Abstract : This paper briefly discusses the development of gas-fired vacuum furnace technology, focusing on the main furnace type, structure and characteristics of gas-fired vacuum furnace, as well as the characteristics of regenerative radiant tube gas vacuum furnace technology, HTAC burner structure and furnace. Internal temperature distribution, heat balance calculation and NOX characteristics. At the same time, the technical and economic benefits of electric furnace and gas vacuum furnace are introduced, and the research, development, popularization and application of high temperature air combustion technology natural gas gas heat treatment technology equipment are discussed.
Keywords : gas-fired vacuum furnace, regenerative radiant tube, high-temperature air combustion technology, natural gas
1 Overview
The oil crisis of the 1970s caused a great blow to the economy of Western countries. Since then, Europe, the United States, and Japan have placed great emphasis on the efficient use of heat treatment energy and improved thermal efficiency. Since electricity is a secondary energy source, the power generation efficiency of general fuel is ～36%, and the thermal efficiency of electric energy is generally about 80%, so the electric heating efficiency of fuel is about <29%. In the 1997 heat treatment industrial research project, the United States listed the diversity of furnace heat sources, burner structure improvement and oxyfuel combustion technology development projects. In the 1999 technology development plan, technologies for improving heat source materials, developing ceramic radiant tubes, improving heat source forms, and improving heat source convection were proposed to improve the thermal efficiency and technical level of primary fuels. Europe and Japan are also promoting the rational use of energy in this field, and developing industrial furnace technology that promotes low fuel consumption and high thermal efficiency. The development, development and promotion of gas vacuum furnace equipment and technology is the result of this technical policy and industrial demand in Europe and the United States [1-5]. Compared with the vacuum furnace which is usually electrically heated, the gas vacuum furnace has the following advantages [1]: 1. Higher productivity, high thermal efficiency; 2. Lower operating cost; 3. Reduced maintenance; 4. Powered All the advantages of heating the vacuum furnace.
American scientific researcher SJSikica et al. launched their gas vacuum furnace in 1992, including 675 ° C gas vacuum furnace (horizontal) and medium temperature 955 ° C gas vacuum furnace. At the same time, the vertical loading high temperature (1010 ° C) vacuum quenching furnace was developed. For gas vacuum furnaces with operating temperatures of 1200 ° C and higher, the group is also under development [2].
Researchers and engineers from the American Gas Research Institute and Abar Ipsen Co. developed the gas ion nitriding furnace [3]. Operating temperature (315 ~ 540) ° C, temperature uniformity DTmax? 4 ° C, effective heating zone size (L? W? H) is 915mm * 610mm * 455mm, working load 545kg. Figure 1 is a simplified diagram of a gas ion nitriding furnace [3].
SB Gupta of Ipsen, Germany, discusses the development technology of gas vacuum furnaces, and introduces several gas vacuum furnace design structures and new models developed in recent years [4].
The gas vacuum furnace uses natural gas as the energy source, and the thermal efficiency can reach 65%, which is more than double the thermal efficiency of the electric energy vacuum furnace. Figure 2 shows a comparison of energy costs per unit of electricity and natural gas.
As mentioned above, due to the high productivity, high thermal efficiency and low production cost of the gas vacuum furnace, this technology has developed rapidly since its inception in 1986. Table 1 lists the production of major gas vacuum furnace manufacturers in recent years. Quantity list:
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