What Does ” Two Grinding And One Firing” Mean In Cement Production
The production of cement can generally be divided into three processes: raw meal preparation, clinker calcination and cement production. The entire production process can be summarized as “two grinding and one firing”.
1. Raw meal grinding
Divided into dry and wet two. The dry method generally adopts a closed-circuit operating system, that is, after the raw materials are ground by a mill, they enter the powder separator for sorting, and the coarse powder is returned to the mill for further grinding operations, and most of the materials are dried and ground in the mill at the same time. The equipment used are tube mill, middle discharge mill and roller mill. Wet methods usually use open-circuit systems such as tube mills and baseball mills that do not return after one pass through the mill, but there are also closed-circuit systems with classifiers or curved screens.
2. Clinker calcination
The equipment for calcining clinker mainly includes vertical kiln and rotary kiln. Vertical kiln is suitable for factories with small production scale, and rotary kiln should be used in large and medium-sized factories.
Shaft kiln: a vertical kiln that does not rotate is called a vertical kiln. It is divided into ordinary shaft kiln and mechanized shaft kiln. Ordinary shaft kiln is manual feeding and manual discharging or mechanical feeding and manual discharging; mechanical shaft kiln is mechanical feeding and mechanical discharging. Mechanical shaft kiln operates continuously, and its output, quality and labor productivity are higher than ordinary shaft kilns.
Most foreign shaft kilns have been replaced by rotary kilns, but in the current Chinese cement industry, shaft kilns still occupy an important position. According to the requirements of building materials technology policies, small cement plants use mechanized shaft kilns to gradually replace ordinary shaft kilns.
3. Cement grinding
The fine grinding of cement clinker usually adopts the circular flow grinding process (ie closed circuit operation system). In order to prevent dust from flying in production, cement plants are equipped with dust collection equipment. Electric precipitators, bag filters and cyclones are commonly used dust collection equipment in cement plants.
Due to the adoption of new technologies and new equipment in the pre-homogenization of raw materials, the homogenization and transportation of raw meal powder, and the dust collection, especially the emergence of the decomposition technology outside the kiln, a new dry production process has emerged. Using this new process, the quality of clinker produced by dry method is no less than that of wet method, and the power consumption is also reduced, which has become the trend of the development of the cement industry in various countries.
Equipment In Cement Grinding Plant
Raw Meal Vertical Mill:
Limestone, clay raw materials and a small amount of calibration materials are crushed and then mixed in a certain proportion and then ground.
Rotary kiln calcination:
The raw meal is calcined in a cement industrial kiln until it is partially melted, and then cooled to obtain clinker with calcium silicate as the main component.
Cement clinker vertical mill:
Add gypsum and other mixed materials to the clinker and use the vertical mill to refine the finished cement.
Coal vertical mill:
It provides the required heat for the calcination of the rotary kiln and provides a strong guarantee for the production of cement clinker.