With the rapid development of industrialization, the amount of refractory waste, a core consumable in high-temperature industries such as steel, cement, and glass, has been increasing year by year. According to data, China produces approximately 8-9 million tons of waste refractory materials annually, but only about 30% is utilized. Efficiently reusing this waste has become a key issue in the industry’s green transformation. This article systematically explores the recycling and reuse of waste refractory materials, combining market trends with technological advances.
Regeneration technology path of waste refractory materials
- Physical Classification and Direct Utilization
After dismantling, scrap refractory materials can be directly downgraded and reused if they are structurally intact and not severely corroded. For example, the permanent clay brick layers removed from steel mill torpedo tank cars can be directly reused in non-critical parts of similar equipment. Selected magnesia carbon bricks can be re-used in converter patching materials. This method is low-cost, but its applicability is limited, primarily used in low-value-added scenarios.
- Crushing and Sorting and Primary Recycling
Through physical processes such as crushing, screening, and magnetic separation, scrap materials are processed into granules or powders of varying sizes for use as admixtures in new products. The general process for producing recycled products using the primary recycling method is as follows: scrap refractory materials → sorting and crushing → screening → sized materials → incorporation into new products. For example:
Metallurgical auxiliary materials: Crushed scrap magnesia carbon bricks can be used as a slag-forming agent in LF refining furnaces, replacing light-burned dolomite and improving desulfurization efficiency.
Monolithic Refractory Materials: Waste MgO-carbon brick particles can be used as self-flowing castables or repair materials, reducing costs by over 30%. For example, crushing waste MgO-carbon bricks into various particles and adding them to the EBT filler at the taphole of an electric arc furnace can achieve a self-flowing rate of 95%, which is at least as high as that of the original filler. Recycling spent Al₂O₃-MgO·Al₂O₃ castables can be used as repair and gunning materials after recycling.
Slag Splashing Furnace Material: Waste MgO-carbon brick particles replace magnesia sand and perform excellently in the converter slag splashing furnace protection process.
- Chemical and Physical Advanced Treatment
For high-value-added waste materials, chemical cleaning, high-temperature heat treatment, or impregnation are required to remove impurities and restore their properties. For example:
Recycled Aggregate Extraction: Chemical reagents are used to separate high-purity aggregates such as corundum and mullite from castable lining residues, replacing virgin raw materials at a cost of only 65% of the original material.
Metal purification: Extract metallic chromium from chromium-containing waste bricks to achieve high-value utilization of resources.
Typical application scenarios and cases
- Closed-Loop Utilization in the Steel Industry
Recycled Magnesia Carbon Bricks: Baosteel crushes waste magnesia carbon bricks and mixes them with 90% virgin material. The resulting recycled bricks have properties close to virgin products and are used in electric furnace slag lines. Many Japanese steel mills have achieved a 50-100% utilization rate for used refractory materials. In the Japanese steel industry, waste refractory materials are primarily used as slag mixes and molding sand substitutes. For example, unburned magnesia bricks for the electric furnace melt pool are produced using 85% recycled material and 15% virgin material; magnesia carbon bricks for the electric furnace slag line are produced using 90% recycled material and 10% virgin material; and RH low-fired magnesia-chrome bricks are produced entirely from recycled material. Kurosaki Steel has developed immersion nozzle bricks using waste corundum-graphite products as raw material; and Kashima Steel has developed a process for reusing slide bricks.
Ladle Casting Material: Jigang crushes waste slide bricks and replaces high-alumina bauxite for use in iron channel ramming material, increasing iron throughput by 15%.
Metallurgical Auxiliary Materials: The United States uses waste dolomite bricks as soil conditioners and slag-forming agents, achieving both environmental and economic benefits.
Valoref, a French company, utilizes a wide range of technologies and recycling methods for waste refractory materials from industries such as glass, steel, chemicals, and waste incineration, achieving a 60% recycling rate for refractory materials used in French glass furnaces by 1997.
The utilization rate of waste refractory materials in my country is relatively low, but significant progress has been made in recent years, particularly in the metallurgical industry. Waste refractory bricks and monolithic refractory materials are commonly used for hot repair of furnace linings, as casting agents for opening holes, and as raw materials for the manufacture of magnesia-carbon bricks. Waste alumina-carbon bricks can be used to manufacture slide bricks, submerged nozzle bricks, protective sleeves, and other materials.
- Expansion in the Building Materials and Ceramics Industry
Recycled Concrete Aggregate: Waste refractory brick particles can be used in roadbeds or building insulation materials, reducing natural resource consumption.
Ceramic Kiln Furniture Recycling: Beijing Tongda Company crushes waste silicon carbide saggers and uses them as castable aggregate, achieving performance standards while reducing costs by 20%.
- Innovative Applications in the Environmental Protection and Energy Industries
Incinerator Lining Repair: French company Valoref uses chemical welding technology to repair waste slats, extending their service life.
High-Temperature Insulation Material: Processed waste aluminum silicate fiber is used in the insulation layer of industrial kilns, reducing thermal conductivity by 10%.
Technological challenges and development trends
- Key Technical Bottlenecks
Impurity Separation is Difficult: Scrap materials are often mixed with metal slag, permeation layers, and other materials, necessitating the development of efficient magnetic separation and chemical cleaning processes.
Insufficient Performance Stability: Excessive inclusion of recycled materials can easily lead to product performance fluctuations, necessitating optimization of formulations and process parameters.
- Drivers of Industry Transformation
Policy Guidance: Policies such as China’s “Guidelines for Emergency Emission Reduction in Heavy Pollution Weather” are forcing companies to increase recycling rates.
Economic Demand: Rising prices for refractory raw materials (e.g., magnesia costs have increased by an average of 8% annually) are driving the use of recycled materials in place of virgin materials.
- Future Trends
Intelligent Sorting: Introducing AI visual recognition technology to improve waste sorting efficiency.
High-Value Utilization: Developing nano-scale micropowders (e.g., waste corundum powder for ceramic coatings) and expanding into the new energy sector.
The recycling of waste refractory materials has evolved from simple crushing and blending to refined, high-value production. Through physical classification, chemical purification, and cross-industry collaborative innovation, the dual goals of resource recycling and cost reduction and efficiency improvement can be achieved. In the future, with technological breakthroughs and policy support, recycled refractory materials are expected to occupy a more core position in the green industrial system and promote the implementation of the “dual carbon” goals.
