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Process Heating

Process Heating

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Process Heating

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  1. Process Heating Technology - Concept

  2. Types of Energy Used for Industrial Heating US DOE – Industries of the Future Workshop Series

  3. Process Heating Demand by Industry US DOE – Industries of the Future Workshop Series

  4. Industrial Process Heating Methods • Fuel Fired Heating • Direct Fired • Indirect Fired • Radiant Tubes • Muffle • Steam Heating • Indirect (heat exchanger, jacketed tank) • Direct injection • Hot Oil/Air/Water Heating • Electrical Heating • Arc Heating/Melting • Resistance • Induction • Other (Laser, E. Beam, etc) US DOE – Industries of the Future Workshop Series

  5. Examples of Process Heating Furnaces • Oxygen Furnace • Heating supplied by blowing oxygen into molten iron • Crucible Furnace • Heating supplied by gas fired circular furnace • Blast Furnace • Iron ore, coke and limestone are dumped into the top, and preheated air is blown into the bottom • Cupola Furnace • Burns coke with an air blast to melt scrap steel Figure: Oxygen Furnace US DOE – Industries of the Future Workshop Series

  6. Examples of Process Heating Systems (cont.) • Induction Heating • Induced electrical currents within the material produces heat • High-Frequency Resistance Heating • High frequency current passed between the power contacts heats up the narrow strip of workpiece surface • Electric Arc Furnace • Electric current is passed through electrodes in the lid to form an arc, which generates heat and melts the cold scrap. • Continuous Casting • Molten steel is cast directly into semifinished shapes Figure: Induction Furnace US DOE – Industries of the Future Workshop Series

  7. Save energy (5-30%) • Improve process control • Minimize safety hazards • Eliminate maintenance crises $$$ Why make a change? Great energy & cost savings potential! US DOE – Industries of the Future Workshop Series

  8. Why make a change? • Losses • 10-25 % of total heat supplied lost through enclosure • 20-70 % of total heat input contained in flue gases • 5-20 % of heat input lost through water-cooling of equipment • Costs • 2-15% of total product cost is due to process heating energy costs • Efficiency • Overall thermal efficiency of process equipment is 15-80 % • Greatest potential lies in higher temperature ranges • Properly Designed and Applied Sensors and Control Systems can lead to 5-30% energy savings! US DOE – Industries of the Future Workshop Series

  9. Technology – Common System Improvements

  10. Areas for Improving Process Heating • Heat Generation • Heat Transfer • Heat Containment • Waste Heat (Energy) Recovery • Sensors and Controls US DOE – Industries of the Future Workshop Series

  11. Components of Process Heating Systems US DOE – Industries of the Future Workshop Series

  12. Air/Fuel Ratio – Combustion Efficiency • In theory . . . PERFECT COMBUSTION AIR (O2 & N2) EXHAUST (CO2, H2O & N2) FUEL (C2H) US DOE – Industries of the Future Workshop Series

  13. Air/Fuel Ratio – Combustion Efficiency • In the real world . . . • Excess air introduced to prevent incomplete combustion AIR (O2 & N2) Combustion AIR (O2 & N2) EXCESS O2 EXHAUST (CO2, H2O & N2) FUEL (C2H) • Left over oxygen carries heat away from boiler US DOE – Industries of the Future Workshop Series

  14. Process Heating Exercises – Air/Fuel Ratio • Optimum combustion air = increased efficiency • Too much air = excess heat loss in stack • Too little air = wasted fuel • Worksheet example (use combustion chart on next slide): US DOE – Industries of the Future Workshop Series

  15. Process Heating Exercises – Air/Fuel Ratio Net Stack Temp = Stack temp reading – ambient air temp US DOE – Industries of the Future Workshop Series

  16. More Combustion Issues • Primary Air • Systems that introduce air to a burner before combustion • Described as a percent of total theoretical air required • E.g. 70% primary air mixture has 7 cubic feet of air mixed with 1 cubic foot of natural gas. The balance of air required to complete combustion, 3 cubic feet, would be secondary air • Secondary Air • Air mixed after ignition if all of the required air is not supplied before combustion • Flame Geometry • Controlled by the percentage of primary aeration US DOE – Industries of the Future Workshop Series

  17. Gas/Air Ratio Control Methods • Valve Control • Controlled using tandem valves linked together with constant pressure source for both fuel and air • Pressure Control • Controlled with constant area (burner orifices) and variable fuel and air pressures • Flow Control • Hydraulic or electronic flow control, measures air and fuel flow and controls the flow of one to match the other through pressure differentials US DOE – Industries of the Future Workshop Series

  18. Heat Generation Opportunities • Efficient Combustion • Use of Preheated Combustion Air • Use of Oxygen-Enriched Air or Oxygen for Combustion US DOE – Industries of the Future Workshop Series

  19. Heat Transfer Opportunities • Improve Fluid Circulation • Use of Fans for Increasing Convection Heat Transfer and Improved Work Temperature Uniformity • Induction Furnaces • Use of Proper Temperature Settings and Heating Cycles to Minimize Soak Time • Optical (infrared) temperature scanners • Replace Indirect Heating where Possible US DOE – Industries of the Future Workshop Series

  20. Heat Containment Opportunities • Use of Optimum and Adequate Insulation for Heating Equipment Walls • Regular inspection, repair, and maintenance of insulation for heating equipment • Minimize Heat Loss in Water-Cooled Parts • Control outlet temperature, use insulation for water-cooled parts • Control Furnace Openings • Eliminate or reduce furnace openings, provide heat shields to reduce heat losses from stacks, furnace openings, doors • Seals around Doors • Eliminate air or hot gas leakage, ensure that doors are sealed US DOE – Industries of the Future Workshop Series

  21. Waste Heat Recovery Opportunities • Install Waste Heat Recuperator for Combustion Air Preheating for Fuel Fired Furnaces • Incorporate Load Preheating for Furnaces if Possible • Cascade Heating from High Temperature Processes to Lower Temperature Processes • Recover Heat from Flue Gases through Water Heating, Steam Generation, or Load Preheating US DOE – Industries of the Future Workshop Series

  22. Preheated Combustion Air US DOE – Industries of the Future Workshop Series

  23. Sensors and Control Opportunities • Furnace Internal Pressure Control • Manual or automatic exhaust damper • Sensors and Controls • Temperature • Process Atmosphere Sensors • Carbon probes, dew point, carbon monoxide, carbon dioxide, methane, etc. • Calibrate Sensors Frequently US DOE – Industries of the Future Workshop Series

  24. Best Bets for System Savings and Improvements US DOE – Industries of the Future Workshop Series

  25. Best Bets for System Savings and Improvements US DOE – Industries of the Future Workshop Series

  26. Application of New Technologies/Concepts • Infrared heating systems • Improved product quality • Faster line speeds • Lower energy and capital costs • Reduced floor space requirements • Lower maintenance costs • Ultra-low NOx burners • Pulse combustion burners US DOE – Industries of the Future Workshop Series

  27. Software Tools • Process Heating Assessment and Survey Tool (PHAST) • Provides an introduction to process heating methods and tools to improve thermal efficiency of heating equipment. • Used to survey process heating equipment that uses fuel, steam, or electricity • Identifies the most energy-intensive equipment. • Performs an energy (heat) balance on selected equipment (furnaces) to identify and reduce non-productive energy use. • Compares performance of the furnace under various operating conditions and test "what-if" scenarios. US Department of Energy – Office of Industrial Technologies http://www.oit.doe.gov/bestpractices/software_tools.shtml#phast US DOE – Industries of the Future Workshop Series

  28. PHAST Calculators • Energy Equivalency: Calculates heat requirements when the heat source is changed from fuel firing (Btu/hr) to electricity (kWh) or from electricity to fossil fuel firing. • Efficiency Improvement: Calculates available heat for fuel-fired furnaces and expected energy savings when burner operating conditions are enhanced. • Oxygen Enrichment: Calculates available heat for fuel-fired furnaces and expected energy savings when oxygen in combustion “air” is increased from the standard (21%) value. US DOE – Industries of the Future Workshop Series

  29. PHAST Screen Shots US DOE – Industries of the Future Workshop Series

  30. Sample Input Data Screen for Specific Equipment • Accounts for • Wall heat losses • Heat storage • Openings • Combustion conditions • Losses due to exposed parts • Water cooling US DOE – Industries of the Future Workshop Series

  31. PHAST Reports • Report presents • Summary of avoided energy costs • Energy ($/kWh) • Natural Gas ($/MMBtu) • Steam ($/MMBtu) • Process heating equipment • Cost distribution • Energy usage • Operational cost US DOE – Industries of the Future Workshop Series

  32. Technology - Conclusion

  33. In house assessment • Tools available from US DOE Process Heating Systems • US DOE Industrial Assessment Centers • Energy Resources Center @ UIC • Private energy service companies Assessing your current system • Industrial Heating Equipment Association US DOE – Industries of the Future Workshop Series

  34. Assessment Resources • Energy Resources Center @ UIC www.erc.uic.edu - can provide expertise in industrial steam systems, also will perform energy assessments for industrial clients. • Industrial Assessment Centers http://www.oit.doe.gov/iac/ - will provide energy assessments (including steam systems) free of charge to qualified industrial clients. • US DOE Process Heating Program http://www.oit.doe.gov/bestpractices/process_heat/- provides a wide range of technical assistance materials, tools, and services to the industrial market. • National Association of Energy Service Companies http://www.naesco.org/ - trade organization of companies that will perform energy audits and finance improvements. BACK US DOE – Industries of the Future Workshop Series