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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]

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]

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]

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 work, Sm-doped manganese supported Zr-Fe polymeric pillared interlayered montmorillonites (Mn/ZrFe-PILMs) were prepared for the low-temperature selective catalytic reduction (SCR) of NO x with NH 3 in metallurgical sintering flue gas. These pillared interlayered montmorillonite catalysts were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, nitrogen adsorption-desorption isotherm, ammonia temperature-programmed desorption, and hydrogen temperature-programmed reduction to study the influence of Sm doping on the SCR performance. The ZrFe-PILMs with a Mn/Sm molar ratio of 18 : 2 showed the excellent SCR activity among these catalysts, where a 95.5% NO x conversion ratio at 200 °C at a space velocity of 20 000 h -1 was obtained. Samarium oxide and manganese oxides were highly dispersed on the ZrFe-PILMs with different Mn/Sm molar ratios by the XRD results and SEM-EDS results. Meanwhile, the Mn-Sm/ZrFe-PILM (18 : 2) had the lowest temperature hydrogen reduction peak by H 2 -TPR results, which indicated that it had the lowest active bond energy on its surface. And the NH 3 -TPD results expressed that the Mn-Sm/ZrFe-PILM (18 : 2) had the most acidic sites, especially the weakly acidic sites. Therefore, it was found that the introduction of a small amount of Sm (Mn : Sm = 18 : 2) to Mn/ZrFe-PILM can significantly improve catalytic activity by the increased active oxygen component and the surface acidity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)