The blending of hydrogen and natural gas (H2-NG) has emerged as a crucial and cost-effective means for processing hydrogen fluids through natural gas networks thereby aiding transition to net-zero ...energy. Nonetheless, the effective adaptation of H2-NG mixtures, especially up to 20% hydrogen concentrations, to existing natural gas distribution and storage facilities relies heavily on a comprehensive understanding of their thermophysical properties. We measured densities of three binary mixtures of hydrogen and methane (xH2 = 0.0532, 0.0858, and 0.2031) at temperatures between 278 and 398 K, and pressures up to 56 MPa using a vibrating tube densimeter (VTD). The VTD was calibrated using H2 and H2O. The measured densities were in reasonable agreements with the predictions of two thermodynamic equations of states (EoSs), Multi-Fluid Helmholtz Energy Approximation (MFHEA) and Peng-Robinson (PR). The average absolute relative deviation (AARD) for the measured density against the predictions of the PR EoS are 1.07%, 1.09%, and 0.89% for xH2 = 0.0532, 0.0858, and 0.2031 mol fractions respectively. While the AARD for the measured density against the predictions of MFHEA EoS are 0.16%, 0.16%, and 0.32% for xH2 = 0.0532, 0.0858, and 0.2031 mol fractions respective. The MFHEA EoS, which has the structure of GERG-2008, has better agreements with our density data than the PR EoS. The relative high deviations with PR EoS results from the PR's simple structure making it deficient in calculating thermal properties of natural gas in saturated-liquid and homogeneous states. In addition, the uncertainty of the measured density was determined, and the experimental data were compared with available literature data. Finally, the compressibility factor (Z), speed of sound (w), specific heat capacity at constant volume (CV), and specific heat capacity at constant pressure (Cp) were obtained from the experimental results and were compared with the predictions of MFHEA EoS. This work provides accurate density and other thermophysical data useful for engineering/process designs and modelling of H2 and natural gas systems thereby enhancing energy transition strategy.
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•Density measurements for H2 + CH4 (xH2 = 0.0532, 0.0858, and 0.2031) binary mixtures between 278 and 397 K and up to 56 MPa using VTD.•The measured densities were compared with the predictions of MFHEA and PR EoSs.•Determination of compressibility factors and other derived properties such w, CV, and CP for the mixtures.
The brownmillerite phase Ca2Fe2O5 was processed by the reactive firing of calcite and a natural siderite for prospective catalytic applications. Thermogravimetry and X-ray diffraction (XRD) was used ...to monitor the decomposition of precursors and its dependence on heating rate and atmosphere. Taguchi planning was used to assess the impact of firing temperature, time, and rate of heating on the conversion of precursors reflected by I121sp:I121b peak intensity ratio of main XRD reflections of secondary spinel phase CaFe2O4 and brownmillerite. The onset of additional minor phases (Ca2Al2SiO7 and Ca2SiO4) was ascribed to the reaction of a fraction of calcia with gangue components of the siderite precursor. Thermodynamic modelling was used as a guideline for synthesis in non-oxidising conditions to hinder the onset of CaFe2O4. These guidelines allowed one to obtain high conversion to Ca2Fe2O5 with enhanced crystallinity at 700 °C, in an inert Ar atmosphere. Faster reactivity at T ≥ 800 °C in this oxygen-lean atmosphere, leads to highly crystalline Ca2Fe2O5 coexisting with the onset of wustite and/or metallic Fe, which account for the oxygen balance, and calcium silicates, by reaction of calcia with silica.
Thermodynamic modelling can reliably predict hydrated cement phase assemblages and chemical compositions, including their interactions with prevailing service environments, provided an accurate and ...complete thermodynamic database is used. Here, we summarise the Cemdata18 database, which has been developed specifically for hydrated Portland, calcium aluminate, calcium sulfoaluminate and blended cements, as well as for alkali-activated materials. It is available in GEMS and PHREEQC computer program formats, and includes thermodynamic properties determined from various experimental data published in recent years. Cemdata18 contains thermodynamic data for common cement hydrates such as C-S-H, AFm and AFt phases, hydrogarnet, hydrotalcite, zeolites, and M-S-H that are valid over temperatures ranging from 0 to at least 100 °C. Solid solution models for AFm, AFt, C-S-H, and M-S-H are also included in the Cemdata18 database.
Experimental phase equilibrium data for the quaternary system containing carbon dioxide + chloroform + ω-pentadecalactone + poly(ω-pentadecalactone), in the mass ratio of 1:0.25:1, 1:0.5:1, 1:1:1, ...1:2:1 and 1:3:1 of carbon dioxide: chloroform: ω-pentadecalactone + poly(ω-pentadecalactone), simulating conversions up to 10.0 wt%, over the temperature range from 323.15 K to 353.15 K, in order to provide fundamental information to the polymerization reaction of ω-pentadecalactone in supercritical fluid medium. Phase transitions of vapor-liquid (bubble point type) were observed. Furthermore, an increase in chloroform content resulted in a decrease of phase transition pressures, revealing this component as an efficient co-solvent for overall system solubilization. For lower chloroform mass ratios (1:0.25:1 and 1:0.5:1), it was noticed that as the amount of polymer content increased, phase transition pressures were also enhanced. The experimental results were modeled using the PC-SAFT EoS, providing a reliable representation of the experimental phase equilibrium data.
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•Phase equilibrium data at several stages of ω-pentadecalactone polymerization reaction were measured.•Experiments were performed in the temperature range from 323.15 to 353.15 K and for different chloroform contents.•Phase transitions of vapor-liquid bubble point type were verified.•Experimental data modeling with PC-SAFT EoS.
Heavy metals (HMs) in concrete pose great environmental risks. However, mechanism-based quantification for cement paste's immobilization on HMs was seldom reported. Using a broad experimental design, ...we investigated the binding behaviors of representative HMs in C3S, C3A and C4AF pastes. Specifically, sorption and leaching tests were conducted to reveal the sorption roles of C-S-H, AFt and AFm. Afterwards, a thermodynamic model was established to quantify cement pastes' immobilization capacity and verified by progressive leaching. According to the results, the HMs are divided into three categories. In the 7-day cement pastes, precipitation-type HM Mn2+ can be completely immobilized as Mn hydroxides; amphoteric-type HM Pb2+ is partly immobilized as hydroxides and sorbed by C-S-H, AFt and AFm; and anion-type HM CrO42− has difficulty precipitating or being sorbed by hydrates (except AFm), while AsO43− can be completely immobilized. The quantification provides a basis for the environmental assessment of HM leaching from concrete.
•Pure-phase pastes and synthetic hydrates were used for the clarification.•Sorption and leaching tests were conducted to reveal the mechanisms in depth.•A mechanism-based thermodynamic model was developed for the quantification.
The significant inhabitation of Portland cement hydration by zinc restricts the utilization of zinc-bearing solid wastes in cementitious materials. The influence of zinc, in the form of ...(Zn(NO3)2·6H2O and ZnCl2, on the hydration of Portland cement and tricalcium silicate (C3S) was investigated both experimentally and by thermodynamic modelling. The reaction of C3S in zinc-rich solutions is strongly retarded and initially results in the formation of Zn(OH)2, Zn5(OH)8Cl2·H2O, CaZn2Si2O7·H2O, Zn2SiO4 and (ZnO)2x(SiO2)x·2xH2O, while the pH values remain low. At higher C3S reaction, Zn2+ concentrations decrease and the pH starts to rise as Ca2+ gradually accumulates in pore solution. Such retarding effect of zinc may be due to i) chemisorption of Zn2+ on the surface of C3S in particular at lower pH values and ii) the lowering of pH by addition of zinc salts.
•A new, open access, thermodynamic model for piperazine and blends was regressed.•The model uses an innovative manner to specify the piperazine zwitterion.•The model is validated against a wide range ...of experimental data.•This is the first thermodynamically consistent PZ and AMP/PZ model on Aspen Plus.
This study developed a comprehensive, open-access, thermodynamically consistent, validated vapour-liquid equilibrium model for CO2 absorption into aqueous solutions of piperazine (PZ) activated 2-amino-2-methyl-1-propanol (AMP) on Aspen Plus. This solves a two-decade-old problem of inconsistent specification of PZ, and lacking AMP/PZ, thermodynamic models on Aspen Plus, supporting robust process modelling of AMP/PZ-based CO2 capture systems, considered the contemporary benchmark. The model coverage is wide: total amine concentrations from 30 wt% to 50 wt%, AMP/PZ mole ratios from 0.46 to 23.1, CO2 loadings from 0.04 to 1.07 mol CO2/mol amine, and temperatures from 20 °C to 160 °C. The significance lies in the model’s innovative treatment of the zwitterion PZH+CO2–, leading to accurate VLE predictions and closed charge balances. Absolute average relative deviations (AARD) are 16.6 % to 22.3 % for CO2 partial pressure predictions and 6.3 % to 7.7 % for absorption heats. Gibbs-Helmholz and flash calculated absorption heats consistently compare within 1.5 % to 7.0 %, signalling the model’s thermodynamic consistency.
Metasomatism is a source of methane on Mars Rinaldi, Michele; Mikhail, Sami; Sverjensky, Dimitri A.
Earth and planetary science letters,
05/2024, Letnik:
634, Številka:
C
Journal Article
Recenzirano
Odprti dostop
•Methane is a major carbon species in fluids at the Martian crust-mantle boundary.•Fluid-rock interaction can induce abiotic methanogenesis in the Martian crust.•Ultramafic rocks are more efficient ...host rocks for methanogenesis than mafic rocks during fluid-rock metasomatism.
The abundance of inactive Martian volcanic centres suggests that early Mars was more volcanically active than today. On Earth, volcanic degassing releases climate-forcing gases such as H2O, SO2, and CO2 into the atmosphere. On Mars, the volcanic carbon is likely to be more methane-rich than on Earth because the interior is, and was, more reducing than the present-day Terrestrial upper mantle. The reports of reduced carbon associated with high-temperature minerals in Martian igneous meteorites back up this assertion. Here, we undertake irreversible reaction path models of the fluid-rock interaction to predict carbon speciation in magmatic fluids at the Martian crust-mantle boundary. We find methane is a major carbon species between 300 and 800 °C where logfO2 is set at the Fayalite = Magnetite + Quartz redox buffer reaction (FMQ). When logfO2 is below FMQ, methane is dominant across all temperatures investigated (300–800 °C). Moreover, ultramafic rocks produce more methane than mafic lithologies. The cooling of magmatic bodies leads to the release of a fluid phase, which serves as a medium within which methane is formed at high temperatures and transported. Metasomatic methane is, therefore, a source of reduced carbonaceous gases to the early Martian atmosphere and, fundamentally, for all telluric planets, moons, and exoplanets with Mars-like low logfO2 interiors.
Thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and thermodynamic modelling have been used to obtain Friedel's salt profiles for saturated mortar cylinders exposed to a 2.8 M NaCl ...solution. Comparison of the measured Friedel's salt profiles with the total chloride profiles indicates that only a minor part of the chloride ions is bound in Friedel's in the studied Portland cement (P) and limestone blended (L) cement. The chloride binding capacity with respect to the formation of Friedel's salt by consumption of monocarbonate is reached for the P and L mortars, where only a fraction of about 20% of the amount of C3A is found to contribute to formation of Friedel's salt. Higher amounts of Friedel's salt are formed in the metakaolin containing mortars. However, the limited chloride ingress depths prevent quantification of the potential full chloride binding capacity of Friedel's salt in these mortars. The measured amounts of Friedel's salt by TGA and the portlandite profiles show that the maximum amount of Friedel's salt is found in the region with limited leaching of calcium, which is in good agreement with the predicted Friedel's salt profiles.
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