News Date:2017-08-10 14:09:14
Granulated blast furnace slag grinding in ball mills is performed almost exclusively in closed circuit with a high-efficiency separator. A drying chamber is installed upline of the mill for predrying the granulated blast furnace slag or slag cement. This grinding method has now been used for decades for the production of slag cements, achieving the required product qualities without problems, but with comparatively high energy consumption rates. chaeng has built plants for intergrinding clinker and granulated blast furnace slags worldwide in recent decades and has recently also installed tube mills for the sole grinding of granulated blast furnace slag. Figure 8 shows a tube mill for grinding granulated blast furnace slag that is located in a plant which has now been grinding granulated blast furnace slags with chaeng machines for over 50 years. The latest ball mill obustness and simple operation.
Alongside the ball mill, the vertical roller mill has established itself in recent years for granulated blast furnace slag grinding. The advantages of this machine compared with the slag ball mill are immediately apparent: this type of mill combines all the main processes, namely drying, grinding and separation in a single unit, which also offers significant benefits thanks to its energy efficiency. The flowsheet of a vertical roller mill grinding plant already built is shown in pic. Wear plays a significant role in granulated blast furnace slag grinding. This depends essentially on the concentration of iron oxide. Since iron fractions are very difficult to cornminute in roller mills due to their plasticity, they become concentrated in the grinding circuit, causing a further increase in the wear rates. In order to avoid these effects or at least to control them, thorough removal of the iron is very important. The flowsheet shows three removal points. First the iron is extracted by magnets above the conveyor before the mill feed point. Further removal of the iron takes place at the magnet in the chute between the mill outlet and the circulating bucket elevator. The third extraction point is before the circulating material inlet to the separator. Another point to remember when grinding granulated blast furnace slag in roller mills is that the exit gas from the grinding plant has a high water vapour content. Its temperature must therefore be prevented from dropping below the dew point and plant components such as circulating bucket elevators, chutes and Fluidors must be carefully insulated or even heated to prevent clogging. With properly designing, a roller mill plant offers the advantage of very simple operation, as only one albeit slightly more complex, machine has to be operated. Contrary to earlier views, it has been proven in granulated blast furnace slag grinding plants built by chaeng that vertical roller mills not only reduce the specific energy consumption by around 50% compared with a ball mill but also achieve high product finenesses of up to 6000 Blaine and very high availabilities. The number of these plants that are either in operation or currently being built proves that the roller mill can be regarded as a proven product that has established itself on the market.
