BLAST FURNACE In the blast furnace iron ore is melted and reduced by coke and limestone. The materials are charged from the furnace top to form layers. Hot blast blown from furnace bottom burns coke and reduces iron ore to produce molten iron at the bottom. Limestone combines with impurity in the ore to produce slag on the molten iron at the bottom. The blast furnace generally consists of several major portions like Shaft, Belly, Bosh, Tuyere, Tap hole and Bottom. Sino-Global offers products carefully selected based on the refractory materials, which are appropriately applicable for respective portion. The generic requirements from blast furnace refractories are summarised below: Impact resistance and abrasion resistance against material charging. CO gas resistance. Alkali resistance. Thermal spalling resistance. Corrosion resistance against molten iron and slag. Resistance against molten iron penetration. In addition to bricks for blast furnace body Sino-Global supplies high quality consumables like tap hole clay (for plugging tap hole) and trough materials (for lining iron troughs).
SILICON NITRIDE BONDED SILICON CARBIDE REFRACTORIES These materials are characterized by a manufacturing process that includes: blending coarse silicon carbide or Corundum (fused alumina) grains with ceramic and metallic powders, pressing or casting the mix to the final shape, and firing the green body at high temperature under Nitrogen. These products exhibit excellent strength, high thermal conductivity and thermal shock resistance, abrasion resistance, alkali and slag corrosion resistance. Silicon nitride bonded silicon carbide products are characterized by high corrosion resistance, high crushing strength, high refractoriness and stable chemical properties. Sino-Global supplies these products for blast furnace application under the brand name BLASICNIT. Brand name SGRL BLASICNIT A SGRL BLASICNIT B SiC (%) 70.0 70.0 Si 3N 4 (%) 22.0 20.0 Si (%) Max. 1.0 - AP (%) Max. 18.0 19.0 BD (g/cc) 2.60 2.58 CCS (MPa) 150.0 150.0 MOR (MPa) 40.0 30.0 HMOR (1400 Deg C / 30 minutes) (MPa) 50.0 40.0
SIALON BONDED REFRACTORY REFRACTORIES These consist of Silicon Carbide grains or or fused Alumina (i.e. Corundum) bonded by a SiAlON matrix. (a) Silicon Carbide based material outperforms the regular Silicon Nitride bonded materials on high temperature corrosion resistance by molten slags, metals and alkali vapour. (b) Fused Alumina based materials. They combine the positive features of the fused Alumina basis and the SiAlON bond. Compared to the best high alumina refractory materials, they show a superior hot mechanical strength and a lower wet ability and infiltration by molten slag and metal. Compared to Silicon carbide based - either SiAlON or Silicon Nitride bonded materials - they show an outstanding corrosion resistance by molten metals, a low thermal conductivity but nevertheless an outstanding thermal shock resistance. These unique refractory materials, installed in critical areas of blast furnaces, direct reduction furnaces or steel mills, provide since many years an excellent and reliable service to the Iron making industry. Sino-Global supplies these products for blast furnace application under the brand name BLASICALON & BLACORALON. Brand name SGRL BLASICALON SGRL BLACORALON Al 2O 3 (%) 5.0 80.0 SiC (%) 71.0 - N (%) 5.5 5.0 Fe 2O 3 (%) Max. 0.7 0.7 AP (%) Max. 16.0 15.0 BD (g/cc) 2.65 3.15 CCS (MPa) 150 135 HMOR (1400 Deg C / 30 minutes) (MPa) Alkali Resistance (K 2CO 3, 930 Deg C, 3 hrs, 2 cycles) (%) Typical 45.0 22.0 + 5.0 0 ~ +5.0
BLAST FURNACE TROUGH CASTABLES Trough castable" is a term generally used to define refractory castable materials used in the iron-making industry. Trough castables are typically used in blast furnace cast house troughs and runners, tilting spouts, torpedo ladle cars, iron transfer ladles, iron mixers, cupolas and induction furnaces. In this wide range of applications, trough castables are exposed to many wear mechanisms that during normal operation will cause the refractory castable to corrode and erode away. Some of these wear mechanisms include thermal shock, iron erosion and slag corrosion. Thermal shock relates to sudden and rapid changes in the temperature of a trough castable that may cause stresses to develop within the refractory material. These stresses can reduce the service life of the refractory lining through cracking and spalling. Iron erosion is caused by flowing molten metal mechanically eroding the exposed surface of the refractory castable. Molten iron may also attack the constituents such as silica and other oxides within the castable, and deteriorate the refractory properties of the material. Slag attacks the trough castable by forming lower temperature melting phases through various chemical reactions which makes the castable more susceptible to wear. Basically, trough castables are designed to resist these different wear mechanisms through the use of specific types of raw materials in the formulation of the trough castable. In this respect, trough castables typically comprise of alumina-silicon carbide-carbon. High alumina aggregate (such as fused alumina, sintered alumina or calcined bauxite) is the primary constituent in blast furnace trough castables. In addition to the alumina, silicon carbide and carbon, trough castables include calcium aluminate cement. Low levels of calcium aluminate cement are used to minimize reaction between the calcium aluminate within the cement and slag. Sino-Global offers trough castables under the TRUFCAST, TRUFCAST SEFLO and TRUFCAST Q brands.
RAPID DRYING & SELF FLOW CASTABLES, REPAIR COATING Brand name SEFLO QDRY COAT SEFQ Al 2O 3 (%) 68.0 70.0 58.0 60.0 SiC (%) Typical. 15.0 15.0 14.0 15.0 BD (g/cc) 110 Deg C 24 hrs 1450 Deg C 3 hrs 2.85 2.85 2.85 2.85 2.80 2.80 2.40 2.80 PLC 1450 Deg C, 3 hrs + 0.6 + 0.6 + 0.6 0 ~ +0.5 MOR (MPa) 110 Deg C 24 hrs 1450 Deg C 3 hrs 4.0 4.0 2.0 4.0 6.0 5.0 4.0 5.0 CCS (MPa) 110 Deg C 24 hrs 1450 Deg C 3 hrs 15.0 20.0 6.0 15.0 30.0 25.0 10.0 25.0 Note: The above are typical data and are not to be taken as binding specifications. Please contact us for latest specifications.
BLAST FURNACE TAPHOLE CLAY The new generation blast furnaces with large volumes operate at high top pressure, increased blast temperature, injection at tuyeres e.g. coal and oxygen. This has resulted in an increase in tapping rate, tapping temperature and duration of tapping. Such changes have prompted radical changes in the materials and applications of refractories in the BF cast house areas, particularly tap hole clay. The tap hole is prone to early erosion and therefore for obtaining a trouble free cast, a good and strong tap hole of requisite strength is required, for which a good quality tap hole clay is essential. Earlier in most of the blast furnaces hydrous mass was used, which doesn t provide strong tap hole. Particularly this hydrous mass, water bonded was found to be responsible for oxidizing the carbon lining around the tap hole, leading to breakouts. To achieve a trouble free tapping a constant tap hole length need to be ascertained. The expansion of the tap hole needs to be controlled with hot metal and slag volume. The delivery speed of the hot metal stream should have minimum possible variation. Any turbulence in the stream at the tap hole exit should be avoided. The operation and closing of the tap hole need to be smooth, to the extent possible. High temperature and Si content of the hot metal affects the performance of the tap hole clay adversely. Material design for tap hole clay has undergone a radical change. Superior grade Al2O3-SiC-C based anhydrous tap hole clays are put in regular use in medium to large size blast furnaces. Both silicious and aluminous aggregates are used along with various additives and binders. Phenolic resins, tar and various oils are used as binders along with Carbides (SiC) or nitrides (Si3N4) as additives. Carbides and Nitrides impart corrosion and abrasion resistance properties where it also improves sinter ability of the mix. These anhydrous tap hole masses maintain good tap hole length, offer smooth & controlled drainage of metal & slag and protect the hearth in tap hole region, the zet impulse of the tap hole is lowered, which reduces waering of trough lining. Slight expansion has been recognised as a desirable property as negative PLC (permanent linear change) leads to gap formation. The hearth should be empty as long as possible; otherwise the permeability of the blast furnace will be influenced negatively. This is influenced by 'Gun-up' to Knock-out' (GUTKO) time practiced in any individual plant. To achieve the best results the GUTKO time should optimum for any plant depending on the charging rate of the furnace, number of tap holes available and tap hole diameter.
BLAST FURNACE TAPHOLE CLAY Properties Properties 1000 2000 3000 PLUS Al 2O 3 20 30 30 30 Chemical compositions (%) SiC 25 25 30 35 Si 3N 4 - - 5 10 Bulk density (g/cm 3 ) 2.1 2.2 2.3 2.3 Permanent linear change (%) 1300 0 C x 3h ± 1.0 ± 1.0 ± 1.0 ± 1.0 Cold modulus of rupture (MPa) 1300 0 C x 3h 2-5 2-5 2-5 3-6 Cold crushing strength (MPa) 1300 0 C x 3h 6-12 6-12 6-12 6-15 Working volume of BF < 1000m 3 1000-2000m 3 2000-2500m 3 > 2500m 3 Installation Techniques In the classification, based on appearance, the tap hole clay is always in 'mud state'; the reason why, it is also called tap hole mud. It is applied by a electro-mechanically/hydraulically operated mud gun, the reason why, it is also called mud gun mass. The capacity of the mud gun largely depends on the pressure inside the blast furnace.the mud gun mass is extruded from mud gun into the tap hole through electro-mechanic/hydraulic pressure. Pressure gauge installed on the mud gun monitors the pressure being applied for the extrusion. A higher pressure reading reflects the excessive hardness of the material, where as, a lower pressure reading reflects the softness of the material. A good flowability help in formation of desired mushroom inside the blast furnace. Mud gun is removed after 5-10 minutes of the extrusion, once the tap hole clay is sintered on the hot face and seals the hole. For opening the tap hole for metal cast, drilling machine is used. An optimum drilling time is the reflection of a good quality tap hole clay. At the manufacturing end, this property is ascertained by evaluating the cold crushing strength of the coked material. Depending on the mud gun capacity, pressure being applied on mud gun, capacity of the drilling machine and GUTKO time, the tap hole clay is tailor made to cater the need of an individual plant.