The pre-homogenization technology used in the design of cement plants is to use the scientific stacking and reclaiming technology to realize the initial homogenization of raw materials in the process of depositing and taking raw materials, so that the raw material storage yard has the functions of storage and homogenization.
The basic principle of raw material pre-homogenization is that when the materials are stacked, the incoming raw materials are continuously stacked in a certain manner into as many parallel layers, upper and lower overlaps and the same thickness. When taking the material, in the direction perpendicular to the layer of the material, all the layers are cut as much as possible, and cut in order, until the end is taken, that is, “tiling straight”.
The storage period of various materials should be determined according to the scale of the plant, material source, material properties, transportation mode, storage type, factory control level, market factors, etc., and should meet the requirements of the following table.
Various material storage period (d)
| Serial number | Material name | Material storage period | |
| Wet material | Dry material | ||
| 1 | Calcareous raw material | 3~7 | — |
| 2 | Silicon-aluminum raw material | 5~30 | — |
| 3 | Iron raw material | 10~30 | — |
| 4 | Coal | 7~30 | — |
| 5 | Raw material | — | 1~3 |
| 6 | Clinker | — | 5~20 |
| 7 | Plaster | 7~30 | — |
| 8 | Mixed material | 7~30 | — |
| 9 | cement | — | 3~14 |
Note:
1. The material storage period is calculated based on the kiln mouth output as the basis;
2. If the calcareous raw materials and the silico-alumina raw materials are purchased, the upper limit may be taken; the storage period of the materials;
3. The clinker storage period of clinker shipment and cement powder grinding may be appropriately relaxed;
4. The mixed materials shall be determined according to their source, distance and variety;
5. The storage period of cement should be considered in conjunction with the storage period of clinker. Combined with market demand, transportation conditions are determined;
6. Material storage period refers to the total storage period in each storage mode such as stacking shed, combined storage, pre-homogenized storage yard, and round storage.
First. In any of the following cases, the raw material should be pre-homogenized:
1. The deposit conditions are complex, and the fluctuation of ore grade or major harmful elements is relatively large;
2. There are low-grade raw materials such as interlayers, coverings and crackers that can be used together in the deposit.
Second. In any of the following cases, the pre-homogenization yard should be set for the raw coal:
1. The quality of raw coal varies greatly, or the quality of pulverized coal into the kiln cannot guarantee the fluctuation range of two adjacent tests;
2. The original coal comes from many places, or the coal types are also various;
3. Poor coal quality, does not meet the requirements of this specification, or the coal blending method is required for adjusting the ratio of sulfur to alkali.
Third, the pre-homogenization yard should be designed according to the nature of raw materials and fuels, and should meet the requirements of factory scale, storage mode, automation level, environmental protection and technical requirements.
Fourth, the design of raw materials and fuel pre-homogenization yards should meet the following requirements:
1. The number of layers should be 400 ~ 500 layers, the homogenization coefficient can be 3 ~ 7, should be determined according to the fluctuation of the raw materials and fuel components entering the yard;
2. The choice of yard form should be determined according to the overall layout of the plant, plant topography, expansion prospects, material performance, quality fluctuations and economic factors;
3. The stacking method can adopt the stacking method such as herringbone and conical, and the type of stacker should be selected according to the yard type;
4. The method of reclaiming can adopt end-face reclaiming or side reclaiming;
5. Mixing pre-homogenization yards, pre-dosing should be carried out before pre-mixing;
6. When two or more types of coal are used, they should be combined into the pre-homogenization yard;
7. The material discharge detector shall be provided at the discharge end of the stacker, and the height of the discharge point shall be automatically adjusted according to the height of the pile;
8. Ventilation facilities should be provided in the trench of the reclaimer.
