Application: The WSA process (Wet gas Sulfuric Acid) treats spent sulfuric acid from alkylation as well as other types of waste sulfuric acid in the petrochemical and chemicals industry. Amine regenerator offgas and /or refinery gas may be used as auxiliary fuel. The regenerated acid will contain min. 98% H 2 SO 4 and can be recycled directly to the alkylation process.
The WSA process is also applied for conversion of H 2S and removal of SOx.
Description: Spent acid is decomposed to SO2 and water vapor in an incinerator using amine regenerator offgas or refinery gas as fuel. The SO 2 containing flue gas is cooled in a waste-heat boiler and solid matter originating from the acid feed is separated in an electrostatic precipitator. By adding preheated air, the process gas temperature and oxygen content are adjusted before the catalytic converter converting SO2 to SO3. The gas is cooled in the gas cooler whereby SO3 is hydrated to H 2SO4 (gas), which is finally condensed as 98% sulfuric acid.
The WSA condenser is cooled by ambient air. The heated air may be used as combustion air in the burner for increased thermal efficiency. The heat released by incineration and SO 2 oxidation is recovered as steam.
The process operates without removing water from the gas. Therefore, the number of equipment items is minimized and no liquid waste is formed. This is especially important in spent acid regeneration where SO 3 formed by the acid decomposition will otherwise be lost with the wastewater.
The WSA process is characterized by:
• No generation of waste solids or wastewater
• No consumption of absorbents or auxiliary chemicals
• Efficient heat recovery ensuring economical operation
• Simple and fully automated operation adapting to variations in feed flow and composition.
Licensor: Haldor Topsøe A/S.