Separation of Difficult to Grind Components in a Feed Stream

Problem: In raw wood fiber processing, the fiber is typically contaminated with sand and gravel from transportation during the logging process. As a result, these impurities cause excessive wear to the internal components of the milling machinery. It was necessary to find a low cost efficient method of disposing hazardous materials before size reduction.

Customer’s requirement:

  • Product Rate: 20,000 lb/hr of wood fiber
  • Removal of hard to grind and abrasive contaminants including sand and gravel
  • Increase purity of final product by disposal of hazardous materials

Operational considerations:

  • Wear resistant design
  • Easy access to internal wear components
  • Ease of component replacement
  • Adjustable operating parameters to satisfy the customer’s particle size and capacity requirements

Solution: The unique design of the Pulvocron mill’s classification system allows for external separation of components within the product stream and more efficient hazardous materials disposal.

Feed containing hard to grind contaminants enter the Pulvocron’s milling section. After milling, the product is air conveyed into the Pulvocron’s dynamic classifier section. In-spec ground product exits the dynamic classifier and is air conveyed to the product collector. Over-sized material (contaminants in this case) discharge from the Pulvocron via the tailings port and enter the external plenum. Here the contaminants settle into a collection drum or can be pneumatically conveyed to remote collection.

The hazardous material disposal process was developed and tested at the Bepex International Process Development Center using the Bepex Pulvocron air swept pulverizer machine. A variety of grinding plates, air flow rates and classifier speeds were used to determine the most efficient operation. Following successful testing, product samples were sent to the customer for analysis.

Benefits and Results:

  • Increased life of wear components
  • Increased purity of final product by the recycling and disposal of hazardous materials
  • Minimal change to existing footprint within the plant
  • Hard to grind material collected for use in other areas within the plant
  • Elimination of downstream separation devices