Dehydration of the still residue from the rectification of raw benzene

Abstract

The still residue from the rectification of raw benzene is a stable emulsion with a water content exceeding 60%. Until 2012, it was dehydrated in the department of coumarone–indene resins by vacuum distillation. The closing of that department entailed the development of an alternative technology, which consists of two stages: 1) addition of 20–25% of the benzene fraction to the still residue and the removal of the water that settles in the lower layer; 2) distillation of the benzene and residual water by the heat from spent steam. After dehydration, the still residue contains 0.5–3.0% water and complies with Technological Specifications TU 2415-194-00190437. This technology permits the processing of the waste from the tar-distillation department in the stills of the benzene department—in particular, light distillates from the naphthalene column (containing naphthalene and 40–60% water) and light oil of no commercial value that contains phenolic hydrocarbons, resin-forming compounds, and phenols. After adding 10–15% of such wastes to the raw still residue, the mixture is dehydrated by the proposed technology. The introduction of such wastes in the still residue prior to dehydration permits the additional production of up to 4 t phenolic hydrocarbons and 40 t of commercial products such as coal solvent naphtha and coumarone–indene resin each month.