement parts cost
• Satisfied the requirement for iron free finished product
| This system included: |
• Roll crusher for tertiary sizing
• Screening coarse crushed
• Gravimetric feed to micronizing
• AIM Jet fluid bed jet mill
• Static particle classifier
• Abrasion resistant filter receiver
• Feeder to calcining
• Modular design
• Structural tower