Hydrocarbon absorption and stripping

Edmister, W. C., Hydrocarbon Absorption and Fractionar tion Process Design Methods, Pet. Engr. May 1947-March 1949 and, Absorption and Stripping—Factor Functions for Distillation Calculations by Manual and Digital—Computer Methods. A.I.ChJE. foumal, V. 3, No. 2 p. 165 (1957). 

Kremser-Brown-Sherwood Method — No Heat of Absorption, 108 Absorption — Determine Component Absorption in Fixed Tray Tower, 108 Absorption — Determine Number of Trays for Specified Product Absorption, 109 Stripping — Determine Theoretical Trays and Stripping or Gas Rate for a Component Recovery, 110 Stripping — Determine Stripping-Medium Rate for Fixed Recovery, 111 Absorption — Edmlster Method, 112 Example 8-33 Absorption of Hydrocarbons with Lean Oil, 114 Inter-cooling for Absorbers, 116 Absorption and Stripping Efficiency, 118 Example 8-34 Determine Number of Trays for Specified Product Absorption, 118 Example 8-35 Determine Component Absorption in Fixed-Tray Tower, 119 Nomenclature for Part 2, 121... 

Tray efficiencies for distillation of light hydrocarbons and aqueous solutions are 60-90% for gas absorption and stripping, 10-20%. 

CHEMCALC 11. AMSIM Amine Gas Tiealing Pbnt Simulator Gulf Publishing Company, Book Division P.O. Box 2608 Houston, TX 77252 (713) 520-4444 Models processes for absorption and stripping of H2S and CO2 in a gas stream. For hydrocarbon gases, also calculates hydrocarbons absoibed and stripped. 

There are a number of sources for phase equilibrium data and computational methods (see E4.1, below). Most of the material focuses on vapor-liquid equilibrium (VLB) since this information is used extensively for distillation, absorption, and stripping. The most complete VLB literature is a series of books by Hala et al. (1967, 1968). Additional information can be found in Hirata et al. (1975) and Gmehling et al. (1979). For light hydrocarbon systems, the Natural Gas Processors Association has published a data book (1972). A very useful and extensive source, including solid-liquid and liquid-liquid as well as VLB information, has been written by Walas (1985). This book contains both source data and methodology and contains sample calculations. 

The phase separation of certain mixtures may take place at economically impractical temperatures and pressures. An example of this type of separation might be the recovery of light hydrocarbon gases dispersed in air. In these situations, a second stream may be added to the mixture to shift the vapor-liquid equilibrium region. Such a process is equivalent to a single-stage absorption or stripping device. 

The basic Solinox process employs a typical absorption/desorption cycle with SO2 removed from the feed gas in a countercurrent absorber, and stripped from the physical solvent in a countercurrent reboiled stripper. In practice, the process is complicated somewhat by the need to water wash the feed gas before it is contacted with solvent to reduce the gas temperature and remove dust and some impurities and the need to water wash both the purified gas and the stripper off-gas to recover entrained or vaporized solvent. A distinctive feature of the process is its ability to remove hydrocarbons, such as benzene, which are present in some vent gas streams and may require removal to meet air pollution control requirements. Hydrocarbons are generally quite soluble in the solvent. They are absorbed and stripped with the SO2. The hydrocarbons can be removed from the SO2 byproduct by a fractionation step or can be destroyed by oxidation during subsequent processing. 

Elemental sulfur also is recovered as a by-product in processing natural gas and petroleum. Refining operations of natural gas and petroleum crude produce hydrogen sulfide, which also may occur naturally. Hydrogen sulfide is separated from hydrocarbon gases by absorption in an aqueous solution of alkaline solvent such as monoethanol amine. Hydrogen sulfide is concentrated in this solvent and gas is stripped out and oxidized by air at high temperature in the presence of a catalyst (Claus process). 

As the natural gas industry developed and expanded, so did the demand for liquids recovered from natural gas. One way of recovering additional liquids is through the use of a heavy absorption oil that has good solubility characteristics for the propane and heavier hydrocarbon components in the gas stream. As in the case of dehydration, the solvent must be regenerated. Figure 20.1311 shows the absorption-stripping section of an absorption-type hydrocarbon liquids recovery facility. The absorbent is circulated to the top of the absorber and flows downward, absorbing liquefiable components from the... 

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