Submitted by,
Aniket Nemade

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Less Emission through Waste Heat Recovery
Introduction – Why waste heat recovery?
Reducing emissions and reducing engine operating costs
To increase exhaust gas energy and employing both steam and exhaust gas turbines in a Total Heat Recover Plant
low-speed marine engines are very highly developed and there is little potential for achieving significant reductions in CO2 emissions
Controlling the generation of the emissions inside engine cylinders,
Removing the emissions by after treatment of the exhaust gases, or in the case of SOX emissions restricting the fuel specification.
low-speed engines having an excellent efficiency of up to 50%
Case study
a Sulzer 12RTA96C engine developing a maximum continuous output of 68,640 kW
Daily consumption of heavy fuel oil about 300 tonnes
To generate 68,640 kW shaft power
Total Heat Recovery Plant
Exhaust gas economizer
Feed water heating
Turbo generator
Power Turbine
Waste gate
Shaft motor/alternator system
Exhaust gas economizer
High-pressure part with HP evaporator and superheating section and a low-pressure part with LP evaporator and superheating section
Economizer outlet temperature is not less then 160°C to avoid sulphur corrosion
Feed water heating
The feed water is heated from the engine’s jacket cooling water to a temperature of 85°C
Feed water for the high-pressure section is further heated in the engines scavenge air cooler to about 150°C to 170°C
Turbo generator
The high-pressure side works at about 8.5–9.5 bar (g) inlet pressure
This requires three stages at a condenser pressure of 0.065 bar
Economizer outlet temperature of 160°C, a low-pressure steam pressure at the turbine inlet of 3.0–3.5 bar (g) pressure
Power Turbine:-
uses a part of the exhaust gas stream (about 10%) from the diesel engine
The torque of the power turbine is fed to the steam turbine rotor through a reduction gear and an overrunning clutch
The power turbine operates between 55% and 100% engine load
less than 55% load is not sufficiently high and therefore does not allow exhaust gas to be branched off to drive a power turbine
Waste gate
to operate within the intake temperature range of –5°C to 35°C
protected from excessive maximum cylinder pressure occurring owing to the high specific density of the cold air.
the best choice is a scavenge air waste gate because it offers a much higher reliability by avoiding contact with high-temperature exhaust gas
Operating modes for the Total Heat Recovery Plant
Motor mode
Alternator mode
Booster mode
Emergency propulsion mode
Potential of the Total Heat Recovery Plant
Recovery Plant is defined as follows:
A1 = ISO conditions, new engine [Reference conditions]
A2 = ISO conditions, maximum exhaust gas back pressure and air suction pressure loss
A3 = ISO conditions, average aged engine
A4 = ISO conditions, maximum aged engine
B1 = Tropical conditions, new engine
B2 = Tropical conditions, maximum exhaust gas back pressure and air suction pressure loss
B3 = Tropical conditions, average aged engine
B4 = Tropical conditions, maximum aged engine
When progressing from operating condition A1 to B4, the following changes can be expected (Fig. 10):
fuel consumption = + 2.3%
• Steam turbine output = + 25.8%
• Power turbine output = –10.0%
Steam turbine & power turbine at various operating condition
Comparison of heat balances for Sulzer 12RT-fl ex96C engines without heat recovery (left) and with the Total HeatRecovery Plant (right) showing the 12% gain in overall effi ciency for the Total Heat Recovery Plant.
Conclusion
saving fuel costs and reducing CO2 emissions
modern large, low-speed engines are very highly developed and there is little potential for achieving significant savings in fuel consumption, and thereby reducing CO2 emissions by engine developments alone.
benefits from an improved competitively in the freight market.
environmentally-friendly solutions.