Grinding Mills

Large SAG & Ball Mill During Installation
Manufacture of Large Ball Mill Shell
Inside a large SAG Mill

New Concept Projects formed a Joint Venture Agreement with Osborn and now supply the new Osborn Grinding Mill Range.

Our capability includes the supply of new mills, based on existing proven Osborn designs, engineered with assistance of modern design techniques and 3D simulation packages. We also offer after sales support and spares backup to all Osborn mills currently operating in the market.

Mill sizes range from 1.6m (5ft) diameter through to 11.6m (38ft) diameter, all carrying gear driven designs. The Grinding Mills are supplied to clients worldwide.

For projects carrying restricted budgets or accelerated timing requirements, NCP incorporates the supply of refurbished Grinding Mills into the portfolio to match project requirements. These options can be refurbished back to OEM specification and be supplied with warrantees equivalent to new equipment.

NCP Mill Design Capabilities

  1. Process Modeling through an NCP developed Specific Energy Breakage Model
  2. 3D Drafting
  3. Structural Design FEA
  4. Bearing Fluid Film Analysis
  5. Drive Train Design (Including Variable Speed Drives)
  6. Drive Train Torsional Analysis
  7. Casting Simulations & Foundry Methodology Review
  8. DEM Charge Analysis & Liner Design Optimization
  9. Project specific chute design based on Trajectory Theory

New Equipment Offered

  1. Osborn Grinding Mills & Comminution Circuit Equipment
  2. Osborn Crushing & Screening Plants & all related equipment
  3. Scrubbers are offered by both Osborn (<3.5m Diameter) and New Concept Projects (>3.5m Diameter)
  4. Mill Spares for all Mill makes

AG/SAG Mills

AG/SAG Mills can accept feed up to 350mm and used as primary grinding units. The mill is thus fed with the product from a Primary Jaw or Gyratory crusher. Grinding action is by particle-on-particle impact (AG Mills) and a combination of ball & particle-on-particle impact (SAG Mills). SAG applications include both wet and dry operation.

The discharge of the AG/SAG mill is fitted with a grate discharge, where ground material passes through slotted apertures into a pulp chamber that then lifts the material out the belly of the mill. The lifted material is then deflected into the trunnion and exits via a trommel into the mill discharge sump.

Rod Mills

Rod Mills can accept feed up to approximately 25 mm and are generally selected to grind products in the 4 mm to +0,5 mm range. Grinding action is by line contact between rods which extend the length of the mill. Rod Mills are usually operated in open circuit. Most rod mill applications involve wet grinding where material is reduced in size from crusher product size to a size suitable for ball mill feed. To avoid breakage or tangling of rods, the L/D ratio of rod mills is kept within the limits of 1, 3/1 to 2/1.

Osborn supplies the three most common rod mill types: overflow, end peripheral and center peripheral discharge.

Overflow:
An overflow mill is constructed with a feed opening at one end and a discharge opening at the other, both on the axis of the mill. Material leaves the mill by overflowing at the discharge end. Used for producing the finer end of the product range.

End Peripheral Discharge (EPD):
The end peripheral discharge mill's steeper gradient produces a shorter retention time and thus a coarser product than the overflow type. Product is discharged through port openings equally spaced around the periphery of the shell at the discharge end. Grinding may be accomplished wet or dry. End peripheral discharge is used to good advantage in damp grinding of coke on steelwork sinter plants.

Center Peripheral Discharge (CPD):
Feed is from both ends and is discharged at the center through discharge ports. The fact that the particles only travel half the mill length makes the CPD rod mill an outstanding unit for coarse grinding and rapid removal of finished material.

Ball Mills & ROM Ball Mills

Ball mills accept feed that ranges in size from 80% passing 70mm (ROM Ball Mills) through 15 mm (post a tertiary crusher circuit) to fine feeds of less than 1mm in regrind operations. Products may be as coarse as 0.5 mm or as fine as 40 microns and below. In a ball mill the length may be less than, equal to, or greater than its diameter. A short length mill has a lower retention time and produces a coarser product. Longer mills have a longer retention time and therefore produce a finer grind.

Grate Discharge:
This mill type embodies the principle of steep pulp gradient, quick discharge operation. A grate and pulp lifter assembly at the discharge end of the mill enables a ball charge of 35-40%. The quick removal of ground material reduces overgrinding, especially when operated in closed circuit with a classifier.

Overflow:
As the name implies, material is discharged from an overflow mill by overflowing the discharge opening. The overflow mill is simple to operate and maintain and is ideal for producing fine products such as in regrind operations.

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