New type tubular water cooling furnace cover
The Tubular Water Cooling Furnace Cover for Electric Arc Furnace (EAF) is a specialized variant of EAF water-cooled covers, characterized by its core heat-dissipating structure—arranged metal tubes (tubular bundles) instead of integral hollow panels. This design optimizes heat exchange efficiency, enhances structural rigidity, and simplifies maintenance, making it particularly suitable for medium-to-large EAFs (e.g., 50-200t steelmaking EAFs, high-power ferroalloy refining EAFs) that face intense arc radiation and frequent thermal shocks.
Compared to panel-type water-cooled covers, the tubular structure offers unique advantages tailored to EAF operating conditions:
- Tubular Heat-Dissipating Core: The cover’s inner heat-absorbing layer consists of seamless steel tubes or stainless steel tubes (arranged in parallel, spiral, or grid patterns). This design increases the heat exchange area (30-50% larger than panel-type covers) and ensures uniform cooling, avoiding local hot spots caused by concentrated arc heat.
- Modular Tube Bundles: Tubes are grouped into removable modular bundles (e.g., 3-5 tubes per module). If individual tubes are damaged (e.g., by molten splashes), only the affected module needs replacement—reducing maintenance time and cost (vs. replacing the entire panel in panel-type covers).
- Reinforced Frame Integration: Tubes are welded or bolted to a high-strength steel frame (Q355B or 16Mn), forming a rigid structure that resists deformation from thermal expansion (critical for EAFs that require frequent cover lifting/tilting).
- Optimized Sealing at Electrode Holes: The tubular structure around electrode holes uses double-layer tube rings (inner tube for cooling, outer tube for fixing high-temperature gaskets), enhancing sealing performance and preventing furnace gas leakage at this high-wear area.
It follows the closed water circulation principle but with enhanced heat transfer efficiency due to the tubular design:
- Low-temperature cooling water (30-40°C, softened/demineralized to avoid scaling) is distributed to each tubular bundle via a header pipe (installed on the cover’s outer frame).
- Water flows through the tubes, absorbing heat from high-temperature furnace gas (1600-2200°C) and arc radiation—heat transfer occurs directly through the tube walls (thinner than panel layers, improving heat conduction).
- Heated water (55-60°C) converges in a return header, is sent to a heat exchanger/cooling tower for temperature reduction, and is recycled back to the cover—forming a continuous, high-efficiency heat dissipation cycle.
Material choice is critical to withstand EAF-specific challenges (high temperature, corrosion from acidic furnace gas, molten slag erosion). The table below details materials for core parts:
Parameters are customized based on EAF capacity, power, and smelting process (e.g., ultra-high power (UHP) steelmaking, ferroalloy refining). Below are representative specifications for a 100t UHP EAF:
Compared to panel-type water-cooled covers and traditional refractory covers, the tubular design offers targeted benefits for EAF operations:
- Higher Heat Exchange Efficiency: The increased tube surface area reduces outlet water temperature by 5-10°C (vs. panel-type covers), lowering cooling system load and saving energy.
- Stronger Thermal Shock Resistance: Tubes have better flexibility than rigid panels, absorbing thermal expansion/contraction without cracking—critical for EAFs that undergo frequent heating (smelting) and cooling (charging/tapping) cycles.
- Lower Maintenance Cost: Modular tube bundles allow partial replacement (costing 10-20% of full cover replacement) and faster repair (1-2 hours vs. 8-12 hours for panel-type covers).
- Better Adaptability to Large EAFs: The rigid tubular-frame structure supports larger cover sizes (e.g., 5-6m diameter for 200t EAFs) without deformation, which panel-type covers struggle to achieve.
It is most effective in EAFs with high heat intensity and frequent operational adjustments:
- Ultra-High Power (UHP) Steelmaking EAFs (50-200t): Handles intense arc heat (2000-2200°C) and frequent cover lifting for scrap charging; CO recovery rate ≥98% due to good sealing.
- High-Power Ferroalloy Refining EAFs (e.g., low-carbon ferrochrome, ferrosilicon): Resists corrosion from chrome/manganese-rich slag (with 316L tubes) and reduces alloy loss via stable temperature control.
- Medium-Sized Non-Ferrous Smelting EAFs (e.g., copper/nickel alloy): Modular design simplifies maintenance in smelting processes with frequent slag cleaning.
To maximize service life and avoid safety risks (e.g., tube rupture leading to water leakage into the furnace), strict maintenance is required:
- Tube & Header Inspection: Check for water leakage at tube joints and headers using a pressure gauge—pressure drops ≥0.05 MPa indicate potential leaks.
- Temperature Monitoring: Use an infrared thermometer to scan tube surfaces; local temperatures >100°C suggest tube blockage (due to scaling or slag adhesion).
- Electrode Hole Sealing Check: Inspect graphite packing for wear; replace if furnace gas leakage (detected by a CO detector) exceeds 0.05%.
- Lifting Mechanism Lubrication: Apply high-temperature molybdenum disulfide grease to hinges and hydraulic cylinders to prevent jamming during cover movement.
The water cooling structure in the furnace cover is composed of a number of tightly arranged seamless pipes.
Each steel pipe is round. The water-cooled furnace cover of this structure is not easy to leak and easy to maintain.
The water cooled furnace cover of electric arc furnace adopts tubular frame water cooled furnace cover, and the water cooled cover is designed in two halves for easy replacement and transportation.
The water-cooled furnace cover comprises a tubular frame, a water cooling fast on the left half cover, a water cooling fast on the right half cover, a lime charging device, and a water-cooling support ring on the central small furnace cover. The tubular frame is made of seamless steel pipes, which are not only used as the strength requirements of the structural parts, but also as the main inlet and return water pipes. Connect all cooling water circuits through the main inlet and return pipes. The left and right half water cooling blocks are connected to the frame by bolts, and the water cooling fast forward and return water are connected to the main inlet and return water pipes by branch steel pipes to cool the two half water cooling blocks.
The lime charging device is installed on the furnace water cooling cover. The device is composed of a receiving hopper, a chute, etc. The lower part of the chute is designed as a water cooling structure. When no lime is added, the sluice valve is closed to prevent the flue gas from overflowing from the lime charging device.
The water-cooled support ring of the central small furnace cover is made into an inverted cone structure, and water cooling is also adopted. The water inlet and return pipes are connected to the main water inlet and return pipes.
Partial plane diagram of tubular water-cooled furnace cover:
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