Ilkka Kojo

Novel process concept for the production of H 2 and H 2 SO 4 by SO 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. H2SO4 manufacture requires a source of sulfur dioxide. 30% of world production of H2SO4 is from the SO2 by-product of pyrometallurgical processing of sulfur containing concentrates of metals such as copper, nickel and zinc. SO2 can also be made by direct combustion of sulfur. In OOC, a divided electrochemical cell is used for SO2-depolarized electrolysis of water. SO2 is fed to the anolyte and converted to H2SO4, 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 H2SO4 and 20 kt/a of hydrogen.

Matte converting in copper smelting

ABSTRACT Copper matte converting is the key step to ensure high primary copper recovery in the smelting chain. Its development and the fundamental research carried out over the past decades will be reviewed. The operational challenges and environmental concern of batch-wise Peirce-Smith Converting vessel have induced more than 50 years ago attempts to continuous converting process which have materialised in the last two decades in the flash converting technology, utilised currently in one smelter in USA and three smelters in China. Their annual copper production is in excess of 1.5 Mt, and selected fundamental studies behind this major technological invention will be examined.