MN PR 401
A crushed stone producer is planning to replace an existing secondary/tertiary crushing circuit with a new two-stage crushing circuit.
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A crushed stone producer is planning to replace an existing secondary/tertiary crushing circuit with a new

two-stage crushing circuit. You have been tasked with preparing a preliminary design for this circuit. The facility processes a hard granite (2.75 g/cm3) from a nearby surface mine. Currently a jaw crusher, which is operating at a nominal setting of 7 inches, is used for primary crushing. The crushed material is stockpiled prior to further crushing and serves as the feed material to the two-stage circuit. The new circuit will be designed for an average feed rate of 950 short tons-per-hour (TPH). The new two-stage circuit will be designed to produce two products (-1+¼ inch and -¼ inch) for different projects. To maximize the production of the coarser material, a reduction ratio of less than 3:1 will likely be required for the secondary crusher.

Based on these specifications, provide the following information needed for the circuit design.

Indicate which tables were used and justify your selections:

  1. Labeled circuit flowsheet for the new two-stage circuit
  2. Cumulative % passing size distribution of the primary crusher product (stockpiled material)
  3. Specifications of the secondary crusher and the reduction ratio
  4. Cumulative % passing size distribution of the secondary crusher product
  5. Calculated circulating load (in TPH)
  6. Specifications of the tertiary crusher
  7. Cumulative % passing size distribution of the tertiary crusher product
  8. Ideal solids split diagram and flow rates as used for the screen design
  9. Required screen area and screen dimensions:

Select from standard screen widths of 4, 6, or 8 feet

Indicate final screen selection

10. The solids mass flow rate (in TPH) for each stream in the designed circuit

Tabulate these results

11. Normalized cumulative % passing 8 M in the -¼ inch product


List and Justify All Assumptions

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