Structural Components
Furnace Top: Equipped with a charging port and a flue gas outlet.
Furnace Body: A vertical furnace body, which can be designed as rectangular or circular as needed, with an internal water jacket.
Tuyeres: Located at the bottom of the furnace body, responsible for blowing in air or oxygen-enriched air.
Hearth: Collects molten metal and slag; depending on the design, it may have a hearth or not, used for further separation of the melt.
Foreboard: A device located outside the furnace used for separating the melt, particularly in some blast furnace designs.
Operating Principle
1. Charging: Solid materials (such as ore, flux) and fuel (coke) are added in batches from the top of the furnace.
2. Descending: The furnace charge moves vertically downwards under its own gravity.
3. Blast and Reaction: Air is blown in through the tuyeres and encounters the descending charge, undergoing an oxidation-reduction reaction at high temperature to melt the charge.
4. Melt Discharge: The molten mixture flows into the hearth or forehearth for separation; slag and matte are discharged separately.
5. Flue Gas Discharge: High-temperature flue gas rises through the gaps in the furnace charge column and exits from the flue gas outlet at the top of the furnace, entering the dust collection device.
Features and Benefits
Multifunctionality: The blast furnace can process various primary and secondary materials, making it a multi-purpose smelting equipment.
Increased Efficiency and Output: Using oxygen-enriched air accelerates the smelting process and increases output.
Improved Environment and Quality: Reduced or no ash production, thus reducing the use of additives and related costs.Using oxygen-enriched air reduces flue gas emissions and improves the operating environment.The produced pig iron is of better quality, with less or no slag generation, requiring no additional treatment.
Adaptability: Blast furnaces are suitable for various production capacity needs, especially advantageous in capacities below 50,000 tons/year.
Cost-effectiveness: Reducing slag and ash content lowers raw material and transportation costs.
Application of Blast Furnace
• Non-ferrous metal smelting: Used for smelting non-ferrous metal concentrates such as lead, zinc, and tin.
• Ironmaking: Blast furnaces are commonly used in ironmaking.
• Sulfide ore smelting: Can be used to smelt copper sulfide ores, producing copper matte and slag.
• Resource recovery: Closed blast furnaces can recover sulfur dioxide from flue gas, achieving sulfur resource recovery and reducing pollution.
Refractory Bricks for Blast Furnace
The temperature, erosion (slag/molten metal/gas), scouring, and mechanical impact vary greatly across different parts of a blast furnace. Refractory bricks must be specifically matched to these differences. The core parts and their selection are as follows:
1. Furnace Roof and Throat
High-alumina bricks (Al₂O₃ 65%-85%), clay bricks (Al₂O₃ 30%-45%, suitable for medium- and low-temperature furnace roofs).
2. Furnace Body (Upper/Middle/Lower)
– Upper: High-alumina bricks (Al₂O₃ 65%-75%), clay-high-alumina composite bricks;
– Lower Middle: Dense high-alumina bricks (Al₂O₃ 75%-85%), corundum-mullite bricks (Al₂O₃ ≥90%, suitable for large blast furnaces);
– Special operating conditions (high-basicity slag): Magnesia-alumina spinel bricks (MgO 15%-30% + Al₂O₃ 60%-75%), with stronger resistance to slag erosion.
3. Furnace Waist and Abdomen
Corundum bricks (Al₂O₃ ≥95%), magnesia-alumina spinel bricks, corundum-silicon carbide bricks (Al₂O₃ 80%-90% + SiC 5%-15%).
4. Hearth (Sidewalls/Bottom)
– Hearth sidewalls: Magnesia-carbon bricks (MgO 70%-80% + C 10%-20%), Alumina-magnesia-carbon bricks (Al₂O₃ 20%-30% + MgO 50%-60% + C 10%-15%), combining the slag resistance of magnesia with the thermal conductivity/impermeability of graphite;
– Hearth bottom: Semi-graphite carbon bricks, graphite carbon bricks (C ≥90%), with a clay brick/high-alumina brick insulation layer at the bottom. The upper carbon brick layer must have low porosity and high bulk density to prevent molten iron penetration.
5. Tunnels (Tunnel Bricks/Surrounding Lining Bricks)
Silicon nitride-bonded silicon carbide bricks (Si₃N₄ 10%-20% + SiC ≥70%), reaction-sintered silicon carbide bricks (SiC ≥85%), and corundum-silicon carbide-carbon bricks in some applications.
6. Taphole/Slag Taphole (Trough/Lending Bricks)
Magnesium-carbon bricks (trough lining bricks), aluminum-carbon bricks (around the taphole), silicon nitride-bonded silicon carbide bricks (critical parts of the trough), and the core of the taphole is formed on-site using ramming mix (alumina-carbon, magnesia-carbon).
