Thermodynamic Equilibrium Calculations Research Articles

Effect of HTC and Water-Leaching of Low-Grade Biomasses on the Release Behavior of Inorganic Constituents in a Calcium Looping Gasification Process at 650 °C.

The release of alkali metals (K, Na) and nonmetals (S, Cl) during a calcium looping (CaL) gasification process of waste derived-hydrochars, water-leached samples, and CaO-biomass blends was investigated. Special attention was paid to biomasses that are not particularly promising for gasification requirements but have a large occurrence in Europe, including Grape Bagasse, Organic Fraction of Municipal Solid Waste (OFMSW), Green Waste, and Out-of-use woods from construction debris and discarded furniture. The release experiments were performed at 650 °C in a flow channel reactor to investigate the behavior of inorganic trace substances. Hot-gas analysis was performed by Molecular Beam Mass Spectrometry (MBMS). Thermodynamic equilibrium calculations via FactSage indicate H2S, carbonyl sulfide (COS), KCl, NaCl, and HCl as the main inorganic impurities. Thus, the focus of the experiments was placed on these species. It was found that the concentrations of trace elements released during gasification at 650 °C, such as H2S, SO2, KCl, and NaCl, are hardly affected by intense water-leaching. In contrast, carbonaceous materials from hydrothermal carbonization exhibit a higher concentration of trace potassium substances (K, KCl, and K2Cl+). When biomass samples are combined with CaO, the total amount of inorganic trace compounds (K, Na, and S compounds) in the resulting syngas could be decreased.

Low-NOx thermal plasma torches: A renewable heat source for the electrified process industry

Industrial thermal plasma torches can heat a gas up to 5000–20,000 K, i.e., well above the temperature needed to replace the heat generated from the combustion of traditional fossil fuels (e.g., coal, oil, and natural gas) in large-scale process industry furnaces producing construction materials (e.g., iron, steel, lime, and cement). However, there is a risk for significant NOx emissions when air or N2 are used as plasma-forming gas since the temperature somewhere in the furnace always will be higher compared to the threshold NOx formation temperature of ∼1800 K. Torch NOx forms inside the high temperature region of the plasma torch (>5000 K) when air is used as gas. Process NOx forms instead when the hot gas (when air or nitrogen is used as plasma forming gas) from the plasma torch mixes with process air downstream the torch. By analysing the complex chemistry of both the torch- and process NOx formation with thermodynamic equilibrium and one-dimensional chemical kinetic calculations it was shown that adding H2 to the plasma-forming N2 gas significantly reduces the NOx emissions with more than 90 %. Verifying experiments with air, pure N2, and mixtures of H2 and N2 as plasma-forming gas were performed in a laboratory scale insulated laboratory furnace with different pre-heating temperatures of process air (293, 673, and 1073 K) which the plasma gas mixes with downstream the torch. Depending on the pre-heating temperature the NOx emissions were between 12,000–14,000 mg NO2/MJfuel when air was used as plasma forming gas. Substantial NOx emission reduction occurs both when N2 replaces air, where the NOx emissions was in the span of 8000–11,500 mg NO2/MJfuel and furthermore when H2 was mixed into the N2 gas stream. For the highest degree of H2 mixing (28.6 vol-%), the NOx emissions were between 450–1700 mg NO2/MJfuel depending on the pre-heat temperature of the process air, i.e., a reduction of 88–96 % and 85–94 %, respectively when air or N2 was used as plasma forming gas. The measured NOx emissions are then of the same order of magnitude as would be expected from the combustion of traditional fuels (coal, oil, biomass and pure H2). Finally, by analysing the aerodynamics in an axisymmetric furnace with an experimentally validated computational fluid dynamics (CFD) model using reduced chemistry for the NOx formation (19 species and 70 reactions), further guidelines into the process of NOx reduction from thermal plasma torches are given.

Novel Strategy for Efficient Recovery of CuO-Based Multiple-Metals from Copper Smelter Dust toward CO2 Electrocatalytic Reduction.

Copper smelter dust, a typical hazardous waste that is abundant in valuable heavy metals, holds the potential to be regarded as a promising resource. This study introduces a new approach that integrates chlorination roasting and cascade condensation to efficiently recover heavy metals from copper smelter dust. The findings demonstrate the successful separation of heavy metals (Cu, Pb, and Zn) as chlorides at nearly 100% efficiency while also effectively converting trivalent arsenic (As(III)) into pentavalent arsenic (As(V)) and immobilizing it in the roasting residues, thereby reducing environmental risk. Through the utilization of thermogravimetric mass spectrum analysis and thermodynamic equilibrium calculations, the chlorination process for heavy metals was investigated, revealing both direct and indirect chlorination processes. Additionally, the study resulted in the development of a CuO-based multiple-metals electrocatalyst from the oxidized roasting-recovered heavy metal chlorides, exhibiting significantly enhanced catalytic activity and faradaic efficiency for the electroreduction of CO2 into CO and CH4 compared to pure CuO electrocatalyst under similar electrocatalytic conditions. Overall, this work presents a sustainable and scalable method and new insights for addressing environmental risks while repurposing copper smelter dust.

High-temperature corrosion mechanisms of a Ni-based alloy in simulated multi-source organic waste co-incineration environments

Due to the new trend of co-incinerating municipal solid waste (MSW) with sewage sludge, medical waste, or industrial organic waste to attain a “waste-free” status, mixing of multi-source organic wastes (MSOW) increases the complexity of solid waste, which fluctuates the composition of corrosive species in the boiler. The fluctuation of corrosive species alters the alkali metals/S/Cl ratios and increases the uncertainties of high-temperature corrosion of boiler key components. The corrosion behaviors and mechanisms in varying compositions of corrosive species are complex and remain elusive. To investigate the corrosion characteristics during the co-incineration of MSOW, this study examined the corrosion mechanisms of a nickel-based Ni59.08Cr24.31Al10.74W5.3B0.57 alloy in simulated co-incineration environments of MSOW. The environment contained either HCl, NaCl, or SO2 in wet oxygen at 600 °C. For each case experiment, the maximum possible value of each corrosive species expected in the actual incinerator and/or its absence was considered. HCl of either 0 or 1500 ppm, SO2 of 0 or 300 ppm, and NaCl of 0 or 50 mg/cm2 were systematically used in each experiment. The influence of each corrosive condition on the corrosion of the alloy was evaluated by mass gain measurements, and the corrosion mechanisms were elucidated through SEM, EDS mapping, XRD, XPS analyses, and thermodynamic equilibrium calculations. The results revealed that NaCl salt and HCl gas in wet oxygen have complementary effects, which accelerated the corrosion of alloy, reaching ∼ 65.6 mg/cm2 over one week. HCl enhanced the corrosion by affecting the chemical reactions that regenerated NaCl, which participated in prolonged corrosion processes. SO2 reduced the mass gain of the alloy to 38.4 mg/cm2. SO2 participated in the sulfation of NaCl, forming a mixed layer of Na2SO4 and (Al/Cr)2O3, reducing the mass gain by 1.71 times. In the environment without NaCl, SO2 helped in the formation of a protective oxide layer, which prevented HCl from reaching the alloy, reducing the corrosion impact by 23.5 times.

Comparative experimental study of ash formation behaviors during the fixed-bed gasification of coal water slurry and dry pulverized coal prepared from Shenmu coal

The mechanism of ash formation during coal gasification is very important for the safety and stability of gasifier operation. This study comparatively investigated the ash formation behaviors during the gasification of coal water slurry and dry pulverized coal. Shenmu coal was gasified in a CO2 atmosphere at 900 °C using a fixed-bed reactor to prepare chars and ashes. Computer-controlled scanning electron microscopy was employed to characterize the compositions and particle sizes of minerals in the raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash. Morphological characteristics reveal that, during gasification, coal water slurry gasification char exhibits obvious agglomeration compared to the dry pulverized coal gasification char. The changes of mineral compositions indicate that, during both coal water slurry and dry pulverized coal gasification, minerals follow nearly identical transformation pathways, but the degrees of transformation are different. The influence of char agglomeration on heat transfer may be the reason for the less transformation of K Al-silicate and kaolinite during the coal water slurry gasification. Furthermore, in comparison to dry pulverized coal gasification, more Ca in calcite and S in pyrite transfer into gypsum during the coal water slurry gasification. The results from thermodynamic equilibrium calculations indirectly suggest that this may be attributed to the limited internal diffusion of CO2 within coal water slurry gasification char resulting from char agglomeration during gasification. Overall particle size distributions of minerals in raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash demonstrate that the degrees of mineral fragmentation are almost consistent during both coal water slurry and dry pulverized coal gasification. However, differences in the degrees of mineral transformation led to different particle size distributions of various minerals between coal water slurry gasification ash and dry pulverized coal gasification ash. This study mainly focuses on the influence of water in coal water slurry on ash formation, and it has not considered the influence of other factors, such as ash content, hydrophilicity, caking property, and gasification reactivity of coal, which need further research to explore.

Study on the Pyrolysis and Incineration of Lewisite by Thermodynamic Equilibrium Calculation

AbstractLewisite is a representative chemical warfare agent that contains arsenic. Thermal decomposition is an essential method for Lewisite destruction, and appropriate destruction conditions can enhance the environmental friendliness of this method by minimizing the hazards of destruction products. In this study, the variation of Lewisite during pyrolysis and incineration was calculated, with particular emphasis on the evolution behaviors of arsenic and chloride with temperature, pressure, and molar ratio. The main products identified during pyrolysis were HCl(g), C, As, and AsCl3(g). Under anoxic conditions, AsCl3(g) and As were the dominant species. In oxygen‐enriched conditions, arsenic existed primarily as AsCl3(g), As2O5, As2O4, and AsOCl. Below 600 °C, arsenic predominantly existed in high valence forms such as As2O5. Above 600 °C, the binding capacity of chlorine and arsenic was stronger than that of oxygen, resulting in an AsCl3(g) molar fraction exceeding 75 % at 1200 °C. The primary chlorides in oxygen‐enriched conditions were Cl2(g), HCl(g), AsCl3(g), and Cl(g). Lower incineration temperatures (around 500 °C), sufficient oxygen conditions (molar ratio above 4 : 1), and positive pressures were conducive to reducing the toxicity of destruction products. The results are in good agreement with the experimental data.

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Thermodynamic study on the separation of strontium and barium from LWR spent fuel

The separation of high heat load fission products, such as alkaline earth metals, from nuclear spent fuel can significantly reduce the burden of spent fuel disposal. This study investigates the feasibility of separating strontium and barium from light water reactor spent fuel through non-aqueous processes. Process flows were developed for treating spent nuclear fuel by heating it at high temperatures to remove volatile nuclides, followed by chlorination with a chlorinating agent. The chlorinated products were then treated with a precipitating agent in LiCl-KCl molten salt for further separation. The remaining liquid was distilled to recover strontium and barium. Thermodynamic equilibrium calculations were conducted for the process flows. Under the conditions of the process flows, the chlorinating agents MgCl2 and NH4Cl both converted SrO and BaO entirely into SrCl2 and BaCl2, respectively. The precipitating agent Li2CO3 exhibited superior separation effectiveness compared to Li3PO4. Thermodynamic calculations indicate that strontium and barium recovered by MgCl2 chlorination, Li2CO3 precipitation, and distillation will contain 0.18 %, 1.06 %, and 0.32 % impurities in terms of mass, radioactivity, and decay heat, respectively.

Modes of Occurrence, Migration, and Evolution Pathways of Lithium and Gallium during Combustion of an Al-Rich Coal, Inner Mongolia, China

The modes of occurrence, migration, and evolution pathways of lithium (Li) and gallium (Ga) during combustion of an Al-rich coal from Inner Mongolia, China, were investigated using methods of simulated combustion experiments, the sequential chemical extraction procedure (SCEP), and the thermodynamic equilibrium calculation. Mineralogical and chemical compositions of the feed coal and combustion ash were analyzed by X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and scanning electron microscopy (SEM). The study reveals that Li and Ga are significantly enriched in the ash after combustion, with the contents reaching up to 1086 μg/g and 133 μg/g, respectively. The primary modes of occurrence of Li and Ga in the ash are quartz and aluminosilicates, and sulfides, respectively. Li, in the form of LiAlSi4O10 (s), primarily occurs in hematite, glass, and quartz below 800 °C. However, it migrates into the glass phase, mullite, and quartz above 1000 °C. On the other hand, Ga exists as Ga4S5 (s) and transforms into Ga2S (g) as the temperature rises from 800 °C to 1000 °C, maintaining this gaseous form until 1200 °C. Ga4S5 (s) predominantly occurs in the glass phase at 600 °C, whereas mullite and quartz become its dominant modes of occurrence in industrial combustion ashes and ashes obtained from simulated combustion above 600 °C.

Co-pyrolysis of municipal sludge and papermaking sludge: Pyrolysis behaviors and heavy metals immobilizations

The co-pyrolysis of municipal sludge (MS) and papermaking sludge (PS) is beneficial for improving the quality of co-pyrolysis biochar and the stability of heavy metals in it. This study investigated the synergistic effect of co-pyrolysis of MS and PS, as well as the influence of different mass ratios (1:9, 3:7, 5:5, 7:3, and 9:1; MS:PS) and pyrolysis temperatures (400–600 ℃) on the physicochemical properties of pyrolysis char, chemical speciation of heavy metals, and their potential ecological risk index. Furthermore, thermodynamic equilibrium calculations were used to study the transformation and stabilization mechanisms of heavy metals during co-pyrolysis. The results indicated that the addition of PS increased the comprehensive pyrolysis index of MS (by 2.09–16.72 times) and the specific surface area of co-pyrolysis char. The inclusion of MS effectively promoted the transformation of heavy metals from unstable fractions to stable fraction, significantly reducing the potential ecological risk index of pyrolysis biochar (by 21.93–41.58 %). The combination of thermodynamic equilibrium calculations and experimental data demonstrated that heavy metals in sludge could be stabilized through the formation of stable heavy metal compounds or their encapsulation within the lattice of inorganic components during co-pyrolysis. These findings suggest that co-pyrolysis of MS and PS is a feasible and promising approach for producing high-quality pyrolysis char with low risk of heavy metals.

Characterization of Limestone Surface Impurities and Resulting Quicklime Quality

Quicklime, rich in CaO(s), is generated by calcining limestone at high temperatures. Parallel-flow regenerative lime kilns are the most energy-effective industrial method available today. To prevent major disruptions in such kilns, a high raw material quality is necessary. Under some conditions, impurity-enriched material may adhere to limestone pebbles and enter the kiln. In this study, limestone and corresponding quicklime were analyzed to evaluate the extent and composition of surface impurities and assess the effect on quicklime product quality, here defined as free CaO. This was performed by sampling and analyzing limestone, quarry clay, laboratory-produced quicklime, and industrially produced quicklime with XRF, SEM/EDX, and XRD; interpretations were supported by thermodynamic equilibrium calculations. In the laboratory-produced quicklime, the surface impurities reacted with calcium forming Larnite, Gehlenite, Åkermanite and Merwinite, reducing the quicklime quality. The results showed that the limestone surface layer comprised 1.2 wt.-% of the total mass but possessed 4 wt.-% of the total impurities. The effect on industrially produced quicklime quality was lower; this indicated that the limestone surface impurities were removed while the material moved through the kiln. Multicomponent chemical equilibrium calculations showed that the quarry clay was expected to be fully melted at 1170 °C, possibly leading to operational problems.

Core–Shell catalyst particles for tandem catalysis: An experimental/numerical approach towards optimal design

Tandem catalysis is a promising approach to intensify chemical processes and increase their efficiency. On the other hand, the design of efficient, optimal and targeted tailored tandem catalysts is yet so challenging as the optimal catalyst loading is difficult to assess a priori. In this article, we present a concise route towards the design of optimal core–shell tandem catalyst particles on the example of coupled RWGS and FTS reactions for any specific spherical morphology. The route features five consecutive steps including: tandem system identification, catalyst synthesis, i.e. mono- and tandem-functional, catalyst characterization and initial performance test, kinetic modeling with parameter estimation if necessary, and optimal design of catalysts. The initial step features thermodynamic equilibrium calculations for RWGS and FTS showing a common operational window. Then, Pt and Co are selected as active metals and the formulation of the tandem catalyst is designed. For the second step, the synthesis route for the tandem catalyst Pt,CeO2@SiO2-Co, and the mono-functional catalysts, Pt@SiO2 and CeO2@SiO2-Co are presented. For the third step, all catalysts were tested for CO2 hydrogenation as an exemplary tandem process. A reduced transport model from literature was adjusted for RWGS and FTS reactions with kinetic expression from literature to enable numerical optimization. The kinetic parameters are estimated based on the performance tests of the mono-functional reference materials, i.e. Pt@SiO2 for RWGS and CeO2@SiO2-Co for FTS. The model is validated by cross comparison to the data from the tandem reaction setup. In the fifth step, the model was used for the numerical optimization of the catalyst loading on core and shell leading to the identification of the optimal design, resulting in a significant increase of C2+ Yield.

MaterialsMap: A CALPHAD-based tool to design composition pathways through feasibility map for desired dissimilar materials, demonstrated with resistance spot welding joining of Ag-Al-Cu

Assembly of dissimilar metals can be achieved by different methods, for example, casting, welding, and additive manufacturing (AM). However, undesired phases formed in liquid-phase assembling processes due to solute segregation during solidification diminish mechanical and other properties of the processed parts. In the present work, an open-source software named MaterialsMap, has been developed based on the CALculation of Phase Diagrams (CALPHAD) approach. The primary objective of MaterialsMap is to facilitate the design of an optimal composition pathway for assembling dissimilar alloys with liquid-phases based on the formation of desired and undesired phases along the pathway. In MaterialsMap, equilibrium thermodynamic calculations are used to predict equilibrium phases formed at slow cooling rate, while Scheil-Gulliver simulations are employed to predict non-equilibrium phases formed during rapid cooling. By combining these two simulations, MaterialsMap offers a thorough guide for understanding phase formation in various manufacturing processes, assisting users in making informed decisions during material selection and production. As a demonstration of this approach, a compositional pathway was designed from pure Al to pure Cu through Ag using MaterialsMap. The design was experimentally verified using resistance spot welding (RSW).

Steam-assisted MILD-POX: A flexible process for the production of hydrogen

The aim of the present work is to propose an alternative hydrogen production process using water and sustainable feedstocks to promote the utilisation of cheap and renewable raw materials on a large scale by increasing flexibility, efficiency, and eco-compatibility of existing technologies without sacrificing their reliability and affordability. The idea is to combine non-catalytic Partial Oxidation and Moderate or Intense Low-oxygen Dilution combustion technologies by adding water. Thermodynamic equilibrium calculations, accompanied by kinetic modelling, are used to assess and interpret the general behaviour of a potential unit that uses the interaction of these two technologies and to compare the performances over a range of operating conditions of interest. The results show that thermochemical production of H2 using the proposed process is theoretically feasible and has the potential to offer many advantages over standard processes. The immediate advantage of such an approach is that a very high H2/CO ratio can be obtained that could eliminate the water gas shift conversion stages, making the reactor more compact and simple than conventional reformers. Moreover, water vapour addition limits the formation of soot precursors due to a “leaning” effect from releasing hydroxyl radicals.

Does Direct Dimethyl Ether Synthesis from Carbon Dioxide and Hydrogen Yield More Valuable Products than the Equivalent Methanol Production? A Review on Recent Work

AbstractDimethyl ether (DME) has promising properties as e‐fuel and platform chemical. Its direct synthesis from CO2 and hydrogen, which is thermodynamically more favorable than the indirect route over methanol, is reviewed. Systematic thermodynamic equilibrium calculations are evaluated and compared to bifunctional catalysis experiments performed with Cu/ZnO/ZrO2 methanol catalyst and ferrierite or heteropolyacid‐coated dehydration catalysts under thermodynamic and kinetic conditions. In the thermodynamic region, the methyl yield of direct DME synthesis is superior over sole methanol synthesis. Significant differences among the solid acids used are absent. However, under kinetic conditions, the heteropolyacid‐coated catalysts show superior performance for dehydration over zeolites.

Broadening of the carbon window and the appearance of core-rim carbides in WC-Fe/Ni cemented carbides

Among several separate challenges, the major one for replacing cobalt in cemented carbides is the difficulty to obtain alternative binder materials with a C-window broad enough to be robustly processed under conventional industrial control on the C content. The C-window is defined as the C content range for which phases that are detrimental to the mechanical properties are avoided. The present paper has two main objectives: first, to show that the processing C-window of Fe-Ni based systems is in fact wider than what thermodynamic equilibrium calculations predict, and that its width can be controlled moderately by tweaking the initial WC grain size and the cooling rate used in the material’s processing. Secondly, in case those detrimental phases are not avoided, this work gives insight on how to make their appearance less detrimental for the mechanical properties. The morphology, volume fraction and particle size distribution of the detrimental phases, specifically η6-carbides at low C contents, are investigated to explore desirable combination of hardness and toughness of alternative binder cemented carbides. During this study it was also discovered that in samples with carbon contents below the low-C limit of the C window a carbide with hexagonal lattice known as κ, not commonly seen in cemented carbides, appeared and formed the core of a core-rim structure together with the more common η6-phase. It is believed that the κ-carbide form due to local high concentrations of tungsten during solid state sintering and that it has an impact on the precipitation characteristics of the η6-phase.

Effects of Fluorides on NaF Vaporization during Mold Powder Melting by Thermodynamic Equilibrium Calculation

Effects of Fluorides on NaF Vaporization during Mold Powder Melting by Thermodynamic Equilibrium Calculation

Component-based equilibrium modeling of biomass fixed-bed gasifier

In this paper, the process of gasification of rice husk directly with air in a fixed-bed gasifier was modeled using Aspen Plus. Unlike traditional models based on the elemental balance method, this study modeled the decomposition of rice husk into cellulose, lignin, and hemicellulose based on experimental data from the pyrolysis equipment, and the product yields were fitted to obtain the distribution of product yields in the pyrolysis stage of rice husk. In the redox stage, the thermodynamic equilibrium calculation model and the kinetic calculation model were used for the simulation, respectively, and compared and analyzed with the actual plant operation data. In the simulation of the thermodynamic equilibrium calculation model, the error of gas yield was about 5%. While in the kinetic calculation model, the errors of gas production rates of N2, H2 and CH4 were within 5%, the errors of CO and CO2 were larger, which were 13.73% and 17.09%, respectively. The error of the yield of Bio-char, an additional product of gasification, is about 2% in both models, which is close to the actual working conditions. Based on the model, the effects of gasification temperature, air equivalent ratio (ER) and air preheating temperature on the gasification reaction were discussed in this paper. The results concluded that the gasification temperature should be maintained at about 800 °C, the air equivalent ratio at about 0.3, and the air preheating temperature should be increased appropriately when performing rice husk gasification.

High-temperature corrosion-resistant alloy for waste-to-energy plants: Alloy designing, fabrication, and possible corrosion-resistance mechanism

This study designed a novel high-temperature corrosion-resistant alloy through thermodynamic equilibrium computations. The strength was determined by the integration of precipitation-strengthening species of nickel boride and tungsten solid solution strengthening, while high-temperature corrosion-resistant property was realized through optimized compositional design. Phase stability was enabled by the presence of a face-centered cubic structure. The alloy was fabricated and its corrosion-resistance performance was experimentally compared with other commercially available nickel- and iron-based alloys under simulated municipal solid waste combustion. The designed alloy with a composition of Ni-5B-6W-28Cr-13Al showed a low corrosion rate of ∼72 % < 13CrMo4-5TS and 1.08 % > Inconel 625. Economic analysis showed that Ni-5B-6W-28Cr-13Al has a cost-effectiveness ratio of 1:1.57 with respect to Inconel 625 and 1:0.09 with respect to 13CrMo4-5TS. Corrosion-resistance mechanism was explored using scanning electron microscopy coupled with energy dispersive spectroscopy, x-ray diffractometer, and DFT computations. The corrosion resistance occurred through the formation of a uniform tungsten-chromium-oxide film which inhibits inward diffusion of corrosive chlorine species. These findings provide insights into the development of alloys for high-temperature technologies.

Challenges in determining individual chemical potentials of system elements by Gibbs energy minimization

Accounting for the elusive gas phase in thermodynamic equilibrium calculations is demonstrated to be important for achieving accurate and unique determination of constituent element chemical potentials, when Gibbs energy minimization (GEM) encounter indeterminacy due to rank deficiency in mass-balance equations. The molar GEM of the equilibrium vapor phase offers a robust solution for unambiguously and accurately determining element chemical potentials. To enable this, a novel optimization method for mass-balance equation is presented, paving the way for reliable thermodynamic calculations.