Separation of Multiphase, Multicomponent Systems || Absorption Extraction of Heavy Hydrocarbons and Water Vapor from Natural Gas
✍ Scribed by Sinaiski, Emmanuil G.; Lapiga, Eugeniy J.
- Publisher
- Wiley-VCH Verlag GmbH & Co. KGaA
- Year
- 2007
- Weight
- 276 KB
- Category
- Article
- ISBN
- 3527406123
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✦ Synopsis
Absorption Extraction of Heavy Hydrocarbons and Water Vapor from Natural Gas
One of the methods of extracting water vapor and hydrocarbons (which form a gas condensate) from natural gas is by absorption. Liquid absorbent is injected into the gas flow that enters the field equipment devices designed for physical processing of hydrocarbon raw material. In Section 2.2, we studied the devices and technologies that are used in absorption extraction of heavy hydrocarbons from gas, and in gas dewatering. It was mentioned that two radically different methods exist: input of the absorbent directly into the gas flow under the concurrent flow condition (gas and absorbent move in the same direction); and input of the absorbent against the gas flow (countercurrent flow condition). The first method is realized when the absorbent is injection directly into the gas-transporting pipeline (this method is called the intratube absorption), or into the contact section of a direct-flow spray absorber. The second method is realized in vertical plate absorbers, where gas enters the bottom part of the device, and absorbent is delivered into the top part and then flows down successively from one contact plate to another. In the latter case, at each plate both concurrent and countercurrent flows are possible -depending on the design of contact plates.
In the process of extraction of heavy hydrocarbons, a liquid saturated with heavy hydrocarbons can be taken as the absorbent, for example, petroleum, solar or transformer oil, weathered condensate etc. For the absorption dehydration of gas, glycols are used: diethylene glycol (DEG) or triethylene glycol (TEG).
Consider successively the calculation of absorption processes for intratube absorption, in concurrent spray absorbers, and, finally, in countercurrent plate absorbers.
20.1 Concurrent Absorption of Heavy Hydrocarbons
An absorbent is introduced in the form of fine drops into the flow of a multicomponent gas mixture moving in a pipe of constant cross section. Let us suppose that all drops have the same radius R, and the composition of the liquid phase is given either by mass concentrations of components r i0 (kg/m 3 ), or by their molar fractions x i0 . Pressure p and temperature T of gas in the pipe are given, and they 635