Improving the thermal characteristics of furnaces and the operating conditions of the lining by improving direct-flame-impingement methods for intensifying the heating of metal

Abstract

This article discusses Russian research and development of the direct-flame-impingement method of heating and modifications made to this technology abroad in the form of the DFI and Oxy-fuel heating systems. It examines the advantages of these heating methods, especially the sharp reduction in refractories use and the substantial improvement in the service conditions of the furnace lining. Various designs of direct-flame-impingement heating furnaces are presented and aspects of their thermal performance are discussed. It is shown that the thermal efficiency of modern furnaces which employ direct flame heating can reach 65% and that emissions of nitrogen oxides from these units do not exceed 30 ppm even when the combustion air is preheated. The efficiency of using oxygen in natural-gas-fired heating furnaces is evaluated for different natural-gas prices. Relations are obtained to describe the effect of the degree of oxygen enrichment of the combustion air on the consumption of natural gas and oxygen individually and the consumption of natural gas + oxygen. The cost-effectiveness of using gas-oxygen burners in melting furnaces is also examined. © 2013 Springer Science+Business Media New York.