The document describes Colorado Golden Energy's extraction steam turbine model for cogeneration plants. The model splits the turbine into two imaginary turbines - an extraction-only turbine and a straight-to-condenser turbine. It uses mass and energy balance equations to model the extraction of 50# and 400# steam from each turbine. The model outputs the extraction turbine power output, the power needed to meet total demand, and calculates the overall turbine efficiency based on extraction loads. The goal is to provide a simple yet accurate model of how extraction loads impact plant efficiency.

1. Colorado Golden Energy’s Extraction Steam Turbine Model
June 2012

2. CGE Extraction Steam Turbine Model
• CGE : a COGENERATION plant
– Simultaneous production of power and heat (50# and 400# steam)
– Max Efficiency when steam flows to condensers are minimized
 Higher extraction loads → Higher Plant Efficiency
 Best Efficiency when 50# loads are highest
– 400# and 50# Steam extracted from TG1 and TG2 to maintain 400# and 50#
header pressures
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3. • A demand-driven model:
– User inputs are :
 400# & 50# extraction flows
 Power
– Splits the real turbine in 2 imaginary turbines
 An extraction-only turbine with no flow to condenser
 A straight-to-condenser turbine with no extraction
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CGE Extraction Steam Turbine Model

4. • Extraction-Only Turbine Model:
– Mass Balance :
(i) f800 to extrac = f400 + f50
– Energy Balance :
Q800 to extrac = Q400 + Q50 + MWextrac
MWextrac = Q800 to extrac - Q400 - Q50
(ii) MWextrac = 0.9 x (H800 x f800 to extrac - H400 x f400 - H50 x f50)
“TG1 Ideal Load Equation” with 90% alternator efficiency to convert
mechanical energy to electricity.
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CGE Extraction Steam Turbine Model
f800 to extrac, Q800 to extrac
f400 , Q400
f50 , Q50
MWextrac

5. • Straight-to-condenser Turbine Model:
– Energy Balance :
accounts for Power production in excess of “Ideal Load” produced by extraction-
only turbine
MWextra Dmnd = MWTotal Dmnd – MWextrac
MWextra Dmnd = Q800 to cond - Qcond
(iii) MWextra Dmnd = 0.9 x f800 to cond x (H800 - Hcond)
– Mass Balance :
(iv) f800 to cond = fcond
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CGE Extraction Steam Turbine Model
f800 to cond, Q800 to cond
fcond, Qcond
MWextra Dmnd

6. • Recombined Turbine Model:
– Mass Balance :
f800 total = f800 to extrac + f800 to cond
f800 total = f400 + f50 + f800 to cond
– Energy Balance :
Q800 = Q800 to extrac + Q800 to cond
Q800 = Q400 + Q50 + MWextrac + MWextra Dmnd + Qcond
Q800 = H400 x f400 + H50 x f50 + MWtot + Hcond x fcond
Result :
a sensible and easy-to-implement set of formulas satisfying Mass, Energy Balances
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CGE Extraction Steam Turbine Model
f800 totaL, Q800
f400 , Q400
f50 , Q50
MWtot
fcond, Qcond

7. • CGE : extraction loads and their impact on plant efficiency
– Impact on TG1’s thermal and electrical efficiency
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75.00
80.00
85.00
90.00
95.00
100.00
0.75 0.77 0.79 0.81 0.83 0.85 0.87 0.89 0.91 0.93 0.95
Efficiency [%]
[(50# + 400#) Extraction / 800# Inlet] Ratio
TG1 - Efficiency vs [Extraction/Inlet] Ratio
Reality vs Model
CGE Extraction Steam Turbine Model