SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Effect of ionic liquids on the microstructure and combustion performance of Shengli lignite

To ensure the safe transportation and efficient utilisation of lignite, it is important to inhibit its spontaneous combustion. In this study, Shengli lignite (SL+) was used as the research object and ionic liquids (ILs) were used to pretreat the lignite to investigate their effect on the combustion performance of lignite. On this basis, the relationship between the structure and combustion performance of lignite with different structures (heat treatment, oxidation) after ILs treatment was investigated. Results indicated that the combustion of lignite treated with ILs shifted towards higher temperatures. The most pronounced effect was observed in coal samples treated with [BMIM]Cl (1-butyl-3-methylimidazolium chloride), with the maximum combustion rate corresponding to a temperature increase of approximately 57 °C compared to that of the untreated lignite. For the heat-treated lignite, the temperature corresponding to the maximum combustion rate was approximately 38 °C higher than that of the untreated lignite. After [BMIM]Cl treatment, the combustion performance of the heat-treated lignite changed very slightly. In contrast, for oxidised lignite, the temperature corresponding to the maximum combustion rate decreased by approximately 54 °C compared with that of the untreated lignite and increased by approximately 135 °C after treatment with [BMIM]Cl. The characterisation results show that the content of aliphatic hydrogen and oxygen-containing functional groups decreased in the heat-treated lignite, while the content of hydroxyl and carboxyl groups increased in the oxidised lignite. The microstructure of the heat-treated lignite after [BMIM]Cl treatment changed slightly. In contrast, in the oxidised lignite after [BMIM]Cl treatment, the content of hydroxyl and carboxyl groups decreased, whereas the content of ether (C-O-) structures increased. The increased content of ether (C-O-) structures improved the stability of the coal samples. It is believed that the inhibition of lignite combustion is mainly attributed to the high stability of the ether (C-O-) structures. The kinetic analysis demonstrated that the ILs treatment increased the activation energy of lignite combustion.

Comparative study on the inhibiting effect of dissolvable tiny-foam extinguishing agent and chlorine salts on coal spontaneous combustion

Coal spontaneous combustion (CSC) is a global disaster and detrimental to the ecological environment. This study aims to better apply environmentally friendly dissolvable tiny-foam extinguisher (DTE) to CSC and look further into the inhibition mechanism. Thermogravimetric analysis and differential scanning calorimetry (TG-DSC) were employed to test the oxidation properties of coal samples treated with DTE, NaCl, MgCl2, and CaCl2 inhibitors, and the reaction mechanisms and kinetic parameters in the high-temperature stage of coal oxidation were determined. The results revealed that the inhibition of the four inhibitors was similar in the initial period of the coal oxidation, DTE increased the cracking temperature of the coal by 37 °C, mass loss was a minimum when reaching the ignition temperature, and inhibition was better than the other inhibitors at the low temperature. DTE had higher thermal stability and played a stable role in suppression at the high temperature, while chlorine salt inhibitors promoted the oxidative exothermic reaction. DTE coal sample absorbed forty times more heat during the endothermic stage than raw coal, ten times more than MgCl2, and released a minimum of heat. In the decomposition and combustion stages, the reaction mechanism of coal and oxygen conformed to the three-dimensional diffusion Z.-L.-T. equation, and the apparent activation energy of the DTE-treated coal sample was about 40 kJ/mol higher than raw coal.

Experimental Study on Catalytic Action of Intrinsic Metals in Coal Spontaneous Combustion

In order to study the effect of inherent metals in coal on spontaneous combustion, Hongmiao lignite and Hongqingliang long-flame coal were demineralized by hydrochloric acid, the raw coal and demineralized coal were characterized by Fourier transform infrared spectrometry, X-ray diffraction, and synchronous thermal analysis experiments, and the corresponding ash content was detected by inductively coupled plasma mass spectrometry. The results show that the effect of demineralization on the volatile matter of low-rank coal is small, and the change of crystallite structure is not significant. The removed parts are mainly water-soluble salts and soluble minerals, such as carbonates and metal ions, that are not tightly bound to the organic matter of coal structure. The removed metal elements are mainly alkali metals Na and K, alkaline earth metals Ca, Mg, Sr, and Ba, and transition metals Fe, Mn, Ti, and so forth. The temperatures corresponding to the end of weight loss, ignition, and maximum weight loss rates were elevated on the thermogravimetric curves of the demineralized coal samples. The heat absorbed by evaporation of water in coal and the heat released by oxidation and combustion of coal are decreased to different degrees, indicating that the spontaneous combustion tendency of coal after demineralization is reduced, and alkali metal, alkaline earth metals, and transition metals in coal have a catalytic effect on spontaneous combustion of coal. After adding the metal chelating agent ethylenediaminetetraacetic acid (EDTA), the apparent activation energy decreased by 33.08 and 2.42%, respectively. EDTA and the alkali metal, alkaline earth metal, or transition-metal ions formed a stable chelate in coal. The catalytic activity of metals is weakened or even lost, thereby inhibiting spontaneous combustion of coal, and verifying the catalytic effect of internal metals in coal on the spontaneous combustion of coal.

Influence of High Sulfate Mine Water on Spontaneous Combustion of Coal

Mine water cannot be discharged until it has been treated, which increases the cost of mining and causes environmental damage. This paper attempted to use sulfate mine water as a flame retardant material for the treatment of coal spontaneous combustion (CSC) in underground mines. The temperature-programed experimental device and gas chromatograph were used to simulate the low-temperature oxidation process of coal. Infrared spectroscopy was used to study the influence and inhibition mechanism of mine water and chloride inhibitor on active functional groups. It was found that although the sulfate mine water inhibited the formation of -OH, it accelerated the cleavage of the aromatic ring. The thermogravimetric experiment was used to analyze the ignition temperature and activation energy of different coal samples. It was found that mine water had an obvious effect on inhibiting CSC in the combustion stage, which could increase the oxidation temperature of coal.

Experimental and Quantum Chemical Study on the Inhibition Characteristics of Glutathione to Coal Oxidation at Low Temperature

In response to the frequent occurrence of coal spontaneous combustion accidents, this paper proposes to use glutathione (GSH) as an inhibitor to inhibit the coal oxidation at low temperature. Based on the gas production of oxidation, thermogravimetric analysis, electron spin resonance, and in situ Fourier infrared transform spectroscopy experiments, it is known that GSH has a good inhibiting effect on lignite, long-flame coal, and fatty coal. The optimal action temperature of GSH is 60-150 °C, which can effectively slow down the weight loss and exothermic process and reduce the gas production of CO and CO₂. Compared with the raw coal, the GSH-treated coal samples possess higher crossing point temperature and lower reactive group content. Subsequently, quantum chemical calculations are performed using density functional theory. The results demonstrate that the inhibiting mechanism of GSH is inerting the reactive radicals in coal and converting them into more stable compounds. Meanwhile, the activation energy of the reaction between GSH and each reactive radical is small, and all of them can occur at room temperature and pressure. This study lays the groundwork for future development of inhibitors.

Importance-Based Key Basic Event Identification and Evolution Mechanism Investigation of Hydraulic Support Failure to Protect Employee Health

Background: Although hydraulic support can help enterprises in their production activities, it can also cause fatal accidents. Methods: This study established a composite risk-assessment method for hydraulic support failure in the mining industry. The key basic event of hydraulic support failure was identified based on fault tree analysis and gray relational analysis, and the evolution mechanism of hydraulic support failure was investigated based on chaos theory, a synthetic theory model, and cause-and-effect-layer-of-protection analysis (LOPA). Results: After the basic events of hydraulic support failure are identified based on fault tree analysis, structure importance (SI), probability importance (PI), critical importance (CI), and Fussell–Vesely importance (FVI) can be calculated. In this study, we proposed the Fussell–Vesely–Xu importance (FVXI) to reflect the comprehensive impact of basic event occurrence and nonoccurrence on the occurrence probability of the top event. Gray relational analysis was introduced to determine the integrated importance (II) of basic events and identify the key basic events. According to chaos theory, hydraulic support failure is the result of cross-coupling and infinite amplification of faults in the employee, object, environment, and management subsystems, and the evolutionary process has an obvious butterfly effect and inherent randomness. With the help of the synthetic theory model, we investigated the social and organizational factors that may lead to hydraulic support failure. The key basic event, jack leakage, was analyzed in depth based on cause-and-effect-LOPA, and corresponding independent protection layers (IPLs) were identified to prevent jack leakage. Implications: The implications of these findings with respect to hydraulic support failure can be regarded as the foundation for accident prevention in practice.