High capacity clinker coolers

Over the years the average size of new cement lines have continuously increased. Since the late 1990?s large clinker kilns with a capacity of 10,000 tonnes per day and more have been built by the several kiln manufacturers. IKN the leading supplier gives the latest picture.

The first of high capacity kilns were built in Thailand, Taiwan and China. Similar large kilns followed in the Middle East, mainly supplied by Chinese OEM?s. Now these high capacity kilns are being built and operated in India, too.

The main reason for these large capacities is the lower initial capital cost and lower operating cost per ton of clinker produced.

India has seen few contracts for new lines until last year. Some highlights were the 2 x 10,000 t/d plants for Ultra tech cement Ltd and the new line of Holcim at Jamul with a capacity of 9,000 t/d. UTCL plants are commissioned three years ago and presently these lines are operated upto 11,800 t/d.

This article will show how IKN contributed to the success of these lines, first by improving the existing large lines and later by supplying a large number of clinker coolers with capacities of 10,000 tpd and more.

Design of large IKN clinker coolers
The main design challenge for large clinker coolers is the ability to evenly distribute the clinker received from the kiln over a much wider cooler with a width of up to 7.2 m. First generation clinker coolers of capacity 10,000 tpd were designed with a width of 4.8 m. Based on the operation of the 9,100 tons per day IKN cooler at Sungshin Cement in Korea, IKN was confident that their fixed inlet called Klinker Inlet Distribution System (KIDS) was able to spread the clinker evenly to a width of 7.2 m and used this design as the standard for all further large coolers. This proved to be a good choice as the reliable operation of the coolers continues over many years. Fig. 1 shows an IKN KIDS in operation.

Thus, it is worth to emphasize that the development of the IKN KIDS fixed Inlet was one of the major factors that allowed the design of large and also comparably wide clinker coolers (Fig. 2). Without a fixed inlet, cooler design would have had to stay with narrow and very long coolers.

The second challenge in the design of large clinker coolers is the observation that clinker from these large kilns seems to be finer than clinker from smaller kilns. Additionally Indian plants are often operated with 100 per cent petcoke as fuel. This is more challenging for the clinker cooler than well granulated clinker. The ideal clinker bed thickness for uniform aeration of fine clinker is lower, and the cooler has to be able to operate between 450 and 550 mm of clinker bed. Compared to other cooler designs the IKN Pendulum Cooler is much more flexible and can work with almost any height of clinker bed and can therefore always operate with the most efficient parameters and the highest recuperation efficiency.

Design details of large IKN clinker coolers Linear Pendulum System
The Linear Pendulum System LPS lends itself well to the large width of these coolers: the cooler width is divided in two and each section has two LPS supports (Fig. 3). This design allows to drive the grate using only two hydraulic cylinders, which are located outside of the cooler, always within sight and continuously accessible for monitoring and maintenance.

All other components inside the cooler housing like the LPS are maintenance free, no bearings and do not require lubrication.

Coanda Wing Aeration
The slots inside the IKN grate plates are designed to use the so-called Coanda Effect to evenly distribute the air across the surface of the grate before it enters the clinker bed. This ensures best cooling of the grate itself and distributes the air evenly through the clinker bed. An in-depth study by using Computational Fluid Dynamic (CFD) showed that it was possible to further improve the velocity profiles in the slots of the grate plates. Based on this, IKN has modified the design of the blades and calls them now GC?Coanda Wings? as their profile is very similar to an airplane wing. The new grate plate shows a more direct airflow together with a uniform high slot velocity evenly distributed between all slots of the grate plate. The new design has been implemented in all new coolers and successfully operates now for more than three years.

Process results of large IKN coolers

The following table gives an overview of the main process data of the Rawan Plant of Ultratech Cement Ltd which was recorded recently.

Even after three years after the commissioning the performance of the cooler did not deteriorate

The three coolers in Tonglin and Wuhu in China operate with a mid-crusher after two thirds of the cooler. They supply additional heat from the mid-air tap to a Waste Heat Recovery System delivering additional power to the plant. In addition to this, it is also possible to recirculate the hot vent gases from stack to the selected cooling chambers to further improve the heat in mid-air.

IKN has the lowest operating cost per ton of clinker produced
Large clinker lines have a lower operating cost compared to smaller lines. The IKN clinker cooler will contribute to this by:

• Very high efficiency figures
• The ability to cope with fine clinker
• The lowest possible electricity kWh/t cost up to 40% lower than walking floor coolers
• Minimizing the maintenance cost of grate surface replacement parts by having a long wear life
• A very high mechanical availability and reliability, in many cases 100%, resulting in no kiln stops caused by the IKN cooler

A comparison between several coolers clearly demonstrated that the IKN Pendulum Cooler operates with the lowest operating cost as compared to all other cooler technologies.

Conclusions
Since the founding of IKN 30 years ago, IKN has become the no. 1 clinker cooler supplier for clinker coolers of capacities with more than 10,000 tpd. In total over 600 installations including coolers from 650 to 13,000 tpd worldwide provide a solid reference base. This success for a small company like IKN with about 150 employees is simply the result of better technology.

All internal and critical components of IKN cooler are manufactured 100% in Europe. IKN engineers are dedicated to continually improve the IKN cooler. The repeat orders of our customers is the result of the success of IKN cooler projects in every aspect.