Novel process concept for the production of H sub(2) and H sub(2)SO sub(4) by SO sub(2)-depolarized electrolysis

Outotec open cycle (OOC) is a new low-energy process linking together production of hydrogen and sulfuric acid. While sulfuric acid is the world's most widely produced chemical by mass at approximately 200 Mt/a, the OOC gives the potential for making 4 Mt/a of hydrogen gas as a by-product. H sub(2)SO sub(4) manufacture requires a source of sulfur dioxide. 30% of world production of H sub(2)SO sub(4) is from the SO sub(2) by-product of pyrometallurgical processing of sulfur containing concentrates of metals such as copper, nickel and zinc. SO sub(2) can also be made by direct combustion of sulfur. In OOC, a divided electrochemical cell is used for SO sub(2)-depolarized electrolysis of water. SO sub(2) is fed to the anolyte and converted to H sub(2)SO sub(4), while hydrogen gas is produced at the cathode. On the industrial scale, the equipment will be in the form of a membrane electrolyzer assembly or stack. A case is described where the OOC would be connected to a pyrometallurgical plant smelting 1 Mt/a of nickel and copper concentrate, producing 1 Mt/a of H sub(2)SO sub(4) and 20 kt/a of hydrogen.