GB773808A - Improvements in or relating to the roasting of sulphide materials - Google Patents

Abstract

In apparatus for roasting pyrites or burning coal &c. in the form of fine or granular particles, pulsations are produced in the air supplied to a bed of the charge material, so that the reaction is facilitated and a <PICT:0773808/III/1> minimum quantity of fines is carried away with the effluent gases. As applied to the roasting of pyrites, particularly flotation concentrates, air is supplied to a substantially rectangular reaction chamber 1, Fig. 1, containing a bed 17 of pyrites through compartments 12-15 under control of valves 4-7 producing the pulsations, and valves 8-11 controlling the quantity of air. Pyrites of a particle size not greater than 20 mm., and preferably below 10 mm. is fed in at 2 and rotated at 3, movement of the charge being induced by the reaction air and/or by tilting the reaction chamber, and an offtake 19 is provided for the gases formed. The frequency of the pulsations is preferably within the range 10-100 per min. In a typical run using flotation concentrates containing 50 per cent S with an average particle size of 0.15 mm., and a pulsation rate of 30 per min., the SO2 percentage in the exhaust gases was 10 per cent calculated on dry gas. The air distribution over the compartments 12-15 was about 40 per cent in the first two, about 15 per cent in the third and about 5 per cent in the fourth compartment. The invention may also be applied to a secondary roaster of circular cross-section, Fig. 3 (not shown), disposed below a conventional flash roaster and supplied with pulsations of air through tuyeres extending through the roaster walls.