Calculation And Analysis Of Energy Consumption Of Al Alloy Melt Preparation And Supplying

In order to provide basis for the energy consumption evaluation, the standardization of energy measurement and energy consumption has been proposed recently by C hinese government to encourage the development and use of technologies with raised energy efficiency, to strength the management of energy use and to achieve improved production profit with reduced energy consumption. However, the energy consumption measurement and evaluation methods for melt preparation and supply process of aluminum die-casting industry have not been available to date in China.In order to promote the establishment of the measurement and evaluation methodologies of melt preparation and supply process, the present study has been devoted to thermodynamic calculation of theoretical energy consumption of Al melt preparation and supply, processing technique investigation of the representative melt preparation and supply process in a leading die-cast plant, accompanied by detailed recording of the energy consumptions in each processing steps and in depth analyses of the mechanisms behind. As conclusions, the evaluation method s of energy consumption in each processing steps were put forward, the potentials for energy saving were pointed out to guide the following up R&D and to support the standardization of energy measurement and evaluation during melt preparation and supply process for Al die casting. The main conclusions of this paper are detailed as follows:① The heat inputs of the whole process of Al melt preparation and supply are the heats of fuel combustion and oxidation reactions of alloying elements, the heat outputs are physical heats of Al melt and slag, radiation of furnace brickwork and door, and physical heat of exhaust gases. Accordingly, a heat equation was constructed according to the law of energy conservation.② Except for the energy consumption in the form of heat loss during melt and solid material transportation within the process, the energy consumed on melting furnace(73%), finery(5%) and holding furnace(22%) for preparing and supplying a tonnage Al melt is 103 Nm3 natural gas in total.③ The energy consumption of the melting furnace is 75Nm3 natural gas per tonnage Al melt, in which, 44% of the heat generated is effectively used, while 35% wasted in the form of exhaust gas, 8% in the form of brickwork radiation, 2% in the form of slag physical heat and 4% in form of furnace door radiation, respectively;④ Theoretically, the temperature of Al melt in the finery and holding furnace does not change, so their energy efficiency is zero. For the finery, the physical heat of slag accounts for 7% of the energy consumption, the radiant heat of furnace door accounts for 23%, the physical heat of exhaust gas accounts for 38% and the radiant heat of brickwork accounts for 21%. For the holding furnace, the physical heat of slag accounts for 0.5%, the radiant heat of furnace door accounts for 23%, the physical heat of exhaust gas accounts for 35% and the radiant heat of brickwork accounts for 24.5%.⑤ According to the energy consumption distributions in the process and on the equipment, an energy effective approach is proposed as "to complete the entire Al melt preparation and supply process(namely charging, melting, refining, holding and pouring) in a single furnace, the so-called integrate furnace. Thus, any unnesessary heat loss caused by the exhaust gas, the furnace doors and the brickworks can be minimized, logistic energy consumption is eliminated to significantly increase the heat efficiency of the process.⑥ The energy consumption for an integral furnace to prepare and supply a tonnage Al melt to a die-caster is about 54Nm3 natural gas with an exhaust gas temperature of 150 oC.