Ethane + propane

The noncondensable hydrocarbons comprise the hydrocarbons having less than five carbon atoms methane, ethane, propane and butanes encountered in production refining will add the olefins and diolefins ... 

The Reid vapor pressure is generally barely different from the true vapor pressure at 37.8°C if the light gas content —methane, ethane, propane, and butane— of the sample is small, which is usually the case with petroleum products. The differences are greater for those products containing large quantities of dissolved gases such as the crude oils shown in Table 4.13. 

Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

When gases are rich in ethane, propane, butane and heavier hydrocarbons and there is a local market for such products it may be economic to recover these condensable components. Natural gas liquids can be recovered in a number of ways, some of which have already been described in the previous section. However to maximise recovery of the individual NGL components, gas would have to be processed in a fractionation plant. 

Engstrom J R, Goodman D W and Weinberg W H 1988 Hydrogenolysis of ethane, propane, n-butane and neopentane... 

Natural gas, depending on its source, contains—besides methane as the main hydrocarbon compound (present usually at >80-90%) — some of the higher homologous alkanes (ethane, propane, butane). In wet gases the amount of C2-C5 alkanes is higher (gas liquids). 

Q-C, Natural gas, methane, ethane, propane, butane, liquefied petroleum gas... 

The lUPAC rules assign names to unbranched alkanes as shown m Table 2 2 Methane ethane propane and butane are retained for CH4 CH3CH3 CH3CH2CH3 and CH3CH2CH2CH3 respectively Thereafter the number of carbon atoms m the chain is specified by a Latin or Greek prefix preceding the suffix ane which identifies the com pound as a member of the alkane family Notice that the prefix n is not part of the lUPAC system The lUPAC name for CH3CH2CH2CH3 is butane not n butane... 

Fig. 2. Quarterly olefin feedstock prices, 1978—1991, for (D) ethane (+) propane (<)) light naphtha, and (A) naphtha.

The market value of natural gas Hquids is highly volatile and historically has been weakly related to the world price of cmde oil. During the 1980s, the market value of natural gas Hquids ranged from approximately 60% of the price of cmde to 73% (12). In this 10-year interval, several fluctuations occurred in the natural gas Hquid market. Because of the variabiHty of the natural gas Hquid market, the NGL recovery plants need to have flexibiHty. Natural gas Hquid products compete in the following markets ethane propane a Hquefted petroleum gas (LPG) a C-3/C-4 mix and / -butane all compete as petrochemical feedstocks. Propane and LPG are also used as industrial and domestic fuels, whereas 2-butane and natural gasoline, consisting of C-5 and heavier hydrocarbons, are used as refinery feedstocks. 

The most important commercial use of ethane and propane is in the production of ethylene (qv) by way of high temperature (ca 1000 K) thermal cracking. In the United States, ca 60% of the ethylene is produced by thermal cracking of ethane or ethane/propane mixtures. Large ethylene plants have been built in Saudi Arabia, Iran, and England based on ethane recovery from natural gas in these locations. Ethane cracking units have been installed in AustraHa, Qatar, Romania, and Erance, among others. 

Thermal Cracking. / -Butane is used in steam crackers as a part of the mainly ethane—propane feedstream. Roughly 0.333—0.4 kg ethylene is produced per kilogram / -butane. Primary bv-pioducts include propylene (50 57 kg/100 kg ethylene), butadiene (7-8.5 kg/100 kg), butylenes (5-20 kg/WO kg) and aromatics (6 kg/ToO kg). 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Places Ethane Propane / -Butane /-Butane Pentanes Total... 

Petroleum Gases and Naphtha. Methane is the main hydrocarbon component of petroleum gases. Lesser amounts of ethane, propane, butane, isobutane, and some 0 + light hydrocarbons also exist. Other gases such as hydrogen, carbon dioxide, hydrogen sulfide, and carbonyl sulfide are also present. 

Includes natural gas, butane, ethane, propane, waste heat, and waste gases. 

A large amount of BTX is obtained as a by-product of ethylene manufacture (see Ethylene). The amount produced strongly depends on the feed to the ethylene plant. This is illustrated in Table 3 for various feeds to a typical large scale plant producing 450,000 t/yr of ethylene (16). Note that only about 1—2% of the ethane/propane feeds end up as BTX and it is almost completely benzene and toluene. As the feed goes up in molecular weight, the yield of BTX increases from 4% with butane feed to about 10% with gas oils, and the BTX proportions go from 72 20 8 respectively, to 44 34 22 respectively. 

Fig. 1. Simplified DCPD recovery flow diagram. Number of towers varies among manufacturers. E P = ethane-propane.

Plant capacity, t/yr Ethane Propane Butane Naphtha Gas oil... 

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)... 

LNG—consisting of ethane, propane, butane, and natural gasoline (condensate)—arrives at the plant for upgrading before it is sent to petrochemical plants and refineries as feedstock. Residue gas is sold to the interstate and intrastate pipeline network. MESA, one of the world s major crude helium producers, also delivers helium to a pipeline operated by the U.S. Bureau of Mines. 

Probably the largest natural gas proeessing straddle plant in North Ameriea is BP-Amoeo s Empress, Alberta faeility. Here, EPBC (ethane, propane, butanes, and eondensate) are extraeted as liquids from natural gas before the gas is delivered to the TransCanada and Foothills (Saskatehewan) pipelines (Figure 8-5). The term straddle plant refers to the faet that the plant straddles the natural gas pipeline and extraets liquid eomponents before passing the natural gas further along the pipeline. 

One cubic foot (0.03 cu.m) of methane requires 10 cubic feet (0.28 cu.m) of air (2cu.ft (0.06 cu.m) of oxygen and 8cu.ft (0.23 cu.m) of nitrogen) for combustion. The products are carbon dioxide, nitrogen, and water. The combustion product of one cubic foot of methane yields a total of nine cubic feet of carbon dioxide gas. Also, the gas burned contains some ethane, propane, and other hydrocarbons. The yield of inert combustion gas from burning a cubic foot of methane will be 9.33 cubic feet (0.26 cu.m)... 

Propane is the next hydrocarbon in this series, and its molecular formula is CjHg which is one carbon and two hydrogen atoms different from ethane. Propane is an easily liquified gas which is used as fuel. 

The example provided in Table 2 is for a four eomponent mixture of hydroearbons (methane, ethane, propane, and n-oetane). The weighting method is a eommon ealeulation procedure that proeess engineers will encounter many times. Computations for simple systems can be easily set up on an Exeel spreadsheet. 

Paraffinic Hydrocarbons Methane Ethane Propane n-Butane 1-Butane n-Pentane n-Hexane... 

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