Experimental study on CO and CO2 emissions from spontaneous heating of coals at varying temperatures and O2 concentrations

Laboratory experiments were conducted to investigate carbon monoxide (CO) and carbon dioxide (CO₂) emissions from spontaneous heating of three U.S. coal samples in an isothermal oven at temperatures between 50 and 110 °C. The oxygen (O₂) concentration of an oxygen/nitrogen (N₂) mixture flowing through the coal sample was 3, 5, 10, 15, and 21%, respectively. The temperature at the center of the coal sample was continuously monitored, while the CO, CO₂, and O₂ concentrations of the exit gas were continuously measured. The results indicate that the CO and CO₂ concentrations and the CO/CO₂ ratio increased when the initial temperature was increased. As the inlet O₂ concentration increased, the CO and CO₂ concentrations increased, while the CO/CO₂ ratios tended to converge to the same value. The ratio of CO/CO₂ was found to be independent of coal properties, approaching a constant value of 0.2. The maximum CO production rate correlated well with the maximum coal temperature rise. The apparent order of reaction for coal oxidation was estimated to be between 0.52 and 0.72. The experimental results in this study could be used for early detection and evaluation of a spontaneous heating in underground coal mines.     

Fabricating data: how substituting values for nondetects can ruin results, and what can be done about it

The most commonly used method in environmental chemistry to deal with values below detection limits is to substitute a fraction of the detection limit for each nondetect. Two decades of research has shown that this fabrication of values produces poor estimates of statistics, and commonly obscures patterns and trends in the data. Papers using substitution may conclude that significant differences, correlations, and regression relationships do not exist, when in fact they do. The reverse may also be true. Fortunately, good alternative methods for dealing with nondetects already exist, and are summarized here with references to original sources. Substituting values for nondetects should be used rarely, and should generally be considered unacceptable in scientific research. There are better ways.     

污染物排放波动特征及对排污许可限值的影响

受生产活动变化的影响,企业的污染物排放具有一定的波动性,制定基于不同时间周期的污染物排污许可限值,是完善企业污染物排放监管的需要。以铁岭市企业在线监测数据为基础,采用短周期排放量与长周期排放量的比值β,研究了企业行业特征和规模对不同周期污染物排放量的影响。结果表明,行业对β值具有重要的影响,铁岭市屠宰行业、煤炭行业和污水处理厂COD日排放量与年排放量的比值β平均值分别为2.82、2.61和1.65,NH-N排放量Cr MDL 3的β平均值分别为2.9、3.49和2.59,表明污水处理厂相比屠宰行业和煤炭行业具有更强的稳定性。从企业规模来看,MDL企业规模较小时,由于生产稳定性差β值波动较大;企业规模较大时,β值趋于稳定。因此,制定不同周期的企业排污许可限值时,应基于不同的行业特征和企业规模给出不同的参考比值。     

Calculation of the minimum ecological water requirement of an urban river system and its deployment: A case study in Beijing central region

The minimum ecological water requirements of an urban river system and water deployment are key elements in integrated water resources planning and urban ecological construction. Based on a review of ecological water requirement calculation methods and considering the different ecological functions of an urban river system, the ecological function method was used in this paper to calculate the components of the ecological water requirements of an urban river. An envelope curve-based method was proposed for assessing the minimum ecological water requirements of an urban river system. Water resources deployment strategies designed to meet the minimum ecological water requirements were described. Then, the minimum ecological water requirements of the urban river system in Beijing central region, selected as a case study, were investigated. The key parameters for assessing the minimum ecological water requirement in the Beijing urban river system were determined. Based on the ecological objectives and the current status of the different urban river systems within the Beijing central region, the minimum ecological water requirements were calculated. Different types of water sources, including rainwater, upstream water, and reclaimed water, were deployed to meet the ecological water requirements for the urban river system in the Beijing central region.     

起重机电气安全保护(接地)技术存在的共性问题的分析

指出了起重机电气安全保护存在的问题 ,分析了其原因 ,提出了改进措施。     

A mathematical model for predicting the flash point of binary solutions

A mathematical model which may be used for predicting the flash point of binary solutions has been proposed and subsequently verified by experimentally-derived data, such data pertaining to an almost-ideal solution as also to highly non-ideal solutions. The results reveal that the model is able to precisely predict the flash point over the entire composition range of binary solutions for both ideal solutions and non-ideal solutions by way of utilizing the flash point of the individual components. The highly non-ideal solution like octane+ethanol exhibits the minimum flash-point behavior, which leads to the minimum on the flash point vs composition curve.     

环境中寄生虫(卵)的检测方法及回收率

环境中常见的寄生虫(卵)有蛔虫、肝吸虫、血吸虫、贾第鞭毛虫和隐孢子虫等,针对其特点已形成以虫卵密度、免疫和血清特性等为基础的检测方法,比较分析不同寄生虫不同检测方法的准确度、精确度、回收率差异及优缺性,为实际工作提供技术依据。     

Applications of intrinsic safety characteristic parameters of propellant dust: Commercial multi-tube pyrotechnic hazard assessment

Fireworks are widely used in festivals around the world, but the safety issue during preparation the manufacture, storage, and operation of pyrotechnics has also been highly valued. Human operation error and insufficient recognition of the safety characteristics of pyrotechnics are the main factors in pyrotechnic incidents in Taiwan. This study considers thermal and explosion safety by electrostatic sensitivity, minimum ignition temperature, and explosion characteristics of propellant dust in commercial multi-tube pyrotechnics. The results show that propellant dust is not sensitive to static electricity, but it was ignited at 260 °C environment temperature. The lower explosion limit of propellant dust was 125–150 g/m³, which provided an effective control of the dust concentration in the workplace. It was also found that the explosive level of the propellant dust belonged to St-1, which is exceptionally close to St-2 explosion influence, and that cannot be ignored. The high temperature associated with the explosion reminded that after the firework is launched, it should be cooled before leaving. Combining the above results, this research suggests the environmental operation temperature and dust concentration should be controlled within a safer range to effectively avoid the occurrence of dust fire or explosion and substantially enhance the safety of the pyrotechnic industry.     

日本二噁英检测及分解技术的发展

日本作为对二噁英的研究和控制取得较大成就的国家之一,在二噁英实验室检测方面一直走在世界的前列,本文简单介绍日本近年来二噁英检测以及分解技术的发展。