Wet sulfuric acid process
The wet sulfuric acid process (WSA process) is a gas desulfurization process. After Danish company Haldor Topsoe introduced this technology in 1987, it has been recognized as a process for recovering sulfur from various process gases in the form of commercial quality sulfuric acid (H2SO4) with the simultaneous production of high-pressure steam. The WSA process can be applied in all industries where sulfur removal presents an issue. The wet catalysis process is used for processing sulfur-containing streams, such as: H2S gas from e.g. amine gas treating unit Off-gas from sour water stripper (SWS) gas Off-gas from Rectisol Spent acid from an alkylation unit Claus process tail gas Heavy residue or petcoke-fired utility boiler off-gas Boiler flue gases from various processes SNOX flue gas desulfurization Metallurgical process gas Production of sulfuric acid The main reactions in the WSA process Combustion: 2 H2S + 3 O2 2 H2O + 2 SO2 (-1036 kJ/mol) Oxidation: 2 SO2 + O2 2 SO3 (-198 kJ/mol) [in the presence of a vanadium (V) oxide catalyst] Hydration: SO3 + H2O H2SO4 (g) (-101 kJ/mol) Condensation: H2SO4 (g) H2SO4 (l) (-90 kJ/mol) The energy released by the above-mentioned reactions is used for steam production. Approximately 2–3 tons of high-pressure steam are produced per ton of acid. Industries where WSA process plants are installed: Refinery and petrochemical industry Metallurgy industry Coal-based industry (coking and gasification) Power industry Viscose industry Sulfuric acid industry The acid gas coming from a Rectisol-, Selexol-, amine gas treating or similar unit installed after the gasifier contains H2S, COS and hydrocarbons in addition to CO2. These gases were previously vented to the atmosphere, but now the acid gas requires purification in order not to affect the environment with SO2 emission. The WSA process provides a high sulfur recovery and recovers heat for steam production. The heat recovery rate is high, and the cooling water consumption is low, which saves resources. Example 1: Feed-gas flow: 14,000 Nm3/h Composition [vol %]: 5.