Concentrations and sources of polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments of the Yellow River Estuary (YRE). The isobath-parallel tidal and residual currents play important roles in the variation of PAH distribution, such that the contamination level of PAHs in fine-grained sediments is significantly higher than in the relatively coarse grain size sediments. Both diagnostic ratios and principal component analysis (PCA) with multivariate linear regression (MLR) were used to apportion sources of PAHs. The results revealed that pyrogenic sources are important sources of PAHs. Further analysis indicated that the contributions of coal combustion, traffic-related pollution and mixed sources (spills of oil products and vegetation combustion) were 35, 29 and 36 %, respectively, using PCA/MLR. Pyrogenic sources (coal combustion and traffic-related pollution) contribute 64 % of anthropogenic PAHs in sediments, which indicates that energy consumption could be a predominant factor in PAH pollution of YRE. Acenaphthylene and acenaphthene are the two main species of PAHs with more ecotoxicological concern in YRE.
Discharging waste gangue from coarse iron ore prior to subsequent upgrading and purification is beneficial to decrease the energy consumption in the grinding stage. In this study, a dry density-based gravity separation technique was used to improve the quality of iron ore by discharging waste gangue. Mineralogical analysis results indicated that the major component of raw iron ore is hematite with small amounts of magnesioferrite and magnetite, and the elements included in the iron ore sample were Fe, Si, S, Mg, Al, and Ca, and the specific iron–compounds (Fe O , Fe O , and FeS ) were determined. High-density gas-atomized iron powder and low-density zircon sand with specific size fractions were validated for appropriateness for mixing in proportion as a binary dense media for the dry separation of coarse iron ore. A regulatory model of the bed density based on the composition of the binary dense media was proven efficient in predicting and adjusting the bed density for separating the coarse iron ore. The actual separation experiments of −31.5 + 6 mm iron ore indicated that the concentrate yield and grade of 83.4% and 52.4%, respectively, were achieved with the highest Fe-recovery of 96.1% at a gas velocity of 6.37 cm/s. The concentrate yield and grade of 63.7% and 52.7%, respectively, with the highest Fe-recovery of 73.0% were achieved at a static bed height of 80 mm. Both the results suggested the satisfied separation performance. The fundamental investigation indicated that discharging waste gangue using the dry gravity separation prior to further upgrading coarse iron ore has substantial potential in industry.
The main concerns of coal power plants are related to high thermal efficiency and biomass utilization for the reduction of CO emissions. In this work, the fuel characteristics of a hybrid coal (HCK) impregnated by sugar impurities extracted from a lignocellulosic biomass were investigated. First, an optimized extraction condition for the sugar impurities was chosen among the various reaction temperatures and times using a hydrothermal pre-treatment (HTP) reactor. The extracted sugar impurities were consisted of 21.76 wt% glucan, 75.88 wt% XMG (xylan + mannan + galactan) and 2.36 wt% arabinan at the optimized reaction condition (190 °C and 30 min). 5 wt% sugar impurities based on the coal weight (dry basis) was used to prepare the HCK and the fuel characteristics were compared. According to the H/C and O/C ratios, raw coals were upgraded. In addition, the calorific value of the raw coals was enhanced by HCK production process. The HCKs had a low moisture re-adsorption rate in an excessive water immersion condition compared to the raw coals. To clarify the combustion behavior of the HCKs, thermogravimetric analysis (TGA) was carried out. The HCKs had a single-stage combustion pattern on the differential thermogravimetric (DTG) curve, even though they were composed of a coal and biomass resource. During the kinetic study of the raw coals and HCKs, a high reaction rate constant ( ) and low activation energy ( ) for the HCKs were identified compared to that of the raw coals.
Humic-like substances (HULIS) are a mixture of high-molecular-weight, water-soluble organic compounds that are widely distributed in atmospheric aerosol. Their sources are rarely studied quantitatively. Biomass burning is generally accepted as a major primary source of ambient humic-like substances (HULIS) with additional secondary material formed in the atmosphere. However, the present study provides direct evidence that residential coal burning is also a significant source of ambient HULIS, especially in the heating season in northern China based on source measurements, ambient sampling and analysis, and apportionment with source-oriented CMAQ modeling. Emission tests show that residential coal combustion produces 5% to 24% of the emitted organic carbon (OC) as HULIS carbon (HULISc). Estimation of primary emissions of HULIS in Beijing indicated that residential biofuel and coal burning contribute about 70% and 25% of annual primary HULIS, respectively. Vehicle exhaust, industry, and power plant contributions are negligible. The average concentration of ambient HULIS in PM2.5 was 7.5 mu g m(-3) in urban Beijing and HULIS exhibited obvious seasonal variations with the highest concentrations in winter. HULISc accounts for 7.2% of PM2.5 mass, 24.5% of OC, and 59.5% of water-soluble organic carbon. HULIS are found to correlate well with K+, Cl-, sulfate, and secondary organic aerosol, suggesting its sources include biomass burning, coal combustion, and secondary aerosol formation. Source apportionment based on CMAQ modeling shows residential biofuel and coal burning and secondary formation are important sources of ambient HULIS, contributing 47.1 %, 15.1 %, and 38.9 %, respectively.
An improved method for coal breakage characterisation has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC). Part 1 of this paper presents the breakage testing method and results, Part 2 gives a breakage model that determines the energy-size reduction relationship for multi-components of particle size and coal density, and Part 3 demonstrates the applications of the model for HGI predictions and coal breakage simulations. The new method incorporates hardware for a fine particle breakage characterisation test, the JKFBC (JK Fine-particle Breakage Characteriser), a device modified from the standard HGI mill, which has a precision torquemeter installed to record energy utilisation during the experiments. Distinguished from the traditional HGI test, which is based on a single particle size with a single energy, the new characterisation test offers the flexibility to grind coal particles at various sizes, or various densities, or indeed (various components) with a range of energy levels. Energy consumption during the grinding was recorded. Using an Australian and a Chinese coal sample collected from power stations, this paper demonstrates the effects of particle size and density on coal breakage, and elucidates the deficiencies associated with the traditional HGI test.
The long cooling time of charcoal produced from eucalyptus pyrolysis is due in part to the heat generation in oxidation reactions at low temperatures. The intensity of this reactions depends on complex interactions between the interstitial gas and the solid matrix. The objective of this paper was to investigate the kinetics of the self-heating phenomena due to charcoal oxidation at low temperatures and at different oxygen concentrations. Samples of 230 g of charcoal were subjected to heating in a steel reactor at constant temperature, from 100 to 300 °C, and oxygen concentrations ranging from 20.9 to 10%. Was evidenced that the rate of oxygen consumption increases with charcoal temperature at rates that depend on the initial concentration of O . The beginning of the oxidation reactions was observed at 67 °C in atmospheres with 20.9% O . The overall activation energy for the self-heating phenomenon was 17,790 J mol and its intensity was increased with the temperature and O concentration.
From an environmental and economic perspective coal handling and preparation plants are under increasing pressure to reduce their consumption of fresh water and to strictly follow tight standards and specifications to release process water. Many coal washeries use recycled water as part of their water management strategy, which contains a higher content of inorganic electrolytes. In this study, five water samples from four coal washeries were analysed. The effect of methyl isobutyl carbinol (MIBC) frother was tested to evaluate the influence of water composition on the persistence of bubble pairs and the effectiveness of MIBC in preventing coalescence in a quiescent and dynamic environment, respectively. It was shown that the coalescence time was longer for bubbles in water samples of higher ionic strengths. However the effectiveness of an addition of MIBC was weakened in these solutions. It was also established that the water samples with higher ion content produced smaller bubbles in a laboratory flotation cell. In contrast to the binary coalescence experiment, the addition of MIBC appeared to be more effective in reducing the bubble size whilst a higher electrolyte concentration is present. The sensitivity of the effects of inorganic electrolytes on the bubble-bubble interactions suggests that coal washeries may benefit in monitoring the quality of the water employed in the flotation circuit.
La Sr Cr Mn Co O (0.1 ≤ ≤ 0.4) catalysts were prepared by the sol–gel method and investigated for the production of hydrogen from simulated coal-derived syngas via the water-gas shift reaction in the temperature range 400–650 °C. Catalyst characteristics were evaluated using XRD, BET, SEM–EDS and TPR. The La Sr Cr Mn Co O ( = 0.1–0.3) catalysts shows high CO conversion of 90% at 450 °C compared to the commercial HT–WGS catalyst and maintains high activity at higher than 450 °C. Therefore, the most suitable catalyst for the WGS reaction in simulated coal-derived syngas was found to be La Sr Cr Mn Co O .
Textural features of 25 worldwide coals were studied after slow oxidation processing (0.5 °C min from 20 to 250 °C in air) using oil immersion microscopy and image analysis techniques. The characterization of samples, before and after oxidation, showed important changes in vitrinite reflectance with high reactive coals, which also related to their intrinsic self-oxidation potential. The morphology of the coal particles was also altered after the oxidation, to produce at least six different morphotypes. Particles with ‘homogeneous change of reflectance’ and particles with ‘oxidation rims’ were predominant in the samples studied, which related to boundary reactive conditions (kinetic and diffusion control of the reaction respectively). These textural characteristics indicate how particles interacted with oxygen at low temperatures, which could be used to predict the most probable pathway during the early stages of oxidation which could then lead to a spontaneous combustion event. The magnitude of the reflectance change and the morphological characteristics of samples studied were also related to the reactivity properties, providing an additional source of information to identify coals prone to spontaneous combustion.
Charcoal briquettes are inexpensive solid fuels made from carbonized biomass. The potential of converting water hyacinth (Eichhornia crassipes) charcoal into briquettes with molasses as binder was investigated in this study. Dried water hyacinth was carbonized at a temperature between 350 degrees C to 500 degrees C in a fabricated fine biomass carbonizer. A solution containing 80% by weight molasses was used in the production of briquettes having different charcoal/molasses ratios of 40:60, 30:70, and 20:80. Each briquette was characterized in terms of bulk density, calorific value, compressive strength, proximate analysis and micro-structure by Scanning Electron Microscopy. Charcoal briquettes were tested for their flammable characteristics through their burning rates and ignition time. Altering the molasses to charcoal ratio affected the quality and characteristics of the briquettes. Volatile combustible matter and fixed carbon increased with increasing amount of binder while ash content decreased. The 30:70 charcoal/molasses ratio produced the highest calorific value (16.6 MJ/kg) and compressive strength (19.1 kg/cm(2)). The results have shown the potential of converting water hyacinth into an alternative fuel source.