GB1341278A - Calcining apparatus - Google Patents

Abstract

1341278 Calcining kilns VEITSCHER MAGNESITWERKE-AG 19 April 1971 [22 Jan 1970] 24868/71 Heading F4B A plant for calcining materials includes a material preheater 1, at least two independently firable rotary kilns 4, 5 and a cooler 6 through which the material successively passes, the plant being operable in various ways. According to a first high temperature calcining method, the kiln is fired by burner 12 fed with oxygen or oxygen-enriched air through line 13, and the kiln 4 by burner 8 fed with preheated combustion air, which may be oxygen enriched, from cooler 6 via line 9, the waste gases from the two kilns passing independently into preheater 1. Partially calcined material may be extracted from stationary head 14. In other lower temperature methods, either burner 12 and oxygen supply line 13 may be shut off and valves (not shown) in the lines 9 and 16 closed, so that combustion air from cooler 6 passes through kiln 5 which now acts as an afterburner, on its way to calcining kiln 4, or burner 8 is turned off with the valves in the lines 9 and 16 closed so that waste gases from kiln 5 pass through kiln 4 on their way to preheater 1. In a modification (Fig. 3, not shown) three such rotary kilns are provided to give greater operational flexibility. The materials to be calcined may include magnesite, dolomite, limestone or other carbonates, oxides or hydroxides.