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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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22.1 Absorptive solvent recovery 1517<br />

Figure 22.1.6. Desorption efficiency and steam consumption.<br />

Figure 22.1.7. Options for solvent recovery by steam desorption (After references 2, 3,12).<br />

If the solvents are partly or completely miscible with water, additional special processes<br />

are necessary for solvent separation and treatment (Figure 22.1.7). For partly miscible<br />

solvents the desorpt steam/solvent mixture is separated by enrichment condensation,<br />

rectification or by a membrane processes. The separation <strong>of</strong> completely water-soluble solvents<br />

requires a rectification column. 2<br />

After steam regeneration, the hot and wet carbon bed will not remove organics from<br />

air effectively, because high temperature and humidity do not favor complete adsorption.<br />

The activated carbon is therefore dried by a hot air stream. Before starting the next adsorption<br />

cycle the activated carbon bed is cooled to ambient temperature with air. Typical operating<br />

data for solvent recovery plants and design ranges are given in Table 22.1.6.

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