Recovery of sulphur

摘要

In the production of sulphur from gases containing sulphur dioxide, such as roaster or smelter gases, the gases are treated with reducing gases, e.g. water gas, producer gas, or natural gas, or with a gaseous suspension of a powdered fuel. The hot roaster gases, at a temperature of about 800 DEG C. are passed rapidly through a dust collector and are then introduced with the reducing gas into a previously heated reaction chamber where the reduction to elemental sulphur is effected. The temperature of the gases should not be less than 1000 DEG C. in order that the reaction may proceed rapidly. Preferably, when a reducing gas is used, the necessary heat is obtained by heat exchange between the outgoing products of reaction and one or both of the reacting gases. In the case of powdered fuel, additional heat is necessary and this is supplied by the combustion of part of the fuel by the addition of air either just prior to or on entry into the reaction chamber. The cooling of the products of reaction by heat exchange should be such as to reduce their temperature quickly to below 500 DEG C. to prevent any large formation of carbon oxysulphide; for this purpose also the rate of flow through the reaction chamber is made rapid and the resultant gases are quickly cooled, preferably by passage through a waste heat boiler, to 300-400 DEG C. after which the sulphur is removed. The carbon oxysulphide and any sulphuretted hydrogen are removed by sulphur dioxide contained in the reaction gases or introduced therein, the gases being passed over a suitable catalyst such as aluminium oxide or bauxite. Alternatively the reaction between sulphur dioxide and carbon oxysulphide is facilitated by passage over bauxite and that between sulphuretted hydrogen and sulphur dioxide by silica gel. As shown, pyrites &c. is fed from a hopper 3 to a roasting furnace 1, air or other oxidizing gas being introduced by pipes 4. The roaster gases are withdrawn by a fan 12 through a pipe 7 and a dust collector 8 and are fed tangentially by a pipe 9 into the base of an annular reaction chamber 10 surrounding the furnace 1, the reducing gases being introduced tangentially by a pipe 11. The outer wall of the chamber 10 is highly insulated but the dividing wall 2 is made thin to promote heat exchange. Products of reaction, including the elemental sulphur, escape by a pipe 13 preferably arranged tangentially. Heat exchange between the reacting gases and the roasting chamber may be used to prevent scar formation due to the fusing of the iron sulphide, the absorption of heat being mainly effected before the reacting gases come into contact by passing either the reducing gas or the roaster gases through a jacket surrounding that portion of the furnace where the tendency for scar formation is the greatest, and then passing both gases to a jacket surrounding another part of the furnace or into a separate reaction chamber. Alternatively, both sets of gases may be passed round the scar zone at such a speed that the heat generated by their reaction will not be detrimental, the reaction being completed in the second zone referred to or in a separate reaction chamber.