Natural ethane separation

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. 

Condensable hydrocarbons are removed from natural gas by cooling the gas to a low temperature and then by washing it with a cold hydrocarbon hquid to absorb the condensables. The uncondensed gas (mainly methane with a small amount of ethane) is classified as natural gas. The condensable hydrocarbons (ethane and heavier hydrocarbons) are stripped from the solvent and are separated into two streams. The heavier stream, which largely contains propane with some ethane and butane, can be Hquefied and is marketed as Hquefied petroleum gas (LPG) (qv). The heavier fractions, which consist of and heavier hydrocarbons, are added to gasoline to control volatihty (see Gasoline and other motor fuels). 

Helium and Natural-Gas Systems Separation Helium is produced primarily by separation of hehum-rich natural gas. The hemim content of the natural gas from plants operated by the U.S. Bureau of Mines normally has varied from 1 to 2 percent while the nitrogen content of the natural gas has varied from 12 to 80 percent. The remainder of the natural gas is methane, ethane, and heavier hydrocarbons. 

The liquid collected at the bottom of the demethanizer tower is a mixture of ethane, propane, butane, and condensate (EPBC), which is taken off in a stream and pumped—as a liquid, at 1,000 psig—to a customer facility. Another part of the EPBC is introduced into a deethanizer tower. The stream of EPBC liquid entering the deethanizer tower is further separated into PBC liquid and pumped to the El Paso Natural Gas facility in Gallup, New Mexico. EP (ethane and propane)... 

The first step in a gas processing plant is to separate the components that are to be recovered from the gas into an NGL stream. It may then be desirable to fractionate the NGL stream into various liquefied petroleum gas (LPG) components of ethane, propane, iso-butane, or normal-butane. The LPG products are defined by their vapor pressure and must meet certain criteria as shown in Table 9-1. The unfractionated natural gas liquids product (NGL) is defined by the properties in Table 9-2. NGL is made up principally of pentanes and heavier hydrocarbons although it may contain some butanes and very small amounts of propane. It cannot contain heavy components that boil at more than 375°F. 

Higher molecular weight hydrocarbons present in natural gases are important fuels as well as chemical feedstocks and are normally recovered as natural gas liquids. For example, ethane may be separated for use as a feedstock for steam cracking for the production of ethylene. Propane and butane are recovered from natural gas and sold as liquefied petroleum gas (LPG). Before natural gas is used it must be processed or treated to remove the impurities and to recover the heavier hydrocarbons (heavier than methane). The 1998 U.S. gas consumption was approximately 22.5 trillion ft. ... 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

British Foreign Minister Ernest Bevin once said that "The Kingdom of Heaven runs on righteousness, but the Kingdom of Earth tuns on alkanes." Well, actually he said "tuns on oil" not "runs on alkanes," but they re essentially the same. By far, the major sources of alkanes are the world s natural gas and petroleum deposits. Laid down eons ago, these deposits are thought to be derived from the decomposition of plant and animal matter, primarily of marine origin. Natural gas consists chiefly of methane but also contains ethane, propane, and butane. Petroleum is a complex mixture of hydrocarbons that must be separated into fractions and then further refined before it can be used. 

About half the propane produced annually in the U.S. is used as a domestic and industrial fuel. When it is used as a fuel, propane is not separated from the related compounds, butane, ethane, and propylene. Butane, with boiling point -0.5 °C (31.1 °F), however, reduces somewhat the rate of evaporation of the liquid mixture. Propane forms a solid hydrate at low temperatures, and this causes great inconvenience when a blockage occurs in a natural-gas line. Propane is used also as so-called bottled gas, as a motor fuel, as a refrigerant, as a low-temperature solvent, and as a source of propylene and ethylene. 

Natural Gas Liquids (NGL) - The portions of natural gas that are liquefied at the surface in production separators, field facilities, or gas processing plants, leaving dry natural gas. They include but are not limited to ethane, propane, butane, natural gasoline, and condensate. 

It is important to keep in mind that any extraction of organic matter from soil will include both naturally occurring organic matter and organic contaminants. Separating the two at some later stage of analysis is thus an essential analytical step. For example, extraction of soil with hexane or dichloromethane will extract both l,l,l-trichloro-2,2-di(4-dicholorphenyl)ethane (DDT), a contaminant, and octadecanoic acid, a natural fatty acid. Also, the herbicide 2,4-dichlorophenoxy acetic acid, a contaminant, and indole-3-acetic acid, a natural plant hormone, are both extracted by water (see Figure 12.3). These... 

Separation of pure methane and ethane from natural gas... 

HYPERSORPTION. Process in w-hiclt activated car lion selectively absorbs the less-volatile components from a gaseous mix. while the more-volatile components pass on unaffected. Particularly applicable to separations of low-boiling mixtures such as hydrogen and methane, ethane from natural gas, ethylene from refinery gas, etc. 

Propane is a colorless, easily liquefied, gaseous hydrocarbon, the third member of the paraffin series following methane and ethane. The chemical formula for propane is CH3CH2CPI3. It is separated in large quantities from natural gas,... 

Natural gas (predominantly methane, CH4, with ethane, propane, and butane) is a fuel gas, and it is also an important chemical raw material for various syntheses. Natural gas can also be separated into its hydrocarbon constituents thereby producing feedstocks for petrochemical processes. 

In GC this process has been used to separate fixed gases such as hydrogen, oxygen, nitrogen, methane, carbon monoxide, ethane, carbon dioxide, and ethylene5 and it has been called molecular sieve chromatography. The sieves are natural zeolites or synthetic materials of which the alkali metal aluminosilicates are typical. Table 3 lists the pore sizes of some commercial sieves. Newer sieves have been especially prepared from carbon Figure 3.5 shows a separation on a typical one, carbosieve II-S. 

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