Patent GB-837765-A (GB)
Title: Separation of gaseous mixtures
IPC: C07C7/00
Filed: 1956-11-07
Abstract: A process for separating a non-condensable gas from a hot liquid/vapour hydrocarbon mixture comprises partially cooling the mixture and passing it to the first of a series of at least two vapour/liquid separation zones, removing vapour and non-condensable gas from each zone and passing them to the next zone, cooling between each zone to condense part of the vapour, distilling the combined condensate from the first and second zones to recover a high- and a low-boiling condensate fraction, passing part of the low-boiling condensate with the vapour feed to the last zone to absorb condensable material therein, and recovering a non-condensable material from the last zone.  The <PICT:0837765/III/1> process is particularly applicable to processes wherein hydrocarbons are treated in the presence of hydrogen, e.g. desulphurization, reforming, isomerization, dehydrogenation, hydrogenation, and hydrocracking.  In the desulphurization of gas oil the oil is fed via line 2 through heat exchangers 4 and 6 to heater 8, and then passes through line 16 where it is joined by heated recycle hydrogen from line 85.  The mixture then passes to desulphurization reactor 20 which is supplied with unheated recycle hydrogen by lines 22.  The effluent from reactor 20 passes through line 26 via heat exchangers 28, 6 and 30 and enters accumulator 34 via line 36.  The vapour phase from accumulator 34 passes via line 38 and water-condenser 40 to accumulator 42 from which liquid hydrocarbons join those from accumulator 34 in line 36 via line 44.  The vapour from accumulator 42 passes to accumulator 50 through line 46, and line 48 where it is joined by liquid from fractionator overhead accumulator 94 while liquid both cools the vapour and acts as an absorbent for the lighter hydrocarbons therein.  Liquid hydrocarbons are withdrawn from accumulator 50 via line 52, where they are joined by the overheads condensate of fractionator 88 from line 90, to accumulator 94. The hydrogen-rich vapours from accumulator 50 pass through line 54 to H2S absorber 56 and then through lines 62 and 66 to knock-out drums 70 and 78 where entrained liquid is removed. They are compressed in compressor 74 between the drums before being returned to the desulphurization reaction via lines 82 and 84 or 86.  The gas oil withdrawn from the bottom of fractionator 88 is pumped through line 116 and is either sent to storage through line 120 and heat exchanger 4 or is heated in heat exchanger 28 and returned to heat the bottom of the column through line 122.  The desulphurization is carried out at temperatures of at least 600 DEG  F. and preferably below 900 DEG F., and at pressures between 25 and 5000 p.s.i.g.  The catalysts used are the oxides and/or sulphides of Group VI metals, e.g. molybdenum trisulphide and trioxide, chromia or tungsten sulphide either alone or on a carrier e.g. alumina, silica-alumina, magnesia, fuller's earth, keiselguhr, pumice or bentonite clay and with or without an oxide and/or sulphide or iron, cobalt, or nickel as promoter.  The desulphurization can be applied to any hydrocarbon oil containing sulphur, e.g. naphtha, kerosene, gas oil, reduced crudes and crude oil, which may be straight-run, cracked, or mixtures of both.  The operation of the desulphurization can be based on a net consumption or net production of hydrogen, the hydrogen rate can vary between 200 and 10,000 cu. ft/barrel of oil feed, and the process may be practised as either a fixed or moving bed system using a non-fluid or fluid bed technique.