Coal Density Research Articles

Analysis of Lignite Character in Inner Mongolia China

The character of indigenous lignite was measured by proximate analysis, ultimate analysis, coal ash analysis, coal true relative density, specific area.et al. The results showed that the internal moisture content is 8-9%, volat ile matter content is more than 45%, the oxygen content is above 20% while the sulphur content less than 0.5%.The main ash content is SiO2 and Al2O3, ash fusion point is above 1200 degree centigrade. The calorific value is between 12∼19MJ/kg. Macropore and mesopore is the pattern in the lignite.

Economic valuation of coal deposits – The value of geological information in the resource recognition process

Resource and economic assessment under uncertainty and risk is quite a difficult process. Many geological, mining, technical and economic aspects should be taken in to consideration simultaneously. The assessment process is also subject to errors, including measurement and interpretation errors and errors resulting from lack of knowledge or over-optimism. Uncertainty about the true value of the geological parameters is reduced as the recognition process and the knowledge about deposits improve. Especially at the first stages of mine development, the information available is insufficient and can lead to incorrect interpretation.In this paper, the impact of geological information on key economic parameters was examined, using the example of a hard coal deposit in mine X in Poland. A scenario analysis was performed, based on a Monte Carlo simulation. The simulation was conducted using ogive distributions and copulas (empirical copulas) binding six geological parameters (coal and waste rock thickness, coal density, coal calorific value (LHV) and sulfur and ash content). To achieve the research purposes, the most popular economic measures (indicators), i.e., IRR, NPV and EBITDA, were used. Finally, differential distributions of these parameters were built and commented upon.The three analyzed scenarios were elaborated considering the data from the geological 3D model of coal deposit X. A polygon (testing) area was defined in the coal field, where complete geological information was available. The first data set (scenario 1) incorporated only information from deep surface boreholes (drillings), the second included data from surface drillings and channel samples and the third used only channel sampling. To interpolate the geological data between boreholes, the inverse distance interpolator was applied.Significant differences in the values of selected economic parameters were obtained; the largest in scenario 1. The average value of the IRR difference distribution (overestimation) was 6.4%; for NPV it was up to 213.7 million PLN and for EBITDA up to 678.6 million PLN in comparison to the reference scenario, or possibly even more. The results achieved are influenced by optimistic estimates of the thickness of coal partings, the amount of coal impurities and finally, lower costs of waste rock handling and coal production, despite the unfavorable values of the coal-quality parameters. The total cost of waste rock management underground and coal processing should be of special interest in the assessment process. These observations led to the general conclusion that interpretation of the geological information at the early stages of the exploration based only on surface boreholes, can lead to overestimating the potential value of the coal reserves and hence to significant errors.It is worth mentioning that the aspects of geological appraisals presented above are commented upon in the professional literature, but elaborations regarding the influence of geological information in the resource economic evaluation are very limited. To strengthen the results achieved, there is a need to continue the research and verify the results obtained on other examples of coal mines.

Influence of moisture and particle size on coal blend bulk density

Abstract Coal blend bulk density is an important property in the coking process. Some variables, such as moisture and particle size, which are controlled or measured in the coal beneficiation process in steel mills, exert a strong influence on this feature. This study aims to understand the density variation of coal blends by the influence of moisture and particle size when using dry and wet bases. The investigations showed that higher density can be reached when drying the coal blend or even with excess of moisture by an agglomeration process. However, for a coal blend of lower moisture content, such as 4%, the better effects on the coking process are evident. Changes on the density from particle size require care, since they can fall in a region of high density achieved by larger particles or in a region with excess coal fines, where either or both can compromise the coke quality.

Moisture transfer of wet coal and its effect on fluidization behavior in a gas–solid separation bed

The characteristics of gas–solid fluidized beds, which are often applied for the separation of minerals, are affected by the moisture carried by wet coal. 3D X-Ray Microanalyser (3D-XRM) and electrical capacitance tomography (ECT) were used to monitor the moisture transfer process of wet coal, as well as the structure and distribution of agglomerates formed in the bed. The fluidization performance of the bed was then studied by a high-speed camera system and pressure drop measurement. The moisture in the wet coal was found to be mainly in the form of free moisture or external moisture on the coal surface. The free moisture mainly formed agglomerates of magnetite, whereas the external moisture caused magnetite to adhere to the surface of raw coal. The agglutinating value of wet coal is mainly affected by external moisture and size fraction, but has little correlation with coal density. The tendency of the formed agglomerate content can be divided into three stages: (i) When the external moisture is 1%, no agglomerates appear in the bed; (ii) When the external moisture reaches 2%, agglomerates are present in the form of magnetite adhering to the coal surface; (iii) When the external moisture exceeds 3%, magnetite adhered to the coal surface is dominant for the agglomerates. Excess moisture will cause the magnetite itself to agglomerate and participate in the internal particle circulation in the bed. At the same time, the moisture content plays a crucial role in the fluidization behavior of the bed. As the moisture content increases, the fluidization behavior of the bed begins to transition from group B to An under low moisture content (<0.25%), and eventually to group C for high moisture (>0.75%).

Development of a Binder Manufacturing Process for Molded Coal Utilizing Used Plastics

Molded coal charging process into coke oven has been used to improve coal charging density. Molded coal charging process can improve coke strength even if the rank of blended coal is low. However, the molded coal is quite expensive because the cost of coal tar binder is high. Thus, we developed a new process that could reduce the amount of tar binder by utilizing used plastics. In this new process, used plastics were charged into heavy tar and dissolved at 200°C. The resulting binder with plastics could improve the strength of the molded coal, thus, coke was prepared experimentally using molded coal with the new binder.

Characterization of coal briquettes using tar as a binding material for use in a coke oven

Abstract In order to increase competitiveness in the steel industry through reduction of the cost of coal mixtures and increase in the quality productivity of coke in the oven, this research was developed with the aim of increasing the bulk density through briquetting of low power coking coal using tar as a binding material. Initially an industrial scale double roller press was used to manufacture briquettes in the ellipsoid format. The physical properties of the briquettes were analyzed in relation to variation of the amount of tar and the curing time of briquettes. Through the process of coal briquetting using low amounts of tar, it is possible to obtain a fuel of greater density, greater use of soft coals, uniform granulometry and easy handling. The increase in the apparent density of coal through briquetting may reach 42.5%. The success achieved in these tests, through these briquettes, with good chemical and physical characteristics represents ease of production as well as economic gain and low investment when compared to other processes of charge densification in coke ovens.

Fractal characterization of pore structure for coal macrolithotypes in the Hancheng area, southeastern Ordos Basin, China

Coalbed methane (CBM) reservoir pore structure is extremely complex and heterogeneous. With the fractal theory, the geometric and structural characteristics of the pore structure could be quantified. However, few studies have aimed to understand the fractal features of compositional-based macrolithotypes (bright, semi-bright, semi-dull, and dull coals). In this work, samples from the Hancheng area, in the southeastern Ordos Basin, China, were collected to investigate the fractal features of pore structures for macrolithotypes and calculate fractal dimensions (Da1 and Da2 for adsorption pores; Ds1 and Ds2 for seepage pores) based on low temperature N2 adsorption and mercury intrusion data, respectively. Meanwhile, the impact of the fractal dimensions on the gas adsorption capacity and the seepage ability were discussed. The results demonstrate that when bright coal turns into dull coal, the vitrinite content, helium permeability, and gas adsorption capacity gradually decrease, while the coal density, mineral content, and ash yield increase. Since the Da1 and Ds1 either deviate from the natural fractal dimension (2 < D < 3) or have a poor correlation with macrolithotypes, Da2 and Ds2 are regarded as the adsorption and seepage pore fractal dimensions, respectively. Of all the coal macrolithotypes, bright coal has the smallest BET specific surface area and micropore proportion, which results in the smallest fractal dimension Da2, while for the dull coal, this is just the contrary; due to the higher mineral content, a higher Da2 of the dull coal indicates a more complicated adsorption pore structure, and the coal with a larger Langmuir volume has a smaller Da2. For the seepage pores, when the bright coal turns into dull coal, the macropore proportion gradually decreases, but the pore proportion tends toward equilibrium, and the mercury withdrawal efficiency increases; the dull coal has a larger Ds2, indicating a more complex seepage pore structure than that in the bright coal. Due to the decreasing macropore proportion and mineral filling, Ds2 demonstrates an obvious negative correlation with the helium permeability and macropore proportion.

EVALUATION OF INITIAL GAS VOLUME OF COALBED METHANE USING FOUR METHOD

&lt;p&gt;Coal bed methane (CBM) is an unconventional energy resources in which the main ingredient is methane gas formed in the process of formation of coal (coalification). Based on research Advance Resource International inc. (ARI), the CBM resource potential is 453 Tcf spread across 11 basins in Indonesia. CBM technology is expected to be one of the alternative energy can play a role in helping to suppress the natural gas needs of oil as one of the energy commodities di Indonesia.&lt;br /&gt;This paper discusses about a calculated initial volume of gas in place (Gas in Place) on CBM reservoir “X” field. This initial gas volume calculation first calculating the gas content is becoming an important parameter in calculating the initial volume. This content gas value can be obtained through data analysis proximate such as ash content, moisture content, volatile matter, fixed carbon which such data can be obtained from laboratory results. But there is also the calculation of the gas content which can be obtained by simply using coal density data using several methods of calculation, such as the Mavor method, Bambang, Modified Kim, and Mullen method. In the “X” field there are five wells coalbed methane drilling has been done, namely, SS-1, SS-2, SS 3, SS-4 and SS-5 and there are five layers are seam-1, seam-2, seam-3, seam-4, and seam-5. Based on the calculations were also obtained in the “X” field coal rank, the average is sub-bitminous. Of the five wells will be calculated gas content and the initial volume of gas using a method Mavor, Bambang, Modified Kim, and Mullen.&lt;br /&gt;Using four methods then the gas content in the SS well ranged between 200-500 SCF / ton. And assuming that the well drainage area (A) covering an area of 100 acres, the obtained large volumes of coal bed methane wells SS-1 with the four methods ranged from 3-9 BSCF, the SS-2 ranged between 1-3 BSCF, wells SS- 3 are 2-5 BSCF, the SS-4 range between 1-3 BSCF and the SS-5 ranges between 1-3 BSCF.&lt;br /&gt;We will be compared the initial gas volume in the Field “X” using the four methods with data from the laboratory result. From that analysis it can be proved that the Bambang method is the most suitable method and represents CBM field in Indonesia. So the initial gas volume in Field “X” is using the result from Bambang method, and the result are 5312.17 MMscf on the SS-1well, 2385.77 MMscf on the SS-2 well, 3330.84 MMscf on the SS-3 well, 1635.44 MMscf on the SS-4 well, and 1608.74 MMscf on the SS-5 well. And the total initial gas volume in the “X” Field is 14273 MMSCF.&lt;/p&gt;

Dry beneficiation of fine coal deploying multistage separation processes in a vibrated gas-fluidized bed

ABSTRACTIn this study, multistage separation processes were introduced into fine coal beneficiation in a vibrated gas-fluidized bed in order to improve the separation performance. The changes of coal properties, operational parameters, and density segregation characteristics during multistage separation were systematically studied. The results showed that with an increase in the separation stage, the range of density was narrowed down and the required input energy decreased. The results showed that with the same yield, the ash content of clean coal decreased from 12.53% for single separation stage to 8.91% for three separation stages, indicating a significant improvement on separation accuracy.

Chemical properties and combustion behavior of constituent relative density fraction of a thermal coal

ABSTRACTThis work presents the experimental results showing the impact of relative density of coal on its properties and combustion behavior. Coal of different mean relative densities (RDm) in the range of 1.375 to 2.0 was prepared through sink–float method of coal beneficiation from the crushed run of mine (ROM) coal. All the RDm fractions were characterized for proximate analysis (PA), ultimate analysis (UA), and gross calorific value (GCV). Combustion behaviors of different coals were carried out by thermogravimetric analysis in the oxygen atmosphere. Important combustion characteristic temperatures like ignition temperature (), peak temperature (), burnout temperature (), and maximum combustion rate () were evaluated from differential thermogravimetric (DTG) data. Further different combustion parameters like ignition index (), burnout index (), combustion performance index (S), combustion rate intensity index (), and activation energy (AE) were evaluated to access the effects of RDm on combustion behavior of coal. Experimental results showed that, with increase in RDm, from 1.375 to 2.0, ash increased from 12.2% to 62.1%, GCV decreased from 8,254 to 3,084 kcal/kg, increased from 357 to 421ºC, increased from 459 to 488ºC, varied from 543 to 553ºC, and decreased from 6.735 to 4.831 wt%/minute. With increase in RDm from 1.375 to 2.0, decreased from 5.8 wt%/minute4, decreased from 9.8 to 4.1 wt%/mintute4, and S decreased from 11.3 × 10−8 to 4.0 × 10−8 wt %2/minute2C3 signifies difficulty in combustion process which was further confirmed by an increase in AE from 92.7 to 173.5 kJ/mole. Overall, experimental and theoretical analysis briefs that coal having lower RDm have better combustion properties compared to higher density coals.

The New Equations for “Rate-Determining Chemisorption of Coal”

The purpose of the new formulas, Cml, CmlK, and CmlY, which express the slowest char combustion rate, is to show the controlling mechanism of single coal burning. Oxygen diffusion through the boundary layer (as a result of releasing volatile matter from coal) to the char surface is the slowest step rate and can also represent as the rate determining. This step has not yet been taken into account in the literature and may effect incomparable decisions between numerical and experimental results of coal combustion studies. In the 1920s, Wilhelm Nusselt found the coal combustion equation for a single coal, which is based on initial coal diameter, and its burning time, or Nusselt square law (NSL). Also, the burning constant in NSL expressed oxygen partial pressure and the ambient temperature level. Nevertheless, recent studies according to char combustion have explained the effect of coal density on char combustion. Consequently, to help understand the slowest rate of char combustion, NSL as well as ordinary char combustion equations can be used together to establish the rate-determining factor. For this purpose, in this study, the slowest step of the char reaction rate is given as “Cml” of stable position for single coal particle, “CmlK” and “CmlY” for a coal particle in a motion.

Changes in Density of Carbon Atomic Packing in Natural Formations

Generalized data of paleotemperature conditions, elemental compositions, technological properties, density, and methane content of coals at different stages of methane generation in terms of catagenetic changes of coalbed organic substance have been studied. Theoretical calculations of changes in averages values of density of carbon atomic packing in natural formations ranging from lignite to anthracite, graphite, and diamond have been represented. Mechanism of the formation of reverse methane content of anthracites at the expense of carbon restructuring of coal, increase in density of carbon atomic packing, and involvement of occluded methane and radicals of СН3 group in the process of anthracite polymerization has been substantiated.

Characterization of the Molecular Structural Changes Following Ion-Exchange Treatment of Zhundong Coal

ABSTRACTLow-rank coal usually contains the highly exchangeable metallic species content. Due to this feature, ion-exchange treatment, which can load extra exchangeable metallic species into coal matrix, is widely used to investigate the behaviors of these species during thermal conversion. However, whether any structural changes of coals are caused during ion-exchange treatment process remains unknown. In this work, to examine structural changes during ion-exchange treatment and provide evidence on reliability of this treatment, multiple techniques were used to characterize the structural features of a Zhundong coal during ion-exchange treatment. The results show that the maximum weight loss of coal becomes smaller after ion-exchange treatment, which indicates that introduction of exchangeable sodium species makes coal matrix density more compact and enhances cross-linking structures. Meanwhile, compared with raw coal, the variation of oxygen forms in the demineralized and ion-exchanged coals is negligible because the maximum differences in content for C–O, C–O, and COO are 5.3, 6.9, and 5.9%, respectively. According to Fourier transform infrared spectra, the skeletal structures of Zhundong coal are also not influenced. Raman spectra show that during ion-exchange treatment, the relative proportions of amorphous carbon structures (particularly small aromatic ring systems with 3–5 fused benzene rings) and large aromatic ring systems (more than six rings) stay almost unchanged. In light of these results, ion-exchange treatment is suggested to result in slight structural changes and is reliable in coal research.

Experimental study on structural models of coal macrolithotypes and its well logging responses in the Hancheng area, Ordos Basin, China

Coal macrolithotype (bright, semi-bright, semi-dull, and dull coals) controls the heterogeneity of coal physical properties in the coalbed methane (CBM) reservoir. However, few scholars carried out the work aiming at the compositional-based macrolithotype analysis of coal reservoirs. In this work, the Hancheng area, Ordos Basin, China, was taken as an example to understand the macrolithotype difference, establish the structural models of macrolithotypes, and then evaluate the responses of advanced well loggings (the natural gamma-ray spectroscopy (NGS), formation microresistivity image (FMI), and cross-dipole array acoustic (XMAC) loggings). Results show that, from the bright to dull coal, the coal density, ash yield, and mineral content increase while the vitrinite content and pore-fracture development degree decrease gradually. The dull and semi-dull coals usually are found in touch with the mudstone (roof, floor, and parting) while the bright or semi-bright coal occurs as an interlayer between them. In the structural models of macrolithotypes for the CBM reservoir, the fracture model couples the artificial and macrofractures controlled by the tectonic stress field as well as the microfracture mainly restricted by the coal macrolithotypes; the pore model shows multilevel pores with gradually decreasing pore size, namely the protogenetic (plant tissue and intergranular pores) and secondary (gas and intermolecular pores) pores; and the pore-fracture relation model is characterized by the multilevel communication between the pores and fractures. Of all the three advanced logging responses of macrolithotypes, the NGS and XMAC show a good consistency with the natural gamma (GR) and interval transit time (AC) loggings since the former was derived from the latter essentially, respectively. But using FMI to identify macrolithotypes is error-prone due to the strong coal heterogeneity around the wellhole. From the bright to dull coal and mudstone, the values of thorium, kalium, uranium elements and GR (or GR without uranium) increase while those of AC including the longitudinal, transverse, and Stoneley waves decrease gradually.

Effects of in-situ stress and joint on permeability of the coal bed in Linfen block, southeastern Ordos Basin, China

Effects of in-situ stress and joint on permeability of the coal bed depend on orientation relationships between in-situ stress and joint. In-situ stress orientations of Linfen block of southeastern Ordos Basin were determined by systematical measurements of the loess joints. In-situ stress magnitudes were calculated based on well logging and hydraulic fracturing data. Joint orientations of the No. 5 coal bed and density distributions of the overlying sandstone bed were investigated. The results show that the NE-oriented maximum horizontal principal stress, approximately parallel to the predominant joint orientation of the coal bed, is favorable to the openness of the predominant joints. The minimum horizontal principal stress, with its orientation perpendicular to the predominant joint orientation, tends to induce the closure of the predominant joints. The stress state of No. 5 coal bed is ov > 0H > Oh, which is favorable for the openness of subvertical joints and an increase in the permeability. The permeability of No. 5 coal bed increases obviously with increasing effective vertical stress and effective horizontal maximum stress and decreases with increasing effective horizontal minimum stress. Besides, the permeability of No. 5 coal bed exhibits a good exponential relationship with the density of predominant joint set. Therefore, predominant joints with the orientation of 45° mainly contribute to increases in the permeability of the No. 5 coal bed in Linfen block. Multidimensional analysis show good exponential relationships among the permeability, predominant joint density, and effective stress of the No. 5 coal bed.

Prediction of tectonic fractures in coal reservoirs using geomechanical method

Coalbed methane (CBM) resources are one of the most important and broadly developed unconventional resources. Considering the particularity of the coal, an adapted geomechanical method involving elastic-plastic deformation is badly needed to calculate the fracture parameters of the coal reservoir. Based on the rock mechanics experiments and three-dimensional μCT scan, the fracture evolution of coals can be summed up to initial compaction, propagation and coalescence stage. The microfractures will rapidly connect to each other when reaching 85% peak strength. Based on the plenty of measurement data, the relationship between fracture volume density and stress-strain of coals is established, and the acquisition of the quantitative geomechanical models made it possible to characterize fracture parameters after various tectonic movements under different stress state. Furtherly, the preparation of procedural language for the finite element (FE) simulation platform made it more popular and effective in the prediction of the generation of fractures and spatial distribution. The simulated results of No. 3 coal seam of Shizhuangbei area, both of the fracture density and direction, were in agreement with field observation results, which can be a compelling evidence for the effectiveness of the method.

CBM Resources/reserves classification and evaluation based on PRMS rules

This paper introduces a set of definitions and classification requirements for coalbed methane (CBM) resources/reserves, based on Petroleum Resources Management System (PRMS). The basic CBM classification criterions of 1P, 2P, 3P and contingent resources are put forward from the following aspects: ownership, project maturity, drilling requirements, testing requirements, economic requirements, infrastructure and market, timing of production and development, and so on. The volumetric method is used to evaluate the OGIP, with focuses on analyses of key parameters and principles of the parameter selection, such as net thickness, ash and water content, coal rank and composition, coal density, cleat volume and saturation and absorbed gas content etc. A dynamic method is used to assess the reserves and recovery efficiency. Since the differences in rock and fluid properties, displacement mechanism, completion and operating practices and wellbore type resulted in different production curve characteristics, the factors affecting production behavior, the dewatering period, pressure build-up and interference effects were analyzed. The conclusion and results that the paper achieved can be used as important references for reasonable assessment of CBM resources/reserves.

Prediction and Characterization of the Microcrystal Structures of Coal with Molecular Simulation

The characterization of coal structures is challenging due to their broad distribution of molecular structures including large-scale entities. Previously, the micro-crystal structure of coal has been extensively observed with the XRD analysis and its features were found to be closely correlated with the carbon/oxygen content. In this work, Polymorph Predictor, a Monte Carlo method, was applied to predict the most favorable micro-crystal structures formed by simplistic coal models and to study the effect of carbon content on the density and inter-layer spacing (d002) of coal. The valence or non-bond interactions existed in predicted crystal structures were analyzed by calculating the energy contributions based on the classical molecular dynamics (MD) simulation theory. The calculation from Density functional theory (DFT) of coal fragments was conducted to study the relationship between carbon content and electronic properties of coal. Additionally, the MD simulation of water contact angle was conducted to ...

Ultrasonic technique for online measurement of bulk density of stamp charge coal cakes in coke plants

Coke oven batteries utilize stamp charged coal cakes for production of high quality blast furnace coke. Crushed coal blends are mechanically stamped to produce coal cakes. It is crucial to have a good control over this stamping operation so as to achieve a uniform bulk density (≈1100–1200kg·m−3 wet basis) of coal cake post stamping. This can facilitate robust and energy efficient coking operation. The dynamic nature of the stamping operation necessitates an online bulk density measurement technique. An ultrasonic technique which enables online measurement of bulk density during the stamping operation is described. The ultrasonic response was found to have a straight line correlation with bulk density (wet basis) and moisture content of stamped coal with an R2 value of 0.98. The effect of moisture content in the coal on the ultrasonic measurements is also discussed. A lab scale prototype was developed with integrated sensors to emulate online measurement. The prototype was found to have a measurement error of less than ±1.6%. This method can also be suitably adapted for online bulk density measurement of granular solids other than crushed coal.

A INFLUÊNCIA DA VIBRAÇÃO MECÂNICA DA CARGA DE CARVÃO NOS ÍNDICES CSR E CRI DO COQUE METALÚRGICO

Steelmaking companies must be always being looking for innovation and how to develop their production methods, because this is unquestionable very important to keep the company competitiveness on world’s market. This research is about an improvement of metallurgical coke production on coke ovens by coal charge mechanical vibration, on this way will be possible a bigger oven loading and an utilization of more poor coal blends, and, consequently, cheaper. The scientific research has happened on experimental scale on a 4,5 kg capacity coke oven, The mechanical vibration was produced by a mechanical immersion vibrator, the one commonly used for concrete compacting on civil construction. The coke produced increased by 21% of the CSR value and a 26% reduction of the CRI. The results obtained contradicts some results of the literature that report that the CSR and CRI are not influenced by loaded coal density, although these studies the densification technique used was stamp charging.