GB884703A - Decomposition of iron sulphate - Google Patents

Abstract

Sulphur dioxide and iron oxide are prepared by introducing partially dehydrated spray-dried iron sulphate, which is a very fine, substantially dry dust, into a mass of hot coarse inert particles, of size preferably 74-500m , fluidized by an oxygen containing gas, and feeding in, as a fuel, a combustible reducing agent in the form of a vapour, liquid or pulverulent solid, and withdrawing from the bed the sulphur dioxide gases produced, entraining therein substantially all the iron oxide produced. The bed conditions are such that the iron sulphate is retained therein for sufficient time for substantially complete decomposition. The bed is preferably 3-5 feet deep, and may comprise magnetite, pyrites cinder, silica, nitile, or zircon. The fuel may be introduced either mixed with or separately from the iron sulphate, and preferably at a number of distributed points below the bed surface. Fuels which may be employed include coke, charcoal, anthracite, bitumen, pitch, fuel oil, tar, creosotepitch, hydrocarbons, producer gas, pyrites, pyrrotite, native sulphur, or mixtures of the above. The preferred fuel is powdered coal, preferably of particle size below 10 BSS, and may be introduced as such or as a slurry in water or fuel oil. The fluidized bed is preferably supported on a perforated base through which the oxygen-containing gas is admitted, the orifices preferably being such that the pressure drop across the base is between 0,1 and 20 times the pressure drop across the bed, and preferably being fitted with devices which prevent solids entering the orifices. The oxygen-containing gas may be air, preferably heated to 250 DEG -600 DEG C., and the bed is preferably maintained at 700 DEG -1100 DEG C. The process is preferably so operated that the iron oxide product contains less than 5% carbon and 1% sulphur, and that the emergent gas contains up to 15% sulphur dioxide and less than 6% oxygen, preferably less than 3% oxygen. The exiting gases are preferably cooled to below 350 DEG C., for example by passing through a waste heat boiler, before separating out, for example in a cyclone, the ion oxide; any residual iron oxide may be removed by a water spray. Sulphur dioxide thereby dissolved may be stripped by means of an air stream. Specifications 721,591 and 800,410 are referred to.