Waste heat recovery

Slide1 : Training Session on Energy Equipment Waste Heat Recovery Presentation from the “Energy Efficiency Guide for Industry in Asia” www.energyefficiencyasia.org Thermal Equipment/ Waste heat recovery © UNEP 2006


Slide2 : Training Agenda: Waste Introduction Type of waste heat recovery Assessment of waste heat recovery Thermal Equipment/ Waste heat recovery © UNEP 2006


Slide3 : © UNEP 2006 Introduction “Dumped” heat that can still be reused “Value” (quality) more important than quantity Waste heat recovery saves fuel What is Waste Heat? Thermal Equipment/ Waste heat recovery


Slide4 : © UNEP 2006 Introduction Source and Quality Thermal Equipment/ Waste heat recovery Table: Waste heat source and quality


Slide5 : © UNEP 2006 Introduction High Temperature Heat Recovery Thermal Equipment/ Waste heat recovery Table: Typical waste heat temperature at high temperature range from various sources


Slide6 : © UNEP 2006 Introduction Medium Temperature Heat Recovery Thermal Equipment/ Waste heat recovery Table: Typical waste heat temperature at medium temperature range from various sources


Slide7 : © UNEP 2006 Introduction Low Temperature Heat Recovery Thermal Equipment/ Waste heat recovery Table: Typical waste heat temperature at low temperature range from various sources


Slide8 : © UNEP 2006 Training Agenda: Waste Introduction Type of waste heat recovery Performance evaluation Thermal Equipment/ Waste heat recovery


Slide9 : © UNEP 2006 Type of Waste Heat Recovery Commercial Waste Heat Recovery Thermal Equipment/ Waste heat recovery Recuperators Heat exchange between flue gases and the air through metallic/ceramic walls Ducts/tubes carry combustion air for preheating Waste heat stream on other side Figure 1 : Waste heat recovery using recuperator, Source: SEAV


Slide10 : © UNEP 2006 Type of Waste Heat Recovery Commercial Waste Heat Recovery Thermal Equipment/ Waste heat recovery Metallic radiation recuperators Figure 2. Metallic Radiation Recuperator (Hardtech Group) Simplest recuperator Two metal tubes Less fuel is burned per furnace load Heat transfer mosly by radiation


Slide11 : © UNEP 2006 Type of Waste Heat Recovery Commercial Waste Heat Recovery Thermal Equipment/ Waste heat recovery Convective recuperators Figure 3. Convective Recuperator (Reay, D.A., 1996) 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 expensive exchanger is needed


Slide12 : © UNEP 2006 Type of Waste Heat Recovery Commercial Waste Heat Recovery Thermal Equipment/ Waste heat recovery Radiation/convective hybrid recuperators Figure 4. Hybrid Recuperator (Reay, D.A., 1996) Combinations of radiation & convection More effective heat transfer More expensive but less bulky than simple metallic radiation recuperators


Slide13 : © UNEP 2006 Type of Waste Heat Recovery Commercial Waste Heat Recovery Thermal Equipment/ 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


Slide14 : © UNEP 2006 Type of Waste Heat Recovery Regenerator Thermal Equipment/ Waste heat recovery Figure 5. Regenerator (Department of Coal, India, 1985) 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 heat losses from the walls


Slide15 : © UNEP 2006 Type of Waste Heat Recovery Heat Wheels Thermal Equipment/ Waste heat recovery Figure 6. Heat Wheel (SADC, 1999) Porous disk rotating between two side-by-side ducts Low to medium temperature waste heat recovery systems Heat transfer efficiency up to 85 %


Slide16 : © UNEP 2006 Type of Waste Heat Recovery Heat Pipe Thermal Equipment/ Waste heat recovery Figure 7. Heat Pipe (SADC, 1999) Transfer up to 100 times more thermal energy than copper Three elements: - sealed container - capillary wick structure - working fluid Works with evaporation and condensation


Slide17 : © UNEP 2006 Type of Waste Heat Recovery Heat Pipe Thermal Equipment/ Waste heat recovery 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


Slide18 : © UNEP 2006 Type of Waste Heat Recovery Heat Pipe Thermal Equipment/ Waste heat recovery 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


Slide19 : © UNEP 2006 Type of Waste Heat Recovery Economizer Thermal Equipment/ Waste heat recovery Figure 8. Economizer (Bureau of Energy Efficiency, 2004) 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


Slide20 : © UNEP 2006 Type of Waste Heat Recovery Economizer Thermal Equipment/ Waste heat recovery Shell and tube heat exchanger Used when the medium containing waste heat is a liquid or a vapor that heats another liquid Figure 9. Shell & Tube Heat Exchanger (King Fahad University of Petroleum & Minerals, 2003) Shell contains the tube bundle, and usually internal baffles to direct the fluid Vapor contained within the shell


Slide21 : © UNEP 2006 Type of Waste Heat Recovery Plate Heat Exchanger Thermal Equipment/ Waste heat recovery Figure 10. Plate Heat Exchanger (Canada Agriculture and Agri-Food) 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


Slide22 : © UNEP 2006 Type of Waste Heat Recovery Plate Heat Exchanger Thermal Equipment/ Waste heat recovery Run around coil exchanger Figure 11. Run Around Coil Exchanger (SADC , 1999) Heat transfer from hot to colder fluid via heat transfer fluid One coil in hot stream One coil in cold stream


Slide23 : © UNEP 2006 Type of Waste Heat Recovery Plate Heat Exchanger Thermal Equipment/ Waste heat recovery Waste heat boiler Figure 12. Two-Pass Water Tube Waste Heat Recovery Boiler (Canada Agriculture and Agri-Food) Water tube boiler: hot exhaust gases pass over parallel tubes with water Capacities: 25 m3 to 30,000 m3 /min of exhaust gas


Slide24 : © UNEP 2006 Type of Waste Heat Recovery Heat Pump Thermal Equipment/ Waste heat recovery Figure 13. Heat Pump Arrangement (SADC, 1999)


Slide25 : © UNEP 2006 Type of Waste Heat Recovery Heat Pump Thermal Equipment/ Waste heat recovery 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


Slide26 : © UNEP 2006 Type of Waste Heat Recovery Heat Pump Thermal Equipment/ Waste heat recovery 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. Figure: Thermo compressor


Slide27 : © UNEP 2006 Training Agenda: Waste Introduction Type of waste heat recovery Assessment of waste heat recovery Thermal Equipment/ Waste heat recovery


Slide28 : Assessment of waste heat recovery Quality: Higher temperatures = Higher quality = Lower heat recovery costs Quantity: The amount of recoverable heat can be calculated as: Heat Losses Thermal Equipment/ Waste heat recovery © UNEP 2006


Slide29 : © UNEP 2006 Heat Saving Calculation Example Thermal Equipment/ Waste heat recovery Saving money by recovering heat from hot waste water: 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 year The annual heat saving (Q) is: Assessment of waste heat recovery


Slide30 : © UNEP 2006 Heat Saving Calculation Example Thermal Equipment/ Waste heat recovery m = 1000 kg/hr = 10000 x 5000 kg/yr = 50000000 kg/year Cp = 1 kCal/kg ◦C T = (75 – 20) ◦C = 55 ◦C  = Heat Recovery Factor = 58% or 0.58 GCV of Oil = 10,200 kCal/kg Equivalent Oil Savings = 159500000 / 10200 = 156372 L Cost of Oil = 0.35 USD/L Monetary Savings = 54730 USD/Annum Assessment of waste heat recovery


Slide31 : Training Session on Energy Equipment Waste Heat Recovery THANK YOU FOR YOUR ATTENTION © UNEP Thermal Equipment/ Waste heat recovery


Slide32 : Thermal Equipment/ Waste heat recovery © UNEP 2006 Disclaimer and References This PowerPoint training session was prepared as part of the project “Greenhouse Gas Emission Reduction from Industry in Asia and the Pacific” (GERIAP). While reasonable efforts have been made to ensure that the contents of this publication are factually correct and properly referenced, UNEP does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. © UNEP, 2006. The GERIAP project was funded by the Swedish International Development Cooperation Agency (Sida) Full references are included in the textbook chapter that is available on www.energyefficiencyasia.org