GB857111A - Improvements relating to the recovery of sulphur values of acid sludge - Google Patents

Abstract

In the recovery of sulphur values from acid sludges containing H2SO4 by decomposition by <PICT:0857111/III/1> contact with hot coke to form SO2 and coke, where the combustible components of the product gases are oxidised in a combustion chamber, the coke is heated at least in part by means of direct contact with a mixture of hot SO2-containing gases from the combustion chamber and recycled cool SO2-containing gases from heating the coke. The coke may be heated in a static bed, moving bed, fluidised bed, or mechanically agitated bed, a rotary kiln, or conveyer, or elevator. The direct gas heating of the coke may be used in combination with partial oxidation of the coke, indirect heating, or direct heating from combustion products from an externally fired furnace. In Fig. 2 the SO2-containing gases from coke heater 12 pass through 4 and part is recycled through 5. The remainder of the gases pass into combustion chamber 6 where air and, if necessary, fuel are added at 7, 8 to oxidise combustible constituents. The SO2-containing gases are removed at 9 and part is withdrawn as product at 10, and part returned through 11 with the SO2-containing gases by-passed through 5 to the coke heater. Heated coke is passed through 13 to decomposer 14 where acid sludge enters at 15. Part of the coke is withdrawn at 16 and part is returned to the heater through 17. The SO2-containing gases pass to hydrocarbon removal at 18 where condensible hydrocarbons are extracted in a spray tower or heat exchanger. The remaining SO2-containing gases are passed at 19 to the heating gases before, or preferably after, the coke heater. In an alternative apparatus (Fig. 1 not shown), a separate decomposer is not used, and the acid sludge is passed to a combined coke heater and decomposer, and means for hydrocarbon condensation is not provided.