Presentation is loading. Please wait.

Presentation is loading. Please wait.

Fluid Catalytic Cracking (FCC) Quak Foo, Lee Chemical and Biological Engineering The University of British Columbia.

Similar presentations


Presentation on theme: "Fluid Catalytic Cracking (FCC) Quak Foo, Lee Chemical and Biological Engineering The University of British Columbia."— Presentation transcript:

1 Fluid Catalytic Cracking (FCC) Quak Foo, Lee Chemical and Biological Engineering The University of British Columbia

2 Outline What is FCC? What is FCC? Why use circulating Fluidized Bed Reactor in FCC? Why use circulating Fluidized Bed Reactor in FCC? Operating Characteristics Operating Characteristics Description of the Process Description of the Process Heat Balance Heat Balance Pressure Balance Pressure Balance Conclusions Conclusions

3 What is FCC? Primary conversion process in petroleum refinery. Primary conversion process in petroleum refinery. The unit which utilizes a micro-spherodial catalyst (zeolitic catalyst) which fluidizes when properly aerated. The unit which utilizes a micro-spherodial catalyst (zeolitic catalyst) which fluidizes when properly aerated. The purpose is to convert high-boiling petroleum fractions (gas oil) to high-value, high-octane gasoline and heating oil. The purpose is to convert high-boiling petroleum fractions (gas oil) to high-value, high-octane gasoline and heating oil.

4 Why use Circulating Fluidized Bed in FCC? Compared with Fixed Bed, Fluidized Bed Compared with Fixed Bed, Fluidized Bed CFB – fast fluidization regime CFB – fast fluidization regime CFB good for catalyst size < 0.2 mm CFB good for catalyst size < 0.2 mm Excellent in: Excellent in: –Gas-solid effective contact –Catalyst effectiveness –Catalyst internal temperature control –Catalyst regeneration

5 Operating Characteristics Particle Diameter = 150 m Particle Diameter = 150 m Geldart Classification = A Geldart Classification = A Temperature = 650 0 C Temperature = 650 0 C Pressure = 100 kPa Pressure = 100 kPa Superficial gas velocity = 10 m/s Superficial gas velocity = 10 m/s Bed depth = 0.85 m Bed depth = 0.85 m Fresh feed flow rate = 300,000 kg/hr Fresh feed flow rate = 300,000 kg/hr Catalyst to oil ratio = 4.8 Catalyst to oil ratio = 4.8

6 FCC Reactor-Regenerator

7 Description of the Process Reactor Reactor Riser Riser Cyclones Cyclones Stripper Stripper Regenerator Regenerator Standpipe and Slide Valve Standpipe and Slide Valve

8 Reactor Performance Feed oil enters the riser near the base Feed oil enters the riser near the base Contacts the incoming regenerated catalyst Contacts the incoming regenerated catalyst Cracking reactions occur in the vapor phase Cracking reactions occur in the vapor phase Expanded volume of vapors lift the catalyst and vaporized oil rises Expanded volume of vapors lift the catalyst and vaporized oil rises Fast reaction, few seconds of contact time Fast reaction, few seconds of contact time

9 Riser Dimensions Dimensions –Diameter: 1.2 m (4 ft) –Height : 36.6 m (120 ft) Plug flow with minimum back-mixing Plug flow with minimum back-mixing Steam is used to atomize the feed Steam is used to atomize the feed –Increases the availability of feed Outlet vapor velocity: 18 m/s (60 ft/sec) Outlet vapor velocity: 18 m/s (60 ft/sec) Hydrocarbon residence time: 2 seconds Hydrocarbon residence time: 2 seconds

10 Cyclones Located at the end of riser to separate the bulk of the catalyst from the vapor Located at the end of riser to separate the bulk of the catalyst from the vapor Use a deflector device to turn catalyst direction downward Use a deflector device to turn catalyst direction downward Two-stage cyclones Two-stage cyclones –To separate the remaining of the catalyst Return the catalyst to the stripper through the diplegs Return the catalyst to the stripper through the diplegs The product vapors exit the cyclones and flow to the main fractionator column The product vapors exit the cyclones and flow to the main fractionator column

11 Cyclones Riser Stripping Bed

12 Stripping Section The spent catalysts falls into the stripper The spent catalysts falls into the stripper Valuable hydrocarbons are absorbed within the catalyst bed Valuable hydrocarbons are absorbed within the catalyst bed Stripping steam, at a rate of 4 kg per 1000 kg of circulating catalyst, is used to strip the hydrocarbons from the catalyst Stripping steam, at a rate of 4 kg per 1000 kg of circulating catalyst, is used to strip the hydrocarbons from the catalyst The catalyst level provides the pressure head which allows the catalyst to flow into the regenerator The catalyst level provides the pressure head which allows the catalyst to flow into the regenerator

13 Inside Stripping Section Steam Reactor Stripper Catalyst Level Reactor Riser

14 Regenerator Two functions: Two functions: –Restores catalyst activity –Supplies heat to crack the feed Air is the source of oxygen for the combustion of coke Air is the source of oxygen for the combustion of coke The air blower with 1m/s (3 ft/s) air velocity to maintain the catalyst bed in a fluidized state The air blower with 1m/s (3 ft/s) air velocity to maintain the catalyst bed in a fluidized state 14 kPa (2 psi) pressure drop in air distributors to ensure positive air flow through all nozzles 14 kPa (2 psi) pressure drop in air distributors to ensure positive air flow through all nozzles

15 Inside Regenerator Inside Regenerator Catalyst (low carbon) Catalyst (high carbon) High Oxygen Low Oxygen Dense Phase Bed Catalyst Air

16 Standpipe & Slide Valve Standpipe provides the necessary pressure head needed to circulate the catalyst around the unit Standpipe provides the necessary pressure head needed to circulate the catalyst around the unit The catalyst density in standpipe is 642 kg/m 3 (40 lbs/ft 3 ) The catalyst density in standpipe is 642 kg/m 3 (40 lbs/ft 3 ) Slide valve is used to regulate the flow rate of the regenerated catalyst to the riser Slide valve is used to regulate the flow rate of the regenerated catalyst to the riser Slide valve function is to supply enough catalyst to heat the feed and achieve the desired reactor temperature Slide valve function is to supply enough catalyst to heat the feed and achieve the desired reactor temperature

17 Heat Balance A catalyst cracker continually adjusts itself to stay in heat balance. A catalyst cracker continually adjusts itself to stay in heat balance. The reactor and regenerator heat flows must be equal. The reactor and regenerator heat flows must be equal. Heat balance performed around Heat balance performed around –the reactor –the stripper-regenerator Use to calculate catalyst circulation rate and catalyst-to-oil ratio Use to calculate catalyst circulation rate and catalyst-to-oil ratio –overall heat balance

18 Heat Balance The unit produces and burns enough coke to provide energy to: The unit produces and burns enough coke to provide energy to: –Increase the temperature of the fresh feed, recycle, and atomizing steam from their preheated states to the reactor temperature. –Provide the endothermic heat of cracking. –Increase the temperature of the combustion air from the blower discharge temperature to the regenerator flue gas temperature. –Make up for heat losses from the reactor and regenerator to surroundings. –Provide for heat sinks, such as stripping steam and catalyst cooling.

19 FCC Heat Balance RegeneratorReactor Spent CatalystFlue gas Heat losses Regeneration Air Feed Preheater Recycle Fresh Feed Products Heat Losses Heat of Coke Combustion Heat of Reaction Regenerated Catalyst

20 FCC Heat Balance RegeneratorReactor Spent CatalystFlue gas Heat losses Regeneration Air Feed Preheater Recycle Fresh Feed Products Heat Losses Heat of Coke Combustion Heat of Reaction Regenerated Catalyst

21 Heat Balance Around Stripper-Regenerator Heat to raise air from the blower discharge temperature to the regenerator dense phase temperature. (108 10 6 Btu/hr) Heat to raise air from the blower discharge temperature to the regenerator dense phase temperature. (108 10 6 Btu/hr) Heat to desorb the coke from the spent catalyst. (39.5 10 6 Btu/hr) Heat to desorb the coke from the spent catalyst. (39.5 10 6 Btu/hr) Heat to raise the temperature of the stripping steam to the reactor temperature. (4.4 10 6 Btu/hr) Heat to raise the temperature of the stripping steam to the reactor temperature. (4.4 10 6 Btu/hr) Heat to raise the coke on the catalyst from the reactor T to the regenerator dense phase T. (3.7 10 6 Btu/hr) Heat to raise the coke on the catalyst from the reactor T to the regenerator dense phase T. (3.7 10 6 Btu/hr)

22 Heat Balance Around Stripper-Regenerator Heat to raise the coke products from the regenerator dense temperature to flue gas temperature. (2.17 10 6 Btu/hr) Heat to raise the coke products from the regenerator dense temperature to flue gas temperature. (2.17 10 6 Btu/hr) Heat to compensate for regenerator heat losses. ( 19.3 10 6 Btu/hr) Heat to compensate for regenerator heat losses. ( 19.3 10 6 Btu/hr) Heat to raise the spent catalyst from the reactor temperature to the regenerator dense phase. (305.5 10 6 Btu/hr) Heat to raise the spent catalyst from the reactor temperature to the regenerator dense phase. (305.5 10 6 Btu/hr)

23 Reactor Heat Balance Hot-regenerated catalyst supplies the bulk of the heat required to vaporize the liquid feed Hot-regenerated catalyst supplies the bulk of the heat required to vaporize the liquid feed To provide the overall endothermic heat of cracking To provide the overall endothermic heat of cracking To raise the temperature of dispersion steam and inert gases to the reactor temperature To raise the temperature of dispersion steam and inert gases to the reactor temperature

24 Reactor Heat Balance Heat into the reactor Heat into the reactor –Regenerated catalyst = 1186 10 6 Btu/hr –Fresh feed = 267 10 6 Btu/hr –Atomizing steam = 12 10 6 Btu/hr –Heat of absorption = 35 10 6 Btu/hr Total heat in = 1500 10 6 Btu/hr Total heat in = 1500 10 6 Btu/hr

25 Reactor Heat Balance Heat out of the reactor Heat out of the reactor –Spent catalyst = 880 10 6 Btu/hr –To vaporize feed = 513 10 6 Btu/hr –Heat content of steam = 15 10 6 Btu/hr –Loss to surroundings = 6 10 6 Btu/hr –Heat of reaction = ? Total heat out = 1414 10 6 Btu/hr + Heat of reaction Total heat out = 1414 10 6 Btu/hr + Heat of reaction

26 Reaction Heat Balance Calculation of Heat of Reaction Calculation of Heat of Reaction Total heat out = Total heat in Total heat out = Total heat in Total heat in = 1500 10 6 Btu/hr Total heat in = 1500 10 6 Btu/hr Total heat out = 1414 10 6 Btu/hr + Heat of reaction Total heat out = 1414 10 6 Btu/hr + Heat of reaction Therefore, Overall Endothermic Heat of Reaction = 86 10 6 Btu/hr Therefore, Overall Endothermic Heat of Reaction = 86 10 6 Btu/hr

27 Pressure Balance Deals with the hydraulics of catalyst circulation in the reactor and regenerator circuit. Deals with the hydraulics of catalyst circulation in the reactor and regenerator circuit. The incremental capacity come from increased catalyst circulation or from altering the differential pressure between reactor-regenerator. The incremental capacity come from increased catalyst circulation or from altering the differential pressure between reactor-regenerator.

28 Pressure Balance Results In spent catalyst standpipe: In spent catalyst standpipe: –Pressure buildup = 27 kPa (4 psi) –Catalyst density = 658 kg/m 3 –Optimum pressure to circulate more catalyst In regenerated catalyst standpipe: In regenerated catalyst standpipe: –Pressure buildup = 55 kPa (8 psi) –Catalyst density = 642 kg/m 3

29 Conclusions Circulating Fluidized Bed is used in FCC unit. Circulating Fluidized Bed is used in FCC unit. Stripping steam of 4 kg per 1000 kg circulating catalyst is required. Stripping steam of 4 kg per 1000 kg circulating catalyst is required. Overall endothermic Heat of Reaction is 86 MBtu/hr. Overall endothermic Heat of Reaction is 86 MBtu/hr. Pressure buildup in spent catalyst standpipe is 27 kPa (4 psi). Pressure buildup in spent catalyst standpipe is 27 kPa (4 psi). Pressure buildup in regenerated catalyst standpipe is 55 kPa (8 psi). Pressure buildup in regenerated catalyst standpipe is 55 kPa (8 psi).


Download ppt "Fluid Catalytic Cracking (FCC) Quak Foo, Lee Chemical and Biological Engineering The University of British Columbia."

Similar presentations


Ads by Google