Experimental CaCO3 scaling of different substrate materials: Unravelling the effects of temperature, corrosion, crystal nucleation and growth

Research output: Contribution to conferencePosterResearchpeer-review

Abstract

Thermal water is increasingly used for heat and electric
power production and provides base-load capable renewable
and virtually unlimited geothermal energy. The generally
highly mineralized deep thermal water can, however, induce
the formation of mineral precipitates along the water circuit
of geothermal power plants, which can considerably impact
on the plant’s efficiency. In order to explore the processes and
effects of temperature, corrosion, crystal nucleation and
growth on carbonate (CaCO3) scaling, we performed basic
laboratory experiments, in which we exposed different
substrate materials (e.g. corroded and uncorroded carbon steel
coupons) to synthetic geothermal solutions at temperatures
ranging from 30 to 90°C. The incorporation of divalent Mg
and Sr cations into the precipitated carbonate scales are
thereby investigated as environmental proxies. Fluid
chemistry and solid phase analysis (e.g. XRD, FT-IR, SEM)
complement our approach.
The experiments, based on solid and liquid phase
analysis, as well as variable Mg/Ca and Sr/Ca ratios, revealed
a strongly temperature-dependent precipitation behaviour of
different CaCO3 polymorphs (calcite, aragonite, vaterite) also
depending on the particular substrate being present. At lower
and intermediate temperatures, stainless steel and polyamide
substrates seem to favour calcite formation, whereas the
carbon steel substrate supports aragonite formation. Vaterite
formation is clearly promoted by polyamide substrates.
Contrary to observed wall crystallization on substrates,
homogenous (particulate) nucleation of aragonite further
occurs from aqueous solution. Importantly, the different
polymorphs and crystallization modes result in a strong effect
on the actual scale material characteristics, e.g. density,
mechanical and chemical resistance. Our experimental results
clearly indicate that CaCO3 crystal nucleation and growth, as
well as element fractionation strongly depend on the materials
used in geothermal applications.
Original languageEnglish
Publication statusPublished - 14 Aug 2017
EventGoldschmidt Conference - Le Palais des Congrès, Paris, France
Duration: 13 Aug 201718 Aug 2017

Conference

ConferenceGoldschmidt Conference
CountryFrance
CityParis
Period13/08/1718/08/17

Fields of Expertise

  • Advanced Materials Science

Cite this

Experimental CaCO3 scaling of different substrate materials: Unravelling the effects of temperature, corrosion, crystal nucleation and growth. / Hippler, Dorothee; Simic, Sanja; Boch, Ronny.

2017. Poster session presented at Goldschmidt Conference, Paris, France.

Research output: Contribution to conferencePosterResearchpeer-review

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AU - Hippler, Dorothee

AU - Simic, Sanja

AU - Boch, Ronny

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N2 - Thermal water is increasingly used for heat and electricpower production and provides base-load capable renewableand virtually unlimited geothermal energy. The generallyhighly mineralized deep thermal water can, however, inducethe formation of mineral precipitates along the water circuitof geothermal power plants, which can considerably impacton the plant’s efficiency. In order to explore the processes andeffects of temperature, corrosion, crystal nucleation andgrowth on carbonate (CaCO3) scaling, we performed basiclaboratory experiments, in which we exposed differentsubstrate materials (e.g. corroded and uncorroded carbon steelcoupons) to synthetic geothermal solutions at temperaturesranging from 30 to 90°C. The incorporation of divalent Mgand Sr cations into the precipitated carbonate scales arethereby investigated as environmental proxies. Fluidchemistry and solid phase analysis (e.g. XRD, FT-IR, SEM)complement our approach.The experiments, based on solid and liquid phaseanalysis, as well as variable Mg/Ca and Sr/Ca ratios, revealeda strongly temperature-dependent precipitation behaviour ofdifferent CaCO3 polymorphs (calcite, aragonite, vaterite) alsodepending on the particular substrate being present. At lowerand intermediate temperatures, stainless steel and polyamidesubstrates seem to favour calcite formation, whereas thecarbon steel substrate supports aragonite formation. Vateriteformation is clearly promoted by polyamide substrates.Contrary to observed wall crystallization on substrates,homogenous (particulate) nucleation of aragonite furtheroccurs from aqueous solution. Importantly, the differentpolymorphs and crystallization modes result in a strong effecton the actual scale material characteristics, e.g. density,mechanical and chemical resistance. Our experimental resultsclearly indicate that CaCO3 crystal nucleation and growth, aswell as element fractionation strongly depend on the materialsused in geothermal applications.

AB - Thermal water is increasingly used for heat and electricpower production and provides base-load capable renewableand virtually unlimited geothermal energy. The generallyhighly mineralized deep thermal water can, however, inducethe formation of mineral precipitates along the water circuitof geothermal power plants, which can considerably impacton the plant’s efficiency. In order to explore the processes andeffects of temperature, corrosion, crystal nucleation andgrowth on carbonate (CaCO3) scaling, we performed basiclaboratory experiments, in which we exposed differentsubstrate materials (e.g. corroded and uncorroded carbon steelcoupons) to synthetic geothermal solutions at temperaturesranging from 30 to 90°C. The incorporation of divalent Mgand Sr cations into the precipitated carbonate scales arethereby investigated as environmental proxies. Fluidchemistry and solid phase analysis (e.g. XRD, FT-IR, SEM)complement our approach.The experiments, based on solid and liquid phaseanalysis, as well as variable Mg/Ca and Sr/Ca ratios, revealeda strongly temperature-dependent precipitation behaviour ofdifferent CaCO3 polymorphs (calcite, aragonite, vaterite) alsodepending on the particular substrate being present. At lowerand intermediate temperatures, stainless steel and polyamidesubstrates seem to favour calcite formation, whereas thecarbon steel substrate supports aragonite formation. Vateriteformation is clearly promoted by polyamide substrates.Contrary to observed wall crystallization on substrates,homogenous (particulate) nucleation of aragonite furtheroccurs from aqueous solution. Importantly, the differentpolymorphs and crystallization modes result in a strong effecton the actual scale material characteristics, e.g. density,mechanical and chemical resistance. Our experimental resultsclearly indicate that CaCO3 crystal nucleation and growth, aswell as element fractionation strongly depend on the materialsused in geothermal applications.

M3 - Poster

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