Genesis of micrinite in some Australian coals

Seven Australian coals have been examined petrographically and two types of micrinite, disseminated micrinite and cavity-filling micrinite, are described. The disseminated micrinite appears to be very fine fragments of fusinite, semifusinite and other low reflectance inertinite. Cavity-filling micrinite occurs only in inertinite-rich coal seams and was formed under aerobic conditions. It is considered that porigelinite and other granular material in peat are the major progenitors of the cavity-filling micrinite. Such progenitors would have entered cell cavities and other voids, possibly as a water slurry, before or after they had been partially oxidized.     

Distribution of potentially hazardous trace elements in coals from Shanxi province, China

Shanxi province, located in the center of China, is the biggest coal base of China. There are five coal-forming periods in Shanxi province: Late Carboniferous (Taiyuan Formation), Early Permian (Shanxi Formation), Middle Jurassic (Datong Formation), Tertiary (Taxigou Formation), and Quaternary. Hundred and ten coal samples and a peat sample from Shanxi province were collected and the contents of 20 potentially hazardous trace elements (PHTEs) (As, B, Ba, Cd, Cl, Co, Cr, Cu, F, Hg, Mn, Mo, Ni, Pb, Sb, Se, Th, U, V and Zn) in these samples were determined by instrumental neutron activation analysis, atomic absorption spectrometry, cold-vapor atomic absorption spectrometry, ion chromatography spectrometry, and wet chemical analysis. The result shows that the brown coals are enriched in As, Ba, Cd, Cr, Cu, F and Zn compared with the bituminous coals and anthracite, whereas the bituminous coals are enriched in B, Cl, Hg, and the anthracite is enriched in Cl, Hg, U and V. A comparison with world averages and crustal abundances (Clarke values) shows that the Quaternary peat is highly enriched in As and Mo, Tertiary brown coals are highly enriched in Cd, Middle Jurassic coals, Early Permian coals and Late Carboniferous coals are enriched in Hg. According to the coal ranks, the bituminous coals are highly enriched in Hg, whereas Cd, F and Th show low enrichments, and the anthracite is also highly enriched in Hg and low enrichment in Th. The concentrations of Cd, F, Hg and Th in Shanxi coals are more than world arithmetic means of concentrations for the corresponding elements. Comparing with the United States coals, Shanxi coals show higher concentrations of Cd, Hg, Pb, Se and Th. Most of Shanxi coals contain lower concentrations of PHTEs.     

Fluidized-bed gasification of some Western Canadian coals

Three Western Canadian coals were gasified with air and steam in a fluidized bed of 0.73 mm sand and coal, at atmospheric pressure and temperatures of 1023–1175K to produce a low-calorific-value gas. One non-caking and two caking coals were tested. The effects of temperature, coal feed rate, $\text{air}\text{coal}$ ratio, $\text{steam}\text{coal}$ ratio, coal quality, coal particle size and bed depth on gas composition, gas calorific value and operating stability of the gasifier were established. Results are compared with those previously obtained for the same three coals when gasified in essentially the same equipment, but operated as a spouted bed.     

Oxidation of some bulgarian coals. Influence of low-temperature oxidation on the microhardness and reflectivity of some brown coals

Experiments carried out with two clarain and three vitrain samples from the Bobovdol basin and two clarain samples from the Pirin basin have shown that changes in microhardness and random reflectance are useful indications of changes which occur in the coal substance during oxidation processes at 150 and 200 °C and subsequent extraction.     

Prediction of unburnt carbon in tangentially fired boiler using Indian coals

Accurate prediction of percentage unburnt carbon in fly ash in the case of high ash content Indian coal, at the design stage, is generally difficult. In the present paper, a large number of laboratory test data and site data are used to understand the mechanism of unburnt carbon in fly ash as well as in bottom ash. Rigorous statistical analysis of the performance data taken from tangentially fired boilers shows that empirical correlation between a combination of coal properties and percentage unburnt carbon in fly ash exist. Equations to predict percentage unburnt carbon in fly ash and bottom ash have been proposed.     

Cleaning of Indian coals by agglomeration with xylene and hexane

A laboratory scale agglomeration process has been undertaken for cleaning Indian coals using oils namely, xylene and hexane. Maximum organic matter recovery for xylene has been found to be 91.9% whereas with hexane, the value is 54.7% on a dry basis. The highest ash rejection values with xylene (90.7%) and with hexane (89.7%) are almost same. Promising results for rejection of metals (Fe, Mg and Zn) have been observed. It has been found that xylene is more selective than hexane for the agglomeration process. Knowledge gained from this study will be helpful for technological advancement of this kind of work.     

Investigation of the flash pyrolysis of some coals

Five bituminous coals, an anthracite and a lignite have been flash-pyrolysed by the electrically-heated grid technique or by means of an electrically-heated fluidized-bed. In the experiments using a heated grid, data were obtained on rates of rapid devolatilization and on the composition of the gases and tars evolved with heating rates up to 3000 Ks^?1 and peak temperatures up to 1400 K. Similar, but more limited data were obtained using the fluidized-bed system. Mathematical models based on overall single- or two-reaction pathways were compared with the experimental results. Good agreement could be achieved by the latter with activation energies of 16 and 35 kJ mol^?1.     

Electron spin resonance studies of some Canadian coals

Nine Canadian coals of different rank and composition were studied by electron spin resonance. For percentage of fixed carbon in the range of 43 to 78 wt%, the free radical g values were found to increase with decreasing carbon content, and did not level off for the low rank coals. The free radical linewidths are attributed to atomic species such as oxygen and not to protons of hydrogen.     

Solubilisation of some bituminous coals in quinoline by ultrasonic irradiation

The solubilisation of 4 hvab and 1 hvbb coals by ultrasonic irradiation of coal-quinoline systems at ambient temperature was investigated. The amount of coal solvated was found to be a function of time and particle size. The use of a char prepared at the temperature of maximum coal fluidity increased the amount of material solubilised. There was little difference in the amounts of coal solubilised at 36° and 80°. There was a decrease in the sulphur and ash content of the solubilised coal compared with the starting coal. Quinoline can be re-used as a solvent with no decrease in solubilisation efficiency. Based on high-resolution mass spectrometric and infra-red spectroscopic investigations and particle size measurements of the solubilised material, it appears that the increased solubilisation of coal in quinoline results from a grinding action and not a chemical action.     

Composition and properties of coals from some deposits in Mongolia

Nine coal samples from different deposits in Mongolia were studied with the use of a set of chemical and physicochemical methods of analysis (proximate and ultimate analyses, low-temperature extraction, the chemical analysis of ashes, thermogravimetric analysis, IR spectroscopy, and thermal dissolution) for evaluating their composition and chemical-engineering properties.     

Qualitative characteristics of power-generating coals from some deposits in Mongolia

The results of a study of the chemical composition and technological properties of coals from the Khar Tarvagatai, Nuurst Khotgor, and Khushuut deposits are presented in this article.     

Capture of volatile hazardous metals using a bed of kaolinite

One of the promising technologies for reducing metals emission from the waste thermal process is the capture of vapor-phase metals through the use of solid sorbents. This study investigated the use of natural kaolinite for the removal of several volatile metals. The capture of cadmium and lead using a packed bed with porous kaolinite of the size range 300-400 Μm was effective. The capturing efficiency increased as the bed temperature increased. The ratio of the sorption reaction rate to the diffusion rate varied on the 10^-2 order of magnitude. This suggests that the resistance of the diffusion within the pores of kaolinite particles is not significant in the selection of sorbent particle size for practice. The capturing mechanism for cadmium chloride is different from that for lead chloride. Cadmium can be reactively scavenged by CdO-Al₂O₃-2SiO₂ as well as metakaolinite, suggesting that a unit mole of metakaolinite can ultimately capture two moles of cadmium.     

部分进口煤炭中氟元素的含量特征及赋存形态

为加强对进口高氟煤炭的管理,评价进口煤炭中氟元素的环境迁入风险,采用高温燃烧水解-氟离子选择电极法对唐山港口岸进口的225批煤炭中的氟含量进行了测定;用稳健统计描述了其整体含量水平,并根据我国煤炭行业分级标准及富集比进行了质量评价;用相关分析对氟的赋存形态进行了分析。结果表明:唐山港口进口煤炭中的氟含量可描述为(137±24)mg/kg;按我国煤炭行业标准进行质量分级评价,唐山港口进口的68%的朝鲜煤、62%的加拿大煤属于中氟煤,氟含量算术平均值高于中国煤、世界煤,其迁入风险值得关注;进口朝鲜煤中氟含量与灰分、全硫含量呈中度正相关、与磷含量呈微弱正相关,推断氟的赋存形态主要为无机硫结合态(硫化物和硫酸盐)和黏土矿物,少部分可能存在于磷酸盐类矿物及有机硫结合态中;进口澳大利亚煤中氟含量与灰分、全硫含量相关性不显著,与磷含量呈低度正相关,推断氟的赋存形态比较复杂,可能部分以磷酸盐结合态存在,赋存于氟磷灰石、磷铝钙石中;进口加拿大煤中氟含量与灰分、全硫含量相关性不显著,与磷含量的相关性系数为0.763,显著性水平为0.01,表明二者呈高度正相关,具有显著性,说明二者有很强的伴生关系,推断氟主要以磷酸盐结合态存在,赋存于氟磷灰石、磷铝钙石中。     

Influence of high ash Indian coals in fluidized bed gasification under different operating conditions

Coal gasification has been internationally accepted as one of the most viable and effective clean coal technology for power generation. Presently, the coal being produced in India is having high ash content and it is a major constraint for most of the commercial applications in process industries. The present paper deals with the variation of higher heating value (HHV) of the product gas and carbon conversion with different inherent properties under different operating conditions in fluidized bed gasification. It has been observed that HHV of product gas increases with volatile mater, fixed carbon and temperature, whereas, mineral matter, air and steam show decreasing effect on HHV. On the other hand, carbon conversion increases with volatile matter, air, steam and temperature. It has also been observed that mineral matter provides catalytic effect to a certain level for carbon conversion, whilst, decreasing trend has been observed with the fixed carbon.     

Safe storage and transportation of some potentially hazardous materials

Many materials which are stored and transported in bulk undergo exothermic decomposition or oxidation reactions at elevated temperatures. Such reactions may render them liable to spontaneous ignition if they are in sufficient quantity and at such a temperature that the rate of heat production exceeds the rate at which heat is able to be transmitted to the surroundings. Steady-state thermal explosion theory has been used to predict safe storage and transportation (critical) masses at a series of temperatures for three representative types of self-heating materials—baled wool, powdered ammonium nitrate and a solution of methylethyl ketone (2-butanone) peroxide (40%) in dimethyl phthalate. The non-steady-state theory (reactant consumption admitted) has been used to estimate the time taken for these critical masses to reach the critical state at each temperature. The critical masses have been shown to be consistent with safety requirements at present accepted for the storage and transportation of the materials discussed. The estimates of the times taken by the critical masses to reach the critical state bring an added dimension to the critical mass calculations, and together these results constitute an advance over the present situation where safe limits have been deduced on a trial and error basis. The methods outlined may be used to estimate critical masses and induction periods for any other self-heating material and may be relied upon to give results of the correct order of magnitude.     

Response of inertinites from some Australian coals to non-catalytic hydrogenation in tetralin

Inertinite concentrates from three Australian bituminous coals were hydrogenated at various temperatures ranging from 350 to 475 °C in the presence of tetralin without any added catalyst. Both conversion yields and microscopic observations of the benzene-extracted hydrogenation residues have revealed that the hydrogenation of the inertinite macerals becomes significant only > 400 °C, whereas the dissolution-hydrogenation of the accompanying vitrinite macerals occurs mainly between 350 and 400 °C. The major reaction pathway for the inertinite particles in the hydrogenation process appears to be one of initial mild carbonization followed by hydrogenation. A simplified reaction scheme is proposed which describes the reaction pathway involved in the hydrogenation of inertinite.     

Carbonization of coals to produce anisotropic cokes. 1. Modifying activities of some additives in the co-carbonization of low-rank coals

Using low-rank coals, the modifying activities of some petroleum, coal tar and aromatic hydrocarbon additives have been examined to find procedures for their utilization in the preparation of blast furnace coke. Petroleum pitch, especially after hydrogenation, exhibited excellent modifying activity even with non-fusible coals. In contrast, the activity of coal tar was very limited with such coals. The napththenic component, revealed by n.m.r. of the additives, appears to be important in the co-carbonization by inducing fusibility and anisotropic development in such coals. Co-carbonization to recover the dehydrogenated additives was attempted. However, there was no development of the anisotropy in the resultant coke by dissolution of the coal particles although the coal particles were firmly fixed in the matrix. Acid-refluxing treatment of non-fusible coals was found to enhance their modification susceptibility, indicating that some of the acid-soluble mineral matter is important in the thermal depolymerization or fusion process of the coal.     

Electrodeposition of some metals from tetramethylurea

Zinc, cadmium and bismuth have been electrodeposited on copper from tetramethylurea, a new organic electrolyte. The nature of the deposits so obtained was good. A more quantitative treatment of the electro-deposition of these metals from this solvent is suggested.