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Process Heating

Process Heating. Technology - Concept. Types of Energy Used for Industrial Heating. Process Heating Demand by Industry. Industrial Process Heating Methods. Fuel Fired Heating Direct Fired Indirect Fired Radiant Tubes Muffle Steam Heating Indirect (heat exchanger, jacketed tank)

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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

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