| 摘要 |
<p>The process comprises a liquid/liquid extraction of the mixture in 1 or 2 stages to obtain an extract and a raffinate. The extract is submitted to an extractive distillation to recover a light fraction, a heavy fraction and a residue. The light fraction is recycled to the liquid extraction or the 2nd stage of it. The heavy fraction is recycled to a zone above the end of the liquid extraction feed. The residue is rectified to obtain aromatic hydrocarbon solvent using water only as reflux. The process is characterised by a combination of 2 or more of (a) to (c) below. (a) The aq. distillate from the rectification is used exclusively for washing the raffinate and is then recycled to the extraction. (b) The solvent is held in an isoenthalpic manner and a liquid current, comprising a solvent of which the water and aromatic hydrocarbon conten is below that of the rectified solvent, separates from a gas current principally contg. water. and a small amt. of aromatic hydrocarbon (c). The condensed gas current is recycled partly and totally to the extraction stage, or mixed with the extract, or mixed with the residue from the extractive distillation or a combination of these. The process is partic. applied to the extraction benzene, toluene, xylenes and 9C cpds. Compared to current processes in which the isoenthalpic holding stage is not included, the above obtains up to 18% heat economy in the extractive distillation column and about 20% in the fractionation column at the same time recovering higher amts. of product.</p> |
