WSA process

WSA process features

The WSA process includes a number of features

  • ability to process feeds containing critical compounds such as SO3, NH3, CO2, HCN and hydrocarbons 
  • simultaneous treatment of many sulfur-containing streams 
  • simple process scheme with only a few pieces of equipment 
  • no waste by-product is produced. 
  • efficient heat recovery and maximum export of superheated steam at desired pressure 
  • very low consumption of cooling water
  • easy to combine with SCR for NOx removal

The WSA process

The WSA process is a wet gas catalytic process where the concentrated sulphuric acid is produced by condensation from a wet process gas. As the process gas is not dried prior to treatment in a WSA plant, generation of waste water and loss of sulphur is avoided.

The first process step produces an SO2 gas at the operating temperature of the oxidation catalyst in the SO2 converter. The catalytic conversion of SO2 to SO3 takes place in one or more beds of catalyst from Topsoe's VK-W series. Reaction heat is recovered between the catalyst beds by production and superheating of steam. After the last conversion step the gas is cooled and the SO3 reacts with water vapour to form gas phase sulphuric acid.

The process gas is cooled by a counter current flow of air in the proprietary WSA condenser. Hot air generated in the WSA condenser may be used as preheated combustion air or just to preheat the feed gases in order to ensure optimal energy efficiency.

The WSA condenser

The design of the WSA condenser allows controlled cooling of the process gas and condensation of the sulphuric acid without formation of acid mist. The vertical glass tubes, the brick-lined bottom section and the coated tube-plates of the condenser are designed for long service life and avoidance of corrosion.

The VK-W catalyst series

Another important element of the WSA process is the proprietary Topsoe catalysts - the VK-W series - developed for the conversion of SO2 into SO3 in the presence of water vapour. The catalysts feature high activity and stability.

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