Adsorption recovery efficiency

The effect of temperature, pressure, and oil composition on oil recovery efficiency have all been the subjects of intensive study (241). Surfactant propagation is a critical factor in determining the EOR process economics (242). Surfactant retention owing to partitioning into residual cmde oil can be significant compared to adsorption and reduce surfactant propagation rate appreciably (243). 

Adsorption of organic compounds on materials such as Tenax is best done on an individual species basis in which the collection and recovery efficiencies are established and blank analyses show no interferences from the adsorbent material. 

Brodtmann [120] carried out a long-term study on the qualitative recovery efficiency of the carbon adsorption method versus that of a continuous liquid-liquid extraction method for several chlorinated insecticides. Comparative results obtained by electron capture gas chromatography indicate that the latter method may be more efficient. 

As stated above, when present in high concentration, e.g. exhaust gas from adipic acid plants, N20 can be valorized as a strong oxidant. The direct oxidation of benzene to phenol was thus demonstrated at 673 K with 97-98% phenol yield from benzene and 85% from N20 on a Fe-MFI catalyst (29). Due to potential interest in selective oxidation processes using N20, several incentives entail recovering N20 from HN03 tail gas (N20 < 1%). Several variously exchanged zeolites have been tested for the adsorption/recovery of N20 (24). Ba-MFI is the most efficient for N20 adsorption at ca. 323 K and desorption at 423-473 K with 90% N20 removal from the flue gas. 

When a surfactant-water or surfactant-brine mixture is carefully contacted with oil in the absence of flow, bulk diffusion and, in some cases, adsorption-desorption or phase transformation kinetics dictate the way in which the equilibrium state is approached and the time required to reach it. Nonequilibrium behavior in such systems is of interest in connection with certain enhanced oil recovery processes where surfactant-brine mixtures are injected into underground formations to diplace globules of oil trapped in the porous rock structure. Indications exist that recovery efficiency can be affected by the extent of equilibration between phases and by the type of nonequilibrium phenomena which occur (J ). In detergency also, the rate and manner of oily soil removal by solubilization and "complexing" or "emulsification" mechanisms are controlled by diffusion and phase transformation kinetics (2-2). 

Table II. Estimate of Recovery Efficiency of Lower-Molecular-Weight Hydrocarbons by Adsorption on XAD-2 Resins...

PH Krumkine, JS Falcone, TC Campbell. Surfactant flooding. 1 The effect of alkaline additives on interfacial tension, swfactant adsorption, and recovery efficiency. Soc Petrol Eng J 22 503, 1982. 

Alkaline inorganic chemicals such as sodium silicates, sodium hydroxides, sodium carbonate, and sodium phosphates have been added to injection fluids used in enhanced oil recovery systems. These chemicals can, in varying degrees, affect various rock and fluid parameters such as interfacial tension, interfacial viscosity, emulsion stability, rock wettability, hardness-ion content, ion-exchange capacity or equilibria, surfactant adsorption, phase equilibria, etc., in order to improve recovery efficiency for residual oil remaining after waterflooding. 

According to Browning (1952), the overall recovery efficiency of such systems is usually between 80 and 95%, depending primarily upon the effectiveness of the design of the hoods and vapor-collection systems. However, 99% (or more) of the solvent that enters the adsorption plant is recovered. 

Operating experience with the Couitaulds plant has shown the recovery efficiency to be at least as high as for a fixed-bed plant and steam consumption a little lower. Carbon attrition has proven to be somewhat of a problem as the accumulation of flnes in the bed increases the residence time, which in turn leads to a greater adsorption of water at the expense of CS2. This problem can be partially resolved by drawing off fines collected from the exit gas instead of returning them to the bottom adsorber tray as shown in the flow diagram. However, this. solution leads to an increased requirement for makeup carbon. 

Extraction (discussed in Chapter 5) uses the selective adsorption of a component in a liquid to separate specific molecules from a stream. In application extraction may be coupled with its cousins, extractive distillation and azeotropic distillation, to improve extraction efficiency. Typical refinery extraction applications involve aromatics recovery (UDEX) and lubricants processing (furfural, NMP). Extractive distillation and azeotropic distillation are rarely employed in a refinery. The only... 

The technologies used in the control of gaseous organic compound emissions include destruction methods such as thermal and catalytic incineration and biological gas treatment and recovery methods such as adsorption, absorption, condensation, and membrane separation. The most common control methods are incineration, adsorption, and condensation, as they deal with a wide variety of emissions of organic compounds. The most common types of control equipment are thermal and fixed-bed catalytic incinerators with recuperative heat recovery, fixed-bed adsorbers, and surface condensers. The control efficiencies normally range between 90% and 99%. 

Cocurrent depressurization, purge, and pressure-equalization steps are normally added to increase efficiency of separation and recovery of product. At the end of the adsorption step, the more weakly adsorbed species have been recovered as product, but there is still a significant amount held up in the bed in the inter- and intraparticle void spaces. A cocurrent depressurization step can be added before the blowdown step, which is countercurrent to adsorption. This increases the amount of product produced each cycle. In some applications, the purity of the more strongly adsorbed components has also been shown to be heavily dependent on the cocurrent depressurization step [Cen and Yang, Ina. Eng. Chem. Fundam., 25, 758-767 (1986)]. This cocurrent blowdown is optional because there is always a countercurrent one. Skarstrom developed criteria to determine when the use of both is justified [Skarstrom in Li, Recent Developments in Separation Science, vol. II, CRC Press, Boca Raton, pp. 95-106 (1975)]. 

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