Patent GB-1132835-A (GB)
Title: A process and apparatus for decomposing an aqueous solution of iron chloride or chlorides and hydrogen chloride to regenerate hydrochloric acid values and to produce iron oxide
IPC: C01B7/03
Filed: 1965-11-29
Abstract: 1,132,835. Iron oxide; hydrochloric acid. H. L. COTTRELL (Steel Co. of Canada Ltd.). 29 Nov., 1965, No. 50626/65. Heading C1A. An aqueous solution containing iron chlorides and hydrogen chloride is decomposed to produce iron oxide and regenerate hydrochloric acid values by feeding the acid solution at a controlled rate on to a heated surface in an oxidizing atmosphere to vaporize the liquid constituents of the solution with attendant deposition of hydrated iron chlorides on the heated surface, this deposit is then decomposed by reaction with steam produced in situ by the vaporization of further solution fed to the heated surface in proximity to the deposit, and the vaporized constituents and residual solids withdrawn. The solution is preferably fed in discrete form, i.e. as drops, on to the heated surface at intervals such that each addition of solution has time to vaporize, the solid deposit being oxidized and dehydrated before the next addition of solution in the proximity of the primary deposit provides the steam necessary to hydrolyse that deposit to iron oxide. The preferred solution is a solution of ferrous chloride in hydrochloric acid, e.g. pickling liquors, which ferrous iron is oxidized to the ferric state before being decomposed to the oxide. A drip-feed evaporator suitable for the process is shown in Fig. 2. Liquor from a tank is fed into chamber 17 through a plurality of openings 18. The openings are arranged in radial groups defining an angle of 30 degrees between them, and the rate and sequence of feeding through these openings is controlled by a proportional distributer 21 (Fig. 3) having a plurality of openings 40 in the periphery of a stator 41, outlets 40 communicating with openings 18. A rotor 43 mounted with the stator is fitted with a plurality of openings 44 which are momentarily aligned with openings 40 during movement of the rotor. Rotor chamber 45 is filled from liquor feed line 47. The controlled liquor feed thus produced drops on to the hearth 20 which in the illustrated embodiment forms the roof of a combustion chamber 22 and is in the form of a circular disc having a depending wall 23 circumferentially attached to the underside which wall acts as the side wall of the combustion chamber. The lower edge of the wall rests on rollers 24 so that hearth 20 can be rotated. The lower end of wall 23 dips into water to provide a seal between evaporating chamber 17 and combustion chamber 22. Burners 35 heat the hearth to a temperature of up to 650‹ C., e.g. 428-650‹ C., preferably 510‹ C., and the feed rate is such that an area of hearth receives an addition of liquor about every 30 seconds. To ensure an even distribution of liquor over the hearth, the holes 44 in rotor 43 are increased in number towards the outside edge of the hearth to compensate for the increase area. A particular flow rate of liquor to the hearth is given as 0.35 litre/hour/in.<SP>2</SP>. Oxidizing gas e.g. 0 2  is introduced into 17 by line 58, and the solid product is removed via shoot 38 and fixed scraper 37. Gaseous reaction products are discharged through duct 14 to an extractor e.g. a water-cooled condenser 39 and the condensed product is recycled.