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In recent years, highway infrastructure in the Ningxia region of China has rapidly advanced. Cement–loess is extensively utilized in the roadbed and foundation reinforcement. It is necessary to conduct micro–macro-analysis and model derivation of the electrical resistivity on Ningxia cement–loess, which are beneficial for both the practical application of electrical resistivity and the evaluation of the geotechnical properties of cement–loess. Therefore, a series of electrical resistivity measurements, microstructural observations (scanning electron microscopy), mineral analyses (thermogravimetric analysis), and theoretical analyses were adopted on the cement–loess. The following conclusions can be drawn: The electrical resistivity is negatively related to dry density and water content, while it is positively related to cement dosage and curing age. A cement dosage of 6% exhibits a lower hydration reaction potential compared to 12%, causing a slower increase in electrical resistivity. The formation of calcium silicate gel around particles results in particle clustering and pore filling, reducing the pore area and increasing electrical resistivity. Increased hydration also decreases microscopic orientation, contributing to a higher electrical resistivity of cement–loess. Finally, a new three-dimensional electrical resistivity model was created, finding that the electrical resistivity of Ningxia cement–loess was determined by the dry density, water content (ρd·w), cement dosage, and curing age (aw·T) in an exponential function form. The new three-dimensional electrical resistivity model could be used in the high-efficiency evaluation of the cement–loess geotechnical parameter, offering valuable insights for the monitoring and maintenance of road infrastructure. [ABSTRACT FROM AUTHOR]

Co-firing zero-carbon fuels as an effective emission reduction strategy in coal combustion processes has garnered widespread attention. This paper proposes utilizing the combustion performance of oxy-hydrogen gas derived from zero-carbon fuels to address issues related to low-concentration coal powder combustion and nitrogen oxide emissions. A test apparatus for coal powder combustion initiated by oxy-hydrogen gas flames was constructed, and experimental and simulation methods were employed to study the impact of oxy-hydrogen gas flame initiation on the temperature inside the combustion chamber, coal powder gasification combustion reactions, and nitrogen oxide emissions. The results indicate that with an excess air coefficient of 0.8, as the oxy-hydrogen gas flow rate increased from 0.022 kg/h to 0.789 kg/h, the average temperature inside the combustion chamber increased from 801 K to 1459 K. The volatile matter release rate and its combustion reaction rate increased, leading to a decrease in volatile matter content. The peak concentration of volatiles was shifted from a position of 68 mm to 7 mm, and the proportion of Cchar–H2O reaction increased from 5% to 34%. NO emissions decreased from 132 ppm to 68 ppm, and the rate of reduction in NO emissions decreased from 15.38% to 5.49%. [ABSTRACT FROM AUTHOR]

Hydrogen energy is an important carrier for energy terminals to achieve green and low-carbon transformation. Hydrogen, as a carbon-free fuel, has great research and development value in the field of thermal power generation. This article proposes a solution for the stable combustion of coal powder using Oxy-hydrogen Gas ignition technology. An Oxy-hydrogen Gas flame injection coal powder combustion testing device was constructed to experimentally study the temperature distribution in the combustion chamber under Oxy-hydrogen Gas ignition technology, with primary air coal powder concentrations of 0.27, 0.32, and 0.36 (kg coal powder/kg air), as well as the concentration changes of volatile CO emissions during the ignition of coal powder using both Oxy-hydrogen Gas and CH4 flames. The sensitivity of the NO generation during coal gasification combustion under the Oxy-hydrogen Gas ignition was simulated and analyzed. The results show that at a coal powder concentration of 0.32 (kg coal/kg air) and an Oxy-hydrogen Gas flow rate of 2.1 L/min, the combustion effect of coal powder is the best, and the highest combustion chamber temperature can reach 1156 K; when the concentration of coal powder varies within a range from 0.32 to 0.27, the combustion chamber temperature can be maintained at around 850K, achieving stable combustion conditions for coal powder. The only product generated by the Oxy-hydrogen Gas combustion is high-temperature water vapor, which helps the rapid gasification of coal powder and releases a large amount of volatile CO, which is beneficial for the ignition and stable combustion of coal powder. [ABSTRACT FROM AUTHOR]

For ground improvement via microbially induced carbonate precipitation (MICP), the spatial distribution of biocementation considerably affects the mechanical performance of soil. This study systematically assessed the CaCO3 spatial distribution in sand columns with various grouting strategies. CaCO3 dispersion along the radial and vertical directions was quantitatively evaluated. Furthermore, a series of biochemical monitoring experiments was conducted to investigate the MICP process in sand. The results indicated that the reversed and downward chemical solution grouting and high rates of microbial grouting all promoted CaCO3 vertical uniformity. Moreover, the grouting strategy slightly affected the dispersion degree of radially distributed CaCO3. The variation coefficient basically ranged from 0.1 to 0.3. However, the variation coefficient for radially distributed CaCO3 along the vertical direction was significantly affected by the chemical grouting direction. The biochemical monitoring results indicated that 38% Ca2+ was even consumed near the chemical solution outlet in the chemical solution grouting process. The initial Ca2+ concentration during the intermittent period gradually decreased along the chemical solution grouting direction. The CaCO3 vertical distribution was controlled by a combination of the total MICP reaction time, biomass, and Ca2+ availability in the intermittent phase. Different CaCO3 distributions resulted in each grouting strategy exhibiting specific applicable engineering requirements. Furthermore, the carbon footprint was preliminarily evaluated. The results in this study provide references for the selection of grouting strategies for the MICP technique in engineering applications. [ABSTRACT FROM AUTHOR]

The chromium, iron or zirconium oligomer cations pillared interlayered montmorillonite supported 10 wt% MnOx were synthesized and studied for the flue gas NOx removal in metallurgical sintering process. The physicochemical properties of these catalysts were detected by some characterization methods, such as XRD, N2 adsorption–desorption, SEM, H2-TPR, and NH3-TPD. The Mn/Zr-PILM catalyst had the highest NOx conversion with 91.8% at 200°C. And the Mn/Fe-PILM catalyst had the highest NOx conversion between 140°C and 160°C. This is because zirconium or iron pillared montmorillonite increases the specific surface area and acidic sites of catalyst, which provided more adsorption sites and activation sites for NO and NH3, thus promoting low-temperature catalytic activity. The XRD results expressed that the pillared elements successfully pillared into Na-montmorillonite and the manganese active components had good dispersibility on the surface of catalyst. The N2 adsorption–desorption isotherm indicated that the metal pillared carrier had fractured mesoporous structure and the specific surface area was increased. The Mn/Zr-PILM and Mn/Fe-PILM catalyst had abundant acidity with 61.56 μmol/g and 57.71 μmol/g, respectively. The large amount of acid sites favored the adsorption of ammonia in the Langmuir–Hinshelwood or Eley–Rideal mechanisms in the low-temperature NH3-SCR process. The Mn/Fe-PILM catalyst had the best N2 selectivity and Mn/Cr-PILM has poor N2 selectivity. This was due to that iron element restrains the side reaction for N2O production and chromium promoted the N2O production by strong oxidation. [ABSTRACT FROM AUTHOR]

With the onset of global warming, the environment has profoundly changed. The melting of ice and slope instability were widely observed in the permafrost regions of the Qinghai–Tibet Plateau, which has destroyed infrastructure and threatened people's safety. For this study, we conducted a direct shear test, monitored field temperature, and performed a numerical simulation to explore the mechanism of slope instability in the permafrost regions of the Qinghai. The results show that the shear strength of the permafrost soil decreased with the increases in water content and thawing condition. Moreover, the thawing depth of the slopes increased with the rising temperature. From the temperature monitoring data and field observations, cracks and slope instability phenomena were observed in the Qinghai and occurred with the thawing of the permafrost soil. The safety of slopes in the permafrost regions decreased with increases in the temperature, slope gradient, and pore water pressure and with decreases in the shear strength parameters. In addition, the sliding interface had a direct correlation with the freeze–thaw interface, which is a migrated interface of water in liquid form. Therefore, the thawing of the permafrost soil causes the shear strength to decrease and pore water pressure to increase, which leads to slope instability in the permafrost regions of the Qinghai. [ABSTRACT FROM AUTHOR]

Porosity distribution is an important factor that affects premixed flame stability in packed beds. In this paper, the discrete element method is used to simulate the sphere packing in cylindrical, conical, and pyramidal packed beds. The anisotropic characteristics of porosity and ignition temperature distributions in packed beds are calculated and analyzed. The results show that the distance of the oscillation period of the packed bed filled with spheres of the same diameter is approximately equal to the sphere diameter. The oscillation amplitude of radial and axial porosity curves can be reduced by filling with mixed spheres of different diameters in cylindrical packed beds. The influence factors on the oscillation period distance of the radial and axial porosity curves include the diameter difference of the spheres and the mixing ratio of the number of spheres. In the cylindrical double‐layer packed beds, the interfacial porosity can be decreased by the increase of the diameter difference among the spheres. Increasing the divergent angle of the conical packed beds can weaken the influence of wall effect on the radial and axial porosities, which makes the uniformity of the porosity in the conical packed beds better than that of the cylindrical and the pyramidal beds. The inhomogeneity of tangential porosity distribution in the packed beds is inherent. In the packed beds, the ignition temperature of premixed gas is negatively correlated with porosity, sphere diameter, equivalent ratio of mixed gas, and divergent angle of conical packed beds, and it is positively correlated with superficial velocity. [ABSTRACT FROM AUTHOR]

As a novel, nature-like biomineralization process, microbially induced carbonate precipitation (MICP) has been successfully applied in soil stabilization. This study investigated the influence of biomass injected on the geotechnical performance of MICP treated sand. Grouting rate and particle sizes were also taken into account. The results showed that the injection of 1.0 or 1.2 PV biological solution achieved the most effective and uniform reinforcement of soil, depending on the grouting rate. Excessive biomass (1.5 PV biological solution) failed to promote the further improvement of the engineering performance of MICP reinforced sand. The relationship between strength and calcium carbonate content and SEM results indicated that for the small CaCO3 content, the improvement of soil strength is mainly controlled by the content of calcium carbonate rather than its distribution. When the amount of carbonate precipitation is sufficient to form bonding between soil particles, the distribution of calcium carbonate has a greater influence on mechanical properties. The strength of biocemented soil measured by layering indicated that the insufficient amount of biological solution (such as 0.5 PV biological solution) greatly weakened the reinforcement effect of soil away from the grouting port, and thus led to larger strength variability. Increasing the grouting rate of biological solution improved the uniformity of reinforcement, especially for medium grain sand. The results of this study provide a guide to facilitate the application of microorganisms in the engineering application practice of MICP. [ABSTRACT FROM AUTHOR]

Due to the influence of soil structure, structured soils exhibit significantly different mechanical behavior compared to the reconstituted soils having the same material. In this work, a theoretical analysis focusing on the mechanical behavior of structured soils is presented. Based on the mechanical behavior of the structured soil, a newly defined variable structural index was used as a measurement of the integrity of soil structure based on the concept of intrinsic compression line of intact structured soils. Furthermore, a novel correlation for the variation in volume of structured soils is established using effective stress and newly defined structural index as the constitutive variables. The novel correlation provided interpretation about the mechanism of compression behavior of the structured soils. Afterwards, the proposed correlation for the variation in volume was extended to triaxial stress state in the framework of subloading surface to include the effect of overconsolidation. Comparisons between the predictions and experimental results validated the proposed constitutive model for structured soils. [ABSTRACT FROM AUTHOR]

The electro-dewatering technique is an effective method to reinforce soft clay. Electro-dewatering experiments were conducted to assess the impact of salt content on electro-dewatering behaviors and effects with copper and stainless steel anodes. The changes in the current, accumulated drainage volume, and electro-osmotic flow velocity reflect the "catch point" phenomenon between the copper anode and the stainless steel anode. Moreover, the higher the salt content was, the earlier the appearance of the "catch point," which means that the effect of the copper anode was better in the early stages and then worse in the following stages than that of the stainless steel anode. Based on photographs of anode surface, SEM-EDS (Scanning electron microscopy-Energy dispersive spectrometry) and XRD (X-ray diffraction) results, we found that the copper anode surface produced green product, which observably decreased the conductivity of the copper anode and then reduced the effective electrical potential gradient. On the other hand, there were no added elements on the stainless steel anode surface after the electro-dewatering experiments, and the conductivity of the stainless steel anode was similar to its initial status. The above two points led to the appearance of the"catch point" phenomenon. The pH value of the stainless steel anode was lower than that of copper anode, and the concentration of Cl− had the opposite relationship. Because the effective electrical potential gradient of the stainless steel anode was higher than that of the copper anode after the "catch point," the water content of the stainless steel anode was lower than that of the copper anode. [ABSTRACT FROM AUTHOR]

The effects of manganese content, carrier calcination temperature, and catalyst calcination temperature of manganese-based zirconium pillared intercalated montmorillonite (Mn/Zr-PILM) catalysts were investigated for low-temperature selective catalytic reduction of NOx by NH3 (NH3-SCR) in the metallurgical sintering flue gas. The physicochemical properties of these catalysts can be characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm, and temperature-programmed desorption of ammonia (NH3-TPD). The 10Mn/Zr400-PILM(300) catalyst had the highest NOx conversion under excess oxygen conditions (15 vol% oxygen) and reached 91.8% NOx conversion at 200 °C. It was found that when the loading of manganese was 10 wt.%, the catalyst had the highest catalytic activity and the manganese-active component was highly dispersed on the Zr-PILM surface. The optimal calcination temperature of the Zr-PILM was 400 °C because the catalyst pore size was concentrated at 1.92 nm and the catalyst had the most acidic sites. And the optimum calcination temperature of the catalyst was 300 °C. This was because excessive calcination temperature promoted the manganese oxide polymerization and reduced the catalytic activity of the catalyst. [ABSTRACT FROM AUTHOR]

A series of Zr-Fe (Zr/Fe = 4:0, 3:1, 2:2, 1:3, 0:4) polymeric pillared interlayered montmorillonite loading 10 wt.% MnOx (Mn/Zr-Fe-PILM) were investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) in metallurgical sintering flue gas. The X-ray diffraction (XRD), N2 adsorption-desorption isotherm, scanning electron microscope (SEM), and ammonia temperature-programmed desorption (NH3-TPD) were used to analyze the physicochemical property. The Fe polymerized with Zr exchanged to montmorillonite can improve the Mn/Zr-Fe-PILM low-temperature NOx conversion and N2 selectivity. The Mn/Zr-Fe-PILM (1:3) shows the highest NOx conversion between 140 and 180 °C. The XRD results suggest that the growth of crystalline ZrO2 phase is intensely restrained for the Fe2O3 migration into the ZrO2 lattice. The ZrO2 and MnOx have an excellent dispersion in montmorillonite. The N2 adsorption result illustrates that the increase of Fe molar content in the Zr-Fe-PILM support increases the catalyst-specific surface area. The NH3-TPD results elucidate that the Mn/Zr-Fe-PILM (1:3) has the most total acid sites. Therefore, the low-temperature catalytic activity of the Mn/Zr-Fe-PILM (1:3) has been assigned to the large specific surface area, abundant acid sites, and the dispersion of metallic oxides. [ABSTRACT FROM AUTHOR]

In this study, a series of electro-osmosis experiments were conducted using Dalian marine soil to evaluate the water content and shear strength of soil samples after electro-osmosis experimental treatment. The conditions that were considered in these experiments include voltage, preloading pressure, drainage direction, temperature, anode material, and processing duration. In comparing water content and shear strength, the different operational conditions were demonstrated to affect the results of electro-osmosis to a variable extent. For example, the shear strength of samples at 35°C improved by an average of 61.96% compared with room temperature samples. Also, water content under 12 V trials decreased by an average of 9.30% compared with 6 V. These results can be attributed to the difference in electro-dewatering capacities of the conditions mentioned above. Based on the data, two statistical relationships, which represent the relationship between experimental conditions and results, were also established. [ABSTRACT FROM PUBLISHER]

One-dimensional laboratory electro-osmosis experiments of marine sludge in Dalian (China) were conducted on a self-made apparatus to research consolidation effects of copper, aluminum, and ferrum electrodes. Although there was potential loss in the contacts of the anode and marine sludge, the electro-osmosis method was still found to be an effective way to reduce the moisture content and increase the shear strength of marine sludge. In particular, ferrum electrodes performed the best for Dalian coastal marine sludge. The bad performance of copper anode can be justified by the generation of non-conductive paratacamite, atacamite, and nantokite on its surface. Overall, these new discoveries can benefit the choice of electrodes in the marine sludge electro-osmosis dewatering application. [ABSTRACT FROM PUBLISHER]