Nonmetallic Mineral

Coal Washing

A primary objective of coal washing is to enhance coal quality, particularly for producing metallurgical coke used in steelmaking. High ash and other harmful elements in coal can increase material consumption, reduce steel output, generate more slag, and lower furnace efficiency.

Coal Analysis:

Designing an effective coal washing plant requires a thorough understanding of the coal’s structure and properties, obtained from representative sample analysis. Key parameters include:

• Hardness and brittleness

• Moisture content

• Ash content and mineral composition

• Harmful substances (e.g., sulfur from mineral and organic sources)

• Coking characteristics and volatile matter content

• Plastometry and maceral composition

• Coal rank and grain size distribution (including particles <0.5 mm)

• Coal washability assessed by sink and float tests

These parameters form the foundation for selecting suitable processing methods. Main operations include crushing, sizing, flotation, dewatering, and gravity-based washing.

For coarse particles with sufficient liberation and specific gravity differences, gravity separation is preferred. Techniques are classified into three categories:

Vertical movement/stratification: e.g., jigs

Movement along an inclined surface or thin water layer: e.g., spiral concentrators, vibrating tables

Suspension in a fluid medium with intermediate specific gravity: e.g., heavy media drums, cyclones, tri-flow separators

Compared with flotation, the gravity method offers key advantages: it requires no chemical reagents, reducing both operating costs and environmental impact and it is relatively simple to operate.