Patent GB-784136-A (GB)
Title: Cracking heavy hydrocarbon oils
IPC: C10G47/34
Filed: 1954-04-06
Abstract: <PICT:0784136/III/1> In order to obtain lighter products such as gas oil from heavy hydrocarbon oils, particularly residual oils containing asphalt, the oil is subjected to thermal cracking in the presence of a hydrogen-donor diluent comprising a partially hydrogenated hydrocarbon oil boiling within the range 500-1100 DEG F., and containing substantial proportions of condensed-ring aromatic hydrocarbons.  The conversion takes place with very little formation of coke; and the gas oil so obtained is suitable for catalytic cracking to produce gasoline.  Crude oil is fed through line 11 into still A which comprises both atmospheric and vacuum stages; and is reduced to a 900 DEG  F. residuum in the atmospheric stage and then to a 1050 DEG  F. in the vacuum stage.  Gases (C3 and below) are taken off overhead, and C4-200 DEG  F. virgin light naphtha is withdrawn through line 17.  The heavy naphtha (B.R. 200-350 DEG  F.) is taken through line 19 to hydroforming unit B, wherein a fluidized bed of finely-divided molybdena catalyst is maintained.  Gas oil (350-1050 DEG  F.) is withdrawn from still A through line 21, and is passed to catalytic cracking unit C.  The residuum from still A flows through line 23 to unit F where it is thermally cracked in the presence of diluent.  Reformed gasoline is withdrawn from unit B through line 27 and is united in line 29 with the gasoline from cat. cracker C; the mixed gasoline is then combined with the light naphtha in line 17.  Hydrogen gas, produced in unit B, passes through line 33 to hydrogenator E. Heating oil (heavy naphtha) produced in cat. cracker C is withdrawn to storage via line 39.  A fraction boiling above 650 DEG  F. is taken off from unit C through line 41, and is passed to thermal cracker D, where pyrolysis is effected at 800-950 DEG  F. Gasoline is withdrawn from unit D via line 45, and is united with the motor fuel products in line 17; while heating oil is taken off through line 47 to mix with that in line 39.  A fraction boiling between 700 DEG  and 950 DEG  F. is taken through line 49 to hydrogenator E where it is hydrogenated with the hydrogen provided by hydroformer B.  The hydrogenation is conducted in the presence of a sulphur-insensitive catalyst such as a heavy metal sulphide, and is operated so as to incorporate 500 to 2500 S.C.F. of hydrogen with each barrel of the 700-900 DEG  F. fraction in order to convert it into hydrogen-donor-diluent.  The diluent is led from hydrogenator E through line 61 into conversion zone F, where the residuum from still A, combined, if desired, with the tar bottoms from unit D, is pyrolysed at 800-900 DEG  F. under moderate pressure (400 p.s.i.g.). The diluent is supplied in proportions of 20 to 200 per cent based on the residuum to be converted.  Gasoline is withdrawn from unit F through line 65 to join the stream in line 29.  Gas oil is withdrawn through line 67, and is united with the feed to cat. cracker C in line 21.  A fraction boiling between 700 DEG  and 950 DEG  F. is withdrawn through line 69, and returned to hydrogenator E.  The residuum from unit F is in part purged through line 77, the remainder being recycled to the unit.  If desired, the thermally-cracked gasolines in lines 45 and 65 may be passed through hydroformer B.