Choosing A Cement Cooler: Rotary Coolers VS Grate Coolers

Clinker cooling is one of the important processes in cement production. Improving the cooling effect is not only beneficial to improve the quality and grindability of clinker, reduce the power consumption of the cement mill, but also can reduce the clinker temperature, recover the waste heat, and create favorable conditions for subsequent cement handling, storage, or transportation. At present, there are varies types of coolers available in the market, such as rotary cooler, grate cooler and so on. Each cooler type offers distinct advantages and disadvantages that may offer better performance in a given setting. The many factors to consider when selecting a cement cooler are summarized here.

Considerations When Selecting A Cement Cooler

In order to make the clinker cooler selecting more easy and efficient possible, factors such as thermal efficiency, clinker temperature, energy consumption, total investment, operational reliability, and environmental protection will help to determine which cooler is most appropriate.

Thermal efficiency

The thermal efficiency of a cement cooler refers to the percentage of the total heat recovered from the high-temperature clinker and the physical heat of the clinker. The higher the thermal efficiency, the more heat is recovered, which can be used to preheat the combustion air in cement kiln, saving energy and fuel cost. Therefore, when selecting a cooler, we should choose a type with higher thermal efficiency.

thermal efficiency
                                                                               Thermal Efficiency Formulas

QR.I: The total heat recovered from the high-temperature clinker and then be transferred to the cement clinker calcination system.

Qo: Physical heat of high-temperature clinker (kJ/kg).

Qloss.s: Total heat loss of a cooler (kJ/kg).

Qair: Heat is taken away by exhaust gas (kJ/kg).

Qm: Heat is taken away by discharged clinker (kJ/kg).

Qdis.l: Heat loss by radiation.

Qsec.a: The physical heat of the secondary air (kJ/kg). 

Qtec.a: The physical heat of the tertiary air (kJ/kg). 

The temperature of cooled clinker

The temperature of the cooled clinker can intuitively reflect the performance of a cement cooler, so it is an important index when selecting a cooler machine. Generally, the temperature of the cooled clinker is usually between 70-300 ℃.

Energy consumption

Energy consumption refers to the power consumption of cement cooler in daily operation. It will directly affect your production costs.

Operational reliability

Operational reliability refers to the daily running of the cooler. That is, whether the machine runs smoothly, the operation is simple, the maintenance is convenient, and the service life is long.

Total investment

The total investment includes not only the cost in the cement cooler but also some supporting equipment required by it, such as dust collector, conveying equipment, etc. Besides, we should also consider civil construction costs. Therefore, when we select a cooler, we should choose models with simple structure and few auxiliary types of equipment.

Environmental protection 

The cement industry is a highly polluting industry. We need to avoid noise and dust pollution in the production process. The cement cooler with low noise and small dust pollution is always the best choice.

Rotary Coolers VS Grate Coolers

Rotary cooler and grate cooler are two hot-sale clinker coolers in the market. They all have the function of cooling high-temperature clinker but differ greatly in structure, investment, cooling efficiency, etc.

Rotary cooler

The rotary cooler is the earliest used clinker cooler. It has a similar appearance with the rotary kiln, and the interior is equipped with refractory lining and flights. Clinker enters from one end and is lifted and scattered by flights. At the same time, the cold air enters from the other end and contacts with the clinker countercurrent for heat exchange. The rotary cooler is generally arranged under the rotary kiln, with a diameter of 2-5m and a length of 20-50m.

Grate cooler

Grate cooler is a quench type cooler. After clinkers enter from one end, they are pushed by movable grate plates and fixed grate plates to form a certain thickness of material layer on the grate bed. The cold air under the grate bed blows vertically through the hole on the grate plates to exchange heat with the clinker. The grate cooler is usually set behind the rotary kiln, and the thickness of material layer is 600-800mm.


Thermal efficiency

The thermal efficiency of the rotary cooler can reach 55-75% in dry cement production and 78% in wet cement production. But its heat loss is large, and the secondary air temperature is about 400-750℃, which is not suitable for the large cement kilns. The thermal efficiency of the grate cooler is 70%-75% and the temperature of secondary air is high, so it is a good choice for large scale cement production.

The temperature of cooled clinker

Since grate cooler is a type of quench cooler, the clinker can be treated by cooled air as soon as entering the machine. This cooling process is efficient and sufficient so the temperature of cooled clinker can reach about 100 ℃. While the rotary cooler adopts a counter-current air-flow design, the temperature of the cooled clinker is usually between 100℃ to 300 ℃.

Energy consumption

The rotary cooler has an independent drive system, while, the power consumption of grate cooler is not only used to push grate bed but also used for many blowers, conveyor and other auxiliary equipment, so the power consumption is large.

Operational reliability

The rotary cooler has a simple structure, steady running, and easy operation. Besides, the inner space of the machine body is large so the daily maintenance is convenient.

The grate cooler has a lot of parts and heavy maintenance workload. In addition, the blower and other auxiliary equipment make the management more complicated.

Total investment

Compared with the rotary cooler, grate cooler needs to buy conveyor, crusher, noise reduction, and dust removal equipment, and its power consumption is high, so the overall investment is large.

Environmental protection 

There is no dust pollution in the rotary cooler, but the exhaust gas from the grate cooler must be treated by dust collection, which increases the cost of investment and maintenance. As for noise pollution, after testing, the noise intensity is 86-97 decibels one meter away from the cylinder of rotary cooler, which has little impact on the environment, while, the noise of grate cooler mainly comes from air fans below the grate bed.

While the choice between a rotary cooler and a grate cooler may seem complex, ultimately, it comes down to, total investment, operational considerations and production capacity.

AGICO is a professional cement equipment manufacturing company. We offer quality rotary coolers, grate coolers, and many other cement manufacturing machines. If you are interested, please feel free to contact us!