Lean amine temperature has a significant impact on the overall efficiency of the natural gas sweetening process. Determining the optimal temperature of lean amine entering the absorber can be a rather difficult task, as it requires careful evaluation of multiple parameters to ensure a proper balance is achieved between acid-gas removal and efficient operation. Although a lower temperature is often preferred as it reduces solvent circulation rate and prevents hydrate formation, system parameters should be thoroughly analyzed in order to quantify the effect that the lean amine will have both on processing equipment and the effectiveness of the sweetening operation. Parameters that should be evaluated when determining the optimal temperature of lean amine include sweet gas CO2 content, solvent pumping requirements, sweet gas water vapor content, and sweet gas H2S content.
Lean amine concentration also has a substantial impact on system efficiency. This is largely due to the effect that concentration has on the sweet gas profile. High amine concentration can also lead to extensive corrosion. Although lowering amine concentration serves as an effective way to protect against such conditions, improper circulation of low concentration amine can produce a number of costly issues, including excessive rich acid-gas loading and damage to the rich amine line. To prevent this, low amine concentrations typically require a higher circulation rate and/or a higher reboiler steam rate to achieve sweet gas specifications.
The corrosion risk associated with higher amine concentrations can often be managed by properly setting solvent circulation and steam rate. As with lean amine temperature, parameters that should be evaluated when determining optimal concentration include steam consumption rate, sweet gas acid content, sweet gas CO2 content, and loading requirements.