Dry Air Conditions Research Articles

The auto-oxidation characteristic of coal at different stages of the low-temperature oxidation process

The spontaneous combustion in the mining gob are often caused by the low-temperature oxidation of coal, and the low-temperature oxidation process has a long process leading to different characteristics in each stage, which brings great difficulties to the prevention and control of coal spontaneous combustion in the underground mining gob. Therefore, this article investigated the oxidation characteristics of coal at different stages of the low-temperature oxidation, mainly including: analyzing the changes in radical concentration and g factor based on electron spin resonance (ESR) experiments, studying the variations in coal temperature by using the programmed temperature controller and analyzing the characteristics of gas products and oxygen consumption by using the gas chromatograph. And the degree of auto-oxidation of coal was characterized by the difference between dry air and nitrogen conditions during the constant temperature period. The results showed that when the constant temperature reached 130 ℃, the coal began to exhibit auto-oxidation characteristics, while when the constant temperature reached 180 ℃, the auto-oxidation phenomenon of the coal significantly intensified, the types and content of radicals rapidly grew, the coal temperature significantly rose, and the oxygen consumption rapidly increased, while releasing a large amount of CO and CO2. And the relationship between the spontaneous oxidation ability of coal radicals and the temperature change of coal during constant temperature was obtained. The conclusions obtained provide theoretical guidance for the safety and clean production of coal resources in mines, as well as the prevention and control of coal spontaneous combustion fires.

Long-term phase composition and microstructure characteristics of phosphoric acid modified magnesium oxychloride cement exposed to natural environment

Magnesium oxychloride cement (MOC) is widely used as fireproof materials, decorative materials, and adsorption materials, etc. However, its poor water resistance limits the engineering application as a building material. The existing researches mainly focus on improving the short-term durability and water resistance, but few focus on long-term durability of MOC. In this paper, phosphoric acid-modified MOC samples with an age of 2–16 years from China and the Netherlands were collected. Their phase composition and microstructure characteristics were studied, which is of practical engineering significance for the modification of MOC. The results indicate that MOC modified by phosphoric acid would be decomposed and carbonated, and water in the ambient where MOC exposed to is the main factor. MOC exposed to humid environment presents a loose and porous morphology, but shows dense matrix with drying shrinkage cracks in dry air condition. MOC exposed to the air shows good carbon capture ability. The carbonated wood-MOC shows lower porosity than fresh wood-MOC paste. Carbonation phase on the surface of MOC products is beneficial to the internal structure and stability of MOC matrix. Besides, MOC is an environmentally friendly material. The manufacture of MOC requires less energy compared to ordinary Portland cement and shows good carbon neutralization potential under service life.

Oxidation behaviour of uncoated and PDC-SiAlOC glass-coated TiAl at 750 °C in dry and humid air

In this work polymer derived ceramic (PDC) coatings, based on SiAlOC glasses, were successfully applied on 48-2-2 TiAl alloy samples. These coatings showed a significant improvement in oxidation resistance in both dry and humid air conditions. The uncoated 48-2-2 TiAl alloy material showed poor oxidation resistance independent of the atmosphere. SEM, EPMA and Raman confocal imaging were used to investigate the oxidation mechanisms of the uncoated and coated 48-2-2 TiAl alloy in dry and humid air. The coating suppressed outward Ti diffusion and promoted alumina scale formation.

Facile construction of new coronal-like MnCeOx hollow nanosphere for efficiently removing o-dichlorobenzene

Designing unique and ingenious microstructure or morphology of catalysts is critical and still a challenge to obtain high catalytic performance in catalytic combustion reactions under dry air and 5.0 vol% H2O conditions, especially by economic and efficient measures. In pursuit of this goal, a facile strategy was exploited to accurately construct new-coronal like MnCeOx hollow microsphere with different Ce contents. This unique structure can expose more active sites and has excellent redox ability. The simulation results of generalized gradient approximation (GGA) of density functional theory (DFT) indicated that the introduction of a certain amount of Ce can effectively improve the adsorption and activation of o-DCB molecules on Mn3O4. The detailed study showed that the Mn2Ce1Ox hollow nanosphere exhibited excellent catalytic performance in the presence of 5.0 vol% H2O. Ideally, the action of Marse-van Krevelen (Mvk) combine Langmuir-Hinshelwood (L-H) mechanism was deduced based on the origin of oxygen species under dry air conditions. In general, the green and facile synthetic strategy provides a new idea for the design of hollow microsphere Mn-based catalyst and the unique structure significantly improves the comprehensive performance of o-DCB catalytic oxidation, which brings great hope for industrial application.

Polyphenols and Antioxidant Activity of Thunbergia laurifolia Infused Tea under Drying Conditions

Thunbergia laurifolia leaf is used in Thai herbal medicine to moderate alcohol, food poisoning, and other health-related diseases mainly due to its overwhelming phytochemical compounds which exert several biological functions such as antioxidant, and anti-inflammatory properties, among others. This study investigated the potential effects of hot air-drying conditions (TL-D80°C, TL-D90°C, and TL -D100°C) of T. laurifolia tea leaves on phenolic compounds, total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activities (AOA) of the infused teas. The results show that an increase in drying temperature significantly p < 0.05 improved TPC (709.7 ± 1.36–744.8 ± 5.79 mg GAE/) and TFC (198.98 ± 7.59–207.16 ± 4.10 mg RE/L) of infused teas. TL-D80°C (69.9 ± 0.95%) and TL-D90°C (69.3 ± 0.7%) infused teas showed significantly p < 0.05 higher DPPH inhibitory effect compared to TL-D100°C. Treatment had no effects p > 0.05 on ABTS.+ scavenging activity. The phenolic compounds detected in infused teas were rosmarinic acid, caffeic acid, gallic acid, catechin, rutin, and quercetin. Regarding, the cumulative phenolic compounds TL-D100°C infused teas were significantly higher p < 0.05 compared to TL-D90°C and TL-D80°C. The results suggest that drying conditions (i.e., TL-D100°C within 30 min) could be used to achieve appropriate moisture content of T. laurifolia tea leaves without compromising the phytochemical compositions and antioxidant potentials of the resulting infused teas.

Influence of Air-Drying Conditions on Quality, Bioactive Composition and Sensorial Attributes of Sweet Potato Chips.

The drying process is an essential thermal process for preserving vegetables and can be used in developing dried products as healthy alternative snacks. The effects of air-drying conditions using a convection dryer with hot air at different temperatures (60°, 65°, 70°, 75°, and 80 °C, in the range 5-200 min, at a fixed air speed of 2.3 m/s) were tested on the quality of slices (2.0 ± 0.1 mm) of dried sweet potato (Bellevue PBR). For each time and temperature, drying condition, physicochemical parameters (moisture content, CIELab color, texture parameters, total phenolic and carotenoid contents) and a sensory evaluation by a panel at the last drying period (200 min) were assessed. Drying time was shown to have a more significant effect than temperature on the quality of dried sweet potato as a snack, except for carotenoid content. Given the raw tuber content, thermal degradation (p < 0.05) of total phenolic compounds (about 70%), regardless of tested conditions, contrasted with the higher stability of total carotenoids (<30%). The dried product, under optimal conditions (≥75 °C for 200 min), achieved a moisture content (≤10%) suitable for preservation, providing a crispy texture with favourable sensory acceptance and providing a carotenoid content similar to the raw product.

A pre-oxidation scheme based on the evolution difference of oxides on the surface of high-chromium steel under different heating conditions

In this paper, the oxidation process of high-chromium steel under different heating conditions in dry air is analyzed. The results show that there is a special "weight gain platform" in the oxidation kinetics curve of high-chromium steel. During the isothermal oxidation process, Fe oxides will preferentially grow near the carbide grain boundaries and ultimately diffuse to the surface of the high-chromium steel. In addition, during oxidation, No oxide is formed near the carbide grain boundaries. Based on these results, a pre-oxidation scheme was proposed and shown to improve the oxidation resistance of high-chromium steel by 40% in water cycle oxidation.

Investigation of microscopic creep and shrinkage deformations of cement paste assisted by digital image correlation technique

New in-situ microscopic mechanical tests in Environmental SEM (ESEM) and climatic chamber (CC), assisted by Digital Image Correlation (DIC) technique, have been developed. The developed testing frameworks speed up the drying duration at least 200 times compared to classical test methods. We mitigate the risk of cracking to focus on the intrinsic drying creep and shrinkage. Free drying shrinkage is assessed at a micro-scale and exhibits a high correlation with the mass loss for relative humidity above 60% relative humidity (RH). We observe a water cavitation effect between 50–60% (RH). Although the drying conditions in ESEM occur at low pressure compared to ambient air-drying conditions in a climatic chamber, the shrinkage deformations at equilibrium at 20% RH are quite the same. The evolution of desiccation creep with drying shrinkage is bilinear in uniaxial and linear under biaxial compression. The drying creep Poisson’s ratio is negative, between −0.1 and 0.

Effect of the drying air conditions on the drying rate and milling quality of a long-grain rice variety

This work aims to study the effect of different drying air conditions on the drying rate and milling quality of a Uruguayan long-grain rice variety. It was observed that increasing the drying air temperature or lowering the drying air relative humidity decreased the milling quality. At temperatures above glass transition, this effect was greater. However, it was possible to dry the rice at a drying rate of up to 3 percentage points of moisture per hour (on a dry basis) maintaining a high milling quality. This was achieved when a 1-hour tempering was performed after drying. At higher drying rates, the milling quality decreased sharply even when tempering was performed. These results aim to contribute to the understanding of the drying process, allowing its optimization by increasing the drying rate without losing milling quality.

Energy analysis of the convective drying of iron ore fines

Drying operations in iron ore processing plants have a particularly high energy demand due to the massive solid flow rates employed in this industry. A 33 full-factorial design was applied to investigate the effects of air temperature, airflow velocity, and solids load on the drying time and the specific energy consumption (SEC) of the convective drying of iron ore fines in a fixed bed. The results demonstrated that each drying air condition was associated with an optimal solids load that minimized the SEC. A load of 73 g (bed height of about 0.8 cm) was identified and validated as the optimal condition in terms of energy consumption for the configuration with the highest air temperature (90?C) and airflow velocity (4.5 m/s). This condition resulted in a drying time of 29.0 s and a corresponding SEC of 12.8 MJ/kg to reduce the moisture from 0.11 kg water/kg dry solids to a target of 0.05 kg water/kg dry solids. Identifying the optimum values for the process variables should assist in designing and operating energy-efficient convective dryers for iron ore fines.

Towards an atomic scale understanding of the early-stage deterioration mechanism of LSCF

The early-stage degradation behaviour of a porous lanthanum strontium cobalt ferrite (LSCF) cathode in a solid oxide fuel cell is investigated at a low temperature of 600 °C by operating in dry air and wet air conditions with and without bias.

Development of a microsampler suitable for aerial collection of aerosol particles

A microsampler for collecting aerosol particles on an unmanned aerial system (UAS) was designed and evaluated in the laboratory for dry (no condensed water) and wet (foggy, misty, or rainy) air conditions.

Synthesis, Hirshfeld surface analysis, computational, wave function properties, anticancer and cytotoxicity activity of di[(p-chlorobenzyl) (dibromo)] (4,7-dimethyl-1,10-phenanthroline)tin (IV) complex

The complex di[(p-chlorobenzyl) (dibromo)] (4,7-dimethyl-1,10-phenanthroline)tin (IV) (SA1), were synthesized by reacting the 4,7-dimethyl-1,10-phenanthroline with the selected di[(p-chlorobenzyl) (dibromide) in methanol at the right mole ratio. The complex SA1, while environmental conditions in dry air, are quite stable in moist air and can be dissolved in a wide variety of organic solvents. Spectral, structural, theoretical, and biological analyses all looked into the products, and they all strongly supported up the expected molecular structures for complex formation. The compoundmolecular structure and geometry were defined using DFT and X-ray analysis. Topological studies, like ELF, LOL, ALIE, and RDG studies, were done with the Multiwfn-3.8 to find the main binding areas and weak interactions in the molecule. The HOMO-LUMO, MEP, and NLO properties were carried out in the gas phase. The complex SA1 study the anticancer and cytotoxicity activity using the HeLa and Vera cell lines. On the HeLa cell lines, the experiment findings demonstrated that the complex SA1 exhibited a higher level of activity than the standard treatment, cisplatin.

Adsorption removal of styrene on C–Cl grafted silica gel adsorbents

The heat desorption of styrene from adsorbents is impracticable owing to its spontaneous polymerization under heating conditions. However, the feature also brings a potential promoting effect on styrene adsorption. Therefore, it is expected to develop the non-regenerative adsorbents with large adsorption capacity by strengthening the polymerization effect. In this work, C–Cl grafted silica gel adsorbents were prepared by introducing (Chloromethyl)dimethylchlorosilane (CMDMCS) and FeCl2 into silica gel. The C–Cl grafted silica gel exhibited excellent styrene adsorption performance, its adsorption amounts for styrene were 4.67 times and 9 times of unmodified silica gel under dry air condition and high humidity condition (RH = 80%), respectively. In addition, the adsorption of styrene on C–Cl grafted silica gel was almost unaffected by the presence of toluene. The characterization of adsorbents after styrene adsorption indicated that the improvement of adsorption capacity of C–Cl grafted silica gel for styrene can be attributed to atom transfer radical polymerization (ATRP) of styrene molecules on modified silica gel during adsorption process.

Behavioural hydroregulation protects against acute effects of drought in a dry-skinned ectotherm.

During extreme climate events, behavioural thermoregulation may buffer ectotherms from thermal stress and overheating. However, heatwaves are also combined with dry spells and limited water availability, and how much individuals can behaviourally mitigate dehydration risks through microclimate selection remains largely unknown. Herein, we investigated the behavioural and physiological responses to changes in air and microhabitat humidity in a terrestrial ectotherm, the asp viper (Vipera aspis). We exposed individuals to a simulated heatwave together with water deprivation for 3weeks, and manipulated air water vapour density (wet air vs. dry air) and microclimate (wet shelter vs. dry shelter) in a two-by-two factorial design. Dry air conditions led to substantial physiological dehydration and muscle wasting. Vipers exposed to dry air usedmore often a shelter thatoffered a moist microclimate, which reduced dehydration and muscle wasting at the individual level. These results provide the first experimental evidence that active behavioural hydroregulation can mitigate specific physiological stress responses caused by a dry spell in an ectotherm. Future studies investigating organismal responses to climate change should consider moisture gradient in the habitat and integrate both hydroregulation and thermoregulation behaviours.

Study of Linear Deformation Changes in Heavy Concrete Based on Modified Portland Cement

The investigation results revealed how modified standard Portland cement of grade 42,5 (M400) with 10% of the expanding additive changes the deformation characteristics of heavy concrete. Heavy concrete of class B 22.5 (M300) with a different water-cement ratio (slump 3 cm and 5 cm) was selected as the object of study, from which cubic specimens of side 10 cm were prepared. The impact of modified cement on concrete linear deformations is determined at the ages of 1, 3, and 28 days under normal setting conditions, and changes in the sizes of the same specimens are checked for three months under air-drying conditions. The study confirmed that the most effective impact of modified cement, as in the case of construction mortars, is also observed in 3–7 days of curing. It was found that the effect of modified cement is increased with the increase in the water-cement ratio, and a relatively low percentage of expansion through the low water-cement ratio is explained by the certain rigidity of the concrete internal structure.

Designing CuO–SiO2 and Cu0–SiO2 Monolithic Ceramics Bearing Hierarchical Porosity Toward Robust and Cycling CO Oxidation Properties

In the general context of environmental air remediation, copper-oxide-based self-standing porous catalysts (MUB-103(x)) and their reduced homologues (Red MUB-103(x)) have been synthesized and studied for the thermoconversion of CO to CO2. Catalytic experiments under dry air conditions reveal that for nonreduced catalysts, increasing the Cu content diminishes the light-off temperature T50 (corresponding to 50% conversion). The catalytic performances exhibited by the CuO phase dispersed in the silica pores of MUB-103(x) samples are the highest reached to date despite the limitations of the experimental conditions used. After reduction with H2, the native Red MUB-103(x) catalysts offer CO conversion efficiencies significantly more increased, leading to a lowering of the T50 values equal to at least 100°C. As such, the CO conversion reaches a T50 value of 160 °C for Red MUB-103(2) with 1.81 wt % Cu; this catalyst displays a specific rate of 8.6 mmolCO gCu–1 s–1 at 175 °C, largely higher than those observed to date. The performances of the Red MUB-103(2) sample were evaluated for CO oxidation under humid conditions with the addition of 5 vol % water vapor in the feed during four cycles, leading to the same efficiency when compared with that under dry experimental conditions, revealing robustness. A drastic increase in the CO conversion temperature was observed for the 4th cycle, i.e., after 8 h under humid conditions. Analyses of the spent Red MUB-103(2) catalyst after four cycles reveal a slight oxidation of copper, leading to Cu2O species. Importantly, after four cycles, the deactivated catalyst was able to partially recover its performance when reactivated through a 2 h reducing treatment under H2 at 400 °C.

Analysis of the Quality Characteristics of Napa Cabbage and Lettuce according to Hot Air Drying Conditions

Analysis of the Quality Characteristics of Napa Cabbage and Lettuce according to Hot Air Drying Conditions

Numerical analysis on burning and particle formation of a single ethanol-based droplet in flame spray pyrolysis

Ethanol is a common inexpensive solvent for industrial flame spray pyrolysis. This work presents a numerical study of a single ethanol-based droplet burning with different precursor concentrations under both dry and wet air conditions. The evaporation and decomposition of precursors, the deposition of water vapor and its diffusion and transport in the liquid phase are considered. The micro-explosion behavior and droplet burning constant were well predicted as compared to existing experimental data in literature. The results show that surface condensation, dissolution, and re-evaporation of water were controlled by the disparity of mass transfer and evaporation priorities of different components in the droplet at different temperatures. Water in the ethanol droplet increases first during the initial burning stage and then decreases with increasing temperature as water preferentially vaporized than the formed less-volatile viscous layer on the droplet surface during the droplet combustion. The ratio of particle synthesis through evaporation and thermal decomposition decreases with increasing precursor concentration. It is further identified that the presence of water from either combustion products or humid air suppresses evaporation of the precursors in ethanol droplets because water dissolved in droplets evaporates preferably than the precursor, thereby potentially inhibiting the gas-to-particle route and providing another potential option for the control of flame synthesis process.

Temporal heterogeneity in photosystem II photochemistry in Artemisia ordosica under a fluctuating desert environment.

Acclimation strategies in xerophytic plants to stressed environmental conditions vary with temporal scales. Our understanding of environmentally-induced variation in photosystem II (PSII) processes as a function of temporal scales is limited, as most studies have thus far been based on short-term, laboratory-controlled experiments. In a study of PSII processes, we acquired near-continuous, field-based measurements of PSII-energy partitioning in a dominant desert-shrub species, namely Artemisia ordosica, over a six-year period from 2012-2017. Continuous-wavelet transformation (CWT) and wavelet coherence analyses (WTC) were employed to examine the role of environmental variables in controlling the variation in the three main PSII-energy allocation pathways, i.e., photochemical efficiency and regulated and non-regulated thermal dissipation, i.e., Φ PSII, Φ NPQ, and Φ NO, respectively, across a time-frequency domain from hours to years. Convergent cross mapping (CCM) was subsequently used to isolate cause-and-effect interactions in PSII-energy partitioning response. The CWT method revealed that the three PSII-energy allocation pathways all had distinct daily periodicities, oscillating abruptly at intermediate timescales from days to weeks. On a diurnal scale, WTC revealed that all three pathways were influenced by photosynthetically active radiation (PAR), air temperature (T a), and vapor pressure deficit (VPD). By comparing associated time lags for the three forms of energy partitioning at diurnal scales, revealed that the sensitivity of response was more acutely influenced by PAR, declining thereafter with the other environmental variables, such that the order of influence was greatest for T a, followed by VPD, and then soil water content (SWC). PSII-energy partitioning on a seasonal scale, in contrast, displayed greater variability among the different environmental variables, e.g., Φ PSII and Φ NO being more predisposed to changes in T a, and Φ NPQ to changes in VPD. CCM confirmed the causal relationship between pairings of PSII-energy allocation pathways, according to shrub phenology. A. ordosica is shown to have an innate ability to (i) repair damaged PSII-photochemical apparatus (maximum quantum yield of PSII photochemistry, with F v/F m > 0.78), and (ii) acclimatize to excessive PAR, dry-air conditions, and prolonged drought. A. ordosica is relatively sensitive to extreme temperature and exhibits photoinhibition.