Cogeneration project opportunity

Cogeneration project
opportunity
KMITL COMBUSTION LAB

Introduction to cogeneration
• conventional steam production in industrial
• What if we place Micro-turbine before the boiler ?
Air inlet
NGV inlet

Introduction to cogeneration
• What if we place Micro turbine and afterburner before the boiler ?
• High value by product electrical generation
• Generating by product electrical power with the same cost of fuel heating value
• To generate by product electrical power while sustaining boiler capacity and
efficiency
Micro turbine
exhaust manifold
After burner
Exhaust stack
Air inletNGV inlet
Steam generation
Electrical
generation

Cogeneration introduction ( Micro turbine application )
Duct combustor
Micro turbine & generator unit
Exhaust manifold duct
To boiler burner
Boiler unit

Cogeneration introduction ( piston engine application )
• Considerable higher thermal efficiency ( around 40-45% )
• More complicate thermal recovery
• Exhaust direct combustion to boost temperature may not capable

Example of cogeneration application
• Electrical & hot water generation ( commercial set )
• Electrical & steam generation with direct burner
• Electrical & cold water generation (trigeneration)
• Integration with ORC or Rankine bottom cycle ( >40% electrical efficiency )
Capstone with ORC integration

C65 electrical & hot water
generation commercial unit

Capstone C65 energy analysis
• Electrical & hot water generation, commercial package
246.67 KW
NGV burn C65
turbine
65 KW electrical generation
120 KW hot water generation
61.67 KW stack loss

Capstone C65 business analysis
• Electrical & hot water generation, commercial package
398.31baht/hr
NGV burn C65
turbine
240.5 baht/hr electrical generation
193.77 baht/hr hot water generation
0 baht /hr
• profit = (240.5 + 193.77) – 398.31
= 35.96 baht / hr
= 315,009.6 baht / yr / unit
Note : NGV cost 17 baht/Kg , Electrical cost 3.7 baht / Kwh
NGV heating value @ 37.9 MJ/Kg

C65 Electrical & steam
generation with afterburner

Energy analysis (compare with conventional boiler system )
• Energy flow with conventional boiler
80 % boiler efficiency 85.4 KW stack loss
427 KW (fuel burn)
341.6 KW of steam generation

Business analysis (compare with conventional boiler system )
341.6 KW of steam generation
• Money flow with conventional boiler
750 baht/hr (NGV burn)
80 % boiler efficiency 20 % stack loss
• pay 750 baht / hr for NGV fueled to generate steam 341.6 KW
Note : NGV cost 17 baht/Kg , Electrical cost 3.7 baht / Kwh
NGV heating value @ 37.9 MJ/Kg

Energy analysis ( C65 CHP application with afterburner )
• Energy flow with CHP integrate system (micro turbine )
246.67 KW (fuel burn)
29 % GT efficiency 80 % boiler efficiency
341.6 KW of steam
generation
65 KW electrical generation
181.67 KW (exhaust gas)
246 KW (After burner)
427 KW (flue gas)
85.4 KW stack loss

Business analysis ( C65 CHP application with afterburner )
• Money flow with CHP integrate system (micro turbine )
400 baht/hr (fuel burn)
29 % GT efficiency 80 % boiler efficiency
341.6 KW of steam
generation
240 baht/hr electrical generation
400 baht/hr (After burner)
427 KW (flue gas)
85.4 KW stack lossPay 800 baht to generate 341.6 Kw
Generate 240 baht of electrical power
Profit = 750 - (800 -240 )
= 190 baht / hr /unit
= 1,641,600 baht / yr /unit

Thermal process analysis on electrical and steam generation
with direct burner
• Typical steam generation process
o Air / fuel was mixed and burned with burner
o Combustion hot gas temperature is nearly at adiabatic flame temperature
o Heat transfer characteristic in fire tube boiler is strongly depends on flame
temperature
• Heat transfer in fire tube boiler
o Radiation ( heat up tube surface of fire tube and hot gas )
o convection ( Transfer hot gas energy to water cooled tube surface )
o conduction ( Transfer energy from hot side tube surface to cool side )
• Hot gas temperature parameter is effect on heat transfer characteristic, boiler
capacity and boiler efficiency

Evaluation on boiler performance and efficiency on
combustion gas temperature and velocity (example)
• Employ dimensionless approach
o Heat transfer through the tube wall electrical circuit analogy
o Fire tube boiler TA is known, temperature of the combustion gas
o Water temperature TB is know, temperature saturated water
o h1 is known by dimensionless approach correlation of …
o h2 can remodel to conduction analogy using K water approach or other
available correlation can be employed.
o Effect of radiation will resulting in raising of T1

Hot gas temperature analysis on electrical and steam
generation with direct burner
• cogeneration application
Exhaust gas temperature was boosted by direct burner
• thermodynamics analysis (energy conservation )
The boosted exhaust gas temperature = (1-n)*(qin ) + (qad –qin ) / Cp air
Typical flue gas temperature = qad /Cp air
p
v

Thermal process analysis on electrical and steam generation
with direct burner
• Micro-turbine with 30% thermal efficiency
• There is 15 % in temperature drop comparing to conventional burner ( for 2000K
adiabatic temperature fuel )
• How can we estimate boiler performance and capacity deteriorate due to this
effect ?

Business opportunity analysis (compare with conventional boiler system )
80 Joule of steam generation
• Money flow with conventional boiler
100 baht (fuel burn)
80 % boiler efficiency 20 % stack loss
• Money flow with CHP integrate system (micro turbine )
xx baht (fuel burn)
xx baht electrical generation
29 % GT efficiency
xx baht (fuel burn)
80 % boiler efficiency
80 Joule of steam
generationxx joule (GT exhaust)

Heat transfer scaling law for systems prediction
• Example NGV fueled Micro-turbine with 30% thermal efficienc

Future development opportunity

Cogeneration project opportunity

Cogeneration project opportunity

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