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WHR in the cement industry – Part 4: Future Trends

World Cement,


All the evidence suggests that, in the future, WHR systems will become essential features of cement plants no matter where the units are built. Thus the medium to long-term prospects for WHR installations in the cement industry are good – largely because the worldwide costs of electric power will continue to be high and the limitations on CO2 emissions are likely to become more stringent. An exception might be in the USA, where plentiful supplies of low cost gas will provide a basis for stable electricity costs and the restrictions on harmful emissions may be less demanding than in other developed countries.

In addition to these economic and statutory requirements, the technologies available for recovery of waste heat that already have a good record of reliability and high availability will show further improvements and perhaps installed costs will decline somewhat. Furthermore, as cement plants become more efficient in the use of energy resources, the temperature of waste heat would be expected to decline so that technologies such as ORC and the Kalina Cycle, which can extract energy from low-grade heat more effectively than the Rankine Cycle, would be expected to win a larger share of the market. However, although some improvements in the individual systems can be expected, it is unlikely that any major changes will occur in the foreseeable future.

Some consideration has been given to the potential of a supercritical Organic Rankine Cycle (sORC) and theoretical studies with exhaust gas from IC engines have shown that some gain in efficiency could be achieved with this type of development. The enhanced efficiency arises because a supercritical fluid can be heated without evaporation, giving a better match with the heat source and more effective heat transfer. While there does not appear to be a commercial application of the sORC, the better efficiency and the relative simplicity of the system could provide an attractive option.

A new approach to power generation also using a supercritical fluid but in this case carbon dioxide (sCO2) is in the early stages of development but has some potential application in WHR systems and this could be an innovation in the industry.

Studies in connection with the next generation of nuclear reactor have confirmed that cycles based on sCO2 have excellent potential for application to nuclear heat sources in the temperature range 450 – 600°C. As further progress is made it may become feasible and economically attractive to use this type of cycle in WHR applications for cement plants. The recent award from Small Business Innovative Research (SBIR), an agency of the US Department of Defense, for a feasibility study of an sCO2 system based on a Brayton Cycle to recover waste heat from an MT30 gas turbine in shipboard applications is an indication of the wider interest in this type of system.

Written by Thomas B. Gibbons. This is an abridged version of the full article, which appeared in the August 2013 issue of World Cement. Subscribers can view the full article by logging in.

Read the article online at: https://www.worldcement.com/europe-cis/05082013/future_trends_waste_heat_recovery_cement_industry_80/


 

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