Summary of advantages of cement separate grinding process Henan Hongxing

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Summary of advantages of cement separate grinding process

At present, in the recycling of slag, cement enterprises usually use slag as mixed material and add it together with clinker and other components in proportion Ball mill The mixture grinding is carried out. Due to the great difference of grindability between different materials, especially the poor grindability of slag in cement mixed grinding process is very obvious, which directly affects the per hour output and power consumption of the grinding system, and increases the production cost. With the continuous progress of cement grinding technology, separate grinding preparation is adopted Production technology of cement It is born of application.

 Cement grinding equipment ball mill

1、 Concept of separately grinding cement

According to the difference of grindability between cement clinker and admixture, different materials are grinded into cement components with different particle distribution. According to the close packing theory and the principle of giving full play to the strength of clinker and the activity and filling ability of admixture, the types and fineness of each component of cement are reasonably matched The high performance of cement can effectively improve the water requirement of cement and the adaptability of admixtures while maintaining or even improving the strength of cement.

2、 Advantages of cement separate grinding process

1. Reasonable particle size distribution

The strength of cement is not only related to its chemical composition and mineral composition, but also to its particle size and distribution composition. The strength of cement will be different even if the specific surface area is the same by using different grinding process and powder selection methods. The reason is that the particle size distribution is different. The influence of cement particle gradation on the performance has been analyzed and studied for a long time at home and abroad, and the basic conclusion has been obtained. For high-grade ordinary portland cement, the particle gradation of cement performance is 3 μ m ~ 32 μ m, the total particle size should be more than 65%, the fine particles less than 3 μ m should not be more than 10%, and the less particles > 65 μ m and < 1 μ m, the better, no, so as to exert the strength of cement In the case that the grindability of different components in cement production is very different, the particle distribution of clinker, admixture and other components in cement is needed to achieve the utilization of clinker activity and the full exploitation of the activity potential of admixture. Separate grinding should be the choice. The slag and clinker can be grinded separately with different specific surface area control by adopting the cement production process of separate grinding, which can make the slag grinding finer. In this way, on the one hand, the reactivity of slag can be improved; on the other hand, the particle distribution of cement can be improved by grinding slag, and the filling effect of fine-grained slag in cement paste can be increased, and the original packing density of cement particles can be increased The strength of clinker can be fully utilized by particle distribution, and the excellent potential hydraulic activity of slag can be brought into full play, and the cement strength can be significantly improved.

 

2. Increase the amount of admixture

Slag has a high potential activity. If the slag is ground to fineness, the addition amount of slag can be increased and the consumption of clinker can be reduced. But in order to give full play to the potential activity of slag, we need to rely on physical action to grind the slag to the fineness. When mixed grinding process is adopted, selective grinding is inevitable due to poor grindability of slag compared with clinker, resulting in uneven particle distribution of two components in the finished product. For example, when the specific surface area of cement is controlled at 350 m2 / kg, the slag in cement can not be fully grinded, the average particle size is too large, and the potential activity of the unrefined low activity slag can not be fully exerted, which limits the cement Red Star slag With the increase of the content of clinker, the consumption of clinker increases. The specific surface area, activity and strength of slag are increased by grinding slag to fineness. This kind of high activity slag powder and clinker powder are used to produce cement products. The activity of slag can be brought into full play. On the premise of ensuring the product quality index, the addition amount of slag powder can be increased, the clinker consumption can be reduced and the economic benefits of enterprises can be increased.

3. Reduce power consumption of grinding system

When using the mixed grinding process, in the case of the same specific surface area, due to the difference of grindability between clinker and slag, it is easy to produce grindable materials that are over grinded and hard to grind materials are not finely ground. The slag particle size after mixed grinding will be coarser than that of clinker. When the specific surface area of cement reaches 350 m2 / kg, the specific surface area of slag is only 230-280 m2 / kg; if the activity of slag is fully exerted To achieve the desired fineness (the specific surface area needs to reach 400 ~ 480 m2 / kg), it will also cause the over grinding of clinker, which not only makes the cement performance worse, but also directly affects the per hour output of the grinding system, making the power consumption of the grinding process increase and the cost increases. By grinding clinker and slag separately, the grinding fineness of clinker can be easily controlled and improved due to the reduction of difficult grinding components. The influence of refractory slag grinding characteristics on grinding process is reduced, so as to improve grinding efficiency and reduce grinding power consumption.

4. Improving the later strength of cement

According to the activity test of slag powder, the early strength of slag powder is lower, but the later strength increase rate is faster, which is the general rule of strength development of cement with slag. With the increase of the specific surface area, the activity index (strength ratio) increased significantly. When the specific surface area of slag powder reaches 400 m2 / kg, the 28d activity index reaches 95%, which is basically equivalent to that of cement; when the specific surface area of slag powder reaches or exceeds 420 m2 / kg, the activity is higher than that of the general specific surface area of cement clinker (350 m2 / kg). Therefore, the fine grinding of slag powder is more conducive to the growth of strength than that of clinker powder. When the cement grinding to a certain fineness, the slag powder is added to improve the strength The strength of cement will exceed that of pure Portland cement, which creates conditions for enterprises to produce high strength cement.

5. Flexible organization of multi variety production

The cost of cement variety conversion is relatively low when cement is prepared by grinding separately. With the permission of cement storage, it can flexibly organize the production of various kinds of cement, and change the process quickly and conveniently. It can not only produce ordinary cement, but also meet the special needs of customers. For example, according to the characteristics that the setting time of cement is prolonged after the addition of slag powder is increased, especially when the dosage is more than 40%, the retarder can be used to produce retarded cement for road construction or other projects with special requirements for setting time. According to the experimental study, with the increase of the content of Red Star slag powder, when the content is more than 30%, the hydration heat of cement is obviously reduced; when the content reaches 70%, the hydration heat is only 59% of that of Portland cement, which can meet the production requirements of low heat slag cement.

6. Improving the performance of cement

The size of clinker particles in cement is directly related to the hydration and hardening process. The hydration rate and degree of clinker particles with different particle sizes vary greatly. In the cement products produced by mixed grinding process, due to the large number of clinker fine particles less than 3 μ m, a large number of clinker fine particles will be hydrated in a short time, resulting in a series of disadvantages, such as the increase of early hydration heat, the increase of water demand, and the decrease of water reducer compatibility, which have a certain impact on the performance of cement. After the slag is ground to a certain fineness (specific surface area ≥ 400 m2 / kg), the crystal structure of glass body is destroyed and the activity of slag is brought into full play. When these active components are hydrated, under the excitation of alkaline solution, they will further generate hydrated calcium silicate and other hydraulic materials. After being prepared into cement, it is not only conducive to the improvement of the later strength of cement, but also can improve the early and late strength, impermeability and frost resistance of concrete, and improve the performance of concrete. The slag powder grinded separately can also be used to prepare high-performance concrete, adjust the hydration process of cement at the initial stage, and improve the workability, pumpability, compactness and durability of concrete.

In recent years, the cement grinding process has been fully integrated into the emerging market. Red Star factory is the R & D manufacturer of separate grinding process, and produces ball mill, ball mill, ball mill, etc Rotary kiln dryer Welcome customers from all over the world to visit and purchase machines.

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