Improving the Performance of the Annular Furnace at PAO ChTPZ

Resumo

Abstract—The productivity of rolling and pipe-rolling mills and the product quality may be improved by heating the metal billet in furnaces with minimum oxidation and decarburization. That is possible in annular furnaces, which are widely used in the rolling of pipe and railroad wheels. High-quality heating permits the creation of metal structure with specified thermophysical and operational properties, as well as the plasticity required for subsequent machining. In the present work, the operation of an annular furnace used to heat pipe blanks before rolling at PAO Chelyabinskii Trubokatnyi Zavod (ChTPZ) is analyzed. Thermal problems are considered: in particular, the high fuel consumption in heating blanks and high external temperatures of the walls and roof; the low rate of blank heating; and the serious leakage of air into the furnace’s working space. In addition, a defect of the gas-burner design is that the gas supply cannot be regulated, despite the wide load range (including periodic shutdown). Finally, practically no use is made of the thermal energy in the exhaust gases. In the analysis of these problems, the heating of the metal is calculated, and the thermal balance of the annular furnace is formulated. The analysis reveals factors that decrease the energy efficiency of the existing furnace design. Measures are proposed for furnace modernization so as to decrease the fuel productivity and increase the productivity: for example, the use of fiber refractories; regenerator burners; and barriers that are not water-cooled. To assess the effectiveness of these measures, we formulate the thermal balance of the redesigned annular furnace and analyze its thermal operation. The proposed measures are expected to provide significant economic benefit and to improve the heating of the metal, with decrease in fuel consumption and increase in productivity. In particular, after reconstruction, increase in the furnace’s total efficiency (by 18.1%) and thermal efficiency (by 31.0%) is expected, as well as decrease in fuel consumption by 48.3 kg CF/t.