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Waste Heat Recovery: ­ Technology and Opportunities in U.S

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Waste Heat Recovery: ­ Technology and Opportunities in U.S Intentionally Blank Page ii ­ Waste Heat Recovery: ­ Technology and Opportunities in U.S. Industry ­ Prepared by BCS, Incorporated March 2008 iii ­ Disclaimer This report was prepared as an account of work sponsored by an Agency of the United States Government. Neither the United States Government nor any Agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any Agency thereof. The views and opinions expressed by the authors herein do not necessarily state or reflect those of the United States Government or any Agency thereof. iv ­ Abstract ­ The U.S. industrial sector accounts for about one­third of the total energy consumed in the United States and is responsible for about one­third of fossil­fuel­related greenhouse gas emissions. It is estimated that somewhere between 20 to 50% of industrial energy input is lost as waste heat in the form of hot exhaust gases, cooling water, and heat lost from hot equipment surfaces and heated products. As the industrial sector continues efforts to improve its energy efficiency, recovering waste heat losses provides an attractive opportunity for an emission­free and less­costly energy resource. Numerous technologies and variations/combinations of technologies are commercially available for waste heat recovery. Many industrial facilities have upgraded or are improving their energy productivity by installing these technologies. However, heat recovery is not economical or even possible in many cases. This study was initiated in order to evaluate RD&D needs for improving waste heat recovery technologies. A bottom­up approach is used to evaluate waste heat quantity, quality, recovery practices, and technology barriers in some of the largest energy­consuming units in U.S. manufacturing. The results from this investigation serve as a basis for understanding the state of waste heat recovery and providing recommendations for RD&D to advance waste heat recovery technologies. Technology needs are identified in two broad areas: 1) extending the range of existing technologies to enhance their economic feasibility and recovery efficiency, and 2) exploring new methods for waste heat recovery, especially for unconventional waste heat sources. Acknowledgement We gratefully acknowledge the support of the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, Industrial Technologies Program (ITP). This work was carried out by BCS, Incorporated under contract with DOE. The final report presents information from many resources. The research and content was developed by Ilona Johnson and William T. Choate, Amber Davidson provided edits, and Borys Marizza provided the cover design. The authors would like to thank: Elwin L. Rooy, Rooy and Associates (aluminum): H. Wayne Hayden, President, MMPact Incorporated (aluminum); Michael Greenman, Executive Director, Glass Manufacturing Industrial Council (glass); Fred Rorick, President, Rorick Inc. (steel); and, William A. Obenchain, AISI Technical Manager (steel) for their time and input to our understanding of the industrial processes. v ­ TABLE of CONTENTS Index of Tables............................................................................................................................ viii Index of Figures............................................................................................................................ ix Executive Summary ....................................................................................................................... x 1.0 Introduction........................................................................................................................ 1 1.1 What is Waste Heat Recovery? ................................................................................................ 1 ­ 1.2 Need for This Study................................................................................................................... 3 ­ 1.3 Structure of This Report........................................................................................................... 4 ­ 2.0 Factors Affecting Waste Heat Recovery Feasibility ......................................................... 6 2.1 Heat Quantity............................................................................................................................. 6 ­ 2.2 Waste Heat Temperature/Quality............................................................................................ 6 ­ 2.2.1 Heat Exchanger Area Requirements......................................................................................................7 ­ 2.2.2 Maximum Efficiency for Power Generation: Carnot Efficiency ...........................................................9 ­ 2.2.3 Temperature and Material Selection....................................................................................................10 ­ 2.3 Waste Stream Composition .................................................................................................... 10 ­ 2.4 Minimum Allowable Temperature ........................................................................................ 11 ­ 2.5 Economies of Scale, Accessibility, and Other Factors.......................................................... 11 ­ 3.0 Waste Heat Recovery Options and Technologies ........................................................... 12 3.1 Heat Exchangers...................................................................................................................... 12 ­ 3.1.1 Recuperator..........................................................................................................................................12 ­ 3.1.2 Regenerator..........................................................................................................................................14 ­ 3.1.3 Passive Air Preheaters .........................................................................................................................15 ­ 3.1.4 Regenerative/Recuperative Burners.....................................................................................................16 ­ 3.1.5 Finned Tube Heat Exchangers/Economizers .......................................................................................16 ­ 3.1.6 Waste Heat Boilers ..............................................................................................................................17 ­ 3.2 Load Preheating....................................................................................................................... 17 ­ 3.3 Low­Temperature Energy Recovery Options and Technologies ........................................ 18 ­ 3.3.1 Challenges to Recovering Low­Temperature Waste Heat...................................................................19 ­ 3.3.2 Low­Temperature Heat Exchange .......................................................................................................19 ­ 3.4 Power Generation.................................................................................................................... 25 ­ 3.4.1 Generating Power via Mechanical Work.............................................................................................25 ­ 3.4.2 Direct Electrical Conversion Devices ..................................................................................................27 ­ 3.5 Summary of Heat Recovery Technologies............................................................................. 29 ­ 4.0 Evaluating Selected Applications for Waste Heat Opportunities and Practices ........... 33 4.1 Glass Manufacturing............................................................................................................... 34 ­ 4.2 Cement Manufacturing........................................................................................................... 35 ­ 4.3 Iron and Steel Manufacturing................................................................................................ 36 ­ 4.3.1 Integrated Steel Mills...........................................................................................................................37 ­ 4.3.2 Electric Arc Furnaces...........................................................................................................................40 ­ 4.3.3 Waste Heat from Solid Streams...........................................................................................................42 ­ vi ­ 4.4 Aluminum Production............................................................................................................. 43 ­ 4.4.1 Primary Aluminum Production............................................................................................................43 ­ 4.4.2 Secondary Aluminum Production........................................................................................................44 ­ 4.5 Metal Casting........................................................................................................................... 45 ­ 4.5.1 Aluminum Casting...............................................................................................................................46
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