Homogenization of raw meal preparation

The preparation of raw meal is an important link in the new dry process, and the key is the homogenization of raw meal. For example: some manufacturers of raw materials fluctuations, and did not take pre measures, some manufacturers of raw mealsilo due to design or irregular operations are a serious shortage of capacity, some of the batching control system, resulting in ineffective management weighfeeders ingredient goal is difficult to control, and the emergence of very large fluctuations and so on. All the problems in the preparation of raw meal will seriously affect the composition of raw meal and the thermal system of kiln.

In order to stabilize the normal thermal system of cement kiln, high quality and high yield and uniformity of the new dry process cement rotary kiln feed ingredients must put forward strict requirements, the homogenizing should be throughout the whole process of the preparation of raw materials. Generally, 4 aspects of mining, mine collocation prehomogenization of raw material, raw material grinding process and the homogenization effect of raw mealsilo, each link of raw materials and raw materials will be further averaging [1], every aspect of the homogenization effect is not the same. Homogenization of raw materials and homogenization of raw materials warehouse is the main link of homogenization process. These two parts account for more than 80% of the work done in the homogenization work.

1.1 Homogenization system of  raw meal and its importance

With the development of new dry process cement plant technology, homogenization technology has been widely used. Homogenization technology and raw meal preparation have formed a pair of concepts. For the new dry process, it is necessary to mention the homogenization system of raw meal when it comes to raw meal preparation. It includes 3 aspects of technical and economic significance.

(1) it can enlarge raw material resources and utilize ore interlayer to improve the comprehensive utilization ratio of mine resources.

(2) we can make full use of the overburden or low grade stone, reduce the stripping, reduce the cost of mining, and extend the service life of the mine.

(3) ensure the homogeneity and quality of raw materials, raw materials and raw materials. In order to stabilize the thermal system and operation of cement kiln, it is easy to implement automatic control, so as to achieve the purpose of high quality, high yield, low consumption and high operation rate.

Raw materials prehomogenizing and storage:

in the preparation of raw materials has two functions, the system in a long period, the elimination of limestone into the plant component of the fluctuation; second, reduce raw material composition fluctuations, reduce the standard deviation of into the plant raw material. In preblending storage in a certain way, stacker reclaimer, discharging components to reach a certain uniformity, meet the control requirements of the ingredients of raw mill, the homogenization silo discharge composition fluctuation has the characteristics of short cycle, high frequency, low amplitude. The general part of the H is less than or equal to 10, the homogenizing effect of 30%-40%.

Preparation of raw material grinding control:

raw mill in preparation of raw materials are the main effect in the control and regulation of the ingredients, although it is to improve the uniformity of grinding material content of CaO, and did not play a large role, but it can guarantee the raw meal composition in certain period up to or close to the target value, and can improve the uniformity of SiO2, Al2O3, Fe2O3 and other ingredients. The homogenization effect of raw meal mill in the preparation of raw meal accounts for about 10%. Due to the delay and hysteresis in the batching control of raw meal mill and the influence of inertia and stability in the production adjustment, the fluctuation of the grinding composition of raw meal mill has the characteristics of medium period, medium frequency and low amplitude.

Raw meal homogenization and storage:

This is the last step in the preparation of raw materials, its role is to eliminate the fluctuation of the composition of raw meal, make the raw ingredients to kiln feed requirements, CaCO3 standard deviation reach + 0.2%. In order to ensure the stability of the kiln thermal system, the homogenization effect of this part accounts for about 30%-40% of the raw material preparation.

1.2 Effect of  raw meal preparation uniformity on clinker quality

The homogeneity of raw materials directly affects the quality of clinker. The following two aspects are discussed: the influence of fCaO and the strength of clinker. R and CaO will be a coefficient of variation of clinker kiln feed in fCaO corresponding to find corresponding relation, results show that the effect of R on fCaO is very direct, the bigger the R, the uniformity of raw material is poor, corresponding to each class in fCaO clinker comprehensive value is greater, the KH value for the two kinds of material high SM, high IM value, secondly, different values of KH to fCaO different influence. The greater the KH, the greater the sensitivity of fCaO to R.

The uniformity of raw material on clinker strength perspective, the uniformity of raw material is poor, the strength of clinker is lower, from the micro can think so: in the CaO rich region, generating a large number of A mine, with a certain amount of unreacted fCaO. In the SiO2 rich area, it can be observed in clusters of patches of B mine, the shape and size of crystals are not ideal development. The macro point of view, mainly for the material instability, sometimes cuangao material (KH material), sometimes resulting in lower material, kiln frequently regulated by coal or thermal annealing kiln system has been severely damaged, agglomeration is not normal and undersintering may exist at the same time, sandwich material, influence of sintering quality, the final effect of clinker strength.