Cement grinding process and equipment

Cement grinding process and equipment

In the design and transformation plan argumentation of cement grinding process, it is not only necessary to consider whether the cement ingredient is mainly composed of raw materials with poor grindability such as slag, but also to consider whether to use good grindability mixed materials such as fly ash and power plant slag, as well as the requirements for producing ordinary Portland cement, composite Portland cement, slag cement and other cement varieties, and to choose appropriate cement grinding process forms and grinding equipment.

The common feature of different cement grinding processes is that slag must be ground into slag micro powder, with a specific surface area of 380m2/kg and 80% 50% micro powder particles μ m. Among them, 10 μ Ultrafine powder accounts for about 30% to 40%, fully utilizing the activity of slag powder, increasing the dosage of slag powder, improving cement performance, reducing clinker consumption, and achieving the goal of low-carbon and environmental protection. The following is a comparative analysis of several common cement grinding processes in China based on the different grinding characteristics of cement materials.

Ball mill separate grinding process flow

In the separate grinding system of ball mills, the process flow can be the first stage open circuit process of high precision and high yield tube mills, or the first stage closed circuit process of ordinary ball mills. One ball mill is used for grinding clinker and gypsum, while the other ball mill is used for grinding slag, which is then sent to the clinker powder warehouse and slag powder warehouse respectively for production according to the requirements of cement varieties. When grinding slag with a ball mill, the moisture content of the ground slag should be controlled below 2.0%. Therefore, drying equipment should be used for drying before grinding the slag.

Process characteristics

The ball mill separate grinding process has a simple production process and flexible production organization, which can achieve high slag grinding fineness and fully utilize the activity of slag powder, which is beneficial for improving cement strength. The disadvantage is low hourly production and high grinding power consumption. Using a ball mill system to produce slag powder, under the same process equipment conditions, the output of cement is reduced by about 40% to 50% compared to that of ground cement. When the specific surface area is controlled at 400m2/kg, the power consumption of the grinding system is about 65kWh/t; When the specific surface area is controlled at 500m2/kg, the power consumption of the grinding system is about 80kWh/t.

Separate grinding process using roller press and ball mill

In recent years, a roller press+ball mill combined separate grinding process has emerged, using a roller press+ball mill combined separate grinding system to achieve separate grinding of clinker powder and slag powder. When grinding slag, a hot air furnace is used to provide hot air, and the improved V-shaped powder concentrator achieves online drying, simplifying the production process. The ball mill grinding system can adopt a common ball mill primary closed circuit system and a high precision and high yield mill primary open circuit system.

Process characteristics

The characteristics of roller press and ball mill are to eliminate the Edge effects of roller press and meet the requirements of Supersaturation feeding of roller press. At the same time, a low-pressure large circulation process can be adopted to reduce the working pressure of the roller press, extend the service life of the roller sleeve, and improve the operating rate. According to information, this process increases the production of slag by more than 40% compared to ordinary ball mills, and reduces the power consumption of slag grinding by 10% to 15%.

Separate grinding process consisting of roller press, ball mill, and vertical mill

In the separate grinding process of cement composed of roller press+ball mill and vertical mill, the roller press+ball mill combined grinding (or semi final grinding) system grinds clinker and gypsum, while the vertical mill system grinds slag. Its characteristic is that the two systems are relatively independent. The grinding system of roller press and ball mill can not only produce clinker powder, but also directly produce finished cement. When producing cement, clinker, gypsum, and mixed materials are batched through the blending warehouse and then enter the grinding system for grinding. Cement products can be directly transported to the cement product warehouse through the conveying system.

Process characteristics

The cement grinding process composed of a roller press, ball mill, and vertical mill integrates two mature domestic process systems, namely cement grinding and slag grinding.

Ball mill grinding of slag has the characteristics of simple production process, energy-saving, and good adaptability to slag grinding moisture. A hot air furnace is installed in the grinding system to provide hot air for drying slag during the grinding process, without the need for separate offline drying equipment, resulting in good material drying effect. During the operation of the ball mill, a water spraying device was designed to stabilize the material layer. Grinding 8% to 15% wet slag with a ball mill can reduce the amount of water sprayed during the grinding process. If the material layer can be stable during operation, it can reduce production costs without the need for water spraying.

Process flow for preparing cement

There are two common cement preparation processes: double bottom preparation and single bottom preparation. The production process of preparing cement with double silo bottom is to store clinker powder and slag powder separately in the clinker powder silo and slag powder silo. Under these two semi-finished product silos, feeding metering equipment and mixing equipment are installed, measured according to the requirements of the cement variety, and then mixed by a mixer. The produced finished products are transported to the cement product silo through a conveying system.

Process characteristics

Both the double warehouse bottom preparation process and the single warehouse bottom preparation process can achieve cement preparation production, meeting the quality index requirements of different cement varieties. The preparation process of double silo bottom can enable the separately ground clinker powder and slag powder to be stored separately, measured and prepared under the warehouse, without being affected by the production of the previous grinding process. As long as there are materials in the warehouse, cement can be produced. Fast variety conversion, low conversion cost, and beneficial for production organization.

The above is the relevant information about the cement grinding process form and grinding equipment. For specific equipment configuration, please contact Jinqiang Technical Manager to provide a plan.

Cement grinding process and equipment