Implementation of Metal Casting Best Practices - EERE - U.S. ...

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7. Common Energy-Saving Solutions The assessment team found some energy-reducing solutions that may be commonly applicable among all the facilities visited. These included optimizing the melting operation and metal handling overall and implementing an energy management program to take advantage of easily achievable opportunities. These solutions should be replicable at metal casting facilities with little or no capital investment. 7.1 Optimizing Melting and Heat Treating Operations The energy efficiency of any metal casting facility depends largely on the efficiency of its melting and heat treating operations. Combined, these two operations represent over 60% of the total process energy costs for a typical metal casting facility. 33 Therefore, any improvement in the energy efficiency of these operations will have a significant impact on a facility’s bottom line. By implementing some simple operating practices and incorporating some cutting-edge melting equipment, metal casters can take advantage of such opportunities. 7.2 Covering the Furnace and Maintaining Refractories Furnaces at many of the facilities visited as part of this analysis were found to be inadequately covered when melting or holding (and in some cases heat treating), have worn refractory material lining their furnaces, and be inadequately insulated. The practice of not keeping the furnaces covered was a result of oversight by employees and/or convenience (i.e., it enabled them to throw a charge into the furnace when needed). The worn refractory lining was primarily due to the harsh operating conditions and had reached the point where it needed repair. Not keeping the furnace covered and the refractory in optimal condition are major sources of inefficiency as they allow heat to escape from the furnace through a combination of radiation, conduction, and convection losses. These losses can account for 10 to 50% of total energy losses depending upon furnace design, operating practices, metals melted, and the source of energy used. 34 An improperly insulated furnace leads to additional conductive energy losses. A simple step to minimize these excessive losses in melting and heat treating operations is to ensure that employees keep the furnaces properly sealed and open the lid only for charging and tapping the melt. Having a strict policy of keeping the furnace door closed is a no-cost solution to reducing energy consumption. Radiation losses from an uncovered bath can reach up to 130 kW per hour for an iron furnace with a 10-ton capacity. 35 Furthermore, the facility should monitor regularly the wear and tear on furnace refractory linings. Insofar as is possible, they should carry out repairs during the annual facility maintenance shutdown. Finally, they should utilize the optimal thickness of insulating material on the outer furnace shell. The U.S. Environmental Protection Agency (EPA) estimates that a properly maintained insulating system can improve thermal efficiency of heating equipment by as much as 50%. 36 DOE estimates that installing thermal insulation, maintaining the refractory lining, and keeping furnace lid properly covered can potentially have a payback period of one year or less in some industrial process heating applications. 37 28
7.3 Examine Advanced Retrofitting Technologies Many advances in retrofitting ferrous and nonferrous melting technologies can significantly reduce energy consumption in melting operations. Such technology advances include installing oxygen-enriched fuel combustion, preheating charge material, and recovering heat from flue gases can improve the efficiency in various steps in the melting operation. Exhibit 11 shows the estimated efficiency savings achievable by implementing these technologies. Furnace efficiency can increase from 25-30% by utilizing one or a combination of these technologies. Exhibit 11: Estimated Efficiency Improvement from Retrofitting Technologies Melting Technology Estimated Efficiency Savings Charge Preheating 5-10% Air Preheating 10-20% Operational Adjustments 0-30% Oxygen Enrichment Technologies Source: Albany Research Center, Improving Energy Efficiency in Aluminum Melting presentation at 2005 Aluminum Portfolio Review 1-40% Employing oxygen-enriched fuel combustion has attracted substantial attention in the metal casting industry because of the increasing demand to reduce harmful emissions, in particular NOx. These systems also improve the energy efficiency of a furnace because they decrease the electrical energy and increase the chemical energy. The energy efficiency improvement can be as high as 40%. However, oxygen in a furnace can also cause greater oxidation, especially in aluminum melting. Also, some foundries worry about wearing their furnace refractory at a higher rate due to the increased combustion rate. A metal caster should balance these competing effects and work with a burner manufacturer who knows how to design these systems optimally to obtain low NOx emissions with minimal heat loss. 38 Further efficiency improvements can occur in the melting and heat treating operation with the utilization of heat recovery methods. Recovering waste heat can improve efficiency by as much as 20%. Waste heat recovery devices simply transfer thermal energy from high-temperature effluent streams, such as furnace flue gases, to a lower-temperature input stream, such as incoming combustion air. 39 For example, preheating charge material is an important retrofit technology that has proven to save facilities between 5 to 10% in energy costs. Using the hightemperature off gas from the melting furnace to preheat the incoming scrap or ingot can reduce melting energy requirements for both ferrous and nonferrous operations. Scrap preheating in steel foundries has proven to reduce the energy for melting by 50-70 kWh per ton. 40 Besides improving energy efficiency, preheating will also remove moisture from the scrap or ingot, thus ensuring a cleaner melt. More foundries should seek to improve the efficiency of their melt operation. During this project, the assessment team did not observe any facility using such retrofit technologies in its melting operation. The participants could have significantly lowered their energy bills by incorporating these retrofit technologies, many of which can work in conjunction with existing furnace technologies, thereby requiring less capital investment when compared with upgrading the entire melting facility. 29
Page 2 and 3: Implementation of Metal Casting Bes
Page 4 and 5: Executive Summary Since 1995 the U.
Page 6 and 7: summarized comments regarding the t
Page 8 and 9: • Metal casters must investigate
Page 10 and 11: F. Iron Foundry-2..................
Page 12 and 13: As part of this project, an assessm
Page 14 and 15: 1.3 Report Organization This report
Page 16 and 17: energy needs, primarily to the larg
Page 18 and 19: As a result of this strategy, ITP h
Page 20 and 21: All of the facilities that particip
Page 22 and 23: A number of the facilities visited
Page 24 and 25: Steel Foundry Aluminum Foundry Alum
Page 26 and 27: 4. Methodology for Assessing Indust
Page 28 and 29: 5. Overall Assessment Observations
Page 30 and 31: samples and measurements from vario
Page 32 and 33: the Metalcasting Congress and other
Page 34 and 35: single in-line memory module (SIMM)
Page 36 and 37: application can offer tangible bene
Page 40 and 41: 7.4 Installing Radiant Panels in Cr
Page 42 and 43: 7.8 Installing Energy-Efficient Lig
Page 44 and 45: 8. Conclusion The ITP Metal Casting
Page 46 and 47: Appendix A: Plant Assessment Case S
Page 48 and 49: Scrap Rate The scrap rate at the pl
Page 50 and 51: Dross Management Metal dealers and
Page 52 and 53: B. Die Casting Plant-2 Plant Profil
Page 54 and 55: Quality Control The assessment team
Page 56 and 57: C. Steel Foundry-1 Plant Profile St
Page 58 and 59: also enables foundries to understan
Page 60 and 61: Automated Molding Line Steel Foundr
Page 62 and 63: D. Steel Foundry-2 Plant Profile St
Page 64 and 65: subsequent machining operations. Ex
Page 66 and 67: motor, with an older piece of equip
Page 68 and 69: 1. Implemented Best Practices Age S
Page 70 and 71: Treating Sand Iron Foundry-1 reclai
Page 72 and 73: F. Iron Foundry-2 Plant Profile Iro
Page 74 and 75: Working with the Utility Iron Found
Page 76 and 77: G. Lost Foam Foundry-1 Plant Profil
Page 78 and 79: work yielded a 0.85% reduction in s
Page 80 and 81: Stack Melter Like many plants melti
Page 82 and 83: tools. Like many of the other facil
Page 84 and 85: will require that the facility have
Page 86 and 87: 1. Implemented R&D and Best Practic
Page 88 and 89:
V-6 blocks, the gating system was c
Page 90 and 91:
During their site visit, the team f
Page 92 and 93:
J. Aluminum Casting Facility-2 Plan
Page 94 and 95:
promoting a product line for the fa
Page 96 and 97:
Another alternative for the facilit
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K. Copper Foundry-1 Plant Profile C
Page 100 and 101:
The facility also stays abreast of
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Electric Arc Furnace (EAF) - A stee
Page 104 and 105:
Sprue - Metal that fills the conica
Page 106 and 107:
23 Stratecast, Inc. AFS Metalcastin
Page 108:
99 Ibid. pg. 335. 100 http://www.go
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