Natural weathering of coal

The effects of weathering on the mean maximum vitrinite reflectance, moisture content, and low-temperature ash mineralogy of the low volatile bituminous, Lower Mississippian Price Formation coals of southwest Virginia were determined on samples from depth profiles of three weathered coal beds. The results show that the outermost ≈50 cm of each seam is intensely weathered showing humic acid formation, higher moisture content and physical disintegration. Beyond this depth (which corresponds to the average frost depth of this area), the amount of weathering decreases sharply. Freezing and thawing appear to be important in weathering the outermost zone, and, together with wetting and drying, disintegrate the coal creating reactive surfaces that oxidize readily. Reflectance values from weathered coal were found to be reliable indicators of rank if measurements were taken away from identifiable weathering features. The low-temperature ash mineralogy (silicates) showed no change with weathering.     

Auto-desulphurization of coal

The effect of atmospheric oxidation or weathering on different forms of sulphur in coal has been studied using a coal sample ground to <63 μm and kept exposed to the atmosphere for up to 228 days. Occasionally, samples were taken from the exposed coal for analysis of total-, sulphate-, pyritic- and organic sulphur. Significant amounts of total-, pyritic- and organic sulphur were reduced up to 106 days of exposure, resulting in a total sulphur content within the permissible limits of utilization. Thus, commercial desulphurization of coal may be possible by using the simple process of atmospheric weathering.     

Fabricating translucent polydimethylsiloxane (PDMS) super-hydrophobic surface greenly by facile water-dissolved fillers

In this study, a polydimethylsiloxane (PDMS) colloid was cast onto a template made of recycled polypropylene for structural duplication to fabricate translucent super-hydrophobic surfaces greenly without the use of any complicated method. The surface structure of the template was formed by hot embossing using salt grain fillers dissolved in water. The resulting contact angle (CA) values of fabricated PDMS surfaces were 153.4 ± 0.6°, 152.3 ± 1.8°, 152.2 ± 0.8°, and 152.0 ± 1.6° and the associated slide angle (SA) values were 5.8 ± 0.6°, 8.7 ± 1.5°, 8.6 ± 1.1°, and 16.3 ± 1.9° for filler grain size categories A, B, C, and D, respectively. The surfaces with grain sizes A, B, and C exhibited super-hydrophobic conditions, where CA > 150° and SA < 10°; on the other hand, the surface with grain size D exhibited an SA value greater than 10°. The measured percentages of light transmittance in the visible wavelength range of 400–800 nm were 75–80% for grain sizes B, C, and D and 85–90% for grain size A. Furthermore, a green laser light was diffused from a spot of 0.5–7.7 cm in diameter; related glare was also eliminated.     

Ruthenium tetroxide catalysed oxidation of illinois no.6 coal and some representative hydrocarbons

The use of ruthenium tetroxide for the catalytic oxidation of coal molecules under mild conditions has been examined. The selectivity of the reagent for aromatic nuclei has been assessed by a study of the oxidation of selected benzene, naphthalene and phenanthrene derivatives. The catalysed oxidation of Illinois No.6 coal has been studied. The preliminary results described in this report suggest that this oxidant is effective for the selective oxidation of the aromatic structures in this coal.     

Low-temperature oxidation of Victorian brown coal

A study has been made of low-temperature oxidation of Victorian brown coal at 35 °C and oxygen pressure of 0.1 M Pa and regression analysis of the experimental results shows that the reaction can best be described by the continuous reaction model. The reaction is subject to reaction product inhibition, apparently caused by product adsorption. Progressive conversion is obtained through a series of cycles consisting of a reaction step followed by evacuation of the coal. The rate equation developed from the continuous reaction model describes satisfactorily the progress of the reaction in each of these cycles. A study of earlier findings on the nature of Victorian brown coal oxidation products indicates that the product water may be significant in this reaction inhibition.     

Detection of natural oxidation of coking coal by TG-FTIR—mechanistic implications

The natural oxidation/weathering of coal continues to be a subject of interest both scientifically and industrially, in part due to the complexity of the molecular processes at hand as well as to the commercial implications involved. It is widely recognized that coking can be adversely affected by weathering whereas, combustion processes appear to be enhanced as result of oxidation.Combustion techniques are commonly used in the analysis of coal, and organic compounds in general, for the determination of elemental hydrogen, carbon and nitrogen. For oxygen, the method in common practice involves the determination by difference from directly determined values for moisture, ash, sulphur, hydrogen, carbon and nitrogen. This has led us to consider the use of thermogravimetry coupled to gas analysis by infrared spectroscopy (TG-FTIR) to measure organic oxygen in coal directly. Although this technique, developed by Solomon and coworkers, has been extensively used by our group and others, it appears not to have been considered for this particular purpose.Recently, we have shown that TG-FTIR is capable of measuring all the organic oxygen in both fresh and oxidized coal by simultaneous measurement of the three main oxygen-containing gases H₂O, CO and CO₂ evolved during rapid pyrolysis. This gives us a way of measuring quantitatively the oxygen introduced into the coal matrix during oxidation and at least a partial capability of establishing oxygen speciation.We have found, using TG-FTIR, that the early stages of coal oxidation results in the appearance of O-containing functional groups not present in the original coal. The nature of these functional groups is directly related to the oxidation reaction mechanism. These results will be presented and discussed in detail.     

Oxidation states in surface and buried coal from the Fording River Deposit

A suite of five representative samples from a freshly opened adit in the Fording River Coal Deposits, BC was taken at selected distances from the surface to the 45.7 m depth of the seam to provide material for studying the progress of coal oxidation under natural conditions. The ‘as-mined’ < 28 US mesh material from each sample was subjected to standard proximate, ultimate and free swelling index (FSI) analyses, followed by quantitative evaluation of surface oxidation states, using several techniques concurrently. Correlation of the results indicates a progressive decrease in oxidation from a very high level for the surface sample, with FSI 1, to a relatively low oxidation level for samples taken at 22.9 m and 45.7 m distances. Solvent extracts show a progressive decrease in the ratio of soluble aliphatic-to-aromatic compounds from surface to deep coal and in the amount of carboxylate groups. Oxidized coals require pretreatment with dilute acids in order to convert phenolate and carboxylate salts into phenols and carboxylic acids respectively; the analytical results for the latter are then increased by a factor of 4–6.     

Further studies of coal oxidation

The low-temperature oxidation of coal has been investigated by Fourier transform infrared spectroscopy (FT-i.r.). Samples were oxidized at 140 and 60 °C for intervals of a few hours to days. These FT-i.r. results were correlated to changes in the thermoplastic properties of the coal measured by a Gieseler plastometer. The loss of Gieseler fluidity as a function of oxidation time corresponds to loss of aliphatic CH groups. Curve-resolving methods were used to distinguish between various C = 0 functional groups. At both oxidation temperatures there was an overall increase in carbonyl and carboxyl groups, but in different relative proportions depending on the oxidation temperatures.     

3000m~3航空煤油罐氟蛋白泡沫液下喷射消防设计

介绍了氟蛋白液下喷射消防的灭火原理、特点及注意事项。对民航机场油库贮罐消防设施的工艺流程、设备选型等进行了设计计算。该工艺方法消防操作简便、效果良好。     

Distribution of free gaseous oxygen in coal stockpiles

This study confirms that the distribution of free gaseous oxygen in a coal stockpile agrees with a previously published model for self-heating within the stockpile. The simplified, isothermal model of the study predicts a hyperbolic cosine distribution which is characterized by a single parameter, the Thiele modulus. This depends on the stockpile properties of size, intraparticle porosity, oxygen diffusivity and the coal properties of density and reactivity towards oxygen. The Thiele modulus can be determined from two measurements of oxygen concentration at different depths in the pile. Changes in coal reactivity (weathering) on prolonged exposure to atmospheric oxygen are reflected in the magnitude of the Thiele modulus and thus can be measured in situ at storage temperatures.     

Release of oxygen and sulphur compounds from coal

The evolution of small quantities of carboxylic acids, indanols and phenols and of dibenzothiophenes and azadibenzothiophenes at temperatures up to 300 °C has been studied by pyrolysis-mass spectrometry.     

Capillary reactor for cyclohexane oxidation with oxygen

Cyclohexane oxidation is the first step in the currently used technology for production of Nylon-6 and Nylon-6,6 which employs a two-stage process. In the first stage 80% selectivity to two main products, cyclohexanol and cyclohexanone (KA oil) is obtained at 4–8% cyclohexane conversion in staged bubble columns or stirred tanks. There have been reports that increased oxygen concentration in the gas phase or pure oxygen is beneficial to cyclohexane oxidation and this was confirmed in our previous study (Jevtic et al., 2009). To fully utilize this advantage here, we present a novel, safer capillary reactor for cyclohexane oxidation with pure oxygen. The discrepancy between the experimental and modeling results was attributed to lower than expected mass transfer achieved in the capillary. With a better design for gas–liquid mixing and contacting this type of a reactor could potentially become attractive for gas–liquid reactions of similar nature.     

Mild oxidations of coal: 1. Hydrogen peroxide oxidation

Mild oxidation of Pittsburgh bed coal was carried out to investigate the removal of organic sulphur. It was postulated that the organic sulphur in coal might first be oxidized to sulphonic acids and then removed through known desulphonation methods. The coal was oxidized with hydrogen peroxide or mixtures of hydrogen peroxide and acid. After oxidation, the coal was treated with water or phosphoric acid at reflux. Under the mild conditions used, coal oxidation led to slight changes in the organic sulphur content. The ensuing treatment of the oxidized coal with water or phosphoric acid again affected the organic sulphur content, generally decreasing the organic sulphur level. Pyritic sulphur removal varied considerably depending upon the reagent system and reaction conditions.     

煤气化废水的超临界水氧化处理实验

对煤气化废水的超临界水氧化处理效果开展了探索性实验研究,以污水、污泥处理达标为目标,对过程中的工艺条件及有害物质的去除效果进行了研究和评价,结果表明,优化条件下无需经过预处理及后续深度处理,出水主要指标即可达到国家《污水综合排放标准》(GB 8978—1996)一级排放标准,并可实现废水的无害化处理和污泥的无害化减量。在此基础上,创新性地提出了碎煤加压气化-超临界水氧化组合工艺方案。     

Catalytic action of minerals in the low temperature oxidation of coal

The mild oxidation of coal by air in a fluidized-bed reactor has been studied by utilizing X-ray powder diffraction, scanning electron microscopy accompanied by energy dispersive X-ray analysis and Mössbauer spectroscopy. These techniques show that some of the highly dispersed minerals in coals undergo changes concurrently with the reactions of the coal matter. An oxidation treatment at a reactor temperature of 350 °C transforms most of the pyrite (FeS₂) into hematite (Fe₂O₃) andthecalcite (CaCO₃) into anhydrite (CaSO₄). Pronounced pitting of the coal surface was observed in the vicinity of mineral crystallites and particles. Calcium was present as a dominant element in those minerals that caused the oxidative pitting to occur most rapidly.     

臭氧氧化深度处理煤化工废水的应用研究

臭氧氧化作为一种有效的深度处理技术,对有机废水具有良好的降解功效。介绍了臭氧的性质及氧化机理,分析了臭氧氧化法在处理纺织印染废水、造纸废水、垃圾渗滤液、炼油废水、焦化废水等难降解有机废水中的应用,指出了臭氧氧化存在的问题,并提出建议。     

低阶煤中氧的测定方法及对煤直接液化的影响

氧是煤中最丰富的杂原子,其含量和存在形式对煤的性质有很大影响,特别是对低阶煤的影响更为显著。低阶煤中的氧主要以酚羟基和醚键形式存在,此外还有羰基、羧基和呋喃等。介绍了低阶煤中含氧官能团的测定方法,结果发现:物理方法方便快捷,但XPS、IR等分析手段因一些峰值无法识别,降低了实用性;化学方法步骤繁琐,操作时间长且准确性较差。综述了含氧官能团对煤直接液化的影响,酚羟基在液化过程中因发生交联反应而产生负面影响;高级醚类具有高的液化特性;羧基的液化机理复杂,没有统一的意见。     

Free-radical involvement in the drying and oxidation of victorian brown coal

The technique of electron spin resonance spectroscopy has been used to study the changes in free-radical nature and content of brown coals as a result of vacuum drying the coal at various temperatures, and exposing the dried coal to either air at room temperature or oxygen at 105 °C. Free-radical concentrations increased during the vacuum-drying process and this is thought to be a result of organic functional group breakdown. Free-radical concentrations in dry coals following air or oxygen exposure have been found to vary with exposure time. The observations can be explained in terms of free-radical involvement in the oxidation process.     

Anodic oxidation of coal slurries in flow-through packed bed electrodes

Experimental studies were made to determine the characteristics of anode systems depolarized by coal slurries. The anode was a packed bed of platinum-plated titanium pellets, through which the slurries were recirculated. This flow system increased collisions between coal particles and the anode surfaces so that the anodic oxidation of the coal was enhanced. At the same time, soluble organic compounds and Fe²⁺ ions dissolved from the coal were oxidized at the anode, and Fe³⁺ was reduced by thermochemical reactions with reducing compounds in the coal; this reduction was important in maintaining the current density in long-term electrolysis.     

Thermal and oxidation chemistry of coal at low temperatures

The chemical reactions which occur when Illinois No. 6 (hv C) and Rawhide (SBB C) coals are thermally pretreated at 100°C and when Illinois No. 6 coal is subsequently oxidized at 100°C with O₂ have been studied using in-situ FT-i.r. differende spectroscopy. Significant spectroscopic changes were seen. Vacuum drying at 100°C resulted in the decomposition of carboxylic acid species to form a variety of new carbonyl species (in Rawhide) and decarboxylated or decarbonylated coal (Illinois No. 6). Oxidation of predried Illinois No. 6 coal leads to the formation of new carbonyl species. The assumption that drying does not alter the chemical composition of coal may not be correct. Thus, overall spectroscopic (and chemical) changes observed in moderate temperature reaction studies may depend upon sample pretreatment, drying and storage. In addition, the time/temperature profile used in a reaction study may affect the overall changes observed by altering the relative contribution of the different reactions.