Drying Up: The Art of Glycol Dehydration in FPSO operation

On board of the Floating Production Storage and Offloading (FPSO) units the dehydration of hydrocarbons plays a crucial role in offshore oil and gas operations. One of the key processes employed in these units is glycol dehydration, which effectively removes water and other impurities from natural gas. This process not only enhances the quality of the gas but also prevents the formation of hydrates and corrosion in pipelines. By utilizing glycol as a dehydrating agent, FPSOs can ensure the efficient and safe transportation of hydrocarbons, making it an essential component of modern offshore production strategies. This article will provide a brief explanation about how the dehydration of hydrocarbons performed and its technical challenges as part of FPSO operation.

Glycol dehydration is a well-established method, known for its reliability and efficiency in removing water from natural gas. The primary goal of glycol dehydration is to remove water from natural gas. Normally the system is designed to maintain specific moisture content levels in the gas, typically not exceeding 7 lbs/MMscf. Excess moisture can lead to hydrate formation, corrosion, and operational issues in pipelines and processing equipment. Glycol dehydration installation helps prevent operational issues mentioned before and ensuring smoother downstream processing. In general, the process inside the Glycol dehydration system can be summarize as below,

·?????? Wet Gas Inlet: The process begins with wet natural gas entering the system, typically through a filter to remove free liquids and solids.

·?????? Absorber Column: The wet gas is then fed into an absorber (glycol contactor) where it meets lean glycol (usually TEG - triethylene glycol). The glycol absorbs water vapor from the gas through physical absorption.

·?????? Contacting Mechanism: This absorption occurs on trays or structured packing within the column, maximizing the surface area for interaction between the gas and glycol.

·?????? Regeneration: After the glycol absorbs water, it becomes “rich” glycol. This rich glycol is then heated in a reboiler to drive off the absorbed water, regenerating it back to lean glycol. The regenerated glycol is cooled and recycled back to the absorber for reuse.

Here are some key technical challenges associated with the glycol dehydration process:

?? Foaming: Excessive foaming in the contactor can lead to significant glycol losses and reduced efficiency. This often results from contaminants in the gas stream.

?? Fouling: Reboilers and heat exchangers can become fouled, which decreases heat transfer efficiency and increases operational costs.

?? Tray Plugging: The presence of solid contaminants can cause tray plugging in the contactor, disrupting the flow and reducing the system’s effectiveness.

?? Glycol Loss: Loss of glycol due to various factors, including leaks or excessive carryover, can disrupt the dehydration process and lead to increased operational costs.

?? Thermodynamic Challenges: Water’s non-ideal behavior complicates the modeling of vapor-liquid equilibrium, especially in high-acid gas streams, making it difficult to optimize the process.

?? High CO2 Content: High levels of carbon dioxide in the feed can affect the glycol’s ability to absorb water, requiring adjustments in operating conditions.

?? Environmental Concerns: Managing emissions of volatile organic compounds (VOCs) and other pollutants during the regeneration process is increasingly important for compliance with environmental regulations.

On top of the technical challenges above, specific constraint related to FPSO installation like space limitation, weight constraints, maintenance access and alignment with FPSO compression system are required to be considered during the design development.

In conclusion, the FPSO glycol regeneration system plays a crucial role in ensuring the efficient removal of water from hydrocarbon streams, thereby enhancing the overall productivity and reliability of offshore operations. By optimizing glycol recovery and minimizing environmental impact, these systems not only contribute to operational efficiency but also align with sustainability goals in the oil and gas industry. As technology continues to advance, the integration of innovative solutions will further improve the performance and resilience of glycol regeneration processes, paving the way for a more sustainable future in offshore production.