What is The Function of SAF Water-Cooled Furnace Cover?

The SAF Water-cooled Furnace Cover is a core component of modern large-scale submerged electric furnaces (primarily used for producing ferroalloys, calcium carbide, ferrosilicon, and industrial silicon). It is a large, water-cooled steel structural component installed on top of the submerged arc furnace furnace body, typically composed of multiple water-cooled wall panels (water-cooled modules) assembled to form a closed or semi-closed furnace cover over the furnace chamber. It plays a crucial role in ensuring the safe, stable, efficient, and long-term operation of the furnace.

I. The Function of the SAF Water-Cooled Furnace Cover

What is it?

• Submerged electric furnaces are high-temperature electric furnaces used for smelting high-energy-consuming products such as ferroalloys, calcium carbide, ferrosilicon, and ferromanganese. Due to their extremely high internal temperatures (reaching over 2000℃), cooling and protection of the furnace structure are paramount.

• The water-cooled furnace roof/water-cooled furnace cover is one of the key cooling components of a submerged arc furnace, primarily used to protect the furnace top structure, extend equipment life, and improve operational safety.

• Function: It replaces traditional refractory furnace roofs, solving the problems of damage caused by high temperatures, high-temperature flue gas flow, dust, and high-intensity heat radiation. 

Main Functions:

1. Sealed Furnace Chamber: Enables semi-enclosed or fully enclosed operation, effectively collecting flue gas containing high concentrations of carbon monoxide for subsequent gas purification and utilization (such as power generation), resulting in both energy conservation and environmental protection.

2. Withstands Extreme Heat Loads: Through forced cooling with internal circulating water, the temperature radiated from the furnace opening, exceeding 1000°C, is reduced to a temperature that the metal materials can withstand for extended periods (typically, the surface temperature is below 200°C).

3. Protects Equipment and Personnel: Prevents direct damage from high temperatures and flames to critical equipment such as the upper electrode system, handles, and feed pipes, and improves the operating environment in front of the furnace.

4. Extends Furnace Life: Its own lifespan is extremely long (usually synchronized with the furnace life), avoiding the inconvenience and downtime losses associated with frequent repairs or replacements of traditional refractory furnace tops.

II. Characteristics of Water-Cooled Furnace Cover Structure

A typical water-cooled furnace cover system for an electric submerged arc furnace includes:

1. Water-cooled wall panels/modules:

• Structure: A densely packed pipe array (membrane wall) welded from boiler steel pipes (e.g., 20# steel) or a water tank structure (box wall) welded from steel plates.

• Advantages: Membrane wall structures offer high strength, good sealing, and uniform cooling, making them the current mainstream.

• Surface Treatment: Anchors are typically welded to the fire-exposed surface, and a thin layer (approximately 30-50mm) of refractory and wear-resistant castable is poured or sprayed to further resist high temperatures and material erosion and corrosion.

2. Segmentation & Assembly: 

• The furnace cover is typically divided into a central cover (surrounding the electrodes) and peripheral covers. The central cover is often further divided into three or more segments depending on the number of electrodes.

• Modules are connected by bolts and equipped with flexible sealing devices (such as packing, ceramic fiber rope, etc.) to accommodate thermal expansion and contraction and ensure airtightness. 

3. Water Cooling System:

• Circulation Loop: Each module has independent inlet and outlet water pipes, connected in parallel to the main inlet and outlet water header to ensure uniform water flow distribution.

• Water Quality Requirements: Softened water or demineralized water must be used to prevent scaling and pipe blockage, which could lead to cooling failure and pipe bursts.

• Safety Monitoring: The system is equipped with flow, temperature, and pressure sensors and alarm devices to monitor the cooling status in real time. The return water typically has interlock alarms for temperature rise and flow rate decrease, automatically cutting off power and shutting down the furnace in severe cases.

4. Integrated Accessory Installation Ports: 

The submerged arc furnace cover has pre-drilled electrode holes (equipped with water-cooled electrode sealing sleeves), feed pipe interfaces, flue interfaces, observation holes/maintenance doors, and explosion vents.

III. Working Principle: 

The core principle is to use water as the cooling medium to continuously and efficiently remove high-temperature heat.

Low-temperature soft water (~30-40℃) enters each module from the main pipe at the bottom of the furnace cover.

Water flows at high speed within the pipes, absorbing a large amount of radiant and convective heat received by the furnace cover from the furnace chamber.

The water temperature rises after heat absorption (typically, the return water temperature is controlled below 50℃, with a temperature rise not exceeding 20-30℃), and it is discharged through the main return pipe into an external cooling system (such as a cooling tower or plate heat exchanger) for cooling before being recycled.

This process is continuous, ensuring that the metal structure of the furnace cover remains within a safe temperature range.

Precautions:

1. The water-cooled furnace cover is highly dependent on the water cooling system of the submerged electric furnaces: A water outage or water circulation failure could lead to catastrophic accidents such as furnace cover burn-through or explosion within minutes. Therefore, backup power and emergency water sources are essential.

2. Strict water quality management: Scale is a hidden killer; a strict water quality treatment and monitoring system must be established.

3. High manufacturing and installation requirements: Welding quality must be absolutely reliable and leak-free. Proper sealing is crucial during installation.

The SAF water-cooled furnace cover is a landmark component signifying the shift in modern submerged arc furnace technology from "extensive" to "precision, safety, and environmental protection." It transforms the challenge of extreme high temperatures into a controllable engineering problem, making it an indispensable key piece of equipment for achieving large-scale, enclosed, automated, efficient, and green production in submerged arc furnaces. Its stable operation hinges on a "reliable water-cooling system" and "meticulous management."