Cement and Energy

Encouraged by these results IKN developed a new generation of clinker coolers - the IKN pendulum cooler with Coanda nou les. (See Fig. I) Fig. 1. The complete IKN pendulum cooler system Even distribution of air increases the efficiency of clinker cooling. Other cooler suppliers concentrated on parameters, such as the inclination of the grate, type of plate, compartmentation , specific air load to improve the cooler performance; but none of these parameters was critical. The key parameter is the grate's resistance to the passage of air. The grate resistance controls the distribution of air into and within the clinker bed. The ratio of the resistance or the grate to the resistance of the clinker bed is important. for a 500 mm clinker bed and a cooling range of from 1400° to I00°C. How can fast cooling be achieved and what are the limits and restrictions? Because every cooler is al so a recuperator it must maintain the highest possible secondary and tertiary air temperatures. In order to minimise the heat consumption of the kiln the maximum amount of cooling air has to be passed through the clinker bed without disturbing it. To maintain the temperature prof·ile across the clinker bed, it is vital not to disturb the stratification of the clinker layers. Though this can be easily achieved by redu ~i.ng the amount of cooling air, the result is slower cooling and the consequences are sticky, clinker-creating clods on the bed surface, recooling of secondary air by the top layer, no quenching effect, and hot clinker at the cooler outlet. In the most effective coolers, cooling air passes evenly through the clinker bed without disturbing the layers. (See Fig.2) Furthermore, the resistance of the clinker bed docs not depend solely on its depth . It is also the result of the partial fluidi sation of the fines. Fig 2: Passage of air over cooler blade.s Clinker cooling with Coanda nozzles Efficient clinker cooling is always a race against time. Fast cooling. at a given bed depth shortens the retention time in the cooler and means that a smaller grate area can be used with a higher specific clinker load. Capital and maintenance costs can be reduced. In addition, fast cooli.ng or quenching in the recuperating zone gives better quality clinker with hi gh c3s ~onten t, low free lime and excellent grindability. At present, the standard IKN design produces 50t/m 2 d with a ret ~.:nti on time of less than 20 minutes Fig 3: A section of a conventional grate with vertical aeration. IKN claims that as a result of high air velocities and reverse air flows, the grate plate will suffer from excessive wear caused by ...-;.¥:;:~7='7~~~~,.?~4-r-- sand blasting effects. The heat shield is a hydraulically powered partition wall located at the neutral point of the cooler: wall raised (left) ·and closed (right). 5