2025 Conference Workshop
CO2 removal using amine units is a common pre-treatment requirement upstream of Cryogenic NGL recovery plants. Typically, the maximum allowable CO2 in the Cryo unit feed is dictated by the CO2 specifications in the residue gas (export gas) from the Cryo plant and by the CO2 specs in the export NGL. If these specifications do not dictate the CO2 limit in the feed, CO2 freezing in the demethanizer column will determine the maximum allowable feed gas CO2 content. Factors such as operating pressure of the demethanizer column, the amount of heavier hydrocarbons in the gas (GPM of C2+), and the extent of ethane recovery in the cryo plant, further impact the CO2 freezing in the column.
Changes in the reservoir production behavior in an existing operating Cryo plant such as increased CO2 content in the feed can often become bottlenecks for the cryo plants, especially when higher ethane recoveries are desired. One obvious solution to handle the increased CO2 in the feed gas scenario is to add extra amine treatment capacity in the gas pretreatment section to remove the excess CO2. However, this option requires significant capital investment.
Because of the similar volatility of CO2 and ethane, majority of CO2 tend to stay with the ethane product. This paper will discuss an alternative debottlenecking scenario where the overhead from the deethanizer column can be processed in a hollow-fiber Cellulose Triacetate (CTA) membrane unit to reduce the CO2 content in the export ethane product. Alternatively, if a separate distillation column is used for the separation of CO2 and ethane, membranes can be used to break the ethane-CO2 azeotrope for higher CO2 recovery. CTA hollow fiber membranes have been extensively used in the oil and gas industry for separating CO2 from natural gas, but not much work has been done for separating CO2 from ethane. Test results for the ethane CO2 separation will be presented. The larger molecular size of ethane compared to methane provides much higher selectivities for CO2-C2 separation compared to CO2-C1 separation. High ethane selectivities of membranes results in high ethane recoveries. Implementing a membrane unit to handle the increased CO2 content in the feed gas offers attractive option for operators. This presentation will discuss a case study demonstrating the advantages of a membrane-based Cryogenic unit for separating CO2 from ethane.
Talk to us about our Advertising options. We publish our bi-annual magazine and send out regular newsletters too.
Our conferences provide a direct marketing channel to Directors and Process Engineers within the natural gas processing industry. You can meet and engage with around 100-member companies, all in one place. Click here to view our Sponsorship Opportunities.
