High-temperature Salt Research Articles

Changing the Structure of a Single-Crystal Ni-Based Superalloy During Its High-Temperature Salt Corrosion at 750°C

Changing the Structure of a Single-Crystal Ni-Based Superalloy During Its High-Temperature Salt Corrosion at 750°C

Investigation of a novel combined ab- and ad- sorption based thermal energy storage and upgrade system

This paper presents a novel sorption-based cycle combining energy storage with energy upgrade to store low-grade heat for long periods and transform it on demand to usable energy at elevated temperatures. The system consists of an ammonia-water absorption system coupled to a resorption thermal transformer using manganese chloride and calcium chloride as the working pair with an ammonia absorbate. The absorption and adsorption systems are charged by separating the constituent sorbent-sorbate pairs, and they remain separated during the transition season. The discharge consists of a two-stage sorption process between the two systems. This work presents a transient thermodynamic model and analysis of the two-stage sorption system. For a typical solar thermal energy input of 106 °C during charging, and ambient temperatures of 5 °C and 25 °C in the winter and summer, respectively, the system is capable of discharging at an average elevated temperature of 62 °C with an energy storage efficiency of 27 %. This system is capable of simultaneously producing heat at a lower temperature by varying the mass flow rate through the high-temperature salt. The energy storage density of the combined system under different conditions is between 71 and 185 kJ kg−1. In comparison with other conventional single-stage thermal energy storage systems, this combination of absorption and adsorption-based storage provides a higher coefficient of performance for a comparable temperature output.

Designing brazing filler metal for heat-resistant nickel alloys of new generation marine gas turbines

The object of research is the processes of the formation of brazed joints and the stressed state. The subject of research is structure, chemical composition, long-term high-temperature strength at a temperature of 900 °C, speed of high-temperature salt corrosion. Existing brazing filler metals have a high-temperature performance of 40–50 % of the performance of the SM93-VI and SM96-VI alloys. Despite this, brazing is the main technique of joining modern heat-resistant cast alloys. Therefore, the development of new brazing filler metals that ensure the formation of joints with increased long-term high-temperature strength is relevant. Ship gas turbine blades operate at a temperature of 900 °C. The purpose of the development of the new SBM-4 brazing filler metal is to achieve long-term high-temperature strength of brazed joints at a temperature of 900 °C at the level of 85–90 % of the strength of heat-resistant alloys SM93-VI and SM96-VI. A two-stage method was used in the development of SBM-4 brazing filler metal. At the first stage, the chemical composition of the brazing filler metal base was determined, taking into account the peculiarities of operating conditions of the blades of marine gas turbine engines and the achievements of materials science of heat-resistant alloys. At the second stage, the depressant and its necessary content were selected. Computer software was used to determine the distribution between the γ- and γ'-phases, taking into account the participation of each element in both dispersion and solid-solution strengthening. Rational limits of concentrations of alloying elements were determined. The criterion was the minimum susceptibility of brazing filler metal to the formation of brittle phases, taking into account the influence of chromium, rhenium, and tantalum concentrations on resistance to high-temperature salt corrosion and high-temperature performance. The long-term strength of SM93-VI and CM96-VI alloys brazed with SBM-4 brazing filler metal is 89–91 % of the strength of the base metal. Technologies of brazing and correction of casting defects have been introduced into production.

Design and manufacture of a proof-of-concept resorption heat pump using ammonia-salt chemisorption reactions

Using the Large Temperature Jump (LTJ) experimental technique, alongside a review of the literature, sodium bromide (NaBr) and manganese chloride (MnCl2) have been identified as a suitable working pair with ammonia refrigerant for a proof-of-concept resorption heat pump system. LTJ tests using a tube-side and shell-side unit cell reactor (sorption heat exchanger), show that the experimentally obtained equilibrium lines for adsorption and desorption of sodium bromide are: ΔHADS = 30,102.5 J/mol; ΔSADS = 207.7 J/(mol·K); ΔHDES = 30,216.4 J/mol; and ΔSDES = 206.8 J/(mol·K). Using a semi-empirical model, the NaBr composite salt (salt impregnated in expanded natural graphite (ENG)) has been characterised for use as a low temperature salt in a resorption heat pump, with manganese chloride as the high-temperature salt. The model constants, A and n, for adsorption are 1 and 3, and for desorption are 5 and 4 respectively for NaBr. Manganese chloride data has been previously reported (Hinmers et al., 2022). With an appreciation of the reaction dynamics and behaviour of the NaBr and MnCl2 composite salts, a proof-of-concept resorption system has been designed and manufactured. The reactor design, alongside the overall experimental rig design (including data acquisition system) is reported. Initial filling and flushing tests show the success of the data acquisition and control system, and thus the overall suitability of the proof of-concept system for investigations into the coupled nature of ammonia salt reactions for a resorption heat pump application.

Seasonal dynamics of evaporite mineral precipitation, dissolution, and back-reactions in shallow and deep hypersaline lakes

Seasonal water temperature variations exhibit a first-order control on the mineralogy, texture, and timing of formation of modern, temperate zone lacustrine evaporites. However, seasonality is generally absent from the thermochemical models used to interpret ancient nonmarine evaporites. Here, a seasonal model is presented which correctly reproduced the complex history of evaporite precipitation, dissolution, and back-reactions observed during the drying up of the shallow (2.4 m) Owens Lake, California (ca. 1969). Additional parameters were then added to simulate a deep (>10 m), perennial lake with the same chemical composition (e.g., ancient Searles Lake). Variations in temperature drive saline mineral precipitation and syndepositional alteration in both models, but in different ways. In shallow, well-mixed temperate lakes, minerals crystallize and transform in rhythm with seasonal temperature fluctuations. In deeper stratified lakes, alteration occurs when salts settle from surface waters (variable seasonal temperatures) to the bottom waters (constant temperatures). The deep lake model shows that more than half of the salts that precipitate at low temperatures later dissolve or back-react in warmer bottom waters. Closed basin evaporite deposits formed in temperate lakes thus preferentially preserve high temperature salts. This means that midlatitude lacustrine evaporites contain more climatic and limnological information than previously recognized, and can be interpreted in terms of seasonal temperatures, mean annual temperatures, and lake depths.

Hydrogen and Corrosion Resistance of Nickel Superalloys for Gas Turbines, Engines Cooled Blades

The paper presents the results of the analysis of the resistance to hydrogen and high-temperature salt corrosion of the developed alloy of the CM88Y type for the turbine blades of gas turbine engines for marine and power purposes in comparison with the industrial heat-resistant corrosion-resistant alloy CM88Y and the alloy for the protective coating of the SDP3-A blades. SDP3-A alloy was chosen as a reference sample, which has high hydrogen and corrosion resistance. The new heat-resistant alloy additionally contains such refractory metals as rhenium and tantalum, which are added to the composition of the alloy in order to increase operational characteristics while maintaining phase-structural stability. These are properties such as long-term and fatigue strength, characteristics of plasticity and strength at room and elevated temperatures. Therefore, the purpose of these studies was to determine the resistance to high-temperature salt corrosion of the developed alloy in comparison with the industrial heat-resistant nickel alloy and to evaluate the influence of alloying, hydrogen embrittlement of CM88Y and ZhS3DK alloys with different contents of chromium, boron, zirconium, hafnium, and yttrium were compared. The corrosion resistance of the materials was evaluated after crucible tests in a salt solution at a temperature of 900 °C for 30 h, according to the standard method. The corrosion resistances of alloys were determined by the mass loss, corrosion rate, and data from metallographic studies.

Optimization of the Plugging Agent Dosage for High Temperature Salt Profile Control in Heavy Oil Reservoirs

After steam discharge in heavy oil reservoirs, the distribution of temperature, pressure, and permeability in different wells becomes irregular. Flow channels can easily be produced, which affect the sweep efficiency of the oil displacement. Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs, improve the suction profile, and increase oil production. In the present study, the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes. Together with the connectivity model, a water flooding simulation model is introduced. Moreover, a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage, which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.

Consistent thermodynamic modeling of H2O–HCl–KOH–KCl between 200 K and 1,000 K

Over the last few decades, thermochemical databases for aqueous solutions and for high-temperature salt solutions have been developed separately from each other. This is largely due to the fact that the models used for the liquid phases are inconsistent. However, there is interest in highly concentrated aqueous solutions, as well as in the hydrolysis of salt melts, closing the gap between the two communities. Here, the liquid phase was consistently modeled, covering the complete composition space between H2O, HCl, KOH, and KCl at temperatures between 200 K and 1,000 K. Thermodynamic modeling of phase equilibria in the KCl–K2O–HCl–H2O reciprocal system was carried out using an associate solution model for the liquid phase, spanning from water to pure liquid acid and base, and liquid salt. Using the Calphad technique, the H2O–KCl, H2O–HCl, H2O–K2O, and KOH–KCl binary systems were critically assessed. While the model does not cover classical aqueous thermochemical properties (pH and osmotic coefficient), an excellent representation of phase diagrams and heat of reactions was achieved.

An experimental study on the mechanical performance of BFRP-Al adhesive joints subjected to salt solutions at elevated temperature

In order to study the mechanical properties of basalt fiber reinforced resin polymers–aluminum alloy (BFRP-Al) single lap joints (SLJ) under different humid and hot conditions. 80 °C/deionized water (DI-water), 80 °C/3.5%NaCl solution and 80 °C/5%NaCl solution were used as the aging conditions of BFRP-Al joints. Through the hygroscopic experiment, the maximum water absorption rate of dumbbell-shaped adhesive in the three environments was 7.15%, 4.12% and 4.96%, respectively. The maximum water absorption of basalt fiber reinforced resin polymers (BFRP) in the three environments was 2.24%, 1.2% and 1.55%, respectively. It is concluded that salt solution inhibits the absorption of water by adhesive and BFRP. The quasi-static tensile test of the joint was carried out. And the result shows that the failure strength of the joint in the three environments increases at first and then decreases with the prolongation of aging time. And the failure strength of the joint in the high-temperature salt solution is better than that in high-temperature DI-water. DSC experiments show that changes in glass transition temperature (T g) reflect changes in failure strength. SEM image analysis of the joint failure mechanism can show that the resin matrix damage in BFRP increases with aging time. The mechanical properties of the joint at the later stage of aging depend on the performance of BFRP.

EXPERIMENTAL INVESTIGATION of DOUBLE AGING HEAT TREATMENT of INCONEL 718 MONOBLOCK GAS TURBINE DISC IN A SALT BATH

The heat treatment of Inconel 718 (In718) monoblock gas turbine discs are mainly done by vacuum furnaces. Despite the vacuum furnaces allow to make a clean and reliable heat treatment, its operation costs affects the final product’s cost. In this work, as an alternative to the vacuum furnaces, the double aging heat treatment of In718 disc in a salt bath was investigated. The appropriate temperature for high and low temperature salt bath was identified in order to achieve necessary cooling rates of 125°C/min and 120°C/min for a 400 kg workpiece. It is shown that the heat treatment could be done when the high and low temperature salt baths temperatures are equal to 300°C. It is also found that the heat transfer coefficient for simulation could be taken as 650 W/m2.K regardless to the salt bath temperature.

Material Selection and Corrosion Studies of Candidate Bearing Materials for Use in Molten Chloride Salt

Abstract Molten chloride salts are being given strong consideration for use in heat transfer and storage in concentrating solar power (CSP) systems as well as in some nuclear reactor applications. Containment of the molten salt, particularly at the highest temperatures, is a major material concern and has received considerable study. Another material issue is the pumps that will be required to move the molten salt along with the bearing materials that will be required to have sufficient corrosion resistance as well as wear resistance in the high temperature salt. A pair of coordinated studies in our laboratory has addressed the corrosion, and the wear issues of candidate bearing materials including the selection of candidate materials as well as their performance in a molten sodium chloride-potassium chloride-magnesium chloride salt environment. This article addresses the selection of candidate materials and their chemical compatibility with the molten salt. The studies have identified material pairs that have suitable properties for use as bearings that would be immersed in molten chloride salt.

Effect of marine environment on the mechanical properties degradation and long-term creep failure of CFRP

The carbon fiber reinforced plastics (CFRP) has broad application prospect in the marine field, but its significate long-term performance and failure mechanism are still unclear. In this paper, the mechanical property degradation and creep failure mechanism of CFRP in marine environment were investigated by the molecular dynamics (MD) method. Based on the CFRP molecular model established in dry, pure water and salt immersion environment, the effect of service conditions on it in marine environment was explored. The results show that the marine environment can lead to a significant decrease in the mechanical properties of CFRP only in the vertical fiber direction, and the degradation extent increases with the increase of temperature. The effects of pure water immersion and salt immersion environment on its mechanical properties are basically the same. High stress level, hygrothermal environment and high temperature salt immersion environment will accelerate the creep failure of CFRP. Later, the creep failure mechanism of CFRP is analyzed from microstructure and microscopic energy. Microstructure analysis shows that water molecules could accelerate the movement of epoxy fragments and lead to CFRP failure. Microscopic energy analysis shows that the conversion process of strain energy and the decline of interface performance are the important reasons for creep failure. The finds of this paper introduce a new method to study the long-term performance of CFRP and can provide reference for the engineering application of CFRP in marine environment.

Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn): High Chemical Flexibility Resulting in Good Nonlinear-Optical Properties.

Seven acentric sulfides Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) were grown by a high-temperature salt flux method. The crystal structures of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds were determined by single-crystal X-ray diffraction with the aid of solid-state NMR spectroscopy. The Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds are isostructural and crystallize in the Ba6Ag4Sn4S16 structure type. The Sn-containing compound exhibits high structural similarity to Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) with the presence of an interstitial atomic position partially occupied by Sn atoms. The chemical bonding characteristics of Ba6(Cu2.9Sn0.4)Sn4S16 were understood with electron localization function calculations coupled with crystal orbital Hamilton population calculations. The Ba-S and Cu-S interactions are dominantly ionic, but the Sn-S interactions consist of strong covalent bonding characteristics in Ba6(Cu2.9Sn0.4)Sn4S16. The monovalent Cu atoms, mixed with certain metals with various oxidation states, significantly shift the optical properties of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi) compounds. This results in a good balance between the second-harmonic-generation (SHG) response and laser damage threshold (LDT). Ba6(Cu1.9Zn1.1)Sn4S16 possesses a high SHG response and a high LDT of 2.8 × AGS and 3 × AGS, respectively. A density functional theory calculation revealed that CuS4 and SnS4 tetrahedra significantly contribute to the SHG response in Ba6(Cu2Mg)Sn4S16, which also confirmed that CuS4 tetrahedra are crucial for the stability and optical properties of the Ba6(CuxZy)Sn4S16 (Z = Mg, Mn, Zn, Cd, In, Bi, Sn) compounds revealed by electronic structure analysis.

Effect of High Temperature Salt Immersion Environment on the Mechanical Properties Degradation and Long-Term Creep Failure of Carbon Fiber Reinforced Polymer

Effect of High Temperature Salt Immersion Environment on the Mechanical Properties Degradation and Long-Term Creep Failure of Carbon Fiber Reinforced Polymer

Tensile Behavior of Incoloy-800HT Exposed to High-Temperature Molten FLiNaK Salt and Thermal Aging

Tensile Behavior of Incoloy-800HT Exposed to High-Temperature Molten FLiNaK Salt and Thermal Aging

Chromium can cluster in molten salts

Highly dilute metal ions can aggregate in a high-temperature ionic-liquid medium and form long-lived clusters. The unexpected finding, which is the result of a study that combines experiment and modeling, sheds light on the early stages of corrosion in molten salt reactors (MSRs). MSRs are a next-generation, high-efficiency nuclear power plant technology in which nuclear fuel contained in a high-temperature salt circulates through the reactor in the liquid state. By running roughly 500 °C higher than today’s solid-fuel commercial reactors, MSRs promise to boost thermodynamic efficiency. More than 50 years after researchers began studying MSRs, however, the technology remains under development. One reason is that molten salts can corrode reactor vessels, slowly leaching chromium from alloys that otherwise perform well. To probe the corrosion process at the atomic level, Alexander S. Ivanov of Oak Ridge National Laboratory and coworkers used X-ray scattering and theoretical simulations to study the behavior of

Silicon as high-temperature phase change medium for latent heat storage: A thermo-hydraulic study

Latent heat storage (LHS) using high-temperature phase change medium (PCM) can provide cost-competitive solutions for dispatchable solar power and accumulate surplus Photo-voltaic (PV) and wind power. Moreover, at a sufficiently high temperature, the round trip efficiency of LHS system may approach that of electrochemical storage system. A conceptual LHS system utilizing high-temperature silicon as the phase change medium (PCM) is presented in the article. Silicon is chosen due to its high melting point (1414 °C), latent heat (1.8 × 106 J/kg), and thermal conductivity (25–50 W/mK). The thermo-hydraulic behavior during melting of silicon is modeled using a combined numerical methodology in COMSOL Multiphysics. The thermal performance of proposed system is compared against high-temperature salt-based system for different aspect ratios (AR). Results indicate that silicon systems are significantly superior to high-temperature salts under the same operating conditions. The anomalous behavior of silicon melting is established by demonstrating natural convection pattern in molten silicon. A generalized correlation is developed to predict the melting fraction as a function of Rayleigh number, Stefan number, and Fourier number for various domain sizes.

Rapid homogeneous precipitation of nano-sized Si in Al–1%Si alloy by electric pulses

Rapid and homogeneous precipitation of nano-sized Si particles with high density was achieved in Al–1%Si alloy by electric pulses treatment (EPT) in a liquid nitrogen bath (∼77 K). In contrast, when processed by EPT in air or by high-temperature (527–720 K) salt bath treatment, the precipitate density decreases dramatically. The homogeneous precipitation of Si could be facilitated by both the low-temperature environment and the non-thermal effects of EPT. The low-temperature environment provides a high driving force for nucleation, and retains the quenched-in vacancies serving as potential nucleation sites. The non-thermal effects of EPT can significantly promote local migration of solutes and vacancies at such low temperatures.

A Study of Solid-Free Drilling Fluid for Tight Gas Reservoirs

This project is explaining a laboratory development of a solid free drilling fluid formula that could be potentially used in tight gas reservoirs. The configuration of the weak gel fluid WGL-1, which is resistant to high temperature and high salt, was tested, and concluded that its gelling properties, salt and temperature resistance, and environmental protection were all in line with industry requirements. The final drilling fluid formula was developed as: water + (0.3% - 0.5%) NaOH + 5% KCl + 2% WGL-1 + 5% NaCl + (1.0% - 2.0%) HBFR Anti-high temperature fluid loss agent + 2% Polyol + (1.5% - 2.0%) SDL-1 Lubricant + 0.4% A4O1. The performance of the liquid was tested for temperature resistance, inhibition, gas formation protection effect, plugging performance, and static settlement stability. It was concluded that the temperature resistance performance is satisfied at 150°C, and the cuttings recovery rate is as high as 96.78%. It has good performance in inhibiting water dispersion and swelling of cuttings. The permeability recovery value reaches 88.9%, which meets the requirements of gas formation protection. The SSSI value shows that its settlement stability is good; under high temperature and high pressure, its sealing performance is good. This drilling fluid system has achieved the expected results and laid a foundation for further promoting the development of solid-free drilling fluid systems. The future development direction of solid-free drilling fluids is pointed out, to the improvement of properties to be applied in high temperature environment and have high salt resistance capacity.

Fluid flow diversion in abnormally high temperature and high salt reservoirs to enhance oil recovery technology

Fluid flow diversion in abnormally high temperature and high salt reservoirs to enhance oil recovery technology