A cooling system for converter linings

Abstract

The cooling of converter linings lengthens their service lifeo A reduction in the temperature of the active surface of the lining impedes the penetration of molten slag and matte into the pores of the refractory masonry, promotes the formation of a crust, and reduces the variation of the temperature in the masonry.An analysis of the heat balance showed that 160 MJ of thermal energy (7% of the total heat input) Is lost through the lining in a coppersmelting converter and up to 320 MJ (11o5%) in a cupronickel converter.The temperature of the active surface of the lining reaches 1250~ sometimes 1350~ The temperature of the lining surface on the melt side decreases slightly and that on the shell side increases to the extent that the lining is eroded.In a 100-mm-thick lining the temperature of the masonry may reach 960~ and that on the side facing the shell 600-700~ In a thick lining the temperature gradient is variable but the temperature field levels out with a decrease in the thickness of the lining.In the zone of the tuyeres the heat flow varies 3-5 kW/m 2. in a 460-380-mm-thick lining, and 8-10 kW/m ~ in a 200-100-mm lining (natural cooling).When the difference between the temperatures of the melt and the active surface of the masonry is 20-50~(measured with an optical pyrometer) for a 400-mm-thick lining the rate of heat transfer from the melt equals 100-250 W/m2odeg K so that the heat transfer coefficient does not exceed 3 W/m2,deg K. tThe data given in this article make it possible to select the most efficient method of cooling the lining of converters for the purpose of lengthening its service life, and they explain some of the contradictions which arise in discussions of the efficiency of given methods of lowering the temperature of the active surface of the lining.The total thermal resistance R t of heat transfer can be divided into three main components; the heat-transfer resistance of the melt R~ the resistenae of the thermal conductivity of the lining and of the clearance between the lining and the shell R%, and the heattransfer resistance of the outside surface of the shell R~. The ratio between them depends on the composition of the matte and slag, the size of the melt bath, the thickness of the lining, the blast condition~, the configuration of the outside surface of the shell, the time of the year, etc. For converters operating in normal conditions R: = 0.5-3%, R% = 60-80%, and R2 = 20-40% so that the temperature of the active surface of the lining can be lowered appreciably by intensive cooling only after significantly increasing the thermal resistance of the melt and decreasing the thermal resistance of the lining and the clearance between the lining and the shell.The influence of the main factors (heat-transfer coefficient, lining thickness, and thermal conductivity) on the ratio between the components of the total thermal resistance is shown in Table i~ The heat-transfer coefficient to the melt is assumed 250 W/m2,deg K and takes into account only the direct cooling of the outside of the masonry....