Industrial Solid Waste Recycling [ Slag ]

Source of Slag

Slag generally refers to the condensate which is polymerized at high temperature, such as water slag, blast furnace slag and so on. Slag generally comes from factories such as cement plants, thermal power plants, smelters, etc., mainly from the following sources:

• ① Oxides formed by oxygenation of various impurity elements (such as Si, Mn, P, etc.) contained in iron and steel (hot metal, scrap).
• ② The slagging materials such as lime, fluorite and dolomite, that are added to remove sulfur and phosphorus from molten iron.
• ③ Impurities brought in when ore, sinter, iron oxide scale and so on are added as oxidant or coolant.
• ④ The furnace lining refractories that have been eroded or washed down.
• ⑤ Sediment impurities brought by various raw materials.

Use of Slag

Slag plays an important role in industrial production, especially in some large factories, slag is extracted and processed into slag cement, slag fine powder, slag powder, slag Portland cement and slag cotton.

Blast furnace slag can also be used as raw materials for cast stone, glass-ceramic, fertilizer, enamel, ceramics and so on. Several uses of slag are described as below:

(1) Glass Ceramics

Glass-ceramic is lighter than aluminum and has high chemical corrosion resistance, heat resistance, wear resistance and mechanical strength, so it is a good electrical insulation material and decoration material.

The investment of glass-ceramic processing equipment is less, and the cost is lower than that of cast stone and ceramics, so it is a kind of promising material.

(2) Road Base or Cushion

The slag is crushed to form mixed slag, which is used as a material for building road base and cushion, and its flatness is better than that of mixed stone foundation. Some of the slag is porous material, which can play a certain role of thermal insulation, in addition, it can play a certain role of water storage in the area with high groundwater level, enhance the stability of the roadbed and prevent grouting.

The construction of slag paving is easy to operate and is not restricted by the season, especially in the rainy season, it is more convenient than lime soil.

(3) Slag Powder

The main use is to add cement and commercial concrete.

There are three utilization types of slag powder: additives type, admixture type and main admixture type. The main function is to improve the early strength of cement and concrete, improve the easiness of concrete, reduce the heat of hydration and so on.

Slag Processing Equipments

1. Crushing equipment

Slag needs to be crushed before it can be used in road base or cushion, the commonly used crushing equipment are: impact crusher, opposite roll crusher, cone crusher and slag mobile crushing plant etc.

2. Grinding Equipment

As a new admixture of high performance concrete, slag powder has the advantages of improving the compressive, tensile, shear, bending and other properties of concrete.

At present, the replacement of cement in concrete and cement products by slag powder has become the mainstream trend of the building materials industry. One of the main equipment of slag fine powder production line is the grinder.

(1) Hanging Roller Mill

Hanging roller mill slag powder processing plant is mainly composed of jaw crusher, bucket elevator, bunker, vibratory feeder, main grinder, fan, powder collector, bag dust collector and so on.

The process of producing fine slag powder by hanging roll mill is more popular in recent years, which is optimized for various iron and steel companies. This process can achieve low input and high output.

(2) Ball Mill

Ball mill slag fine powder processing plant mainly has roller press, ball mill, powder separator, dust collector and fans and so on.

The dried slag is fed into the mill through the metering and feeding equipment and grinded into fine powder in the mill. if necessary, a fine mill classifier can be installed in the mill to improve the fineness of the product, and the finished product can be transported to the finished product warehouse by pneumatic force.

Using ball mill to produce slag fine powder, the fineness adjustment is more flexible, and the particle shape and gradation are better, but the power consumption is higher.

With the expansion of the scale of industrial production, the emissions of waste stone, tailings and slag are rising linearly, and a large number of industrial solid waste emissions are bound to cause bad damage to the environment.