Coal Powder Research Articles

Investigation into the ignition of coal powders in the presence of oxygen and natural gas by means of high-speed cinematography

The mixtures of soot or graphite powder with a stoichiometric mixture of natural gas and oxygen intensely ignite at lower initial temperatures, as compared with that for powder–gas mixtures of coal powders with the above mixture of natural gas and oxygen.

The regeneration of waste foundry sand and residue stabilization using coal refuse

The processes for recycling waste foundry sand are divided between regeneration and beneficial reuse, and the potential for regeneration is higher than that of reuse. In this study, two processes for the recycling and residue stabilization of waste foundry sands were considered. One is the dry mechanical process for recycling, and the other is the stabilization process for powdered residue. The dry mechanical process of regeneration consists of crushing, grinding, separation, and classification. To stabilize the residues that were generated through the regeneration process, powdered residues were pelletized by a high-shear pelletizer, and the surfaces of the pellets were subsequently coated with coal refuse powders that contained sodium silicate as a binder. Coated pellets were sintered by a self-propagating combustion method. The refractory index of the recycled sands, as measured by the Seger cone method, was over −34, and their SiO 2 contents of 94% was similar to that of green sand. The general conclusion that coal refuse and sodium silicate stabilize heavy metals better than other processes may lead to the development of a cost-effective solution for stabilizing heavy metals in residues.

Comparative effects of different soil amendments on amelioration of saline-sodic soils

  A greenhouse experiment was conducted to test the potential of different soil amendments in saline-sodic soils reclamation; to affect the growth response of alfalfa (Medicago sativa L.) plants grown on two saline-sodic soils; and to evaluate the comparative efficiency of different soil amendments for their effects on salinity, sodicity, and pH levels of the soils. To achieve these objectives, two highly saline-sodic soils were selected (Abees, Typic torrifluvents and Elhammam, Typic calciorthids). Different soil amendments were used (compost, anthracite coal powder, water treatment residuals, ferrous sulphate, and a combination of them). The results of the study indicated that pH of Elhammam soil was less affected than pH of Abees soil after the amendment application because of the high calcium carbonate content which acted as a buffer and resisted any appreciable change in soil pH in the alkaline range. The positive effects of all treatments followed the order: T16 > T12 > T13 > T14 = T5 > T11 = T15 > T7 > T8 > T4 = T6 > T9 = T10 > T2 >T3> T1 >T0. The most effective amendment in reducing SAR<sub>e </sub>in the experimental soils was T16. This was due to the presence of Al in WTRs and Fe in ferrous sulphate which enhanced the leaching process, and the presence of high adsorptive capacity materials like WTRs and compost which adsorb more sodium. The positive effects of all treatments for reducing SAR<sub>e</sub> in Abees soil followed the order: T16 > T15 > T14 > T13 > T11 > T12 .While, in Elhammam soil, the order was: T16 > T15 > T14 > T13 = T11>T12 = T5. The removal sodium efficiency (RSE) or percentage of Na-removed from the soils at the end of the experiment was significantly reduced after the application of the amendments. RSE of T16 proved the highest value (76%) among the treatments for the two soils used, followed by T15 and T14. The yield of biomass at T16 significantly increased, the increase being 959% in comparison with T0 in Abees soil, while the increase in biomass yield was 1452% in comparison with T0 in Elhammam soil. However, field tests are necessary to draw the final conclusions.

Gas Upgrading in a Downdraft Fixed-Bed Reactor Downstream of a Fluidized-Bed Coal Pyrolyzer

A new two-stage gasification process, consisting of a fluidized-bed (FB) pyrolyzer and a downdraft fixed-bed (DFB) gasifier, has been proposed to gasify powder coal for fuel gas production with low tar generation. Aiming at developing the new technology, this paper investigated the means for coal pyrolysis gas upgrading, with the focus on tar removal by both thermal cracking with or without the presence of oxygen and catalytic cracking or reforming over a char bed in a fixed-bed reactor downstream of a FB coal pyrolyzer. The presence of oxygen and the adoption of a char bed evidently facilitated the tar removal performance and also improved the produced fuel gas quality. Analyzing the tar sample collected at the outlet of the tar removal reactor with gas chromatography-mass spectrometry (GC-MS) clarified that the oxidation by O(2) and the char-catalyzed reforming both exhibited certain selectivity to the tar-containing chemical species. In addition, the property of char played an important role on its catalytic activity. The higher the specific surface area, the better the activity of char for removing tar. The spent char showed a much reduced specific surface area of micropores but evidently elevated the specific surface area of mesopores, even by up to 3 times. The tests with the metal oxides impregnated onto the demineralized char demonstrated that both Ca and Fe oxides enabled better catalytic activity for tar removal than Na and Mg oxides. This study clarified as well that the viable operating conditions for tar removal in a char bed were at 1100 degrees C with an excessive air ratio (ER) of 0.04 and gas residence time above 1.3 s.

Preparation and Performance Characterization of Active Coal Gangue Powder (ACGP) Used for Cement Admixture

Two kinds of high active coal gangue powder (ACGP) were prepared by heat treated and ball milled coal gangue. The density, fineness, Loss on ignition (LOI), activity and influence of the fineness of the two kinds of ACGP on the density and I/W (compressive strength to weight of the foam concrete specimens) of foam concrete were also studied in this paper. The results show that the density and I/W of the foam concrete were greatly affected by the fineness of ACGP. The finer of the ACGP, the lower density and higher I/W of the coal gangue foam concrete will be got. Based on the experimental results, a method to evaluate the activity of active powder used for cement admixture is proposed and the activity of the ACGP is also evaluated.

Effect of Bentonite on Properties of Fly Ash-Based Porous Ceramics

Recycling fly ash in a way with high benifits is important to environmental conservation and sustainable development. Using bentonite as binder and coal powder as pore-forming agent, the fly ash-based porous ceramics was prepared and effects of bentonite on performances of the ceramics were researched. With the increasing of bentonite content from 3.0mass% to 5.0mass%, liquid phase sintering process was promoted and the bending strength improved from 5.46 to 6.09Mpa. Contrarily, the open porosity decreased from 48.18% to 44.39%. But more bentonite addition would result in some larger pores distributed inhomogeneously in the microstructure so that the bend strength fell down and porosity went up.

Study on Ultra-Fine Grinding and <i>In Situ</i> Modification of Taixi Super-Low-Ash Anthracite

Abstract. This paper discussed the ultra-fine grinding and in-situ modification of Taixi super-low-ash anthracite in stirred mill. Particle size distribution of the products was determined by laser particle size analyzer. The surface morphology and dispersion of the powder were detected by scanning electron microscopy (SEM), and surface structure of the modified powder was measured by Fourier transformation infrared (FTIR). It was found that the optimum ultrafine grinding time is 70 min in the stirred mill, the suitable maleic anhydride (MAH) dosage was 1 wt% of the ground coal powder, MAH can play roles in grinding aid and modifier. On these conditions, both the grinding and dispersion effect are the best.

Coal powder measurement by digital holography with expanded measurement area

The field of view of digital in-line holography for flow field diagnostics is restricted to a small volume due to the finite size and the low spatial resolution of the available CCD. Expansion of the measurement cross section of digital holographic particle image velocimetry was investigated with a lens-based holography configuration. By sampling the chirp signal in the center lobe completely and undersampling the chirp signal in the second- and higher-order lobes by a magnified virtual recording plane produced by an imaging camera lens, the field of view is expanded. Simulation results show that the three-dimensional (3D) location and size of the relatively large particle can be reconstructed with good accuracy. A digital holographic particle image velocimetry system was established for coal particle flow field diagnostics. Compared with the lensless configuration, the field of view of the digital holography system was enlarged 1.9 times, up to 2.78 cm × 2.78 cm × 3 cm. The 3D location, size distribution, and the 3D vector field of coal powder were obtained. The results show that the application of digital in-line holography to measure large particle flow field is feasible.

Burning Blended Coal of Indonesia Lignite and Vietnam Anthracite on a Face-Fired 600MW Boiler Original Designed for Bituminous Coal

Elemental research of burning blended coal of Indonesia Lignite and Vietnam anthracite on a face-fired 600MW supercritical boiler is performed, which is original designed for burning high-quality bituminous coal. Maximum ratio of Vietnam anthracite can be 40 percent. With the increase of the ratio of the anthracite, the size of residue particles and the ratio of unburned carbon in residues (UBCRs) rise up markedly, the slag formation of Indonesia Lignite alleviate. The results reveal: the burnout of anthracite is more difficult than its ignition, the key way to solve this problem is to control Fineness of Pulverized Coal Powder (FPCP) of the blended coal according requirements of anthracite, but to control the Primary Air (PA) outlet temperature of mill and the mass ratio of PA to coal as flammable coal Lignite. Besides, Secondary Air (SA) Distribution mode of Centralized Oxygen Feeding(COF), Big Swirl Intensity also have obvious effects the combustion of blended coal.

Renovation Design of Coal Powder Conveyor Bearing Support

The bearing support breakage of screw coal powder conveyor in power plant boiler went through four stages: axial displacement of shaft sleeve, shaft sleeve wearing by shield ring and by bearing, and the wearing of skeleton seal rings and dustproof felts by shaft sleeve. By analyzing the wearing characters of each part, the renovation structure was designed. The bearing settled style was changed from using shield ring to using locknut by designing convex sidestep on the shaft sleeve, preventing the axial from drifting. Substituting for the welding assembly, the bolt connecting between the covers and the bearing support body was selected to replace the worn sealing materials easily in dismantling and installing. Good operating effects were achieved after the renovation of the coal powder conveyor bearing support, in the screw coal powder manufacturing line of 100MW power plant boiler, there was no line vibrating, coal leaking, noising and line locking, having decreased the repairing cost greatly and insuring the safety and stable electric power producing.

Determination of contact angle on the coal surface

The paper considers the method for determining a contact angle of coal surface prepared by pressing the coal powder into cylindrical pellets of a target size. The authors analyze the relationships between the contact angle and chemical properties of coal surface.

CFD study of in-furnace phenomena of pulverised coal injection in blast furnace: Effects of operating conditions

A three-dimensional mathematical model of the flow and combustion of coal powder in a coke packed bed has been developed to simulate the complicated in-furnace phenomena of pulverised coal injection (PCI) in the raceway and the surrounding coke bed in an ironmaking blast furnace. The model includes the flow–thermal–chemical behaviours of two fuels: (i) coal powders; and (ii) coke solids. The typical in-furnace phenomena of the base case are obtained by means of this model in terms of flow and combustion behaviours of coal powder. An array of parametric studies are carried out to evaluate the effects of operating conditions under practical conditions, including blast conditions and types of cooling gas. The results show that these operating conditions play a limited role in improving the burnout at the endpoint of the raceway but a notable role in the recirculation region, i.e. over the raceway surface. Gas composition is sensitive to oxygen enrichment and use of oxygen as cooling gas. The results are then compared to the previous studies. The underlying mechanisms are explored. It is indicated that this study can provide more useful information for optimising the PCI operation in full-scale blast furnaces.

Effect of the addition of cornstalk to coal powder/coal tar combustion

Thermogravimetry (TG) and differential thermal analysis were used to investigate combustion behavior with the addition of cornstalk to coal powder and coal tar at three different heating rates: 5, 10, and 15 °C min−1. Different reaction kinetic mechanisms with the classical Arrhenius model were used to treat TG data. The first-order combustion model fitted the data well. The combustion characteristics of the two masses were analyzed according to combustion characteristics parameters such as ignition temperature, peak temperature at maximum weight loss rate, and burnout temperature, among others. By calculation, a uniform trend of decreasing activation energies was observed with the addition of cornstalk. The rate of coal powder and coal tar combustion process was also greatly improved.

Effect of coal gangue-fly ash ceramic (CFC) media on municipal wastewater treatment in a pre-denitrification biological aerated filter

Coal gangue-flyash ceramic (CFC) is a novel media, which is made up of flyash, coal gangue powder and some kinds of additive. In this study, CFC was used as filter medium for a pre-denitrification biological aerated filter (BAF) to treat municipal wastewater. The performances of the two pilot-scale pre-denitrification BAF systems were monitored for 3 months to compare the effect of CFC media with expanded clay media as BAF medium. In terms of started-up speed, the efficiency of the system with expanded clay media was slightly faster than that with CFC media. In terms of removing chemical oxygen demand (COD), ammonia (NH4+-N) and total nitrogen (TN), the efficiency of the system with CFC media almost could rival with expanded clay media. The average COD, NH4+-N and TN concentrations in the effluent were average 47.0 mg/L, 4.0 mg/L and 14.8 mg/L when HRT was 4 h, which were all up to the National Discharge Standard of Level 1-A (GB 18918-2002) in China. So it is feasible for CFC media to be applied as the media of BAF.

Detonation of a coal-air mixture with addition of hydrogen in plane-radial vortex chambers

Results of an experimental study of continuous and pulsed detonation of a coal-air mixture with addition of hydrogen in plane-radial vortex chambers 204 and 500 mm in diameter are presented. The tested substance is pulverized activated charcoal. A method of coal powder supply through narrow channels by means of adding the gas at the injector entrance is found. Stable regimes of continuous spin detonation with one or two transverse detonation waves moving with velocities of 1.8–1.6 km/sec are obtained for the first time in the combustor 204 mm in diameter. The frequency of pulsed detonation with radial waves is 4–4.8 kHz. The limits of continuous detonation in the combustor 500 mm in diameter are extended: regimes of continuous spin detonation with a large number (5–8) of transverse waves moving with velocities of 1.8–1.5 km/sec are obtained, the amount of hydrogen added to coal is reduced to 2.8%, and combustion of coarser fuel particles is ensured owing to an increased residence time of the mixture in the combustor. The wave structure and the flow in the vicinity of the waves are reconstructed in the combustor plane.

Efecto del tipo y concentración de aglutinante en la conductividad térmica de polvos de carbón

<span>Se reporta la conductividad térmica (k) a temperatura ambiente de polvos de carbón térmico, en función del tipo y concentración del aglutinante (agua, alcohol, ACPM), los cuales variaron de porcentaje en peso (%wt), entre 5% y 40%. Las muestras fueron obtenidas de la mina Cerro Tasajero ubicada en el área metropolitana de San José de Cúcuta, Colombia, las cuales se pulverizaron manualmente, utilizando molino de rodillos y se tamizaron en malla pasante número 100 (150 ¿m). k se determinó, usando el principio físico de flujo lineal transitorio de calor, mediante el sistema KD2¿ Thermal Properties Analyzer (Decagon Devices, Inc). El porcentaje de ceniza presente en la muestra, se determinó según la norma ASTM D3174, y se encontró un valor de 1,75%; para hallar la concentración de azufre, se utilizó la norma ASTM D3177, y reportó un valor de 0,45%, mientras que el porcentaje de materia volátil presente en la muestra fue de 34,17%, que se halló, aplicando la norma ASTM D3175. El análisis de k en función del tipo y concentración del aglutinante, se realizó, usando el ajuste a los datos experimentales mediante la función logística 221])/(1[)(AxxAAyno+¿¿= donde A2 corresponde a los valores de la propiedad térmica (y) para la concentración inicial de aglutinante (x); A1 representa dicho valor para cuando la concentración de aglutinante (x) sea muy grande; xo corresponde al punto donde sucede el cambio de curvatura y n la razón de crecimiento o decrecimiento. Los resultados encontrados en este trabajo, podrán ser utilizados en el desarrollo de estudios que permitan la fabricación de cilindros de polvos de carbón prensados a altas presiones, los cuales se usarán en los procesos de combustión en hornos industriales que se utilizan en la sinterización de productos cerámicos como teja, bloque y baldosa.</span>

Experimental Research on Ultrafine Coal Powder for Methane Adsorption

A new adsorption material technology and its adsorption mechanism were studied in this paper. Anthracite and lignite were taken as raw materials in those experiments. Firstly, the coal was made into different sizes by ball mill then cooked in tube furnace so as to obtain the ultrafine coal material for methane adsorption. Secondly, the ultrafine coal powder which fully adsorbed methane was gone through the gas chromatography analysis to choose the best samples. Finally, the characterization of adsorption and adsorption mechanism were researched by the micro-morphology analysis, thermal analysis, X-ray diffraction analysis, BET surface area-aperture-volume analysis and infrared spectral analysis. The results of experiments showed that the ultrafine lignite powder which mainly consists of microporous, is more suitable for methane adsorption. Under the same treatment condition, the adsorption capacity of lignite series is better than that of anthracite series. After milling for 120 minutes and coking in medium temperature, the lignite could be used as the best material of ultrafine coal powder for methane adsorption.

Ignition of coal powders in the presence of natural gas, oxygen, and reactive admixtures

At elevated temperatures (650–750°C), coating the inner surface of the reactor with coal dust exerts a significant effect on the ignition of hybrid coal-gas mixtures because coal evolves an effective inhibitor of methane combustion upon heating. The hybrid mixtures consisting of a coal powder and a stoichiometric natural gas-oxygen mixture do not ignite in the reactor lined with coal dust.

Liquid Tin-Lead Anode Solid Oxide Fuel Cell Fueled by Coal

Liquid tin-lead alloy, liquid bismuth, and liquid tin-lead-bismuth alloy were investigated as potential anodes for a solid oxide fuel cell powered directly by coal. Power generation from direct oxidation of solid coal was demonstrated with a good stability only in the case when liquid tin-lead anode was used. The tests were carried out at 900 °C under ambient pressure. The open circuit potentials of the SOFC with tin-lead and bismuth anodes operated under nitrogen were compared, and those values were found to correspond to the metal-metal oxide redox potentials for tin and bismuth, respectively. When the SOFCs were fueled by hydrogen, only the tin-lead anode showed a direct electrochemical reaction between hydrogen and oxygen. When 60-mesh coal powder was fed to the liquid tin-lead anode, SOFC showed increase in open circuit potential and generated power from direct electrochemical oxidation of coal.

Budget Estimate Management Information System for Blast Furnace Coal Powder Injection Project

Rapid, accurate and standardized budget estimate is the basis of project bidding, which involves a lot of data information verification and charts. At present, many companies often use the traditional manual method in project budget estimate, which is time-consuming and error-prone. Aiming at the requirements of blast furnace coal powder injection project bidding, this paper developed a blast furnace coal powder injection project budget estimate management information system by using Visual Basic 6.0 and SQL Server database technology, introduced its overall function modules and the key technologies, including system role represent and use case analysis, the system data storage methods, report forms customization methods and so on. Finally, an applied case is given, which can make the project budget estimate conveniently, quickly and accurately, and can reduce the labor intensity of project information management.