CO2 Environment Research Articles

Effect of temperature on the ability to synthesize SiC from rice husks

Agricultural production in Vietnam annually generates a substantial volume of by-products and waste, with rice husks constituting the predominant fraction. Due to their meager economic value, rice husks are typically deemed agricultural waste and are commonly disposed of through incineration or discharge into rivers, contributing significantly to environmental pollution. In this investigation, rice husks were employed as the principal raw material for synthesizing silicon carbide. A blend of rice husks and silica gel in a ratio of 1.4/1 was subjected to sintering in a CO2 environment within the temperature range of 800 °C–1300 °C for 30 min. The chemical composition of the resultant product post-pyrolysis was ascertained in accordance with the ISO 21068–2:2008 standard. The capacity for SiC formation was further assessed utilizing Fourier transform infrared spectroscopy and x-ray diffraction. The outcomes revealed that the optimal temperature for SiC synthesis was 1200 °C. The composition of the sample post-pyrolysis was determined as 20.4% SiC, 51.2% SiO2, and 26.4% C (%wt). The primary phase constituents encompass amorphous carbon, cristobalite, α-SiC, and β-SiC. Scanning Electron Microscopy/ Energy Dispersive x-ray imaging of the product at 1200 °C exhibited dispersed SiC crystals on a SiO2-C substrate. The presence of SiC suggests the potential application of the product as a wear-resistant material.

Corrosion Behavior of N80 Steel in Underground Supercritical CO2 Environments

Corrosion Behavior of N80 Steel in Underground Supercritical CO2 Environments

Prediction and modeling of tie-dye polyester fabric's texture and color feature in supercritical carbon dioxide

To mitigate the water-intensive challenges of tie-dye clothing production and address the absence of objective evaluation for finished products, we have explored the correlation between tie-dye techniques in supercritical carbon dioxide (SC-CO2) and image patterns. Employing digital image processing, we extracted the average HSV three-component value of the valid tie-dye area, the proportion of incompletely dyed area in the HSV color space, and the initial three texture features of the digital tie-dye image using the Tamura method. We scrutinized five factors in the supercritical CO2 dyeing process: rotational speed, dyeing temperature, dyeing pressure, dye concentration, and dyeing time. The single-factor climbing test revealed that temperature and pressure are the predominant factors influencing tie-dyeing performance. We propose a correlation between the texture parameters of tie-dyeing and the swelling effect of polyester fabric in a supercritical CO2 environment. Subsequently, we conducted two-factor tests on temperature and pressure to investigate their specific effects on the parameters of supercritical polyester tie-dyeing. The results indicated significant changes in regularity, saturation, and the proportion of undyed area with variations in dyeing temperature and pressure. Building upon these findings, we developed an artificial neural network for predicting tie-dye dyeing temperature and pressure in supercritical CO2, utilizing features regularity, saturation, and proportion of undyed area as inputs. In the 105st round, experimental results demonstrated an accuracy of 0.99445, substantiating the efficacy of tie-dye pattern features in supercritical CO2 for technique forecasting.

Corrosion of Zinc Cold Spray Coatings in a Wet Sweet and Sour Gas Environment

Internal corrosion is a problem for steel pipelines transporting natural gas or CO2 containing water and partial pressures of H2S higher than 0.3 kPa (0.05 psi). This work aims to mitigate internal corrosion in steel pipelines transporting natural gas containing H2S using cold spray coatings. Two types of the cold spray binary metallic coatings (zinc chromium [ZnCr]. zinc niobium [ZnNb]) were studied using electrochemical techniques: potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy. The corrosion resistance of cold spray coatings (ZnCr, ZnNb) was evaluated in an environment containing 4 bar CO2 pressure, simulating the partial pressures found in gas transmission lines over a solution of 3.5 wt% NaCl heated to 40°C. A concentration of 0.003 M Na2S2O3·5H2O, corresponding to H2S partial pressures around 0.079 bar (1.146 psi), was used to simulate sour conditions. Postcorrosion surface characterization was performed using a scanning electron microscope (SEM) equipped with an energy-dispersive x-ray spectroscope (EDS) and x-ray diffraction analysis. The data showed that the presence of 0.003 M Na2S2O3·5H2O shifted the corrosion potential to more anodic values and decreased the corrosion current density. Both coatings showed similar behavior after 1 h of exposure in the CO2/H2S environment, indicating that similar electrochemical reactions were occurring on ZnNb and ZnCr. SEM images and EDS surface analyses for specimens showed a significant change in the surface chemical composition of carbon steel coated with ZnNb and ZnCr after 24 h of immersion. In the presence of thiosulfate (under sour conditions), the formation of corrosion product layers (ZnCO3 and ZnS) on top of ZnNb and ZnCr coatings increased their corrosion resistance, which helped to reduce their corrosion by a factor of 2. Under a sweet environment, the corrosion rates for steel coated with cold spray coatings after 14 d of exposure are lower than that for galvanized steel by a factor of 5 due to the ZnCO3 layer formed on top of the coatings. The ZnCO3 layer formed on the steel surface acts as a physical barrier against corrosion by blocking the diffusion of corrosive species to the surface. No localized attack was observed. ZnCr Cold spray coating with defect showed promising corrosion protection against CO2 corrosion (sweet corrosion) after 14 d of exposure to a CO2 environment. The scratch on the coating simulated damage created in service, and it was deep enough to expose the substrate material (steel). The formation of zinc oxide (ZnO) and zinc carbonate (ZnCO3) on the scratch confirmed the cathodic protection of the steel by ZnCr and ZnNb coatings.

Hydrogen embrittlement susceptibility of AISI 4140 alloy-steel under cathodic protection and in H2S and CO2 environment

The susceptibility to hydrogen embrittlement (HE) of AISI 4140 steel when subjected to environments such as those found in offshore oil and gas fields is investigated. Hydrogen charging was carried out for 15 days using two different hydrogen sources, cathodic protection (CP) and corrosion in a saline solution containing high concentrations of H2S and CO2 (SC-sour corrosion). The steel specimens were austenitized at 850 °C, oil-quenched at ambient temperature, followed by tempering for 18 min at 350, 450, and 600 °C. The effect of tempering temperatures on hydrogen embrittlement susceptibility was also investigated. Tensile strength testing, scanning electron microscopy (SEM), and fractography analysis were used to correlate the HE with microstructural and environmental conditions. The results revealed that both hydrogen charging conditions increased the steel hardness and decreased ductility, with this effect being more pronounced at lower tempering temperatures and SC-hydrogen charging. Fracture surfaces of the steel tempered at 600 °C with hydrogen charged exhibited predominantly ductile behavior with the presence of dimples, while at 350 and 450 °C surface fractures showed cleavage facets as a consequence of brittle behavior. In general, the AISI 4140 steel hydrogen embrittlement index (%EI) was higher for hydrogen charging induced by SC compared to CP.

Rapid wet grinding carbonation of sintering red mud for highly efficient CO2 sequestration and Cr solidification

Sintering red mud (SRM) is an alkaline and aqueous solid waste from bauxite sintering for alumina production. The challenges in the effective utilization of SRM are strong alkalinity, aqueous state and leaching toxicity of the heavy metals. Herein, a rapid wet grinding carbonation technique of simultaneous injection of CO2 in wet grinding process was proposed. The rapid carbonation of alkaline metal ions and the efficient solidification of heavy metal ions were achieved in the wet grinding carbonation. After 40 min of short-term carbonation, the CO2 uptake and carbonation degree of SRM reached 30.25 g CO2/100 g SRM and 79.31% respectively. The high-efficiency CO2 uptake of SRM was attributed to the continuous stripping of the attached surface CaCO3 layer by wet grinding, the constantly exposed new surface area after refinement and the largely increased Ca2+ concentration, which was 12.5 times the initial value at 10 min. Furthermore, the simultaneous carbonation realized the solidification of dissolved chromium ion (Cr(III)/Cr(VI)), which was transformed into CaCrO4, Ca3Cr2(OH)12 or Cr(OH)n(CO3)n(3n-3)- complexes under the weak acid environment of CO2. After 40 min of wet grinding carbonation, the Cr concentration was notably decreased by 85.71 %, which was lower than the limit of groundwater standard requirement.

Atomic insights into the corrosion behavior of Fe-Cr alloys in supercritical CO2 environment

In this work, the corrosion process of Fe-Cr alloys in flowing CO2 was simulated using molecular dynamics within an extended ReaxFF force field. The effects of Cr content, temperature variations, impurity gases and vacancy defects were discussed. The corrosion process was dominated by oxidation and carburization reactions, with the oxidation rate higher than carburization rate, resulting in the formation of a carbide layer within the central region between two oxide layers. The increase in Cr content tended to decelerate corrosion, while raising temperature aggravated the corrosion of Fe-Cr alloy. The presence of O2 and SO2 impurities was found to thicken the corrosion layer, in contrast to the effects of CO and H2O impurities. A notable finding highlighted the positive influence of 2% vacancy defects in enhancing the corrosion resistance of the Fe-Cr alloy. The Al2O3 coating achieved a good corrosion protection by inhibiting the dissociation of CO2.

Sludge-derived biochar as an additive in cement mortar: Mechanical strength and life cycle assessment (LCA)

Given the growing concern about environmental contamination risks, the management of sewage sludge (SS) from wastewater treatment plants is becoming more challenging. Thus, alternative pathways that offer value-added opportunities with minimal environmental impacts are needed. This study investigates the use of 0.52 wt% biochar (BC) powders generated from the pyrolysis of the SS in an N2 or CO2 environment, as an additive in cement mortar mixtures. The effect of dry and pre-wetted BC on the fresh properties, phase formation, compressive and tensile strength properties of cement mortar mixtures were assessed. Thereafter, life cycle assessment (LCA) of Plain and BC-modified mortar mixtures were evaluated, and the environmental impacts arising thereof were quantified. Results showed that whereas the BC had an infinitesimal effect on mix fresh properties, it caused approximately 1734% and 10–18% increases in compressive and tensile strength, respectively. Regardless of the pyrolysis condition, pre-wetted BC had a superior impact on mechanical strength evolution. LCA results showed that except for minor, net increases in particulate matter/water consumption potential, the rest of the impact categories associated with the production of 1 m3 of cement mortar decreased with the addition of the BC. In terms of Global Warming Potential (GWP) per unit 28d compressive strength, the BC-modified mixtures yielded values that were lower than that of the Plain mortar by about 1629%. Therefore, these research findings indicate that the use of SS-derived BC as a low-dose additive in cement composites could help the construction industry mitigate its negative environmental footprints.

High-temperature corrosion and carburization behaviour of austenitic stainless steels in impurity-added CO2 environments

The corrosion and carburization behaviour of four austenitic stainless steels were evaluated in CO2 and CO2+impurities (CH4, CO and O2) at 600 °C. Exposure to CO2, CO2+CH4, and CO2+CO environments showed poor corrosion resistance, especially in 316 grades with the spallation of Cr2O3 layer and breakaway corrosion. Conversely, materials showed improved corrosion resistance in CO2+O2 environment with thin Cr2O3 layer. TEM analysis of 316LN revealed carbon-accumulated layer at the Cr2O3–matrix interface for highly corrosive environments. The degradation of Cr2O3 adherency is correlated with the carbon-accumulated layer, resulting from the high carbon activity in CO2, CO2+CH4, and CO2+CO environments.

Influence of environmental conditions on the morphological evolution of bismuth oxide nanostructures via pulsed laser ablation in liquids

Bismuth oxide nanomaterials are increasingly recognized for their promising electronic and optical properties, particularly in electrochemical and biomedical applications. This study demonstrates that various bismuth oxide nanostructures can be synthesized through pulsed laser ablation in liquids (PLAL) by adjusting the concentration of dissolved gases from ambient conditions. Structural and compositional analyses were performed using x-ray diffraction, Raman spectroscopy, FTIR spectroscopy, and morphological investigations were conducted using atomic force microscopy and transmission electron microscopy. Our findings indicate that factors such as dissolved gases, laser fluence, and nanoparticle aging are crucial in determining the final structure and composition of the resulting nanomaterial. The phases observed ranged from spherical metallic bismuth nanoparticles to monoclinic bismuth oxide nanowire bundles, and orthorhombic bismuth carbonate oxide nanosheets. Dissolved gases are shown to influence not only the primary particles formed immediately after ablation, but also significantly impact the aging process of the colloid as well. Additionally, fluence plays an important role in the production of reactive oxygen species, thereby influencing the reactive pathways experienced by the ablated material and its subsequent formation into nanostructures. A notable result, emphasizing the significance of factors such as liquid environment and fluence when performing PLAL on reactive targets like bismuth, is seen in high fluence (20 J/cm2) samples under ambient conditions. These samples initially display an amalgamation of α-Bi2O3 nanowire bundles and carbonate nanosheets, which upon aging, transition to predominantly bismuth oxide nanowire bundles. This contrasts with samples produced in a saturated CO2 environment where bismuth carbonate nanosheets remain highly stable in the colloid.

Exploring microalgal nutrient-light synergy to enhance CO2 utilization and lipid productivity in sustainable long-term water recycling cultivation

In this work the effects of nutrient availability and light conditions on CO2 utilization and lipid production in Micractinium pusillum KMC8 is reported. The study investigated the ideal nitrogen concentrations for growth and nitrogen utilization in a 15% CO2 environment. Logistic and Gompertz models were employed to analyze the kinetics of KMC8 cell growth. Compared to 17.6 mmol L−1 control nitrogen, which generated 1.6 g L−1 growth, doubling and quadrupling nitrogen concentrations boosted biomass growth by 12.5% and 28.78%. At 8.6 mmol L−1 nitrogen, the growth decreased but lipid productivity increased to 18.62 mg L−1 day−1. At 70.6 mmol L−1 nitrogen, elevated nitrogen levels maintained an alkaline pH above 7 and enhanced CO2 mitigation, achieving 2.27% CO2 utilization efficiency. Nitrogen shows a positive correlation with higher rates of carbon and nitrogen fixation. The investigation extends to find out the influence of phosphorus and light conditions on microalgae. Increasing light intensity incrementally from 150 to 1200 μmol m−2 s−1 with more phosphorus increased biomass productivity by 85% (255 mg L-1 day−1) and lipid productivity by 2.5-fold (84.76 mg L-1 day−1), with 3.3% CO2 utilization efficiency compared to directly using 1200 μmol m−2 s−1. This study suggests a water recycling-fed batch cycle with gradual light feeding, which results in high CO2 fixation (1.1 g L−1 day−1), 7% CO2 utilization, and significant biomass and lipid productivity (577.23 and 150 mg L−1 day−1). This approach promotes lipid synthesis, maintains carbon fixation, and minimizes biomass loss, thus supporting sustainable bioenergy development in a circular bio-economy framework.

Electrochemical properties of Sr-doped La2-xSrxCe2O7-δ hydrogen separation membrane

The prominence of hydrogen energy has brought membrane separation technology to forefront attention. La2Ce2O7, possessing a fluorite structure, exhibits notable stability in both H2O and CO2, rendering it a prospective material for membrane separation. The impact of Sr doping on the electrochemical characteristics of La2Ce2O7 was systematically investigated. The findings indicate that a minor addition of Sr2+ through doping enhances the electrical conductivity, with the most significant improvement observed in La2-xSrxCe2O7-δ (x = 0, 0.05, 0.15, 0.30) when doped by 0.05. Elevated temperature and increased hydrogen partial pressure on the feed side enhance hydrogen permeability. Hydrogen permeation is predominantly governed by bulk diffusion when the membrane thickness exceeds 0.59 mm, while for thicknesses below 0.49 mm, the process is influenced by both surface and bulk diffusion. Moreover, the doped La2Ce2O7 exhibit commendable stability in H2O and CO2 environments. Consequently, La2Ce2O7 emerges as a promising candidate for ceramic hydrogen separation membranes.

Quantitative measurement of sodium emissions during oxy-fuel combustion of a beech wood biomass particle using laser-induced breakdown spectroscopy

Oxy-fuel biomass combustion in a circulating fluidized bed is a clean and sustainable biomass utilization technology. Woody forest biomass is considered a promising source of renewable energy because of its widespread availability across the globe. However, effective biomass utilization in thermal power plants is largely limited by severe ash deposition and corrosion of heat transfer surfaces due to alkali metal and chlorine emissions during biomass combustion. In this study, laser-induced breakdown spectroscopy (LIBS) was applied to detect in-situ gas phase sodium (Na) emission during single particle combustion of widely available forest biomass, namely, beech wood. The operating conditions simulate the thermo-chemical conditions relevant to a fluidized bed combustor system, where the operating temperature varies between 1073K–1273K. This work aims to investigate the effect of O2 concentration, CO2 (oxyfuel environment), and particle size on the emission of sodium during the combustion of a single beech wood particle. The unresolved sodium doublet was used as the LIBS signal to quantify sodium emission concentration.Oxygen concentration is the most critical parameter affecting Na emissions, and an increase in O2 concentration led to higher Na emissions. It is observed that there is a significant reduction in the emission of Na in an O2/CO2 environment as compared to an O2/N2 environment. It is hypothesized that this drop in Na emissions in O2/CO2 environment could be due to lower particle temperatures caused by the lower diffusivity of O2 in CO2 as well as the endothermic gasification reaction in high CO2 environments. In addition, it is reported that the dissociation of sodium carboxylates and carbonates in the biomass matrix to release gaseous Na due to thermal decomposition is retarded at higher CO2 concentrations which could explain the drop in Na emissions. The effect of biomass particle size is pronounced mainly at lower concentration of O2 where, larger particles keep Na trapped in its matrix, however, at higher O2 concentrations (30%), the effect of particle size on Na emission is negligible.

Impacts of Eutrophication and Global Warming on the Emergence of Toxic Cyanobacteria blooms

Cyanobacteria, the oldest phytoplankton on the planet, cause toxic algal blooms in freshwater, estuarine, marine and fresh water habitats. According to recent study, eutrophication and climate change may contribute to the spread of dangerous cyanobacterial algae blooms. This study examines the correlation between eutrophication, climate change, and cyanobacterial taxa in freshwater (Microcystis, Anabaena, Cylindrospermopsis). Cyanobacterial genera have the capacity to compete for low inorganic phosphate concentrations and acquire organic phosphate molecules. Cyanobacteria, both diazotrophic (nitrogen (N2) fixers) and non-diazotrophic, may create blooms using a wide range of nitrogen sources. Some cyanobacterial blooms are linked to eutrophication, although others occur at low inorganic N and P concentrations. Cyanobacteria dominate phytoplankton assemblages at higher temperatures due to physiological (e.g., faster growth) and physical reasons (e.g., greater stratification), with distinct species exhibiting various temperature peaks. The impact of rising carbon dioxide (CO2) concentrations on cyanobacteria is unclear. However, some research shows that some genera of cyanobacteria thrive in low CO2 environments. Future eutrophication and climate change are expected to increase the frequency and size of dangerous cyanobacterial blooms, despite their complicated interactions

Combining Thermodynamics and Kinetics to Investigate the Corrosion of 3Cr Steel and HP-13Cr Stainless Steel in Extreme Oil-Gas Environments

ABSTRACT The corrosion behavior of 3Cr steel and HP-13Cr stainless steel (SS) under high temperature and CO2 or H2S pressure environments was investigated by immersion tests and multiple characterizations of corrosion films, and analyzed by combining the Pourbaix diagram and kinetic calculations. At 180 °C/3.8 MPa CO2, both 3Cr steel and HP-13Cr SS exhibited double-layered corrosion films, comprising a crystalline FeCO3 outer layer and an inner Cr2O3 and Cr(OH)3 layer. Furthermore, at 180 °C/3.8 MPa H2S, the corrosion films of both steels consist of an outer crystalline pyrrhotite and pyrite layer and an inner Cr2O3 and Cr(OH)3 layer. The corrosion resistance of 3Cr in H2S is inferior to that of HP-13Cr SS due to the influence of stress corrosion cracking but is close to that of HP-13Cr SS in CO2. Therefore, 3Cr steel could be considered a cost-effective alternative to HP-13Cr SS in CO2 environments.

Effect of ionic liquids on the corrosion behaviour of X80 pipeline steel

The study encompasses the synthesis of an ionic liquid corrosion inhibitor using the ion exchange method. Its impact on the corrosion and hydrogen permeation behaviour of X80 pipeline steel in a CO2 environment is thoroughly investigated. The findings reveal that the corrosion resistance and hydrogen atom diffusion of X80 pipeline steel exhibit an initial decline, followed by an increase with escalating inhibitor concentration. The nadir values are recorded at an inhibitor concentration of 500 mg·L−1, attaining a remarkable maximum inhibition efficiency of 97%. Following the addition of corrosion inhibitors, the formation of corrosion products notably decreases, indicating a positive inhibition effect on both corrosion and hydrogen permeation. Additionally, a correlation is successfully established between hydrogen permeation parameters and inhibitor concentration.

Zero carbon emission CCGT power plant with integrated solid fuel gasification

The development of a high-capacity power plant with zero CO2 emissions is an urgent task that will curb the increase in atmospheric temperature. It should have an efficiency comparable with existing TPPs, a low metal consumption rate, a high fuel versatility, and high flexibility. To meet these conditions, oxygen combustion is conducted in an environment of inert CO2, and most of the condensation heat from the combustion products is usefully utilized. This work presents a combined cycle gas turbine (CCGT) power plant with solid fuel gasification, oxy-fuel combustion, and a pressurized heat recovery steam generator (PHRSG). The two plant options are compared with the natural gas plant previously proposed. In the PHRSG, the low metal intensity is achieved by high average temperature differences, the pinch point value at 8–12 °C, and the intensification of heat transfer caused by the high pressure of combustion products and the condensation of water vapor in the tail surfaces. The developed plants are highly efficient when using coal, 51%, and 57.3% when using peat, and have acceptable CO2 avoidance costs of 72.7 €/t and 60.4 €/t. By combining these factors, and using well-developed materials, it will take less time to develop and implement this plant widely.

Experimental study on eco-friendly one-part alkali-activated slag-fly ash-lime composites under CO2 environment: Reaction mechanism and carbon capture capacity

This work studied the reaction mechanism and carbon capture capacity of novel type eco-friendly one-part alkali-activated slag-fly ash-lime composites (SFL) based on the change in SFL under CO2 environment from the macroscale to the microscale. Experimental results showed that SFL had a higher carbonation rate and led to the formation of carbonates (calcite, vaterite, aragonite), gypsum, amorphous calcium carbonate, and alumino-silicate gel. The carbonation reaction of SFL can be generally divided into three periods. In period 3, Al from the decomposed aluminum-bearing hydrates was gradually incorporated into the amorphous silica phase in the form of tetrahedral Al(-SiO)4 sites, which finally resulted in the formation of an alumino-silicate gel. The mass ratio of carbon capture in the complete carbonation zone of SFL is approximately 13%. Due to a large amount of CO2 binding in hydrates in a wider carbonation zone, the actual total capacity of carbon capture in SFL under CO2 environment was slightly lower than that in Portland cement. Thus, SFL had a better and adjustable capacity for CO2 capture compared to other low carbon binder materials.

Corrosion behavior of eutectic high-entropy alloys in supercritical CO2 environments

This study explores the corrosion resistance of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) in supercritical CO2 (S–CO2). The corrosion behavior was meticulously examined under conditions of 500 °C and 25 MPa CO2 over a duration of 800 h. The formation of distinct passivation layers on the face-centered cubic (FCC) and body-centered cubic (BCC) B2 phases was observed, leading to a cooperative passivation effect of Al and Cr. The protective Al2O3 oxide layers, which were dense and continuous, played a crucial role in inhibiting carburization and further oxidation, thereby significantly enhancing the corrosion resistance. Interestingly, no carburization was observed in this study.

Investigation of Iron Dissolution Mechanism in Acidic Solutions with and without Dissolved CO2—Part II: Time of Flight-Secondary Ion Mass Spectrometry 3D Mapping

Time-of-flight-secondary ion mass spectrometry (ToF-SIMS) 3D mapping and depth profiling were used to study the anodic iron dissolution mechanisms of mild steel in chloride-containing aqueous CO2 environments. The technique detected adsorbed hydroxide and chloride intermediates formed during the corrosion process, consistent with the proposed multipath reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous CO2 environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results on characterization of the specimens immersed in a chloride-containing solution with and without CO2 suggest that one role of aqueous carbonic species CO2 could be to accelerate the adsorption of chloride ions and the formation of chloride intermediates.