Patent GB-775978-A (GB)
Title: Regeneration, by distillation, of oils used for gas washing
Inventor: MALOY JOHN
IPC: C10K1/18
Filed: 1953-06-01
Abstract: In a process for the purification of coal gas by washing it with a small quantity of petroleum oil to remove naphthalene <PICT:0775978/III/1> <PICT:0775978/III/2> and washing it with a relatively large volume of a petroleum or creosote oil to remove benzole, the benzolized wash oil is stripped with steam, and vapours leaving the benzole stripping still are introduced into the naphthalene-bearing wash oil in order to distil the naphthalene therefrom.  The vapours from the naphthalene stripping still are condensed; and benzole and naphthalene are separated from the water of the condensate.  The regenerated wash oils are re-used for further gas washing; but a part of the naphthalene-free wash oil is withdrawn from the washing-regeneration circuit and is subjected to distillation with benzole-bearing steam from the stripping still until substantially all but the sludge, which causes thickening, has been vaporized, the vapours are fractionated and a condensate of reconditioned wash oil is obtained, which is returned to the circuit. Crude gas from coke oven 1 passes through ascension pipe 2 and main 3 into flushing tank 4, and then into primary coolers 5.  Tar and other liquors are withdrawn from coolers 5 via pipe 6. The gas flows on via pipe 7 to a tar extractor (not shown), and is then washed with petroleum oil in naphthalene washer 8.  The gas leaving washer 8 passes through secondary cooler 11 and ammonia washer 12.  The ammonia liquor, withdrawn from washer 12 via pipe 16, is taken to the ammonia recovery plant.  The ammonia-free gas is washed with oil in benzole washers 14 and 15; and the purified gas is finally passed to a gas holder via pipe 17.  The benzolized wash oil is removed from washers 14 and 15 through pipe 20, and flows through heater 21 into regeneration still 22, which is supplied with steam through pipe 23. The regenerated oil is removed from the still through pipe 25 and, after cooling, is returned to washers 14 and 15.  The naphthalene-bearing wash oil withdrawn from washer 8 via pipe 10, flows via heater 27 into the top of still 29.  The benzole-bearing steam from the head of still 22 is introduced via pipe 30 into the base of still 29.  Valves 33, 34 and 35 control the amount of benzole-bearing steam which is passed to still 29, and the amount which is by-passed.  The vapours leaving the top of still 29 are united with those that have by-passed still 29, the mixed vapours are condensed, and naphthalene and benzole are recovered from the condensate.  The regenerated wash oil withdrawn from the base of still 29 is returned to washer 8 via pipe 32.  The oil used in washer 8 is liable to thicken; and this is avoided by means of the still shown in Fig. 2.  The lower part of the still forms a blowing chamber 40 which is separated from the still proper by bubble tray 41.  The naphthalene-bearing wash oil is admitted to the still via pipe 281, and the regenerated oil leaves via pipe 321, through pipe 42, into chamber 40.  Benzole-bearing steam is blown, via pipes 24 and 301, through the oil in chamber 40; and all the components except sludge are vaporized. The sludge is removed from the chamber via pipe 44. The vapours pass through bubble tray 41 into the still proper, wherein the benzole vapours flow upwards while the reconditioned wash oil condenses and is withdrawn via pipe 321.