Wet gas Sulfuric Acid (WSA)
The WSA process is a wet gas catalytic process. The concentrated sulfuric acid is produced by condensation from a wet process gas. Drying of the process gas prior to treatment in a WSA plant therefore becomes superfluous, hence generation of waste water and loss of sulfur are avoided. The purpose of the first step in the process is to produce an SO2 gas at the operating temperature of the oxidation catalyst in the SO2 converter. If the sulfur in the feed is SO2, only a simple preheating is required. Other sulfurous feeds are oxidized to SO2 by combustion and then cooled to the optimum catalytic conversion temperature in a waste heat boiler. The excess heat from this operation is recovered as steam. The catalytic conversion of SO2 to SO3 takes place in one or more catalyst beds. Reaction heat is recovered between the catalyst beds by superheating of steam. After the last conversion step the gas is cooled and the SO3 reacts with water vapor to form gas phase sulfuric acid. The process gas is finally cooled by a counter current flow of air in the proprietary WSA condenser. Clean gas exits at the top of the WSA condenser, and the sulfuric acid is collected in the bottom section from where it is cooled and sent to storage. Hot air generated in the WSA condenser may be used as preheated combustion air to ensure optimal energy efficiency.