GB423328A - Improvements in the removal and recovery of benzene and naphthalene from gases particularly coal distillation gases - Google Patents

Abstract

<PICT:0423328/III/1> Oil which has absorbed benzene and its homologues and naphthalene from coal gas is distilled preferably in the presence of water or steam, and the distillate which includes a portion of the washing oil is preliminarily rectified at such a temperature that only the easily boiling fractions of the washing oil go over with the absorbed products. This distillate is finally rectified at a temperature allowing only benzene and its homologues to pass off, the naphthalene being removed in solid form by cooling the residue which together with the residues from the distillation and preliminary rectification is then returned to the washing oil supply. Used washing oil passes through a heater 4 to a bubble tower 7 in which steam is admitted through a pipe 11. Vapours pass to a condenser 13 and thence to a tank 15 in which water is separated from the condensates which are then supplied to a preliminary rectifier 19 together with uncondensed vapours from the condenser. Heating coils at the base of the rectifier cause vapours to pass off through a dephlegmator 23 cooled as by cold water to a main rectifier 30 of similar type from which vapours of benzene and homologues pass to a condenser 32. The liquid residue is discharged into a naphthalene crystallizing pan 37 and thence at room temperature into a storage tank 39 which also receives the residue from the preliminary rectification. The residual oil from the bubble tower 7 is also returned to the storage tank after having passed through a heat exchanger 1 and a water-cooled pipe system 45. The used washing oil is delivered from the gas scrubbers into a tank 40 and is preheated by acting as the cooling liquid in condenser 13 and exchanger 1 before being pumped to the heater 4.