2020 REFINING PROCESSES HANDBOOK PROCESS CATEGORIES COMPANY INDEX TREATING, GAS/LIQUID Spent acid regeneration Application: The Wet gas Sulfuric Acid (WSA) process treats spent sulfuric acid from alkylation, as well as other types of waste sulfuric acid in the petrochemical and chemical industries. Amine regenerator offgas and/or refinery gas may be used as auxiliary fuel. The regenerated acid typically contains 98.5% H2SO4 and can be recycled directly to the alkylation process. The WSA process is also applied for conversion of hydrogen sulfide H2S and removal of SOx. Description: Spent acid is decomposed to SO2 and water vapor in a combustor using amine regenerator offgas or refinery gas as fuel. The SO2 containing flue gas is cooled in a waste-heat boiler and solid matter originating from the acid feed is separated in an electrostatic precipitator or other type of filter. By adding preheated air, the process gas temperature and oxygen content are adjusted before the catalytic converter converts SO2 to SO3. The gas is cooled in the gas cooler, whereby SO3 is hydrated to H2SO4 (gas), which is finally condensed as 98%-98.5% sulfuric acid. The WSA condenser is cooled by ambient air. The heated air is used as combustion air for increased thermal efficiency. The heat released by combustion and SO2 oxidation is recovered as HP superheated 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 SO3 formed by the acid decomposition would otherwise be lost with the wastewater. The WSA process is characterized by: * No generation of 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 * Inherent safety against hydrogen explosions due to absence of stainless-steel absorbers * High sulfur recovery efficiency, low emissions. Stack gas Superheated steam Blower Combustion air Filter BFW Steam drum Dust Spent acid H2S gas/ fuel gas SO2 converter Combustor WHB Blower Interbed cooler Interbed cooler Gas cooler Air WSA condenser Acid cooler Product acid Installations: More than 160 units worldwide, including 25 for spent acid regeneration Licensor: Haldor Topsoe A/S Website: topsoe.com/processes/sulfur-removal Contact: emdg@topsoe.com Copyright © 2020 Gulf Energy Information. All rights reserved.http://www.hydrocarbonprocessing.com/ http://www.topsoe.com/processes/sulfur-removal