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Problem: Carbon dioxide is a common impurity in natural gas which must be removed to improve the heating value of the gas or to meet pipeline specifications. (back to top) Solution: PRISM® membranes can be used as a gas scrubber for natural gas. PRISM membranes, based on simple process designs, lower costs, and the other benefits listed below, provide an attractive alternative to traditional amine systems.  PRISM membranes can also be used as a bulk-removal device to minimize the size of an amine system.  The benefits become even more pronounced as the industry produces natural gas from very remote locations. (back to top) Benefits: Ideal for remote locations with limited utilities. Flexibility to explore process flow sheets with various product gas compositions. No moving parts mean minimal maintenance costs. No additional hazardous chemicals, like amines, to cause environmental complications. Lightweight and compact. Easy to install and operate. (back to top) Examples: This small CO2 removal system was engineered and built by Petreco.  It incorporates the latest PRISM membrane technology and is designed to remove CO2 from natural gas.  Its capacity is 8 MMSCFD, and it is designed to reduce the CO2 level from 4.5% to less than 2%. It was commissioned in July 2004.   Recovery of CO2 from associated gas in enhance oil recovery (EOR) programs. Acid gas removal from natural gas. (back to top) Performance: The following figure demonstrates general trends. Contact us to discuss performance in your specific application and for assistance in sizing equipment. (back to top) Related Publications: Stookey, D.J. and W.M. Pope, "Application of Membranes in Separation of Carbon Dioxide from Gases," Recovering Carbon Dioxide from Man-Made Sources, Argonne National Laboratory, Oct 1985, ANL/CNSV-TM-166, pp. 53–62. Stookey, D.J., C.J. Patton, and G.L. Malcolm, "Membranes Separate Gases Selectively," CEP, Nov. 1986, pp. 36–40. (back to top) Frequently Asked Questions: How can I determine if Prism membranes will provide the separation I need? Prism membranes will effectively separate carbon dioxide from hydrocarbon vapors. Performance is highly depended on CO2 content in the raw feed gas, CO2 specification in product, supply pressure, permeate pressure, and operating temperature. To accurately determine the separation and membrane size for your specific application Air Products uses a proprietary computer model to provide you with a complete heat and material balance. What are the operating limits of the membrane? The membrane can operate over a wide range of pressures and temperatures. Temperatures up to 195°F (90°C) and differential pressures over 1000 psi are typical. The maximum absolute feed pressure is limited only by the mechanical design pressure of the ANSI flanges on the pressure vessel. What pre-conditioning of the feed gas is required? Several factors determine the required pretreatment. A filter coalescer or mist eliminator vessel with a high efficiency coalescing element is required to remove entrained liquid in the feed gas. A feed heater is required to superheat the gas and maintain constant operating temperature and constant membrane performance. A mist eliminator and heater are sufficient pretreatment in many cases. If other contaminants may be present such as methanol, amines, very high molecular weight or waxy hydrocarbons, or corrosion inhibitors, Air Products should be consulted for other pretreatment recommendations. Particulate filtration of the feed gas is not required. The shell-side fed Prism membranes have sufficient open flow area to prevent plugging from rust, pipe scale, and other particulates typically found in natural gas streams. However, a temporary conical strainer is recommended during the commissioning period to remove any weld slag or excessive amounts of debris which may be in new piping. What process controls and instrumentation are required? Air Products will provide a standard Piping and Instrumentation Diagram (P&ID) showing recommended control systems and instruments on the membrane and pretreatment equipment. Air Products will review and approve customized control systems with the system packager to provide any special control requirements. What is the life of the membrane? With proper operation and maintenance the membrane should last for the life of the project. If replacement becomes necessary usually due to fouling with contaminants, the membrane internal module can be easily replaced. Does Air Products provide complete membrane systems? Air Products provides membranes to the oil and gas industry through OEM partners. The OEM partner designs and constructs the complete skid-mounted package including pretreatment equipment, membrane housings, piping, valving, instrumentation, and control systems. Air Products works closely with our OEM partner to deliver a quality system that meets the requirements of the application. Is the Prism membrane warranted? Air Products provides a standard warranty for performance one year from start-up or eighteen months from purchase date, provided the membrane and pretreatment equipment have been properly operated and maintained. (back to top)