GB678175A - A process for the recovery of phenols from ammonia liquor and other liquors - Google Patents

Abstract

<PICT:0678175/III/1> In the recovery of phenols from aqueous liquors by extraction with solvents such as benzene, benzine, butyl acetate, the solvent is distilled off to recover the phenols in a two-stage process, part of the solvent being evaporated in a first stage at super-atmospheric pressure (e.g. 8 atmospheres) and the remainder in a second stage at atmospheric pressure, the vapours from the first stage while still at high pressure being utilized to vaporize solvent from the residue from the first stage, after its reduction to atmospheric pressure. As described the phenol-containing solvent enters the plant at 1 and is pumped by pump 2 through heat exchanger 3 to steam preheater 5 from which it passes to the high pressure column 9. The "bottoms" of this column are partly circulated through auxiliary heater 11 back to the column and partly drawn off at 15 and passed through pressure-reducing-valve 16 causing some of the remaining solvent to vaporize. The mixture of liquid and vapour passes through heat exchanger 17, where it is heated by vapours from the column 9, to a second column 19. Part of the condensate from heat exchanger 17 is returned at 33 to the column 9 as reflux. The bottoms from column 19 are partly recirculated to the column via boiler 37 and partly drawn off as product at 42. Column 19 may be further heated indirectly by steam at 34 and directly by steam supplied through pipe 35. The vapours from column 19 after passing through heat exchanger 3 and heat exchanger 46 by which they heat the ammonia or other liquor treated in the phenol-extraction plant, are condensed at 29 and the condensate collected in receiver 30. Part of the condensate is returned to column 19 as reflux. The solvent from heat exchanger 17, after reduction in pressure at 21 passes to separator 22 from which vapour may be fed by line 23 to the vapour line 24 from column 19 to provide extra heat for the exchangers 3 and 46. Liquid from separator 22 is cooled at 25 and collected at 26. Alternatively the line 23 may be omitted and the vapours condensed at 22 and 25.