The blast furnace tap trough system consists of a main tap trough, branch troughs, and slag troughs. It is an important system to realize the separation of molten iron and slag in the blast furnace. With the enlargement of iron-making blast furnaces and the development of high-temperature and high-pressure technology, higher requirements have been placed on the service life and iron flux of the blast furnace tap trough. The trough material is the main factor affecting the performance of the blast furnace tap trough. Its high-temperature resistance, thermal shock resistance, erosion resistance, erosion resistance, and other properties directly affect the iron flux and service life of the blast furnace tap channel. This in turn affects the production cost and labor intensity of the entire production process.
Refractory Material Al2O3-SiC-C Castable for Tap Trough
At present, the refractory materials used in the blast furnace tap trough are mainly Al2O3-Si C-C castables. Although it has the advantages of good high-temperature mechanical strength, good resistance to slag erosion and permeability, good thermal shock resistance, and small changes in reburning. However, in the face of technological advancements such as increased molten iron temperature, increased iron tapping volume, prolonged iron tapping time, and faster-molten iron flow rate caused by modern large-scale blast furnace smelting. The original iron trench materials cannot meet production needs. Therefore, improving Al2O3-SiC-C castables or developing new refractory materials for blast furnace tap troughs are the research directions of many scholars.
Aluminum silicon carbide carbonaceous castables, which are unshaped refractory materials, are often used in blast furnace tap troughs, so they are also called trough castables. The blast furnace tap trough castable is made of fused corundum (or sintered corundum, special high-aluminum clinker) and silicon carbide. It is a high-performance refractory castable containing 90%-95% fixed carbon (or flake graphite), binder, and various admixtures.
Aluminum silicon carbide carbonaceous castable. The aggregate part can be made of one or two types of fused or sintered corundum, brown corundum, spinel, and bauxite clinker. Carbonaceous raw materials can be asphalt, coke, graphite, or electrode powder. The binding agent can be bonded clay, oxide micro powder or ultrafine powder, and pure calcium aluminate cement with good dispersion properties.
The blast furnace tap trough is a channel through which high-temperature molten iron or molten slag flows. Its refractory lining should have the following characteristics. These features are complementary to each other and should be compatible with each other.
- ① Strong resistance to erosion and erosion from molten iron and slag.
- ② Good thermal shock resistance and small change in volume after reheating.
- ③ Strong antioxidant capacity.
- ④ Easy to construct, can be baked quickly without bursting, and is easy to repair and dismantle.
- ⑤ When used, it does not produce harmful gases, does not stick to slag iron, and has a long service life.
Iron trench castable is a high-tech refractory castable with exquisite preparation technology and excellent performance, which can significantly increase the service life of the trench lining. The key issue is that the amount of construction water must be strictly controlled, operated carefully, and maintained carefully to achieve the expected purpose.
At the same time, the specific selection of tap trough castables also depends on the size of the blast furnace. Generally speaking, high-aluminum silicon carbide carbonaceous castables can be used for the main ditch, slag ditch, and slag line of small blast furnaces. Corundum silicon carbide carbonaceous castables can be selected for medium and large blast furnaces.
Erosion-resistant Molten Iron-Clad Aluminum Silicon Carbide Castable
Spheroidized ladle castable is an unshaped refractory material with high aluminum and silicon carbide materials as the main raw materials and refractory cement as the binder. It is widely used in molten running ladles, launders, and working linings of kilns. It has high strength and refractory resistance and has good impact resistance, corrosion resistance, wear resistance, and other properties. It has a long service life, convenient construction, and easy maintenance. It is suitable for the overall lining of ladles and is the refractory material of choice for spheroidized ladles.
Molten iron and slag react with the castable, resulting in chemical slag sticking. According to ASTM C01-91 Al2O3-SiO2 series castables, those with CaO content >2.5 are traditional cement-bound castables. The CaO content between 1.0% and 2.5% is low cement castable. The CaO content <1.0% is cement-castable. The lower the CaO content, the higher the temperature at which the liquid phase appears, and therefore the higher the fire resistance. The CaO content of the existing castable is 3.78%, which is a traditional high cement content castable. Aluminum silicon carbide castables are erosion-resistant, heat-exchange-resistant, refractory castables, and ladle castables.
The liquid phase of this material appears at a low temperature, about 1300°C. The temperatures of molten iron and slag are generally >1300°C, and the interface is prone to reaction at this time. For example, the components in the refractory material, especially the liquid phase in the matrix, easily react with CaO, SiO2, Fe2O3, etc. in the slag to form Al2O3-SiO2-CaO-Fe2O3 series low-melting materials. The molten iron, molten slag, and refractory materials are melted together to form sticky slag. The sticky residue that occurs in this form is strong and difficult to clean.
Development of Aluminum Silicon Carbide Refractory Castables for Tap Trench
Al2O3-SiC-C castable is the most widely used iron trench refractory material in my country. Improving the quality of Al2O3-Si C-C castables is an important factor in reducing the cost of molten iron and achieving efficient production. RS Unshaped Refractory Castable Manufacturer puts forward several suggestions based on the current development situation.
(1) Different companies have different compositions of molten iron and slag. The reasons why molten slag and molten iron corrode the iron trench materials should be analyzed based on the actual situation to achieve “prescribing the right medicine”.
(2) Using slag or other industrial waste residues as raw materials to prepare Al2O3-Si C-C castables has extremely high added value. At the same time, it can also solve problems such as waste residue accumulation and environmental pollution.
(3) Improve the production of Al2O3-Si C-C castables in the direction of green and environmental protection, and remove or replace toxic and harmful components in the raw materials. It not only achieves green production but also protects the health of workers.
(4) Many new Al2O3-Si C-C castables have been applied in enterprise blast furnace production, achieving mutual benefit and win-win results between scientific research and enterprises.