Patent GB-1456356-A (GB)
Title: Manufacture from sulphur dioxide of elemental sulphur or a sulphur compound
IPC: C01B17/04
Filed: 1975-10-06
Abstract: 1456356 SO 2  conversion SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV 6 Oct 1975 [7 Oct 1974] 40875/75 Heading C1A A method for making sulphur or a sulphur compound other than SO 2  comprises (1) continuously supplying a gas containing sulphur oxides to a plant in which sulphur oxides are accepted from the gas on to a solid acceptor and an SO 2 -containing off-gas is subsequently released therefrom by regeneration of the loaded acceptor, the acceptance plant comprising at least 2 acceptor-containing reactors which are so operated as to provide a continuous stream of off-gas; (2) cooling the off-gas; (3) compressing the cooled off-gas; (4) passing the compressed gas to a gas holder or pressure vessel; and (5) continuously feeding SO 2 -containing gas from the holder or vessel to a plant for conversion of SO 2  to sulphur or sulphur compound. The SO 2  content of the regeneration off-gas varies from a maximum during regeneration to zero or substantially zero at the end of regeneration. During the latter period, the gas, after cooling and removal of H 2 O, may be diverted to a combustion plant. In one embodiment (Fig. 1), SO 2 -containing flue gas from line 1, mixed with off-gas from furnace 55 is passed through absorber 2. Loaded absorber 2<SP>1</SP> is regenerated by H 2  and CH 4  (8), diluted with steam (9) to yield an off-gas which is cooled to about 40 C. at 11 and 12. The cooled gas is passed via valve 24 and line 25 to furnace 55 in periods when it is substantially SO 2 -free, such as at completion of regeneration, but is passed via valve 14 and line 15 to compressor 16 when it contains SO 2 . When valve 14 is open, about 5% of the gas entering compressor 16 is recycled via 22, 23 from gasholder 19, and when 14 is closed, 100% of the compressed feed is gas recycled from 19. Off-gas from the compressor 16 is cooled at 17. A constant pressure feed to the conversion plant is bled off at valve 21 and line 20. Excess hot water, formed in the coolers, is stripped of SO 2  at 38 by injection of steam 40. The SO 2  is fed to cooler 12, and the water removed at 44. In Fig. 1, the gas-holder 19 is a constant volume vessel, within which the pressure varies as valve 14 is closed or opened in accordance with the SO 2 -content of the flue gas. Alternatively (not shown), the volume of 19 is variable (to maintain constant pressure) by altering the level of water therein in accordance with the operation of valve 14. The SO 2  conversion plant fed by line 20 may produce H 2 SO 4 , by conventional catalytic oxidation, or S in a modified Claus plant. If H 2 S and SO 2  are available in appropriate quantities, a mixture of the gases is heated and fed directly in to a first Claus catalytic zone. Where insufficient SO 2  is available, SO 2  is introduced into combustion chamber of the Claus thermal reaction zone, e.g. by means of an annular distributor with outflow openings arranged so that SO 2  is distributed around the flame obtained by partial combustion of H 2 S. Where no H 2 S is available, two-thirds of the SO 2  stream is catalytically reduced to provide an H 2 S-SO 2  mixture for a Claus plant. Alternatively the SO 2  is combusted with light hydrocarbons in O 2  deficiency to form inter alia H 2 S H and CO. In this case, remaining SO 2  is reduced by the H and CO in a catalytic stage preceding the conventional Claus catalytic stage.