JPS5278903A - Catalytic cracking method by catalyst fluid bed - Google Patents

Abstract

1516590 Fluid catalytic cracking TEXACO DEVELOPMENT CORP 25 Nov 1976 [22 Dec 1975 (2)] 49118/76 Heading C5E Cracked hydrocarbon vapours from a fluidized catalytic cracking zone are charged to a fractionation column and separated into a wet gas and naphtha fraction and light, intermediate and heavy cycle gas oil fractions and the light and intermediate cycle gas oil fractions are separately stripped with stripping of the light cycle gas oil fraction and/or of the intermediate cycle gas oil fraction being carried out with reboiled stripped light and/or intermediate cycle gas oil respectively. Hydrocarbon vapours 7 from the fluidized catalytic cracking of a feed 1 (e.g. an atmospheric or vacuum gas oil, an atmospheric residue, shale oil or naphtha) are separated into a wet gas fraction (comprising C 4 and lighter components) 19, a naphtha 22 boiling in the C 5 -430‹F range, a light cycle gas oil fraction 24 boiling in the 400-650‹F range, an intermediate cycle gas oil 32 boiling in the range 575-750‹F and a non-distilled heavy cycle gas oil 51. A portion of the stripped intermediate cycle gas oil 34 is reboiled in a direct fired reboiler 36 and the remainder 42 is recycled to the cracking zone via cracking riser 13. The vapour streams 31 and 41 from the stripping at 25 and 33 are returned to the column 14. Figure 2 (not shown) illustrates a process in which a portion of the stripped light cycle gas oil is reboiled by indirect heat exchange with a portion of the heavy cycle gas oil 51 and all or a portion of the vapours 31 comprising naphtha boiling range components is charged to the stripping vapour ring 8 to fluidize the dense phase catalyst bed 4 and to be converted into lower boiling high octane naphtha.