The effects of phosphorus-free inhibitors on the ignition of lycopodium dust

The minimum ignition temperature of dust suspension (MIT) and the hot surface ignition temperature of the dust layer (LIT) are essential safety parameters for the process industry. However, the knowledge of the ignition behavior when solid mixtures of flammable fuels and phosphorous-free inhibitors are considered is still scarce and further experimental and theoretical analyses are requested. In this work, the ignition temperature of phosphorous-free inhibitors (coal fly ash and calcium carbonate) mixed with lycopodium dust have been studied in terms of LIT analysis (hot plate thickness: 5 mm, 12.5 mm and 15 mm), and by the Godbert-Greenwald test for the MIT. Both coal fly ash and calcium carbonate have been tested at different concentrations and particle sizes.Results show that the effects of the inhibitor can be counter-productive when layer ignition temperature is considered even if the minimum ignition temperature of the dust suspension shows a positive effect from the safety point of view. This behavior has been analyzed in the terms of thermal conductivity and diffusivity of the mixture, by using Maxwell's equation for two-phase solid mixtures. Standard empirical correlations for the ignition temperature of solid mixtures have been also tested, showing their weakness in reproducing mixture behavior.     

High efficiency of the NH4H2PO4/Mg(OH)2 composite for guaranteeing safety of wood production

Currently, China's timber industry is in high demand with the development of real estate. However, there is a certain fire hazard in the production process of wood manufacturing. Once a fire occurs, the fire is violent and the spread is rapid. Therefore, to improve the safety of its production process, ammonium dihydrogen phosphate and magnesium hydroxide were selected to prepare a new composite superfine dry powder, which was denoted as the NH₄H₂PO₄/Mg(OH)₂ composite. Furthermore, to figure out dry powders' extinction effect on Class A fire, the wood-crib fire suppression effect of the NH₄H₂PO₄/Mg(OH)₂ composite was test, and then compared with that of ultrafine dry powder (UDP) and commercial ABC dry powder (C-ABC) in a 1 m³ chamber. Three parameters of the fire extinguishing process, namely flame extinction time, powder consumption and temperature drop were adopted to measure the fire suppression performance. The results demonstrated that UDP and C-ABC both had a larger flame extinction time and powder consumption than the NH₄H₂PO₄/Mg(OH)₂ composite. Besides, a fire (wood cribs) can be extinguished by the NH₄H₂PO₄/Mg(OH)₂ composite with the fastest temperature drop and a much-improved toxic gas suppression ability. In short, the NH₄H₂PO₄/Mg(OH)₂ composite can better guarantee the safety of the wood processing production process. Moreover, the reasons for performance advantages of the NH₄H₂PO₄/Mg(OH)₂ composite were discussed.     

球磨铝/聚四氟乙烯的热性能和失效研究

目的 研究高活性铝/聚四氟乙烯(Al/PTFE)含能材料在常温条件下的存贮能力.方法 采用高能球磨法,制备Al/PTFE复合物,对其进行温度加速老化试验.采用差热分析方法,研究该材料在不同老化时间段的放热性能,并对其失效时间进行评估.结果 球磨制备的样品组分间的反应模式为气固相反应.干法球磨制备得到的样品具有较高的放热量和较长的贮存寿命,放热量为1.82 kJ/g,在老化时间4 a以内的放热性能损失不超过20％.湿法球磨制备得到的样品具有很高的反应活性,放热量达到2.86 kJ/g,但是老化1 a后就发生明显失效.结论 以干法球磨的样品放热能力较低,但其能够在更长的时间内保持反应活性,更加适合于长期贮存.     

Concentrations and modes of occurrence of trace elements in the Late Permian coals from the Puan Coalfield, southwestern Guizhou, China

The concentration, mode of occurrence, and origin of trace elements in the Late Permian coals from the Puan Coalfield, southwestern Guizhou, China, were examined using inductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence (XRF), cold-vapor atomic absorption spectrometry (CV-AAS), ion-selective electrode method (ISE), sequential chemical extraction procedure (SCEP), scanning electron microscopy equipped with energy-dispersive X-ray (SEM-EDX), and optical microscope. Results show that minerals in the No. 2 Coal from the Puan Coalfield were mainly made up of epigenetic pyrite of low-temperature hydrothermal fluid origin and kaolinite of detrital terrigenous origin. Elements including As (36.9 μg/g), Cd (10.2 μg/g), Cr (167.3 μg/g), Cu (365.4 μg/g), Hg (2.82 μg/g), Mo (92.6 μg/g), Ni (82.6 μg/g), Pb (184.6 μg/g), Se (6.23 μg/g), Zn (242.3 μg/g), and U (132.7 μg/g) are significantly enriched in the No. 2 Coal from the Puan Coalfield. However, concentrations of trace elements in the other four coals, the No. 1, No. 8, No. 11, and No. 18 Coals, were close to the usual ranges found for Guizhou of China, China, and USA. Results of SEM-EDX and SCEP showed that As, Cd, Hg, Mo, Ni, Pb, and Zn occur mainly in veined pyrite, while Cr, Cu, and U distribute mainly in kaolinite, indicating that the low-temperature hydrothermal fluid and detrital materials of terrigenous origin are the main contributors to the enrichment of these trace elements in the No. 2 Coal.     

Factors associated with occupational injury severity in the New South Wales underground coal mining industry

The relationship between a large number of mine and mine worker characteristics and injury severity was examined using multiple regression techniques. The study was based on data extracted from the New South Wales (N.S.W.) Joint Coal Board's computer based accident/incident reporting system describing 21,372 non-fatal, lost-time injurious incidents that occurred in the N.S.W. underground coal mining industry during the 4 year period from 1 July 1986 to 30 June 1990. The number of days lost as a result of an injurious incident was the best available proxy measure of injury severity. Over the study period, the number of days lost per 100,000 tonnes of raw coal production declined by 73%. Over the same period, injurious incidents involving more than 20 days off work, which constituted only 16% of all injurious incidents in underground mines, resulted in 75% of the total days lost for the whole N.S.W. underground coal mining industry. Factors that had practical importance and that were significantly associated with injury severity included mine worker's age, part of the body injured, type of accident, agency of accident, and mine worker activity. Factors not important or not significant in their relationship with injury severity were: time into shift, previous hours worked, mine location of incident, occupation, work experience, frequency of task, shift, and mining region. This study suggests that factors related to the susceptibility of a mine worker's body tissue to damage or repair, and factors related to the concentration of energy on the mine worker by vehicle and environmental characteristics are important determinants of injury severity.     

从煤和瓦斯的耦合作用及煤的失稳破坏看突出的机理

以含瓦斯煤力学为基础，研究煤与瓦斯的耦合作用对煤和瓦斯突出的影响及突出发生的失稳机理，提出煤和瓦斯突出的固流耦合失稳理论，为煤和瓦斯突出的预测提供了理论基础     

Density functional and experimental study of NO/O2 on zigzag char

In this paper, quantum chemistry computation (density functional theory) of multi-air-staged combustion was investigated in combination with experiment. It was found that the presence of oxygen in the combustion environment has a great influence on the surface chemistry of coal char. In the reaction pathway, the ring-opening reaction happens first, and is followed by NO adsorption. Afterwards, the ring-closure reaction takes place, leaving the nitrogen atom trapped in the inner char molecule. This reaction route effectively inhibits NO formation and achieves the aim of controlling NO emissions. In the staged combustion experiments, the consumption of O₂/NO was accompanied by an increase in the CO₂ concentration. The quantum chemistry computation successfully interprets the recent experimental trends displayed in multi-air-staged combustion.     

水力空化对褐煤水煤浆流变特性影响的试验研究

介绍了水力空化作用机理,研究了水力空化作用对褐煤水煤浆粘度的影响,探讨了空化后浆体内存在气泡的形态及影响关系。试验结果表明:水力空化处理后的水煤浆浆体流动性变好,水煤浆的粘度特性已由假塑性流体变成了类似牛顿流体;速度梯度为100 s-1时的粘度指标由320 mPa·s提高到340 mPa·s,速度梯度为30 s-1时的粘度指标由420 mPa·s提高到850 mPa·s,30μm以下的细粒级含量明显高于空化前粒级的含量;水力空化作用在水煤浆中引入了大量不易消失的圆形微细气泡,气泡的占位作用提高了水煤浆粘度和稳定性,微细气泡的布朗运动破坏了颗粒之间的静电力吸附,圆形微细气泡成为水煤浆浆体流动过程中的润滑剂并改善水煤浆流变性能。     

论我国防治煤与瓦斯突出技术的发展方向

指出了我国在防治煤与瓦斯突出方面值得注意的问题,论述了突出矿井合理的采掘部署在防突中的重要作用,提出了把《四位一体》的综合防突措施发展为《五步配套》的综合防突体系;阐明了煤矿建设和生产各阶段的主要防突任务,并对完善防突预测预报体系提出了建议;强调了全面开展区域性预测预报技术的研究和加快发展利用声发射技术预测预报防突的重要意义。     

含滑石粉的环保型聚乙烯包装材料的可环境消纳性能研究

借助人工加速老化、自然土壤填埋等实验方法 ,采用力学性能测试、扫描电镜 (SEM)、热重 -红外联用仪 (TG IR)等测试方法 ,对所研制的含滑石粉的环保型聚乙烯 (PE)塑料包装材料的可环境消纳性能进行探讨。实验结果表明 ,以PE为主材料 ,添加不易分解的滑石粉、生物活性剂、FeSt3 MnSt2 复合光敏剂 ,研制出的高填充可降解的PE塑料薄膜 ,具有良好的光 -生物降解性能 ,且可适用于焚烧处理。