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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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22.2 Solvent recovery 1543<br />

22.2 SOLVENT RECOVERY<br />

Isao Kimura<br />

Kanken Techno Co., Ltd., Osaka, Japan<br />

22.2.1 ACTIVATED CARBON IN FLUIDIZED BED ADSORPTION METHOD<br />

This section discusses a solvent recovery process developed by Kureha Engineering Co.<br />

Ltd., Japan. 1 In this continuous process, spherical particles <strong>of</strong> activated carbon (AC) circulate<br />

in the adsorption and desorption columns by fluidization. In the adsorption column, the<br />

particles form fluidized beds on multi-trays to adsorb the solvent in counter-current contact<br />

with the feed gas. The cleaned gas is released from the top <strong>of</strong> the adsorption-column to the<br />

atmosphere.<br />

The carbon absorber with adsorbed solvent is electrically heated (150-250°C) at the<br />

upper part <strong>of</strong> the desorption column and solvent is desorbed by nitrogen, which is supplied<br />

from the bottom <strong>of</strong> the desorption column. Nitrogen is continuously recycled in the<br />

desorption column. The solvent in the carrier gas is fed to a condenser for its recovery.<br />

Features <strong>of</strong> the process:<br />

• Atmospheric condensate is the only waste product because nitrogen (or air) is used<br />

as the carrier gas.<br />

• High flow rate per unit area because the process is conducted by fluidization.<br />

• Low thermal energy loss because both the adsorption and desorption are conducted<br />

at constant temperature.<br />

• Low electric energy consumption because the fluidization needs less blower driving<br />

power.<br />

Figure 22.2.1 shows the process diagram and Table 22.2.1 shows application data.<br />

Figure 22.2.1. Flow diagram <strong>of</strong> the process.

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