Coal Feed Research Articles

Computer-Aided Design and Fabrication of a Dry Wind-Sifter Separator.

In this study, the simulation of a newly designed wind-sifter separator for dry beneficiation was deployed to upgrade −6.7 + 3.36, −3.36 + 1, and −1 mm coal. The wind-sifter principle is very effective for particle separation as it is based on the separation of lighter particles from heavier ones. First, the study entails computer simulations by utilizing the Lagrangian particle tracking method to observe the effectiveness of the wind sifting principle in separating particles based on their density in an air stream. From the three particle size fractions used, the simulation test results show that at a cut-point of 1.5 RD, yields of 29.1, 54.3, and 99.4% were attained at different optimum velocities for −6.7 + 3.36, −3.36 + 1, and −1 mm, respectively. The effect of operating parameters such as the mass flowrate and air velocity on yield, ash content, and calorific value were determined using the fabricated separator. A preliminary experimental study showed that the separator was effective in upgrading the feed coal with 30.28% ash content and 21 MJ/kg calorific value to clean coal with 18.94% ash content and 26.8 MJ/kg calorific value. A laboratory-scale wind-sifter separator was fabricated based on the results from the simulation test, which served as the first applied prototype in the field of dry coal beneficiation.

ОПЫТ СОВМЕСТНОГО ПРИМЕНЕНИЯ СОРБЕНТОВ И ПРОБИОТИКОВ ПРИ ВЫРАЩИВАНИИ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ПТИЦЫ

The studies were carried out in the conditions of ZAO PPF “Kavkaz” of the Krasnodar Territory. The article presents results of studies on separate and combined usage of active coal feed additive (ACFA) as a sorbent and “Sporothermin” probiotic for development of muscles and internal organs of broiler chickens of “Cobb-500” cross. The studies were carried out in accordance with the “Methodology for conducting scientific and industrial research on agricultural poultry.” At the end of the experimental period, the development of the muscles and internal organs of the bird was studied. In the course of the experiment, the survivability of the bird, the increase of live weight, and the cost of feed were also determined. As a result of the studies, it was revealed that the use of a probiotic and a sorbent increases the live weight of an un-gutted carcass by 5.0-8.7%. With the combined application of a sorbent and a probiotic, the mass of the glandular stomach was significantly increased by 0.15 abs. % (P <0.001). Intestinal mass significantly grew up with application of ACFA sorbent by 0.42 abs. % (p <0.05). Intestinal length evidently decreased by 8.5% (p <0.001) when using “Sporothermine” probiotic. It should be noted that the mass of the thigh muscles significantly increased by 29.0% (p <0.05) in the second experimental group with usage of ACFA, in relation to the control. At the end of the experiment, the live weight of poultry increased by 4.2% (p <0.01) in the second group with ACFA application. In the third group, where “Sporothermin” was used, the live weight grew up by 9.0% (p <0.001). In the fourth experimental group, which was fed with both the sorbent and the probiotic, the best results were obtained and the live weight significantly increased by 9.7% (p <0.001). Over the entire experiment period, feed costs per unit of production have been reduced by 4.3- 8.6%. The survivability of the poultry population was 94.4% in the control. In the second and third groups, the survival rate was also high and exceeded the control by 3.0%, in the fourth - by 5.6%.

Parametric Study on Co-Feeding of Municipal Solid Waste and Coal in an IGCC Power Plant with Pre-Combustion Carbon Capture

Municipal solid waste (MSW) is one of the top contributors in greenhouse gas (i.e. methane) emissions - particularly from landfill disposals. However, it could be a remarkable source of renewable energy. In Bangladesh, generation of municipal solid waste is at least 2.7 million tonne per year in the major cities, implying a heavy environmental burden. On the other hand, there are several coal-based power plants are in the pipeline to meet the increasing energy demand in Bangladesh with the potential of significant CO2 emission. To find a remedy to the above situation, a power plant using Integrated Gasification and Combustion Cycle (IGCC) technology with pre-combustion carbon capture is considered in this study. IGCC has the advantage of producing high quality syngas from a wide variety of feed and assists in the capture of CO2 at a lower cost while providing high electric efficiency. The power plant was simulated by commercial simulation packages (Aspen PLUS™ and Aspen HYSYS™) using MSW and bituminous coal (Indonesian) as a combined feed. With a feed rate of 1800 tonne per day, Syngas produced from an entrained flow type gasifier was then treated for CO2 removal using mono-ethanol amine (MEA) solvent after necessary shift in a high temperature shift reactor. About 91% efficiency was achieved in the shift reactor while the CO2 capture efficiency was varied for this study from 30% to 85%. Further parametric variation was studied by varying the moisture content of MSW and MSW to coal feed ratio. Through combustion of the H2 rich syngas in a gas turbine and subsequent steam cycle with reheat resulted in 125 MW of electricity at an efficiency of 28.95% while capturing 50% of the CO2 generated in the process for an MSW to Coal feed ratio of 1:1. With variation in moisture content especially during monsoon season, the plant efficiency could be affected remarkably. On the other hand, it was observed that the energy requirement varied from 6 to 8 MW for every 10% increase in CO2 capture quantity. Overall, by capturing 50% of the generated CO2, it is possible to reduce the emission of a same size ultra-supercritical coal-based power plant from about 700 kg CO2/MWh to about 360 kg of net CO2/MWh incorporating co-feeding and pre-combustion capture in an IGCC power plant.
 Chemical Engineering Research Bulletin 21(2020) 37-42

An Approach to Simulate Vapor Phase Reactions of Coal Volatiles in a Reducing Section of the Two Stage Entrained Flow Gasifier with a Detailed Chemical Kinetic Model

The present study further develops an approach in predicting reactions undergone by coal volatiles in a reducing section (reductor) of an air-blown two-stage entrained flow gasifier toward designing a better gasification process. A detailed chemical kinetic model was first applied to simulate chemical reactions of a complex molecular mixture of the coal volatiles evolved due to rapid pyrolysis of coal fed into the reductor. The composition of volatiles was determined based on pyrolysis-gas chromatography experiments, where 22 compounds including inorganic gases (H2, H2O, CO and CO2), light hydrocarbon gases (C1–C4) and aromatic hydrocarbons (benzene to pyrene) were identified. Gas composition at the reductor inlet was estimated by integrating the information on the experimentally obtained molecular composition of the volatiles, and the thermodynamically calculated composition of inorganic gases generated from the combustor and the coal feeding rates into reductor and combustor. Concentration profiles of the individual chemical species, as well as soot particles along with the flow direction of the reductor, were revealed by using an extended detailed chemical kinetic model involving 202 species, 1,351 gas-phase reactions and 101 surface reactions for soot formation and growth. The simulation highlighted that near-complete decomposition of tar (<1.5 mg/Nm3) regarded as a set of all aromatic hydrocarbons is likely to require operation temperature of the reductor at temperatures as high as 1,200°C, when the combustor is operated at 1,800°C.

Eulerian-Lagrangian simulation study of the gas-solid reacting flow in a bubbling fluidized coal gasifier

A reactive multiphase particle-in-cell approach is developed to explore the air-blown coal gasification in a bubbling fluidized bed reactor. The model is validated by comparing the predicted bed hydrodynamics and product yields with experimental data. Subsequently, the gas thermal properties and particle-scale behaviours are comprehensively explored. The results show that: (i) the density difference between two solid species gives rise to spatial segregation, which further affects the gasification process. The presence of coal feeding port causes the non-uniform distribution of bed hydrodynamics. (ii) the combustible gases species distribute above the coal feeding port. The concentration of gas species continuously increases while the gas temperature changes little in the dense region. (iii) the slip velocity of sand particles ranges from 0 to 4 m/s; the temperature ranges from 1000 K to 1150 K, and the heat transfer coefficient ranges from 80 W/(m2·K) to 200 W/(m2·K). Compared with sand, coal particles have a larger heat transfer coefficient and particle Reynolds number (Rep). Coal particles reach the maximum temperature of about 1100 K in the period of 3 s after being injected into the bed. (iv) bubble and emulsion phases give a larger Rep and smaller Rep due to the dominant role of the interphase drag force and inter-particle collision force, respectively.

PAHs in feed coals and fly ashes from coal-fired thermal power plants in Bulgaria

The first thorough study of PAHs in feed coals and FAs from combustion in six Bulgarian TPPs was done. Since coal-derived FAs are applied to many targets, it is imperative to enhance the knowledge for their geochemical composition and environmental impact. The gap of information on PAHs in feed coals and coal-derived FAs has outlined the aim of the study: (i) to compare by geochemical proxy PAHs in feed coals and FAs generated in six Bulgarian TPPs; (ii) to track the changes in PAHs compositions with feed coal ranks and in different ESP rows; and (iii) to estimate the potential toxicity of FAs (if any). Extractable organic matter (EOM) was prepared. PAHs were isolated in aromatic fractions and quantified in μg/kg. The total PAHs for lignite feed coal are in the range 400–530 μg/kg and for FAs 0.30–12.60 μg/kg: for subbituminous feed coal, they are 4000 μg/kg, and for FAs, 1.10–32.50 μg/kg. For bituminous feed coals, they are - 860 μg/kg and 9305 μg/kg, and for FAs from both TPPs, they are several times lower, from 69.4 μg/kg to 103.3 μg/kg, for the five ESP rows of Varna TPP and from 100.4 to 182.20 μg/kg, for the three rows of ESPs of Russe TPP. The EOM for low rank feed coals is strongly dominated by coal biomarkers, i.e., perylene and phenyl substituted PAHs. Therefore, calculations and ratios based on PAHs compositions are done only for bituminous feed coals and their FAs. Combustion has resulted in a regular shift to lighter PAHs compared to the signature PAHs of feed coals. PAHs distributions in FAs are dominated by phenanthrene. Distribution profiles according to the number of aromatic cycles (R) in PAHs are dominated by three-ring (3R) PAHs > four-ring (4R) PAHs. Only in the last row of ESP from the Varna TPP is there evidence for the presence of heavier PAH, five-ring (5R) benzo[g,h,i]fluoranthene, trapped by the finest particulate matter. Relatively low PAHs concentrations determined for FAs are compared with the values for PAHs in soils according to the Bulgarian regulation.

Metal-Containing Nanoparticles in Low-Rank Coal-Derived Fly Ash from China: Characterization and Implications toward Human Lung Toxicity.

Characterization of nanoparticles (NPs) in coal fly ashes (CFAs) is critical for better understanding the potential health-related risks resulting from coal combustion. Based on single-particle (SP)-inductively coupled plasma mass spectrometry (ICP-MS) coupled with transmission electron microscopy techniques, this study is the first to determine the concentrations and sizes of metal-containing NPs in low-rank coal-derived fly ashes. Despite only comprising a minor component of the studied CFAs by mass, NPs were the dominant fraction by particle number. Fe- and Ti-containing NPs were identified as the dominant NPs with their particle number concentration ranging from 2.5 × 107 to 2.5 × 108 particles/mg. In addition, the differences of Fe-/Ti-containing NPs in various CFAs were regulated by the coalification degree of feed coals and combustion conditions of all of the low-rank CFAs tested. In the cases where these NPs in CFAs become airborne and are inhaled, they can be taken up in pulmonary interstitial fluids. This study shows that in Gamble's solution (a lung fluid simulant), 51-87% of Fe and 63-89% of Ti (ratio of the mass of Fe-/Ti-containing NPs to the total mass of Fe/Ti) exist in the NP form and remain suspended in pulmonary fluid simulants. These NPs are bioavailable and may induce lung tissue damage.

Examining the effect of simulation parameters on coal gasification in tapered fluidized bed reactor

The aim of this study is to assess the influence of oxygen-to-steam ratio, wall boundary conditions, coal feeding rate, and static bed height on the concentrations, heating values, and efficiencies of the product gas in a tapered fluidized bed reactor. Results show that lower and higher heating values slightly vary with increasing the oxygen-to-steam ratio in the range of 0.25–0.35. It is found that cold gas efficiency and carbon conversion efficiency goes up with increased ratio of oxygen to steam; however, both efficiencies decline as a result of increasing the coal feeding rate. As static bed height rises, lower and higher heating values diminish for tapered angle of 5°. For tapered angle of 5°, slight changes in concentrations of the product gas are observed with the increased coal feeding rate while the gas concentrations remarkably vary for the tapered angle of 9°.

The Core Control Strategy Adapted to Different AGC Control Modes for Ultra-supercritical Once-through Furnace Unit Burning Lignite

As for the once-through unit using lignite, in order to meet the AGC requirements of load change, the coordinated control strategy of unit was optimized. The control strategy was optimized mainly from the aspects of steam temperature control and steam pressure control. In order to control the mid-temperature stability, strategy of using feed water and coal to correct the mid-temperature at the same time was adopted, and the feed water flow was revised by desuperheating water. Different measures including variable parameter control of turbine, rapid coal adding to improve the main steam pressure, and feed-forward adjustment of primary air pressure were taken to improve the delay of main steam pressure, and also shortens the starting time of pressure when changing load. When the unit was put into AGC control, according to the different load changing characteristics of the two modes of BLO and BLR, the variable parameters of the coordinated feedforward of each subsystem were modified. And it is necessary to dynamically adjust the correction factor according to the load fluctuation, in order to reduce disturbance of important parameters such as furnace pressure, main steam pressure, main steam temperature, etc. The application results of the control strategy in the power plant show that the optimized control logic can meet the load regulation requirements of different AGC modes for the lignite burning unit, and the steam temperature and steam pressure control effect is good in the process.

The use of active coal feed supplement in the young fish feeding

The use of active coal feed supplement in the young fish feeding

Soil and ambient air mercury as an indicator of coal-fired power plant emissions: a case study in North China.

Coal-fired power plants (CFPPs) are an important anthropogenic mercury (Hg) source in China, and it is crucial to understand the environmental impacts of this detrimental element emitted from this source. In the present study, field experiments were conducted for measuring Hg in ambient atmosphere and upland agricultural soils within a radius of 10 km surrounding a large scale coal-fired power plant (1550 MW) in Tangshan, Hebei province. Short-term (20 min) average of gaseous elemental mercury (GEM or Hg0) in ambient air varying from 1.5 to 9.0 ng/m3 and total Hg (THg) in surface agricultural soil (0-20 cm) varying from 9.2 to 43.5 μg/kg at different sites were observed. THg in two soil cores decreased with depth, with concentrations being 2-2.5 times higher in the surface layer than that in the deep layer (50-60 cm), indicating the possibility of the atmospheric input of Hg. Based on the information of the total atmospheric Hg emission since this CFPP's operation in 1970s and the increased THg in nearby soils, it was estimated that about 3.9% discharged Hg has accumulated in the nearby agricultural soils. The low retention rate of the total emitted Hg by soils is a result of high proportion of Hg0 (79.5%) in stack gas emission and potential loss of Hg from soil surface reemission. The positive shifting (~ 0.5‰) of Hg isotopic signature (δ202Hg) from deep soil to surface soil reflected Hg deposition from nearby CFPP emissions that are featured with much heavier Hg isotopic signatures inherited from feed coal (δ202Hg: -0.50‰) and different combustion products (δ202Hg: -0.95 to 3.71‰) compared with that in deep soil layer (δ202Hg: ca -1.50‰). Overall, this study demonstrated that this CFPP has a slight but distinguishable effect on the elevation of ambient GEM and agricultural soil THg in the local environment.

Mercury in desulfurization gypsum and its dependence on coal properties in coal-fired power plants

To disclose possible influencing factors on mercury (Hg) contents in flue gas desulfurization (FGD) gypsum of coal-fired power plants (CFPPs), 11 major CFPPs in Guizhou province of southwest China were surveyed for analyzing Hg contents in feed coal, limestone and gypsum as well as coal properties. It was found that Hg contents in the desulfurization gypsum of the 11 CFPPs varied greatly from 160 to 1482 μg kg−1, with an average of 595 ± 353 μg kg−1. The majority of Hg in gypsum was introduced from the flue gas downstream of the particulate matter control devices, while a much lesser portion (average 3.43 ± 3.85%) was stemmed from limestone. Hg content in gypsum has a strong positive correlation with chlorine content, a weak positive correlation with Hg content and a weak negative correlation with sulfur content in feed coal. Multiple regression analysis results showed that Hg and Cl contents in feed coal were the major determinants of Hg content in flue gas FGD gypsum despite the proportioning of Hg went in wet FGD system was not been evaluated. Results from the present study suggested that coal characteristics are important factors affecting Hg contents in gypsum.

A study of gasification behavior of residues from mild coal hydro-liquefaction

Coal hydro-liquefaction is important means for producing liquid fuel thus ensuring energy security for countries lacking crude oil reserves such as China. Liquefaction residues account for one third of feeding coal and its utilization is crucial for reducing the cost of hydro-liquefaction. Residues can be gasified to produce H2 thus eliminate the hazardous solid waste. Liquefaction residues are complex mixture of unreacted coal, heavy components, inherent mineral matters in coal and used catalysts. This work investigated the structural features and gasification reactivity of the sub-fractions of residues (Res) including preasphaltene and asphaltene (PAA), deashed residues (DeR), and raw coals were also used for comparison. The results showed that the enriched minerals in the residues significantly accelerated gasification while the compact and condensed aromatic structures remarkably inhibited the reaction. The gasification rate decreased in the order Coal ≥ Res ≫ DeR > PAA during isothermal CO2 gasification. Kinetic analysis of gasification was performed with the uniform reaction (UR) and unreacted shrinking core (USC) model, and the kinetic parameters (Eα and A) obtained with the two models were well correlated. Comparatively, USC model was superior to UR model in describing the gasification behaviors of both the coals and the sub-fraction of the residues. These results are potentially helpful for optimizing gasification conditions and realizing clean and efficient utilization of the residues.

Operating characteristics and ultra-low NOx emission of 75 t/h coal slime circulating fluidized bed boiler with post-combustion technology

Coal slime was a kind of industrial solid waste and it was hard to utilize. To realize the resource utilization of coal slime, a 75 t/h circulating fluidized bed (CFB) boiler with post-combustion technology was built. The operating and emission characteristics during mono-combustion of coal slime were investigated in detail. The fuel characteristics of coal slime and feeding from the top of the furnace resulted in the temperatures at the top and the bottom were higher than the middle of the furnace. When the furnace differential pressure increased, the furnace temperature and the main steam temperature both decreased, but the main steam flow increased. The main steam temperature could significantly increase after the soot blowing. The post-combustion air (PCA) was an effective means to adjust the main steam parameters. The main steam temperature increased as PCA increasing. The average SO2 emissions were only 8.4 mg·m−3 benefited from the excellent desulfurization effect of the combination of dry and semi-dry desulfurization. Nevertheless, due to the fluctuations of coal slime characteristics, the standard deviation of SO2 emission reached 8.6 mg·m−3. Under the conditions without desulphurization and SNCR, the NOx emissions of coal slime could be decreased to 38 mg·m−3 and reach the ultra-low NOx emission when post-combustion technology was used.

The transformation and enrichment of Cd in fine particulate matter during coal combustion: The key roles of Ti-bearing components

Fine particulate matter (PM) emitted from coal-fired power plants (CFPPs) has aroused widespread environmental and human health concerns. Cadmium (Cd), as one of the prime toxic air pollutants, which exists in fine PM intensifies its toxicity. In this research, three particle sizes of PM (PM1, PM2.5, and PM10) at the outlet of electrostatic precipitator (ESP), along with feed coal, bottom ash, and ESP ash, were collected from a 300-MW pulverized CFPP. Results showed that Cd was more enriched in the fly ash than in bottom ash. With the PM diameter decreasing, the relative enrichment index (REI) value of Cd increases from 2.30 to 7.84. The concentration of Cd was found to be intimately related to Ti in the PM. Abundant Ti-rich particles were identified in the PM1, having quite different chemical compositions as compared to particles larger than 2.5 μm. The major processes governing the formation of Ti-rich particles included melting of silicate-bound Ti and heterogeneous condensation of gaseous Ti from the decomposition of organic-associated Ti in coal. The transformation behavior of Cd to PM in a coal combustion process was discussed based on its occurrence mode in coal, thermodynamic property, and the possible interactions with ash particle compositions. The retention of Cd (g) by Ti-rich particle were probably dominated by chemisorption at high temperature; at lower temperature, physical adsorption or condensation may be the primary mechanisms for capturing CdCl2 (g).

A simulation-based parametric study of CLOU chemical looping reactor performance

Chemical looping with oxygen uncoupling (CLOU) is a variant on chemical looping combustion in which the oxygen carrier releases gaseous O2 in the fuel reactor, making it well-suited for solid fuels, since the released gaseous O2 readily reacts with solid char. This study presents several computational fluid dynamic (CFD) simulations of copper-based CLOU in a dual fluidized bed system, each with different operating conditions. The modeling predicted that coal particle sizes as large as 1000 μm did not significantly affect performance. Increased oxygen carrier copper loading resulted in an excess of gaseous oxygen in the product gas stream. Decreasing the oxygen carrier bed mass as well as reducing the air reactor fluidizing velocity did not supply enough oxygen to the fuel reactor to complete combustion of the coal. This generated a failure state in which the temperature continued to decrease in the fuel reactor from the lack of combustion, which in turn reduced the O2 equilibrium partial pressure, further lowering the amount of combustion possible. Sufficient O2 can be maintained in the fuel reactor by ensuring a high enough air reactor velocity and a large enough supply of oxygen carrier inventory to handle the chosen coal feed rate.

Thermal and electrochemical impact of kaolin on a direct carbon fuel cell

This paper investigates the impact of kaolin, a dominant coal mineral, on the thermal and electrochemical behaviour of the molten ternary carbonate eutectic ((Li,Na,K)2CO3) in the direct carbon fuel cell (DCFC) as a means to simulate long-term operation with a continuous coal feed. Thermogravimetric and differential thermal analysis, coupled with kinetic modelling using the Friedman method, shows a substantial decrease in activation energy for eutectic melting with the addition of kaolin. Electro-oxidation of carbon (graphite) is also enhanced with kaolin in the electrolyte, increasing from 17.68 mA/cm2 at 0 wt% kaolin to the highest value of 162 mA/cm2 with 15 wt% kaolin added. It is shown that the improvement is due to increasing oxide concentration resulting from kaolin dissolution in the electrolyte.

A comprehensive understanding of the non-uniform characteristics and regulation mechanism of six external loops in a 600 MW supercritical CFB boiler

As the carrier of material circulation, the uniformity of multi-parallel external loops directly affects the operation of large-scale circulating fluidized bed (CFB) boilers. Some non-uniform phenomena have been found, but the non-uniform characteristics and the absorptive capacity in full process of external loops under changeable operating parameters were seldom considered. To solve this, comprehensive cold/thermal field tests were conducted on the external loops of the first 600 MW supercritical CFB boiler. Operating characteristics of the loops and the fluidization uniformity of fluidized bed heat exchangers (FBHEs) under various cases were fully demonstrated. The influence of air-coal distribution on the operating non-uniformity of the external loops were analyzed, and the absorptive capacity to thermal deviations were quantified. The regulation mechanisms of cyclones and FBHEs were clarified, and the key reason of thermal deviations in FBHEs was also figured out. Eventually, a new coal feeding method to maintain heat balance in dense phase zone was proposed. The results of this paper fully reflected the operating characteristic of the full process in external loops and the response characteristics to air-coal adjustments, which could provide the most direct guidance for academic research as well as optimal design and operation of large-scale CFB boilers.

Reducing unplanned downtime using Predictive Maintenance (PdM)

Maintenance is one of the essential aspects that contribute to keep production process continue to operate and reduce unplanned downtime. In the cement industry, especially kiln area, unplanned downtime can cause not only low availability but also high maintenance costs due to unplanned demand for spare parts and the need for labour to complete unplanned downtime, hence the right method of maintenance is needed. One of the strategic maintenances could be applied is Predictive Maintenance (PdM). Among others maintenance strategy, PdM provides more accurate task due to real time condition monitoring of equipment based on sensors obtained from server data. In this paper, Mahalanobis-Taguchi System (MTS) is applied to provide reliable multisensory analysis and real-time decision making. MTS includes 1) fuses data from multiple sensors into a single system level performance metric; 2) extends MTS by providing a single tool for fault detection/diagnostic, isolation, and prognostic; and 3) offers a systematic way to determine the key parameters following with fault reducing analysis. Multi-sensor data in the kiln used in this research are speed motor main drive, Pfister Coal feed, kiln feed, speed motor IDFAN1, speed motor IDFAN2, speed motor EPFAN. Based on the MTS calculation, the normal data values are obtained from each sensor data. This method is also used to detect, identify, and classify failures based on tests from scheme data. The proposed diagnostic and prognostics scheme from this paper are useful for guiding the company to predict the failure as well as the maintenance schedule then it will increasing the availability from 80% to 90% by reduce the unplanned downtime.

Distribution and Mode of Occurrence of Co, Ni, Cu, Zn, As, Ag, Cd, Sb, Pb in the Feed Coal, Fly Ash, Slag, in the Topsoil and in the Roots of Trees and Undergrowth Downwind of Three Power Stations in Poland

It is supposed that the determination of the content and the mode of occurrence of ecotoxic elements (EE) in feed coal play the most significant role in forecasting distribution of EE in the soil and plants in the vicinity of power stations. Hence, the aim of the work was to analyze the properties of the feed coal, the combustion residues, and the topsoil which are reached by EE together with dust from power stations. The mineral and organic phases, which are the main hosts of EE, were identified by microscopy, X-ray powder diffraction, inductively coupled plasma atomic emission spectrometry, and scanning electron microscope with an energy dispersive X-ray methods. The highest content of elements was observed in the Oi and Oe subhorizons of the topsoil. Their hosts are various types of microspheres and char, emitted by power stations. In the areas of long-term industrial activity, there are also sharp-edged grains of magnetite emitted in the past by zinc, lead, and ironworks. The enrichment of the topsoil with these elements resulted in the increase in the content of EE, by between 0.2 times for Co; and 41.0 times for Cd in the roots of Scots pine, common oak and undergrowth, especially in the rhizodermis and the primary cortex and, more seldom, in the axle roller and cortex cells.