A calcium carbonate scale inhibitor for direct-contact binary geothermal service
A 500-kW direct-contact binary-cycle pilot geothermal power plant was constructed and successfully operated free of scale at the U.S. DOE East Mesa geothermal test facility. The pilot plant used an Elgin tower directcontact heat exchanger (DCHX) with isobutane as the working fluid. Initial tests with the untreated 340/sup 0/F (170/sup 0/C) geothermal brine gave heavy calcium carbonate fouling of the brine boost pump, flow monitors, and flow-control valves within 20 to 50 hours of startup. Use of 2 ppm high-temperature polymeric scale inhibitor in the feed brine enabled plant operation for more than 700 hours without formation of detrimental scale. The antiscalant was not extracted into the working fluid and did not emulsify the hydrocarbon/brine interface. On the basis of dosage and flow, the additive cost was calculated to be about 0.06 per net kW-hr of power generated. Calcium carbonate scaling in a direct-contact binary-cycle geothermal power plant using up to 340/sup 0/F (170/sup 0/C) brine can be easily controlled with low dosages of a maleic terpolymer threshold antiscalant. This additive permits extended operation and reduces shutdown frequency for equipment maintenance. No significant additive/working-fluid interactions have been noted, although cleanout of prior scale gave a foamy suspension at the brine surface in the DCHX tower. The cost of using threshold antiscalant polymers in geothermal power plants suffering critical carbonate scaling is roughly an order of magnitude lower than the cost of periodic shutdown and cleaning. In this case, the additive cost was 0.06 /kW-hr of net power output, or 1.5% of power value. Use of such a thermally stable additive by downhole injection may enable greater utilization of liquid-dominated geothermal resources by permitting scale-free flow of two-phase fluid under artesian conditions.
- Research Organization:
- Pfizer Central Research
- OSTI ID:
- 6926972
- Journal Information:
- J. Pet. Technol.; (United States), Vol. 35:9
- Country of Publication:
- United States
- Language:
- English
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Calcium carbonate scale inhibitor for direct contact binary geothermal service
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Related Subjects
EAST MESA GEOTHERMAL FIELD
GEOTHERMAL POWER PLANTS
ANTIFOULANTS
SCALING
2-METHYLPROPANE
ADDITIVES
BINARY-FLUID SYSTEMS
BRINES
CALCIUM CARBONATES
COST BENEFIT ANALYSIS
DIRECT CONTACT HEAT EXCHANGERS
FOULING
HEAT TRANSFER FLUIDS
PILOT PLANTS
POLYMERS
SCALE CONTROL
ALKALINE EARTH METAL COMPOUNDS
ALKANES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATES
CONTROL
ENERGY SYSTEMS
FLUIDS
FUNCTIONAL MODELS
GEOTHERMAL FIELDS
HEAT EXCHANGERS
HYDROCARBONS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
POWER PLANTS
THERMAL POWER PLANTS
150903* - Geothermal Engineering- Corrosion
Scaling & Materials Development
150802 - Geothermal Power Plants- Power Plant Systems & Components