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Metal Casting Technologies : December 2007
METAL Casting Technologies December 2007 51 nvironmentally friendly furnace design is not a new concept. You could equally call it good furnace design or maximizing furnace efficiency. In this paper we begin by reviewing the impact that various fuels have on the environment. In particular we look at the carbon emission from both natural gas and electricity in the State of Victoria, Australia. We then review the issues that make for efficient furnace design. These design issues are linked to their environmental impact by way of a few examples. One may question why spend our natural resources recycling? The answer is that it uses far less energy to recycle aluminium than it does to produce it in the first place, as indicated in Figure 1. The primary Aluminium industry uses as much as 15% of Australia's electricity . The efficient reprocessing of scrap is essential in reducing the use of our fuel resources and reducing emissions. This paper is not trying to address the challenges facing primary smelters but rather look at issues that can help improve the performance of secondary melting furnaces. All of us need to play our part and be ready for the inevitable day when we will pay a higher price for our use of energy and generation of Carbon emissions. Furnace types are as varied as the scrap, so the following points need to be seen as a general guide. ENERGY AND CARBON EQUIVALENT Electricity in Victoria is produced mostly by burning Brown Coal. In Victoria for every 278 kWh of electricity used, the equivalent of 407 kg CO2 is released into the atmosphere . For the equivalent amount of energy from natural gas, we produce an equivalent of 58.9 kg of CO2. Regardless of whether we are using electricity or natural gas, we are creating CO2. To put this into perspective, if we have a natural gas fired aluminium melting furnace in Victoria melting 20,000 Environmentally friendly furnace design Brian Gooden and Jan Migchielsen look at and analyse carbon emission from both natural gas and electricity in the State of Victoria in Australia E Fuel Combustion Energy content of fuel (EC) Direct combustion emission kg CO2-e/GJ Full fuel emissions kg CO2-e/GJ Coal used in steel industry 30.0 GJ/t 93.0 100.7 Brown coal briquettes 22.1 GJ/t 105.0 109.4 Coke 27.0 GJ/t 119.5 133.3 LPG: non-transport 49.6 GJ/t 59.4 68.6 Naphtha 31.4 GJ/t 66.0 75.2 Kerosene 36.6 GJ/t 69.7 78.9 Heating oil 37.3 GJ/t 69.7 78.9 Refinery fuel 68.1 77.3 Automotive diesel: non-transport 38.6 GJ/t 69.7 78.9 Waste Methane Stock measured in GJ 51.0 56.0 Figure 1. Comparison of energy for primary and secondary melting Table 1. Fuel combustion and emission factors  TECHNICAL FEATURE