Sulfur Price Up 80%: Why HPAL Pays for Acid Twice

Indonesian high-pressure acid leaching (HPAL) is one of the main sources of nickel and cobalt sulfates for batteries. Its cost structure is tied to sulfur: sulfur is burned on site, the gas is converted into sulfuric acid, and the acid dissolves the ore. When the sulfur price rose by 80%, every tonne of acid became more expensive. The acid is paid for twice. It is bought first as sulfur; after leaching, a large part of it remains in the waste and is quenched with limestone, which releases CO2 and produces heaps of waste for landfills. This preprint describes how ARBOK-ACID, an ambient-temperature vacuum separation, regenerates spent sulfuric acid at up to 1 kWh/m3 without a neutralizer or membranes and returns it to the process together with the water, while metals and salts leave as dry concentrates. ARBOK-Cobalt recovers cobalt already dissolved in the same wastewater stream. ARBOK-SULPHUR and ARBOK-SA show where sulfur and acid can be obtained from waste instead of the market.