The quencher column is a part of Tail Gas Treating (TGT) section in Sulfur Recovery Unit (SRU). The column is used to cool the gas containing H2S, CO2 and SO2 by using direct counter-current contact with circulation water. Soda caustic (NaOH) is injected to the quench water to neutralize the acid in the solution.
The quench water pH is one of the main parameters of maintaining the integrity of the whole quench water system. Failure to maintain the quench water pH within safe limits will cause negative effects to the system. pH neutralization is a complex issue since the required amount of neutralizer injected to the system will be very much dependent on the amount of acid and slippage of CO2 to the system. Further, operationally it is not easy to comply with "tight" pH specification.
This paper describes the failure of TGT quencher system due to low quench water pH, includes failure investigation, process and operating parameters, analysis and conclusion. This paper will also describe all the recommended action to improve the process to control corrosion.