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IntroductionType of waste heat recoveryAssessment of waste heat recovery                                    2
What is Waste Heat?• “Dumped” heat that can still be  reused• “Value” (quality) more important than  quantity• Waste heat ...
IntroductionSource and QualityTable: Waste heat source and quality  S. No      Sourc of Waste Heat                     Qua...
IntroductionHigh Temperature Heat RecoveryTable: Typical waste heat temperature at high temperaturerange from various sour...
IntroductionMedium Temperature HeatRecoveryTable: Typical waste heat temperature at medium temperature rangefrom various s...
IntroductionLow Temperature Heat Recovery                                                                 low temperature ...
Training Agenda: Waste                      IntroductionWaste heat recoveryThermal Equipment/                      Type of...
Type of Waste Heat RecoveryCommercial Waste Heat Recovery Recuperators                          Inlet air from           ...
Type of Waste Heat RecoveryCommercial WasteHeat Recovery Metallic radiation  recuperators                              Re...
Type of Waste Heat RecoveryCommercial Waste Heat Recovery Convective  recuperators•   Hot gas through    parallel small d...
Type of Waste Heat Recovery Commercial Waste Heat Recovery Radiation/convective  hybrid recuperators •   Combinations of ...
Type of Waste Heat RecoveryCommercial Waste Heat Recovery Ceramic recuperators  • Less temperature limitations:     • Ope...
Type of Waste Heat RecoveryRegenerator•   Large capacities•   Glass and steel melting    furnaces•   Time between the    r...
Type of Waste Heat Recovery    Heat Wheels•   Porous disk rotating    between two side-by-    side ducts•   Low to medium ...
Type of Waste Heat RecoveryHeat Pipe•   Transfer up to 100    times more thermal    energy than copper•   Three elements: ...
Type of Waste Heat RecoveryHeat Pipe Performance and advantage  • Lightweight and compact  • No need for mechanical maint...
Type of Waste Heat RecoveryHeat Pipe Typical application   • Process to space heating     - Transfers thermal energy from...
Type of Waste Heat RecoveryEconomizer•   Utilize the flue gas heat for pre-heating the boiler    feed water•   1% fuel sav...
Type of Waste Heat RecoveryEconomizer Shell and tube heat exchanger  • Used when the medium containing waste heat is a   ...
Type of Waste Heat Recovery    Plate Heat Exchanger    •    Parallel plates forming a thin flow pass    •    Avoids high c...
Type of Waste Heat Recovery    Plate Heat Exchanger     Run around coil exchanger•    Heat transfer     from hot to     c...
Type of Waste Heat Recovery    Plate Heat Exchanger Waste heat boiler•    Water tube boiler: hot     exhaust gases pass  ...
Type of Waste Heat RecoveryHeat Pump                          The vapour                                   compression cyc...
Type of Waste Heat RecoveryHeat Pump Developed as a space heating system Can upgrade heat >2X the energy  consumed by th...
Type of Waste Heat RecoveryHeat Pump Thermo compressor  • Compress low-pressure steam by very high-  pressure steam and r...
Training Agenda: WasteIntroductionType of waste heat recoveryAssessment of waste heat recovery                            ...
Assessment of waste heatrecoveryHeat LossesQuality:•    Higher temperatures = Higher quality = Lower heat     recovery cos...
Assessment of waste heatrecoveryHeat Saving Calculation ExampleSaving money by recovering heat from hot wastewater:• Disch...
Assessment of waste heatrecoveryHeat Saving Calculation Examplem = 1000 kg/hr = 10000 x 5000 kg/yr = 50000000 kg/yearCp = ...
Training Session on EnergyEquipmentWaste Heat Recovery                                   THANK YOU       FOR YOUR ATTENTI...
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Waste Heat Recovery Vinay Shukla

Perspective point constraining the heat recovery in industries; power.

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Waste Heat Recovery Vinay Shukla

  1. 1. 1
  2. 2. IntroductionType of waste heat recoveryAssessment of waste heat recovery 2
  3. 3. What is Waste Heat?• “Dumped” heat that can still be reused• “Value” (quality) more important than quantity• Waste heat recovery saves fuel 3
  4. 4. IntroductionSource and QualityTable: Waste heat source and quality S. No Sourc of Waste Heat Quality of Waste Heat 1 Heat in flue gases The higher the temperature, the greater the potential value for heat recovery 2 Heat in vapour streams As above but when condensed, latent heat also recoverable 3 Convective & radiant heat lost Low grade – if collected may be used for from exterior of equipment space heating or air preheats 4 Heat losses in cooling water Low grade – useful gains if heat is exchanged with incoming fresh water 5 Heat losses in providing •High grade if it can be utilized to reduce chilled water or in the demand for refrigeration disposal of chilled water •Low grade if refrigeration unit used as a form of Heat pump 6 Heat stored in products Quality depends upon temperature leaving the process 7 Heat in gaseous & liquid Poor if heavily contaminated & thus requiring effluents leaving process alloy heat exchanger 4
  5. 5. IntroductionHigh Temperature Heat RecoveryTable: Typical waste heat temperature at high temperaturerange from various sources Types of Devices Temperature (0C) Nickel refining furnace 1370 – 1650 Aluminium refining furnace 650 –760 Zinc refining furnace 760 – 1100 Copper refining furnace 760 – 815 Steel heating furnace 925 – 1050 Copper reverberatory furnace 900 – 1100 Open hearth furnace 650 – 700 Cement kiln (Dry process) 620 – 730 Glass melting furnace 1000 – 1550 Hydrogen plants 650 – 1000 Solid waste incinerators 650 – 1000 Fume incinerators 650 – 1450 5
  6. 6. IntroductionMedium Temperature HeatRecoveryTable: Typical waste heat temperature at medium temperature rangefrom various sources Types of Devices Temperature (0C) Steam boiler exhaust 230 – 480 Gas turbine exhaust 370 – 540 Reciprocating engine exhaust 315 – 600 Reciprocating engine exhaust (turbo 230 – 370 charged) Heat treatment furnace 425 – 650 Drying & baking ovens 230 – 600 Catalytic crackers 425 – 650 Annealing furnace cooling systems 425 – 650 6
  7. 7. IntroductionLow Temperature Heat Recovery low temperature range from various sources Source Temperature 0C Table: Typical waste heat temperature atProcess steam condensate 55-88Cooling water from: Furnace doors 32-55Bearings 32-88Welding machines 32-88Injection molding machines 32-88Annealing furnaces 66-230Forming dies 27-88Air compressors 27-50Pumps 27-88Internal combustion engines 66-120Air conditioning and refrigeration condensers 32–43Liquid still condensers 32-88Drying, baking and curing ovens 93-230Hot processed liquids 32-232Hot processed solids 93-232 7
  8. 8. Training Agenda: Waste IntroductionWaste heat recoveryThermal Equipment/ Type of waste heat recovery Performance evaluation 8
  9. 9. Type of Waste Heat RecoveryCommercial Waste Heat Recovery Recuperators Inlet air from atmosphere • Heat exchange between flue gases and the air through metallic/ ceramic walls Exhaust gas from process • Ducts/tubes carry Centre tube plate Outside combustion air for ducting Preheated air preheating Tune plate • Waste heat stream on Figure 1 : Waste heat recovery other side using recuperator, Source: SEAV 9
  10. 10. Type of Waste Heat RecoveryCommercial WasteHeat Recovery Metallic radiation recuperators Recuperator (Hardtech Group) Figure 2. Metallic Radiation• Simplest recuperator• Two metal tubes• Less fuel is burned per furnace load• Heat transfer mosly by radiation 10
  11. 11. Type of Waste Heat RecoveryCommercial Waste Heat Recovery Convective recuperators• Hot gas through parallel small diameter tubes• Tubes can be baffled to allow gas to pass over them again• Baffling increases heat exchange but more Figure 3. Convective expensive exchanger Recuperator is needed ( 11
  12. 12. Type of Waste Heat Recovery Commercial Waste Heat Recovery Radiation/convective hybrid recuperators • Combinations of radiation & convection • More effective heat transfer • More expensive but less bulky than simple metallic radiation recuperators Figure 4. Hybrid Recuperator 12
  13. 13. Type of Waste Heat RecoveryCommercial Waste Heat Recovery Ceramic recuperators • Less temperature limitations: • Operation on gas side up to 1550 ◦C • Operation on preheated air side to 815 ◦C • New designs • Last two years • Air preheat temperatures <700◦ C • Lower leakage rates 13
  14. 14. Type of Waste Heat RecoveryRegenerator• Large capacities• Glass and steel melting furnaces• Time between the reversals important to reduce costs• Heat transfer in old regenerators reduced by •Dust & slagging on surfaces Figure 5. Regenerator •heat losses from the (Department of Coal, India, 1985) walls 14
  15. 15. Type of Waste Heat Recovery Heat Wheels• Porous disk rotating between two side-by- side ducts• Low to medium temperature waste heat recovery systems• Heat transfer efficiency up to 85 % Figure 6. Heat Wheel (SADC, 1999) 15
  16. 16. Type of Waste Heat RecoveryHeat Pipe• Transfer up to 100 times more thermal energy than copper• Three elements: - sealed container - capillary wick structure - working fluid• Works with evaporation and condensation Figure 7. Heat Pipe ( 16
  17. 17. Type of Waste Heat RecoveryHeat Pipe Performance and advantage • Lightweight and compact • No need for mechanical maintenance, input power, cooling water and lubrication systems • Lowers the fan horsepower requirement and increases the overall thermal efficiency of the system • Can operate at 315 ◦C with 60% to 80% heat recovery 17
  18. 18. Type of Waste Heat RecoveryHeat Pipe Typical application • Process to space heating - Transfers thermal energy from process exhaust for building heating • Process to process - Transfers recovered waste thermal energy from the process to the incoming process air • HVAC applications - Cooling and heating by recovering thermal energy 18
  19. 19. Type of Waste Heat RecoveryEconomizer• Utilize the flue gas heat for pre-heating the boiler feed water• 1% fuel savings if • 60 ◦C rise of feed water • 200 ◦C rise in combustion air temp Figure 8. Economizer (Bureau of Energy Efficiency, 2004) 19
  20. 20. Type of Waste Heat RecoveryEconomizer Shell and tube heat exchanger • Used when the medium containing waste heat is a liquid or a vapor that heats another liquid• Shell containsthe tube bundle,and usuallyinternal bafflesto direct thefluid• Vapor Figure 9. Shell & Tube Heat Exchangercontained within (King Fahad University of Petroleum & Minerals,the shell 2003) 20
  21. 21. Type of Waste Heat Recovery Plate Heat Exchanger • Parallel plates forming a thin flow pass • Avoids high cost of heat exchange surfaces• Corrugated plates to improve heat transfer• When directions of hot and cold fluids are opposite, the arrangement is counter current Figure 10. Plate Heat Exchanger (Canada Agriculture and Agri-Food) 21
  22. 22. Type of Waste Heat Recovery Plate Heat Exchanger  Run around coil exchanger• Heat transfer from hot to colder fluid via heat transfer fluid• One coil in hot stream• One coil in cold stream Figure 11. Run Around Coil Exchanger (SADC , 1999) 22
  23. 23. Type of Waste Heat Recovery Plate Heat Exchanger Waste heat boiler• Water tube boiler: hot exhaust gases pass over parallel tubes with water• Capacities: 25 m3 to 30,000 m3 /min of exhaust gas Figure 12. Two-Pass Water Tube Waste Heat Recovery Boiler (Canada Agriculture and Agri-Food) 23
  24. 24. Type of Waste Heat RecoveryHeat Pump The vapour compression cycleFigure 13. Heat Pump Arrangement 24(SADC, 1999)
  25. 25. Type of Waste Heat RecoveryHeat Pump Developed as a space heating system Can upgrade heat >2X the energy consumed by the device Most promising when heating and cooling capabilities are combined 25
  26. 26. Type of Waste Heat RecoveryHeat Pump Thermo compressor • Compress low-pressure steam by very high- pressure steam and reuse as medium pressure steam • Nozzle for acceleration of HP steam to a high velocity fluid. 26 Figure: Thermo compressor
  27. 27. Training Agenda: WasteIntroductionType of waste heat recoveryAssessment of waste heat recovery 27
  28. 28. Assessment of waste heatrecoveryHeat LossesQuality:• Higher temperatures = Higher quality = Lower heat recovery costsQuantity:• The amount of recoverable heat can be calculated as: Q = heat content in kCal V = the flow rate of the substance in m3/hr ρ = density of the flue gas in kg/m3 Q = V x ρ x Cp x ∆T Cp = the specific heat of the substance in kCal/kg oC ∆T = the temperature difference in oC Cp (Specific heat of flue gas) = 0.24 kCal/kg/ oC 28
  29. 29. Assessment of waste heatrecoveryHeat Saving Calculation ExampleSaving money by recovering heat from hot wastewater:• Discharge of the waste water is 10000 kg/hr at 75◦C• Preheat 10000 kg/hr of cold inlet water of 20◦C• A heat recovery factor of 58%• An operation of 5000 hours per yearThe annual heat saving (Q) is: Q = m x Cp x ∆T x η 29
  30. 30. Assessment of waste heatrecoveryHeat Saving Calculation Examplem = 1000 kg/hr = 10000 x 5000 kg/yr = 50000000 kg/yearCp = 1 kCal/kg ◦C∆T = (75 – 20) ◦C = 55 ◦Cη = Heat Recovery Factor = 58% or 0.58 ⇒Q = 50000000 x 1 x 55 x 0.58 = 1595000000 kCal/yearGCV of Oil = 10,200 kCal/kgEquivalent Oil Savings = 159500000 / 10200 = 156372 LCost of Oil = 0.35 USD/LMonetary Savings = 54730 USD/Annum 30
  31. 31. Training Session on EnergyEquipmentWaste Heat Recovery  THANK YOU FOR YOUR ATTENTION 31

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