Cement manufacturing processing steps

In the portland cement manufacturing process, three steps occur. First, raw materials are crushed and mixed. The raw materials are powdered limestone, alumina, iron, and silica. Second, the raw materials are fed to an inclined rotary kiln in which they are heated to at least 2700 F. A rock-like substance called clinker is formed, which exits the kiln and is cooled. Third, the cooled clinker is finely crushed, and about 5 percent gypsum is added to produce finished cement. Details of the process are explained below. 

Figure 1-4. Pictorial flow diagram establishes key processing steps Cement manufacture. By permission, E-M Synchronizer, Electric Machinery Mfg. Co.

The manufacturing process begins with the composition of a specific Cemented carbide powder mixture - tailored for the applicatiOTi. Scheelite or wolframite are the tungsten-cfuitaining minerals. Ammonium-Para Tungstate (APT) is the starting raw material of the production. The first step is a wet process involving a sequence of stepwise dissolutions, precipitations, and separations (Fig. 9). 

As the last step in Portland cement manufacture, Portland clinker, in combination with limited amounts of gypsum and/or anhydrite, has to be ground to a fine powder. A ball mill is the standard equipment used for this purpose. It was reported recently (Goldstein, 1997) that the power consumption in the grinding process may be reduced if—in place of a single clinker—a blend of two clinkers is used, of which one has a higher and the other a lower lime saturation factor. 

This preheating can be achieved by indirect heat exchange between hot product gases. This is practised in the manufacture of cement clinker. The clinker is cooled in process air, which is thus preheated for the precalcination step. The next calculation example treats a simplified case of this type. 

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