GB870649A - Improvements in or relating to furnaces or kilns for calcining solid material - Google Patents

Abstract

870,649. Shaft furnaces. PRIEST, C. F., and KNIBBS, N. V. S. Feb. 17, 1959, No. 5528/59. Class 51 (2). Air heated by flowing upwardly through the cooling zone 11, Fig. 1, of a shaft furnace or kiln for calcining limestone &c. together with hot gases from a heating zone 12 enter ports 17 to combustion chambers 18 from where they re-enter the shaft at 23, a portion of the gases being recirculated into the zone 12 and the remainder passing upwardly through a cone 13 in countercurrent to the charge for exhaustion through conduits 24. Fluid fuel or steam is introduced into the chambers 18 at 22 by jets from blowers 21 which heat the gases from 900‹ C. at the ports 17 to 1200‹ C. in the chamber. The fuel used may be gas, gasified oil or gasified solid fuel or the injection may be of air to create the flow of gases through the furnace. In a modification, the shaft 10, Fig. 2, is divided by a vertical medial wall, not shown, and has bridges 34 in the heating zone 12 which extend from the medial wall to the side walls of the shaft to distribute the gases from the combustion chambers 18 over the full cross-section of the shaft, to minimize channelling of the charge and to shield ports 17, 23 from the descending charge. The ports 17 allow air introduced into the cooling zone 11 from inlets 16 to pass to manifolds 28 and conduits 29 to the combustion chambers 18, which have injectors 20, from where the combusted gases are led through manifolds 31 to the ports 23.