Conversion to High-Efficiency Grate Coolers

The grate cooler is integral to heat recovery from the clinker, so grate coolers that operate with higher efficiencies will lead to less wasted heat and reduce fuel usage elsewhere in the process. The grate coolers offer two main advantages.  First, they can have a large capacity allowing large kiln capacities.  Second, they offer efficient heat recovery by lowering the emperature of the clinker leaving the cooler to as low as 83°C, instead of 120 to 200°C, which is expected from planetary coolers. 

Modern grate coolers have a higher degree of heat recovery than older variants, increasing heat recovery efficiency to 65% or higher, while reducing fluctuations in recuperation efficiency (i.e. increasing productivity of the kiln). Both planetary and travelling grate coolers can be replaced with reciprocating grate coolers or coolers with static grates and innovative moving mechanisms (the so called fourth generation coolers). Such coolers typically have minimal leakage, a modular structure, high heat recovery and running rate, a compact structure, and longer-life grate plates (MIIT, 2012. p21). As planetary coolers do not allow for tertiary heat recovery, which would be necessary if a pre-calciner is used, conversion to grate cooler may be more economical for units that have or will have a precalciner installed as well.  The cost of the reciprocating cooler may be prohibitive for facilities with a capacity less than 550 tons/day.

Chinese flag In 2012, reciprocating grate cooling technology had a penetration rate of 10%. However, the technology is widely used in the cooling process of new cement plants using dry processes as well as in upgrading existing coolers. The penetration rate is expected to reach 25% during the twelfth five year development period (MIIT, 2012. p.21-22). The penetration rate of this type of coolers is expected to reach 42 to 45% by 2015 (NDRC, 2009. p43),  

Development Status Products
clinker, Cement

Conversion to High-Efficiency Grate CoolersCosts & Benefits

Parent Process: Clinker Cooling
Energy Savings Potential

Fuel consumption in the kiln can be reduced by as much as 8%, or by 0.27 GJ/t-clinker, but electricity consumption will increase by around 3 kWh/t-clinker. 

Chinese flag Compared with the third generation grate cooler, fourth generation coolers can help reduce heat consumption for clinker making by 10% to 18%, and power consumption of the cooler by 20% (NDRC, 2009. p.43)

Chinese flag According to MIIT, this technology consumes 4 kWh of electricity per ton of clinker processed, and can achieve heat recovery rates up to 74% – enabling an improvement of 4 to 6%.

Chinese flag For a 5000 tpd plant, high efficiency grate coolers are reported to have the potential to reduce annual coal consumption by 4000 to 5000 tons (MIIT, 2012. p.22).

Chinese flag In a 3000 tpd Chinese plant, installation of high efficiency grate cooler reportedly reduced annual energy consumption by 99.35 TJ (3390 tce) (MIIT, 2012, p.22)

Chinese flag In a 5500 tpd Chinese plant, installation of high efficiency grate cooler reportedly reduced annual energy consumption by 156.2 TJ (5330 tce) (MIIT, 2012, p.22)

CO2 Emission Reduction Potential

The cost of a cooler conversion is estimated to be between US $.044 and $5.5/annual tonne clinker capacity, depending on the degree of reconstruction needed. Annual operation costs of the cooler can increase by US $0.11/t clinker. Estimated payback period: 1-2 years (LBNL, 2008).

The cost for the conversion from a planetary cooler to an efficient reciprocating grate cooler of newest generation with a capacity of 6,000 tons per day is estimated to €15 - 20 million. These costs can vary widely due to the site specific conditions (new exhaust air fan and cooler filter, foundations and other construction cost, shortening of the kiln). The retrofit of an old grate cooler demands an investment of €1 – 3 million. (ECRA, 2009)

Chinese flag Fourth generation coolers are reported to have 20% lower installation costs, and 70 to 80% less maintenance costs (NDRC, 2009. p.43)

Chinese flag For a 5000 tpd plant, the installation and annual operational costs for a high-efficiency grate cooler are reported to be 20 million RMB and 5 million RMB, respectively. Resulting payback time is reported to be 3.5 years(MIIT, 2012, p.22)

Chinese flag In a 3000 tpd Chinese plant, high efficiency grate cooler was installed at a cost of 8 million RMB and over a period of 3 months. The annual cost savings amounted to 2.37 million RMB, resulting in a payback time of 3.5 years (MIIT, 2012, p.22)

Chinese flag In a 5500 tpd Chinese plant, the technology was installed at a cost of 10 million RMB and over a period of 3 months. The annual cost savings amounted to 3.7 million RMB, resulting in a payback time of 3 years. MIIT, 2012, p.22)

Conversion to High-Efficiency Grate Coolers Publications

Development of State of the Art Techniques in Cement Manufacturing: Trying to Look Ahead

The report represents the independent research efforts of the European Cement Research Academy (ECRA) to identify, describe and evaluate technologies which may contribute to increase energy efficiency and to reduce greenhouse gas emissions from global cement production today as well as in the medium and long-term future. 

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Energy Efficiency Improvement Opportunities for the Cement Industry

The U.S. Environmental Protection Agency’s (EPA) energy guide, Energy Efficiency Improvement and Cost Saving Opportunities for Cement Making, discusses energy efficiency practices and technologies that can be implemented in cement manufacturing plants. This ENERGY STAR guide provides current real world examples of cement plants saving energy and reducing cost and carbon dioxide emissions.

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Advanced and Applicable Technology Guide for Energy Saving and Emission Reduction in Building Materials Industry (first batch)

Published jointly by the Chinese Ministry of Industry and Information Technology, Ministry of Science and Technology, and Ministry of Finance, this guide describes information on currently available as well as developing technologies that can help reduce energy consumption and emissions in building materials industries. The guide aims to inform decision makers involved with designing new plants and/or implementing energy efficiency and emission reduction projects in existing plants.

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Conversion to High-Efficiency Grate Coolers Reference Documents

Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Portland Cement Industry


This document provides information on control techniques and measures that are available to mitigate greenhouse gas (GHG) emissions from the cement manufacturing sector. It includes a useful table where mitigation measures are summarized, along with their energy and economic saving potentials and implementation costs.  

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