GB731838A - Improvements in or relating to cracking of heavy hydrocarbon oils - Google Patents

Abstract

<PICT:0731838/III/1> Heavy hydrocarbon oils are cracked to lighter hydrocarbons including gasoline by contacting the oil with hot solid particles circulating between the cracking zone and a regeneration zone, the pressure in the system being maintained between 150 and 800 p.s.i.g.; the contaminated particles are regenerated, at a temperature of 1600-2500 DEG F., with a mixture of steam and oxygen, in the molar ratio of about 1.5 : 1 to 5 : 1, which react with the carbonaceous deposit to give a gas containing substantial proportions of hydrogen and carbon monoxide, and this gas is passed into the cracking zone, which is maintained at a temperature of 850 DEG to 1100 DEG F., so as to maintain a hydrogen partial pressure of 35 to 200 p.s.i. therein. Suitable contact materials include quartz, alumina, magnesia, zircon, beryl and bauxite. The vessel 10 contains both a cracking zone 12 and a regeneration zone 11, the two zones being separated by perforated plate 13. For cracking asphaltenic petroleum oil (13 per cent carbon residue and 5 per cent sulphur), bauxite particles which will pass through a 20-mesh sieve (but not through a 200-mesh sieve) are used as catalyst. The oil is preheated to 750 DEG F. and fed through distributor 16 into zone 12 where it contacts the fluidized bauxite at 980 DEG F. Contaminated bauxite particles pass downwards through plate 13 into zone 11 where they are contacted with a mixture of steam and oxygen, in the volume ratio of 15 : 8, introduced through distributer 17. The carbonaceous matter on the bauxite is thereby converted, at 1750 DEG F., into gases rich in hydrogen and carbon monoxide. The regenerated particles are conveyed from zone 11 to zone 12 through tube 14 by injecting steam into the lower end of the tube. The regeneration product gases flow up through plate 13 and become mixed with the hydrocarbons being cracked in zone 12. The pressure maintained in vessel 10 is 460 p.s.i.g., and the hydrogen in the gases flowing up into zone 12 exerts a partial pressure therein of 75 p.s.i. The mixture of cracked vapours and regeneration product gases is withdrawn through outlet 18, and is subjected to cooling and separation into fractions including gasoline, light gas oil and heavy gas oil. The gasoline has an octane number of at least 85, and contains at least 40 per cent of olefines and at least 30 per cent of aromatic hydrocarbons. The uncondensed product gas contains 32 per cent by volume of hydrogen and 25 per cent by volume of carbon monoxide.