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Biomass serves as an alternative energy solution for decarbonizing coal-fired power plants, which have been reactivated in several countries due to the global energy crisis. Oil palm waste, owing to its abundant availability, holds significant potential as a biomass fuel. This study aimed to investigate the combustion performance of various oil palm wastes in comparison to coal. Biomass combustion is associated with ash-related problems such as slagging, fouling, and corrosion, which may accelerate ash deposit acceleration, reduce heat transfer, and damage refractory equipment in boilers. Ash-related problems were evaluated using the method commonly adopted for solid fuel, including experimental drop tube furnace combustion and ash observation. The results indicate that each oil palm waste has different combustion characteristics. Palm leaves, empty fruit bunch, and palm fronds with clean probe observation have a relatively low tendency of slagging and fouling and can be recommended as biomass fuel for co-firing. However, their high alkali and iron contents need to be considered. Palm fiber has similar combustion characteristics to coal, but it has a high slagging and fouling tendencies. The palm stems with high chlorine content have a high corrosion tendency confirmed by probe observation, scanning electron microscopy, and X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

Russia is one of the world leaders in the production of sunflower oil, and the utilization of sunflower husks seems to be a very pressing problem. The husk has low humidity (4.4‒12.2%) and a fairly high calorific value (16–19 MJ/kg), but its ash contains a significant amount of potassium, calcium, and magnesium compounds, which cause slagging of the boiler furnace and rapid growth of ash deposits on its convective heating surfaces. Agglomeration and slagging are especially acute when burning crop waste in a fluidized bed of quartz sand, causing defluidization of the layer. This leads to frequent boiler shutdowns to clean the furnaces. Alternative materials to quartz sand are known, but the literature contains little data on their commercial application. The operation of a combustion device with a fluidized bed of quartz sand and olivine as part of a 2-MW heat-generating installation when burning sunflower husks is analyzed. The chemical composition of agglomerates is studied and the mechanism of their formation is described. The experiment on burning husks in a layer of olivine lasted continuously for 600 h. When carrying out periodic measurements of the fractional composition of the olivine layer, the concentrations of carbon oxide, dioxide, and oxygen in the flue gases and the formation of agglomerates was not detected. [ABSTRACT FROM AUTHOR]

The computational studies carried out previously taking as an example the BKZ-210-140 boiler installed at Tomsk-2 state-owned district power plant (SDPP) have shown that, given the existing scatter in the characteristics of coals fired at the power plant, the temperature of gases at the boiler furnace outlet may vary in a wide range (more than 100°С). Such variability of the operational parameters entails a number of problems, including difficulties with keeping a stable superheated steam temperature, increased risk of heating surfaces becoming slagged, and less efficient fuel combustion. A conclusion has been drawn based on the obtained computation results that the possibility of adjusting the flame's initial section vector by ±15° will make it possible to solve the above-mentioned problems to a significant extent. A tiltable burner is the key component of the combustion system with adjusting the flame position. Based on an analysis of the current operation conditions of the Tomsk-2 SDPP BKZ-210-140 boiler, technical solutions were developed on the design of a tiltable vortex burner intended for combusting pulverized coal as well as natural gas and fuel oil. The burner's outlet part is made so that it is possible to tilt it by ±15° in the vertical plane and by ±5° in the horizontal plane, which will make it possible to adjust the combustion mode in an efficient manner. The furnace process is simulated in the ANSYS Fluent software package under different boiler operation conditions. The simulation results show that, in the case of using the new burners, it is possible to improve the furnace process efficiency. By tilting the burner by ±15° in the vertical plane, it becomes possible to obtain the temperature adjustment range at the furnace outlet equal to 120°С. Based on the adopted technical solutions, design documentation for the burner has been developed. An experimental sample of the low-toxic tiltable vortex burner installed in the Tomsk-2 SDPP BKZ-210-140 boiler has been manufactured. [ABSTRACT FROM AUTHOR]

The effect of adding coal gangue (CG) under different ratios, temperatures and atmospheres on the slagging of wheat straw (WS) combustion was studied in a tubular furnace. At 800°C, there was obvious agglomeration and melting on the ash surface, caused by the reaction of alkali metal elements and alkali earth metal elements with SiO2 to form low melting point silicate substance, resulted in serious slagging. After adding CG, Al2O3 in CG reacted with SiO2 to form high melting point silicate minerals, which reduced the tendency of biomass slagging. According to the slagging discriminant results of empirical index, sample with 20% CG added combustion in air atmosphere has the lowest slagging tendency. The FactSage results showed that after adding CG, in the whole temperature range, there was no significant difference between the O2/CO2 atmosphere and the air atmosphere, but the phase contents were different. [ABSTRACT FROM AUTHOR]

Phosphorus-based additives are recognized as an effective strategy for alleviating slagging during Zhundong coal combustion. However, their efficacy to mitigate fouling issues caused by the substantial sodium release is constrained. In this work, ball-milled ash was combined with ammonium dihydrogen Phosphate (NH4H2PO4) to jointly address the challenges of fouling and slagging. The sodium release behavior, ash fusion temperatures (AFTs), and combustion characteristics were comprehensively investigated by using simultaneous thermal analyzer and other characterizing methods. The findings show that ball-milled ash, owing to its high reactivity, substantially enhanced the sodium retention percentage. The sodium retention mechanism of ball-milled ash is mainly attributed to solid–solid reactions, whereas NH4H2PO4 primarily serves to increase AFTs through gas–gas and gas–solid reactions. The highly reactive components within ball-milled ash also facilitate the reactions with NH4H2PO4 to form high melting-point phosphorus-based minerals. In terms of combustion characteristics, the inclusion of ball-milled ash leads to a noteworthy reduction in the burnout temperature, while the addition of NH4H2PO4 contributes to a moderate increase in the burnout index. Taking into account the three aspects of sodium release, AFTs, and combustion characteristics, the optimal combination strategy is the mass addition ratio of 0.05 for ball-milled ash and the PO43−/Na molar ratio of 1.0 for NH4H2PO4. [ABSTRACT FROM AUTHOR]

The process of gasification of biomasses of plant origin containing the additives of sulfur oil shale was studied. It was shown that the presence of sulfur oil shale in the mixtures decreased and, in some cases (at a high sulfur content of oil shale), prevented the appearance of deposits (slagging) on the equipment walls. It was established that a maximum effect was achieved with the addition of 5% oil shale containing at least 16% sulfur. [ABSTRACT FROM AUTHOR]

Intense mechanical pretreatment of coal is among promising technologies in thermal engineering owing to its ability to achieve essentially higher coal reactivity. In being subjected to such treatment, the coal's mineral part becomes significantly transformed, and a change occurs in the gas and ash flows during combustion, which may result in either lower or higher fouling of the boiler's heating surface. Till now, there have been no activities in the world practices on studying the effect that the "mechanical activation" of coals has on the deposit formation intensity. For coals characterized by different degrees of metamorphism, specifically, brown coal from the Kansk–Achinsk basin and black coal from the Ekibastuz basin, regularities pertinent to the change in the slagging onset temperature after pulverization in mills having different degrees of energy intensity are established. Results from studying the slagging intensity in burning the dust of brown coals after their having been pulverized in a disintegrating mill are given. The numerical analyses were carried out by applying the universal SigmaFlow CFD software package. The mathematical model used in carrying out the studies comprised the submodels of a reacting turbulent gas flow and models of motion, heat transfer, coal particle combustion, and slag deposit formation. For taking into account the specific features pertinent to the combustion of "mechanically activated" coals, the model was supplemented with the reaction properties, volatile release rates, and coal residue burning rates. The numerical analyses of slagging intensity in burning pulverized brown coals have shown that the slagging onset temperature becomes by 40–60°С higher after having been pulverized in a disintegrator. [ABSTRACT FROM AUTHOR]

In the short- and mid-term perspective, drastic measures for the reduction of anthropogenic emissions including extensive decarbonization of the residential and industrial heating sector have to be implemented. To replace fossil fuels, solid biogenic residues and wastes will have to be increasingly utilized. Compared to clean woody biomass, these biomass assortments are commonly characterized by higher Si and alkaline metal contents recognized as major driver for low ash melting temperatures resulting in elevated risk of bottom ash slagging. To facilitate the prediction of bottom ash slagging during combustion, several fuel indices have been proposed. Based on empirical correlations with parameters relevant for slagging behavior, e.g., ash melting temperatures or slag fraction of the bottom ash, these fuel indices were subsequently enhanced and adapted for an increasing range of biomass fuel characteristics. In this study, analysis data of 26 woody and non-woody fuels and experimental data derived from two combustion test campaigns with an automatically stoked small-scale boiler were investigated through principal component analysis. Thus, the complex interdependencies between the fuel composition and the resulting bottom ash characteristics and the applicability of existing fuel indices were evaluated. The chemometric analysis highlighted that Si, Ca, K, Mg, and also the remaining Al and S in the bottom ash are crucial fuel components in the context of bottom ash melting. On this basis, the molar ratio (Si + P + K)/(Ca + Mg) was adapted and correlated with the susceptibility to slag formation which is a new parameter derived from ash content, slag fraction > 16 mm in the bottom ash, and slag category. Thus, the applicability of a newly developed fuel index was evaluated with respect to the bottom ash slagging risk during real-scale combustion. Three ranges were distinguished for the fuel index corresponding to a specific susceptibility to slag formation (i.e., low < 20 mol/g for woody biomass, elevated between 20 and 75 mol/g, and serious > 75 mol/g for straw-like fuels and blends with wood). The linear regression of the fuel index with susceptibility to slag formation exhibits a high coefficient of determination (i.e., 0.99 for woody biomass and 0.84 for straw-like fuels and their blends with wood). [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the ignition and slagging characteristics for combustion of boron-containing solid propellants with ammonium perchlorate as an oxidizer under conditions modeling the operation of the gas generator and afterburner of a rocket-ramjet engine. It is shown that the introduction of fluorine-containing additives into the propellant reduces the content and adhesion capacity of primary condensed combustion products (slags). The dependences of the ignition delay on the radiant heat flux density in the range 20–180 W/cm2 are obtained for model solid propellants containing boron, carbon, boron carbide, and slag particles collected in the gas generator. [ABSTRACT FROM AUTHOR]

Agricultural plant wastes such as wheat straw, rice hulls, and sunflower-seed husks were characterized experimentally. The chemical composition of the ash formed from these wastes at various temperatures was determined by energy-dispersive X-ray microanalysis, X-ray diffraction analysis, and IR spectroscopy. The chemical composition of mineral components of the agricultural plant waste ash varies, but the prevalent components are CaO, SiO2, and K2O. Thermodynamic calculations show that SiO2 prevails in rice hull ash; K2Si2O5 and Ca3Si2O7, in wheat straw ash; and potassium compounds (K2O, K2SiO3, KCl, K2SO4), in sunflower-seed husk ash. The ash melting temperatures were determined by the method of characteristic temperatures. No clear correlation was revealed between the melting temperature and alkali metal content of the ash. The main parameters of slag formation such as base–acid ratio, slag viscosity index, and fouling coefficient were calculated. Wheat straw ash and sunflower-seed husk ash, in contrast to rice hull ash, tend to slagging and fouling of reactor walls. [ABSTRACT FROM AUTHOR]

In order to mitigate the slagging risks of high-alkali coal (HAC) gasification while optimizing the operating temperatures for practical application, the experimental and calculational works were performed on the horizontal tubular furnace system and the FactSage 7.2 software, respectively. The slagging tendencies of three HACs were anticipated by applying different indexes of ash chemistry characteristics prior to experiments, but the determined results were found inconsistent. The relationship between Na retained ratio (RNa) and the ash fusion temperatures (AFTs) of gasification residues demonstrated that the AFTs of coal with high RNa are low, while AFTs of coal with low RNa are high. Nevertheless, when the residues contained a large number of calcium-containing silicates and aluminosilicates, the ATFs were reduced significantly even if its RNa stayed at a low level. Furthermore, the operating temperatures of the three coals (in order of Mulei coal, Shaerhu coal, and Tietou coal) were suggested to be controlled below 1150°C, 1100°C, and 950°C, respectively. [ABSTRACT FROM AUTHOR]

A commercial CFD package coupled with user-defined functions was used to observe coal particle combustion and tracking, particle capturing and deposition, and other related phenomena. A modified Watt-Fereday model for deposition employing experimental coefficients derived from the ash fusion test was used to predict ash viscosity, which showed that the samples had a nonadditive behavior due to the eutectic phenomenon. The furnace results showed that when the Bayan coal, containing a large amount of volatile matters, was injected at the top burner, the slagging propensity increased compared to when it was injected in the bottom burner. In addition, the specific blending ratio of 25 % Flame and 75 % Bayan coal, which had a lower melting temperature compared to the individual coals. This study suggests that sub-bituminous coal should be injected in the bottom burner, and the specific blending ratio that yields a low-temperature eutectic mixture should be avoided. [ABSTRACT FROM AUTHOR]

Spent biochar obtained after water treatment especially metal adsorption could be used as a solid fuel. In this study, soil application potential and fuel value of cadmium contaminated biochar was investigated. Biochar prepared from Parthenium (PBC) and the thermally modified biochar (MPBC) was artificially contaminated with different concentrations (1, 10, 50, 100 and 200 mg/l) of Cd solution. The contaminated PBC-Cd and MPBC-Cd was applied to a red soil, and their impact on soil biological activity, maize growth and Cd bioaccumulation was assessed. Maize growth was retarded due to the contaminated biochar. Soil and plant Cd concentrations increased significantly. The soil dehydrogenase (DHA) and fluorescein diacetate hydrolases enzyme activities were adversely affected. DHA reduced from 324 to 97 mg TPF/kg/24 h in MPBC-1 to MPBC-200, while in PBC-1 to PBC-200, DHA decreased from 422 to 112 mg TPF/kg/24 h. Cd contaminated biochars obtained after waste water treatment could not be used for soil application. Fuel values of contaminated biochar were analysed by the higher heating value of biochars and their fusibility indices. The high heating value of the biochar is comparable with the lignite. Raw biochar contains significant amount of alkali elements that affected their use as a fuel. However after adsorption, the washing of the biochar alkalies significantly improved the fuel properties, especially the propensity for slagging and fouling. Biochar used for treatment of contaminated waste water could be sustainably used as a solid fuel; however further studies are needed to manage the metal enriched ash generated after combustion of these contaminated biochar. [ABSTRACT FROM AUTHOR]

The model composition of municipal solid waste (MSW) and its ash chemical composition are characterized. Mineral compounds and melting points are studied using a variety of analytical methods, including XRD, FTIR, and AFT. The main parameters of slag formation are calculated: base-to-acid ratio, slag viscosity index, and fouling coefficient. Solid municipal waste ash contains significant amounts of CaO, SiO2 and Al2O3. Using the Terra program, thermodynamic calculations of the chemical equilibria of the CaO–SiO2–Al2O3–Na2O systems containing from 5 to 25% sodium oxide are performed. It is experimentally shown that each 5 wt % increase in the Na2O content reduces the characteristic melting temperatures of MSW ash by 30–50°С. [ABSTRACT FROM AUTHOR]

Mankind's quest to reduce its dependency on fossil fuel involves biomass as a promising alternative. However, direct application of raw biomass faces problems such as high moisture content, low heating value, and poor grindability. Pyrolysis is one of the pre-treatment methods to improve biomass properties particularly its energy density. This study is aimed at investigating the pyrolysis of oil palm trunk (OPT) into biocoal and its suitability for solid fuel applications in terms of slagging and fouling tendencies, bulk density, proximate and ultimate analysis, higher heating value, energy densification ratio, and mass and energy yield. The biocoal was produced using a top-lit, updraft reactor with a peak temperature of 550 °C and fixed air flowrate of 4.63 L/min. The bulk density of OPT biocoal was 87.7 kg/m3 which is 4.63% lower than that of original OPT due to the increased porosity. The elemental composition of our biocoal resembles lignite. The volatile matter content decreased by a factor of 1.87 while the fixed carbon content and higher heating value (HHV) increased from 4.29 to 30.9% and from 14.5 to 19.6 MJ/kg, respectively. The HHV of biocoal increased by a factor of 1.36 relative to that of raw OPT; however, the resulting energy yield was low (37.6 ± 1.9%) due to a low biocoal yield of 27.8 ± 1.4%. The ash content increased by a factor of 1.5, resulting in an ash content of 27.8 wt% for biocoal. This increment may exacerbate the slagging and fouling propensity in furnaces and boilers as indicated by the slagging and bed agglomeration index which increased from 2.0 to 5.2 and from 0.4 to 0.7, respectively. Demineralization, a lower pyrolysis temperature and subsequent briquetting of OPT biocoal are suggested to improve its fuel properties for co-combustion in coal-firing power plants. [ABSTRACT FROM AUTHOR]

Five lignite samples from Russia's Itatsky, Munai, Arkharo-Boguchansky, and Kangalassky fields and the Mongolian Baganuur field are characterized on the basis of technical analysis, their elemental composition, calorific value, petrographic composition, and the properties of their mineral component. Experimental data regarding the chemical composition of their ash residues permit empirical calculation of temperatures characterizing ash fusibility, the temperature of normal liquid slag removal, and the temperature of slagging onset. The melting temperatures are found to rise with increase in content of the acidic oxides SiO2 and Al2O3 in the ash residues but to fall with increase in the concentration of Fe2O3, CaO, and MgO. [ABSTRACT FROM AUTHOR]

fluidized bed combustion boiler, pulverized fuel boiler and waste heat boilers. These boilers are used in different industries such as power plants, paper, and chemical. The present paper reports various problems (such as agglomeration, slagging, fouling, caustic embrittlement, fatigue failure and high temperature corrosion) related to boilers and their possible solutions. Some of the controlling parameters for high temperature corrosion has also been studied viz use of inhibitors, varying temperature and pressure, sol-gel coating and thermal spray coating. Thermal spraying has emerged as a main tool for improvement in surface. Problem of corrosion, wear resistance, electrical or thermal insulation can be altered using different coating techniques and materials. Deposition of ash in biomass-fired boilers also causes severe problems of agglomeration. The problem of agglomeration can be solved using kaolin or NH3 in the bed of boilers. Some important processes such as pulse detonation wave technology, intelligent soot blower, chemical treatment technology can be used to minimize the effects of fouling. [ABSTRACT FROM AUTHOR]

Experience with the burning of coals from the Kansk-Achinsk Basin in a P-49 boiler with different burner and furnace configurations is examined. Problems in running the boiler with liquid slag removal are noted. Some studies of boiler operation with low-temperature vortex coal firing following technical renovation are discussed. [ABSTRACT FROM AUTHOR]

Results of calculations and test firing of non-design 3BR grade coal from the Bol'shesyrskii deposit instead of 2BR Borodino coal in a BKZ-160-1,4-5 boiler with mill-fans are described. The feasibility of using Bol'shesyrskii coal in BKZ-160-1,4-5 boilers for mandatory blast of furnace screens by four water cleaning systems is demonstrated. [ABSTRACT FROM AUTHOR]

On the understanding that the characteristics of the gas flow have a major contribution to slagging, a change in the fineness of pulverized coal necessitates taking into account the change in the properties of fly ash, which can either improve or worsen the slagging situation. A decrease in the pulverized coal particle size leads to a reduction of the fly ash particle size, an intensification of the formation of friable deposits, and an increase in the degree of conversion of pyrite to solid iron oxides. This reduces or prevents the formation of strong primary deposits and critical slagging situations. The smaller the dust particles, ceteris paribus, the lower the slagging rate. Unlike coarser pulverized coal, the strength of deposits increases due to sintering and decreases due to sulphatization. [ABSTRACT FROM AUTHOR]

The article reports the results of investigation into the possibility of using off-design coals as an additional fuel in connection with predicted reduction in the heat of combustion of shale oil and more stringent environmental regulations on harmful emissions. For this purpose, a mathematical model of a TP-101 boiler at the Estonian Power Plant has been constructed and verified; the model describes the boiler's current state. On the basis of the process flow chart, the experience of operating the boiler, the relevant regulations, and the environmental requirement criteria for evaluation of the equipment operation in terms of reliability, efficiency, and environmental safety have been developed. These criteria underlie the analysis of the calculated operating parameters of the boiler and the boiler plant as a whole upon combustion with various shale-oil-to-coal ratios. The computational study shows that, at the minimal load, the normal operation of the boiler is ensured almost within the entire range of the parts by the heat rate of coal. With the decreasing load on the boiler, the normal equipment operation region narrows. The basic limitation factors are the temperature of the steam in the superheater, the temperature of the combustion products at the furnace outlet and the flow rate of the combustion air and flue gases. As a result, the parts by heat rate of lignite and bituminous coal have been determined that ensure reliable and efficient operation of the equipment. The efficiency of the boiler with the recommended lignite-to-coal ratio is higher than that achieved when burning the design shale oil. Based on the evaluation of the environmental performance of the boiler, the necessary additional measures to reduce emissions of harmful substances into the atmosphere have been determined. [ABSTRACT FROM AUTHOR]

In a conventional coal-fired boiler combustion of coal causes buildup of soot, ash, and slag in the heat transfer surfaces, which reduces the heat transfer as well as operating efficiency. To achieve a high operating efficiency and improving heat transfer in boiler pressure parts, sootblowing is an important phenomenon in boiler operation. Boiler operators are typically provided with little or no information about the fouling status of heating surfaces or with much guidance regarding how to optimize sootblowing operations even if there are some indications like metal temperature, sprays. This raises the requirement of sootblowing optimization strategy to determine which portions of the boiler to clean and on what schedule. The objective of this study is to develop a sootblowing optimization system that uses thermodynamic model and artificial neural networks model to predict the effectiveness of heating surfaces. In addition, the system utilizes an optimization algorithm to refine the search for the optimal sequence of sootblower frequency and achieve boiler performance targets. [ABSTRACT FROM AUTHOR]

Furnace chambers are currently designed with extensive use of methods employing computer programs for three-dimensional dynamics that take into account a large number of influencing factors in the form of physically based quantities without the computational model being dependent on features of the geometry and operating mode of the furnace. The results of heat transfer calculations, however, are highly dependent on a priori specification of the level of loose (not sintered) deposits and slagging of the furnace. This has made it necessary to develop and test models of slagging and empirical methods for predicting the thermal resistance of deposits based on extensive studies in Russia. For practical purposes it is also necessary to improve zonal methods using physical principles for heat transfer calculations. [ABSTRACT FROM AUTHOR]

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The initial slagging temperature represents a combination of various properties of fly ash, does not give a priori preference to any of them, and objectively characterizes the bonding of particles in deposits. Unlike other countries, in our country, this temperature is widely used as a main coal slagging index. This temperature measured in different experimental conditions for the same coal may differ from the temperature measured in identical conditions for different coals. The first part of this review addresses methods for determining the initial slagging temperature and the use of this index during the design and operation of coal-fired boilers. [ABSTRACT FROM AUTHOR]

A new pneumoimpulsive technology, central to which is an impact effect of air jet on ash deposits, was proposed for carrying out continuous preventive cleaning of the platens installed in the steam superheater primary and secondary paths of the PK-38 boiler at the Nazarovo district power station. The pneumoimpulsive cleaning system was mounted in the PK-38 boiler unit no. 6A, and the cleaning system tests were carried out during field operation of the boiler. Owing to the use of the proposed cleaning system, long-term (for no less than 3 months of observations) slag-free operation of the platen surfaces was achieved in the range of steam loads from 215 to 235 t/h with the average load equal to 225 t/h at furnace gas temperatures upstream of the platens equal to 1220-1250°C. [ABSTRACT FROM AUTHOR]

In Part 1 of the present investigation, 37 representative Eocene coal samples of Meghalaya, India were analyzed and their physico-chemical characteristics and the major oxides and minerals present in ash samples were studied for assessing the genesis of these coals. Various statistical tools were also applied to study their genesis. The datasets from Part 1 used in this investigation (Part 2) show the contribution of major oxides towards ash fusion temperatures (AFTs). The regression analysis of high temperature ash (HTA) composition and initial deformation temperature (IDT) show a definite increasing or decreasing trend, which has been used to determine the predictive indices for slagging, fouling, and abrasion propensities during combustion practices. The increase or decrease of IDT is influenced by the increase of FeO, AlO, SiO, and CaO, respectively. Detrital-authigenic index (DAI) calculated from the ash composition and its relation with AFT indicates Sialoferric nature of these coals. The correlation analysis, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) were used to study the possible fouling, slagging, and abrasion potentials in boilers during the coal combustion processes. A positive relationship between slagging and heating values of the coal has been found in this study. [ABSTRACT FROM AUTHOR]

One of the ways to mitigate fouling and slagging in downstream sections of boilers, power plants, and gas turbines employing coal combustion is to coat the boiler tubes with low surface energy materials. Such a coating not only reduces the surface energy but can potentially offer a rough surface as well. Hence, the simultaneous effects of surface energy and roughness on fly ash deposition need to be understood. Slag-layer deposition involves drop dynamics associated with arrival of molten ash droplets. While recoiling after reaching maximum spread diameter, the drop may bounce or stick depending on the retraction energy. Bouncing potential of the recoiling droplet decides its fate-to stick or to bounce. In order to quantify the bouncing potential, the spread ratio-maximum spread diameter to initial drop diameter-needs to be evaluated. In this study, models are presented to calculate the spread ratio and bouncing potential of impacting drops on rough surfaces; these incorporate the phenomenon of air/gas pockets present beneath the spreading and recoiling splat. The velocity profiles of the spreading droplet, derived by solving axisymmetric creeping flow, are employed to theoretically estimate the dissipation energy while spreading. The predictions of the proposed spread ratio model-free from fitting parameters-are compared with experimental data in literature and are shown to be within ±5 % of the reported values. With the capability to predict whether the droplet bounces or sticks, the bouncing potential model is exploited to suggest choices of roughness and surface energy to mitigate slagging deposits. [ABSTRACT FROM AUTHOR]

Mathematical models of slagging which can provide successful predictions for specific cases are not reliable for arbitrary fuels and boilers. This is because of insufficient experimental data and the complexity of the many processes and properties involved in slagging, but also because of conceptual shortcomings of these models. Here we examine some important questions, including the destruction of deposits during their formation, the dependence of the computational scheme of a model on the type of primary deposits, and the variability of the viscosity at which particles begin to adhere. [ABSTRACT FROM AUTHOR]

Scientific and technical problems concerned with retrofitting the TP-87 boiler installed at the Novokemerovo cogeneration station and operating on Grade 2SS Kuznetsk coal and the BKZ-320 boiler installed at the Novosibirsk TETs-3 cogeneration station and operating on Berezovo coal from the Kansk-Achinsk coal field for vortex combustion technology are addressed. A conclusion is drawn that low-cost retrofitting of obsolete boilers at thermal power stations with retaining the existing boiler unit infrastructure is presently the most reasonable strategy of their further use. [ABSTRACT FROM AUTHOR]

An instrumented study of furnace process in BKZ-160 boilers at the Sogrinskaya heating and electric power plant is used to examine boiler slagging and capacity limitations. The causes of slagging are established: burning of low-ash coals, excessively fine coal dust, high air inflow into the furnace and gas ducts with corresponding low excess air in the burner feeds, nonoptimal flue gas dynamics owing to a nonuniform distribution of secondary air between the burners, etc. These results confirm that, with other conditions the same, tangentially-fired furnaces are subject to more slagging, often at emergency levels, than the other standard combustion configurations. [ABSTRACT FROM AUTHOR]

Research on the slagging properties of coals and slagging in boilers continues to be of current interest, despite many years of experience and considerable progress. This is because of changes in the fuel balance and the development and introduction of new technologies. These include changes in the design of pulverized coal fired boilers to reduce atmospheric pollution, higher steam temperatures, combustion in oxygen, and thermal preparation of coal. Reducing slagging requires boiler designs consistent with the properties of coal, the ability to vary the conditions under which slagging occurs, improved monitoring, control, and cleaning methods. [ABSTRACT FROM AUTHOR]

New technological schemes for low-temperature swirl combustion of different kinds of fuel in semienclosed furnaces are developed and successfully tested in an operating plant. Data on swirl combustion of bituminous coals, peat, and natural gas in a BKZ-210-13.8 boiler are presented. [ABSTRACT FROM AUTHOR]

The period of commissioning of P-61 boilers at stations Nos. 1 and 2 of the Berezovsk state regional thermal power plant (BGRÉS-1) and measures for improving the operation of boiler components in order to prolong steady performance of 800-MW power generating units in the load range of 650 – 700 MW are considered. Suggestions of the personnel of BGRÉS-1 and ZiOSib on modification of the P-67 boiler of unit 3 are presented including reshaping of the platens above the furnace, replacement of the convection superheater by double-stage L-shape platens, corridor arrangement of the loops of the convection superheater, and 30% widening of the surface of the economizer. Planned renovations of the P-67 boiler of units 1 and 2 are discussed. [ABSTRACT FROM AUTHOR]

The ash behaviour comprises one major obstacle towards the efficient utilization of municipal solid wastes, (MSW), in incineration plants. The presence of large amounts of inorganic constituents such as alkali and alkali earth metals, chlorine, sulfur and zinc increase significantly the ash reactivity and lead to severe ash-related problems such as fouling, slagging, corrosion and erosion during their thermal treatment. In this paper, the melting behaviour of various ash fractions originating from the incineration of MSW is studied using simultaneous, (DSC/TG), thermal analysis methods. The produced results provide the basis for improved modelling of the ash behaviour during the incineration of MSW. [ABSTRACT FROM AUTHOR]