Process for recovering elemental sulfur from gases having a high carbon dioxide content and containing sulfur compounds

A process for recovering elemental sulfur from a gas continuous inorganic and/or organic sulfur compounds together with carbon dioxide and impurities which may include hydrogen cyanide and unsaturated hydrocarbon, said process comprising the steps of:

• a. combining said gas with a combustion promoter and burning same with a slight excess to produce a combustion gas stream;
• b. contacting said combustion gas stream with coke at a temperature of 300.degree. to 450.degree. C to remove residual oxygen, sulfur trioxide and nitrogen oxides from said combustion gas stream and forming a prepurified gas stream;
• c. thereafter cooling said prepurified gas stream to a temperature of 20.degree. to 80.degree. C and scrubbing same with an aqueous solution of an absorbent selelected from the group which consists of alkali salts of weak inorganic acids and organic acids, and amines, thereby absorbing in said solution sulfur dioxide from the prepurified gas stream;
• d. heating said absorbent and stripping sulfur dioxide from said absorbent and forming a hot SO.sub.2 -containing gas stream;
• e. cooling the SO.sub.2 -containing gas stream and removing water by condensation therefrom;
• f. adding hydrogen to said SO.sub.2 -containing gas stream and following step (e) and reacting the resulting mixture at a temperature of 200.degree. to 450.degree. C on a catalyst selected from the group which consists of oxides of cobalt, oxides of nickel, oxides of molybdenum and oxides of tungsten to reduce the SO.sub.2 and form a sulfur and H.sub.2 S-containing gas stream;
• g. separating from the sulfur and H.sub.2 S containing gas stream resulting in step (f) by cooling elemental sulfur and recovering same;
• h. admixing with the hydrogen sulfide containing gas from which elemental sulfur has been removed in step (g) an amount of SO.sub.2 stoichiomtrically sufficient to react with the H.sub.2 S thereof and passing the resulting mixture at a temperature of 200.degree. to 300.degree. C over an alumina or activated carbon catalyst to form the gas stream containing elemental sulfur;
• i. separating elemental sulfur from the gas stream formed in step (h) by cooling and recovering the elemental sulfur thus separated;
• and
• j. recycling the gas remaining after step (i) at least in part to a preceding step.