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CFD Modeling of Heaters
May 19, 2017 37
0 ft
Height in
Feet
19 ft
36 ft
50 ft
[ft/sec]
Existing Case
with Vertically Fired
Burners
Proposed Case
with Inclined Firing
System](https://image.slidesharecdn.com/firedheatersriceglobalfinal-170519204403/75/Fired-Heaters-Key-to-Efficient-Operation-of-Refineries-and-Petrochemicals-37-2048.jpg)
Uploaded byAshutosh Garg
Fired Heaters-Key to Efficient Operation of Refineries and Petrochemicals
Fired heaters are crucial in refinery and petrochemical processes, operating at high temperatures to achieve efficient heating for various applications. The document discusses the evolution, efficiency, and environmental impact of these heaters, highlighting advancements in design and technology to reduce emissions. Additionally, it addresses the challenges of energy consumption, coking, and presents strategies for improving heater performance and reducing air pollution.
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Fired Heaters-Key to Efficient Operation of Refineries and Petrochemicals
- 1. www.heatflux.com Fired Heaters Key toEfficient Operation of Refineries and Petrochemicals Ashutosh Garg Furnace Improvements Services Sugar Land, TX
- 2. www.heatflux.comMay 19, 20172 Typical Refinery Process Flow Diagram CRUDE OIL DISTILLATION FCC VACUUM DISTILLATION JET FUEL & DIESEL MID-DISTILLATE HYDROTREATING ASPHALT COKING PETROLEUM COKE LPG GASOLINE CYCLE OIL TO HYDROTREATING OR HYDROCRACKING GASOLINE ALKYKATION NAPHTHA HYDROTREATING GASOLINE ISOMERIZATION HYDROGEN LPG CATALYTIC REFORMING GASOLINE & AROMATICS JET FUEL & DIESEL HYDROCRACKING CRUDE OIL CDU HEATER COKER HEATER VDU HEATER REFORMER HEATER
- 3. www.heatflux.com Major Refinery BuildingBlock Majorly used in refinery processes which require very high temperatures Crude Unit – 650-750ºF Vacuum Unit – 700-800ºF Coker Unit – 950ºF Reforming Unit – 1000ºF Heating options- Steam Hot Oil/Molten Salts Electric 3May 19, 2017
- 4. www.heatflux.com Fired Heaters inPetrochemical Industry Most common petrochemical classes - Olefins & Aromatics Processes involved: Steam Cracking – To Produce Olefins (Using Ethane to Gas Oils), Propane Dehydro to produce Propylene Catalytic Reforming – To Produce Aromatics (Using Naphtha) Global Production Ethylene – 140 Million Tonnes Propylene – 100 Million Tonnes Aromatics – 85 Million Tonnes 4May 19, 2017
- 5. www.heatflux.com Steam Cracking May 19,2017 5 Natural Gas Processing Petroleum Refinery Raw Natural Gas Ethane Propane Butanes Methane Methane Ethylene Propylene Benzene Butadiene Byproducts Optional gas feeds Optional liquid feeds GasOil Naphtha Crude Oil BTX Produced by cracking any of the optional feeds Produced only by cracking any of the liquid feeds Benzene, Toluene Xylenes Steam Cracker polyesters engine coolant polyvinyl chloride polyol propylene glycol epoxy resins polyurethanes polystyrenes nylons 1600o F
- 6. www.heatflux.comMay 19, 20176 Steam Reforming 1500o F Steam ReformerDesulfurization Naphtha Natural Gas Fischer-Tropsch Synthesis Water-gas-shift Reaction Methanol Synthesis Hydrogen Ammonia Synthesis Ammonia Synthetic Fuels CH3OH Dimethylether Steam Synthetic Gas CO+H2
- 7. www.heatflux.comMay 19, 20177 Heat transfer modes Conduction-Solids Heat is transferred by direct contact between two objects Convection-Fluids Heat is transferred with in a medium due to movement of molecules Radiation Transmission of heat from a heated body by electromagnetic waves
- 8. www.heatflux.com Heat transfer requiresdifference in temperature of two bodies Flue gas Tube (Higher temperature) (Lower temperature) Heat transfer is proportional to temperature difference. 1,500 °F 800 °F
- 9. www.heatflux.com How is Heat Transferredto the Fluid? Direct Radiation from hot gases to tubes Re-radiation from refractory walls to tubes Convection from hot gases to tubes Conduction through wall of tubes Convection into process fluid TUBE CONVECTIVE HEAT TRANSFER RERADIATION REFRACTORY DIRECT RADIATION FLAME
- 10. www.heatflux.com Fired Heaters Evolution Developed in late 1800s for growing demand of petroleum products Earlier designs – Shell Still-Batch Process-unable to heat viscous liquids efficiently Led to development of tubular coil arrangements in 20th century Earlier designs were based on convection section heat transfer and flue gas recirculation May 19, 2017 10 Courtesy- Refinery Operations by Bill Berger
- 11. www.heatflux.com Courtesy- Refinery Operationsby Bill Berger
- 12. www.heatflux.com Fired Heaters Evolution May19, 2017 12 TO STACK TO STACK TO STACK TO STACK TO STACK TO STACK BURNERS BURNERS BURNERS BURNERS BURNERS BURNERS BURNERS (A) (F) (E) (D) (C)(B)
- 13. www.heatflux.com Fired Heater Evolution-2 May19, 2017 13 TO STACK BURNERS TO STACK BURNERS BURNERSBURNERS TO STACK BURNERS BURNERS BURNERS TO STACK TO STACK TO STACK (L)(K)(J)(I)(H)(G)
- 14. www.heatflux.com Fired Heater –Evolution Fired heaters- initially box type radiant shape with horizontal tubes and end wall fired burners Initially two rows of tubes backed by the refractory In 1950s, designs used single row of tubes New designs go for double fired tubes Vertical tube configuration with Vertical Cylindrical Radiant Section Vertical up fired burners 14May 19, 2017
- 15. www.heatflux.com Fired Heaters -Importance Major energy consumer High temperature Exposed to flames Major source of green house gases Major source of NOx emissions Coking of tubes Run length 15May 19, 2017
- 16. www.heatflux.com Fired Heaters inRefining Industry About 3000 Heaters in the USA Natural Draft Heaters- 89.6% Forced Draft Heaters-8% without APH Balanced Draft Heaters- 2.4% with APH Natural Draft Heater- 72 MMBtu/hr (Avg Size) Balanced Draft Heater-110 MMBtu/hr (Avg. Size) May 19, 2017 16
- 17. www.heatflux.com Heater Nomenclature Threemajor components Radiant Section Convection Section Stack Radiant / Convection split In refinery heaters, radiant section heat transfer is predominant (60-80%). In high temperature heaters the radiant heat duty drops down to 50% of the total duty. May 19, 2017 17 AIR AIR STACK CONVECTION RADIANT BURNER
- 18. www.heatflux.com Major Refinery Heaters Four major building blocks Atmospheric heater Vacuum heater Coker heater Catalytic Reforming heater May 19, 2017 18
- 19. www.heatflux.com Atmospheric Heater Crudeor topping heater Inlet temperature: 400-600°F Outlet temperature: 625-725°F Outlet pressure: 25 psig Pressure drop: 100-200 psi Typical run lengths: around 3-4 years Avg. Radiant heat flux:10,000-12,000 Btu/hr ft2 Coil material- 5 Cr -1/2 Mo CS for sweet crudes, low temp. service May 19, 2017 19 GAS SEPARATOR ATMOSPHERIC FRACTIONATION DESALTER Heavy naphtha Kerosene Light gas oil Heavy gas oil Crude oil Gas Gasoline Furnace Residuum Gas (butane and lighter) + Gasoline (light naphtha) Pump
- 20. www.heatflux.com Coker Heaters Convertsall the bottom of the barrel in to gases, naphtha and coke. Coke is shipped to other countries for burning in powerplants. Very popular high gasoline demand Endothermic reaction- heater supplying the heat 20May 19, 2017 Feed Pump Fractionator Coker Heater Gas Oil Stripper Steam C4 & Lighter Reflux Drum Naphtha Gas Oil Coke Drums Petroleum Coke DruminDecoking DruminOperation
- 21. www.heatflux.com Reformer- Furnace RadiantSection Fue Hydrocarbon Steam Reformed GasConvection Section Stack ID Fan Radiant Furnace Side Process Side Catalyst-Filled Tubes CCHH44 ++ HH2200 33HH22 ++ CCOO RReeffoorrmmiinngg SShhiifftt CCOO ++ HH2200 HH22 ++ CCOO22 l
- 22. www.heatflux.com Typical Operating Conditions Steam to Carbon Ratio of 2.5 to 4.5 Radiant section Temperature, in / out - 950/ 1560 F Pressure, in / out - 330/290 psig Radiant section efficiency: 45-50% Overall thermal efficiency: 88-92% Typical tube diameter-3-5 inches Typical lengths - 25-45 ft. High Chrome Nickel tubes 22May 19, 2017
- 23. www.heatflux.com Down Fired SteamReformer 23May 19, 2017 Pipe Support Inlet Pigtails Burner Pent House Observation Doors Flame Inlet Manifold Outlet Pigtails Tubes w catalyst
- 24. www.heatflux.com Pyrolysis-Cracking Furnaces Breakingthe molecule with fire or heat Heavier parafinnic hydrocarbons are heated to a high temperature at a low pressure to produce ethylene, propylene, butadiene etc. Tubular furnace in the presence of steam. 24May 19, 2017
- 25. www.heatflux.com Historical data forcracking heaters Year 1940 1970 1990 Max TMT 1400 F 1950 F 2050 Avg. Flux 14400 25000 30000 Tube Matl 321 H Cast 310 3545Cr Ni Arrngmt. Horizontal Vertical Vertical Burners Wall&Roof Floor& side Floor Heater Size 30 MMBtu 200 MMBtu 400 MMBtu
- 26. www.heatflux.com Furnace Configuration Verticalcoils fired from both sides Tubes are supported from top by spring hangers Burners are located on floor and side walls Radiant flux density, Btu/hr ft2 Ethane /Propane - 20,000-26,000 Naphtha - 24,000-30,000 26May 19, 2017 STACK DAMPER CONVECTION SECTION RADIANT SECTION TO TLX ECONOMIZER FEED PREHEATER HP STEAM SUPER HEATER MIXED FEED PREHEATER ID FAN Floor Fired
- 27. www.heatflux.com Air Pollution byFired Heaters Nitrogen Oxides 50% of total NOx emissions are from industrial processes 2 types of NOx produced: • Fuel NOx (due to fuel bound nitrogen) • Thermal NOx (due to high temperature) May 19, 2017 27
- 28. www.heatflux.com Air Pollution byFired Heaters Carbon Dioxide Generally 200,000 BPD capacity refinery emits 1.5 million tons/year of CO2 (2/3rd is from Fired Heaters) Carbon monoxide produced by incomplete combustion EPA limit is 50 ppmvd Sulfur Oxides By-products of combustion Fuel gas contains upto 160 ppm of H2S Others– trace amounts of VOCs, PM10 and PM2.5 May 19, 2017 28
- 29. www.heatflux.com Typical NOx emissions Gas firing- 0.05-0.2 lb./MMBtu Oil firing-0.2-0.4 lb./MMBtu A 100 MMBtu/hr gas fired heater will emit approx..... 5.5-22 lb./hr or 20 -80 tons /year. A typical refinery having 40 heaters will be emitting approx......--- 8,00-3,200 tons/year. 19 May 2017 29
- 30. www.heatflux.com Low NOx/ UltraLow Burners Low NOx Burner Development History 0 50 100 150 Standard Staged air Staged fuel Internal Flue gas recirculation New Generation1984 1986 1992 2001
- 31. www.heatflux.com Selective Catalytic ReductionSystems Nitrogen Oxides are reduced to Nitrogen by of Ammonia in the presence of catalyst. First tried out in Japan in 1963 First commercial installation began in 1978. Most proven technology for reduction of NOx ( can accomplish greater than 95% reduction) May 19, 2017 31 FIRED HEATER BURNERS STACK DAMPER WASTE HEAT RECOVERY UNIT CATALYST BED AMMONIA INJECTION GRID INDUCED DRAFT FAN
- 32. www.heatflux.com How to reduceair pollution Improving heat recovery in the heat exchangers to minimize the heat duty Improving fired heater efficiency to 90+% to minimize the fuel firing Car pooling/Electric Cars 32May 19, 2017
- 33. www.heatflux.com Coking in Tubes Coke deposits on the inside of heater tubes Pressure drop goes up High tube metal temperature Exceeds design limit- time for decoking Run length 9-12 months How to clean the tubes? Pigging vs. decoking vs. on-line spalling 33May 19, 2017
- 34. www.heatflux.com Energy Consumption TypicalRefinery 44 MMBtu/ BBL of oil 67% of the energy used in Fired heaters 134,000 BPD ( Average Size) Fuel Cost-$3/MMBtu Energy Bill $4.32 Billion/Year Efficiency improvement 1%= 43.2 Million Dollars A dollar saved is a dollar earned. May 19, 2017 34
- 35. www.heatflux.com Fired Heaters EfficiencyImprovement Fired Heaters Efficiency can be improved by: Installing Air preheater Waste Heat Steam Generator Efficiency improvement potential of 8-15% Low energy prices do not provide good payback May 19, 2017 35 COLD AIR HOTAIR FD FAN ID FAN HOT FLUE GAS COLD FLUE GAS RADIANT SECTION BURNER CONVECTION SECTION DAMPER WITH ACTUATOR STACK AIR PREHEATER
- 36. www.heatflux.com New Developments Betterdesign correlations- still using 70 years old design methods CFD Modeling of the burners and heaters Better materials for tubes and refractory Better flue gas analyzers Better burner management systems and controls IIoT-Industrial Internet of Things Sensors Advanced analytical capabilities 36May 19, 2017
- 37. www.heatflux.com CFD Modeling ofHeaters May 19, 2017 37 0 ft Height in Feet 19 ft 36 ft 50 ft [ft/sec] Existing Case with Vertically Fired Burners Proposed Case with Inclined Firing System
- 38.