A.FLUID CATALYTIC CRACKING/a.PROCESS(Contd.)
Q3 With the shift toward greater utilization of “opportunity crudes “ such as Canadian synthetic crudes,what shifts do you expect in FCC product yield and quality and how this will this impact the operation of the FCC unit?
A3.With the shift toward “opportunity’’crudes,FCC feedstocks are becoming”heavier’’,which lowers API,and are increasingly derived from Canadian synthetic crudes and bitumen blends.While sweet synthetic blends make up the majority of Canadian bitumen derived crudes on the market,some sour synthetic,bitumen and condensate blends (Dilbits,SynBit,SynDilBit)are also available.Processing implications for the FCC refinery will be a function of the type of bitumen-derived crude imported and should be evaluated on a case to case basis.However general trends can be drawn based on the compositional differences between conventional refinery feeds and these “opportunity crudes’’.
Compared to conventional crude oil,synthetic crude oil(SCO)provides a larger volume of FCC feedstock with no residue and low total sulfur,nitrogen and metals.with a large aromatic content.On the other hand.Canadian bitumen contains a larger volume of highly aromatic 650F+material,lower API gravity,lower hydrogen content and higher levels of sulfur,nitrogen,nickel,and vanadium.The central issue is the high throughputs required to
process the additional fed that is of poorer quality.
Refiners will see a significant shift in the FCC yield pattern when processing vacuum gas oils from most bitumen -derived crudes.The aromatic nature of SCOs limits FCC bottoms
conversion with an increase in decant oil and light cycle oils yields.Other differences will be observed in the decrease of yield,especially naphtha and LPG,and quality of valuable products,with higher sulfur content in the naphtha and LCO cuts,and an increase in the levels of coke precursors and reactor coking for heavier feedstocks.Also,the LCO produced will have low cetane number due toits high aromatic content.To a certain extent yield improvements are possible with an increase in the catalyst to oil ratio,which can produce pressure balance issues,standpipe and slidevalve sizing increases,and the need to improve/debottleneck the catalyst stripper.The large percentage of VGO-range material in these unconventional crudes may result unit capacity becoming a bottleneck.A higher unit throughput can be accomplished at a high reactor severity,but this would be limited by FCC hardware constraints.All the above-the contaminant levels,composition of bitumen -derived crudes and high feed volumes-make these opoertunity crudes more challengingto upgrade into cleaner fuels and development of tailored FCC catalyst technology playing a key role in addressing these challenges
Q3 With the shift toward greater utilization of “opportunity crudes “ such as Canadian synthetic crudes,what shifts do you expect in FCC product yield and quality and how this will this impact the operation of the FCC unit?
A3.With the shift toward “opportunity’’crudes,FCC feedstocks are becoming”heavier’’,which lowers API,and are increasingly derived from Canadian synthetic crudes and bitumen blends.While sweet synthetic blends make up the majority of Canadian bitumen derived crudes on the market,some sour synthetic,bitumen and condensate blends (Dilbits,SynBit,SynDilBit)are also available.Processing implications for the FCC refinery will be a function of the type of bitumen-derived crude imported and should be evaluated on a case to case basis.However general trends can be drawn based on the compositional differences between conventional refinery feeds and these “opportunity crudes’’.
Compared to conventional crude oil,synthetic crude oil(SCO)provides a larger volume of FCC feedstock with no residue and low total sulfur,nitrogen and metals.with a large aromatic content.On the other hand.Canadian bitumen contains a larger volume of highly aromatic 650F+material,lower API gravity,lower hydrogen content and higher levels of sulfur,nitrogen,nickel,and vanadium.The central issue is the high throughputs required to
process the additional fed that is of poorer quality.
Refiners will see a significant shift in the FCC yield pattern when processing vacuum gas oils from most bitumen -derived crudes.The aromatic nature of SCOs limits FCC bottoms
conversion with an increase in decant oil and light cycle oils yields.Other differences will be observed in the decrease of yield,especially naphtha and LPG,and quality of valuable products,with higher sulfur content in the naphtha and LCO cuts,and an increase in the levels of coke precursors and reactor coking for heavier feedstocks.Also,the LCO produced will have low cetane number due toits high aromatic content.To a certain extent yield improvements are possible with an increase in the catalyst to oil ratio,which can produce pressure balance issues,standpipe and slidevalve sizing increases,and the need to improve/debottleneck the catalyst stripper.The large percentage of VGO-range material in these unconventional crudes may result unit capacity becoming a bottleneck.A higher unit throughput can be accomplished at a high reactor severity,but this would be limited by FCC hardware constraints.All the above-the contaminant levels,composition of bitumen -derived crudes and high feed volumes-make these opoertunity crudes more challengingto upgrade into cleaner fuels and development of tailored FCC catalyst technology playing a key role in addressing these challenges
