| 摘要 |
<p>Solvent extn. of the desired liq. substance, partic. aromatics, from feed containing at least two solvents of different b.pt. above that of the reffinate, introduces each solvent separately at different extn. column positions, to obtain either purer raffinate with reduced solvent loss, or higher extract yield, less solvent free, than before. For almost solvent free raffinate, the enriched solvent component (A), characterised by max. insolubility and high selectivity w.r.t. the substance to be extracted is introduced into the extn. column, where raffinate is taken off, while enriched solvent component (B), characterised by high solubility therein of the substance to be extracted is introduced between the inlets for the feed stock and solvent (A), or vice versa for high yield. The usual reflux column is on stream between extn. and solvent recovery columns. In the latter, raffinate is distilled off, and the lower boiling solvent between inlet and base and/or from the overheads receiver, while the higher boiling solvent is taken from the base. Both components are distilled off in the reflux and solvent recovery columns, but the lower boiling solvent may be distilled off by itself, or in addn. to the overheads.</p> |
