Patent CA-2217889-A1 (CA)
Title: Conditions of operation during coking which leads to higher yields of valuable liquid products
Inventor: TOLLEFSON ERIC L
IPC: C10G9/32
Filed: 1997-10-08
Abstract: A 2-inch diameter, fluid bed coker using a 21 cm bed of Syncrude fluid coke was adapted to feed bitumen, bitumen-in-water emulsions plus steam and nitrogen. Initially feeding was through a 1/8-inch tube incorporated into a steam nozzle. This was later modified to provide feeding of the bitumen plus steam through a side port nozzle at various depths below the surface of the fluid bed. The reaction system was constructed for once-through operation without recycle of heavy ends. Product liquids were analyzed for microcarbon residue (MCR) and so that calculations could be made to determine the extent of "by passing" of the feed on its passage through the reactor.     As a basis for comparison to determine progress being made, a series of eight runs were made under a set of standard conditions. Bitumen feed rates employed ranged from 1.0 to 3.9 g/minute. Steam provided for fluidization and atomization varied from 6.3 to 9.1 g/min. and nitrogen flows were 3.4 L/min. Reaction temperatures ranged from 485 to 540 °C and calculated residence times from 0.50 to 0.64 seconds. Real liquid product yields ranged from 54.6 to 67.3% averaging 61.6%.     (ii) Bitumen-in-water emulsions were employed as feed to supply the bitumen as small particles (60 µm) to determine the effects on real liquid product yield. Operating conditions were similar to those described for the standard runs. The real liquid product yields surprisingly were significantly higher ranging from 64.0 to 73.8% averaging 69.6%. The cost and availability of the surfactant to prepare this emulsion on a commercial scale ruled out the possibility of using bitumen-in-water emulsions as feedstocks.   To simulate the small particle sizes observed in the bitumen-in-water emulsions and achieve higher real liquid product yields, hypodermic syringe needles (No. 17 and 18 gauge) were built into nozzles which were introduced through a side port to inject feed 5.5 cm below the surface of the fluid bed. With the No. 18 gauge needle and conditions similar to those in the standard runs, real liquid product yields ranging from 83.9 to 86.1% averaging 85.0% were obtained. Using the No. 17 gauge needle and feeding bitumen under similar conditions, real liquid product yields from 77.3 to 80.2%, averaging 79.0% were obtained demonstrating that particle size of the bitumen fed plays a major role in determining the real liquid product yield.     It was found that when the syringe needle nozzle was located further below the fluid bed surface, the real liquid product yield decreased to the low 70's, suggesting that longer residence time in the bed causes losses of liquid product in the form of additional coke and gas.     (iii) Steam flow rate as part of the feed mixture was found to have a marked effect if insufficient steam were present, causing significantly lower real liquid product yield, eg. 50.6%. However, 51 to 75% more steam than normally fed under standard conditions caused only minor increases in real liquid product yield.     Results from a riser pipe reactor feeding into a shallow fluidized bed disengaging zone gave real liquid product yields ranging from 78.2 to 83.9%. These results demonstrate that if the bitumen can be uniformly fed with coke in the riser pipe as small particles from a syringe needle (No. 18 gauge), the MCR values of the liquid product are relatively low, from 3.1 to 5.4%, and the extent of reaction is approximately the same as obtained when the bitumen is fed through a side port into the 2-inch I.D. reactor. In several respects the riser pipe reactor is considered similar to the commercial fluid coker in its mode of operation.