GB374386A - Process for the separation of phenols from coal tar and tar distillates - Google Patents

Abstract

In the removal of phenols from coal tar or its distillates by means of aqueous alcohol, the tar and distillates are those drawn off at a reduced pressure of 40 mm. or more of water below atmospheric from ducts in the retort or oven charge of coal, the strength of the alcohol being 77-84 per cent by weight. In an example, gases and vapours are withdrawn from ducts 5 in the coal 2 in a coke oven 1 at 900 DEG C. through pipes 6, 4, 8, 9 to a gas and tar container 10 and a cooler 14, the pressure in the ducts 5 being gradually reduced from 40 to 200 mm. of water below atmospheric. The gases are <PICT:0374386/III/1> then delivered by a centrifugal or turbine blower 16 through a Pelouze or other tar separator 17, washers 18, 19 for ammonia and benzol, and a discharge pipe 20. The condensates from the cooler 14, blower 16, and separator 17 flow to a settling vessel 24, the ammoniacal liquor overflowing into a container 26, and the tar passing into a container 28. The tar is pumped to a holder 30, in which more water is separated, preferably by indirect steam heating. For the alcohol treatment this tar is passed down pipes 31, 42, 43 to a pipe 44 supplied with the required proportion of alcohol from a tank 47 by pipes 46, 45; the mixture flows through a heat-exchanger 49 and is further mixed in a centrifugal pump 48 by which it is delivered through a pipe 50 to a separator 51 having perforated diaphragms 52 to assist separation. The purified tar forming the lower layer passes out through a pipe 54 and is again treated with alcohol, from a pipe 58, in the heat-exchanger 57, pump 56, and settling vessel 59; it discharges through a pipe 62 to a still 71 in which residual alcohol is removed to a condenser 72, a pump 73, and the tank 47; the tar discharges through a pipe 75. The mixtures of alcohol, phenol, and tar oil forming the upper layers in the settlers 51, 59 flow through outlets 53, 60 and a pipe 61 to a still 63 in which the alcohol is driven off to a condenser 64 from which it is pumped through a pipe 67 to the tank 47; the still residue is cooled and allowed to separate in the lower part of the distillation plant into a lower layer of phenolic oil which is drawn off through a valve 70, and an upper layer of dilute alcohol which is withdrawn through a pipe 69 and pumped to the tank 47. Preferably the tar from the tank 30 is passed from the pipe 31 by a pipe 32 to a still 33 and separated into a fraction of water and light oils boiling up to 180 DEG C. which is collected in a vessel 35, a 180-300 DEG C. gas oil fraction collected in vessel 36, a 300-380 DEG C. fraction of phenols containing oil and anthracene collected in vessel 37, and a residue which is withdrawn through a pipe 38; and only the tar oil fractions in the vessels 36, 37 are treated with alcohol. The treated gas oil fraction, after washing with concentrated sulphuric acid, may be used as Diesel engine fuel. The treated fraction from the vessel 37 may be further treated to separate anthracenes.ALSO:Phenols are removed from tar or tar distillates which have been drawn off at a reduced pressure from ducts in the charge of coil in the oven or retort by means of aqueous alcohol if desired at temperatures above normal. In an example gases and vapours drawn off from a charge of Westphalian coking coal are passed through washers and separators to remove ammonia and benzol. The tar, from which more water is separated preferably by indirect steam heating, is treated with aqueous alcohol and the separated tar therefrom again treated with aqueous alcohol. The mixture of alcohol, phenol and tar oil is then distilled to remove some alcohol, which may be again used in the process, and the residue is allowed to separate into a layer of phenolic acid and a layer of dilute alcohol. Preferably the tar to be treated is first distilled and only the gas oil fraction (180-300 DEG C.) and the phenolic oil fraction (300-380 DEG C.) are so treated. The treated gas oil fraction washed with concentrated sulphuric acid is suitable as Diesel engine fuel whilst the phenolic fraction may be further treated to recover anthracene.