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WASTE HEAT RECOVERY SYSTEM

WASTE HEAT RECOVERY SYSTEM

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WASTE HEAT RECOVERY SYSTEM

  1. 1. WASTE HEAT RECOVERY SYSTEM
  2. 2. INTRODUCTION  The primary source of waste heat of a main engine is the exhaust gas heat dissipation , which accounts for about half of the total waste heat, i.e. about 25% of the total fuel energy.  the exhaust gas temperature is relatively low after the turbocharger, and just high enough for producing the necessary steam for the heating purposes of the ship by means of a standard exhaust gas fired boiler of the smoke tube design..  ME main engine tuned for WHRS will increase the possibilities of producing electricity from the exhaust gas.
  3. 3.  Depending on the level of complexity acceptable to the owner and shipyard and the actual electrical power consumption on-board, it is possible to choose between the following systems: 1. ST-PT – Steam Turbine-Power Turbine generator unit (Power turbine, steam turbine, gear and generator unit with single or dual pressure steam turbine) 2. STG – Steam Turbine Generator unit (Steam turbine, gear and generator unit, single or Dual steam pressure) 3. PTG – Power Turbine Generator unit (Power turbine, gear and generator unit).
  4. 4. POWER CONCEPT AND ARRANGMENT  The principle of the WHRS-tuned MAN B&W low speed diesel engine is that part of the exhaust gas flow is bypassed the main engine turbocharger(s) through an exhaust gas bypass.  the total amount of intake air and exhaust gas is reduced.  The reduction of the intake air amount and the exhaust gas amount results in an increased exhaust gas temperature after the main engine turbocharger(s) and exhaust gas bypass.  an increase in the maximum obtainable steam production power for the exhaust gas fired boiler – steam, which can be used in a steam turbine for electricity production.  the revised pressure drop in the exhaust gas bypass, which is part of the WHRS, can be utilised to produce electricity by applying a power turbine.
  5. 5. WHR SYSTEM CONFIGURATION:
  6. 6. Choosing a system for a project depends:  on the power demand onboard the ship (electrical load at sea),  the ship’s running profile (hours at different main engine loads at sea),  the acceptable payback time for the proposed WHRS solution based on the running profile and the space available on the ship Important part of selecting the best WHRS for a ship project is  choosing the best suited propulsion power and rpm for the ship – biggest possible propeller – so as to ensure the lowest possible fuel consumption for the basic performance of the ship.
  7. 7.  Whrs will be able to supply the total electricity need of the ship as a standalone power source,  but it can also run in parallel with a shaft generator, shaft motor and auxiliary diesel generating sets.  this type of advanced power system requires an advanced power management system (pms), with which the man diesel & turbo engine control system is designed to communicate.
  8. 8. Power Turbine and Generator (PTG)  The simplest and cheapest system consists of an exhaust gas turbine (also called a power turbine) installed in the exhaust gas bypass, and a generator that converts power from the power turbine to electricity on-board the ship  For power turbine solutions, the main engine receiver will be equipped with two exhaust gas connections, one for engine exhaust gas by-pass (EGB) and one for the power turbine  The power turbine and the generator are placed on a common bedplate  The power turbine is driven by part of the exhaust gas flow which bypasses the turbochargers. The power turbine produces extra output power for electric power production, which depends on the bypassed exhaust gas flow amount.
  9. 9. (Specified maximum continuous rating)
  10. 10. Steam Turbine and Generator (STG)  When applying the steam turbine (ST) as a stand-alone solution, the exhaust gas bypass stream is mixed with the exhaust outlet from the turbocharger(s), increasing the exhaust gas temperature before the boiler inlet.  When part of the exhaust gas flow is bypassed the turbocharger, the total amount of air and gas will be reduced, and the exhaust gas temperature after the turbocharger and bypass will increase. This will increase the obtainable steam production power for the exhaust gas fired boiler.  By installing a steam turbine (often called a turbo generator), the obtainable steam production from the exhaust boiler system can be used for electric power production
  11. 11. Steam Turbine, Power Turbine, and Generator (ST-PT)  If the electric power demand on the ship is very high, e.G. A container ship, the power turbine and the steam turbine can be built together to form a combined system. The power turbine and the steam turbine is built onto a common bedplate and, via reduction gearboxes, connected to a common generator  In many conditions, reduces the fuel costs of the ship considerably by being able to cover the total electric power needs in many conditions onboard the ship  Otherwise, a shaft motor / generator connected to the main engine shaft could be an option  Combining both steam and power turbines – some 8-11% power can be recovered, depending on the main engine size, engine rating and ambient conditions
  12. 12. Main Engine and WHRS System Control The main engine control and the WHRS control must be able to function as an integrated part of the total control system of the ship, which means that integration between the systems must be in place.
  13. 13.  The development of the WHRS and main engine controls is based on the ship owner’s demand for full control and optimum fuel consumption in all operational modes. Focus is very much on fuel economy because of the continuously increasing fuel oil prices.  The engine control and the whrs control have to be strongly integrated because the whrs steam turbine and power turbine use the energy in the exhaust gas to recover energy.  The connection between the main engine and whrs can be seen in figure showing the exhaust gas flow between engine, power turbine and exhaust boiler. Two exhaust connection on engine exhaust receiver is necessary for WHRS arrangements including power turbine.
  14. 14. The basis for this layout of the connections between the engine and WHRS components is two-sided as the control must first be able to protect the engine against unacceptable conditions, and second ensure maximum available power for the WHRS. This is done by controlling the exhaust gas bypass amount, keeping it within acceptable limits.
  15. 15. Installation Aspects  Size of the system and the complexity of the piping and cabling, and other preparations to be considered by the shipyard.  All whrs generator systems are prepared on a common bedplate, where the different components already are installed and assembled  The main concerns of the shipyard are therefore to find space in the machinery room on-board – near the main engine installation – for foundation, piping and cabling between these main components
  16. 16. Power Turbine WHRS Solution  The simplest installation  The system is the smallest of the different systems  The main connection between the WHRS PTG and the MAN B&W engine is only the exhaust gas by-pass line
  17. 17. Steam Turbine WHRS Solution  Installation is quite extensive as many different components must be connected.  The boiler installation has to be in-creased in size. From the boiler, one or two pipes should be connected to the steam turbine, depending on whether the single or dual pressure system is applied.  The condenser must be installed under the bedplate of the steam turbine  The condenser piping is connected to the boiler system so that the water can be recirculated.  The condenser is furthermore equipped with cooling water piping.
  18. 18. Full Steam and Power Turbine WHRS Solution  The power turbine will need an inlet and exhaust gas pipe connected to the existing exhaust gas system.  The steam turbine requires the piping system.  Power turbine takes the exhaust gas from the exhaust gas receiver, which sits on the engine, and the steam turbine receives steam from the boiler system.  With whrs including steam turbine, more space is required in the engine room and casing areas.  The ship designers must make reserve space for all components in the machinery arrangements and casings.
  19. 19. Exhaust Gas Bypass with Power Turbine
  20. 20. Exhaust gas bypass without power turbine
  21. 21. Single Pressure Steam System  The simple single-pressure steam system only utilises the exhaust gas heat  The steam drum from the oil fired boiler can also be used instead of a separate steam drum  Is less complex and easy to operate, but the possible efficiency of the total steam circuit (exhaust boiler and steam turbine) will be less than the more used dual pressure steam system.
  22. 22. Dual Pressure Steam System  it is not possible to install an exhaust gas low-pressure preheater section in the exhaust gas boiler  the exhaust gas boiler outlet temperature would otherwise be too low and increase the risk of wet (oily) soot deposits on the boiler tubes  Too low an exhaust boiler outlet temperature may result in corrosion in the exhaust piping when running on normal HFO with sulphur content  needs supplementary waste heat recovery (WHR) sources (jacket water and scavenge air heat) for preheating feed water, which will increase the obtainable steam and electric power production of the WHR
  23. 23. Obtainable Electric Power of the WHRS Waste Heat Recovery Systems Max. electrical recovery % TCS – PTG: 3 to 5 STG – Single pressure system: 4 to 7 STG – Dual pressure system: 5 to 8 Full WHRS (ST - PT): 5 to 11
  24. 24. CONCLUSION  Significant fuel cost savings can be achieved by adding a WHRS to a ship project.  A full whrs (st & pt), a standalone whrs (st) or a standalone ptg solution are selected, all of these solutions offer large fuel savings.  Fuel reductions of between 4-11% are possible, depending on the selected whrs solution, main engine power level, electric need at sea, operational profile, etc.  The larger the engine power, the greater the possible fuel saving.  In addition to large fuel savings, a whrs gives large co2, nox, sox and particulate reductions to the benefit of the environmnet.
  25. 25. THANKYOU

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