How to Select Conveyor Belts for Power Station Fly Ash and Bottom Ash?

Coal Ash Handling Overview

Coal-fired power stations produce two types of ash: fly ash (captured in electrostatic precipitators or bag filters —?fine powder) and bottom ash (collected from the bottom of the boiler —?coarser and initially hot). Both require careful conveyor specification, but for different reasons.

Fly Ash Belt Requirements

Fly ash is a fine powder (particle size 1—?50 micron) with a bulk density of 0.7—?.0 t/m³. It has low abrasiveness but presents significant health and environmental hazards:

Health Hazard

Fly ash contains crystalline silica, heavy metals (arsenic, lead, mercury), and in some ashes PAHs (polycyclic aromatic hydrocarbons). Exposure regulations are strict. All fly ash conveyor systems must prevent dust release:

• Fully enclosed transfer chutes
• Negative-pressure dust extraction at all transfer points
• High-efficiency belt scrapers —?carryback creates diffuse dust on the return run
• Sealed conveyor covers where possible

Belt Specification for Fly Ash

• Cover grade: Grade M (low abrasiveness)
• Antistatic: essential —?fine dry fly ash is a static electricity hazard
• Cover thickness: 4—?mm top / 3—?mm bottom (low wear rate)
• Carcass: EP —?standard for the tension requirements

Bottom Ash Belt Requirements

Bottom ash is discharged from the bottom of the boiler at temperatures of 200—?00°C. After quenching with water, temperature may still be 80—?00°C at the belt loading point:

• Heat resistant belt mandatory: T1 (if consistently below 100°C) or T2 (up to 150°C)
• Cover thickness: 8—?2mm top —?bottom ash contains sharp slag particles
• Wet handling: bottom ash is usually quenched —?use EP carcass for moisture resistance
• Impact protection: bottom ash is coarser and heavier than fly ash —?UHMWPE impact bars at loading points

Comparison: Fly Ash vs Bottom Ash Belt Spec