Technical paper
An Evaluation of General "Rules of Thumb" in Amine Sweetening Unit Design and Operation
Many "rules of thumb" are widely used in the design and operation of amine sweetening units. These rules have been developed over the years and most engineers accept them even though many have little familiarity with how important they may or may not be. Few ask why we have these rules, how absolute they are, and whether the rules have any flexibility. In this paper, several of these rules are described and evaluated for their usefulness and necessity using parametric studies with a steady-state process simulator. The rules evaluated include the 5 C temperature approach in the absorber, the 0.12 kg/L specification for reboiler steam, the 99C lean/rich exchanger outlet temperature, and the regenerator pressure/reboiler temperature guideline. Although these four rules of thumb are excellent starting points, none of them represent optimum conditions for all cases and, depending on the situation, violating these rules could offer considerable advantages to process efficiency. Every situation is different and requires a thorough investigation as to whether changes to these set points are beneficial and whether these benefits offset any additional risks.
Many “rules of thumb” are widely used in the design and operation of amine sweetening units. These rules have been developed over the years and most engineers accept them even though many have little familiarity with how important they may or may not be. Few ask why we have these rules, how absolute they are, and whether the rules have any flexibility. In this paper, several of these rules are described and evaluated for their usefulness and necessity using parametric studies with a steady-state process simulator. The rules evaluated include the 5 C temperature approach in the absorber, the 0.12 kg/L specification for reboiler steam, the 99C lean/rich exchanger outlet temperature, and the regenerator pressure/reboiler temperature guideline. Although these four rules of thumb are excellent starting points, none of them represent optimum conditions for all cases and, depending on the situation, violating these rules could offer considerable advantages to process efficiency. Every situation is different and requires a thorough investigation as to whether changes to these set points are beneficial and whether these benefits offset any additional risks.