Slags blast furnace

During the production of iron, iron ore, iron scrap, and fluxes (limestone and/or dolomite) are charged into a blast furnace along with coke for fuel. The coke is combusted to produce carbon monoxide, which reduces the iron ore to a molten iron product. This molten iron product can be cast into iron products, but is most often used as a feedstock for steel production [ 12,35-48]. 

Blast furnace slag (BFS) is a nonmetallic co-product produced in the process. It consists primarily of silicates, aluminosilicates, and calcium-alumina silicates. The molten slag, which absorbs much of the sulfur from the charge, comprises about 20% by mass of iron production. 

---

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

Insulation. Impure sdiceous limestone and blast-furnace slag are the main raw materials for making rock-wool insulation bats and peUets (see Insulation, thermal). 

Blended hydraulic cements are used to conserve energy. They are intimate and uniform blends of tine materials such as Pordand cement, ground blast furnace slag, dy ash, and other po22olans, ie, tine, reactive sUica sources. ASTM C595 Hsts five classes or types. 

Type IS Pordand cement and blast furnace slag cement... 

CaO(from limestone) + Si02 CaSi03(blast furnace slag)... 

Fig. 2. Cement 2ones in the CaO—AI2O2—Si02 system (5) where B represents basic blast-furnace slag D, cement compositions which dust on cooling E, compositions showing no tendency to set G, aluminous cement and PC, Pordand cement.

Zinc Zinc is processed very similarly to copper and lead. The zinc is bound in the ore as ZnS, sphalerite. Zinc is also obtained as an impurity from lead smelting, in which it is recovered from the blast furnace slag. 

Hochofen, m. blast furnace, -anlage, /. blastfurnace plant, -betrieb, m. blast-furnace operation. gas, n. blast-furnace gas. -guss, m. blastfurnace cast iron, -koks, m. blastfurnace coke, metallurgical coke, -schlacke, /, blast-furnace slag, -schmelze, /, blastfurnace smelting, -verfahren, n. blastfurnace process. 

O. G. Benge and W. W. Webster. Evaluation of blast furnace slag slurries for oilfield application. In Proceedings Volume, pages 169-180. lADC/SPE Drilling Conf (Dallas, TX, 2/15-2/18), 1994. 

K. M. Cowan and A. H. Hale. High temperature well cementing with low grade blast furnace slag. Patent US 5379840, 1995. 

K. M. Cowan and T. R. Smith. Application of drilling fluids to cement conversion with blast furnace slag in Canada. In Proceedings Volume, number 93-601. CADE/CAODC Spring Drilling Conf (Calgary, Canada, 4/14- /16) Proc, 1993. 

Blast furnace slag, concentrates, ore mill tailings, plating sludge... 

At some plants the blast furnace dust is recycled as feedstock to the sinter plant. At plants without sintering operations, blast furnace dust is sometimes mixed with other byproduct residues, briquetted, and recycled back to the blast furnace. In other plants, the dust is landfilled or stockpiled.1 Several techniques are available for removing the zinc and lead. The majority of blast furnace sludge is land disposed as solid waste or stockpiled. Because of the similarity between wastewater sludges generated by sinter plants and blast furnaces, these streams are commingled and cotreated.1 The blast furnace slag is cooled and processed to be reused for various applications such as onsite in-land reclamation and landfill construction. 

As mentioned above, approximately 7% of the total sulfur present in lead ore is emitted as S02. The remainder is captured by the blast furnace slag. The blast furnace slag is composed primarily of iron and silicon oxides, as well as aluminum and calcium oxides. Other metals may also be present in smaller amounts, including antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, mercury, molybdenum, silver, and zinc. This blast furnace slag is either recycled back into the process or disposed of in piles on site. About 50 to 60% of the recovery furnace output is slag and residual lead, which are both returned to the blast furnace. The remainder of this dross furnace output is sold to copper smelters for recovery of the copper and other precious metals. 

Air-cooled blast furnace slag. If the liquid slag is poured into beds and slowly cooled under ambient conditions, a crystalline structure is formed, and a hard, lump slag is generated, which can subsequently be crushed and screened. 

---