In the design of the cement grinding system and the demonstration of the transformation plan, it is not only necessary to consider whether the cement ingredients are mainly made of slag and other materials with poor grindability, but also whether to use fly ash and power plant slag. Choose the appropriate process form and grinding equipment based on better raw materials for mixing materials, as well as the requirements for the production of ordinary Portland cement, composite Portland cement, slag cement and other cement varieties.

The common point of the different grinding processes is that the slag must be ground into slag powder, that is, the specific surface area is ≥380m2/kg, and the micropowder particles are 80%≤50μm, of which ≤10μm ultrafine powder accounts for about 30%~40%, so that the slag powder The activity of the cement can be fully exerted, the addition of slag powder can be increased, the performance of cement can be improved, the consumption of clinker can be reduced, and the goal of low carbon and environmental protection can be achieved.

Separate grinding process of ball mill

1. Ball mill separate grinding process

In the separate grinding system of the ball mill, the process flow can be a first-level open-circuit process of a high-fineness high-yield tube mill, or a first-level closed-circuit process of an ordinary ball mill plus a high-energy powder separator. One ball mill is used to grind the clinker and gypsum, and the other ball mill is used to grind the slag, and then sent to the clinker powder warehouse and the slag powder warehouse respectively, and the production is prepared according to the requirements of cement varieties. When the ball mill grinds the slag, the water content of the slag entering the mill must be controlled below 2.0%, so the slag should be dried by drying equipment before entering the mill.

2. Process characteristics

The separate grinding process of the ball mill is simple in production process and flexible in production organization. It can obtain higher slag grinding fineness, make the activity of slag powder fully play, and is conducive to the improvement of cement strength. The disadvantages are low output per hour and grinding power High consumption. Using the ball mill system to produce slag powder, under the same process and equipment conditions, the output is about 40%~50% lower than that of cement grinding. 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.

Roller press + ball mill separate grinding process

1. Roller press + ball mill separate grinding process

In recent years, the combined separate grinding process of roller press + ball mill has appeared. The combined separate grinding system of roller press + ball mill can realize the separate grinding of clinker powder and slag powder. When grinding the slag, the hot air stove is used to provide hot air, and the slag is dried on-line through the improved V-type separator, which simplifies the production process. The ball mill grinding system can adopt the first-level closed-circuit system of ordinary ball mills and the first-level open-circuit system of high-fineness and high-yield mills.

2. Process characteristics

The characteristics of the separate grinding process of roller press + ball mill are that it eliminates the edge effect of the roller press and meets the requirements of supersaturated feeding of the roller press. The working pressure can prolong the service life of the roller sleeve and improve the operation rate. According to the information, this process increases the output by more than 40% when grinding slag, and reduces the power consumption of grinding by 10% to 15% compared with the ordinary ball mill grinding process.

Separate grinding process composed of roller press + ball mill and vertical mill

1. Separate grinding process consisting of roller press + ball mill and vertical mill

In the separate grinding process of cement consisting of roller press + ball mill and vertical mill, the combined grinding (or semi-final grinding) system of roller press + ball mill grinds clinker and gypsum, and the vertical mill system grinds slag. The two systems are relatively independent. The roller press + ball mill grinding system can not only produce clinker powder, but also directly produce cement products. When producing cement, the clinker, gypsum and mixed materials are batched through the blending warehouse and then entered into the grinding system for grinding. The finished cement can be directly sent to the finished cement warehouse through the conveying system.

2. Process characteristics

The cement grinding process composed of roller press + ball mill and vertical mill integrates the two mature process systems of cement grinding and slag grinding in China.

Using a ball mill to grind slag has the characteristics of simple production process, energy saving, and good adaptability to the water content of slag entering the mill. Drying, grinding, and powder selection are all completed in the mill. A hot air stove is installed in the grinding system to provide hot air to dry the slag in the mill, without separate offline drying equipment, and the drying effect of the material is good. In order to stabilize the material layer during operation, the ball mill is designed with a water spray device. Using the ball mill to grind wet slag with a moisture content of 8% to 15% can reduce the amount of water spray during grinding. If the material layer can be stabilized in operation, it can be used without Spray water to reduce production cost.

Preparation of cement process

1. The process of preparing cement

The common technological process for preparing cement includes two production processes: double-bottom preparation and single-bottom preparation. The double-bottom cement production process is to store the clinker powder and slag powder obtained through separate grinding in the clinker powder storehouse and the slag powder storehouse respectively, and install feeding metering equipment and mixing equipment under the two semi-finished product storehouses , according to the requirements of the cement variety, after being measured, it enters the mixer for mixing, and the finished product is sent to the cement finished product warehouse through the conveying system.

2. Process characteristics

Both the double-bottom preparation process and the single-bottom preparation process can realize the production of compounded cement and meet the quality index requirements of different cement varieties. The double-bottom preparation process allows the separately ground clinker powder and slag powder to be stored separately for measurement and preparation under the warehouse, which is not affected by whether the previous grinding process is produced or not, as long as there are materials in the warehouse. For the production of compounded cement, the variety conversion is quick and the conversion costs less, which is beneficial to the production organization.