1 Overview

Water quenched blast furnace slag was superfine ground to prepare slag powder (specific surface area 400-450 m2 / kg), which was added into silicate cement as admixture to prepare 42.5#, and 52.5# slag silicate cement. The content of slag powder in cement can reach 60-70%, which can greatly reduce the production cost of cement. Slag powder has lubrication effect, pozzolanic effect and filling compaction effect, which can significantly improve the construction performance of fresh concrete, enhance the environmental erosion resistance and improve the durability.            

As a new green building material with good environmental performance, slag powder has been widely used in major cities in China. The development of blast furnace slag powder project in iron and steel enterprises is an effective measure to turn waste into treasure and develop circular economy, with considerable economic benefits.

2 Technology of slag ultrafine powder

(1)Short process technology with slag mill as the core is adopted for pulverizing, which integrates drying, grinding and sorting. The process is simple, covers a small area and reduces the use of auxiliary equipment.          

(2)Based on the development of coal mill and cement raw mill in recent years, arms slag mill has made significant adjustment in structural design in view of the main problems such as rolling, bed formation, wearing of vulnerable parts and sorting, etc. based on the development of coal mill and cement raw mill in recent years, the vertical slag mill is developed to meet the requirements of small and medium-sized slag powder production. It has compact structure, convenient maintenance and energy saving significant (40-50% lower power consumption than rod mill).    

(3)The process is simple, the resistance is small and the emission pollution is less.        

(4)Partial external circulation is adopted for material flow, which can reduce air volume and ventilation power consumption, facilitate slag iron removal and reduce equipment wear.      

(5)The noise of VRM is lower than 85 db, and the noise of the main induced draft fan is lower than 85 db by using muffler.

3 Technical process

Wet slag is transported to the slag silo by truck for storage, and the slag is lifted to the receiving hopper by the loader. Under the hopper, there are rod gate valve and electronic belt quantitative feeder. The roller type feeding amount is controlled by the electronic belt quantitative feeder, and sent to the slag mill through the large angle belt conveyor.            

The slag from slag storehouse enters slag mill through rotary feeder, grinds, dries and selects powder. The final product is collected by bag filter. The heat source for drying is provided by special hot blast stove. The slag fed into the mill is rolled by the roller and disc, and then thrown to the hot air nozzle on the edge of the grinding plate under the centrifugal force of the rotation of the grinding plate. The material enters the powder concentrator at the top of the mill under the high-speed jet hot air flow. After the separation by the high-efficiency powder concentrator, the coarse powder with larger particles falls back into the mill for regrinding, and the fine powder is taken out by the air flow and collected by the bag filter Products. In order to save the electric energy of grinding system and facilitate iron removal, part of the coarse powder discharged from the overflow device around the grinding plate is removed by a special iron remover, and then returned to the feeding belt conveyor by the belt conveyor and fed into the mill for regrinding.          

Finished slag is collected by bag filter and sent to the finished product warehouse by air chute and bucket elevator. It is designed to store the finished products in the inflatable bulk warehouse with a diameter of 15m. The superfine slag powder is delivered in bulk by the truck through the bulk equipment at the bottom of the warehouse. In order to facilitate the measurement of bulk superfine powder, a ground scale is directly set at the bottom of the warehouse to measure the ex factory products.