Patent GB-268868-A (GB)
Title: Improved process and apparatus for burning cement
IPC: F27B7/14
Filed: 1926-01-06
Abstract: 268,868. Fasting, J. S. Jan. 6, 1926. Rotary kilns for burning cement are provided at the drying or preheating zone with tubes or channels disposed on the outside of the kiln tube and communicating therewith so that the area of the passage for the combustion gases and 'the exposed surface of the material are increased. The tubes may be so connected together that the gases and the material take circuitous paths in opposite directions, and grinding means may be fitted in the tubes. Four tubes 2, Figs. 1 and 2 are firmly connected with the kiln tube 1 and communicate by openings 3 with the kiln tube and by openings 5 with a, chamber 4 having a boss 6 opening into a chamber 7 leading to a chimney 9. A wall 11 having four openings 12 closes the kiln tube 1 and the raw material fed by a chute 10 passes in part through the openings 12 into the kiln tube while the rest falls to the lowest tube 2. The combustion gases take the paths shown by the arrows and the material after traversing the tubes 2 drops on to cross partitions 13 in the kiln tube 1 whence it passes to the burning zone. The tubes 2 may be replaced by chambers in an annular belt surrounding the preheating zone and may be placed at some distance from the supply end of the kiln. Pairs of tubes 2 may be connected in parallel or in series; Figs. 8, 11 show six tubes of which every alternate one communicates by an opening 5 with a chamber 14, these tubes being connected by passages 18 at the other end with the adjacent 'tubes, which at their opposite ends communicate with the kiln tube 1 by apertures 19. The combustion gases pass to every second one of the tubes 2 by the openings 19, thence to the intervening tubes and to the chimney by the openings 5 and the chamber 14 of the kiln. The slurry passes through through the openings 5 to every alternate tube 2 and on dropping through the passages 18 is reversed by oblique vanes 30 and conveyed to the openings 19 whence it drops to the kiln tube 1 divided by three partion walls 31. Fig. 11 shows a grinding device 41 which during the rotation of the kiln runs on a path 42, being kept in position by a rod 43; this device may be fitted in each alternate tube 2. Wet slurry may be projected by atomizing nozzles 35 into each tube 2, Fig. 10, the nozzles being connected to an annular pipe 36 encircling the chamber 14 and supplied with slurry under pressure by a pipe 37 journaled in the wall of the smoke chamber 7. A flexible hose 38 connects the pipe 37 with a rotary stand-pipe 20" and funnel 40 which thus rotate with the kiln. The chambers 2 in Fig. 10 are arranged singly as in Figs. 1 and 2. The slurry may be put under pressure by a pump, and may be projected into the opposite ends of the tubes 2 so as to travel in the same direction as the combustion gases. A single stationary atomizing nozzle may project the slurry against an imperforate plane or conical wall replacing the wall 11, Fig. 1, which wall is maintained heated from the opposite side by the combustion gases. The slurry will thus be partially dried before dropping into the lowermost tube 2 and the combustion gases after leaving the chamber 4 will pass through the jet of atomized slurry so that any dust will be separated from the gases and returned to the kiln. In modifications the slurry is supplied to a stationary pipe with upwardly-directed atomizing nozzles projecting into the extension 14 of the kiln, or to a tube having staggered openings and supported between bearings on the wall of the smoke chamber 7 and the end wall 25, Fig. 11, of the kiln tube 1, rotation being imparted to the supply tube by a lug on the end wall engaging a projection on the tube. In order to allow for expansion the free ends of the tubes 2 are slidably supported on the kiln tube 1, but instead of being disposed wholly outside the kiln tube they may intersect it. For attachment to existing kilns a separately-supported extension carrying, 'the tubes 2 may be coupled to the existing kiln tube and may either be driven by it or independently rotated. The tubes 2 may be of helical shape and may be provided with helical chains to improve the heat transfer.