Blast Furnace Slag

What is blast furnace slag

Blast furnace slag is a kind of waste slag discharged from the blast furnace during pig iron smelting. When smelting pig iron in a blast furnace, the raw materials added from the blast furnace include iron ore and fuel (coke), as well as flux. When the furnace temperature reaches 1400 to 1600°C, the flux reacts with iron ore at high temperature to produce pig iron and slag. Blast furnace slag is composed of gangue, ash, flux and other impurities that cannot enter the pig iron. It is a fusible mixture. From the perspective of chemical composition, blast furnace slag is a silicate material. Every 1t of pig iron produced, the discharge of blast furnace slag varies with the grade of ore and the smelting method. For example, when using lean iron ore to produce iron, 1.0 to 1.2 tons of blast furnace slag is produced per ton of pig iron; when using rich iron ore to produce iron, only 0.25 tons of blast furnace slag is produced per ton of pig iron. Due to the improvement of modern ore dressing and iron making technology, the amount of blast furnace slag produced per ton of pig iron has been greatly reduced.

Classification

Due to changes in the variety and composition of iron-making raw materials and the influence of operating process factors, the composition and properties of the slag are also different. According to the types of pig iron smelted, blast furnace slag can be divided into casting pig iron slag, steel-making pig iron slag and special pig iron slag. According to the amount of alkaline oxides in the chemical composition of blast furnace slag, blast furnace slag can be divided into alkaline slag, neutral slag and acid slag.

Application

Blast furnace slag can be processed into valuable materials with multiple uses by various processes. Processed into slag crushed stone can replace natural sand and gravel, as the main raw material for concrete, reinforced concrete and pre-stressed reinforced concrete below 500, heat-resistant concrete aggregates with working temperature below 700 ℃, wear-resistant, non-slip highways, racing tracks, Auxiliary materials for airstrips, railway ballast, tunnel filling and foundation cushion filling, sewage treatment media, etc. After blast furnace slag is quenched with a large amount of water, it can be made into fine-grained slag containing mainly glass body, which has potential hydraulic cementing properties. Under the action of activators such as cement clinker, lime, and gypsum, it shows hydraulic cement The setting performance is a high-quality cement raw material. 70% to 80% of the cement produced in my country is mixed with different amounts of water slag. Water slag can also be used as insulation materials, wet milling and wet grinding slag, concrete and road engineering fine aggregates; soil improvement materials, etc.

Hot-melt slag can be processed into porous expanded slag. After being crushed and sieved, it becomes concrete lightweight orthopedics, which can also be processed into particles with micropores, smooth surface and different sizes.

Expanded beads are high-quality lightweight concrete aggregates, which can save 20% of cement compared with expanded slag; they can also be used as cement mixing materials, road materials, thermal insulation materials, etc.

Slag wool can be produced by blowing compressed air or high-pressure steam into a stream of hot molten slag. Used as heat preservation, sound absorption, fireproof materials, etc.

In addition. Blast furnace slag can also be used as raw materials for cast stone, glass-ceramics, fertilizer, enamel, ceramics, etc.