Gases gasoline recovery from

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. 

In processes such as the recovery of gasoline components from natural gas, where only a small fraction of the feed gas is absorbed, calculation of absorption and stripping factors is greatly simplified by assuming L Lo, V = ... 

Gas-adsorbent carbon. This is made by carbonization of coconut shells, fruit pits, coal, lignite, and wood. It must be activated, essentially a partial oxidation process, by treatment with hot air or steam. It is available in granular or pellet form and is used for recovery of solvent vapors from gas mixtures, gas masks, collection of gasoline hydrocarbons from natural gas, and the fractionation of hydrocarbon gases. It is reviviHed for reuse by evaporation of the adsorbed gas. 

The removal of hydrocarbon vapors from gas streams by absorption in liquid oils is an important part of many industrial operations. In some cases, such as natural gasoline recovery, the absorption step is but a portion of a refining process that produces several commercial products, and the gas purification aspects of the operation are of little importance. In other cases, such as the removal of aromatics from coke-oven gas, the absorption process serves to improve the value of the product gas. Processes for the removal of light oil (primarily benzene) and naphthalene from coke-oven gas are described in this section. 

The US petroleum refining industry generates sales of over 730 billion with only about 143 plants. It employs 62,000 people. About 90% of the produets used in US are fuels of whieh 43% is gasoline. Figure 13.20.1 illustrates how the produets breakdown. The proeess is described in detail in Chapter 3. Emissions of hydrocarbons to the atmosphere occur at almost every stage of the production process. Solvents are produced in various processes and they are also used to extract aromatics Irom lube oil feedstock, deasphalting of lubricating base stocks, sulfur recovery from gas stream, production of solvent additives for motor fuels such as methyl tert-butyl ether and tert-amyl methyl ether, and various... 

To enhance C3+ recovery, some units have installed presaturator drums that function as an additional absorption stage. In this operation, the cooled debutanized gasoline is mixed (presaturated) with the absorber overhead gas. The mixture is cooled and flashed in the presaturator drum. The liquid from this drum is then pumped to the top of the primary absorber. 

A test run is conducted to evaluate the performance of a 50,000 bpd (331 m /hr) FCC unit. The feed to the unit is gas oil from the vacuum unit. No recycle stream is processed however, the off-gas from the delayed coker is sent to the gas recovery section. Products from the unit are fuel gas, LPG, gasoline, LCO, and decanted oil (DO). Tables 5-2 and 5-3 contain stream flow rates, operating data, and laboratory analyses. The meter factors have been adjusted for actual operating conditions. 

Tar Sands Canadian tar sands either are strip-mined and extracted with hot water or employ steam-assisted gravity drainage (SAGD) for in situ recovery of heavy oil (bitumen). The bitumen is processed into naphtha, kerosine, and gasoline fractions (which are hydrotreated), in addition to gas (which is recovered). Current production of syncrude from Canadian tar sands is about 113,000 T/d (790,000 B/d) with expected increases to about 190,000 T/d (1.7 MB/d) by 2010. 

The recovered sulfur industry exists primarily as a result of the necessity of removing sulfur values from hydrocarbon fuels before combustion so that sulfur emissions to atmosphere are reduced. In the case of sour gas, the principal source of recovered sulfur, the product that results from recovery of the sulfur is clean-burning, non-polluting methane. In the case of refineries handling high sulfur crude the product is low sulfur gasoline and oils. Thus every ton of sulfur recovered is a ton that is not added to the atmosphere. The recovery process itself however, is also the subject of optimization and recent developments in recovery efficiency have further ensured that the environmental impact in the immediate vicinity of these desulfurization facilities will be minimized. 

Vapor Phase Absorption. Absorption is closely related to extractive distillation, in that a solvent is used for the separation of one or more constituents from a gaseous mixture. In absorption, however, the mixture to be treated is comprised of compounds having relatively large differences in volatility and condensation cannot be conveniently used. The various absorption processes differ primarily in the means used to separate product and absorber oil. A typical example of the application of vapor phase absorption in the petroleum industry is the recovery of gasoline from natural gas. 

Methane reforming units receive methane-rich gas from a cryogenic product recovery facility and subject the gas to partial oxidation. Some of the carbon dioxide content is removed and the gas recycled to the reactors. Once liquids are recovered, the stream goes to essentially conventional refining units. The plant s production is primarily transport fuels. Most of the gasoline production is currently sold to other refineries for blending with their stocks, but a portion of the product is marketed directly to consumers. 

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