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.
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 |
|---|---|
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Commercial
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clinker, Cement
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| 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.
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| CO2 Emission Reduction Potential | |
| Costs |
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)
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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.
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.
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.
Published by the National Development and Reform Commission of China, this directory provides information on 50 energy-efficient technologies applicable to 9 industries such as coal, electricity, iron and steel, nonferrous metals, petroleum and petrochemicals, chemicals, building materials, machinery, textile and others.
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.
