Grate coolers

However, it is doubtful that industrial clinkers can ever contain a good deal of glass, because even very good grate coolers cannot assure such rapid cooling, as in laboratory. 

Some coolers and dryers can be in a form of contactors such as the rotary kiln itself, although some are packed-bed contactors such as grate coolers. Rotary coolers can be either in-line or attached (Figure 1.8), the number of which is determined by a simple formula... 

Figure 10.6 Typical schematic of a cement kiln with preheater, precalciner, and grate cooler.

With regard to adaptation to the kiln system the grate cooler is more versatile than the other systems of clinker cooler. More particularly, it offers the best conditions for optimal extraction of hot air for precalcining kiln systems with separate tertiary air supply. 

For kiln systems with grate-type preheaters, in which the exit gases cannot be utilized for material drying purposes, there is practically no economical alternative to the grate cooler, because in such cases the exhaust air from the cooler can always be utilized. 

Fig. 3 Suitability of the coolers for different clinker gradings Grate cooler 1 —3, for grading "0" only if equipped with inter-...

Grate coolers and shaft coolers present the least problems in this respect, because the increase in fan capacity and size of housing necessitated by higher altitude has only a minor effect on the overall cost of the cooler. On the other hand, with the shaft cooler the attainment of suitably low final clinker temperatures becomes even more problematical at high altitudes, while in the case of grate coolers it becomes advisable under such circumstances to install a type comprising an intermediate breaker and a circulating air system. 

The actual capital expenditure associated with the various types of clinker cooler is liable to vary greatly from one case to another, especially if after-coolers and/or elaborate noise control measures have to be included. In every case where complete utilization of the exhaust air from the cooler is possible, the multiple-stage grate cooler with circulating air system will involve the lowest capital outlay. 

Wherever complete exhaust air utilization is possible, the grate cooler will always be the least expensive type in terms of purely mechanical engineering and ancillaries. In this respect the shaft cooler is also quite favourable, whereas in the case of the rotary cooler and planetary cooler, as also the grate cooler with high-efficiency dust collection system, the cost of mechanical and/or ancillary equipment is distinctly higher, though in this there is very little difference between these three last-mentioned types of cooler. 

In so far as these expenditure items are concerned, the planetary cooler is distinctly superior to the other types even though it requires a more powerful kiln drive and higher-capacity exit gas fan, while the shaft cooler and grate cooler are the most expensive types in this respect. 

Table 2 Operating cost relations for the grate cooler with exhaust air utilization...

Nearly all manufacturers of machinery for the cement industry include their own grate coolers in their product ranges. Hence it is not possible, within the present scope, to go beyond a description of the more commonly encountered types and forms of construction. 

In the main, a distinction is drawn between travelling grate coolers and reciprocating grate coolers. 

The main problems associated with the travelling grate cooler are those of achieving uniform distribution of the clinker across the width of the grate immediately after its discharge from the kiln. 

Fig. 9 Travelling grate cooler with rising grate (from Herchenbach, 1978) 3.3.1.2 Reciprocating grate coolers...

The example relates to a three-stage cooler, with intermediate size reduction, of the type built by the engineering firm of Claudius Peters. The principles it embodies are essentially applicable to ail other reciprocating grate coolers, including for... 

The measuring and control instrumentation for a shaft cooler is somewhat less elaborate than that for a grate cooler. The control duties to be performed are similar, however. The column of clinker in the cooler must be maintained at constant height irrespective of the rate at which clinker is discharged from the kiln. 

Separate dust coiiection systems are needed only for grate coolers in so far as there is a surplus of exhaust air and no after-cooling in a gravity cooler is employed. The exhaust air design conditions for dust collectors intended for operation with... 

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