GB680655A - Improvements in or relating to the purification of kerosene - Google Patents

Abstract

<PICT:0680655/III/1> Kerosene is initially treated with sulphur dioxide to form a raffinate and extract, and the raffinate thus obtained is treated with bauxite or absorbent clay. The pocess is particularly applicable to those kerosenes having a wick char value of more than 10 as measured by test method 10-44 of the Institute of Petroleum, and to those obtained by the fractionation of crude oil having a sulphur content of 1.4 per cent or more. The sulphur dioxide treatment is preferably carried out in counter-current in the liquid phase at a temperature between -40 and +25 DEG F and 0-100 pounds per square inch. The amount of sulphur dioxide is preferably 25-100 per cent of the oil used. The solid adsorbent may be formed into a bed through which the raffinate is passed, or it may be formed into a slurry with the raffinate. O.1 to 4 lbs. adsorbent per U.S. barrel of oil (preferably 1 lb. per U.S. barrel) may be employed at a feed rate of about 0.25 to 4 vols. of oil per volume of adsorbent per hour. The adsorbent step is usually carried out at atmospheric temperature and pressure, but elevated temperature and pressure may be used if desired. Other additional steps, e.g. hypochlorite sweetening or Doctor sweetening, may be employed to reduce the sulphur content further. In the preferred embodiment the sulphur dioxide treatment is followed by a process for the removal of mercaptans and then the kerosene is treated with the adsorbent. As shown, kerosene is contacted in zone 1 with sulphur dioxide in counter-current, the sulphur dioxide flowing downwardly. The extract phase may be distilled to recover sulphur dioxide, which may be recycled. The raffinate is distilled in zone 8, the sulphur dioxide being removed and recycled through line 9, the raffinate product being passed through line 10 to zone 11 for hypochlorite sweetening. The hypochorite solution (2-30g/ litre of NaOCl and containing more than 2g/ litre of free NaOH) in an amount equivalent to 1-10 volume per cent, is mixed with the raffinate product in an orifice mixer 25 and allowed to settle in vessel 11. The sweetened kerosene is removed through line 12 and treated with sand or other moisture removing agent in vessel 13, the dried kerosene passing through line 15 to the adsorbent treating tower 16 filled with bauxite or an adsorbent clay such as Fuller's earth. In an example (4) a kerosene of boiling range 357-512 DEG F from an Iraq crude oil and having a wick char value of 46 is treated with sulphur dioxide and subsequently with Attapulgus clay, the product having a wick char value of 6.