Technology for Producing Mineral Wool from Blast Furnace Slag

 

Technology for Producing Mineral Wool from Blast Furnace Slag

Blast furnace slag is a by-product generated during the ironmaking process, and its output is substantial. Using blast furnace slag to produce mineral wool products not only makes full use of this resource but also reduces environmental pollution caused by slag, effectively turning waste into value. The production process of mineral wool mainly consists of four stages: melting, fiberization, fiber collection, and forming. According to the different melting processes, the technology can be divided into the cupola method and the direct production method using blast furnace molten slag. The difference between the two lies in the raw materials and the melting equipment used.

Cupola Method

The cupola method uses cold blast furnace slag as the main raw material, with coke as the fuel. A suitable amount of modifiers (such as limestone or fly ash) is added and melted in the cupola for conditioning. However, this method has several drawbacks:

• Large amounts of flue gas and dust are generated during production, leading to environmental pollution.

• Since cold slag is used as feedstock, additional fuel is required for remelting. Producing 1 ton of mineral wool consumes approximately 400 kg of coke, increasing both energy consumption and production costs.

• The resulting mineral wool tends to have a high shot content, coarse fiber diameter, and poor hand feel.

Direct Production Method Using Molten Blast Furnace Slag

In this method, molten blast furnace slag is used as the primary raw material. Liquid slag from the blast furnace is introduced into a heating and conditioning furnace, where modifiers are added. Temperature and composition adjustments are achieved using electrodes or gas burners. The conditioned melt is then transformed into mineral wool fibers through a fiber-forming system, followed by fiber collection and post-processing to produce mineral wool products with various properties and applications.

Comparison Between the Two Processes

Compared with the cupola method, the direct production method with molten slag can recover more than 80% of the slag’s sensible heat. Its energy consumption is less than 30% of the cupola method, and production costs are only 60–80% of those in the cupola process, giving it strong market competitiveness. At present, the main technologies developed domestically and internationally for the direct production of mineral wool from molten blast furnace slag include:

• JFE’s blast furnace slag mineral wool production technology,

• Dalian Environmental Protection Design Institute’s “one-step” mineral wool production process,

• Hebei University of Science and Technology’s direct fiber-forming technology.

Economic and Environmental Benefits

For steel enterprises, blast furnace slag is mostly used for cement production, which has low added value. Using blast furnace slag—particularly molten slag—to produce mineral wool offers a new path for expanding non-steel industries and increasing profitability. Currently, the market price of mineral wool ranges from 2,500 RMB per ton to over 10,000 RMB per ton. Additionally, the process allows full recovery of the sensible heat in molten slag, offering significant environmental benefits. Therefore, from economic, environmental, and social perspectives, producing mineral wool from blast furnace slag is a highly promising, high-value-added utilization model.