Anthracite Research Articles

Research on the rational profile of exit trails of auto transport in deep open mines

Purpose. Technical and economical justification of the parameters of the profile of exit trails without horizontal sections in the operation of road transport in deep open mines. Methodology. To solve the objectives, the following methods were used: analytical, graphic methods, mathematical modeling, comparison of options, and analogies. These research methods are used when studying and justifying of a rational profile of exit trails of auto transport in the open mine, as well as defining the width of the working platforms of the excavator, and doing technical-economical calculations of the proposed solutions. Findings. Based on the performed analysis of parameters determining the distance of transportation of rock mass, it was found that when using the exit trails without horizontal sections, the transportation distance is 300 m, and with horizontal sections 531.3m, which exceeds the former by 1.77 times. The trip time when using the transportation scheme without horizontal sections is 7.44 min, and when using it with horizontal sections, it is 8.42 min. It is proved that the use of exit trails without horizontal sections in the open mine of Poltava Mining and Processing Plant reduces the cost of diesel fuel by 42.57% and capital costs by 40.5%. Originality. A comparison of the actual distance of transportation, and time of dump truck trip by component operations is carried out, and expenses for maintenance of open mine roads when using trails with horizontal sections and without them are calculated. The scheme of exit trails without horizontal sections has been offered for the first time, which allows a reduction in the distance of transportation of rock mass by dump trucks with a reduction of rock volume for carrying out conventions by 57%. Practical value. The developed scheme of the route profile without horizontal sections can be applied to overburdening operations, and the development and deepening of open mines for the extraction of different types of minerals, such as iron ore and hard coal. The expected economic effect from the introduction of trails without horizontal sections is determined by the reduction of diesel fuel costs by 52.9 UAH/t.km, and accordingly 1.68 million UAH for the conduction of conventions.

The Prospect of Recovering Vanadium, Nickel, and Molybdenum from Stone Coal by Using Combined Beneficiation and Metallurgy Technology Based on Mineralogy Features

Black shale ore contains rich strategic metal resources such as vanadium, nickel, and molybdenum, but due to its complex composition, it is currently only used in the vanadium extraction industry. Metals such as nickel and molybdenum have not been effectively recovered, resulting in environmental pollution and resource waste. Using mineralogical features and a combination of beneficiation and metallurgy-based tests, the present work carried out feasibility studies of the combined beneficiation and metallurgy processes. The mineralogical features of the stone coal sample were studied using chemical analysis, an automatic mineral analyzer (BPMA), etc., and we identified the main phase composition, embedded characteristics, and particle size distribution of the associated strategic metals, vanadium, nickel, and molybdenum. The results showed that the grade of V2O5 in the stone coal was 1.29%, which was mainly present in carbonaceous clay and mica minerals. The nickel grade was 0.53%, mainly in the form of nickel–magnesium spinel and a small amount of nickel-containing magnesite. The stone coal contained 0.11% molybdenum; the mineral particles were fine, mostly in the form of molybdenite, and some were associated with carbonaceous matter and carbonaceous clay minerals. Based on the mineralogical feature, we proposed using the scrubbing–desliming and flotation process to enrich vanadium, nickel, and molybdenum. Our preliminary experiments obtained two products: vanadium–molybdenum-rich sludge and nickel-containing tailings. The V2O5 and molybdenum grades in the sludge were 4.10% and 0.44%, respectively, and the recovery was 41.31% and 51.40%, respectively. The nickel grade in the tailings was 1.49%. These products were roasted and leached. The vanadium, nickel, and molybdenum in the stone coal were effectively recovered through the beneficiation–metallurgy combination process, and the comprehensive utilization rate of the stone coal was improved.

The Effect of Silicon-Containing Minerals on Coal Evolution at High-Temperature Pre-Graphitization Stage

Coal is a carrier of carbon enrichment, so it has the potential for the preparation of coal-based carbon materials. In this paper, LT anthracite and TSG bituminous coal were selected, and the corresponding graphitized samples were prepared from high-temperature treatment. The effects of silicon-containing minerals on coal evolution during the high-temperature pre-graphitization stage were investigated by XRD, Raman spectroscopy, and SEM. The results showed that with increasing temperature, the silicon-containing samples showed smaller d002 and ID1/IG, and higher Lc, while La presented a slight increase. It was found by SEM that the micromorphology of all samples was mainly massive structures. Meanwhile, irregular polyhedral structures also were observed in silicon-containing samples at 1300 °C, which were related to the formation and deposition of SiC. The carbothermal reactions of silicon-containing minerals continued to generate SiC and precipitate with increasing temperature, resulting in the gradual transformation of the needle-like structures into polyhedral structures. However, SiC was completely decomposed at 2800 °C. These changes indicated that during the pre-graphitization stage, silicon-containing minerals form SiC to advance the reduction of the interlayer spacing and the increase of longitudinal layer stacking height, thereby enhancing structural ordering and graphitization degree, while it had less effect on the lateral size. This will help to further understand the role of silicon-containing minerals in the coal pre-graphitization stage and also provide useful information about synthetic coal-based graphite.

Bioleaching and biosorption behavior of vanadium-bearing stone coal by Bacillus mucilaginosus

Bioleaching and biosorption behavior of vanadium-bearing stone coal by Bacillus mucilaginosus

Experimental Study on Gas Loss Derived from Positive Pressure.

Positive pressure sampling enables the fixed-point and rapid acquisition of coal samples, but the derivation of loss volume during sampling is usually based on the law of gas desorption from granular coal at atmospheric pressure, which seriously affects the reasonableness of loss amounts under positive pressure and thus leads to errors in gas content determination. The gas loss under positive pressure is the key to the accurate determination of the gas content of coal seams. To obtain reliable loss data, under different positive pressures, we tested the gas desorption process of anthracite coal samples with different adsorption equilibrium pressures, analyzed the effect of positive pressure on gas desorption, studied the changes in the gas desorption rate caused by positive pressure, recorded the fluctuation of the amount of gas loss, and compared the values of loss under different conditions. The results show that the positive pressure is the main factor affecting gas desorption compared to the adsorption equilibrium pressure. The positive pressure has an inhibitory influence on gas desorption. Under the same positive pressure, the gas desorption rate shows a decreasing trend over time, and at the same time, the gas desorption rate gradually decreases accompanied by the increasing positive pressure. The gas loss error rate increases with increasing adsorption pressure under the same positive pressure. However, under the same adsorption pressure, the error rate of loss quantity presents a significant increase with positive pressure. The relative error of gas loss under different positive pressures can reach 63-180%, and the positive pressure has an obvious influence on gas loss. This study has experimentally confirmed that positive pressure has a greater effect on gas desorption than adsorption pressure, which will theoretically improve the method of deriving the amount of gas loss and will provide a basis for the accurate determination of gas content under positive pressure in engineering terms.

Tracking sources of PM10 emissions and deposition in the industrial city of Ostrava, Czech Republic: A carbonaceous δ13C-based approach

The sources of airborne particulate matter (PM10) emissions in Ostrava, Czech Republic, were investigated. Emphasis was placed on their organic carbon (OC) and elemental carbon (EC) contents, and their carbon stable isotope composition, δ13C. Emission sources were identified using OC-δ13C and concentration values. To track the extent of long-term deposition, these sources were also identified using the black carbon (BC) δ13C values of soil samples. At all sampling sites, wind flow is predominantly (65–80%) bidirectional in either SW-NE or NE-SW trajectories. Source apportionment along these dominant airflow trajectories was calculated from an isotopic 13C mass balance, and according to differences in the OC content and δ13C values of PM10. Determined emission sources are: (i) combustion of Silesian hard coal (δ13C = −24.5‰); (ii) local Ostrava coal combustion (δ13C = −25.5 to −26‰), automotive emissions (δ13C = −26.5‰), and biogenic particles (δ13C = −28 to −28.5‰). Winter emissions (mean OC concentrations from 12 to 25 μg m−3) originated mostly from coal combustion (80%) in domestic and industrial point sources. Differences were ascribed to automotive emissions. Ostrava is located near the Czech-Polish border, transboundary emissions are transported under a southbound wind flow that transported from 40 to 80% of the collected PM10. Summer emissions were lower (mean OC concentration from 6 to 8 μg m−3). Automotive emissions accounted for up to 40%, whilst biogenic production accounted for 60%. Absence of 13C isotope data of secondary OC (SOC 1.2–1.5 μg m−3) increases uncertainty in our source apportionment in summer; when SOC could comprise >20% of total OC. Contribution of SOC to the winter-measured OC is much lower (5–10%), and has no significant effect on mass balances. The upper soil layer analyses revealed long-term deposition of the same emissions sources. We conclude that the stable δ13C isotope values of OC and EC are useful for discriminating against local sources of PM10 pollution in relatively small urban areas, containing discrete polluting sources. Such a simplified approach can be easily standardized and implemented to manage regulatory compliances in the increasingly commoditized carbon offset market.

Study on the reactions and alkali metals radiation characteristics from different coal ranks of a single coal particle flame

In this work, the combustion progress and alkali metals radiation characteristic of the different coal ranks (NaoMaoHu (NMH) lignite coal, YangChangWan (YCW) bituminous coal and SiHe (SH) anthracite coal) are studied in a visualization drop tube furnace (VDTF) by a high-speed camera and a hyper-spectral camera. The effects of different coal ranks on the alkali metal (Na*, K*) radiation characteristics in the volatile and char reaction stage are explored at the oxygen concentration (Xi,O2) ranging from 0.2 to 1.0. In addition, the flame temperature of the different coal ranks is further calculated by alkali metal spectral intensity. The results show that in the volatile reaction stage, the NMH Coal is homogeneously ignited and the coal particle shows the fragmentation behavior. The YCW coal shows a hetero-homogeneous ignition, and SH Coal particles are heterogeneously ignited with a black spot in the center of the particle. During the char reaction stage, the three coal particles are ignited heterogeneously. As the reaction proceeds, the flame size and brightness of the three coal particles first increase and then decrease. The Na* and K* peak intensity and volatile reaction time of the different coal ranks have the relationship that NMH Coal > YCW Coal > SH Coal, because the volatile content of YCW Coal and SH Coal is lower than that of NMH Coal. Besides, the trend of flame temperature variation agrees with the alkali metal spectral intensity for different coal ranks. When Xi,O2 is 0.2, only one release peak of Na* and K* occurs, and the flame temperature varies from 1600 K to 1950 K. When Xi,O2 is greater than 0.4, the three coal particles show two Na* release peaks and the flame temperature varies from 1650 K to 2100 K. This paper provides insight on the effects of flame temperature and alkali metals radiation characteristics on reaction process of different coal ranks.

Research into Impact of Leaving Waste Rocks in the Mined-Out Space on the Geomechanical State of the Rock Mass Surrounding the Longwall Face

Backfilling technology is not always used by mining enterprises, which is conditioned by technological and economic factors, such as the need for high mining rates and costs for the technological processes of transporting backfill materials from the daylight surface to the mined-out space. This concerns the underground mining of hard coal, which is a strategic energy resource, in the mines of Ukraine. This paper aims to study the effect of leaving the waste bottom rocks in the mined-out space of the longwall face without their drawing to the earth’s surface on the geomechanical state of the rocks surrounding the longwall face. The geomechanical assessment of the stress state of the rock mass surrounding the longwall face, when leaving the waste rocks from the seam bottom rocks in the mined-out space, is performed by the finite element method using the Ansys software package. A geomechanical model has been developed and substantiated, which adequately reflects the mining-geological conditions for seam mining within the extraction site, the actual structure and properties of the coal-bearing rock stratum, the parameters of the longwall face and the modified powered support for the processes of leaving the rocks in the mined-out space. The values and patterns have been determined of the decrease in the stress intensity concentrations in the coal-bearing roof mass in the frontal bearing pressure zone and destressing zone with an increase in the ratio of the rock pack thickness to the extracting seam thickness. The relative indicators of the load on the powered support section and the lowering of its roof have been determined by the ratio of the thickness of the rock pack formed in the mined-out space to the extracting seam thickness. The proposed mining method is of significant commercial and research interest for owners of coal mines developing thin coal seams because environmental costs for placing waste on the surface are reduced, and the energy potential of coal is increased due to the separation of waste rocks from coal in underground conditions. The need for a cycle of beneficiation of mined mass is eliminated and the geomechanical conditions of coal mining processes are improved.

Elemental composition and mineralogy of NW Venezuelan Guasare coals: Provenance study and role of illite in methane sorption capacity

A series of coal seams (groups 4 to 11) of Paleocene age in the Marcelina Formation have been open pit exploited in two mines (Paso Diablo and Mina Norte) in the Guasare Coalfield (NW Venezuela). An investigation has been conducted on the elemental composition, mineralogy, and coalbed methane (CBM) in Guasare coals. For this study, 46 core coal samples of 16 seams (groups 2 to 7) were collected from 16 exploratory boreholes that were drilled in both mines. It was also considered unpublished proximate-ultimate and gross calorific data of other 66 coals of 31 seams intersected in most of these wells. The coals under study showed low ash yields (3.4 wt % on average) and were classified as high volatile bituminous A. Mean values of trace element and lanthanide (REE) contents in Marcelina coals generally indicate depletion compared to average values for world hard coals. The statistical evaluations indicate that elements (except Se) show inorganic affinity or intermediate association and mixed mode of occurrence. La/Sc, Th/Sc, La/Co, and Th/Cr ratios support a felsic or metamorphic felsic source for the mineral matter present in Marcelina coals. Most coal samples exhibited similar normalized REE patterns, showing light REE enriched, as well as negative Ce and Eu anomalies. The comparison of REE patterns to those of some nearby granitoids suggests that Marcelina coals received a supply of sediments from theses granitic source rocks. The mineralogical compositions of representative coal samples are notably similar, kaolinite and quartz were noted as the major mineral species in all coal seams. The measured gas volumes available for CBM production from Marcelina seams vary approximately between 5 and 11 cm3/g. Variation in the illite content has an appreciable positive effect on gas adsorption capacity of Guasare coals. Lastly, a numerical model of the gas generative potential of the coals in the Marcelina Formation was also developed.

Molecular simulation study on the effect of coal metamorphism on the competitive adsorption of CO2/CH4 in binary system

To explore the competitive adsorption characteristics of a CO2/CH4 binary gas in coal with different metamorphic degrees, macromolecular-structure coal models with different metamorphic degrees (anthracite coal, coking coal, and long-flame coal) were constructed based on elemental analysis, X-ray photoelectron spectroscopy (XPS), and carbon-13 nuclear magnetic resonance (13C NMR) results. Then, the competitive adsorption behaviors of CO2 and CH4 molecules in the different coal molecular models were simulated using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods, and the changes of the competitive adsorption capacity, density distribution, adsorption selectivity, adsorption heat, and energy distribution were investigated. The results showed that the variation characteristics of the total adsorption of mixed gas were similar to those of pure gases, and the increase in the pressure led to an increase in the total adsorption, which also increased with the increase in the coal deterioration degree. The distribution ranges of the gas adsorption sites in coal with different metamorphic degrees were significantly different, with anthracite coal being the most widely distributed and long-flame coal being the least widely distributed. With the increase in the coal rank, the competitive adsorption selectivity of any proportion of CO2/CH4 binary mixed gas increased. The difference in the equivalent adsorption heat of single-component gases CO2 and CH4 in the mixed gas increased with the increase in the coal metamorphism and decreased with the increase in the CO2 gas proportion coefficient. This paper provides a theoretical basis for the application of CO2 enhanced coal bed methane in coal seams with different metamorphic degrees.

Dynamic model of a longwall shearer with a chain haulage system

Despite the pro-ecological policy, hard coal still is and for a long time will remain a valuable major source of energy in the world. It is usually found in the form of seams in underground mines. For many years, thin coal seams have been exploited on an increasingly large scale, therefore mines and machine manufacturers are looking for new, effective and safe methods of extraction. One of such methods is the use of a longwall system with a single-head shearer. This solution has been briefly described in the article, with special focus placed on the proprietary dynamic model of a longwall shearer with a chain haulage system. The model concerns a chain-hauled single-head shearer, but can be used to simulate coal ploughs, and to a certain extent, scraper and belt conveyors. There are models in the literature in which the chain is replaced by point masses. In the discussed model, the chain segments have been described as a continuously distributed mass, the value of which changes as the shearer travels along the wall. The shearer has been modelled as a rigid body with six degrees of freedom, placed on elastic skids. The load from cutting, loading and movement resistance has been taken into account in the model. The mathematical model has been saved in the form of scripts in Matlab. The set of scripts allows obtaining information about the behaviour of the shearer and the load on important structural nodes such as skids, chain and loaders fasteners or the driving shaft of the cutting head. The results also enable determining the power demand of the motors as well as calculating the required initial tension of the chain. The fully parametric model makes it possible to analyse the influence of a change in the values of significant parameters of the longwall working, drive units and shearer. This information is crucial at the stage of design construction and verification, which allows avoiding many errors in the prototype.

Applying CFD Model Studies to Determine Zones at Risk of Methane Explosion and Spontaneous Combustion of Coal in Goaves

Underground mining operations are subject to a number of natural hazards. Events resulting from these hazards are difficult to predict, and if they occur, they disrupt the entire mining process and pose a great danger to the crew. Some of the most dangerous include ventilation hazards involving methane explosions and fires caused by the spontaneous combustion of coal. The complex state of the underground environment means that these hazards oftentimes occur simultaneously, making mining conditions even worse. The following paper addresses this issue by developing methodology for determining areas endangered by methane explosions and coal spontaneous combustion in goaves. The reference to goaves results from the fact that this particular area is most frequently affected by coal spontaneous combustion and accumulation of dangerous amounts of methane. The developed methodology was based on model tests with the use of the CFD method and data necessary to develop a numerical model. The research encompassed a real longwall in one of the hard coal mines, ventilated with the Y system during its exploitation, which is beneficial in the case of the methane hazard but worsens the safety in terms of the self-ignition of coal. As a result of the conducted research, for the exploitation conditions, dangerous zones were specified due to a potential possibility of methane explosion and self-heating of coal. The basis for determining dangerous zones were the criteria of occurrence of the examined phenomena. In this study, the zones were identified for each of the investigated hazards separately and for their simultaneous occurrence. Thus, the aim of the study, which involved the determination of potentially hazardous zones by applying modern methods of modelling in the mining area, was achieved. The results are an immensely important source of information for activities aimed at improving safety in the studied area, in relation to the studied threats.

Experimental study on the mechanical properties, permeability characteristics, and energy evolution of gas-containing anthracite coal under different loading–unloading speeds

In the coal mining process, the stress state of a coal seam will change due to coal-mining-induced unloading, which may lead to the occurrence of coal and gas outburst disasters. According to the change of stress characteristics of the coal seam, the mechanical properties, permeability characteristics, and energy evolution of gas-containing anthracite coal at different loading–unloading speeds were analyzed in this study. The result shows that the strength of anthracite coal samples under different loading–unloading speeds increases with increasing initial hydrostatic pressure and decreases with increasing loading–unloading speeds, presenting the power function relationship. Moreover, the higher loading–unloading accelerated the damage rate of coal samples, resulting in a rapid increase in permeability, which has a significant influence on the emergence of coal and gas outburst. Furthermore, the energy evolution characteristics of coal samples were influenced by the loading–unloading speed, the increase in the loading–unloading speed reduces the total energy, and dissipating energy of the coal sample at the point of failure. The study is of great significance for reducing the occurrence of coal and gas outburst disasters and providing a basis for the design of mine gas drainage.

Deep-lying sites of the house-cricket Acheta domesticus (Linnaeus, 1758) (Orthoptera: Gryllidae) in coal mines in Upper Silesia (Poland)

The report provides information about the occurrence of the house-cricket Acheta domesticus in 2021 in the area of the hard coal mines "Budryk" (Ornontowice) and "Pniówek" (Pawłowice). The species was recorded at depths of 900, 1050 and 1290 m ("Budryk") and 1050 m beneath the surface ("Pniówek"). The information provided testifies high adaptability of the species and encourages its search in other Polish mines.

A unique type of industrial railway – the sand railways of southern Poland

Abstract Since the mid-twentieth century, the Polish rail network has been experiencing a systematic decline of its lines and this includes railway lines serving only freight services. One of the most striking examples of freight transport is the sand railways in southern Poland. This world-unique system for transporting backfill sand used in hard coal mining was one of the most spectacular types of specialized rail transport. The general crisis of railways in Poland, the restructuring of the hard coal mining industry and changes in the technology for securing the underground parts of mines, have all resulted in a sharp decline in the role of sand railways as the carrier of backfill sand. The infrastructure system, as well as the companies involved in the exploitation of sand and its transport, have had to face the fundamental question about their future. This article indicates the essence of these challenges in the context of the role of sand railways in the freight rail system in general. The function of sand railways in the rail transport system has been recognized in relation to their specific unique features that have constituted important elements of their functional and spatial existence.

Occurrence Patterns and Enrichment Influencing Factors of Trace Elements in Paleogene Coal in the Fushun Basin, China

The occurrence forms of trace elements in coal are of great significance for the clean utilization, abnormal enrichment, and recovery of beneficial elements in coal. The Fushun Basin in Northeast China has thick coal deposits which provide a good opportunity for studying their geochemistry. This study aims to estimate the element enrichment of Paleogene coal seams and their influencing factors during deposition based on statistical and geochemical analyses. Compared with world hard coals, coals in the Fushun Basin feature enrichment of Ga and Sb (CC > 5), slight enrichment of V, Cr, Co, Ni, As, Rb, Zr, Nb, and Cd (2 < CC < 5), and depletion of B, Tl, Bl, and U (CC < 0.5). The CC values of the remaining elements (0.5 < CC < 2) are close to the average values for world hard coals. The main carriers of Ga, Co, Rb, Mo, As, Se, Pb, V, and Li are potassium, iron, and sulfate minerals and those of Cd, Cr, Ni, Sb, Th, Sn, U, Hf, Zr, Cs, Ta, and Nb are clay minerals. The CIA, Sr/Cu, Rb/Sr, and Ga/Rb values suggest that the studied coal seam formed under humid/warm climatic conditions. The coal seam is mainly derived from intermediate source rocks and sandstone or mudstone source rocks which were exposed to intensive chemical weathering and deposited in a freshwater setting. Additionally, paleoweathering, paleoclimate, detrital input, and provenance all contributed to the enrichment of geochemical elements in the studied Paleogene coal. The results of this study are preliminary, and the authors will continue to conduct mineralogical analysis.

The Instability Characteristics and Displacement Law of Coal Wall Containing Joint Fissures in the Fully Mechanized Working Face with Great Mining Height

Coal wall rib-spalling is regarded as a key technical problem influencing safe and efficient mining of fully mechanized working face with great mining height (FGH) while the coal wall stability is influenced by the strength of the coal body, of which the internal joint fissures have a crucial impact on the strength of the coal body. This research attempted to explore how the coal wall stability of FGH is influenced by the occurrence of joint fissures. This paper uses physical and numerical simulations to systematically analyze the instability characteristics and displacement law of FGH. Research results show that the form and scope of the instability of coal wall rib-spalling depend on the state of the coal seam joint fissures development area, and the development state of coal seam joint fissures is related to the combination of the coal seam joints; under the condition of hard coal, the coal wall stability is better at the inclination angle of 90°, and less stable at 45° and 135°; under the condition of medium-hard coal and joint surface inclination angle of 45° and 135°, the smaller the spacing of joint surface, the larger the area of the working face rib-spalling, and the less stable the coal wall.

A novel method for determining water saturation of porous media in relative permeability measurement using DPT

Relative permeability is essential for understanding porous media’s gas and water seepage characteristics and establishing production schedules in practical engineering applications. However, the movable water is too small to be detected in ultra-lowpermeability rocks, and it is difficult to determine the water saturation in the relative permeability measurement accurately. In this study, a differential pressure transducer (DPT) was applied to self-developed apparatus to quantify displaced water precisely. The results indicate that: (a) both the permeability and the relative permeability measurement results show high stability in repeatability tests with the application of DPT. (b) The final cumulative water flow data measured by the DPT is reliable; the relative error of the electronic balance and DPT value was less than 4%. (c) This self-developed instrument can obtain the relative permeability curve for ultra-low permeability rocks, such as tight sandstone and anthracite coal. Although there are limitations, this technique provides an economical and reliable pathway for studying the seepage characteristics of gas and water in ultra-low permeability rocks.

Co-firing characteristics and fuel-N transformation of ammonia/pulverized coal binary fuel

As a feasible way to decarbonize coal combustion under the background of carbon neutrality in recent years, ammonia co-firing with pulverized coal is receiving considerable critical attention from the academic and industrial communities. This paper investigates the effects of coal type, NH3 injection mode, temperature, excess air ratio (α) and NH3 co-firing ratio (ENH3) on combustion characteristics and fuel-N transformation of ammonia/pulverized coal in a 6 kW drop tube furnace. Emission of O2, CO2, CO, NO, NO2 and NH3 at the furnace exit was monitored online. The unburned carbon (UBC) content and elementary composition in fly ash were also tested. Results show that NOx generation behaviors of premixed and staged modes are significantly different. Typically, NOx emission peaks at ENH3 = 20 % under high temperature and staged mode. As for NH3/coal cases at 1000 °C, NOx level is even lower than pure coal combustion, but NH3 residue is higher. The water gas shift reaction (WGSR) under fuel-rich condition generates more CO, and the conversion ratio from fuel-N to NOx decreases when α diminishes. Ammonia co-firing can achieve lower CO emission with anthracitic coal from Gongyi (GY-coal) while lower NOx emission with bituminous coal from Inner Mongolia (IM-coal). Ammonia co-firing can considerably improve the transformation from fuel-N to N2. From the perspective of emission control and decarbonization, ENH3 = 40 % is an optimal ammonia co-firing ratio which not only can reduce half of CO2 but also brings the conversion ratio from fuel-N to NOx and residual NH3 to the minimum level. The micromorphology of ash samples is greatly affected by coal/ammonia co-firing. In premixed mode, the surface of ash sample is porous and adhered to each other; while in staged mode, obvious fractures and cuts exist between the ash particles due to the sharp decrease of local gas temperature.

INFLUENCE OF SALTS OF HEAVY METALS Pb AND Cd ON THE VEGETATIVE INDICATORS OF TRITICUM AESTIVUM

The Ukrainian energy and fuel sector is highly dependent on mineral extraction. Hard coal accounts for 25-30% of mineral production in Ukraine. All processes, from coal mining to its use for energy, have a negative impact on the environment. One of these impacts is the accumulation of waste rock at an industrial facility, known as a coal dump. These dumps have a negative impact on all spheres of the environment. Coal dumps located in Western Donbas are characterized by a low pH level, a low level of specific electrical conductivity of the soil, a low level of nutrients and a high concentration of heavy metals. Among the main dangerous toxic elements are Pb and Cd, the concentration of which exceeds more than 2 times the maximum permissible concentration. According to the results of the study, it was established that Triticum aestivum has shown itself as a phytoremediator plant resistant to heavy metals such as Pb and Cd, which makes it available to further use for planting contaminated areas of coal dumps.