Hearth

The hearth is the critical lower section of a blast furnace structure, forming a refractory-lined basin that collects and temporarily stores the molten iron (hot metal) and slag produced during the smelting process. It is designed to withstand extreme temperatures, chemical corrosion from molten materials, and significant mechanical stress. The hearth's integrity is essential for the safe and continuous operation of the furnace, facilitating the periodic tapping of iron and slag through dedicated tap holes. The hearth receives the descending burden of reduced iron ore, coke, and flux. As these materials melt in the higher-temperature zones above, the resulting liquid iron, being denser, sinks to the bottom of the hearth, while the lighter slag floats on top. The hearth's refractory lining contains and protects the furnace shell from the molten materials. Cooling systems (often staves or sprays) manage the intense heat. The accumulated molten products are then drained at scheduled intervals through tap holes located in the hearth walls. Typical hearth dimensions include an inner diameter of 6000–15000 mm, a height of 3000–6000 mm, and a working volume of 100–500 m³. Operating temperatures range from 1450–1550 °C, with operating pressures of 1.0–1.6 MPa. The refractory lining thickness is typically 300–800 mm, with thermal conductivity of 1.5–3.5 W/(m·K) (ASTM C417) and compressive strength of 50–120 MPa (ASTM C133). The hearth weight ranges from 50–200 t. Tolerances on inner diameter and height are ±0.5% and ±0.3% respectively (ISO 2768-m). The shell material grade is Q345R (GB/T 713), and the lining material grade is NMA (YB/T 4111). Materials on file include carbon refractory bricks, graphite blocks, ceramic cup materials (e.g., silicon carbide), and a steel shell. Verify all model-specific values and standards with the legal manufacturer or supplier.

The hearth receives the descending burden of reduced iron ore, coke, and flux. As these materials melt in the higher-temperature zones above, the resulting liquid iron, being denser, sinks to the bottom of the hearth, while the lighter slag floats on top. The hearth's refractory lining contains and protects the furnace shell from the molten materials. Cooling systems (often staves or sprays) manage the intense heat. The accumulated molten products are then drained at scheduled intervals through tap holes located in the hearth walls.