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Biogenic coalbed methane (CBM) is a developing clean energy source. However, it is unclear how the mechanisms of bio-methane production with different sizes of coal. In this work, pulverized coal (PC) and lump coal (LC) were used for methane production by mixed fungi-methanogen microflora. The lower methane production from LC was observed. The aromatic carbon of coal was degraded slightly by 2.17% in LC, while 11.28% in PC. It is attributed to the proportion of lignin-degrading fungi, especially Penicillium, which was reached 67.57% in PC on the 7th day, higher than that of 11.38% in LC. The results suggested that the limited interaction area in LC led to microorganisms hardly utilize aromatics. It also led the accumulation of aromatic organics in the fermentation broth in PC. Increasing the reaction area of coal and facilitating the conversion of aromatic carbon are suggested means to increase methane production in situ., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Combustion or gasification of coal in nitrogen-free environment (CO 2 -H 2 O-O 2 ) is a promising technology contributing to reduce the carbon footprint in the energy industry. Accordingly, this will make it quite easy to capture practically pure carbon dioxide for subsequent storage. The study presents numerical investigation of the entrained-flow oxy-gasification processes of pulverized coal in CO 2 -H 2 O-O 2 environment. A numerical methodology for describing oxy-fuel gasification processes has been developed and tested. A study of the influence of the absorption of gas coefficient on the calculation results was carried out. Studies have been conducted on the effect of the excess oxygen ratio, the oxygen concentration in the blast, and the amount of moisture on the physicochemical processes and the composition of the syngas for the gasifier under consideration. It is shown that increasing the oxygen concentration in the blast allows stabilizing the ignition and combustion of pulverized coal at low excess oxygen ratio. The dependence of the chemical efficiency on the main regime parameters is determined. The results showed that a decrease in the excess oxygen ratio from 0.43 to 0.33 leads to an increase in combustible losses from 0.15 to 45% for this gasifier. In the mode with high fuel conversion in the gasifier, the produced syngas with a caloric value of 9.26 MJ/m 3 comprised of CO, 40.3; H 2 , 32.4; and CO 2 , 25.5 (vol. % dry)., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Characteristics of pulverized coals have significant influence on the spontaneous combustion and explosion processes. This paper presents an experimental and theoretical framework on physico-chemical characteristics of coal and their interrelations from spontaneous combustion and explosion perspectives. The chemical properties, morphology, bulk density, particle size, and specific surface area of pulverized coals from nine different coal subsidiaries of India are vividly investigated in five distinct sizes. Moreover, the effects of particle size on bulk density, specific surface area, and N 2 adsorption capacity of pulverized coals are critically analyzed. With decrease in particle size, the bulk density of pulverized coals decreased, and the specific surface area and N 2 adsorption capacity increased. The relationships of bulk density and specific surface area of pulverized coals with particle size are established. Moreover, the specific surface areas determined by both the particle sizing and BET methods are compared, and correlation factors between them are determined. This study generated insightful coal characteristic data, which can be useful for furthering research on spontaneous combustion and explosion involving pulverized coals., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The combustion behaviors of sewage sludge (SS), pulverized coal (PC), and their blends were studied using a thermogravimetric analyzer. The effect of the mass ratio of SS to PC on the co-combustion characteristics was analyzed. The experiments showed that the ignition performance of the blends improved significantly as the mass percentage of SS increased, but its combustion intensity decreased. The burnout temperature (T b ) and comprehensive combustibility index (S) of the blends were almost unchanged when the mass percentage of SS was less than 10%. However, a high mass percentage of SS (>10%) resulted in a great increase in T b and a notable decrease in S. Subsequently, the effects of different catalysts (CaO, CeO 2 , MnO 2 , and Fe 2 O 3 ) on the combustion characteristics and activation energy of the SS/PC blend were investigated. The four catalysts promoted the release and combustion of volatile matters in the blended fuels and shifted their combustion profiles to a low temperature. In addition, their peak separating tendencies were obvious at 350-550 C, resulting in high peak widths. All the catalysts improved combustion activity of the blended fuel and accelerated fixed carbon combustion, which decreased the ignition temperature and burnout temperature of the fuels. CeO 2 had the best catalytic effects in terms of the comprehensive combustion performance and activation energy, followed closely by Fe 2 O 3 . However, the rare-earth compounds are expensive to be applied in the catalytic combustion process of SS/PC blend at present. Based on both catalytic effects and economy, Fe 2 O 3 was potentially an optimal option for catalytic combustion among the tested catalysts., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the identification accuracy of coal gangue under the complex working conditions of pulverized coal and moisture adhesion on the surface, this paper studies the distribution difference of characteristic curves under five working conditions of different proportions of moisture and pulverized coal, and finds that moisture has a greater influence on gradient features, while pulverized coal has a greater influence on gray texture features. Then this paper studies the distribution of coarse texture and fine texture in coal and gangue, and finds that there are many fine textures and few coarse textures on the surface of gangue, while coal shows the opposite law. In addition, the ratio of pixels with large gray value to pixels with small gray value can reduce the occurrence of noncompliance with the above laws. Finally, through the combination of coarse texture, fine texture, and gray value difference, the relief feature is put forward. Compared with different features, the average feature overlap ratio proposed in this paper is lower, at 23.83%. Compared with different methods, this method has a higher identification rate under different working conditions, and the average identification accuracy rate is 89.59%, which is at least 13.93% higher than other methods. [ABSTRACT FROM AUTHOR]

The combustion and fragmentation characteristics of wet coal slime particle are different from that of dried coal particle. In this paper, an understanding of the combustion process of wet coal slime particle through the combined results of the morphology characteristics, mass changes, and gas release pattern is provided. A tube furnace and high-speed camera were used to observe morphological changes of the combustion process of wet coal slime. For comparison, the mass change and gas release pattern of wet coal slime was monitored by a thermogravimetric analyzer and mass spectrometer (TG/MS). The four combustion stages of coal slime were observed for the first time: (1) drying and evaporation, (2) devolatilization and fragmentation, (3) volatile homogeneous combustion, and (4) char heterogeneous combustion. The water content in wet coal slime greatly affected the fragmentation of coal slime, it could build up a great internal pressure when evaporated, which caused the primary fragmentation to occur earlier and be more severe than traditional coals. The temperature and diameter of the slime were considered as factors for the occurrence of fragmentation and the level of it. A larger diameter with a higher furnace temperature resulted in a more severe fragmentation of the wet coal slime. The smaller coal slime at the lower temperatures did not experience the fragmentation stage. Here, the fragmentation and non-fragmentation zones of wet coal slime at different temperatures and different paticle diameters are given, which could be a guide for the combustion of coal slime in CFB(Circulating Fluidized Bed). Also, for larger diameters and lower setting temperatures, the ignition delay time and burnout time of wet coal slime became longer. The gas release pattern of wet coal slime during the combustion process was analyzed, and it was determined that it could be affected greatly by fragmentation. A model of the drying and evaporation stage of wet coal slime was established for the first time by using COMSOL Multiphysics. The results of the theoretical calculations show that there were two evaporation rate peaks of water when fragmentation occurred, which theoretically explained the early stage of the combustion process of wet coal slime, and the results were in agreement with the experiments. [ABSTRACT FROM AUTHOR]

Background: The combustion of coal, the world's most polluting form of energy, must be significantly curtailed to limit the global average temperature increase to well below 2°C. Since carbon pricing is politically constrained, alternative policies, such as compensating coal plant owners, for early closure are being considered. Methods: Germany is the only country to date to have implemented a reverse auction to give compensation payments for early coal retirement. We analyse the merits and demerits of Germany's policy, drawing comparisons with other countries that have phased out coal through other means. Results: While bilateral negotiations can lead to excessive compensation due to asymmetric information, a competitive auction can discover the true cost of closure and help allocate funds more efficiently and transparently. Germany's experience illustrates the practical necessity of adjusting auction design to ensure additionality, reduce the risk of gaming and manage the security of supply. Conclusion: While auctions have attractive properties in theory, in practice, their design must address these concerns to unlock the full benefits. Retirement auctions that deliver compensation payments can be a pragmatic policy option, particularly in countries where an incumbent coal lobby makes punitive measures such as carbon taxation hard to implement. However, where there is a concentration in coal plant ownership, auctions will not work and alternative policies, such as enhanced incentives for scrappage and repurposing of coal assets, could be used instead. In many coal-burning areas, the decline of coal is slowed down by long-term contracts that insulate coal-fired generation from competition. Compensation for early closure is a 'pay-to-break' mechanism which may be a politically feasible alternative to 'polluter-pays' policies such as carbon pricing. Competitive auctions can deliver efficient and transparent compensation payments for early coal closures relative to negotiations which suffer from asymmetric information. Ensuring that there is sufficient competition in a coal closure auction through design adjustments can ensure discovery of true closure costs. Shutting down coal-fired power plants can lead to fiscal savings in countries where coal-fired generation is supported by capacity payments. [ABSTRACT FROM AUTHOR]

Copyright of Geology & Exploration is the property of Geology & Exploration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The treatment of sewage sludge has become a global concern. Large amounts of sewage sludge can be disposed of by burning coal-mixed sludge. Thermogravimetric analysis and lab-scale combustion experiments in a drop tube furnace were utilized to study the combustion characteristics, pollutant emissions, and heavy metal migration during the co-combustion of coal and sewage sludge. The results showed that the blended fuels with a sewage sludge content less than 10 weight percent exhibited coal-like combustion characteristics. Additionally, the additional sewage sludge favored the ignition performance of blended fuels. When sewage sludge was added, the SO2 emissions rose to 76 mg/Nm3 under the 10% sludge condition—nearly three times higher than that of coal alone. While NOx emissions stayed mostly unchanged, HCl and HF emissions were very low. Meanwhile, Cr, Cu, and Ni migrated to the bottom ash, and their concentrations were all reduced with an increase in sewage sludge. Pb, Cd, Cr, Cu, Ni, and Hg migrated to the flue gas, mostly in the form of gaseous components. The results provide crucial information in the co-combustion of sewage sludge and coal, with implications in the development and improvement of large-scale, harmless, and resource-recovering techniques for waste sludge. [ABSTRACT FROM AUTHOR]

The present research shows the combustion characteristics of different specific gravity fractions of high ash thermal coal. Coal with different mean specific gravity (SGM) ranging from 1.25 to 2.0 was produced using the float–sink experiment. All SGM coals were characterized with proximate analysis, ultimate analysis, higher heating value, ash analysis, Brunauer–Emmett–Teller analysis and Fourier-transform infrared spectroscopy (FTIR). Combustion experiments were performed with thermogravimetric analysis to identify the impact of SGM. Experimental results inferred that ignition temperature ranged from 285 to 408 °C as SGM varied from 1.25 to 2.0. The combustion rate of 1.25 SGM coal was found to be the highest due to the strong or moderate presence of hydrocarbons like alkane, alkene, aldehyde and alcoholic, as observed from FTIR. Activation energy ranged from 121.81 to 54.60 kJ/ mol as SGM of coal increased from 1.25 to 2.0. Thermodynamic analysis inferred that 1.65 SGM coal had the highest ΔS (− 158.21 J/mol. K) and minimum ΔH (48.93 kJ/ mol), inferring ease of decomposition and higher combustion reactivity. [ABSTRACT FROM AUTHOR]

Coal slurry is a semi-solid material formed by the water content of pulverized coal, which is a product of the coal production and transportation process and has viscous and wet characteristics, and is easy to cause blockage in the process of mechanized mining and transportation. To study the resistance law of the probe rod pressed into the quasi-static viscous particle medium at a uniform speed, coal dust and deionized water were mixed into different water content of coal slurry, and the resistance of the probe rod under pressure in different water content of coal slurry was measured. It is found that when the cohesion of coal slurry is small, the press-in process tends to be stable, and the intrusion resistance shows a linear-slowly increasing-suddenly increasing trend as the depth of pressure increases. [ABSTRACT FROM AUTHOR]

The conditions in the combustion zones, i.e., the raceways, are crucial for the operation of the blast furnace. In recent years, advancements in tuyere cameras and image processing and interpretation techniques have provided a better means by which to obtain information from this region of the furnace. In this study, a comprehensive approach is proposed to visually monitor the status of the pulverized coal cloud at the tuyeres based on a carefully designed processing strategy. Firstly, tuyere images are preprocessed to remove noise and enhance image quality, applying the adaptive Otsu algorithm to detect the edges of the coal cloud, enabling precise delineation of the pulverized coal region. Next, a Swin–Unet model, which combines the strengths of Swin Transformer and U-Net architecture, is employed for accurate segmentation of the coal cloud area. The extracted pulverized coal cloud features are analyzed using RGB super-pixel weighting, which takes into account the variations in color within the cloud region. It is demonstrated that the pulverized coal injection rate shows a correlation with the state of the cloud detected based on the images. The effectiveness of this visual monitoring method is validated using real-world data obtained from a blast furnace of SSAB Europe. The experimental results align with earlier research findings and practical operational experience. [ABSTRACT FROM AUTHOR]

The oxidation characteristics and spontaneous combustion (SC) tendency of raw long-flame coal (RC), water-soaked 200-day coal (S200), pre-oxidized water-soaked coal at 200 °C (O200S200), and pre-oxidized soaked coal at 300 °C (O300S200) in an oxygen-poor environment were investigated using a programmed warming system. The results show that pre-oxidation water-soaked treatment (PWT) promotes the coal-oxygen complex reaction and increases the rate of coal oxygen consumption (OCR) and the rate of carbon and oxygen compound production. The rate of CO and CO2 production of the water-soaked (WS) coal increased by 0.329 mol·(cm3·s)−1 and 0.922 mol·(cm3·s)−1, respectively, compared with that of the original coal sample. PWT reduces the activation energy of coal in the low-temperature oxidation stage (the maximum difference can be up to 110.99 kJ/mol) and enhances the oxidizing and heat-releasing capacity. There was a synergistic effect between the pre-oxidation (PO) and WS treatment, and the lowest comprehensive determination index of the SC propensity of coal in O200S200 samples was 831.92 which was 4.72 lower than that of RC samples, presenting a more SC tendency. Low oxygen concentration has an inhibitory effect on the oxidation characteristic parameters of coal, and the apparent activation energy of the low-temperature oxidation stage of pre-oxidized water-soaked coal (PWC) increased to 206.418 kJ/mol at 3% oxygen concentration. The lower the oxygen concentration of the anoxic environment, the lower the risk of SC of the coal samples. The results of the study can provide theoretical guidance for the identification and prevention of SC disasters in coal seams with shallow burial and close spacing. [ABSTRACT FROM AUTHOR]

In this study, the co-combustion of coal and biomass, and the tri-combustion of coal, biomass, and oil sludge in a 130 t h−1 circulating fluidized bed (CFB) boiler are investigated via the computational particle fluid dynamics (CPFD) approach. Furthermore, the effect of biomass feeding position is also comprehensively evaluated. The results show that for the co-combustion of coal and biomass, the O2 mole fraction at the furnace outlet rises from 0.0541 to 0.0640 as the biomass blending ratio enhances from 40% to 100%, while the CO2 mole fraction reduces from 0.1357 to 0.1267. The mole fraction of NOx and SO2 at the furnace outlet decreases from 4.5867 × 10−5 to 3.9096 × 10−5 and 2.8253 × 10−4 to 4.6635 × 10−5, respectively. For the tri-combustion of three fuels, the average NOx mole fraction initially grows quickly and then declines gradually, ranging from 4.1173 × 10−5 to 4.2556 × 10−5. The mole fraction of SO2 at the furnace outlet increases from 3.5176 × 10−4 to 4.7043 × 10−4 when the ratio of oil sludge rises from 10% to 20%. The uniformity of temperature and gas components distribution is "new inlet > secondary air inlet > feed inlet". As for the three inlet positions, the mole fractions of NOx at the furnace outlet are between 3.9096 × 10−5 and 5.1537 × 10−5, while those for SO2 are between 2.5978 × 10−4 and 2.5278 × 10−4. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of gas pressure, in-situ stress, and coal strength on coal and gas outbursts (CGO) based on the laboratory CGO experimental data. Based on the hypothesis of the comprehensive of CGO, the single-factor control variable method was used to analyze and evaluate the relative outburst intensity, the characteristics of outburst holes, the distribution of pulverized coal, the drops of outburst gas pressure, and the pulverized coal density under different outbursts experimental condition. The improved CGO energy equation and instability criterion are proposed as a direction to study the occurrence of CGO as an energy evolution direction. Furthermore, the results shows that the initial outburst gas pressure was 0.45 MPa during the experimental conditions of in-situ stress was 5 MPa, and the coal strength was 0.24 MPa. The gas pressure is directly proportional to the relative outburst intensity, while the in-situ stress and coal strength are inversely proportional to the relative outburst intensity. After the CGO occurred, the outburst coal always show spallation and pulverization characteristics. The results highlight that the gas pressure plays a key role in pulverizing and throwing out the pulverized coal, and the in-situ stress mainly plays a role in destroying the coal, and the coal strength plays a resistance role during the CGO occurs. It is also found that pulverized coal particles size less than 0.28 mm can be used to represent the distribution pattern of the total weight of outburst pulverized coal particles in the different outburst interval. These results clearly illustrate that using effective methods to control gas pressure, in-situ stress, and coal strength has an important role in preventing and controlling CGO on coal mining sites. [ABSTRACT FROM AUTHOR]

The present study performs three-dimensional (3D) numerical simulations of coal combustion of four samples with varying ash content in a drop tube furnace (DTF) to mimic the particle heating rates observed in industrial furnaces. The numerical framework adopted is validated with prior experimental and simulation results using a 3D cylindrical geometry and a very good match is obtained for the axial temperature distribution and particle burnout rate. The combustion performance of coal samples with varying ash contents of 2.3, 16.6, 24.1, and 37.2 wt%, is explored through temperature profiles, burnout rates, particle tracking, and mass fractions of various products of combustion. A user-defined function is used to specify the 14 species, 10-step solid particle combustion with a modified eddy dissipation concept model for volatile combustion. The range of ash content considered is for Indian coal which has a high degree of heterogeneity, making the evaluation of its combustion performance, a challenge. The present work aims to provide benchmark set of results showing the evolution of the evaporated, charred, and volatile mass for the three ash contents, which has not been attempted before. It is found that the high-ash content Indian coal samples have a tendency to produce less NOx . A 9:52% reduction in the NOx is obtained for the coal sample with 37:2% ash compared to that with 16:6% ash. The results suggest that the combustion performance is enhanced when the ash content falls within an optimum range of 20 35%. [ABSTRACT FROM AUTHOR]

Low rank coals are not used optimally, another way to increase this value is combustion without oxygen, known as pyrolysis. On the other hand, as a solid waste biomass, palm kernel shell (PKS) is a by-product of the palm oil industry that can cause environmental problems if not handled properly. In fact, the waste is plentiful and not even widely used, therefore it may also be an ideal feedstock for the pyrolysis process. This study compares the distribution of products from coal and PKS pyrolysis, and also characterizes the liquid (tar) and solid (char) products. The results show that the pyrolysis of coal produces more char, while the pyrolysis of PKS produces more gas. Higher tar yields were obtained with the pyrolysis process using PKS. GC-MS identified the main tar compounds for both materials as phenol and acetic acid, 3-methylphenol and methanol were also found in coal and PKS, respectively. The calorific value of char increased by about 5.19 % for coal and 41.12 % for PKS after pyrolysis. The other physical properties of coal and PKS are also improved after pyrolysis. Therefore, the application of pyrolysis in the use of coal and PKS can increase the added value of these two materials and contribute to alternative energy sources. [ABSTRACT FROM AUTHOR]

The gas contained in coal plays a crucial role in triggering coal and gas outbursts. During an outburst, a large quantity of gas originally absorbed by coal is released from pulverized coal. The role this part of the gas plays in the process of coal and gas outbursts has not been clearly elucidated yet. Therefore, investigating the changes in gas desorption rate from coal particles of different sizes could provide some meaningful insights into the outburst process and improve our understanding of the outburst mechanism. First, combining the diffusivity of coal of different particle sizes and the distribution function of broken coal, we present a gas desorption model for fragmented gas-bearing coal that can quantify gas desorption from coal particles within a certain range of size. Second, the gas desorption rate ratio is defined as the ratio of the gas desorption rate from coal being crushed to that from coal before breaking. The desorption rate ratio is mainly determined by the desorption index (γ) and the granularity distribution index (α). Within the limit range of coal particle sizes, the ratio of effective diffusion coefficient for coal particles with different sizes is directly proportional to the reciprocal of the ratio of particle sizes. Under uniform particle size conditions before and after fragmentation, the gas desorption rate ratio is the square root of the reciprocal of the effective diffusion coefficient. The gas desorption model quantitatively elucidates the accelerated desorption of adsorbed gas in coal during the continuous fragmentation process of coal during an outburst. [ABSTRACT FROM AUTHOR]

The influence of the oxygen content in the gas phase on the thermal destruction and combustion of peat and coals with various degrees of metamorphism were studied using a device for synchronous thermal analysis to optimize the conditions for obtaining pulverized coal fuel. It was found that the thermal destruction rate decreases at higher degrees of metamorphism (e.g., 2.69%/min for peat; 1.48%/min for brown coal; 0.55%/min for lean coal, and 0.30%/min for anthracite). The volatile component release temperature decreases (from 420°C for lean coal to 220°C for peat) and remains approximately the same in the presence of oxygen up to the composition of synthetic air. The structure of peat particles was studied on a scanning electron microscope. They have an elongated shape measuring from 50 to 400 μm in size. The predominant grain structure is cellular, or less often – fibrous and layered. The onset combustion temperature of peat-contained carbon is about 340°C. The processes are accompanied by the release of a significant amount of gases, such as CO2, H2O, H2, SO2, NO, and NO2. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a key nutrient for many organisms but its global atmospheric budget is largely unconstrained. Estimates of major emissions sources such as fossil‐fuel combustion range from ∼0.02 to 1.1 Tg yr−1, and primary biogenic emissions range from 0.16 to 1.0 Tg yr−1. Here we used detailed measurements of phosphorus in Alpine ice cores extracted from the Col du Dôme (CDD) glacier located near the Mont Blanc summit and atmospheric model simulations to evaluate changes in western European emissions from pre‐industrial (PI) to modern times. The ice‐core records show that P concentrations during the PI were about 0.9 ng g−1, of which one third was of crustal origin and two thirds the result of primary biogenic emissions. Concentrations were higher throughout the 20th century, reaching 2.5 ng g−1 in the 1980s. Analysis of source tracers measured in the same ice, commodity productions statistics, and other information suggest that the increase in P throughout the 20th century was caused by enhanced emissions from natural and anthropogenic sources. Coal burning and steel industry represented the main anthropogenic sources during the first and second half of the century, respectively. After 1950, the increase in P was also caused by enhanced dust emissions, with increased biogenic emissions caused by recent changes of use‐land also contributing. These findings provide important constraints on the atmospheric P budget at the scale of western Europe during the recent centuries. Plain Language Summary: Phosphorus is an important nutrient for terrestrial and aquatic flora and fauna. Whereas dust aerosol emissions are the dominant atmospheric source of phosphorus on a global scale, other sources such as biogenic particles emitted by vegetation, as well as fossil‐fuel combustion, may represent important sources in less‐dusty industrialized regions. Estimates of these non‐crustal sources are uncertain, however, with values often varying by an order of magnitude or more. Comparison with long‐term pollution records extracted from well‐dated ice cores provides a means of evaluating these estimates. Here, we analyzed phosphorus in ice cores extracted near the Mont Blanc summit in the French Alps to develop an 1850 to 2000 record. Phosphorus deposition doubled during this period, with increases attributed to enhancement of both natural (dust and biogenic particles emitted by vegetation) and anthropogenic (mainly coal burning and the steel industry) emissions. Key Points: A doubling of phosphorus in Alpine ice deposited between 1850 and 2000 from increasing natural and anthropogenic emissionsPhosphorus deposition trends from 1900 to 1975 mainly attributed to coal burning and pig iron industry emissionsNatural European phosphorus sources dominated by primary emissions of biogenic (70%) and dust (30%) particles that were enhanced after 1975 [ABSTRACT FROM AUTHOR]

The work determines the characteristics of the processes of thermal decomposition and combustion when heating coal, cedar needles, and their mixtures with different fuel particle sizes. Based on the results of thermal analysis, the following characteristics were determined: the temperature at which the coke residue ignition occurs, the temperature at which the combustion process is completed, and the combustion index. An analysis was carried out of the interaction between the fuel mixture components on the characteristics of their combustion for compositions (50% coal and 50% biomass) with a particle size of 100–200 μm and 300–400 μm. The combustion kinetic parameters of individual solid fuels and their mixtures containing 50% coal and 50% biomass are compared. The activation energy for coal combustion was 60.3 kJ mol−1, for biomass 24.6 kJ mol−1, and for mixture 42.5 kJ mol−1. The co-combustion of coal and biomass has a positive effect on the main combustion characteristics of solid fuels. Fuels with particle sizes of 100–200, 200–300, and 300–400 μm were studied at temperatures of 500–800 °C under heating conditions in a heated airflow. Using a hardware-software complex for high-speed video recording of fast processes, the ignition delay times were determined, the values of which for the considered fuels vary in the range from 0.01 to 0.20 s. Adding 50 wt% biomass with particle sizes of 100–200, 200–300, and 300–400 μm to coal reduces the ignition delay times of mixtures by 55, 41, and 27%, respectively. The results obtained can become the basis for the conversion and design of modern power plants operating on solid fuel mixtures to co-combust coal with biomass. [ABSTRACT FROM AUTHOR]

Co-combustion of semi-coke and coal is a prospective technique for large-scale disposal or utilization of the solid waste. In this paper, the co-combustion behaviors and kinetics of semi-coke and coal were studied by thermogravimetric analysis with a focus on the influence of blending method and synergy. The results indicated that the semi-coke combustion was improved by blending with coal, and the interaction between fuels tended to promote the co-combustion. The ignition and burnout temperatures were positively correlated with the carbon content of the mixture, while the comprehensive combustion index and stability index were negatively correlated with it. The layer blending and partition blending method seemed to show stronger promotion than uniform blending method, and the layer blending method with coal in the upper layer was recommended due to the better combustion behavior. The promotion of coal on semi-coke combustion was less affected in devolatilization stage but weakened by the decrease of O 2 concentration in char burnout stage. The apparent activation energy (E a) of the mixture decreased with the increasing faction of coal. The layer blending method with coal in the upper layer had the lowest E a in devolatilization stage and relatively high E a in char burnout stage. The work can give some new insights into waste co-disposal strategy and carbon emission reduction in China. [Display omitted] [ABSTRACT FROM AUTHOR]

Aiming at the problem of pulverized migration and plugging propped fractures during coal seam fracturing, we experimentally studied the pressure changes and pulverized coal blocking characteristics with deionized water and solutions of three surfactants including 1227 (C21H38ClN), SDS (C12H25SO4Na) and TX-100 (C34H62O11). A device capable of visualizing propped fractures was established, and simulation experiments were conducted with solutions of different surfactants at different injection flow rates. The obtained images were binarized and analyzed to quantify the pulverized coal blockage degrees of facture under different conditions. The experimental results show that: (1) The higher the injection flow rate, the higher the inlet pressure. (2) All three surfactants can lower the injection pressure, as compared with water alone. SDS decreases the injection pressure more obviously at low injection flow rates, and the other two perform better at high injection flow rates. (3) Similar to their effects on inlet pressure, the ratio of pulverized coal in SDS solution is lower at low injection flow rates, while TX-100 and 1227 solutions show lower ratios of pulverized coal at high injection flow rates. Our work has provided a theoretical support for coal blockage removal and pressure reduction in propped fractures during coal seam fracturing to improve coal seam permeability and further improves the dust prevention effect of coal seam water injection. [ABSTRACT FROM AUTHOR]

Oxy–fuel (O2/CO2) combustion technology shows great potential for carbon reduction. However, difference in the combustion atmosphere would affect coal combustion characteristics and pollutant emissions. In order to explore oxy–fuel combustion characteristics, two typical Chinese coals, sub–bituminous and lean coal, were utilized. Based on thermogravimetry and pilot–scale test, the ignition and burnout characteristics under oxy–fuel and air combustion atmosphere were investigated. Besides, the NOx emission characteristics were also investigated on the pilot–scale test. Through experimental results, these two kinds of coal showed different combustion characteristics, mainly due to differences in coal quality. Compared with air combustion, oxy–fuel combustion affected the coal combustion process. Firstly, the ignition temperature of sub–bituminous and lean coal decreased from 418 and 477 °C to 405 and 415 °C, respectively; the burnout temperature also decreased from 855 and 985 °C to 808 and 838 °C, respectively. Then, coal combustion performance was evaluated by comprehensive combustion characteristics (S); with an increase in S from, respectively, 3.659 and 2.013 to 4.826 and 3.545 × 10−8(min−2 × K−3), the combustion performance significantly improved. Then, the char burnout time was advanced for 1~3 min. Similar results were obtained on the pilot–scale test. The ignition temperatures decreased from 505 and 552 to 490 and 512 °C, respectively. Moreover, the char burnout rate increased by 0.5~5% and 2~11%, respectively. Lastly, the NOx concentration in flue gas was 2.2~2.6 and 2.0~2.3 times higher for the two kinds of coal under oxy–fuel combustion. [ABSTRACT FROM AUTHOR]

Mathematical validation and comparison of coal milling operations of a horizontal ball tube mill and a vertical bowl mill located in two distinct coal based power plants in India was carried out. The coal mill model was developed and the unknown model coefficients were obtained numerically by genetic algorithm (GA). The input variables of mass flow rates of raw coal and air and temperature of inlet primary air were obtained from the on-site data. The output variables of mill current and mill outlet temperature as obtained by GA were compared with on-site data for the two mills and show good agreement. The ball tube mill requires less mass flow rate of primary air and raw coal per MW of power produced than the bowl mill. It contains larger mass of raw and pulverized coal but less grinding heat is generated in this mill. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coal ash fusion characteristics are a significant factor to consider while designing a boiler to match a coal or different coal range. Characterization of coal ash provides the fundamental mechanism that controls the heating efficiency of the coal in a pulverized coal-fired boiler, regarding the coal minerals association. Changes in coal properties could lead to changes in ash properties, i.e., ash fusion temperatures (AFT) and ash elemental composition, which could lead to slagging or fouling issues inside the boiler. The main cause could be attributed to the high temperature of the combustion process and the low melting point of ash, or vice versa. This study aimed to develop AFT prediction models using coal samples from different coalfields to predict the initial deformation temperature (DT), softening temperature (ST), hemispherical temperature (HT) and fluid temperature (FT) of coal ash. The artificial neural network (ANN), Gaussian process regression (GPR) and support vector regression (SVR) are the three machine learning tools used in this modeling. The resulting AFT predictive models indicated that the ANN model predicted DT, ST, HT and FT more adequately and reliably than the GPR and SVR. The Taylor's diagram, which enabled easy identification of the closeness of the model predictions to the measured data, also indicated that the ANN outperformed all the other models. [ABSTRACT FROM AUTHOR]

In this study, the combustion characteristics of pine needles, pine needle humus, and the co-combustion of these two types of biomass with coal were compared. In addition, the optimization of the combustion performance of coal/humus was assisted through the following studies: (i) the combustion performance of coal/pine needle humus was studied under four different oxygen concentrations (N2, 10%O2/90%N2, 20%O2/80%N2, and 40%O2/60%N2); (ii) the synergistic effect between the humus and coal during combustion was also investigated by adjusting the blending ratio and oxygen content; (iii) the mechanisms of the optimized combustion processes were expounded by kinetics and thermodynamics discussion. The results demonstrated that the combustion characteristics of the coal/humus blends were found to be higher than those of the coal/pine needle blends. The coupling interactions of the oxygen content and blending ratio contributed to the significant synergistic effect between the two fuels, and the synergistic effect showed a nonlinear variation with an increased oxygen concentration. The synergistic effect in a rich oxygen environment (O240%/N260%) is 5.1 times greater than that in the synthetic air (O220%/N280%) and 13.8 times greater than that in the oxygen-poor environment (O210%/N290%). Hence, the blending ratio could be adjusted to maintain the intensity of the synergistic effect in an oxygen-rich atmosphere. [ABSTRACT FROM AUTHOR]

The coal found in the Longtan Formation of the Late Permian is widely distributed in Southwest China, including the northwestern Guizhou, southeastern Sichuan, and northern Yunnan regions. This coal typically has a high sulfur content. Eighty-two coal samples were collected from the coal strata in 11 counties spanning this area, including underground mine coal, native outcrop coal and man-made outcrop coal. The mercury, total fluorine, total sulfur, and sulfate contents and pH values were determined. The results showed that the average mercury content in native outcrop coal was 2233 ng/g, whereas that in underground mine coal was 306 ng/g, and the relative enrichment factor could reach 6.6. There was no significant difference in the total fluorine content among the three types of coals; furthermore, the total sulfur content in native outcrop coal and man-made outcrop coal was higher than that in underground mine coal because of the local policy, which strictly prohibits the mining of high-sulfur coal. Native outcrop coal is acidic, with a total average pH of 3.54 and an average sulfate content as high as 13,390 μg/g. In contrast, underground coal is almost neutral (average pH 7.33), with a low sulfate content (average 3221 μg/g). These characterizations indicate that native outcrop coal has been subjected to long-term weathering and the mercury enrichment is likely due to migration, oxidation, and precipitation of Hg from the underground coal seam and enriched in loose and pulverized coal particles. Further investigation is needed to determine whether other outcrop areas are affected by this phenomenon. [ABSTRACT FROM AUTHOR]

Blended coal combustion technology is being adopted by more and more power plants as a clean coal combustion technology, while the combustion of coal coke accounts for more than 85% of the total combustion process of pulverized coal. In order to investigate the effects of different factors on the pore structure and fractal properties of the blended coal coke, a low-temperature nitrogen adsorption method and scanning electron microscopy are used to study the coal coke consisting of three types of coal after pyrolysis. The adsorption isotherm analysis indicates that the pore structure in blended coal coke consisted mainly of semi-open pores with semi-cates. Petroleum coke can severely inhibit microporosity when the content of petroleum coke in the blended coal sample exceeds 10%. The microporosity distribution of blended coal coke with different blending ratios is more concentrated than that of mesopores. In addition, it is found that the trend of D1 is consistent with the trend of the ratio of the microporous specific surface area to the total specific surface area in the blended coal coke. Bituminous coal will make the blended coal coke have a complex structure and petroleum coke will make it have a smooth surface. [ABSTRACT FROM AUTHOR]

To address the problem of late ignition and poor burnout of Foster-Wheeler down-fired boilers, this study proposed a new combustion technology, which combines adding on arch secondary air and alternately arranging the fuel-lean coal/airflow (FLCA) and fuel-rich coal/airflow (FRCA). The coal particle trajectories of FLCA and FRCA and overall aerodynamic characteristics in the furnace were studied at FRCA and FLCA ratio (RRL) of 5:5, 7:3, and 9:1. The results showed that even at a low FRCA ratio, the new combustion technology could still effectively ensure the penetration depth of pulverised coal/airflow. At different RRL values, the main airflow from the arch appeared in the near-wall area and could penetrate downwards into the cold ash hopper area. With an increase in the value of RRL, the deflection degree of FLCA towards the furnace wall increased, while that of FRCA decreased. At RRL of 7:3, both the penetration depth and deflection degree of FRCA and FLCA were at a high level, which was conductive to promoting the burnout and recommended in practical applications. [ABSTRACT FROM AUTHOR]

Purpose. To develop scientific foundations and technical solutions and to implement the converting of the anthracite boiler of the 800 MW unit of Slovianska TPP with central coal pulverizing plant to sub-bituminous coal combustion with maximum use of existing equipment, without stopping the unit’s operation. Methodology. Theoretical and calculational studies on the processes of coal drying and pulverizing at the central coal pulverizing plant. Calculational justification of technical solutions to eliminate the risk of pulverized coal ignition in the pulverized coal supply system and in the boiler unit burners. Trial tests at the coal pulverizing plant and boiler unit. Findings. The technological features of coal pulverizing plant with steam panel dryers designed for anthracite and the peculiarities of the drying process of an individual coal particle were analyzed. It is substantiated that coal drying at the first stages takes place according to the “wet bulb thermometer” mechanism, and safe conditions for sub-bituminous coal pulverizing are determined and confirmed by tests. Technical solutions to eliminate the risk of pulverized coal ignition in the pulverized coal supply system and in the boiler burners were calculated and implemented, which allows the combustion of different coal grades (anthracite, sub-bituminous coal and their mixtures) without changing the composition of the air duct equipment and burners, using only operational measures. Originality. For the first time, it was proved that coal drying at the first stages takes place according to the “wet bulb thermometer” mechanism, and safe conditions for sub-bituminous coal pulverizing at the central pulverizing plant with steam panel dryers and unventilated ball drum mills were determined. Practical value. Technical solutions were developed and implemented to convert the anthracite boiler of the 800 MW unit of Slovianska TPP with a central coal pulverizing plant to sub-bituminous coal burning with maximal use of existing equipment, without stopping the unit’s operation, including safe modes of sub-bituminous coal pulverizing, as well as pulverized coal of various coal grades and their mixtures feeding and combustion. As a result of the implementation of the developed technical solutions, the 800 MW power unit of Slovianska TPP became the first unit in the world capable of using anthracite and sub-bituminous coal separately or in the form of mixtures of a wide range of compositions. [ABSTRACT FROM AUTHOR]

During deep underground coal mining, coal is typically fractured under high in situ and mining-related stresses, thus increasing the risk for dynamic disasters. However, knowledge regarding the mechanical and permeability characteristics of initially fractured coal remains limited. In this study, laboratory investigations were performed to examine the anisotropic strength, failure modes, and permeability of initially fractured coal subjected to true triaxial stresses. The results indicated that initially fractured coal can be classified into semi-brittle Class I failure modes. A new failure plane can be formed for initially fractured coal samples after failure, which was different from the intact coal samples' failure mode. The peak strength of initially fractured coal was typically observed when the maximum principal stress was subjected perpendicular to the bedding planes, while minimum values were obtained when the maximum principal stress was subjected parallel to the butt cleats. The brittleness of initially fractured coal was increased with intermediate stress. The permeability evolution curves for initially fractured coal exhibited an L-shaped trend. The pulverized coal grains in initially fractured coal can block the gas flow channel contributing to the continuous decrease in permeability. Intermediate stress exerts a more significant effect on permeability reduction when deviatoric stresses are applied parallel to cleats in coal. [ABSTRACT FROM AUTHOR]

The operational parameters of monoethanolamine (MEA)-based carbon capture were investigated and optimized based on 300 MW e co-firing power plant. The representative coal and biomasses (peanut shell, rice straw and rice husk) were employed as co-firing fuels by quantitative analysis. The stripper pressure is determined as 1.9 bar and CO 2 capture rate no more than 90% is preferred for relatively low energy consumption, and the optimal CO 2 loadings in lean solution is mainly 0.22. The key material and energy performances of the main equipment and the carbon capture system at the optimal operating conditions were comprehensively discussed. The addition of the biomass leads to more CO 2 captured as well as more thermal consumption. The optimal specific thermal requirement for rice husk-firing reaches the lowest, 3.39 MJ/kg CO 2 for 90% CO 2 removal. To capture CO 2 from flue gases deriving from biomass-contained fuels is more energy efficient compared to that from pure coal. The carbon capture system contributes ∼18–22% total energy penalty compared with the case without carbon capture system. The study devotes to the application of integrated low energy penalty carbon capture technology (CCT) with biomass co-firing technology. [ABSTRACT FROM AUTHOR]

The growing demand for rare-earth elements and yttrium (REY) in modern technologies has resulted in the systematic depletion of primary ores. For this reason, research is being conducted around the world on alternative sources of rare-earth elements, e.g., on the possibilities of recovering REY from coal waste or coal combustion. The article presents the results of comprehensive tests of the fuel—hard coal, and high-temperature HTA ash, fly ash, and bottom ash. Examined samples were taken from a Polish power plant. In the tests, fuel quality parameters were determined in accordance with the standards; microscopic observations in reflected and transmitted light, as well as a scanning electron microscope (SEM/EDS), were used, and chemical and phase composition were determined using ICP-MS and XRD methods, respectively. The distribution of REY between these ashes was analyzed. Their suitability as alternative sources of REY was assessed. The obtained results showed that the process of hard coal combustion in pulverized coal boilers influenced the geochemical differentiation of REY elements in energy waste. This differentiation is manifested by higher concentrations of REY and critical elements in the fly ash than in the bottom ash. The obtained values of the Coutl prospective coefficient made it possible to classify the analyzed fly and bottom ashes as prospective REY raw materials. [ABSTRACT FROM AUTHOR]

The co-combustion of dry coal and sludge was carried out in a self-built laboratory scale fluidized bed furnace. We used FTIR spectroscopy, high-resolution gas chromatography, high-resolution mass spectrometry, and XRF to capture and dynamically observe the flue gas fly ash and bottom ash. The sludge sample was taken from a municipal sewage treatment plant and its mixing ratio was below 20%. The temperature distribution of the furnace was observed and the emissions of the main gaseous pollutants such as SO2, NOx, and dioxins were measured in the combustion process. The heavy metal contents of fly ash and bottom ash were later detected to analyze the migration characteristics. The results showed that all of the gaseous pollutants measured increased linearly with the sludge mixing ratio. However, it could also meet the 1 metal content of bottom ash and fly ash did not change much. Through the elaboration of the above points, this study can provide guidance for future research on the co-combustion of coal boiler sludge and suggest favorable conditions for the co-combustion of coal boiler sludge. [ABSTRACT FROM AUTHOR]

The adsorption difference of water and methane by long-flame coal is compared and analyzed by molecular simulation. The results show that when the single-component isothermal adsorption pressure is less than 15 MPa, the adsorption capacity of CH4 and H2O increases gradually with the increase of the adsorption pressure, and the average adsorption amount of H2O is much higher than that of CH4; after more than 15 MPa, the average adsorption amount of CH4 and H2O is saturated. When the two-component isothermal adsorption pressure is less than 0.7595 MPa, the long-flame coal molecule can adsorb both CH4 and H2O; after more than 0.7595 MPa, the average adsorption amount of H2O is much larger than that of CH4 indicating that H2O is in a dominant position in the competitive adsorption with CH4. [ABSTRACT FROM AUTHOR]

Residual coal is easily submerged and damaged by groundwater. In the course of mining underlying coal seam, coal belonging to the overlying gob area tends to spontaneously combust during draining water. To explore the effect of micro-functional group transformation in immersed coal on the coal spontaneous combustion (CSC) traits during the low-temperature oxidation process (LTO), the migrant law of special functional groups under varying oxygen concentration (Co) of immersed coal was discussed by infrared spectroscopy. The endothermal and exothermal properties of the function group inside of coal were studied via thermal analysis. It is shown that the higher Co, the more oxygenic function groups on the soaked, and by contrasted with the Co of 18% the 14% has a small increase and the chain length is shortened. The temperature increment together with the Co content determines the functional group content, the pyrolysis process produces some function group. The lower the Co, endothermic coefficient decreases and endothermic temperature increases, the higher the ignition temperature of coal oxy-combustion, the lower the total heat release. And the speed of the oxygen-absorbing weight gain and the conversion of the functional group would be improved followed by the burnout temperature rising. Below 14% Co, the oxidative combustion process will be greatly inhibited. Those findings complement a theoretical basis for preventing long-term water-soaked coal oxidative spontaneous combusting in shallow buried coal seams. [ABSTRACT FROM AUTHOR]

A large-scale experiment on coal spontaneous combustion (CSC) was conducted to investigate the experimental spontaneous combustion period (ESCP) and limit parameters. Coal samples were collected from the Wenjiapo coal mine in the Binchang mining area in Shaanxi Province, China. Specifically, the high-temperature point (HTP) migration of coal and the variations in the oxygen consumption rate, heat release intensity, lower limit oxygen concentration (LOC), maximum air leakage intensity (ALI), and minimum residual coal thickness (RCT) during CSC were investigated. The ESCP was discovered to be 35 days. During CSC, the HTP moved from the middle of the coal body to the bottom where air was supplied. Heat release intensity and oxygen consumption rate were directly proportional to coal temperature. Under the same conditions, minimum RCT increased with ALI, lower LOC decreased as RCT increased, and maximum ALI increased with RCT. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The harmless disposal of spent cathode carbon blocks (SCCBs) has become an urgent issue in the primary aluminum industry, and the disposal of SCCBs by co-combustion in pulverized coal boilers is expected to be the most effective treatment method. A muffle furnace at 815 °C was used in this study to perform a co-combustion experiment of meager coal and SCCBs. The ash fusion characteristics (AFTs), microscopic morphology, and minerals composition of co-combustion ash were characterized. The interaction mechanism of different mineral components and the change in AFTs and viscosity-temperature characteristics were investigated using FactSage software. Results show that the change in the ash deformation temperature (DT) is correlated linearly with the SCCB addition ratio, whereas other characteristic temperatures exhibit a nonlinear relationship. The contents of SiO2, Al2O3, and Na2O collectively determine the DT in the ash, and the influence degree from high to low is in the order of SiO2, Na2O, and Al2O3. The phase diagram of Na2O–Al2O3–SiO2 is used to accurately predict the changing trend of the melting point of co-combustion ash. The ratio changes between refractory and fusible minerals in the ash, as well as the degree of low-temperature eutectic reaction between sodium- and calcium-containing minerals, are the main factors affecting the melting point of ash. When the blending amount of SCCBs is 5%, mostly complete combustion is achieved, and slagging does not occur easily. The optimal blending ratio of SCCBs is obtained using the co-combustion method from the aspect of AFTs and viscosity-temperature characteristics. This work lays a theoretical foundation for industrial application. [ABSTRACT FROM AUTHOR]

The effect of intrinsic metal mineral elements in the combustion process of pulverized coal on the formation and transformation mechanism of PM was investigated in a drop-tube furnace in air atmospheres at 1200 °C, which laid a solid foundation for the control of particulate pollutants. The results show that reducing the evaporation of mineral elements or the generated PM1 aggregating to form PM1–10 or particles bigger than 10µm can reduce the emission of PM1 in the coal combustion process. The amount of PM0.2, PM0.2–1, PM1–2.5 and PM2.5 produced by the raw coal-carrying Mg are reduced by 36.7%, 17.4%, 24.6% and 21.6%, respectively. The amount of PM10 is almost unchanged. The addition of Mg increases the viscosity of submicron particles effectively, making it easier to aggregate and bond together to form ultra-micron particles. The amount of PM0.2, PM0.2–1, PM1–2.5, PM2.5 and PM10 produced by the raw coal-carrying Ca are reduced by 36.3%, 33.0%, 42.8%, 38% and 17.7%, respectively. The effect of adding Ca compounds on the particles is better than that of Mg. The amount of PM0.2, PM0.2–1, PM1–2.5, PM2.5 and PM10 produced by the raw coal-carrying Fe are reduced by 15.6%, 16.2%, 31.1%, 22.4% and 5%, respectively. While the production of PM2.5–10 increased from 0.17 mg/g to 0.34 mg/g, it is clear that a significant fraction of the submicron particles produced during the combustion of the raw coal-carrying Fe are transformed into ultra-micron particles. After comparing the particulate matter produced by raw coal-carrying Mg, Ca and Fe, it shows that the addition of these three elements can effectively reduce the ash melting point, so that during the process of coal combustion, part of the sub-micron are transformed into ultra-micron particles, which are easy to remove. [ABSTRACT FROM AUTHOR]

In case of firing pulverized coal in power steam boiler certain fuel preparation process has to be taken in order to ensure stable and optimal combustion in boiler furnace. Before entering furnace low caloric coal is introduced from coal bunker to the coal preparation system where milling/pulverization and drying processes of raw large coal particles are conducted. For the purpose of defining fineness of grinding of pulverized coal mill gaseous mixture at mill outlet is introduced to the separator where large coal particles, separated from outgoing mill gaseous mixture, are recirculated to mill for regrinding. In this paper character of two-phase flow in inertial separator at milling plant in TPP Nikola Tesla Unit B under various operating conditions has been analyzed. The CFD approach has been used for calculating two-phase flow in separators flow domain. Measurement data taken on site along with results of performed heat balance calculations of milling plant have been used for validating calculation model as well as for setting appropriate boundary conditions in CFD model. The CFD calculations has been performed for different positions of all regulating flaps, recirculation rates of gaseous phase and values of specific weight of solid phase in two-phase mixture. For evaluating separators operating performance at different operating regimes changes of milling capacity and fineness of grinding of pulverized coal at separators outlet have been observed. Additionally, deviation rate of trajectories of different-sized particles to the streamlines of gaseous phase has been examined. [ABSTRACT FROM AUTHOR]

Pulverized coal (PC) pyrolysis is an indispensable process for coal thermal conversion and utilization. The transformation of fuel-N into fast pyrolysis is a basis for the investigation of nitrogen migration in coal combustion. In this paper, a wire mesh reactor was used to study the initial decomposition processes and to reveal the final pyrolysis yield and composition distribution during the fast pyrolysis process. Furthermore, the initial pyrolysis characteristics of PC with different ash contents were presented and compared. The results showed that both Huangling coal (with higher volatile) and Wuhai coal (with higher ash content) showed a similar trend, and the pyrolysis ratio increased with the increased pyrolysis final temperature. The pyrolysis ratio at the high heating rate was estimated to exceed that at the low heating rate by 2%–10%. With the temperature increased, the char-N yield decreased first and then tended to be stable, and most of nitrogen remained in the char (more than 55%). An increase in heating rate made the pyrolysis zone to shift toward higher temperature, and it enhanced the yields of volatile and tar as well as the proportion of tar in volatile. Besides, the heating rate increased from 10°C·s−1 to 1500°C·s−1, the yield of tar-N increased from 4% to 14% and gas-N decreased from 28% to 19%. Overall, NH3 yielded was higher than HCN, which became more apparent at high heating rates. The content of the N-6 was positively related to the coal pyrolysis ratio. [ABSTRACT FROM AUTHOR]

One of the ways to minimize anthropogenic emissions from coal combustion is to replace conventional schemes used for the introduction of coal dust into the furnaces of power plants through the injection of water-containing fuels. In this research, the three most promising schemes for fuel combustion were implemented: (i) the simultaneous introduction of coal particles and water droplets into the combustion chamber; (ii) steam injection into the fuel particle combustion zone; and (iii) the introduction of coal–water slurries into the furnace. Three methods of supplying water to the combustion zone were evaluated using the multi-criteria decision-making technique. Experimental research was conducted to record a range of process characteristics: the time of the gas-phase and heterogeneous ignition, the time of complete combustion, minimum ignition temperatures, maximum combustion temperatures, the completeness of the fuel burnout and the concentrations of the main gaseous emissions. It has been found that the most favorable scheme for coal particle combustion in water-steam environments is to produce fuel slurries. The cumulative indicator integrating the energy and environmental characteristics is 7–47% higher for slurries than for the other examined schemes for burning coal particles and slime. [ABSTRACT FROM AUTHOR]