H2O CO2 Research Articles

Pyrolysis and Volatile Evolution Behaviors of Cold-Rolling Oily Sludge

Cold-rolling oily sludge contains high amounts of oil and iron resources that can be recycled by pyrolysis. We investigated the pyrolysis behavior and volatile products of oily sludge by thermogravimetric analysis (TG) coupled with Fourier transform infrared spectroscopy (FTIR) and a pyrolyzer (PY) coupled with gas chromatography/mass spectrometry (GC/MS). The pyrolysis process was divided into three stages: H2O drying and CO2 desorption at low temperatures (below 393 K); the volatilization of low-molecular-weight organics and the covalent bond cleavage of C=C, C-O, and C-H in the medium-molecular-weight organics at medium temperatures (393–844 K); and chain scission of the high-molecular-weight organics and reduction of iron oxides by CO at high temperatures (above 844 K). The weight losses of oily sludge in the three stages were 0.4 wt %, 47.9 wt %, and 14.7 wt %, respectively. According to the kinetic models, stage 2 and stage 3 could be described with the second-order and third-order reaction models, and their activation energies were 40.22 kJ/mol and 214.99 kJ/mol, respectively. The compounds in the volatile products were identified by FTIR and GC/MS. The organics in the volatile products from stage 2 pyrolysis mainly consisted of aliphatic hydrocarbons, fatty acids, esters, ketones, and nitrogen compounds, while the volatile products from stage 3 predominantly contained aliphatic hydrocarbons, mononuclear aromatic hydrocarbons, and small amounts of nitrogen compounds and CO, suggesting the occurrence of chain scission of heavy organics.

MafiCH: a general model for H2O–CO2 solubility in mafic magmas

MafiCH: a general model for H2O–CO2 solubility in mafic magmas

Evolution of Ore-Forming Fluids and Gold Deposition of the Sanakham Lode Gold Deposit, SW Laos: Constrains from Fluid Inclusions Study

The Sanakham gold deposit is a newly discovered gold deposit in the Luang Prabang (Laos)–Loei (Thailand) metallogenic belt. It consists of a series of auriferous quartz-sulfide veins, which is distinguished from the regional known porphyry-related skarn and epithermal gold deposits. There are four mineralization stages identified in Sanakham, with native gold grains mainly occurring in stages II and III. Evolution of ore-forming fluids and gold deposition mechanisms in Sanakham are discussed based on fluid inclusion petrography, microthermometry, and Laser Raman spectroscopy. The original ore-forming fluids belong to a medium-high temperature (>345 °C) CH4-rich CH4–CO2–NaCl–H2O system. In stages II and III, the ore fluids evolve into a NaCl–H2O–CO2 ± CH4 system characterized by medium temperature (~300 °C), medium salinity (~10 wt% NaCl eq.), and CO2-rich (~10% mol). They might finally evolve into a NaCl–H2O system with temperature decreasing and salinity increasing in stage IV. Two fluid immiscibility processes occurred in stages II and III, which created high-CH4 & low-CO2 and low-CH4 & high-CO2 end-members, and CO2-poor and CO2-rich endmembers, respectively. Gold-deposition events are suggested to be associated with the fluid immiscibility processes, with P–T conditions and depth of 236–65 MPa, 337–272 °C, and 8.7–6.5 km, respectively.

High-yield electrochemical upgrading of CO2 into CH4 using large-area protonic ceramic electrolysis cells

Electrochemical production of commodity chemicals via CO2–H2O co-electrolysis using solid oxide electrolysis cells presents a promising cost-effective energy-storage approach. Here, we harness the unique property of protonic ceramic electrolysis cells (PCEC) and demonstrate direct electrochemical production of CH4 from CO2–H2O in a PCEC unit-cell stack. An exceptional CH4-yield ratio of 34.6% from only CO2–H2O reactants and greater than 70% with exhaust H2 recycle were achieved under an electrolysis current of –1 A cm–2 at 450 °C. Additionally, the electrochemical co-conversion of CO2–H2O offered a higher CH4-yield ratio compared to the thermochemical conversion of CO2–H2 under certain operating conditions, indicating possible electrochemical promotion of catalytic CO2 methanation. Techno-economic analyses were conducted to reveal potential operating conditions that yield a promising levelized cost of fuel production. The demonstrated good performance of the unit-cell stack shows promising scalability of PCECs for practical application from a system-level viewpoint.

Structural and dynamic analyses of CH4-C2H6-CO2 hydrates using thermodynamic modeling and molecular dynamic simulation

Adding CO2 into the CH4-C2H6 (C1-C2) hydrate system introduces much complexity to the stability of C1-C2-CO2 hydrates due to the occupancy competition of CO2 for the small and large hydrate cages with CH4 and C2H6 molecules. Also, the effect of weak hydrogen bonding between CO2 and cage H2O molecules has not been elucidated. In this work, the thermodynamic modeling and molecular dynamic (MD) simulation methods are applied to explore the impact of gas composition on the motion of H2O and gas molecules in the C1-C2-CO2 hydrates. According to the calculated results of the thermodynamic model, the sII C1-C2 hydrates are transformed to stable sI hydrates as CO2 is added. The results of the MD simulation indicate that the stability of C1-C2-CO2 hydrates is reduced as the CO2 composition increases. The weak hydrogen bonds between CO2 and cage H2O molecules facilitate the reorientation of H2O. The gas composition will influence the average translational motion as well as the amplitude and the frequency of oscillations in the translational and rotational curves of gas molecules. The variation in the average MSD curves of CH4 molecules is due to different cage occupancy induced by the competition of CO2 for the large hydrate cages with CH4. The oscillation amplitude of CH4, C2H6, and CO2 in the hydrate cages are affected by the interactions between gas molecules, with the dominant interaction changing with the gas composition. The oscillation frequency in the rotational motion curves of CO2 is suppressed by the weak hydrogen bonding between CO2 and cage H2O molecules.

Simultaneous Compression and Absorption for Energy‐Efficient Dissolution of Gases in Liquid

AbstractIn this study, a novel approach for energy‐efficient dissolution of gases in liquid is presented, which significantly reduces the compression work. The core of the one‐step process is the simultaneous operation of compression and absorption. The liquid was injected into a cylinder filled with the gas, while a piston compressed the mixture during the injection time. The solubility increases with increasing system pressure, so that the compression work of the gas phase is permanently reduced on the one hand by the permanent reduction of the gas volume and on the other hand by the nearly isothermal compression process. The approach is demonstrated in this study using liquid H2O and gaseous CO2 compressed up to 10 bar. The theoretical energy savings of the novel process compared to the conventional two‐stage process is 41.2 % for the selected fluids. A maximum energy saving of 40.8 % was demonstrated in the experiments. The results also show that the energy saving depends on the curve of the piston speed and the injection time.

Analysis of routes for electrochemical conversion of CO2 to methanol

Abstract In the context of peak carbon and carbon neutrality, the utilization of CO2 has attracted attention with the aim of reducing carbon emissions by converting CO2 into high-value chemicals or energy. Methanol (MeOH), which is both a hydrogen and a carbon carrier, is considered the most promising among the CO2-conversion products. This paper focus on routes for electrochemical conversion of CO2 to MeOH using green power and green hydrogen to achieve negative CO2 emissions. Three feasible technical routes for electrochemical conversion of CO2 to MeOH are proposed in this paper: Route 1, electrolysis of water to H2 and hydrogenation of CO2 to MeOH; Route 2, electrochemical reduction of CO2 to MeOH; and Route 3, co-electrolysis of CO2–H2O to syngas and synthesis of MeOH from syngas. Techno-economic assessments of the three routes are conducted using technical maturity surveys, system simulations and cost analyses to provide reference data for route selection for CO2 conversion to MeOH in China. Compared with the other routes, Route 1 is advantageous in terms of technical maturity and commercial application prospects. Although Route 1 is presently economically unviable, it is expected to achieve profitability and commercial application in the future with decreases in the cost of renewable power and continuous development of water-electrolysis technology.

Anisotropic rate-dependent saturation functions for compositional simulation of sandstone composites

Determination of representative saturation functions for permeable reservoir sandstones requires consideration of mm-cm scale laminations and crossbedding common in these heterogeneous porous media. Modelling selected laminated sandstones from CO2CRC's Otway International Test Centre in Victoria, Australia as bimodal composites of different rock types, we analyse drainage relative permeability parallel and perpendicular to the laminae for a range of driving gradients. The results from these numeric drainage experiments are curve fit across a continuous range of flow rates between the capillary and viscous limits. Our analysis shows that laminae-related small, but spatially correlated grainsize and permeability variations give rise to flow-rate dependent drainage behaviour at the bed scale. The flow direction- and rate-dependent behaviour is captured by a new set of anisotropic extended saturation functions that are implemented and presented in a form that is suitable for compositional simulation in the system CO2–H2O–NaCl. For the first time, these new constitutive relationships permit an investigation of feedbacks between the reservoir-scale flow regime and bed-scale phase mobility. To illustrate the application of these functions in reservoir simulation, meter-scale plume spreading simulations are presented for a suite of ten homogenised fluvial-to-estuarine sandstones from the Otway facility.

Ca-Si-Al interactions induced char structure and active site evolution during gasification–A comparative study based on different gasifying agent

Catalytic steam gasification, as a promising technology for producing hydrogen-enriched syngas, has been a hotspot in recent studies. This study aims to analyze the role of calcium-silicon-aluminum (Ca-Si-Al) interactions in char gasification and distinguish the difference of the interaction in different gasifying agent. The gasification reactivity of coal char was closely linked with the physiochemical structure and the mineral interactions. It was found that whether in CO2 or H2O, the calcium oxide (CaO) has function to promote the generation of mesopores, which is beneficial to the diffusion of reactant and product gases. The scanning electron microscopy (SEM) images showed that no SiO2 particles agglomerated in coal char containing silicon-aluminum ((Si-Al)-coal), which was a good reason why Si-Al inhibited gasification severely; the well dispersed SiO2 particles have no function to adsorb the gasifying agent molecular to transfer oxygen. New minerals including Ca2Al2SiO7, Ca2SiO4 and CaSiO3 were formed in CO2 and H2O, while CaAl2Si2O8 only was detected in H2O. These new minerals exert a positive effect on active site in CO2 but negative effect in H2O. While in H2O, compared with active sites, the mesopores dominate the reaction more. Overall, the interactions catalyze gasification to a moderate degree whether in CO2 or H2O.

Introducing our 2022 Early Career Advisory Board Members

Introducing our 2022 Early Career Advisory Board Members

New data on the formation conditions of the Drazhnoye deposit gold mineralization (Republic Sakha, Yakutia)

New results of thermal, baric, and geochemical studies indicate that quartz veins within the deposit were formed in mesozonal conditions at depths 3–9 km from heterogeneous CO2–H2O fluids containing water and carbon dioxide with low concentrations of salts and high concentrations of CO2, which is typical for ore-forming fluids of orogenic vein gold deposits. According to the phase composition, there are three types of fluid inclusions: 1) carbon dioxide- water; 2) gas-filled with dense carbon dioxide; 3) biphasic gas-liquid water-salt solutions. There are Na, Mg, and Fe chlorides predominated in the ore-forming fluids. It is assumed that the fluids migrated along the regional Adycha-Taryn shear zone, uplifting to the Earth’s surface at supra-lithostatic pressures, followed by the deposition of ore elements and the vein quartz formation during tectonic movements along shear zones.

Effects of HVAC on combustion-gas transport in residential structures

Time-resolved concentrations of oxygen (O2), carbon dioxide (CO2) and water vapor (H2O) produced by controlled propane gas burners are measured at three locations in a residential structure equipped with a heating, ventilation and air-conditioning (HVAC) system. Experiments are conducted to assess the effects of HVAC operating status (off vs. on) and the impact of bedroom door position (open vs. closed) on species concentrations. Change in concentration up to the flame extinction point, the rate of change, and the transport time for the measured species at each location is compared. The CO2–O2 concentration ratio derived from these experiments correlates strongly with the stoichiometric combustion ratio. The CO2–H2O and O2–H2O ratios have a relatively strong correlation though with slightly higher variability. Both the HVAC status and bedroom door position have statistically significant influence on the total change in concentration for all the measured species. However, HVAC status only has a statistically significant effect on the rate of change of H2O but not CO2 and O2 concentrations. For all three species in both bedrooms, the concentrations typically begin to change later in experiments with HVAC off than experiments with HVAC on.

Confining and Highly Dispersing Single Polyoxometalate Clusters in Covalent Organic Frameworks by Covalent Linkages for CO2 Photoreduction.

Single clusters have attracted extensive research interest in the field of catalysis. However, achieving a highly uniform dispersion of a single-cluster catalyst is challenging. In this work, for the first time, we present a versatile strategy for uniformly dispersed polyoxometalates (POMs) in covalent organic frameworks (COFs) through confining POM cluster into the regular nanopores of COF by a covalent linkage. These COF-POM composites combine the properties of light absorption, electron transfer, and suitable catalytic active sites; as a result, they exhibit outstanding catalytic activity in artificial photosynthesis: that is, CO2 photoreduction with H2O as the electron donor. Among them, TCOF-MnMo6 achieved the highest CO yield (37.25 μmol g-1 h-1 with ca. 100% selectivity) in a gas-solid reaction system. Furthermore, a mechanism study based on density functional theory (DFT) calculations demonstrated that the photoinduced electron transfer (PET) process occurs from the COF to the POM, and then CO2 reduction and H2O oxidation occur on the POM and COF, respectively. This work developed a method for a uniform dispersion of POM single clusters into a COF, which also shows the potential of using COF-POM functional materials in the field of photocatalysis.

Air temperature equation derived from sonic temperature and water vapor mixing ratio for turbulent airflow sampled through closed-path eddy-covariance flux systems

Abstract. Air temperature (T) plays a fundamental role in many aspects of the flux exchanges between the atmosphere and ecosystems. Additionally, knowing where (in relation to other essential measurements) and at what frequency T must be measured is critical to accurately describing such exchanges. In closed-path eddy-covariance (CPEC) flux systems, T can be computed from the sonic temperature (Ts) and water vapor mixing ratio that are measured by the fast-response sensors of a three-dimensional sonic anemometer and infrared CO2–H2O analyzer, respectively. T is then computed by use of either T=Ts1+0.51q-1, where q is specific humidity, or T=Ts1+0.32e/P-1, where e is water vapor pressure and P is atmospheric pressure. Converting q and e/P into the same water vapor mixing ratio analytically reveals the difference between these two equations. This difference in a CPEC system could reach ±0.18 K, bringing an uncertainty into the accuracy of T from both equations and raising the question of which equation is better. To clarify the uncertainty and to answer this question, the derivation of T equations in terms of Ts and H2O-related variables is thoroughly studied. The two equations above were developed with approximations; therefore, neither of their accuracies was evaluated, nor was the question answered. Based on first principles, this study derives the T equation in terms of Ts and the water vapor molar mixing ratio (χH2O) without any assumption and approximation. Thus, this equation inherently lacks error, and the accuracy in T from this equation (equation-computed T) depends solely on the measurement accuracies of Ts and χH2O. Based on current specifications for Ts and χH2O in the CPEC300 series, and given their maximized measurement uncertainties, the accuracy in equation-computed T is specified within ±1.01 K. This accuracy uncertainty is propagated mainly (±1.00 K) from the uncertainty in Ts measurements and a little (±0.02 K) from the uncertainty in χH2O measurements. An improvement in measurement technologies, particularly for Ts, would be a key to narrowing this accuracy range. Under normal sensor and weather conditions, the specified accuracy range is overestimated, and actual accuracy is better. Equation-computed T has a frequency response equivalent to high-frequency Ts and is insensitive to solar contamination during measurements. Synchronized at a temporal scale of the measurement frequency and matched at a spatial scale of measurement volume with all aerodynamic and thermodynamic variables, this T has advanced merits in boundary-layer meteorology and applied meteorology.

Thermochemical Energy Storage by Calcium Looping Process that Integrates Co2 Power Cycle and H2o Steam Power Cycle

Thermochemical Energy Storage by Calcium Looping Process that Integrates Co2 Power Cycle and H2o Steam Power Cycle

Theoretical Insight into the Competitive Effect of Co2 and Additive H2o in Coke Gasification

Theoretical Insight into the Competitive Effect of Co2 and Additive H2o in Coke Gasification

Efficient and green production of manno-oligosaccharides from Gleditsia microphylla galactomannans using CO2 and solid acid in subcritical water

This study aimed to produce manno-oligosaccharides (MOS) from Gleditsia microphylla galactomannans (GMG) using CO2 and solid acid (Amberlyst-35) in subcritical water. The optimal condition for MOS preparation was 3 MPa CO2, 0.1 g/g solid acid (relative to GMG) at 150 °C for 40 min. The maximum MOS yield with a degree of polymerization from 2 to 4 (M2-M4) was 52.19%, which doubled the yield of MOS compared to either using solely CO2 or solid acid. Solid acid showed excellent performance in producing MOS under subcritical H2O–CO2 condition, due to the enhanced mass transfer efficiency and increased H+ concentration in the reaction system. The solid acid can be easily separated and reused. Comparing with traditional methods used to produce MOS, this approach has many merits such as higher galactomannan hydrolysis efficiency (largely reduced time and higher MOS yield), purer M2-M4 product, lower costs, and more environmental-friendly.

Genesis of the Aobaotu Pb–Zn deposit in the southern Great Xing'an Range, NE China: Constraints from geochronology and C–H–O–S–Pb isotopic and fluid inclusion studies

The Aobaotu Pb–Zn deposit (470,700 t; 1.51% Pb, 2.30% Zn) in the southern Great Xing'an Range, northeastern China, is hosted by the Late Jurassic volcanic tuff and structurally controlled by a near‐east–west‐trending fault. Three stages of mineralization were identified, namely, stage I of quartz ± pyrite veins, stage II of quartz–polymetallic sulphide veins, and stage III of late quartz–calcite veins. The quartz and calcite that formed in the three stages were selected for fluid inclusion and C–H–O isotope analyses. The results show that the ore‐forming fluid of the deposit belongs to the H2O–CO2–NaCl system at a medium temperature (concentrated at 220–300°C) and in low salinity (0.7–12.1 wt% NaCl equiv). The δ13C values of the calcite and ankerite are in the range of −8.4 to −4.8‰, indicating that as a source of deep magma. The δDV‐SMOW and values of quartz range from −108 to −88‰ and 4.55 to 5.85‰, respectively, indicating that the initial fluid of the Aobaotu deposit was a mixture of residual magmatic and meteoric water. Sulphur isotope analysis of the sulphide minerals, that is, sphalerite, galena, pyrite, and chalcopyrite, yield δ34S value in a range of 1.44–4.94‰, indicating that sulphur is mainly derived from magma. In addition, the Pb isotopic composition of the sulphides indicates that the ore‐forming material has a mixed crust–mantle source. Zircon U–Pb dating suggests that the formation of the Aobaotu deposit is genetically related to the granodiorite porphyry (130.3 ± 0.9 Ma). The combined geochronology and isotopic evidence suggest that the Aobaotu deposit is a magmatic‐hydrothermal vein‐type Pb–Zn deposit, opposite to a volcanic Pb–Zn deposit as suggested before. The Aobaotu deposit formed in an extensional tectonic setting caused by the rollback of the Palaeo‐Pacific Plate.

The rise time of the change of cometary brightness during its outburst

The paper presents a new method for determining the change in the brightness of a comet during an outburst in which particles are ejected into the coma at a uniform rate, i.e. via a long-lived jet. In the proposed approach, the mass flow rate by a jet and the time it takes to increase the brightness of the comet play key roles. Absolute values adopted for H2O ice and CO2 ice were taken from measurements by Rosetta of the jets observed on 67P/Churyumov–Gerasimenko. These two parameters significantly affect the amplitude of the change in the brightness of a comet during its outburst. The performed numerical calculations concern a hypothetical comet from the Jupiter family for which it was assumed that its sublimation activity was controlled by the sublimation of water ice and carbon dioxide. Based on numerical simulations, it was shown that the difference between the change in brightness for H2O ice and CO2 ice is about −3.4 magnitude for the same fraction of the area that is active and the same mass flow rate. This value corresponds to the rise time of the amplitude of the brightness change t = 3 h. In addition, it should be emphasized that this difference is a consequence of thermodynamic parameters, such as the speed of sublimating gas molecules, the sublimation rate of given ice, which determine the numerical values of the individual scattering cross-sections C(t1) and C(t2).

Point‐Defect Engineering: Leveraging Imperfections in Graphitic Carbon Nitride (g‐C3N4) Photocatalysts toward Artificial Photosynthesis (Small 48/2021)

Point-Defect Engineering Solar energy is an abundant source of renewable energy, which can be harnessed via photocatalysis. Of which, point-defect engineering is a robust strategy to tune physico-chemical properties of graphitic carbon nitride toward enhanced photocatalytic H2O splitting, CO2 and N2 reduction. A comprehensive review is presented by Wee-Jun Ong and co-workers in article number 2006851.