Process Safety and Environmental Protection最新文献

As a result of human underground mining activities, phyllite has been extensively reused to make raw ceramic materials and concrete aggregates. Building materials are a significant source of indoor radon, and radon gas emitted from phyllite poses radiation risks to humans. High temperatures can alter the structural properties of rocks, impacting radon exhalation. Thus, this study examined phyllite's radon exhalation rate after heat treatment ranging from 25 °C to 1000 °C. The effects of changes in pore structure and mineral composition on phyllite's radon exhalation were analyzed in detail using nuclear magnetic resonance (NMR), polarizing optical microscopy (POM), three-dimensional microscopy (3DM), and scanning electron microscopy (SEM). Results indicate that the radon exhalation rate initially increases and then decreases with rising temperature. This rate correlates positively with both total porosity and micropore porosity. Processes such as free water evaporation, pyrite oxidation, quartz phase transformation, and chlorite dehydroxylation within phyllite contribute to pore development and the movement of free radon within pore spaces. The highest total porosity and radon exhalation rate occur at 700 °C, measuring 8.6 % and 6.14 Bq/m²·h, respectively—4.30 times and 1.18 times higher than at 25 °C. Additionally, mineral decomposition and melting reduce pore connectivity and effective porosity, hindering radon migration. These findings offer guidance for assessing radon radiation risks and indoor radon potential in phyllite-based building materials.

Plastic waste poses a significant environmental challenge due to its non-biodegradable nature and accumulation in landfills. Converting plastic waste into usable fuel could offer a promising solution for mitigating these issues while addressing the emission-related challenges of diesel engines. This study investigates the impact of plastic waste oil (WPO) obtained through pretreatment and catalytic pyrolysis, blended with acetone-butanol-ethanol (ABE) and diesel fuel, on diesel engine. The aim was to evaluate how these blends affect gaseous emissions, organic compounds, and particle-bound carbon, focusing on their potential to reduce harmful pollutants compared to pure diesel fuel. The results indicated that the ABE5W15D blend significantly reduced smoke and CO emissions by 35.7 % and 17.43 %, respectively, with a slight decrease in HC emissions. However, the ABE20W blend showed elevated NOx levels due to higher ignition delay and increased cylinder pressure. Compared to pure diesel (D100), ABE10W10D and ABE5W15D blends reduced total polycyclic aromatic hydrocarbons (PAHs) emissions by 26.8 % and 37.4 %, respectively. Naphthalene was the dominant PAH, remarkably increasing with W20D use, while longer-chain alkanes associated with lubricant oil had higher W20D emissions. The ABE5W15D blend notably reduced organic carbon (OC) emissions by approximately 38.26 % compared to D100. ABE20D exhibited lower elemental carbon (EC) emissions than D100, although it had higher EC than OC. The W20D blend resulted in larger particle diameters, whereas ABE10W10D showed lower particle counts in the 7–15 nm range. In conclusion, blending plastic waste oil with ABE and diesel fuel can effectively mitigate certain pollutants, depending on the blend composition.

The accidental release of cryogenic liquids can cause several hazards to humans, assets, and the environment. Therefore, this phenomenon has drawn significant attention and has been investigated as part of quantitative risk assessment associated with the use of cryogenic liquids. However, the effects of release conditions on pool spread have not been thoroughly studied, and the mechanism of pool retraction has not been discussed. In this study, an attempt was made to address these gaps by both experimental and numerical analyses. Firstly, large-scale-outdoor release tests with a systematic measurement system were performed using liquid nitrogen to compare with large-scale release tests of liquid hydrogen. The release height and orientation were varied. It was observed that the pool shape was affected by the release orientation. However, the maximum pool size and average vaporization rate were insensitive to both the release height and orientation. The conductive heat from the ground was confirmed to be the major heat source for pool vaporization, accounting for over 90 % of the total heat transferred into the liquid pool. Subsequently, release scenarios were simulated using integral source models. Especially, several hypotheses were thoroughly discussed, implemented in the source models, and validated against experimental results to determine the most appropriate mechanism for pool retraction. The findings of this study are expected to be beneficial for the consequence estimation of cryogenic release scenarios and for the validation and improvement of source models.

In the renewable energies scenario, biogas has several advantages, such as reducing greenhouse gas emissions, the possibility of decentralized production, and using a wide variety of substrates. Many operational factors significantly impact biogas production efficiency, and failure to ideally align them can lead to adverse situations in the production process. In this context, uncontrolled foam formation is one of these main negative factors. To obtain a better understanding of foam formation during biogas production, this article carried out a survey of the most likely causes. The most relevant factors found are the inefficient agitation system, the excess organic loading rate into the equipment, and the stress of the microbial community. In addition, ways of mitigating the formed foam were investigated, and this work provides effective guidelines to overcome this problem, such as maintaining the agitation efficiently, regulating temperature and pH within ideal ranges, and controlling the microbial community with the application of antifoams being the most relevant action. Therefore, understanding the mechanisms of foam formation and mitigation methods will help develop more efficient forms of industrial operation. Finally, future research directions were proposed for anaerobic digestion and foam formation.

The gradual depletion of mineral resources has led to the emergence of a new engineering challenge in the field of mineral processing: the effective treatment of low-grade ores. In this study, the low-grade titanium ore leaching solution was employed as the raw material. The extraction ability of a series of hydroxyl extractants for the most common metal iron in minerals was investigated. As a result, a new high-quality processing system for low-grade ore with branched-chain octanol as the core component was constructed. In the treatment of mineral leaching solution, branched-chain octanol has high selectivity and large capacity (111.7 g/L) for iron. It was capable of efficiently removing a significant quantity of iron ions in low-grade ores that were not anticipated to be present. By employing quantum chemical (QC) methodologies, the mechanism for the high selectivity of branched-chain octanol for Fe(Ⅲ) has been elucidated by analyzing the frontier molecular orbital (FMO) energy of acid salts of common metals in minerals. Combined with spectral analysis and slope method, the structure of the extracted complex was confirmed to be [n-R₈-OH]₂·H·FeCl₄. On the basis of system optimization, a three-stage countercurrent extraction and three-stage countercurrent stripping was employed to remove all the Fe(Ⅲ) in the mineral leaching solution. And after detecting, the purity of the obtained Fe(III) solution was greater than 99.5 %. In the treatment of low-grade minerals, especially those containing key metals, the branched-chain octanol extraction system demonstrates high selectivity and reliability, which is a effective means to improve the quality of mineral leaching solution.