Blast-slag treatment Industrial solid waste - Solid waste treatment blast-slag holding furnace

Part of the process diagram of BF slag treatment of industrial waste slag:

Core Functions & Objectives

1. Harmlessness: Eliminate potential environmental risks (e.g., leaching of heavy metals, alkalinity pollution) by modifying the slag’s chemical and physical properties through high-temperature processing.
2. Reduction: Reduce the volume of slag (typically by 30%–50%) via melting, densification, or crystallization, lowering storage and transportation costs.
3. Resource Utilization: Convert slag into marketable products (e.g., cement admixtures, building aggregates, functional materials) to create economic value and replace non-renewable resources.

Key Technical Principles

• Raw Material Pretreatment: Blast furnace slag is first crushed, screened, and dried to remove moisture and impurities (e.g., iron scraps, dust), ensuring uniform feeding.
• High-Temperature Processing: The pretreated slag is fed into the furnace, where it is reheated to a molten or semi-molten state. At this temperature,:
  • Amorphous phases in the slag (e.g., glassy components) rearrange into stable crystalline structures.
  • Volatile impurities (e.g., sulfur compounds) are released and captured by flue gas treatment systems.
  • Heavy metals (if present) are either immobilized in the slag matrix or volatilized for targeted recovery.
• Post-Treatment: The modified slag is rapidly cooled (via water quenching or air cooling) to retain desired properties, then crushed and graded into final products.

Main Types of Furnaces

Typical Products & Economic Value

• Cement Admixtures: Granulated blast furnace slag (GBFS) is a key component of blended cement, improving strength, durability, and corrosion resistance.
• Building Aggregates: Crushed and graded slag replaces natural gravel in concrete, asphalt, and roadbeds, reducing reliance on quarrying.
• Functional Materials: Specialized treatment (e.g., activation, doping) produces slag-based adsorbents (for wastewater treatment) or insulation materials.
• Metal Recovery: Some slags contain residual iron, manganese, or rare earths, which can be extracted during thermal processing.

Environmental & Industrial Significance

• Waste Reduction: Globally, over 400 million tons of blast furnace slag are generated annually; treatment systems divert nearly 100% of this waste from landfills.
• Low Carbon Impact: Using slag as a cement admixture reduces CO₂ emissions from cement production (each ton of GBFS replaces ~0.8 tons of clinker, cutting emissions by ~0.6 tons).
• Circular Economy: The system closes the loop in ironmaking by "recycling" waste into inputs for construction, manufacturing, and environmental sectors.