Patent GB-745548-A (GB)
Title: Improvements in or relating to the refining and cracking of crude petroleum oil
IPC: F02B3/06
Filed: 1953-05-13
Abstract: <PICT:0745548/III/1> A process for refining crude petroleum oil comprises feeding the crude oil into a fractional distillation zone (fractionator), removing a residual fraction boiling above 600 DEG F. from the fractionator, contacting the residual fraction with a fluidized bed of particles, preferably of coke, at a temperature of 800 DEG  to 1100 DEG F. whereby the residual fraction is converted into hydrocarbon vapours containing a major proportion of gas oil, leading the vapours into a fluidized bed of cracking catalyst at 850 DEG  to 1100 DEG F. passing the catalytically cracked products into the fractionator from which the residual fraction was withdrawn, and taking off gasoline from the upper part of the fractionator. Crude oil is supplied through line 1 to still 2 wherein it is fractionated into gas, virgin naphtha, and gas oil.  The bottoms fraction (initial B.P. 650 DEG F.) is passed through line 3 into a lower section of fractionating tower 4, which also receives, through line 9, the hot products from the catalytic reactor 20.  A short residium stream having an initial boiling point of 950 DEG F. is withdrawn from the base of tower 4 through line 8.  Part of this short residium is recycled to still 2 in order to supply heat required therein, but the major portion of the residuum is passed through line 10 to vessel 11, which contains particles of hot petroleum coke maintained as a dense fluidized bed 12 by steam introduced through line 14.  The temperature of the bed is 850 DEG -950 DEG F., and the residuum is converted into coke and hydrocarbon vapours containing less than 20 volume per cent of gasoline.  These vapours pass through grid 21, and come into contact with a dense fluidized bed 22 of catalyst particles (clay or silica - alumina gel) at 900 DEG -1000 DEG F. maintained in reactor 20.  The cracked product vapours are passed through line 9 to the lower part of tower 4 where they supply heat required for the partial vaporization of the residuum introduced through line 3. High-octane gasoline is withdrawn from tower 4 through line 6. Spent catalyst, withdrawn from reactor 20 through standpipe 25, is regenerated with air in regenerator 30.  Part or all of the gas oil stream withdrawn from tower 4 via line 7 may be passed directly to catalyst bed 22 through line 28.  If desired, the oil may first be mixed with some hot catalyst withdrawn from regenerator 30 through a standpipe 33.  Gas oil from line 7 may also or alternatively be fed through line 29 to spray nozzles below the catalyst bed.  Part or all of the gas oil stream 7 may be withdrawn from the system via line 77 to prevent an excessive build-up of refractory cycle stock.  The light gas oil from still 2 may either be passed through line 78 and combined with the gas oil from fractionator 4 for feeding to reactor 20, or it may be withdrawn from the system and disposed of as heating oil or diesel fuel.  Coke particles from bed 12 overflow through orifice 15 into section 16 where the temperature of the particles is raised by direct contact with hot regenerated catalyst introduced through line 17.  Steam is introduced into section 16 through line 18 and this elutriates out the catalyst, which is less coarse and dense than the coke, and carries it up to reactor 20.  Virgin naphtha for reforming and refractory gas oil may also be introduced into section 16.  Reheated coke particles are withdrawn from the base of section 16, and are returned through line 14 to coking bed 12. Additional heat may be supplied to the fractionating stage by adding hot coke, withdrawn through line 19, to bottoms of towers 2 and 4. Specifications 700,309, 710,144 and 723,149 are referred to.