Blast Furnace Hot Slag Modification Furnace（Slag Conditioning Furnace）

1. Equipment Overview

2. Complete Equipment Composition (5 Core Systems)

2.1 Main Furnace Body System

1. Furnace Shell: Welded cylindrical or square steel structure equipped with external water-cooling coil or spray cooling. Outer diameter ranges Φ3,600～Φ5,200 mm with overall height 2,200～3,200 mm.
2. Refractory Lining: Multi-layer masonry structure: light high-alumina castable for thermal insulation layer, corundum/chrome-corundum ramming mix for working layer against corrosion from blast furnace slag. Furnace chamber is partitioned into feed modification zone and molten pool homogenization zone by partition wall with liquid through-hole and water-cooled sliding gate.
3. Material Inlet & Outlet

• Hot Slag Inlet: Water-sealed chute on furnace top/sidewall connecting BF slag runner for gravity feeding of liquid hot slag;
• Modifier Feeding Port: Sealed feed opening on furnace top coupled with dust containment;
• Main Tapping Hole (water-cooled copper fitting): Lower sidewall for continuous controlled melt feeding to fiber forming line;
• Iron Discharge Outlet: Bottom drain for periodic removal of precipitated iron granules and iron-bearing residues.

2.2 Electrode Power Supply System (Core Heating Unit)

• Electrodes: Φ350～Φ500 mm graphite electrodes (3pcs for 3-phase AC, 2pcs for DC type) with servo hydraulic lifting control;
• Special furnace transformer: On-load tap-changing transformer with electrically regulated grading voltage, power rated per furnace capacity;
• Short-net copper busbar, water-cooled electrode clamps and full set of hydraulic lifting cylinders.

2.3 Automatic Modifier Batching System

2.4 Molten Bath Homogenizing System

• Arc self-stirring: Molten pool agitated by electric arc disturbance;
• Bottom nitrogen bubbling system: Pre-buried permeable bricks inside furnace bottom + high-pressure nitrogen pipeline, nitrogen pressure 0.2～0.4 MPa for forced homogenization of slag and additives;
• Optional carbon mechanical stirring impeller for large-capacity furnaces.

2.5 Auxiliary Supporting Systems

3. Standard Technical Parameters by Production Capacity

4. Core Process Control Parameters

4.1 Temperature Parameters

• Incoming BF hot slag temp.: 1,320～1,380°C;
• Target tapping temp. after modification: 1,360～1,420°C (optimal 1,380±20°C for rock wool production);
• Furnace holding temperature range: 1,350～1,450°C; electrodes supply supplementary heat to offset temperature drop caused by cold modifiers.

4.2 Chemical Composition & Acidity Coefficient (Mk)

• Raw BF slag basicity (CaO/SiO₂): 0.9～1.0;
• Target acidity coefficient Mk=(SiO₂+Al₂O₃)/(CaO+MgO): 1.25～1.55 (1.4～1.5 preferred for mineral wool);
• Modifier chemical index: SiO₂=45%～75%, Al₂O₃=8%～35%, feed particle size ＜0.1 mm.

4.3 Physical Properties of Molten Slag

• Tapping viscosity: 1.2～4.0 Pa·s (optimal 1.5～2.5 Pa·s for fiberization);
• Allowable liquid level fluctuation: ≤±80 mm to guarantee stable continuous tapping;
• Nitrogen bubbling pressure: 0.25～0.35 MPa, homogenization duration ≥35 min for uniform composition.

4.4 Material Proportion Index

• Modifier adding ratio: 5%～15% by mass, max blending rate up to 30%;
• Raw slag iron content: ＜3%, accumulated bottom iron discharged per shift intermittently.

5. Equipment Operational Advantages

1. Waste Heat Recovery: Rely on inherent high sensible heat above 1300°C of BF slag; electrodes only supply supplementary power, saving over 50% power vs cold-feed cupola furnace;
2. Continuous Feeding: Direct hot slag feeding without ladle transfer, minimizing heat loss and raising incoming slag temperature by around 30°C compared with tank transportation process;
3. Full Automation: PLC interlocked control for batching, power regulation, temperature and tapping flow, one-click formula modification available;
4. Eco-friendly Design: Fully enclosed feeding + top dust collection, zero unorganized flue gas emission, 100% solid waste resource utilization.

6. Selection Suggestions

1. On-line tapping matched with blast furnace: adopt continuous single-chamber modification furnace; intermittent ladle-delivered hot slag: dual-chamber furnace with dedicated molten storage tank;
2. High-grade rock wool production: DC modification furnace for superior uniform bath temperature and stable chemical composition; ordinary slag wool: 3-phase AC furnace for lower investment cost.