Slide 1

New Approach to Optimizing Fired Heaters Ashutosh Garg, Furnace Improvements Sugar Land Texas, USA Slide 2 Energy Consumption Petroleum Refining 7.5% of the total energy consumption in USA 0.40 MMBtu/ BBL of oil Total Energy consumed in refining- 7.1 Quadrillion BTU/yr Energy cost -$6/MMBtu Total Energy Cost- 42 Billion /yr Fired heaters -40-70% of the energy Slide 3 Energy Consumption A Typical refinery process 100,000 BPD Consumption of 0.40 MMBTU/BBL $6 per MMBTU Energy bill of $ 87.6 million per year. Potential Saving 1% Efficiency improve $876,000/Year Slide 4 Fired Heaters Essential component in Petrochemical and Chemical Plants Each refinery has 20-50 fired heaters Design efficiency - 70-90% Operating efficiency is even less than design. Slide 5 Maintaining Design Operation Maintain the design conditions (very difficult) In the field, heater loads change constantly due to variations in: Feed flow rate Feed temperature Fuel composition Ambient temperature The heater will be operating a non-optimal conditions Requires optimization 24/7 Slide 6 How to Maintain the Design Efficiency? When the heater conditions change, adjustments in the heater are required. Manual adjustments are provided- not adequate Optimizing the fired heater will: Reduce Energy Consumption Increase run length Minimize maintenance FIS has proposed two prong approach Software based- Heater Performance Index Hardware based- Draft & Excess O2 Control Slide 7 Fired Heater Heat liberated by the combustion of fuels is transferred to fluids contained in coils Fired Heater: Radiant Section Convection Section Stack www.heatflux.com Slide 8 Typical heater efficiency Natural Draft- 70-84% Balance Draft-90-92% Natural Draft heaters in Industry- 86% Balanced Draft heaters in Industy-12% Typical stack temperature 500-800 F Typical stack Oxygen- 2-10% Target Oxygen-2-3% Plenty of room for optimization Slide 9 Combustion Combustion Requires Air ( 0.21O 2 + 0.79 N 2 ) Fuel Ignition source Complete Combustion Excess air Incomplete Combustion Energy Loss CO and H 2 are released Slide 10 Draft Pressure inside the heater Combustion air is drawn inside the heater through the burners air register Hot Flue gas flows out of the heater through the stack Types of Draft Natural Draft (ND)> 80% Forced Draft (FD) < 1% Induced Draft (ID) 10% Balanced Draft 10% Slide 11 Draft Stack Dampers helps control the draft Arch is the highest pressure point in the heater Excess or shortage of draft is not acceptable Slide 12 Burner Operation Correct combustion in firebox include: The firebox is clear No smoky appearance Burners flames are steady and well-formed Check burners regularly Adjusting burner registers to control air intake Slide 13 Air Leakages Air entering in to furnace from a number of places: Peepholes Header box doors Tube guide opening Feed tubes entering and exits Not pressure tight structure Slide 14 Heater Optimization Target set 2-3% O2 in the flue gas. Operating conditions fluctuates : Manual control /adjustments Operators Number going down Experience going down Need training Slide 15 Optimisation Case Study -1 FIS performed a tuning job for a refinery. Heater: Depentanizer reboiler heater Horizontal tube box Absorbed heat duty - 87 MMBtu/hr 15 up fired burners The stacks is connected to a large common stack Two off take ducts provided with manual dampers Slide 16 Optimisation Approach Check draft Adjust using off-take dampers Check excess O2 Adjust burner register Check burners Light up all burners Check Flames/Firebox Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Crude Heater Tuning Case Study -2 Natural Draft Crude Heater Horizontal tube Up-fired burners 11 burners Slide 22 Before & After Tuning Fuel gas flow, MSCFD Fuel gas pressure, psig Fuel gas Flow and Pressure Slide 23 Before & After Tuning Tube Skin Temp Slide 24 Recommendations Furnace working off design conditions Poor quality of dampers Lower number of operators Operator without sufficient training Software Heater Performance Index (HPI) Hardware Draft control system Excess O2 control system Observations in Refineries Slide 25 Heater Performance Index Analyzes the performance of Fired Heater 24/7 Built into DCS Generates guidelines Built in intelligence Customized modeling Thermal Efficiency Fuel gas rate, Draft, Excess O2, Tube skin temperatures, Feed flow rate, Pressure drop, Coking rate, Air preheater performance Slide 26 Crude Flow Rates TAG No.SERVICEUNITS SET POINT 8/15/20098/16/20098/17/2009 Data 1Data 2Data 3 PROCESS 57FC0009.PVTotal Crude FlowBPH4337.65249.14807.34637.7 57FC0001.PVCrude Flow to Pass 1BPH542.2709.5711.6668.0 57FC0002.PVCrude Flow to Pass 2BPH542.2676.5725.0 57FC0003.PVCrude Flow to Pass 3BPH542.2670.8671.1635.6 57FC0004.PVCrude Flow to Pass 4BPH542.2729.1731.1686.3 57FC0005.PVCrude Flow to Pass 5BPH542.2729.1731.2686.3 57FC0006.PVCrude Flow to Pass 6BPH542.2695.1710.1680.2 57FC0007.PVCrude Flow to Pass 7BPH542.2737.4743.8711.8 AverageBPH542.2706.7717.7684.7 Slide 27 Coil Inlet Pressure TAG No.SERVICEUNITS SET POINT 8/15/20098/16/20098/17/2009 Data 1Data 2Data 3 PROCESS 57PI0054.PV Crude Inlet Pressure (Pass 1)psig147.9278.9287.4286.0 57PI0055.PV Crude Inlet Pressure (Pass 2)psig147.9296.0309.6309.8 57PI0056.PV Crude Inlet Pressure (Pass 3)psig147.9275.9282.8284.8 57PI0057.PV Crude Inlet Pressure (Pass 4)psig147.9286.0294.8293.0 57PI0058.PV Crude Inlet Pressure (Pass 5)psig147.9281.7290.4288.7 57PI0059.PV Crude Inlet Pressure (Pass 6)psig147.9283.8292.4290.2 57PI0060.PV Crude Inlet Pressure (Pass 7)psig147.9298.2310.0306.8 Averagepsig147.9285.7295.3294.1 Slide 28 Fluids Cross-over Temperatures. TAG No.SERVICEUNITS SET POINT 8/15/20098/16/20098/17/2009 Data 1Data 2Data 3 PROCESS 57TI0583 Crude Inlet Temperature oFoF542557.2553.8555.3 57TI0590 Cross-over Temp. (Pass-1) oFoF610585.1581.9583.6 57TI0591 Cross-over Temp. (Pass-2) oFoF610589.7586.9587.9 57TI0592 Cross-over Temp. (Pass-3) oFoF610592.0589.4590.3 57TI0593 Cross-over Temp. (Pass-4) oFoF610597.1594.2595.8 57TI0618 Cross-over Temp. (Pass-5) oFoF610594.5591.9593.2 57TI0619 Cross-over Temp. (Pass-6) oFoF610590.9588.4589.7 57TI0620 Cross-over Temp. (Pass-7) oFoF610594.4591.1593.0 AVERAGE Cross-over Temp. oFoF610.0590.9588.0589.4 Slide 29 Coil Outlet Temperatures TAG No.SERVICEUNITS SET POINT 8/15/20098/16/20098/17/2009 Data 1Data 2Data 3 PROCESS 57TI0633 Coil Outlet Temp. (Pass 1) oFoF730686.8687.0687.4 57TI0634 Coil Outlet Temp. (Pass 2) oFoF730678.6678.3677.5 57TI0635 Coil Outlet Temp. (Pass 3) oFoF730680.2680.6679.0 57TI0636 Coil Outlet Temp. (Pass 4) oFoF730678.5678.6679.9 57TI0629 Coil Outlet Temp. (Pass 5) oFoF730683.4683.5683.7 57TI0630 Coil Outlet Temp. (Pass 6) oFoF730670.1670.0670.9 57TI0631 Coil Outlet Temp. (Pass 7) oFoF730683.0682.2683.3 AVERAGE Coil Outlet Temp. oFoF730.0679.9 680.1 Slide 30 Heater Performance Index. Remarks Slide 31 Slide 32 Heater Performance IndexHeater Performance Index Slide 33 Oxygen & Draft Control System (Natural Draft Heater) Slide 34 Draft Control System Slide 35 Stack dampers Reliable Correctly sized Pneumatically operated Opposed blades Slide 36 Reliable Dampers Opposed blades vs. Parallel Blades Slide 37 Excess O2 Control Control air supply to burners Pneumatically operated dampers or registers Provide proper control scheme Damper opening is provided based on Draft Excess O2 Firing rate Other parameters Savings realized through out the day Slide 38 Summary Manual controls are not adequate Energy prices are high Advanced Controls possible Use DCS based or PLC based Provide adequate safe guards Intelligent analysis of heater parameters Substantial savings can be realized Payout will be less than a year in most cases Slide 39 Thank you very much Questions and comments are welcome