Energy Savings of Amine Sweetening Process through Lean and Rich Vapor Compression Approaches

The natural gas demand for energy production has increased in the last decades and is forecasted to further increase in the future. According to IEA energy outlook report 2008, approximately 40% of proven natural gas reserves are acidic (i.e. contains H₂S and CO₂). Hence, the need to capture associated contaminants of acidic gases to meet health, environmental, integrity and product specifications with affordable techniques will continue to be a challenge. Amine sweetening process is considered as one of the most acid gas removal techniques being used around the world due to its flexible operation, high removal efficiency and its design maturity. However, energy requirement around amine process has been always an area of a concern for all new and existing units. The top energy consumer is the regenerator re-boiler. Optimization of energy requirement around Amine plant becomes an important exercise for most operating companies to minimize its expenditures either during design stage or operation stage and achieve carbon emission target.

The aim of this study is to examine the effectiveness of two debottlenecking approaches namely Lean Vapor Compression (LVC) and Rich Vapor Compression (RVC) to minimize energy consumption around Amine units. These two approaches are considered to be the most promising in reducing the reboiler duty. These debottlenecking approaches involve modification of standard conventional process flow scheme with modified process flow scheme to enhance heat integration and regeneration efficiencies.

The two approaches have been applied on two different amine sweetening units in Sultanate of Oman with MDEA and MDEA-PZ solvents. ProMax process simulation software has been utilized to perform advanced thermodynamics model which has been initially validated by real field data.

Unlike most of published studies, the study has been conducted using models validated by real field data including different solvents and operating conditions as a base case. Additionally, the study focuses in pre-combustion amine based CO₂ and H₂S capture processes. By applying the Lean Vapor Compression approach, 40-50% reduction in re-boiler duty was achieved. For Rich Vapor Compression approach, saving of 10-11% has been achieved with considerable changes in amine circulation rate and stripper operating pressure.