stone crusher process flow

Stone Crusher Process Flow: An Overview

This article details the fundamental process flow of stone crushing, a core operation in quarrying and aggregate production. It systematically breaks down the stages from raw material extraction to the final graded products, explains the key equipment involved, and highlights critical control points for efficiency and product quality. The discussion will cover both basic and more complex flows, compare different crushing circuit configurations, address common operational questions, and illustrate the application with a real-world case study.

The Fundamental Crushing Process Flow

A typical stone crushing process flow can be divided into three primary stages: Primary Crushing, Secondary Crushing, and Tertiary/Quaternary Crushing, followed by Screening and Material Handling throughout. Each stage reduces the stone to a smaller size and shapes the aggregate particles.

1. Primary Crushing: This is the first size reduction stage. Large blasted rock (often up to 1 meter in diameter) is fed into a primary crusher, such as a jaw crusher or gyratory crusher. The goal is to reduce the material to a size manageable for downstream conveyors and crushers, typically producing output ranging from 100mm to 250mm.
2. Secondary Crushing: Material from the primary crusher is conveyed to secondary crushers like cone crushers or impact crushers. This stage further reduces the size (typically to between 20mm and 100mm) and begins to improve the shape of the aggregate.
3. Tertiary/Quaternary Crushing: For producing finer aggregates (e.g., sand, chips) or achieving specific particle shapes (cubical), additional crushing stages using cone crushers or Vertical Shaft Impact (VSI) crushers are employed. VSI crushers are particularly valued for their superior particle shaping capabilities.
4. Screening: Screening is an integral and recurring step. After each crushing stage, vibrating screens separate the material by size. Oversized material is sent back to the appropriate crusher (forming a "closed circuit"), while correctly sized material proceeds to the next stage or to product stockpiles.
5. Material Handling: Conveyor belts connect all stages, moving raw feed, transferring crushed material between crushers and screens, and finally transporting finished products to designated stockpiles.

A simplified process flow diagram is as follows:
Blasted Rock Feed -> Primary Crusher -> Primary Screen -> Secondary Crusher(s) -> Secondary Screen(s) -> Tertiary Crusher(s) -> Final Screening -> Product Stockpiles

Comparison of Common Crushing Circuit Configurations

The arrangement of equipment defines the circuit's efficiency, product flexibility, and cost. Two common configurations are compared below:

Feature	Open Circuit Crushing	Closed Circuit Crushing
Process Description	Material passes through a crusher only once without being recirculated for re-crushing.	Material is continuously screened after crushing; oversized material is recirculated back to the same crusher for further reduction.
Control over Product Size	Limited. Product size distribution depends largely on the crusher's discharge setting and feed homogeneity.	Precise. Allows tight control over top product size and improves overall gradation consistency.
Efficiency & Yield	Generally lower efficiency; can produce more unwanted fines or oversized material depending on feed variability.	Higher efficiency; maximizes yield of in-spec product by ensuring all oversize is reprocessed.
Typical Application	Simple operations, production of base materials where strict gradation is less critical, or first stage in a multi-stage plant.	Standard for modern aggregate plants requiring specific, consistent product grades (e.g., concrete aggregates, asphalt chips).

Most professional aggregate plants operate secondary and tertiary stages in closed circuit to ensure product quality.

Real-World Case Study: Granite Aggregate Plant in Southeast Asia

A large granite quarry supplying aggregates for a major port construction project required high-quality, cubical aggregates for high-strength concrete.

• Challenge: The local granite was highly abrasive. The existing two-stage jaw-cone circuit produced excessive flaky particles, which were unsuitable for concrete specs and led to rapid wear on equipment.
• Solution & Process Flow Upgrade: The plant flow was redesigned to include a shaping stage.
  1. Primary: Jaw Crusher (remained unchanged).
  2. Secondary: High-performance cone crusher in closed circuit with a screen.
  3. Tertiary/Shaping: A Vertical Shaft Impact (VSI) crusher was added in closed circuit with an air classifier to remove excess fines.
• Outcome: The new flow allowed precise control over particle shape and reduction of flakiness index from over 20% to below 10%. The VSI produced highly cubical aggregates meeting strict project specifications. While wear costs on the VSI were managed with proper rotor design and wear part metallurgy, overall plant profitability increased due to premium product pricing and reduced waste.

FAQ (Frequently Asked Questions)

1. What is the most important factor affecting crusher performance?
   The "feed material characteristics" are paramount according to industry handbooks like The Aggregate Handbook. Hardness, abrasiveness, moisture content, clay contamination, and initial feed size directly influence crusher selection, wear rates, throughput capacity,and final product shape.

2.What's better: Jaw Crusher or Cone Crusher for primary crushing?
Neither is universally "better"; they serve different needs based on capacity,material hardness,and mobility requirements.Jaw Crushers offer lower initial cost,a smaller footprint,and handle larger feed sizes,making them suitable for medium-hard rockand portable plants.Gyratory Crushers(atype of primary compressioncrusher) provide higher throughputfor very large-scale stationary quarries handling hard abrasive rock.The choiceis an engineering trade-off.

3.How does screening impactthe finalproduct quality?
Screeningis criticalforproductgradationcontrol.Ineffective screening allows oversized particlesinto finished productsor sends correctly sizedmaterialbackfor unnecessary re-crushing(generating excessfines).Proper screen selection(decksize,motiontype),maintenanceof screencloths,and controlof feed rateto screensare essentialfor maximizingyieldofon-specmaterialandplant profitability.

4.Can recycled concretebe processedinastonecrushingplant?
Yes.Recyclingconcreteand demolitionwasteisacommonapplication.Mobilejawandimpactcrusherstypicallyformthecoreoftheseoperations.Theprocessflowmustincludeapre-cleaningstage(removingrebar ,wood ,plastic)and oftenamagnetsystemto removeferrousmetals.Thecrushedproduct,RAP(RecycledAggregateProduct),isusedasabasematerialor,duringfurtherprocessing ,asaggregatefornewconcrete .