Patent GB-423292-A (GB)
Title: Improvements in or relating to the heat conversion of hydrocarbon oils
Filed: 1934-06-16
Abstract: <PICT:0423292/III/1> <PICT:0423292/III/2> A multi-stage cracking process combines in unitary manner topping a crude oil, further evaporating the topped oil by direct contact with cracked vapours to give a heavy oil, viscosity breaking the heavy oil, cracking a clean condensate obtained by fractionation of the mixed vapours obtained from the cracking and topping stages, reforming the end products to raise their anti-knock value and stabilizing the gasoline produced, together with heat-exchange between the various stages.  Crude oil delivered through a line 9 and preheated to 450 DEG  C. in heat-exchangers 11, 12, 13, 14 is flashed in the primary drum 15 of a tower 1 from which vapour pass off through the exchanger 11 and condenser 18 to a storage drum 19 from which some of the condensate is returned as reflux through a line 20 to the drum 15.  The unvaporized oil is withdrawn through a line 23 and passed into a secondary flash drum 22 where further vaporization of the oil is obtained by contact with vapours evolved in a tar flasher 24 and introduced through a pipe 25 and heat-exchanger 26.  Vapours are withdrawn through a line 80<1> and condenser 180 to a receiver 80 from which condensate is returned through a line 31 to form with condensate produced from a fraction fed through a line 30 a fraction which is collected on a tray 35 and removed to a receiver 38.  The residual oil from the flash drum 22 is passed through heat-exchangers 26, 42 and lines 39, 40, to an evaporator 2 where it is partially vaporized by flowing in counter current to hot vapours from the cracking plant and the unvaporized portion is collected in a tray 44 and passed to an accumulator drum 46 as stock for the viscosity breaking operation which is carried out by passing the oil through the coils of a cracking furnace 3 the products from which are returned through a pipe 52 to the evaporator 2.  The vapours evolved in the evaporator 2 after contact with reflux supplied through pipes 40, 55, 56 pass off through a line 61 into a fractionating tower 6. In this tower fractionation is controlled by reflux introduced through lines 64, 67 and vapours pass off at the top through a pipe 70 and condenser 71 into a primary gas separator 7 while a condensate is collected in a tray 73 and passed to the receiver 38.  The reflux collecting at the bottom of the tower 6 is removed as stock for the vapour phase cracking stage through a line 102 to the coils of a furnace 4 and thence through a line 104 into the soaking drum 5, the vapours from which pass to the evaporator 2 through a line 105 which is maintained free from obstruction by circulating residual oil from the evaporator 2 through heat-exchanger 42 line 143 and valved lines 400, 401, 402, 403. The gas oil stock accumulated in the drum 38 may be passed to a header line 57 from which it is directed (a) through line 152 and 116 into the base of the evaporator 2 (b) through heatexchanger 107 and line 106, with optional byepassing through a coil 93, into the drum 5 (c) through lines 55, 56 into the evaporator 2.  The residues from the soaker drum 5 are sent through a line 129 either through a line 150 into the bottom of the tower 6 or through a line 146 to mix with the residues from the bottom of the evaporator 2 the mixed residues being flashed in the tar flasher 24 at the bottom of the tower 1 in contact with reflux introduced from the drum 38 through a line 113 and with the aid of hot vapour from the drum 2 led through a line 111.  Fuel oil is withdrawn from the flasher 24 through a cooler 156 and line 155, and reduced in viscosity by admixture with gas oil from a line 160, or it may be recirculated in part through a line 158.  The heavy naphtha fraction accumulating in the drum 80 is stripped of gasoline in a tower 131 and the naphtha is reformed by passing it via a line 114 through coils 115, 117 and 118 in the furnace 4, the reformed products being passed through line 116 to the evaporator 2.  The vapour phase furnace comprises two separate independently fired radiant sections 109 and a commonly fired connection section 108 and soaking section 110 and the oils are led through the symmetrical coils which are provided with two tubes in parallel in the sections 108, 109 and three tubes in parallel in the sections 108, 109 and three tubes in parallel in the soaking section 110 the flow of oil in each path being maintained constant by controllers 119.  The furnace 3 is similarly provided with parallel coils controlled by regulators 471.  The gasoline distillate collected in the separator 7 after rough separation of gases which pass off through a pipe 83 is stabilized in a tower 8 to which it is passed through an exchanger 86 and enters above trays 87 and below trays 88.  Reflux collecting on a tray 89 is withdrawn through a pipe 90 and recirculated through an exchanger 76 while stabilized gasoline is withdrawn through heat-exchangers 86, 94 to storage.