ITP Metal Casting: Theoretical/Best Practice Energy Use In
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Theoretical/Best Practice Energy Use In Metalcasting Operations J. F. Schifo J.T. Radia KERAMIDA Environmental, Inc. Indianapolis, IN May 2004 Prepared under Contract to Advanced Technology Institute North Charleston, SC for the U.S. Department of Energy Industrial Technologies Program Washington, DC Industrial Technologies Program Boosting the productivity and competitiveness of U.S. industry through improvements in energy and environmental performance Errata Sheet This is a listing of the corrections that were made since the original posting of the Theoretical/Best Practice Energy Use In Metalcasting Operations in April 2004. Text Errors • Cover, in the title Metal Casting was two words and changed to one word “Metalcasting”. • Page 9, the following sentence was inserted. “This study, therefore, utilized actual metalcasting energy usage by facility type to calculate the total energy used by alloy, rather than summaries of energy consumption data by NAICS codes.” • Page 9, the following sentence was removed: “It is estimated that the industry consumes 466 trillion Btu tacit energy annually.” • Page 10, Table 9, the total 2003 row was deleted. • Page 52, Table 31, removed total row and re-labled header on second column to “2003 Benchmark Tacit Energy.” • Page 52, Table 32 removed total row and re-labled second column to “2003 Benchmark Tacit Energy.” • Page 62, Table 37 was removed and tables 38 through 56 where renumbered accordingly. 1 TABLE OF CONTENTS EXECUTIVE SUMMARY ........................................................................................................... 4 INTRODUCTION ...................................................................................................................... 6 OBJECTIVE.................................................................................................................................. 6 RESEARCH METHODOLOGY..................................................................................................... 6 METALCASTING INDUSTRY PROFILE....................................................................................... 8 ESTIMATED ENERGY USE IN THE METALCASTING INDUSTRY.............................................. 9 CHAPTER 1. MELTING........................................................................................................... 15 SECTION 1. THEORETICAL MINIMUM.................................................................................. 15 SECTION 2 – BEST PRACTICE .................................................................................................. 18 IRON CASTINGS – MELTING................................................................................................. 18 Induction Furnaces ........................................................................................................... 19 Cupola Melting Furnaces.................................................................................................. 25 STEEL CASTINGS – MELTING ............................................................................................... 32 ALUMINUM CASTINGS – MELTING...................................................................................... 34 OTHER NONFERROUS ALLOYS – MELTING.......................................................................... 40 RECOMMENDATIONS – Cu-Mg-Zn................................................................................. 41 RECOMMENDATIONS – FERROUS AND NONFERROUS ................................................ 42 SECTION 3 – MELTING ENERGY AND CO2 EMISSION REDUCTIONS................................... 43 CHAPTER 2. METALCASTING ............................................................................................... 46 SECTION 1. METALCASTING METHODS............................................................................... 46 CAST IRON MOLDING PROCESSES ....................................................................................... 46 STEEL MOLDING PROCESSES ............................................................................................... 47 NONFERROUS CASTING PROCESSES .................................................................................... 48 SECTION 2. CASTING YIELD AND SCRAP ............................................................................. 51 CHAPTER 3. OTHER ENERGY REDUCTION OPPORTUNITIES ............................................ 55 SECTION 1 – ENERGY REDUCTION OPPORTUNITIES ........................................................... 55 ANALYSIS OF METALCASTING ENERGY REQUIREMENTS................................................... 55 Heat Treating Operation................................................................................................... 58 Ladle Heating.................................................................................................................... 59 Energy Conservation Programs ........................................................................................ 60 Energy and CO2 Reduction Summary .............................................................................. 60 SECTION 2 – COMBINED HEAT AND POWER ANALYSIS ...................................................... 61 Use of Waste Energy ......................................................................................................... 62 Evaluation Methodology .................................................................................................. 62 A Perspective on Exergy.................................................................................................... 64 PRIME MOVERS FOR COMBINED HEAT AND POWER AND ONSITE DISTRIBUTION GENERATION ........................................................................................................................ 66 WASTE HEAT RECOVERY OPPORTUNITIES ......................................................................... 71 APPLICATION OF PRIME MOVERS TO POWER GENERATION............................................. 76 ASSESSMENT OF GENERATION POTENTIAL FOR SPECIFIC FOUNDRY OPERATIONS ........ 78 Cupola Melting Furnace ................................................................................................... 79 Aluminum Stack Melter.................................................................................................... 83 2 Steel Casting Heat Treating .............................................................................................. 84 Ductile Iron Pipe Heat Treating........................................................................................ 85 CHP SUMMARY .....................................................................................................................86 GLOSSARY OF TERMS............................................................................................................ 91 REFERENCES........................................................................................................................... 94 APPENDIX “A” ....................................................................................................................... 97 APPENDIX “B” ..................................................................................................................... 105 3 EXECUTIVE SUMMARY The energy used to melt one ton of metal in a metalcasting facility is significantly higher than the theoretical minimum requirements. The theoretical requirements can be calculated for melting and annealing processes. The large variety of other casting processes and value added work performed at some casting facilities, however, makes it difficult to calculate the theoretical minimum requirements for the entire facility. Energy use also varies widely among facilities with differing sales volumes and dissimilar production castings for different end use market segments. This study determined the theoretical minimum energy requirements for melting processes for all ferrous and nonferrous engineering alloys. Detailed energy consumption data for best practice melting methods were only available for three processes: Iron Induction Melting, Iron Cupola Melting, and Aluminum Reverberatory Melt Furnaces. Comparative data for the three processes are summarized in Table 1 and covered in detail in Chapter 1. Table 1 - Comparison of Practical Minimum, Theoretical Minimum and Best Practice Minimums for Selected Processes (Delivered kWh/Ton Melt) Best Tacit Best Theoretical Industry % Practice % Practice Selected Processes Minimum Average Difference Minimum Difference Minimum Iron Induction Melting 351.5 796.3 56% 538.1 35% 1,689.5 Iron Cupola Melting 351.5 1,413.6 75% 1,002.5 65% 1,124.5 Aluminum Reverberatory 288.7 1,399.8 79% 510.5 43% 523.2 Melt Furnaces These best practice melting processes include iron and aluminum castings production. Iron and aluminum castings production accounts for 84 percent of the total castings produced in the United States and 82 of the tacit energy used by the casting industry sector. Tacit energy is a term used to describe an energy value that equals the combination of onsite energy consumption, the process energy required to produce and transmit/transport the energy source, and feedstock energy. Table 1 gives the theoretical minimum energy requirements to melt one ton of metal, ignoring all efficiency loses, along with the industry average and the best practice. The best practice is considered the minimum energy required to melt one ton of metal at an operating foundry. The last column of Table 1 gives the tacit energy requirements in addition to