CO2 Removal from Natural Gas

Recovery of CO2 in the oil and gas production is of major importance to promote enhanced oil recovery (FOR) from depleted fields High pressure CO2 is then pumped back into the reservoir at the periphery of the field and diffuses through the formation to drive residual oil toward the wells. The recycled gas generally needs to have a purity of at least 95 vol% CO2. 

The main companies producing membranes for CO2 removal are listed in Table 4.6. 

FI GU RE 4.25 Picture from Qadirpur, Pakistan, the world s largest membrane-based natural gas processing plant. (From Dortmund D., Doshi K., Recent developments in CO2 removal membrane technology http /www.uop.com/gasprocessing/TechPapers/C02RemovaIMembrane.pdf (accessed March 2004). With permission.) 

Some examples of installed membrane units for gas processing are given below  

One of the earliest (and largest) membrane plants for FOR was at the SACROC unit in West Texas, which started up in 1984. (The hollow Hber membrane units are owned and operated by Cynara, a subsidiary of Dow.) In this process, the purified CO2 stream from the membranes is further treated with hot potassium carbonate before reinjection into the oil field. A single-membrane stage is used followed by multiple banks of membrane permeators in parallel, thus plant performance can be optimized under varying feed conditions by adjusting the number of permeators in operation. (Over tbe years tbe CO2 content increased from 0.5 vol% up to a level of -60 vol%.) The Cynara membrane system would successfully process 70 million SCFD of gas containing 40-70 vol% CO2 around 1990 [122]. 

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UOP Separex membrane comprising cellulose acetate (CA) polymer has been extensively used for CO2 removal from natural gas and currently holds the membrane market leadership for this appUcation. The UOP Polysep membrane, a polymeric membrane, has been successfully applied to H2 separation processes. 

ZeoHte/polymer mixed-matrix membranes have been studied for a number of gas separations such as separation of N2 from air [37, 73, 75, 81, 84, 85], H2 and CO2 removal from natural gas [51, 54, 69, 81, 86-88], CO2 removal from N2 [74], n-pentane/i-pentane separation ]89] and separation of H2 from CO2 [65]. But a majority of the mixed-matrix membranes that have been evaluated for gas separations are mixed-matrix dense films. 

Industrial gases Hz, N2, O2, Ar, He, CO2, natural gas Sweetening and CO2 removal from natural gas, removal of hydrocarbons from air, preparation of protective gases Aromatic compounds... 

Na Na 2 (A102) 2(Si02) 2l 8-ring (obstructed) 3.8 Desiccant. CO2 removal from natural gas... 

Permeable gas separation membranes utilize differences in solubility and diffusion of different gas components in polymer materials. In recent years membrane-based technologies have gained increasing importance in gas processing. Typical applications are CO2 removal from natural gas or hydrogen recovery from synthesis gas. The degree of selectivity between different gas components depends on the membrane used so that it is necessary to contact the manufacturers for a concrete project. Membrane separation units are usually supplied skid mounted. 

Figure 4.8 Process flow diagram of two-stage membrane separation for CO2 removal from natural gas stream data correspond to the optimal solution ( / in Figure 4.9.

Peters, L., Hussain, A., Folhnann, M., et al. (2011) CO2 removal from natural gas by employing amine absorption and membrane technology - a technical and economical analysis. Chemical... 

Liu H, Cooper VR, Dai S, Jiang D (2012) Windowed carbon nanotubes for efficient CO2 removal from natural gas. J Phys Chem Lett 3 3343-3347... 

C. Anderson, A. Siahaan, Membrane CO2 Removal from natural gas, Grissik gas plant Sumatra, Indonesia Proceedings of the Laurance Reid gas conditioning conference, (2006) 71-84. 

Y. Xiao, B. T. Low, S. S. Hosseini, T. S. Chung, The strategies of molecular architecture and modification of polyimide-based membranes for CO2 removal from natural gas - a review. Prog. Polym. Sci., 34, 561-580 (2009). 

Environmental exposure may occur from emission to aquatic compartment from wastewater and evaporative emissions associated with its use in the perfume and cosmetic industries and its use as a solvent and CO2 remover from natural gas, and disposal of consumer products containing triacetiiL... 

In the separation of supercritical gases such as air separation, CO2 removal from natural gas, and hydrogen recovery from a variety of chemical and petrochemical processes, the smaller penetrant molecules (O2, CO2 and H2, respectively) are the more permeable penetrants, and membrane materials research focuses on developing materials with high diffusivity and high diffusivity selectivity (57). For such... 

Further, these polymeric fillers are reducing the hydrocarbon fouling problem of PI membranes. Gas separation experiments show a dramatically enhanced gas separation performance for CO2 removal from natural gas. 

Zeolites a variety of crystalline silicates with pore diameters between 0.3 and 1 nm dehydration of gases, dehydration of liquids (e.g. alcohol), n-paraffins from iso-paraffins, CO2 removal from natural gas, desulfurization of natural gas and other streams, fructose/glucose separation, sulfur compounds from organics, N2/O2 separation very widely used... 

The Selexol process has found a very wide range of applications. It was originally used to remove CO2 from an ammonia plant in Nebraska, followed soon after by H2S and CO2 removal from natural gas in the U.S. and in Europe. Other applications include desulfurization and CO2 removal from synthesis gas derived from the partial oxidation of heavy petroleum stocks and from coal gasification. Natural gas treating applications include several, where in addition to production of pipeline specification gas, a relatively pure stream of carbon dioxide is produced for reinjection into oil formations, so-called enhanced oil recovery or EOR. A relatively new use for the process dating back to 1979 is the purification of landfill gas drawn from the biological degradation of municipal waste in sanitary landfills. This application is characterized by the occurrence of chlorinated and aromatic hydrocarbons as impurities in the landfill gas. 

Union Carbide reported that as of 1992, a total of S3 Selexol plants had been installed. These comprise 10 for CO2 removal from various synthesis gases, 12 for CO2 removal from natural gas, 15 for selective H2S removal (with or without CO2 removal), 8 for desulfurization of synthesis gas, and 8 for landfill gas purification (Epps. 1992A). 

Carbon-dioxide-selective separation is becoming an important issue in areas such as petrochemical engineering (e.g., CO2 removal from natural gas), environment (e.g., CO2 removal from flue gas), agriculmre (e.g., control of CO2 concentration), and other related industries. Membranes can selectively separate CO2 from industrial processes. 

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