CYNARA acid gas removal membrane systems efficiently and selectively permeate acid gases to separate them from produced gas streams that contain 5- to 95-mol% acid gas.
These systems are ideal for stand-alone bulk acid gas removal and the treatment of produced gas to meet pipeline transmission and natural gas heating specifications. They can provide permeate streams of more than 95% pure CO2 for enhanced oil recovery (EOR) injection applications. Used in a hybrid acid gas treatment train, they provide bulk separation of produced gas streams that are subsequently treated by an amine system or other separation technologies.
The compact footprint of the membrane systems and their largely self-contained functionality make them well suited for offshore applications. There are no moving parts or chemical requirements because the systems work on the principle of diffusion and solubility-based separation.
In addition to eliminating the weight of liquid chemicals and the need for liquid recirculation equipment and associated maintenance, CYNARA systems eliminate the logistics associated with the transportation and storage of liquid amine chemicals onshore and offshore. The need to superheat gas streams containing >40% CO2 and related costs are also minimized because the membranes can efficiently handle condensing hydrocarbons.
Three membrane-based acid gas removal options are available.
CYNARA systems use tubular membrane elements that consist of a central steel tube surrounded by a sheet of asymmetric, hollow fibers made from cellulose triacetate polymer. Millions of these hollow fibers are combined to make a single element, which is housed in a case.
As the inlet natural gas stream is drawn through the membrane, small molecules such as CO2 and H2S in the gas stream permeate into the fibers much faster than the larger, more complex natural gas components (e.g., methane and higher hydrocarbons). The smaller molecules flow around the fibers into the central core. A low-pressure CO2-rich stream flows through the tube sheets and exits the element at both ends. The high-pressure natural gas product stream, with the bulk of the acid gas removed, exits through the core steel tube.