b1 maría sigríður guðjónsdóttir
TRANSCRIPT
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Thermoeconomic analysis of geothermal power cycles for IDDP-1 chloride mitigation
Alberto Mereto, María S. Guðjónsdóttir, Vijay Chauhan, Guðrún SævarsdóttirReykjavik University
Georg Geothermal WorkshopNovember 24th-25th 2016
#GGW2016
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Superheated steam h: 3150 kJ/kg
Potential power output: 30-40 MWe
Source: IDDP
IDDP-1
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Objectives - What is the problem?
• Geothermal fluid contains many minerals and non-condensable gases
• Corrosion is a major issue for the components of the plant: increase O&M, decrease useful life
• Mitigation techniques exist, but they have:– different techniques– different efficiencies– different costs
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Chloride-induced corrosion
• HCl becomes highly corrosive as it dissolves in water droplets• Reaction of HCl with magnetite film on the steel surface breaking the film:
• Two techniques of corrosion mitigation studied:– Chloride neutralization (wet scrubbing):
– Corrosion mitigation with binary cycle (corrosion is shifted)
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Single flash with wet scrubbing
Proposed power cyclesSingle flash with wet scrubbing and heat recovery
Single flash with wet scrubbing and and additional turbine
Binary cycle
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Thermoeconomics - Exergy• Important to develop thermal systems able to effectively use energy resources• Exergy represents the maximum theoretical useful work obtainable as two
systems interact to equilibrium. Specific exergy:
[kJ/kg] [kJ/kg] [K] [kJ/kgK]
• Exergy rate:
[kJ/s] [kg/s] [kJ/kg]
• Exergy can be destroyed and/or lost
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Thermoeconomics - Economics
• Every stream has a unit cost
[$/s] [$/kJ] [kJ/s]
• Every component has a product, a fuel and a capital cost
• Costs of loss and destruction attributed to product
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Cycle analysis
•
5•
𝑐6=𝑐5𝑐22=0
𝑐24=0
𝑐23=0
�̇�21=�̇�20+ �̇�𝐶𝑜𝑜𝑙𝑖𝑛𝑔𝑃𝑢𝑚𝑝 Total plant:
•
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Results – Heat recovery cycle
10 20 30 40 50 60 70 80 90 100 110 120 130 1400.0E+00
2.0E-05
4.0E-05
6.0E-05
8.0E-05
1.0E-04
1.2E-04
1.4E-04
1.6E-04
0E+00
2E-06
4E-06
ZHX SF: c3 HR: c5
Wellhead pressure (bar)
Cost
rate
($/s
)
Unit
cost
of e
xerg
y ($
/kJ)
Exergy rates in the heat recovery cycleHeat exchanger cost rate and comparison of unit cost of exergy entering the turbine between SF and HR
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Results – Cycles comparison
Net work output and unit cost of exergy of all the cycles
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Scenarios’ results - Heat recovery cycle
• Base case:– Well cost: 20 MUSD– O&M: 5%– Life time of plant: 25yrs– Interest rate: 4%
• Total cost of power output of base case at wellhead pressure 40bar: 0.01250 $/kWh
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Conclusions
• All the cycles aim at chloride mitigation in IDDP-1
• Best cycle to use for this purpose is the single flash with heat recovery
• HR produces the greatest amount of power among all cycles
• Wellhead pressure at which HR produces highest power output is also
the condition at which the power output has the lowest unit cost
• IDDP-1 was exceptionally expensive, but has exceptional potential
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Thank you for your attention!