GB927648A - Improvements in or relating to kilns for heat treating charges - Google Patents

Abstract

927,648. Shaft furnaces. L. VON ROLL A.G. Dec. 2, 1960 [Dec. 3, 1959], No. 41643/60. Class 51 (2). In a shaft furnace for burning cement, lime, dolomite &c. by burning a fuel externally of the furnace and introducing the hot gases into the charge material provision is made for cooling air ascending the shaft to be by-passed with a minor quantity of the heating gases, the mixture being fed back into the charge material immediately below a preheating zone. As shown in Fig. 1, the shaft furnace comprises a shaft 10 with a revolving discharge grate 15, a cooling air supply pipe 27, and consecutivelyoperated discharge valves 22a, 22b and 22c forming an air lock. Charge material supplied through shoots 60 is fired by hot gases supplied from a combustion chamber 44 through a sleeve 43, part of said gases with the cooling air rising up the shaft being extracted through ducts 36a, 36b and 36c into an annular duct 33 formed between the shaft and a hood 31. The remainder of the hot gases ascends the shoots 60 to preheat the incoming material, being joined at 33b by the admixed combustion gases and cooling air from the duct 33. Dust collecting in duct 33 is fed by a line 38 through valves 39a and 39b to valve 22a. Air supplied through pipe 52 to an oil burner 57 is preheated in a jacket 50 surrounding the combustion chamber 44 and a flue 62 terminates in a jacket 61 surrounding the hood 31. In a modification, Fig. 2, the combustion chamber 80 disposed parallel to the shaft 82 discharges thereinto through an annulus 88 and ports 89. Part of the combustion gases joins the air entering a central sleeve 93, the mixture joining the rest of the combustion gases through ports 95. Another modification, Figs. 3 and 4 (not shown), has a furnace of rectangular cross-section with combustion chambers opposite each end feeding a central duct with ports opening into the shaft and bypass ducts in the opposite outer walls. A final modification, Figs. 5 and 6 (not shown), has an end combustion chamber feeding distributing ducts on the long sides of the shaft and a central by-pass duct running parallel therewith.