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CEMENT MANUFACTURING TECHNOLOGY: STORAGE AND PRE-BLENDING

We were discussing “Cements and its types” and " Raw materials for manufacturing of cements” and “Material preparation technology in cement manufacturing” in our previous posts. We have also see the concept of cement manufacturing process and its selection in our recent post.

Today we are going to start here one very important topic i.e. process technology of cement manufacturing: Storage and pre-blending. We will understand the various terminologies and engineering concepts used in cement technology with the help of this category.

Further we will go for discussion of properties of burning technology, firing technology, clinker cooling and grinding, cement packing and dispatch, pollution control and much more facts about cement technology in our next post in this category of cement technology.

Let us see here the process technology of cement manufacturing

Process technology of cement manufacturing: Storage and pre-blending

Buffer stores are required between the crushing and grinding plants because of the following reasons:
Receipt of the raw materials from the mines is not continuous as the mines are operated in shifts. The grinding plants, on the other hand, are operated continuously as far as possible.

To provide better homogeneity in raw materials before feeding them to the grinding plants due to possible variations in properties e.g. chemical, physical and mineralogical, depending on the nature of deposits and the method of exploration.

There are broadly two types of stores:

1.      Homogenizing stores
2.      Buffer stores

Homogenizing Stores

These are rather expensive, especially if they are covered. The two types of stockpiles most widely used are as mentioned here.

1.      Longitudinal stockpile
2.      Circular stockpile

The quality of the blending bed depends upon the method of stockpiling. Reclaiming may be done using a Lateral scraper or in a transverse direction using a bridge type re-claimer fitted with a harrow.
There are two methods usually used for stockpiling are as mentioned here

1.      Chevron method (Roof method)
2.      Windrow method (Line method)

Blending effect by either method is as high as 1: 10. However, the Chevron method is cheaper. The stockpiling of horizontal beds by Chevron method is performed by

1.      A belt conveyor with traveling tripper
2.      A travelling stacker with a rigid boom

The stockpiling of a circular blending bed is performed by a belt conveyor which is swivel mounted in the beds centre- point.

The blending effect for either system is 1: 10. However, in the longitudinal system, the materials at the end cone areas of the stockpile are less homogenized.

Simultaneous operation i.e. stacking and reclaiming from the same pile is possible in circular stockpile but not in longitudinal type.

The cost of installation is relatively high for longitudinal stockpile (higher if it is covered) whereas covered construction is cheaper for circular stockpile.
The space requirement for a fixed capacity is higher for a longitudinal stockpile as compared to a circular one.

Expansion of storage capacity in future is possible In a longitudinal stockpile but not in a circular stockpile. 

Quality adjustment in the complete pile due to chemical variations in raw materials is possible in longitudinal stockpile but not in circular.

Non - Homogenizing Stores

Buffer stores e.g. the portal scraper type, give o much lower investment cost and is also suited for sticky material. Additives and admixtures are stored in this type of stores.

Do you have any suggestions? Please write in comment box.

We will see other topic i.e. “Process technology of cement manufacturing: Raw grinding plant” in our next post in the category of Steel and cement technology. 

I am very thankful to Mr. Subrata Bhaumik, Independent cement consultant, for providing such beautiful information and contents about cement technology. 

Mr. Subrata Bhaumik has more than 50 (Fifty) Years (1965 - 2016) of Experience in Cement and other related Industry covering more than 100 assignments in cement plants with capacities ranging from 100 tpd to 10,000 tpd in India and abroad involving visit to 25 countries overseas in connection with work.

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