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Steam Generation Efficiency

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Steam Generation Efficiency

Efficiency Definition

Radiation and Convection losses – Shell losses

Blowdown losses

Stack losses

Steam Generation Efficiency

Efficiency Definition

Radiation and Convection losses – Shell losses

Blowdown losses

Stack losses

- Steam generating unit efficiency is defined as the heat absorbed by the steam divided by the energy input with the fuel

- Boiler fired with natural gas which has a higher heating value of 23,311 Btu/lbm
- HHV is 1,000 Btu/sft³

- Steam conditions: 400 psig, 700°F
- Output: 100,000 lbm/hr (steady)
- Rating: 120,000 lbm/hr (maximum continuous)
- Feedwater: 600 psig, 242°F
- Fuel supply: 149,000 sft³/hr (2,480 sft³/min)
- Fuel cost: $10.00/10⁶Btu ($10.0/10³sft³)
- Determine the operating cost

Answer: Appendix

Answer: Appendix

- A typical boiler will have an efficiency of ----?

- A typical boiler will have an efficiency of ----?

75% to 82% to 90%

Wood Natural Gas Oil and Coal

Efficiency is dependent on the type of fuel and the installed equipment.

Answer: Appendix

- For the example boiler determine the steam generation efficiency.
- This is also called
- Boiler efficiency
- First law efficiency
- Fuel to steam energy conversion efficiency

This evaluation is also known as direct efficiency

Why is the efficiency not 100%?

Why is the efficiency not 100%?losses

Answer: Appendix

- Identify the Boiler losses

Exhaust Gases

Feedwater Inlet

Steam Outlet

Fuel and Air

Combustion and

Temperature

- Identify the Boiler losses

Feedwater Inlet

Steam Outlet

Exhaust Gases

Radiation and

Convection

Fly Ash

Blowdown

Fuel and Air

Bottom Ash

Answer: Appendix

- Boiler efficiency can also be determined in an indirect manner by determining the magnitude of the losses
- Primary losses are typically
- Shell loss
- Blowdown loss
- Stack loss

- Primary losses are typically

- American Society of Mechanical Engineers (ASME) has established a comprehensive testing standard for fired boilers
- ASME Power Test Code 4 (ASME PTC–4 )
- Fuel efficiency (the same as the classic equation)
- Gross efficiency (includes auxiliary input streams)

- ASME PTC–4 describes two investigation methods
- Input/output (direct method)
- Energy balance (indirect method)

- ASME Power Test Code 4 (ASME PTC–4 )