GB932058A - Improvements in or relating to shaft kilns for burning limestone - Google Patents

Abstract

932,058. Shaft kilns; recirculating combustion products. PRIEST FURNACES Ltd. Aug. 17, 1961 [Aug. 19, 1960], No. 28867/60. Classes 51 (1) and 51 (2). A limestone burning kiln, especially for small size limestone, with a rectangular shaft, contains upper and lower horizontal hot gas inlet flues in each side wall connected to the shaft by horizontal ducts; upper and lower horizontal waste gas outlet flues disposed above and below the lower hot gas flues, and connected to the shaft by horizontal ducts and to the inlet side of a fan; a horizontal waste gas flue in each side wall, connected to the outlet side of the fan and also to a furnace chamber; cold air inlets at the bottom of the shaft, and a horizontal flue for preheated air in each side wall above the cold air inlets, which is connected to the shaft by horizontal ducts and to a burner in the furnace chamber which is in turn connected to the upper and lower hot gas flues. As shown in Fig. 1, the kiln is heated by an oil burner 31 which receives preheated air through ducts 33, 34 and fan 30 from the flues 27, the air having been drawn in cold through openings 26 in order to cool the limestone in the air preheating zone 18. The hot combustion gases mix in the furnace chamber 21 with hot air drawn from the waste gas flues 44, 50 by the fan 24 and passed back across the shaft through flues 19. These gases are then passed into the limestone at the top and bottom of the burning zone 17 through flues 40, 35. At the top of the shaft are outlet ports 80 leading to waste gas pipes 81, an exhauster 82 and a stack 83, and also outlets 84 leading to draught stacks 85. The embodiment of Fig. 5 shows a kiln heated by blast furnace gas which is drawn in cold through an inlet 65 of a preheater 64, passing up through the preheater and out through a pipe 70, being heated by descending waste gases extracted from the kiln through flues 66 above the upper hot gas flues 40, which are then exhausted from the preheater. Preheated air from duct 27 mixes with the hot combustion gases in the furnace chamber 21, and the limestone is cooled by cold air supplied to flues 74 and ducts 73 by a fan, through pipes 75.