Natural Gas Separations

Both hollow-fiber and spiral-wound modules are used ia gas-separation appHcations. Spiral-wound modules are favored if the gas stream contains oil mist or entrained Hquids as ia vapor separation from air or natural gas separations. 

Gas separation Hollow-fibre for high-volume applications with low-flux, low-selectivity membranes in which concentration polarisation is easily controlled (nitrogen from air) Spiral-wound when fluxes are higher, feed gases more contaminated, and concentration polarisation a problem (natural gas separations, vapour permeation). 

A simplified schematic for natural gas separation is given here and consists of the following steps. 

Combining with its small size 3S installation can be used for cooling purposes in LNG technological schemes and has at least the perspective for the problem of small scale natural gas separation and liquefaction. 

Spiral-wound when fluxes are higher, feed gases more contaminated and concentration polarization a problem (natural gas separations, vapor permeation)... 

Dried CA membranes for CCL/Ch natural gas separations Separex, Cynara, Grace... 

Natural gas is usually produced from the well and transported to the gas processing plant at high pressure, in the range 500-1500 psi. To minimize recompression costs, the membrane process must remove impurities from the gas into the permeate stream, leaving the methane, ethane, and other hydrocarbons in the high-pressure residue gas. This requirement determines the type of membranes that can be used for this separation. Figure 8.30 is a graphical representation of the factors of molecular size and condensability that affect selection of membranes for natural gas separations. 

Removal of carbon dioxide is the only membrane-based natural gas separation process currently practiced on a large scale—more than 200 plants have been installed, some very large. Most were installed by Grace (now Kvaerner-GMS), Separex (UOP) and Cynara and all use cellulose acetate membranes in hollow fiber or spiral-wound module form. More recently, hollow fiber polyaramide (Medal) membranes have been introduced because of their higher selectivity. 

Membrane technology for natural-gas separations is gaining broad acceptance and a number of major membrane-separation plants have come into operation in recent years. These include the Cakerawala production platform (CKP) that processes 700 MMScfd with a 37% C02 feed and a plant in Qadirpur, Pakistan that processes 500 MMscfd of 6.5 mole% C02 feed to 2% C02 pipeline specification [26]. Current plans are being made to double production at the CKP facility [27]. 

Husain, S. (2006). Mixed Matrix Dual Layer Hollow Fiber Membranes for Natural Gas Separation, in Chemical Biomolecular Engineering, PhD Dissertation, Georgia Institute of Technology. 

Sulfur removal from natural gas Separation of MFCs (CFC substitutes)... 

Gas transport through polymers is an area of growing interest as materials with unique transport properties continue to find use in new, specialized applications ranging from extended life tennis balls (1) to natural gas separation systems (2.) Concurrent with this increased interest is the desire to understand on a molecular level what determines the gas permeability properties of a particular material. The ability to better relate polymer molecular structure to gas transport properties is crucial in any attempt to rationally design materials for specific permeability applications such as gas barriers. 

Oxygen and natural gas, separately preheated in fuel-fired heaters, are/ thoroughly premixed prior to ignitiqn by a jet burner.. The burner gas is/ quenched by water spray to 90 C and further cooled by water washing in a column. Carbon soot is partly removed at each of these stages. Final j carbon removal is by filtration through a moving bed of wet coke. Burner gas composition is shown in Table 9-1. 

Table 1 is typical of run time table which shows that in 1.50 nunutes, C3H8 and heavier components will elute from the Silicone colmtm, at 15.85 minutes valve 3 ON position, will trap O2, N2 and CH4 in the Molecular Sieve colmtm, followed by elution of CO2 and C2H6 from Porapak Q column. At 19.85 minutes valve 3 off position, O2, N2 and CH4 will be separated by Molecular Sieve column. Figure 2 is typical of a chromatogram for natural gas separation. 

The S3Tiergy between the products from FT and Natural Gas Separation plants has been proposed since the late 1940s as a sensible commercial opportunity. 

Based on the example in Section 4.6, simulate one- and three-stage natural gas separation processes in Aspen Plus. Interface the Aspen Plus simulation file with the Excel-based optimization program, and then optimize the natural gas separation for single and/or multiple objectives. 

Other membrane-based gas-separation applications that developed in the late 1980s and the 1990s include the separation of carbon dioxide from natural gas, separation of organic vapors from air and nitrogen, and dehydration of air. Table 7.3 lists the major companies involved in the industry and their principal markets. Currently, total industry sales are estimated to be about US 200 million. Of all the industrial membrane-separation processes, gas separation is... 

Separex (UOP) Cynara (Narit) > Mostly natural gas separations (US 50 million/yr)... 

The Present Current Status and Potential of the Membrane Industry 323 7.2.4.3 Natural Gas Separations... 

Cao, C., Chung, T.S., Liu, Y., Wang, R. and Pramoda, K.P. 2003. Chemical cross-linking modification of 6FDA-2,6-DAT hollow fiber membranes for natural gas separation. 

Figure 15.4 Chemical structures of two polymers investigated for use in natural gas separation membranes...

Natural gas separations are unusual in that not only is CO2 highly permeable but that CO2 and other contaminants can also plasticize the most selective polymer structures. Although cellulose acetate stmctures are sensitive to solvents and chemicals, effective pre-treatment schemes in the field can allow for stable long-term operations. 

Processing natural gas separates almost all other components from its key ingredient, methane. Processing crude oil occurs in a refinery. Because the different components of crude oil vaporize at different temperatures, they can be separated by distillation. To obtain the most desirable end products, the components are further treated through chemical processes called cracking and reforming. 

Exploratory development of dual-layer carbon-zeolite nanocomposite hollow fiber membranes with high performance for oxygen enrichment and natural gas separation. Microporous Mesoporous Mater., 113, 315-324. 

Kalikmanov, V., Betting, M., Bruining, J., and Smeulders, D. (2007) New Developments in nucleation theory and their impact on natural gas separation. SPE Armual Technical Conference 2007, 110736-PP. 

---