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. Classic Boiler Efficiency.

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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


Classic Boiler Efficiency

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


Operating Cost

  • 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


Boiler Operating Cost

Answer: Appendix


Steam Cost Indicator

Answer: Appendix


Typical Boiler Efficiency

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


Typical Boiler Efficiency

  • 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


Boiler Efficiency

  • For the example boiler determine the steam generation efficiency.

  • This is also called

    • Boiler efficiency

    • First law efficiency

    • Fuel to steam energy conversion efficiency


Efficiency Example Steam Properties


Direct (Classic) Efficiency Calculation

This evaluation is also known as direct efficiency


Efficiency Calculation

Why is the efficiency not 100%?


Efficiency Calculation

Why is the efficiency not 100%?losses

Answer: Appendix


Boiler Losses

  • Identify the Boiler losses

Exhaust Gases

Feedwater Inlet

Steam Outlet

Fuel and Air


Boiler Losses

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


Indirect Efficiency

  • 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


ASME Boiler Efficiency

  • 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)


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