Changes in the reaction regime during low-temperature oxidation of coal in confined spaces

A study of the initial stage of the low-temperature oxidation of coal is important, not only for the prevention for fires in coal industry, but also in reducing emissions of hazardous gases. A batch reactor was introduced and a series of simulated experiments of coal oxidation was carried out in this paper. The time-dependent rates of CO emission and oxygen consumption during oxidation experiments of coal samples with different particle size ranges were obtained simultaneously from the measurements of CO and O₂ concentration in the reactor. The experimental results show that the rate of CO emission presents three stages in the duration of coal oxidation. Based on the rates of oxygen consumption, the reaction order and reaction rate were obtained from the reaction rate equation. These results indicate that the reaction regime switches during coal oxidation in confined spaces. The initial decrease of reaction rate is due to the decrease of the active sites in coal. While the decrease of reaction rate in the following period of coal oxidation is attributed to the reaction-inhibition mechanism of oxidation products. And it is mainly represented by the chemisorption sequence of coal oxidation. The oxidative activity of coal can be restored when the oxidation products are evacuated. A mechanism of low-temperature oxidation of coal in confined spaces was also suggested.     

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.     

Assessing determinants of industrial waste reuse: The case of coal ash in the United States

Devising effective strategies to facilitate waste reuse depends on the solid understanding of reuse behaviors. However, previous studies of reuse behavior have been limited in scope, focusing mostly on household recycling behaviors or very limited types of industrial wastes. To gain a better understanding of the business reuse behaviors, this study examined the impact of various factors in technical, economic, regulatory, and behavioral categories in the case of coal ash generated in the United States. The results of fixed effect models for fly ash and bottom ash particularly showed the significance role of the behavioral factor. In both models, a proxy variable, which represents knowledge sharing among the power plants or the utility's decision-making, turned out to be statistically significant and had the largest coefficient estimates among a group of variables. This finding may imply that the characteristics of waste reuse behavior are determined more by business decision-making behaviors than by market or institutional factors. However, the role of the behavioral variable was stronger in the bottom ash models than in the fly ash models. While the reuse of bottom ash was determined primarily by the behavioral variable, fly ash reuse was determined by more diverse factors including economic and regulatory variables. This could be explained by material characteristics in relation to competing resources and the nature of reuse applications.     

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.     

“十五”期间沈阳市煤炭消费与大气污染相关性分析

通过对沈阳市“十五”期间经济发展所引起的煤炭消费量与大气污染之间的关系进行分析后可知,“十五”期间沈阳市煤炭消耗量与大气污染物排放量、大气环境质量均呈现为“负相关性”,经解析,“十五”期间由于沈阳市采取了煤炭管制、推行集中供热提高煤炭使用效率等手段,使得煤炭消费在增长的情况下大气污染物排放量降低、环境空气质量逐步改善,呈现为“负相关性”。     

兖州矿区循环经济与可持续发展研究

按照循环经济的理论,结合兖州矿区产业链,提出了兖州矿区循环经济的初步模式和对策。最后,以济三煤矿为例,介绍了兖州矿区循环经济的实践。     

Detailed in-furnace measurements with reburning of superfine pulverized coal in high CO2 concentration

This paper presents detailed measurements of gaseous species during the reburning process with high CO₂ concentration in a bench-scale furnace. Superfine pulverized coal, with the average particle size below or around 20 μm, is used as the reburning fuel. The data of flue gas concentration (NO_x, HCN, NH₃, CH₄, O₂, CO, CO₂ etc.) is obtained in order to reveal the intrinsic connection between NO_x emissions and other influential gaseous species at different positions of the furnace. The finding concludes that the advantage of superfine pulverized coal with regard to NO reduction is more efficient in homogeneous stage rather than heterogeneous stage. Meanwhile, the evolution of HCN and CH₄ agrees well with each stage of NO reduction, which indicates that these gaseous species are favorable for NO abatement. Eventually, oxygen consumption rate for superfine pulverized coal is relatively faster, conducive to strengthen both homogeneous and heterogeneous NO reduction under CO₂ reburning condition.     

The lack of microbial degradation of polycyclic aromatic hydrocarbons from coal-rich soils

Analytical techniques used to assess the environmental risk of contamination from polycyclic aromatic hydrocarbons (PAHs) typically consider only abiotic sample parameters. Supercritical fluid extraction and sorption enthalpy experiments previously suggested slow desorption rates for PAH compounds in two coal-contaminated floodplain soils. In this study, the actual PAH availability for aerobic soil microorganisms was tested in two series of soil-slurry experiments. The experimental conditions supported microbial degradation of phenanthrene if it was weakly sorbed onto silica gel. Native coals and coal-derived particles in two soils effectively acted as very strong sorbents and prevented microbial PAH degradation. The long history of PAH exposure and degree of coal contamination apparently had no influence on the capability of the microbial soil community to overcome constraints of PAH availability. Within the context of the experimental conditions and the compounds chosen, our results confirm that coal-bound PAHs are not bioavailable and hence of low environmental concern.     

对伊犁地区民用燃煤放射性限值的探讨

探讨了将煤炭中铀含量１０ｍｇ／ｋｇ作为伊犁地区民用燃煤放射性限制指标的合理性．     

火电厂煤尘污染防治主要措施研究

文章通过对火电项目煤尘产生源的分析,根据北方地区社会、经济、环境现状,提出电厂储煤场及输煤系统煤尘的主要防治措施,从而为北方经济欠发达地区火电厂的煤尘污染防治提供一些参考依据,促进环境质量的改善.