Growing demand of aluminium in domestic and international markets, forcing aluminium producers to modify their smelter to increase the production as well as to reduce the electricity consumption, though to build a new aluminium smelter plant is one of solution to meet this demand. This article is described modification one of the aluminium smelter plant in North Sumatera Province, Indonesia as a parts of aluminium smelter upgrading project to reach production up to 300,000 TPY.