Fluid coking process

Abstract

A fluid coking process is operated in a fluidized bed coking reactor in which a plurality of heavy oil inlet nozzles are arranged in a number of rings around the periphery of the dense bed reaction section at vertically spaced elevations. A heavy oil feed is injected with atomization steam through the nozzles into the fluidized. bed, operating at a lower steam-to-oil ratio for the upper ring or rings of nozzles than for the lower ring or rings.

What is claimed is: 
     
         1 . In a fluid coking method operated in fluidized bed coking reactor having (i) a dense bed reaction section of circular horizontal cross-section about a vertical axis and confined by a reactor wall and (ii) a plurality of heavy oil inlet nozzles located in the dense bed reaction section and arranged in rings around the periphery of the reactor wall in the reaction section at vertically spaced elevations by means of which a heavy oil feed is injected into a fluidized bed in the dense bed reaction section to thermally crack the feed to form solid coke and vaporous cracking products, the improvement comprising:
 injecting the heavy oil feed into the fluidized bed from the upper ring or rings of nozzles at a lower steam-to-oil ratio than from the lower ring or rings of nozzles.   
     
     
         2 . A fluid coking method according to  claim 1  in which the uppermost rings are operated at the same steam-to-oil ratio and the lower rings are operated at the same steam to oil ratio, the steam to oil ratio of the upper rings being lower than that of the lower rings. 
     
     
         3 . A fluid coking method according to  claim 1  in which the fluidized bed coking reactor has six rings of nozzles and the uppermost two rings are operated at a steam-to-oil ratio lower than that of the four lower rings. 
     
     
         4 . A fluid coking method according to  claim 3  in which the four lower rings are operated at the same steam-to-oil ratio higher than that of the uppermost two rings. 
     
     
         5 . A fluid coking method according to  claim 1  in which the lowermost ring or rings are operated with steam and with or without oil feed. 
     
     
         6 . A fluid coking method according to claim I in which the uppermost rings are operated at a steam-to-oil ratio from about 0.25 to 0.35% w/w and the lower rings at a steam-to-oil ratio of about 0.9 to 1.1% w/w. 
     
     
         7 . A fluid coking method according to  claim 1  in which the uppermost rings are operated at a steam-to-oil ratio from about 0.4 to 0.6% w/w and the lower rings at a steam-to-oil ratio of about 1.3 to 1.5% w/w. 
     
     
         8 . A method for modifying the operation of a fluid bed coking unit which has (i) a dense bed reaction section of circular horizontal cross-section about a vertical axis confined by the reactor wall, and (ii) injection nozzles for injecting a heavy oil feed with the aid of atomizing steam in at least some of the rings, the nozzles being arranged in a series of rings at vertically spaced intervals around the periphery of the upper portion of the dense bed reaction section; the modification method comprises:
 operating the unit after modification at an overall steam/oil ratio for rings in which oil is injected with atomizing steam at substantially the same rate or higher as in the unit before modification but with the ratio of steam-to-oil feed on the uppermost ring or rings lower than for lower rings,   
     
     
         9 . A modification method according to  claim 8  in which the uppermost rings are operated at the same steam-to-oil ratio and the lower rings are operated at the same steam to oil ratio, the steam to oil ratio of the upper rings being lower than that of the lower rings. 
     
     
         10 . A modification method according to  claim 9  in which the fluidized bed coking reactor has six rings of nozzles and the uppermost two rings are operated at a steam-to-oil ratio lower than that of the four lower rings. 
     
     
         11 . A modification method according to  claim 9  in which the four lower rings are operated at the same steam-to-oil ratio higher than that of the uppermost two rings. 
     
     
         12 . A modification method according to  claim 8  in which the lowermost ring or rings are operated with steam and with or without oil feed.