GB620753A - Improvements in or relating to refining of naphthalene - Google Patents

Abstract

<PICT:0620753/III/1> In recovering naphthalene by fractional distillation of crude naphthalene, vapours are refluxed with liquid derived at least in part by introducing into the vapours a liquid (preferably water) which is volatilized and which is immiscible with liquid naphthalene. The vapours of naphthalene and of the liquid are then condensed together and the naphthalene separated from the liquid. Naphthalene crude is pumped through lines 7, 9 to batch-still kettle 10 which has direct steam pipe 12, indirect steam coil 13 and outlet line 14. Vapours from the kettle pass through pipe 15 to column 16 containing bubble cap trays 17. Condensate from the fractionating tower is returned to the still through pipe 18. Fractionated vapours leave the column through pipe 19 and valve 20 to water-tube condenser 21 which by circulation of water, which may be heated with steam, cools the naphthalene vapours to a desired temperature. Effluent from the column 16 may then be condensed to a liquid form or to a slurry of solid naphthalene and added liquid. The condensate flows from the condenser through insulated pipe 26. First runnings containing no naphthalene are diverted to separator 28 from which aqueous material is removed by pipe 29 to a sump and non-aqueous material by pipe 30, either to receiver 33 or by pipes 35, 38, pump 37 and tank 36, back to the top of column 16 for control of reflux ratio during the early part of the distillation. When naphthalene distillation is established, condensate from condenser 21, is diverted by pipe 50 either into tank 52 or into pure products tank 55. Tank 52 handles intermediate fractions containing some naphthalene. Condensate enters over weir 56 and is cooled by water jet 57. The tank has a vent 32a and baffle plates 58, 59 to retain scum and dregs as the watery condensate flows to screen 60 through which water passes to drain pipe 62. Slush or solids remaining in tank 52 are melted at the end of a batch distillation by steam coil 63 and returned by pipe 64 to still kettle 10. The baffle plates 58, 59, and 60, may be removed and water and oil separated by decantation by manifold 61, which may be connected to pipe 64. Pure products tank 55 is insulated and surrounded at its base by a steam-heated shell which keeps the naphthalene molten so that it may be syphoned by insulated pipe 65 to storage tank 67 equipped with steam coil 68. Water is decanted from the top of tank 55 by pipe 69 to box 70 where it is quickly cooled by water spray 71 to solidify entrained naphthalene which is caught by screens 72, water running to waste by pipe 73. Reflux producing liquid, e.g. water, enters column 16 by pipes 74, 79 and spray 80. Valve 75 and rotameter 78 permit accurate control of its rate of flow. To permit reduction of pressure in various parts of the apparatus a steam-jet vacuum pump 39 is provided. This can communicate with separator 28, condenser 21, vapour line 19 from the column 16, tank 55 or tank 52. All vapours going to pump 39 are first shock cooled by water spray 42 in condenser 40, the water and condensates from this condenser going to tank 52 or tank 55. This prevents stoppage of pump 32 by condensed naphthalene.