Cyclic, adsorption

Cycle Control Valves are the heart of cycle control for cyclic adsorption systems. These on/off valves switch flows among beds so... 

TSA [Thermal (or Temperature) swing adsorption] A method for separating gases by cyclic adsorption and desorption from a selective adsoibent, at alternating temperatures. Less commonly used than PSA. 

Cyclic adsorption processes such as parametric pumping, cycling zone adsorption and heatless adsorption have received much attention both theoretically and experimentally in the past several years (3j. Skarstrom (4J has reviewed applications of heatless adsorption (synonymous with pressure swing adsorption) to air drying, hydrogen purification and air fractionation. 

TABLE II Examples of Cyclic Adsorption Separation Processes... 

Fractionation of Citrus Oil by Cyclic Adsorption Process in Supercritical C02... 

A cyclic adsorption process for citrus oil processing in supercritical carbon dioxide (SC-C02) was studied with silica gel adsorbent. Based on the adsorption equilibrium properties, where adsorbed amounts decreased with the increase in the solvent density and oxygenated compounds were selectively adsorbed on silica gel, a continuous cyclic operation between the adsorption step at 8.8 MPa and 313 K, and the desorption step at 19.4 MPa and 313 K was demonstrated Highly concentrated fraction of oxygenated com pounds was continuously obtained for the desorption and blowdown step. The proposed system showed the feasibility of the continuous operation for citrus oil processing. 

Commercial sorbents used in cyclic adsorption processes should ideally meet the following requirements ... 

These basic requirements are usually proposed for adsorbents used in cyclic adsorption processes that are based on physical adsorption. There is an increasing demand for strong chemical adsorbents used in... 

Cyclic adsorption processes Two examples (a) thermal swing adsorption -maximization of total adsorption efficiency and minimization of consumption rate of regeneration energy, and (b) rapid pressure swing adsorption -maximization of both purity and recovery of the desired product for RPSA. Modified Sum of Weighted Objective Function (SWOF) method Modified SWOF method is superior to the conventional SWOF as it was able to find the non-convex part of the Pareto-optimal set. Ko and Moon (2002)... 

Ko, D. and Moon, I. (2002). Multiobjective optimization of cyclic adsorption processes. Industrial Engineering Chemistry Research 41, 1, pp. 93-104. 

All cyclic adsorption applications rely on regenerability, which allows the adsorbent to operate in sequential cycles with uniform performance. This means that each adsorbable component... 

Usually, the nucleophilic substitutions under NPTC condition are described by an S -type reaction both in solid-liquid and liquid-liquid systems in which they can proceed at the interface through the formation of cyclic adsorption complexes. The activity of the nucleophilic reagent in the organic phase is determined by the polarity of the organic solution and the hydration in liquid-liquid system. In the solid-liquid system, the reaction is highly affected by the organic solvent. 

Fig. 4.3 CO2 cyclic adsorption (25 °C) and regeneration (85 °C) of PAF-1 blade), PAF-3 blue), and PAF-4 green) red is temperature). Reproduced from Ref. [29] with permission from the Royal Society of Chemistry...

The McCabe-Thiele and Kremser methods have also been applied to analyze less common separation methods. A modification of the McCabe-Thiele method has been applied to parametric punping, which is a cyclic adsorption or ion exchange process iGrevillot and Tondeur. 19771. A similar modification can... 

In a linear equilibrium system adsorption and desorption are symmetrically equivalent processes so the restriction to equal times for the adsorption and desorption cycles in a two-bed system does not limit the efficiency with which the adsorbent may be used. However, most cyclic adsorption separation processes operate under conditions such that the isotherm for the. more strongly adsorbed species is of favorable (type I) form. Under these conditions... 

The choice of optimal operating conditions for a two-bed cyclic adsorption system presents a complex optimization problem since the effects of all the process variables (cycle time, bed length, adsorption and desorption temperatures, purge gas velocity) are coupled. However some general guidance may be derived from a comparatively simple theoretical analysis. 

The mathematical models used to simulate die dynamic behavior of a cyclic adsorption system are essentially similar to those described in Chapters 8 and 9. There is however one important difference. In most of the models discussed in Chapters 8 and 9 an initially sorbate free-adsorbent bed was... 

Because the sorbent needs to be regenerated for most commercial applications, adsorption processes are necessarily cyclic. A number of cyclic adsorption processes are available, depending on the way the sorbent is regenerated. These processes have been discussed extensively elsewhere (e.g., Yang, 1987 Humphrey and Keller, 1997). 

Numerous studies have been undertaken on the use of layered beds consisting of different sorbents for cyclic adsorption/ion exchange (Klein and Ver-meulen, 1975 Frey, 1983 Wankat and Tondeur, 1985 Chlendi and Tondeur, 1995 Watson et al., 1996 Pigorini and LeVan, 1997). For hydrogen purification using layered activated carbon and zeolite, Chlendi and Tondeur (1995) used the... 

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