High-pressure Aqueous Environments Research Articles

Thermodynamic Modeling of Mineral Scaling in High-Temperature and High-Pressure Aqueous Environments

Methods of predicting mineral scale formation have evolved over the years from simple empirical fittings to sophisticated computational programs. Though best practices can now solve complex multi-phase, multi-component systems, they are largely restricted to temperatures below 300 °C. This review examines critical gaps in existing mineral scale modeling approaches as well as strategies to overcome them. Above 300 °C, the most widely used model of standard thermodynamic functions for aqueous species fails when fluid densities are below 0.7 g cm−3. This failure occurs due to the model’s reliance on an empirical form of the Born equation which is unable to capture the trends observed in these high temperature, low density regimes. However, new models based on molecular solvent-solute interactions offer a pathway to overcome some of the deficiencies currently limiting high-temperature and high-pressure mineral scale predictions. Examples of the most common scale prediction methods are presented, and their advantages and disadvantages are discussed.

Hydrothermal corrosion of laser printed SiC fibers under extreme environment

SiC/SiC fiber composites are proposed cladding materials to improve the accident tolerance of commercial light water nuclear reactor fuel. To evaluate their viability, understanding the kinetics of corrosion under irradiation and high-temperature, high-pressure aqueous environment is critical. In the present work, the microstructure and mechanical properties of novel SiC fibers manufactured by Laser Chemical Vapor Deposition (LCVD) are introduced. The LCVD technology has control over microstructure and stoichiometry while allowing for high purity manufacturing, all key qualities needed in search of an optimum SiC fiber for nuclear energy applications. The isolated hydrothermal corrosion of commercially available carbon-rich Hi-Nicalon Type-S fibers is compared to the LCVD stoichiometric and LCVD silicon-rich fibers. Autoclave testing was carried out at 310°C and 14 MPa in the absence of irradiation. In a separate study, the effect of gamma irradiation on the fibers in the room-temperature environment was analyzed. It was observed from the experiments that the dissolution of the fibers was highly dependent on the stoichiometric ratio, fiber surface morphology and thermal pre-treatment of fibers. Contrary to previous findings, fiber dissolution was also visible under low-temperature gamma irradiation in aqueous environment with LCVD fibers showing lower dissolution.

Effects of hollow microsphere surface property on the mechanical performance of high strength syntactic foams

Syntactic foams (SF) with robust impermeable hollow microspheres as density adjuster have drawn much attention because of their easy-tailored low density, high mechanical strength and excellent performance especially when used in high pressure aqueous environment. In this work, specially fabricated hollow silicate glass microspheres (HSMs) with high strength to weight ratio were employed for the controlled fabrication of high strength lightweight syntactic foams. Special attention has been paid on the effects of surface physicochemical status modification of the HSMs on the mechanical strength and mechanical performance evolution in various external environments. It is found that the surface physicochemical status modification of the HSMs contributes more on the enhancement of the fracture toughness compared with that of the compressive strength. Moreover, compared with those of the pristine SF, the mechanical strength of the SF samples after different environmental exposure display a more remarkable improvement due to the surface physicochemical status modification of the HSMs, indicating an enhanced environmental stability. This work provides an additional insight to the mechanical strength and aging resistance control of SF, which holds the potential to be extended to the property improvement of similar composites with various types of silicate or glass fillers.

Effect of oxide film on ECT detectability of surface IGSCC in laboratory-degraded alloy 600 steam generator tubing

Abstract Stress corrosion cracking (SCC) widely found in both primary and secondary sides of steam generator (SG) tubing in pressurized water reactors (PWR) has become an important safety issue. Using eddy-current tests (ECTs), non-destructive evaluations are performed for the integrity management of SG tubes against intergranular SCC. To enhance the reliability of ECT, this study investigates the effects of oxide films on ECT’s detection capabilities for SCC in laboratory-degraded SG tubing in high temperature and high pressure aqueous environment.

Formation of hydrous stishovite from coesite in high-pressure hydrothermal environments

The dramatic change in properties of water near its critical point (i.e. T = 374 °C and p = 22.1 MPa, note: 100 MPa = 0.1 GPa = 1 kbar ≈ 1000 atm) has been a subject of numerous studies and also lead to the development of various applications (e.g. in waste destruction, biomass processing, and the synthesis of advanced ceramic materials). However, comparatively little is known about the behavior of water at gigapascal pressures. The present study attempts to explore catalytical properties and reactivity of extreme water with respect to several oxide systems: SiO2, TiO2 and LiAlSiO4. “Extreme water” here is defined as existing at p,T conditions of 0.25–10 GPa and 200–1000 °C, thus considering both supercritical fluid and hot compressed ice. The study shows that extreme water can make high pressure mineral phases accessible at relatively mild T conditions. At the same time, high pressure aqueous environments appear efficient in stabilizing novel metastable structures and may be considered as a general route for synthesizing new materials.The hydrothermal treatment of SiO2 glass at 10 GPa and 300–550 °C yielded an unusual ultrahydrous form of stishovite with up to 3% of structural water. At the same time, the extreme water environment enhanced notably the kinetics of stishovite formation, making it accessible at unprecedentedly low temperatures. Thus, for the SiO2–H2O system water acts as both catalyst and reactant. For TiO2 a hydrothermal high pressure treatment proved to be of high importance for overcoming the kinetical hindrance of the rutile – TiO2-II transformation. 6 GPa and 650 °C were established as the mildest conditions for synthesizing pure TiO2-II phase in less than two hours. The crystallization of LiAlSiO4 glass in an extreme water environment yielded a number of different phases. In the low pressure region (0.25 – 2 GPa) mainly a zeolite (Li-ABW) and a dense anhydrous aluminosilicate (α-eucryptite) were obtained. At pressures above 5 GPa the formation of novel pyroxene-like structures with crystallographic amounts of structural water was observed.The overall conclusion of this study is that extreme water environments show a great potential for catalyzing phase transitions in oxide systems and for stabilizing novel structures via structural water incorporation.

Copper-Copper Sulfate Reference Electrode for Operating in High Temperature and High Pressure Aqueous Environments

A copper-copper sulfate electrode (CSE) was constructed and tested at elevated temperatures. Experimental cell potentials versus a silver-silver chloride electrode were compared against results from Gibbs energy minimization (GEM) calculations. After accounting for irreversible thermodynamic processes, experimental and calculated CSE potentials, were generally within 3% of the observed potential from 25 to 150°C at 3MPa. The CSE potentials changed by less than 20mV with increasing temperature, compared to 120mV for the silver-silver chloride electrode. With its repeatability and small temperature dependence, the CSE electrode appears to be a viable reference electrode for measuring in-situ real time cell potentials in aqueous phase-containing media at elevated temperature and pressure.

An experimental study of deposition of suspended magnetite in high temperature-high pressure boiler type environments

Fouling in boilers has been a problem for decades. In addition to iron oxide deposits on tube walls impeding heat transfer, some forced circulation boilers experience magnetite deposition in lower orifices. These deposits impede flow, cause inefficiencies and lead to boiler tube failures from overheating and corrosion. Particle deposition in some boiler/reactor type environments has been attributed to particle transport and the probability of particle attachment. The attachment is governed by both the inter-particle and particle-substrate interactions, which depend on the aqueous environment. In this study, a novel experimental system is presented, which focusses on the particle attachment aspect of the deposition issues observed in boiler type environments. To identify the effect of boiler water chemistry on the deposition of suspended magnetite on stainless steel, a high temperature high pressure electrophoretic deposition cell with provisions to test metal substrates and different chemistries was developed. Tests were conducted at pH25°C of 9.3 in simulated boiler conditions in terms of temperature, pressure and water chemistry. In addition to visual observations, the deposition was investigated using in-situ Electrochemical Impedance Spectroscopy (EIS) and post-test surface analyses including Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). As predicted by Derjaguin-Landau-Verwey- Overbeek (DLVO) theory, deposition was confirmed possible in the above-mentioned aqueous environment at 300°C. The experimental system presented here was successful in simulating boiler type environments with accelerated deposition. The capability to understand particulate fouling and also to study interfacial phenomena in high temperature, high pressure aqueous environments has been demonstrated.

Corrosion of C110 carbon steel in high-pressure aqueous environment with mixed hydrocarbon and CO2 gas

Corrosion is a major issue in the oil industry, especially in presence of aqueous carbon dioxide under high-pressure high-temperature (HPHT) conditions. Exposing tubular materials to aqueous CO2 (carbonic acid) environment causes severe corrosion. This paper presents results of an experimental study conducted to investigate effects of CO2 partial pressure ratio (i.e. ratio of CO2 partial pressure to the total pressure) and total pressure on corrosion behavior of C110 carbon steel. In addition, effect of CO2 corrosion on mechanical strength was investigated to identify presence of microscopically undetectable localized corrosion such as intergranular attack that can cause substantial mechanical degradation.To perform corrosion experiments, test specimens were cut from C110 casing and machined. In order to improve accuracy and reduce machining-induced defects, water-jet cutting and milling machines were utilized. Corrosion tests were conducted by exposing the specimens (three specimens in one batch) to 2% NaCl solution saturated with mixed gas containing CH4 and CO2. CO2 partial pressure ratio (CPPR) and total system pressure were varied. Tests were performed at a constant temperature (38±1°C) for one week duration. Corrosion rate was measured using weight loss technique. In addition, corroded specimens were examined using a digital microscope to inspect corrosion product and detect presence of localized corrosion. Localized corrosion is known for degrading mechanical properties of carbon steel. To identify existence of undetectable localized corrosion, the specimen load-carrying-capacity (LCC) was measured using tensile strength measuring apparatus.When CPPR was varied from 0 to 100%, similar corrosion rate trends were observed at 41.37 and 62.05MPa. Corrosion rate increased to a maximum value and subsequently decreased as the CPPR was increased to 100%. A dense and compact corrosion product was formed at 41.37MPa and 100% CPPR. To detect presence of localized corrosion, total reduction in Load Carrying Capacity (LCC) and reduction in LCC due to uniform corrosion were determined and compared. Results show no mechanical property degradation after exposure indicating absence of localized corrosion. The total reduction was slightly higher than the reduction due to uniform corrosion. One possible explanation for this observation could be minor variation of corroded specimen thickness, which resulted in underestimation of LCC reduction due to uniform corrosion.

Reference Electrodes for electrochemical measurements in high-temperature high-pressure aqueous environments—Review of potential corrections for ‘external’ reference systems

Corrosion studies in high-temperature high-pressure aqueous environments, and in particular electrochemical corrosion measurements in these environments, are again becoming more important for a number of industrial applications. Reliable and accurate electrochemical measurements in high-temperature high-pressure aqueous systems (i.e. up to ca. 300°C) are, however, not straightforward. Especially the stability of so-called ‘internal’ reference electrode systems or the accuracy of ‘external’ reference systems continues to pose major measurement problems.In this paper we will present a brief state-of-the-art, and we will demonstrate the possibility of transforming the huge amount of correction data for external reference electrode systems into one simple analytical expression, at least for neutral and alkaline solutions. For acidic solutions, there is a small deviation. Precisions of the order of ±5 to 15mV (depending on the temperature) can generally be obtained, which should be sufficient for applications like corrosion monitoring, redox potential measurements, etc.

Electrochemical characterization of nano zinc ferrite coating on carbon steel by pulsed laser deposition

The structural materials in water-cooled nuclear power reactors are mainly iron and nickel based alloys. Continuous operation of these nuclear reactors at high temperature and high pressure aqueous environment leads to the formation of various oxides due to corrosion of the structural materials. Since the corrosion process is mainly interfacial and electrochemical in nature, the interfaces formed between the alloys/oxide and oxide/solution plays a crucial role in deciding the overall corrosion resistance of the structural materials. In this context, efforts are being made to modify the size of the oxide particles (surface morphology) to nano size and/or change the composition of the oxides by the addition of an external metal ion (Metal Ion Passivation) both of which are likely to improve the adherence and protectiveness of the interfacial film. In this paper, attempts were made to form an additional nano zinc ferrite (ZnFe2O4) coating by pulsed laser deposition technique on the magnetite (Fe3O4) layer formed on carbon steel for improving the corrosion resistance of the base metal. The ZnFe2O4 was synthesized by co-precipitation method and its phase purity was confirmed by Raman Spectroscopy and X-Ray Diffraction studies. 10mm diameter ferrite targets were prepared and a thin film of ZnFe2O4 was deposited on the Fe3O4 coated carbon steel specimens using pulsed laser deposition technique. Characterization of this deposited ferrite film was carried out by Raman spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy and Secondary Electron Microscopy. The semiconductor properties of these oxides were investigated by Mott-Schottky plots. The mechanism of corrosion resistance/improvement in the deposited layer was studied by electrochemical techniques and the results are presented in detail in this paper.

Chemical Processing in High-Pressure Aqueous Environments. 9. Process Development for Catalytic Gasification of Algae Feedstocks

Through the use of a metal catalyst, gasification of wet algae slurries can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 °C). In a pressurized-water environment (20 MPa), near-total conversion of the organic structure of the algae to gases has been achieved in the presence of a supported ruthenium metal catalyst. The process is essentially steam reforming, as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium-heating value gas due to the synthesis of high levels of methane, as dictated by thermodynamic equilibrium. As opposed to earlier work, biomass trace components were removed by processing steps so that they did not cause processing difficulties in the fixed catalyst bed tubular reactor system. As a result, the algae feedstocks, even those with high ash contents, were much more reliably processed without plugging the feeding systems or the fixed catalyst bed. High conversions were obtained even with high slurry concentrations. Consistent catalyst operation in these short-term tests suggested good stability and minimal poisoning effects. High methane content in the product gas was noted with significant carbon dioxide captured in the aqueous byproduct in combination with alkali constituents and the ammonia byproduct derived from proteins in the algae. High conversion of algae to gas products was found with low levels of byproduct water contamination and low to moderate loss of carbon in the mineral separation step. Further development is required to demonstrate protection of the catalyst bed from sulfur poisoning.

Investigation of oxide film formation on 316L stainless steel in high-temperature aqueous environments

Oxide films were grown on the surface of 316L stainless steel subjected to high temperatures and a high-pressure aqueous environment (250 °C and 7 MPa). The morphology, chemical compositions and corrosion properties of oxide films were investigated by scanning electron microscopy (SEM), auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The results indicated that oxide films formed at 250 °C were more corrosion resistant and thicker than were oxide films formed in air at room temperature (25 °C). These distinctions are correlated with the structure and chemical compositions of oxide films. It was found that both films contained a double-layer structure comprised of mixed iron–nickel oxides and chromium oxides. Iron was present as FeO, Fe 2O 3 and FeOOH; Cr was present as Cr 2O 3, Cr(OH) 3 and CrO 3; and Ni existed as Ni(OH) 2 within the oxide films formed at 250 °C.

Double pulse laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: interrelationship of gate delay, pulse energies, interpulse delay, and pressure

Laser-induced breakdown spectroscopy (LIBS) has been identified as an analytical chemistry technique suitable for field use. We use double pulse LIBS to detect five analytes (sodium, manganese, calcium, magnesium, and potassium) that are of key importance in understanding the chemistry of deep ocean hydrothermal vent fluids as well as mixtures of vent fluids and seawater. The high pressure aqueous environment of the deep ocean is simulated in the laboratory, and the key double pulse experimental parameters (laser pulse energies, gate delay time, and interpulse delay time) are studied at pressures up to 2.76x10(7) Pa. Each element is found to have a unique optimal set of parameters for detection. For all pressures and energies, a short (< or = 100 ns) gate delay is necessary. As pressure increases, a shorter interpulse delay is needed and the double pulse conditions effectively become single pulse for both the 1.38x10(7) Pa and the 2.76x10(7) Pa conditions tested. Calibration curves reveal the limits of detection of the elements (5000 ppm Mg, 500 ppm K, 500 ppm Ca, 1000 ppm Mn, and 50 ppm Na) in aqueous solutions at 2.76x10(7) Pa for the experimental setup used. When compared to our previous single pulse LIBS work for Ca, Mn, and Na, the use of double pulse LIBS for analyte detection in high pressure aqueous solutions did not improve the limits of detection.

Sequential-Pulse Laser-Induced Breakdown Spectroscopy of High-Pressure Bulk Aqueous Solutions

Sequential-pulse (or dual-pulse) laser-induced breakdown spectroscopy (DP-LIBS) with an orthogonal spark orientation is described for elemental analysis of bulk aqueous solutions at pressures up to approximately 138 x 10(5) Pa (138 bar). The use of sequential laser pulses for excitation, when compared to single-pulse LIBS excitation (SP-LIBS), provides significant emission intensity enhancements for a wide range of elements in bulk solution and allows additional elements to be measured using LIBS. Our current investigations of high-pressure solutions reveal that increasing solution pressure leads to a significant decrease in DP-LIBS emission enhancements for all elements examined, such that we see little or no emission enhancements for pressures above 100 bar. Observed pressure effects on DP-LIBS enhancements are thought to result from pressure effects on the laser-induced bubble formed by the first laser pulse. These results provide insight into the feasibility and limitations of DP-LIBS for in situ multi-elemental detection in high-pressure aqueous environments like the deep ocean.

Chemical Processing in High-Pressure Aqueous Environments. 8. Improved Catalysts for Hydrothermal Gasification

Improved catalyst formulations have been developed and tested for hydrothermal gasification of wet organics. A high-pressure (about 20 MPa) and high-temperature (about 350 °C) liquid water processing environment was used to treat organic chemical model compounds. The organic feedstocks were converted primarily to methane and carbon dioxide in the presence of a heterogeneous catalyst. Test results with different catalyst formulations showed that catalyst composition could be tailored for the hydrothermal environment to effectively process wet wastes and wastewater and to recover useful fuel gas.

Chemical Processing in High-Pressure Aqueous Environments. 7. Process Development for Catalytic Gasification of Wet Biomass Feedstocks

Through the use of a metal catalyst, gasification of wet biomass can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 °C). In a pressurized-water environment (20 MPa), near-total conversion of the organic structure of biomass to gases has been achieved in the presence of a ruthenium metal catalyst. The process is essentially steam reforming, as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium heating value gas due to the synthesis of high levels of methane, as dictated by thermodynamic equilibrium. While good gas production was demonstrated, biomass trace components caused some processing difficulties in the fixed catalyst bed tubular reactor system used for the catalytic gasification process. Results are described for tests using both bench-scale and scaled-up reactor systems.

Chemical Processing in High-Pressure Aqueous Environments. 6. Demonstration of Catalytic Gasification for Chemical Manufacturing Wastewater Cleanup in Industrial Plants

Catalytic gasification of organics has been demonstrated at the engineering development scale as an option for chemical manufacturing wastewater cleanup. A high-pressure (about 20 MPa) and high-temperature (about 350 °C) liquid water processing environment was used to treat wastewaters at two industrial sites. Organic byproducts from chemical manufacturing were converted primarily to methane and carbon dioxide in the presence of a fixed bed of nickel/ruthenium catalyst. Test results with chemical manufacturing wastewater streams showed that this process could be effectively used with the appropriate catalyst to clean up wastewater and recover waste organics as useful fuel gas. Preliminary process economics were determined.

Chemical Processing in High-Pressure Aqueous Environments. 5. New Processing Concepts

A combination of fundamental and applied process research at Pacific Northwest National Laboratory resulted in the development of several new processing concepts. These concepts have in common the use of high-temperature pressurized water as a unique reaction medium for carrying out chemical reactions. Typical operating conditions of these processes range from 300 to 360 °C and have pressures to above 200 bar. Investigation of the process chemistry and engineering for these new processing concepts required the development and scale-up of several high-pressure reactor systems which are described. Several new processes involving catalysts and the distinctive properties of pressurized water were patented as part of this effort. These processes, which are at various stages of development, address a broad mix of energy and environmentally related problems. Chemical processing in a high-temperature liquid water environment remains a relatively untapped area for commercial application.

Meteorite organics in planetary environments: hydrothermal release, surface activity, and microbial utilization

Up to 50% of the organics in the Murchison meteorite, possibly including some of the polymer, is released in high temperature and pressure aqueous environments, to 350°C and 250 bar, that simulate submarine volcanic, hydrothermal or impact-induced conditions. Meteorite organics of prebiotic significance, such as nonanoic acid, glycine, and pyrene survive the hydrothermal conditions. The released material is surface active with surface pressures up to 19.8 × 10 −3 N m −1, and exhibits an extended surface tension isotherm which suggests a mixture of amphiphilic components. One component, nonanoic acid, is shown to form vesicles. The materials extracted under mild conditions, at 120°C, are nutrients for the humic acid bacterium Pseudomonas maltophilia and efficient nutrients for the oligotroph Flavobacterium oryzihabitans, demonstrating the capability of micro-organisms to metabolize extraterrestrial organics.

Chemical Processing in High-Pressure Aqueous Environments. 4. Continuous-Flow Reactor Process Development Experiments for Organics Destruction

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemical Processing in High-Pressure Aqueous Environments. 4. Continuous-Flow Reactor Process Development Experiments for Organics DestructionDouglas C. Elliott, M. R. Phelps, L. John Sealock Jr., and Eddie G. BakerCite this: Ind. Eng. Chem. Res. 1994, 33, 3, 566–574Publication Date (Print):March 1, 1994Publication History Published online1 May 2002Published inissue 1 March 1994https://doi.org/10.1021/ie00027a013RIGHTS & PERMISSIONSArticle Views632Altmetric-Citations100LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts