Effect Of Coal Properties Research Articles

Reservoir Simulator For Improved Recovery Of Coalbed Methane (Icbm) Part Ii : Effect Of Coal Matrix Swelling And Shrinkage

Sequestration of CO2 in deep unmined coal seams is currently under development for improved recovery of coalbed methane (ICBM) as well as permanent storage of CO2. Recent studies have shown that CO2 displaces methane by adsorbing more readily onto the coal matrix compared to other greenhouse gases, and could therefore contribute towards reducing global warming. In order to carry out a more accurate assessment of the potential of ICBM and CO2 sequestration, field based numerical simulations are required. Existing simulators for primary CBM (coalbed methane) recovery cannot be applied since the process of CO2 injection in partially desorbed coalbeds is highly complex and not fully understood. The principal challenges encountered in numerical modelling of ICBM/CO2 sequestration processes which need to be solved include: (1) two-phase flow, (2) multiple gas components, (3) impact of coal matrix swelling and shrinkage on permeability, and (4) mixed gas sorption. This part II of this two-part paper series describes the development of a compositional simulator with the impact of matrix shrinkage/swelling on the production performance on primary and echanced recovery of coalbed methane. The numerical results for enhanced recovery indicate that matrix swelling associated with CO2 injection could results in more than an order of magnitude reduction in formation permeability around the injection well, hence prompt decline in well injectivity. The model prediction of the decline in well injectivity is consistent with the reported field observations in San Juan Basin USA. Also, a parametric study is conducted using this simulator to investigate the effects of coal properties on the enhancement of methane production efficiency based on published data.

Prediction of coke CSR using time series model in Coke Plant

Coke is raw material for blast furnace for production of hot metal. Good quality raw material produces low cost hot metal and one of the important quality parameter for blast furnace is Coke Strength after Reaction (CSR), as it refers to coke “hot” strength, generally a quality reference in a simulated reaction condition in an industrial blast furnace. In this research, the effects of coal properties and process parameters on the Coke CSR were studied by Time Series forecasting and artificial neural network models. In this method, historical data of last 3 years was used to estimate the CSR value. In this investigation, thirty-four input parameters such as moisture, volatile matter, ash, fluidity, battery temperature etc. were used. An Unobserved Component Model of Time Series was found to be optimum with nine parameters of coal properties and other process parameters with maximum accuracy of 76%, on the validation dataset respectively. The operating range of coal properties and controllable process parameters is derived from model developed to operate for consistent Coke CSR of 65.5% and above. The potential saving from this modelling initiative is INR 120 Million/USD 1.75 Million.

Influencing factors and mechanisms involved in the ignition of low-rank coal: Implications for spontaneous combustion

Understanding the ignition mechanism of spontaneous combustion is critical for preventing it. In this work, the effects of different test conditions including oxygen concentration, heating rate, oxidation carrier gas flow rate, and sample amount on the ignition temperature were studied with a thermal gravimetric analyzer. Further, the effects of coal properties on the ignition temperature were also investigated using 15 different low-rank coals. A heterogenous ignition model was proposed that small amount of active species is the key material leading to ignition. The heterogenous ignition mechanism well explained the complex effects of test conditions and coal properties on the ignition temperature of low-rank coal. Finally, an empirical formula for predicting the ignition temperature was derived for the rapid assessment of the spontaneous combustion potential.

Effect of coal properties on the strength of coke under simulated blast furnace conditions

Eight cokes made from coals/blend with different properties (vitrinite mean maximum reflectance = 0.90–1.66, logarithm Gieseler maximum fluidity = 4.16–1.30) were subjected to gasification and annealing simulating the conditions within an ironmaking blast furnace (BF). The specific methodology utilised included gasification of coke with BF gas-temperature profile from 900 to 1400 °C (corresponding from the thermal reserve zone to the cohesive zone) and annealing of coke up to 2000 °C (corresponding to the raceway region). The coke microstrength and macrostrength were determined using ultra-micro indentation and tensile test to understand the effect of coal precursor properties on the strength of the resulting coke and the changes when processed under the simulated BF conditions. Under the high temperatures in the simulated BF processes, the cokes from different coals showed significant differences in their properties, even though most of them had similar Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) values. Coke microtextures experienced significant reflectance loss and structure change upon simulated BF gasification and annealing conditions. The decreases in mean maximum reflectance and bireflectance were more severe for the coke produced from the high rank coal. The cokes made from coals with higher rank and lower Gieseler maximum fluidity exhibited greater change in their microstructure upon high temperatures. As a result, microstrength of cokes produced from these coals decreased more than that of coke made from the parent coals with a lower rank and higher Gieseler maximum fluidity; this tendency was more significant in the Reactive Maceral Derived Components (RMDC) than Inert Maceral Derived Components (IMDC) microtextural type. Degradation of macrostrength of cokes produced from coals with higher rank and lower maximum fluidity was also more severe due to the greater decrease in their microstrength.

Effects of Coal Rank and High Organic Sulfur on the Structure and Optical Properties of Coal‐based Graphene Quantum Dots

Coal‐based graphene quantum dots (GQDs) were successfully produced via a one‐step chemical synthesis from six different coal ranks, from which two superhigh organic sulfur (SHOS) coals were selected as natural S‐doped carbon sources for the preparation of S‐doped GQDs. The effects of coal properties on coal‐based GQDs were analyzed by means of high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), ultraviolet‐visible (UV‐Vis) absorption spectroscopy, and fluorescence emission spectra. It was shown that all coal samples can be used to prepare GQDs, which emit blue‐green and blue fluorescence under ultraviolet light. Anthracite‐based GQDs have a hexagonal crystal structure without defects, the largest size, and densely arranged carbon rings in their lamellae; the high‐rank bituminous coal‐based GQDs are relatively reduced in size, with their hexagonal crystal structure being only faintly visible; the low‐rank bituminous coal‐based GQDs are the smallest, with sparse lattice fringes and visible internal defects. As the metamorphism of raw coals increases, the yield decreases and the fluorescence quantum yield (QY) initially increases and then decreases. Additionally, the surface of GQDs that were prepared using high‐rank SHOS coal (high‐rank bituminous coal) preserves rich sulfur content even after strong oxidation, which effectively adjusts the bandgap and improves the fluorescence QY. Thus, high‐rank bituminous coal with SHOS content can be used as a natural S‐doped carbon source to prepare S‐doped GQDs, extending the clean utilization of low‐grade coal.

Effect of particle properties on the energy-size reduction of coal in the ball-and-race mill

Breakage behaviors and energy consumed characteristics of coal are directly influenced by properties, such as particle size, ash content or density. It is essential to model these effects and conduct quantitative evaluation. In this study, samples of 4 particle sizes × 4 ash contents were ground in a Hardgrove mill for 9 energy levels, respectively. Breakage rate of particles in the top size and t10 were determined and effects of coal properties on two parameters were also discussed. Though the relation between consumed energies and t10 of each sample can be described by classical breakage model, experimental data of all samples were scatter. In this case, particle size and ash content were modelled into breakage equation in exponential term, namely t10 = A × (1 − e−b∙x∙Ecs/eYa). This modified model gave good fitting results to experimental data. Introduce of coal properties into energy-size reduction model helps to compare grinding energy efficiency of various coals. Confidence analyses of repeat experiments demonstrated the repeatability of test results and indicated the reliability of new breakage model.

Effects of coal properties on ventilation air leakage into methane gas drainage boreholes: Application of the orthogonal design

Ventilation air leakage into underground to inseam drainage boreholes is a common issue observed during gas drainage in underground coal mines. This air leakage adversely affects the gas drainage efficiency. Despite the extensive research conducted on air-leakage prevention strategies, the effects of coal properties on the air leakage has not yet been properly investigated. This paper presents a fully-coupled numerical study on the effects of coal properties such as Young's modulus, Poisson's ratio and porosity on the air leakage into drainage boreholes. This was achieved through an integrated approach of the orthogonal design method and the F-test theory. The results show that there is a direct correlation between the Young's modulus and the amount of air leakage. Furthermore, the F-test theory was used to examine the significance of the above-mentioned properties' effects. It is found that the impact of Young's modulus on the air leakage is the most significant among those three properties. The Poisson's ratio is the next significant factor with an inversely proportional relationship. Porosity is found to have the least effect on the air leakage. This study provides a systematic approach to examine the air leakage performance for various site conditions and coal properties. Research outcomes offer the mining researchers and engineers a guidance to develop appropriate leakage-prevention strategies and enhance gas drainage performance.

An approach for utilization of direct coal liquefaction residue: Blending with low-rank coal to prepare slurries for gasification

Direct coal liquefaction residue (DCLR) is a main byproduct in direct coal liquefaction process and its clean and high-efficient utilization is important. If DCLR could be gasified for hydrogen production, it will compensate hydrogen consumption during liquefaction and lower the operation cost, which makes DCLR utilization more promising. We proposed to blend DCLR with low-rank coals to prepare DCLR–coal–water slurries (DCLRCWS) as feedstock for gasification. In this work, one DCLR and four low-rank coals were used to prepare the individual DCLR–water slurries (DCLRWS), coal water slurries (CWS) and the mixed DCLRCWS at the weight ratio of 1:1. The slurryability, static stability and rheology of various slurries were investigated. The results show that DCLR and the low-rank coals are complementary in terms of slurry properties and DCLRCWS could meet the requirement of gasification process. Adding 50wt.% DCLR apparently improves the slurryability of low-rank coals, and the maximum solid loading (Cmax) of DCLRCWS prepared with ZLNR coal and DCLR is about 10% higher than that of the corresponding CWS. The effects of coal properties, dispersant adsorption, zeta potential on preparation of highly loaded slurries were examined in terms of slurryability. Moreover, compared with DCLRWS, DCLRCWS display higher degree of pseudoplasticity and better static stability owing to the addition of low-rank coals.

Effects of coal properties on the production rate of combustion solid residue

Abstract The production rates of furnace bottom ash in a pulverized coal-fired power plant were monitored for a two-year period and its variations with respect to coal properties were analyzed. The power plant was originally designed to fire the coal sludge generated from a washing process; however, the coal sludge and its mixture with low-rank bituminous coal have been started to be used as the main fuel with time. The results of the hardgrove grindability measurements have shown that the grinding properties of sludge or its mixtures could not be predicted based on proximate analysis (moisture, ash, carbon and volatile contents); it could only be determined by experiments. The production rate of bottom ash in this particular power plant remained relatively insensitive to the high ash and moisture contents and could be estimated almost only by knowing the calorific value of the source coal. The evaluated dependency was linear.

Effect of coal properties on CO 2 sorption capacity under supercritical conditions

Relationships between coal properties and CO 2 sorption capacity have been investigated for 30 coals from various sources in Australia and elsewhere, selected to cover a wide range of rank and maceral composition. Samples were characterised by their CO 2 sorption capacity, porosity, density and chemical and petrographic composition. Carbon dioxide adsorption isotherms were measured on dry coal at 53 °C and at pressures up 16 MPa using a gravimetric apparatus. Isotherms were fitted to a modified Dubinin–Radushkevich (DR) model using gas density rather than pressure to enable the model to be applied to supercritical conditions. A term related to Henry's Law to account for gas absorbed by the coal is also included in the model. This model provided excellent fits to the experimental data; in most cases the difference between the predicted and measured value was less than 1% of the sorption capacity over the entire pressure range. Sorption capacities of the coals investigated were found to vary by over a factor of 2, even when comparing on a dry-ash-free basis. Carbon dioxide sorption capacity tended to reduce with rank to reach a minimum that corresponded to a vitrinite reflectance of about 1.2% after which it began to increase. Increasing hydrogen content tended to result in a decrease in sorption capacity. Two of the coals showed significantly higher sorption capacity than any of the other samples examined. In both of these cases, the coals had been naturally weathered and exhibited high porosity relative to the other samples. In general, however, the correlations observed were quite weak with considerable scatter in the data. This implies that CO 2 sorption capacity, required for assessing sequestration potential, cannot be reliably inferred from the coal properties investigated here.

Devolatilization and Cracking Characteristics of Australian Lumpy Coals

An experimental study was conducted to investigate the devolatilization characteristics of five Australian coals in a thermogravimetric analysis (TGA) reactor by varying the coal lump size and the temperature. The swelling ratio was measured after thermal treatment of coal lumps in a horizontal tube furnace at 1273 K while the cracks generated in the lumpy char samples were examined using scanning electron microscopy (SEM). Physical and chemical properties of coal and char samples were measured using CO{sub 2} gas adsorption, Hg porosimetry, X-ray fluorescence (XRF) and X-ray diffraction (XRD). Under all the tested conditions, the total volatile yield of lumpy coals was found to be not influenced by either the temperature or particle size and was similar to that indicated in proximate coal analysis. However, as expected, the devolatilization rates were found to increase with increasing temperature as well as the increasing amount of volatiles present in the coal. The study further demonstrated that the effect of coal properties on the devolatilization rates of lumpy coals may not be significant as the rates decrease with increasing lump size, such that coal lumps with sizes more than 10 mm indicated similar orders of reaction rates. The apparent activation energy of coalmore » lumps indicated a linear correlation with the stack height of the carbon crystallite of coals. The study demonstrated that the cracking and swelling behavior of coals was influenced by physical as well as chemical properties, particularly their modification during devolatilization conditions. The study showed that coals with low volatiles indicated high cracking which would increase further with increasing lump size in accordance with the size effect. The cracking tendency of coals appeared to have a reciprocal association with swelling tendency such that less swelling coals are more vulnerable to cracking. 33 refs., 13 figs., 3 tabs.« less

Mercury Capture on Fly Ash and Sorbents: The Effects of Coal Properties and Combustion Conditions

The US fleet of coal-fired power plants, with generating capacity of just over 300 GW, is known to be a major source of domestic mercury (Hg) emissions. To address this, in March 2005, the Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR) to reduce emissions of mercury from these plants. It is generally believed that most of the initial (Phase I) mercury reductions will come as a co-benefit of existing controls used to remove particulate matter (PM), SO2, and NOX. Deeper reductions in emissions (as required in Phase II of CAMR) may require the installation of mercury-specific control technology. Duct injection of activated carbon sorbents is the mercury-specific control technology that has been most widely studied and has been demonstrated over a wide range of coal types and combustion conditions. The effectiveness of the mercury control options (both “co-benefit control” and “mercury-specific control”) is significantly impacted by site-specific characteristics such as the combustion conditions, the configuration of existing air pollution controls, and the type of coal burned. This paper identifies the role of coal properties and combustion conditions in the capture of mercury by fly ash and injected sorbents.

Binderless briquetting of some selected South African prime coking, blend coking and weathered bituminous coals and the effect of coal properties on binderless briquetting

The binderless briquetting of some selected South African prime coking and blend coking coals, as well as the effects of weathering on the binderless briquetting of some inertinite-rich bituminous coals, were investigated in the laboratory. Selected properties of these coals were determined and the coals were briquetted at various moisture contents and pressures. Based on the results obtained in this study, binderless briquetting was found to be most successful in the cases of the fresh, vitrinite-rich coking and blend coking coals and satisfactory in the fresh inertinite-rich Witbank coals. However, the bonding process seemed to be adversely affected by weathering. The negative impact on bonding could be ameliorated to some extent by the presence of a significant kaolinite content when the percentage ash reports in the order of more than 15% (air-dry basis). It should, however, be noted that kaolinite may reduce the water resistance of the briquettes.

Application of percolation model to particulate matter formation in pressurized coal combustion

Coal is an important energy resource for meeting the future demand for electricity, as coal reserves are much more abundant than those of other fossil fuels. In this study, the percolation model, which can account for swelling due to devolatilization and ash agglomeration, is applied to particulate matter formation process in coal combustion, and the effects of coal properties, ambient temperature, ambient pressure and initial coal size on the characteristics of a burning coal particle are studied. The devolatilization rate of coal is given by the first-order reaction model with FLASHCHAIN ® model [Niksa, S., Combust. Flame, 100, (1995) 384–394.]. The characteristics of a burning coal particle are investigated under the atmospheric and high pressure conditions. The results show that in the atmospheric pressure condition, the characteristics of the burning coal particle obtained by the percolation model are in general agreement with the experimental data. The particle diameter of Newlands coal with higher fuel ratio and ash content is larger than that of Plateau coal in the char-combustion-dominant process. As the ambient temperature increases, the particle diameter becomes small in the early stage of the char-combustion-dominant process, but becomes large afterward. The porosity in the char-combustion-dominant process decreases with decreasing the initial coal size. It is also observed that the effect of ambient pressure is prominent in the char-combustion-dominant process. The particle diameter and porosity in the pressurized condition are greater than those in the atmospheric pressure condition. These behaviors can be explained by the interaction between char reaction and ash agglomeration.

Effect of Coal Properties on HCN and NH3 Release During Coal Pyrolysis

The formation of HCN and NH 3 from fuel nitrogen during pyrolysis was studied in a prefilled reactor system with slow (temperature-programmed) heating and in a drop-in reactor system with a rapid heating rate. The experimental results indicate that the formation of HCN and NH 3 is obviously affected by coal properties. The effects of these coal properties vary with the heating fashion. Coal rank, characteristic of char residue, surface characteristics, and composition of the coal are important factors influencing the formation of HCN and NH 3 during pyrolysis.

COAL PROPERTY EFFECTS ON N2O AND NOx FORMATION FROM CIRCULATING FLUIDIZED BED COMBUSTION OF COAL

ABSTRACT The effects of coal properties on N2O and NOx formation from circulating fluidized bed combustion of coal was examined through burning nine typical coals and a coal shale, widely used in China over a wide range of coal ranks, in a bench-scale circulating fluidized bed. It was found that N2O and NOx formation had similar dependence on coal rank. Fixed carbon content and nitrogen content were the most important coal properties to influence N2O and NOx emissions from circulating fluidized bed combustion of coal. A coal with high fixed carbon content had high conversion ratio of fuel-N into N2O and NOx. The conversion ratio of fuel-N into N2O or NOx increased with nitrogen content of coal, whereas it decreased with O/N ratio. No significant correlation between conversion ratio of fuel-N into N2O or NOx and C/N ratio was identified. To clarify the coal property effect, investigation of a wide range of coal rank, is important.

Theoretical Study of Coal Gasification in a 50 ton/day HYCOL Entrained Flow Gasifier. I. Effects of Coal Properties and Implications

A three-dimensional computational fluid dynamics simulator was developed to study hydrogen-from-coal (HYCOL) coal gasification theoretically. The simulator developed has satisfactory sensitivity to various coal properties, including C/H ratio, C/O ratio, volatile matter content, ash content, heating value, and particle size when simulating coal gasification in an oxygen-blown HYCOL gasifer. Among the coal properties investigated, the heating value had a strong influence on the gasification characteristics of a HYCOL gasifier, whereas the influence of particle size was limited, suggesting a very likely reaction regime of chemical reaction control in the gasification process. The trajectory and temperature distribution were quite different for particles of different sizes, which may be useful information to avoid ash slagging in the gasifier.

04/01583 The effect of diesel fuel on common vetch ( Vicia Sativa L.) plants : Adam, G. and Duncan, H. Environmental Geochemistry and Health, 2003, 25, (1), 123–130

The advanced reburning process for NOx emission control was studied in a down-fired 20 kW combustor by evaluating the performance of 15 pulverised coals as reburning fuels. The proximate volatile matter contents of the coals selected ranged from around 4 to 40 wt% (as received) with elemental nitrogen contents from around 0.6 to 2.0 wt%. The effects of reburn fuel fraction, reburning zone residence time, ammonia agent injection delay time (relative to the reburn fuel and burnout air injection points) and the nitrogen stoichiometric ratio are reported in detail and the optimum configurations for advanced reburning, established as a function of operating condition and coal type. The experimental results show that advanced reburning can reduce NOx emissions up to 85%. The maximum benefits of advanced reburning over conventional reburning were observed at the lower reburn fuel fractions (around 10%). The results demonstrate that under advanced reburning conditions equivalent or higher levels of NOx reduction can be achieved while operating the reburn zone closer to stoichiometric conditions compared with conventional reburning operating at high reburn fuel fractions (20–25%). Thus the practical problems associated with fuel-rich staged operation can be reduced. The effect of coal properties on the advanced reburning performance was also investigated. As with conventional reburning, the fuel nitrogen content of the coal used was found to have little influence on the NOx reduction efficiency except at the highest reburn fuel fractions. There was, however, a strong correlation between the effectiveness of advanced reburning and the volatile content of the reburning fuels, which not only depended on the reburn fuel fraction, but also the mode (rich or lean) of advanced reburning operation. These parameters are mapped out experimentally to enable the best operating mode to be selected for advanced reburning as a function of the reburning fuel fraction and volatile content.

03/02099 Effects of coal properties on recycled-NO x reduction in coal combustion with O 2/recycled flue gas : Hu, Y. Q. et al. Energy Conversion and Management 2003. 44, (14), 2331–2340

03/02099 Effects of coal properties on recycled-NO x reduction in coal combustion with O 2/recycled flue gas : Hu, Y. Q. et al. Energy Conversion and Management 2003. 44, (14), 2331–2340

Effects of coal properties on recycled-NO x reduction in coal combustion with O 2/recycled flue gas

The emission of NO x and the reduction of recycled-NO x in coal combustion with O 2/recycled flue gas were experimentally studied in an electrically heated up flow combustor under low recycling ratio with three kinds of coal: a high volatile bituminous, a medium volatile bituminous and a semi-anthracite. The recycled flue gas was simulated with the mixture of CO 2 and NO x . NO x emissions from the combustion of the three coals were firstly investigated under the recycling ratio ranging from 0 to 0.4 but without recycled-NO x . The results show that the relative release rate of fuel-nitrogen to volatile matter and the partitioning of volatile-N and char-N are more critical than volatile matter content and nitrogen content in coal for NO x emissions, especially in the fuel lean combustion. The experimental data on recycled-NO reduction indicate that the reduction efficiency increased with fuel equivalence ratio and recycling ratio. In the fuel rich region, the reduction efficiency reached as high as 80% at a fuel equivalence ratio of 1.4. The experiments on the replacement of NO recycle by NO 2 recycle indicated that the same reduction efficiencies of recycled-NO 2 as those of recycled-NO were reached for the high volatile bituminous, while the reduction efficiencies of recycled-NO 2 were always lower than those of recycled-NO for the semi-anthracite coal.