Search

During the combustion of solid fuels in power generation systems, one of the biggest problems related to ash is the surface deposition and accumulation of molten or sintered slag, commonly known as slagging. This research evaluated the influence of coal quality on the tendency for slagging based on the evaluation of practical criteria for industry, such as traditional indices, ash load, and coal granulometry. The indices were evaluated from standardized analyses of the composition and fusibility temperatures of the ash of eight bituminous coals. Ash fusibility tests were performed in both oxidizing and reducing atmospheres. Under oxidizing conditions, iron had a dominant influence on the formation characteristics of slagging, resulting in higher melting temperatures. Coals with low frequencies of hard deposit formation, as determined by their ash composition, contributed significantly to deposition problems due to their high ash load and granulometry. Furthermore, large coal particles require more time to burn, which can lead to caking or slag and increased carbon loss in ash. Therefore, when using empirical indices to assess the tendency for slagging, it is essential to consider ash content and ensure an appropriate distribution of coal sizes for combustion. [ABSTRACT FROM AUTHOR]

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]

Co-combustion in pulverized coal boilers is one of the best methods to achieve harmlessness, reduction and resource disposal for carbon-containing solid wastes. This work aims to study the effect of dried dust (DD) generated from CaC2 production on the combustion and slagging characteristics of Zhundong (ZD) coal blend. The combustion of ZD coal blend with different ratios (0%, 2.5%, 5.0%, 7.5%) of DD was conducted in a thermal gravimetric analyzer under air atmosphere. The ash fusion temperature tests and slagging experiments were carried out to understand the effect of the addition of DD on the slagging behavior of ZD coal blend. The results showed that the ignition and burnout temperatures of ZD coal showed different varying tendency with the blending ratio of DD increasing. Increasing the adding ratio of DD could raise the ash fusion temperatures of ZD coal blend. The addition of 5% DD promotes the formation of gypsum in deposited slags, and it also alters the chemical components of fine particles adhered onto the surface of molten particles. Meanwhile, in comparison with raw ZD coal blend, more Ca would combine into silicates in sampled slags. After the overall evaluation, a low blending proportion of DD (<5%) is suggested for pulverized boilers. [ABSTRACT FROM AUTHOR]

The study aimed to explore the effects of biomass co-firing of coal using acacia wood bark at circulating fluidized bed (CFB) boiler coal-fired power plant with 110 MWe capacity. The analysis focused on main equipment parameters, including the potential for slagging, fouling, corrosion, agglomeration, fuel cost, and specific environmental factors. Initially, coal and acacia wood bark fuel were blended at a 3% mass ratio, with calorific values of 8.59 MJ/kg and 16.59 MJ/kg, respectively. The corrosion due to chlorine and slagging potential when using wood bark was grouped into the minor and medium categories. The results showed that co-firing at approximately 3% mass ratio contributed to changes in the upper furnace temperature due to the variation in heating value, high total humidity, and a less homogeneous particle size distribution. Significant differences were also observed in the temperature of the lower furnace area, showing the presence of a foreign object covering the nozzle, which disturbed the ignition process. A comparison of the seal pot temperature showed imbalances as observed from the temperature indicators installed on both sides of boiler, with specific fuel consumption (SFC) increasing by approximately 0.17%. During the performance test, the price of acacia wood bark was 0.034 USD/kg, resulting in fuel cost of 0.023355 USD/kWh, adding 0.061 cent/kWh to coal firing cost. Despite co-firing, the byproducts of the combustion process, such as SO2 and NOx, still met environmental quality standards in accordance with government regulations. However, a comprehensive medium- and long-term impact evaluation study should be carried out to implement co-firing operations using acacia wood bark at coal-fired power plant. Based on the characteristics, such as low calorific value, with high ash, total moisture, and alkali, acacia wood bark showed an increased potential to cause slagging and fouling.

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]

One of the prominent technologies in biomass energy applications is commercial biomass combustion systems. While burning forest-derived biomass is a well-established and proven technology, the combustion of agricultural residues poses more challenges compared to forest-derived fuels. These challenges vary depending on factors such as the design of the combustion system, operational conditions, and the type, physical, and chemical properties of the biomass to be burned. Sintering, agglomeration, slagging, and corrosion are among the major issues that affect the regular and continuous operation of the combustion system, leading to unplanned shutdowns. This study investigates the applicability of common coal ash indices, widely used in the literature to predict these problems, to biomass ash for pre-analysis. Five different biomass feedstocks (reed canary grass, corn stalk, pine, poplar, and tree root) stored in open silos were sampled at two different time periods. Analyses of ash mineral content, chlorine content, sulfur content, and ash fusion temperatures were conducted, and various indices were calculated. Thus, changes in the problems related to biomass fuels depending on storage conditions will also be examined. As a result of the analyses and calculations, no significant relationship or prediction could be demonstrated among the existing indices due to the considerable differences between biomass ash and coal ash, as well as the heterogeneous nature of biomass feedstocks. The contradictory results highlight the necessity for further research and experimental tests under real conditions to establish or verify these indices. It is concluded that a more comprehensive evaluation, taking into account the heterogeneous structure and physicochemical characterization of solid biomass fuels, will be required based on actual combustion experiences. [ABSTRACT FROM AUTHOR]

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

• Chlorine-rich RDF can cause corrosion of metal surfaces. • Ash deposition rate increases with addition of RDF to coal. • Biodegradable- and non-biodegradable-rich RDF separation has a beneficial on ash deposition. • Biodegradable-rich RDF potentially as co-firing fuel. • Blend of 5 wt% non-biodegradable-rich RDF with coal has medium to high risk. The potential impact of ash deposition during the combustion of separated biodegradable- and non-biodegradable-rich waste of refuse-derived fuel (RDF) was evaluated in this study. Theoretical prediction, drop tube furnace experimental combustion, and ash observation were performed to comprehensively investigate their ash deposit behaviour. The results show that high CaO and Cl in RDFs result in severe sintering and rust in the metal surface. The high ash deposit weight and aggregated sticky particles are observed during single-firing RDFs. Furthermore, adding 5 wt% of biodegradable-rich RDF or mixed RDF to coal has a less significant effect on ash deposition. However, several aggregate particles and metal degradation are observed during the combustion of mixed coal with the addition of 5 wt% non-biodegradable-rich RDF. The high Cl in non-biodegradable-rich RDF affects the ash deposition behaviour significantly. This research provides valuable insights into optimising coal-RDF co-combustion, especially with separating biodegradable- and non-biodegradable-rich RDFs. [ABSTRACT FROM AUTHOR]

When low NOx combustion technology is employed in an opposed wall-fired utility boiler, problems of high temperature corrosion and slagging often occurs on the side water wall, especially when burning low-quality coal. In this study, the wall air injection technology was proposed to be developed in a 1000 MWe opposed wall-fired utility boiler for alleviating these problems. Four rows of nozzles for wall air injection were set on the side wall, with three nozzles in each row. The multiphase flow, coal combustion, and heat transfer in the furnace were numerically simulated to obtain the distributions of gas velocity, temperature, and components. Results show that when burning low-quality coal without wall air injection, the gas velocity, temperature, and CO concentration near the side wall is particularly high, where ash tends to melt to cause slagging, and corrosive H2S gas is easily formed to damage the water wall tube. By injecting wall air, which provides oxygen for coal combustion and prevents flue gas from approaching the wall, the gas velocity and temperature near the side wall are both decreased, and the stability of coal combustion in the primary combustion zone gets improved. The CO concentration is significantly decreased near the wall and increased near the furnace center, which helps strengthen the air-staged combustion to benefit the low NOx emission. At the outlet of the furnace, the NO concentration in the flue gas is reduced by 38 mg/Nm3 by wall air injection. [ABSTRACT FROM AUTHOR]

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

Palm kernel shells (PKS) were washed with water and glacial acetic acid (CH3COOH) gradually to prepare them for co-firing with coal. They were then torrefied at 450ºC for one hour. Washing was done to reduce the concentration of ash and alkaline oxides, which would reduce the chance of slagging and fouling. The research was conducted considering that information about washing the PKS with acetic acid and then having them torrefied is very limited and unclear. The results showed that washed and torrefied PKS had better characteristics than those of raw PKS or PKS washed with water. PKS that is washed with acid, torrefied and then blended with coal has low slagging and medium fouling tendencies. However, based on ash fusion temperature, the inclination towards slagging and fouling is high under reducing conditions and medium under oxidation conditions.

. Currently, the transition to alternative fuel during the operation of thermal power plants (TPP) occurs due to the reduction and unreliability of coal supplies, deterioration of its quality, proposals for the use of cheaper fuel, tightening environmental requirements. Alternative fuel means such coal, for the use of which the boilers have not been designed during their design or reconstruction, as well as coal that has not previously undergone industrial or experimental combustion at this TPP. When converting boilers to alternative fuels, the main problems are: slag of the furnace shields and heating surfaces located above the furnace; fouling of convective heating surfaces; instability of non-designed fuel combustion; abrasion of the convective part of boilers; reduction of environmental performance; change in operating conditions of dust preparation, slag removal, ash collection and fuel supply systems. Before conducting experimental combustion of alternative fuels, it is advisable to carry out a preliminary assessment of its combustion possibility using numerical simulation, which makes it possible to identify emerging problems in advance. The most important factor in assessing the possibility of using alternative fuels is the influence of thermal performance, fuel and ash characteristics on the slagging of heating surfaces in the furnace. For a long time, the ability of ash to slagging was determined by the results of a fusibility test by changing the shape of a pyramid of ash particles during its gradual heating to various states according to the specific temperatures, viz. the initial deformation temperature, the softening temperature, the hemispherical temperature. The fusibility test cannot predict the real situation that occurs during the boiler operation. In addition, it does not allow ranking coals according to their tendency to slagging, which is necessary for the preliminary selection of alternative coal. Therefore, it is proposed to use the Watt - Fereday method with Bomkamp’s refinement for calculating the slagging index for ranking coals according to suitability as non-design fuels.

Slagging and fouling of boilers are typical technological problems in the combustion of solid fuels (especially coal and biomass). This study proposes a novel approach based on laser texturing of the near-surface layer of steel used to make heating surfaces of coal-fired boilers. This approach is aimed at improving the resistance of metal surfaces to slagging. The formation of slag deposits on the surfaces of AISI 310 S steel modified by laser radiation has been experimentally studied. The formation of slag melt was analyzed on the surface of modified and polished steel plates during heating to 1400 °C. High-temperature heating and interaction with slag led to a change in the chemical composition of the steel. A significant increase in the chromium content (up to 47%) of the steel surface and the transformation of its texture with the formation of grains up to 2.5 µm in size were established. Laser surface treatment significantly increased the resistance of the steel to such changes and also reduced the grain size to 1.5 µm. As a result of laser modification of surfaces, the temperature of slag formation shifts to higher values (higher by 60–75 °C compared to the unmodified polished surface). The anisotropic texture (cauliflower type) contributed to a decrease in the size of the slag spreading front, and also had by self-cleaning properties from the mineral melt. The latter allows to increase the reliability and energy efficiency of boiler equipment. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a portable spectral analysis instrument based on spontaneous emission spectroscopy (SES) was developed for the in situ, non-intrusive, and quantitative measurement of gaseous Na inside ZD coal-fired boilers, which is mainly applied for predicting slagging in furnaces. This technology is needed urgently because the problem of fouling and slagging caused by high alkali metals in ZD coal restricts the rational utilization of this coal. The relative extended uncertainty for the measurement of gaseous Na concentration is Urel = 10%, k = 2, which indicates that measurement data are reliable under working conditions. It was found that there is a clear linear relationship between the concentration of gaseous Na and fouling in high-alkali coal boilers. Therefore, a fast and efficient method for predicting the slagging and fouling of high-alkali coal boilers can be established by using this in situ online real-time optical measurement. [ABSTRACT FROM AUTHOR]

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

The 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]

The purpose of the work is to select replacing design coal possible options for low slagging potential reasons in the furnace and on adjacent heating surfaces. Solved problems: the main slagging indices (SI) are summarized, based on considering the two main parameters of the formation of ash deposits, namely viscosity and fusibility. An analysis of existing methods for assessing slagging processes of heating surfaces in steam power boilers was carried out. The scientific goal is achieved by the proposed method of ranking coals according to their slagging tendency on power boiler heating surfaces based on their physicochemical properties. The methodology is based on the slagging potential dependence of the fusibility and viscosity ash characteristics, considering the ratio of the ash percentage content to the heating value of coal. The most important result is ranking of 28 coals of various grades (subbituminous, bituminous, anthracite) burned at Russian power plants according to their tendency to form ash deposits on the furnaces of power boilers. The significance of the results obtained lies in the identification of two coal deposits, subbituminous Irsha-Borodinsky and Berezovsky in Easten Siberia and Kuznetsky bituminous in Western Siberia, which are universal during the transition to burning non-design fuel from the slagging potential point of view. The dependences of the change in ash viscosity and SI on the and ratios in ash for Irsha-Borodinsky and Moscow region coals were under consideration. It was concluded that the value of the SI is directly proportional to the load ash content and could differ more by an order of magnitude for different coals.

Among the alternative recycling methods for food waste, its utilization as a renewable biomass resource has demonstrated great potential. This study presents empirical findings pertaining to the cofiring of solid biomass fuel and coal for power generation. Various co-combustion ratios involving food waste biochar (FWB) and coal (100:0, 85:15, 90:10, 95:5, and 0:100) were tested to optimize combustion efficiency, monitor the emissions of NOX, CO, and unburned carbon (UBC), assess ash deposition tendencies, and evaluate grindability. Two types of FWB and sewage sludge were selected as biomass fuels. The results demonstrated that co-combustion involving FWB reduced NOX and UBC emissions compared to coal combustion alone. In particular, the 10% FWB_A blend exhibited the best combustion efficiency. Notably, FWB demonstrated lower tendencies for ash deposition. The ash fusion characteristics were monitored via thermomechanical analysis (TMA), and the corresponding shrinkage levels were measured. Furthermore, FWB exhibited superior grindability compared to both coal and sewage sludge, reducing power consumption during fuel preparation. This study suggests that FWB is a valuable co-combustion resource in coal-fired power plants, thereby facilitating the efficient recycling of food waste while concurrently advancing clean energy generation. Nevertheless, further research is required to validate its practical applicability and promote its use as a renewable resource. [ABSTRACT FROM AUTHOR]

A 46 MW pulverized coal industrial boiler with swirl burner had severe slagging and high NOx emission during actual operation. To solve these problems, a full-scale industrial test was carried out. The flue gas temperature and the composition of exhaust gas were obtained under different ratios of secondary and separated secondary air. The results shown that reducing the ratio of secondary and separated secondary air could delay the ignition of pulverized coal and weaken the flame deflection, which was conducive to slowing down the burner slagging problem. However, it will aggravate the erosion of high temperature flue gas on the back wall, and further aggravated the furnace slagging problem. Changing the air ratio couldn't substantially improve the problem of high exhaust temperature. Properly reducing the ratio of secondary and separated secondary air could effectively control NOx emission. When the ratio of secondary and separated secondary air was reduced from 73:27 to 52:48, the NOx emission was reduced by 44.8%. Reducing the ratio of secondary and separated secondary air leaded to the increase of carbon content in fly ash and slag, but the heat loss of exhaust gas was reduced and the thermal efficiency of boiler was increased. [ABSTRACT FROM AUTHOR]

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

Aiming at the problems of slagging and high temperature corrosion of water wall in a 1 000 MW ultra-supercritical double tangential boiler, the mechanism of slagging and high temperature corrosion of boiler was analyzed by X-ray diffraction (XRD) and X-ray fluorescence (XRF).The results show that the presence of sodium and calcium in coal reduces the ash melting point of coal, causing boiler slagging. Sulfide-type high temperature corrosion is the main type of high temperature corrosion of the boiler. Through coal blending optimization and air distribution adjustment, the coal quality feeding into the furnace and the air distribution mode of the burner were optimized. The results show that selecting low-sulfur and low-slagging coal for blending can effectively alleviate the problem of slagging in the furnace. The increase of the total air volume of the boiler and the reasonable adjustment of the secondary air distribution of the burner can effectively reduce the concentration of the reducing atmosphere in the furnace, and alleviate the problem of high temperature corrosion in the furnace. The prediction results of boiler corrosion tendency by numerical simulation method show that the high-temperature corrosion should be further prevented in the hot corner area of the furnace by adding adherent wind or water wall spraying.

Zhundong coal is rich of alkali metals, and coal ash contains large amounts of Na and K element, which can easily lead to slagging and contamination problems, and affect the normal operation of the boiler. This paper focused on the slagging characteristics of the 2×135 MW circulating fluidized bed (CFB) boilers in the actual operation burning Zhundong coal, and proposed the corresponding renovation plan and operation technology through mechanistic analysis. The results show that increasing the gas velocity at the separator inlet can improve the separation efficiency and circulating rate; increasing the area of platen heating surface and improving the efficiency of separator help to achieve the cooling of the furnace chamber; diluting alkali metal content with pulverized coal boiler ash can reduce the formation of alkali metal sulfate. After the optimization, the target boiler was put back into operation at the original load for about 8 months. The comparison with the operation effect before modification shows that the staining and slagging problems are significantly improved while burning pure Jundong coal at high efficiency and low cost, which verifies the feasibility of the proposed technical solution and also provides a reference for other Jundong coal utilization engineering projects.

In view of widespread slagging on heating surfaces of boilers in power plants， the paper introduces a piezoelectric acceleration sensor for slag impact signal measurement to determine the size and position of the impact of slag on the water wall of the cold ash hopper. In order to verify the accuracy of the method， the slag on boiler water wall was simulated in a laboratory. By the symmetric arrangement of the acceleration sensors in four positions of the cold ash hopper， the four vibration starting times and the maximum amplitudes were measured to judge the fallen slag's approximate area. Moreover， the impact coefficient between the slag block and the cold ash hopper was obtained by calculation fitting. Finally， a sensor was installed in a boiler for on-site test in a power plant. The results show that the method can well locate and measure the slag mass.

Cofiring of coal slime in existing utility boilers is a promising approach to the disposal of coal slime. However, reports about cofiring coal slime with anthracite in the down-fired utility boiler are still few. This work presents a comprehensive study on the combustion characteristics, slagging potential, and NOx emissions of cofiring coal slime and anthracite through lab-scale experiments, numerical simulations, and full-scale industrial measurements in a 600MW down-fired utility boiler. The lab-scale experiments show combustion interactions between anthracite and coal slime, which have both a promotive effect on the ignition of anthracite and inhibitive effect on the combustion and burnout of anthracite. Especially, the inhibitive effect is greater than the promotive effect when the blending ratio of coal slime is above 5%. The addition of coal slime can effectively improve the ash fusion temperature of blended samples. In addition, simulations and full-scale industrial measurements of anthracite cofiring with coal slime are performed in a down-fired utility boiler. The results show that as the blending ratio of coal slime increases, the carbon content in fly ash increases and the boiler efficiency and NOx emissions decrease. A 5% ratio is validated to be a reasonable cofiring ratio of coal slime in the actual operation without no slagging phenomenon. These results provide more insights into the cofiring behavior of coal slime and anthracite and guide the application of blending coal slime in a down-fired boiler. [ABSTRACT FROM AUTHOR]

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

Cofiring coal with various biomasses has received much attention due to environmental factors and is considered a low-cost option. Although cofiring coal with biomass seems feasible, it potentially produces ash, which causes issues in boilers, such as fouling and slagging. This paper comprehensively investigates combustion performances and slagging and fouling behaviors during cofiring biomass and coal. A thorough examination is conducted to investigate the slagging-fouling tendencies employing ash indices. Thermogravimetry-differential scanning calorimetry and a pilot combustion experiment using a drop tube furnace (DTF) are performed to investigate the thermal behavior of the materials, including ash observation using scanning electron microscopy-energy dispersive X-ray analysis and X-ray diffraction systems. Results show that cofiring coal with 25% biomass (mixture of empty fruit bunch and palm frond) has the best combustion performance. It is found that cofiring coal with 25% biomass, either empty fruit bunch or frond, increases the risk of slagging with evidence of the decrease of ash fusion temperatures, deposition material, and sticky material in the probe. The results can provide useful information about cofiring behavior and slagging-fouling tendencies before being implemented into a real plant.

In this study, a portable spectral analysis instrument based on spontaneous emission spectroscopy (SES) was developed for the in situ, non-intrusive, and quantitative measurement of gaseous Na inside ZD coal-fired boilers, which is mainly applied for predicting slagging in furnaces. This technology is needed urgently because the problem of fouling and slagging caused by high alkali metals in ZD coal restricts the rational utilization of this coal. The relative extended uncertainty for the measurement of gaseous Na concentration is Urel = 10%, k = 2, which indicates that measurement data are reliable under working conditions. It was found that there is a clear linear relationship between the concentration of gaseous Na and fouling in high-alkali coal boilers. Therefore, a fast and efficient method for predicting the slagging and fouling of high-alkali coal boilers can be established by using this in situ online real-time optical measurement.

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

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

During coal combustion in boilers, light fly ash particles are carried away along with the hot flue gases and the heavier bottom ash particles fall to the bottom of the boiler. The fly ash particles stick on the convective heat transfer surfaces and the furnace wall, causing fouling and slagging deposition problems during the boiler operation. The fouling and slagging effect reduces the boiler's operational efficiency. This study was motivated by the decline in the operational efficiency of the installed boilers at Sasol synfuel operations in Secunda, Mpumalanga province in the Republic of South Africa. It was assumed that the drop in the boiler efficiency was caused by the coal ash deposition during the boiler operations. The rate of ash deposition and accumulation in the convective heat transfer tubes and furnace water walls during the boiler operation depends on the chemical composition of the coal ash produced during combustion. Coal fly and bottom ash samples were collected from the operational site for laboratory analysis to determine their chemical composition using induced coupled plasma optical emission spectroscopy, induced coupled plasma mass spectroscopy (ICP-OES, ICP-MS) and X-ray fluorescence (XRF) analytical methods. The major, minor and trace elements by mass (%) in the ash samples were obtained from the ICP-OES and ICP-MS, whereas the elemental composition in an oxidised atmosphere was obtained from the XRF analysis. The amount of unburnt coal particles within the ash samples was determined from the loss on ignition (LOI) test. The fouling and slagging prediction during Sasol boiler operation was evaluated using previously developed fouling and slagging indices as a guide using the analysed ash chemical composition results obtained in this study. It was concluded from the analysed results using the guided evaluated indices from the analysed coal ash chemistry that during the operations of Sasol boiler(s) there is a low to medium fouling prediction occurrence on the convective heat transfer tubes and a low slagging in the boiler furnace walls. [ABSTRACT FROM AUTHOR]

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

Purpose. Determination of the main mechanisms of slagging and corrosion of heating surfaces when using coal or other raw materials with a high content of alkali and alkaline earth metals. Experimental determination of mineral phases of ash residues of burning composite raw materials with the participation of salty coal and the influence of component composition on the formation of refractory compounds. Methodology. Critical analysis and generalization of achievements in the developed theories of slagging and corrosion of surfaces during the combustion of problematic carbon raw materials (salty coal, biomass, some wastes, etc.). Determination of the main approaches to the problem of using coal with a high pollution factor. Selection of objects of experimental study on composite raw materials, including coal of different degrees of metamorphism and salinity. Identification of minerals of ash residues of individual fuels and their blends using X-ray phase analysis (X-ray diffraction). Semi-quantitative phase analysis of diffractograms was performed using MATCH! software. Findings. Modern views on the causes of slagging and corrosion processes during the combustion of fuel with a high salt content are highlighted. It has been determined that the process of intensive slagging is associated with a certain ratio of sodium, calcium and iron compounds. The composition and features of the mineral phases of ash residues of composite fuel with the participation of salty coal are experimentally established. The influence of the content of components on the formation of certain mineral phases of mixed ash was determined. Originality. For the first time, the prospects of using two-component blended fuel with the participation of Ukrainian salty coal have been studied. The analysis of minerals in ash residues of salty coal and its blends was carried out. It has been determined that the main part of Na in ash of salty coal of the Bohdanivske deposit in the Northern Donbas is in the form of sulfates and silicates. For the first time, the composition and ways of formation of new refractory mineral compounds in the ash formed during the combustion of composite fuel from coal of different metamorphism and salinity have been established. Practical value. Based on the analysis of literary sources and conducted studies, the dependence of the ash composition on the minerals of the initial fuel and on the ratio of various components in the blends was determined. The proposed approach has a predictive power, as it allows predicting the formation of the main refractory ash minerals. The expediency and prospects of involving salty coal in the fuel base of Ukraine as a component of blended fuels are shown. [ABSTRACT FROM AUTHOR]

In oil palm mills, the slow rate of biodegradation of tenera palm kernel shells leaves a sizable deposit. However, these large mass deposits are potential materials that can be investigated for energy purposes as a suitable alternative due to the limited availability and negative impacts of fossil fuels.Standard methods were used in this study to analyze all major energy related physicochemical properties.Tenera palm kernel shell has moderate moisture content (9.8%), high carbon content (48.63%), low amounts of sulfur (0.48%), nitrogen (0.43%) and ash content (7.6%). The analysis gave volatile matter (75.8%), fixed carbon (6.8%), and a higher heating value of 17.2 MJ/kg. XRD data gave a crystallinity index of 28.29 %, which indicated the presence of low crystalline cellulose. Elemental composition of ash obtained by XRF were used to calculate its sintering, slagging and fouling indices. It has ash deposition tendencies based on calculated slagging-fouling indices. Its FTIR analysis showed the presence of complex compounds. Fixed bed pyrolysis achieved max. biochar, bio-oil, and gas at 350 °C, 550 °C, and 650 °C, respectively. TGA was done at a constant heating rate of 10 °C/min, and the Coats–Redfern method was used to obtain Activation Energy (Ea) value between 41.77–91.83 KJ/mol.Overall, physicochemical parameters indicate that it might be a promising alternative for fossil fuels. Co-firing it with other biomass or coal can help to reduce slagging and fouling. The formation of dioxin and furan is unlikely because its XRF result contains no chlorine and a significant amount of SO3. It has significant thermal deterioration at a low Ea of 41.77 KJ/mol. This type of PKS is recommended for industrial and domestic energy generation via pyrolysis/gasification, and the results are useful for designing efficient thermal reactors for its conversion.

• SRF composition influences on melting characteristic of ashes. • Slag viscosity index Sr forecasts the influence of ash oxide composition on melting. • High concentration of calcium compounds counteracts the ash melting point reduction. • High concentration of calcium compounds prevents the melt phase formation. • The ashes of SRF rich in waste paper (CaCO 3) has high values of the melting point. Various types of solid recovered fuels (SRFs) were investigated, then the waste was chemically leached and co-fired with coal and sewage sludge. Ashes with different properties and oxide compositions were used to explain the influence of various ash components (mainly sodium, potassium and calcium) on the Ash Fusion Temperatures (AFTs). Oxide compositions and empirical indices were determined and the effect of these data on the measured AFTs was investigated. An attempt to explain the effects of specific oxides on SRF melting temperatures using FactSage thermodynamic equilibrium software is presented. Thermodynamic equilibrium calculations are also used to predict the onset temperature of the molten phase, the percentage of molten phase at different combustion temperatures, and the possible solid phases that may exist at different temperatures. The mechanism of transformation of the inorganic substance of SRF turned out to be more complex than that of the mineral substance of coal, which resulted from the variable composition of the SRF. The character of temperature changes of the studied wastes after leaching in water and acetic acid in most cases is similar to the courses determined experimentally. For all investigated ashes from obtained the leaching of SRF wastes, the melting temperature decreases with the applied leaching. Potassium and sodium are the key elements causig the formation of low-melting silicates. Depending on the type of waste and leaching agent the lower the value of the B/A and α indices and the CaO content in ash, the lower the shrinkage temperature of the ash. [ABSTRACT FROM AUTHOR]

Steam power plant (SPP) is the most popular power plant and the largest power generator in Indonesia. SPP uses coal as fuel to produce heat energy. The coal that is taken and used by the SPP must be in accordance with the boiler specifications. However, at the end of 2021, Indonesia experienced a coal shortage crisis, forcing SPP to use a lower coal calorific value specification than usual. Therefore, there is a slagging phenomenon in the wall tube which makes the reliability value of the generator worse. The reliability performance of a power plant can be determined from the calculation of the Net Plant Heat Rate (NPHR). NPHR is a value that represents the amount of energy used to produce electrical energy by a generator. The greater the NPHR value indicates that the boiler efficiency worsen. This is because it used more amount of energy to make 1 kW than usual. To overcome the slagging phenomenon that increases the NPHR value, boiler maintenance companies did an injection of coal additive CORINT PC 99 in the combustion chamber and coal silo. Thus the AFT value of coal is getting higher and the slag will collapse from the wall tube. If this happens, it is expected that the heat transfer from the combustion chamber to the walltube will be better and the NPHR value will decreases. After calculation, the injection of coal additives made the NPHR value increase by 4.08% which indicates that the treatment had no significant impact. However, the success parameter of coal additive injection is not only from the NPHR value but also from the amount of slag that falls and the hardness of the fallen slag. According to these 2 parameters, the injection of coal additive has succeeded in collapsing the slag and softening the slag attached to the walltube therefore it is easier to be cleaned by soot blower. [ABSTRACT FROM AUTHOR]

Calculation and experimental investigations were carried out to determine the parameters of the impulse air jet created by the pneumatic generator of the air-impact system of the cleaning of tubular heat exchangers in boilers. Two configurations (lengthwise and checkerboard) of the arrangement of tubular heat exchangers located at distances from 1.0 m to 2.5 m of nozzle exit were experimentally investigated and the forces acting on them were determined. Numerical modeling of the impulse jet impact on heat exchange tubes was carried out. It was shown that an increase in the pressure of the generated impulse jet to 2.35 MPa makes it possible to significantly increase the acting force from 78 N to 1881 N at a large distance from the exhaust nozzle. The results obtained can be used in the development of specific systems for air impact cleaning systems of boiler units with other sizes and configurations of the heat exchange tubes. [ABSTRACT FROM AUTHOR]

The slagging of heating surfaces by fly ash significantly complicates the long term operation of solid-fuel boilers. Gas pulse technologies offer a potentially convenient, inexpensive, yet efficient way for online slag deposits removal. The creation and application of real boiler cleaning systems using gas pulse technologies is a relatively new direction in the energy sector and requires scientific research on various aspects. In this work, the numerical investigation of the gas-dynamic flow arising when the package of heat-exchange tubes is blown with single air jet created by a pneumopulse cleaning system has been carried out. The forces acting on the heat-exchange tubes located at distances 1.0 m and 2.0 m from the exhaust nozzle with various configurations of tubes in the package have been determined. It is shown that an increase in the pressure of the generated air jet makes it possible to significantly increase the acting forces at large distances from the exhaust nozzle. The results of this study and similar calculations for real geometry will increase the validity of engineering solutions used in the development of pneumopulse cleaning systems for large power boilers. [ABSTRACT FROM AUTHOR]

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

The 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]

• Alkali metals in herbaceous biomass result in numerous fuel utilization problems. • Ashless biomass technique can extract alkali metals in mild conditions. • Herbaceous kenaf was evaluated as an alternative fuel for coal-fired power plants. • Ashless kenaf exhibited favorable combustion and fouling/slagging characteristics. • Ashless herbaceous biomass can be used as a partial fuel for power plants. The use of herbaceous biomass as an alternative fuel for coal-fired power plants is a promising strategy for achieving carbon neutrality. However, it should be noted that herbaceous biomass contains a higher proportion of alkali metals in its ash than coal or wood pellets. This can give rise to a number of significant operational issues, including fouling and slagging, as well as environmental concerns, such as the emission of particulate matter (PM). In this study, ashless biomass technology, which selectively removes alkali metals under mild conditions, was applied to pretreat herbaceous biomass (kenaf). The combustion and emission characteristics of the pretreated biomass, including the unburned carbon (UBC), sulfur oxides (SOx), nitrogen oxides (NOx), and PM, and its slagging and fouling formation tendencies, including the capture efficiency (CE), viscosity, slagging and fouling index, and thermo-mechanical analysis, were then compared with those of coal and wood pellets using a drop tube furnace. The results demonstrated that kenaf treated with ashless biomass technology exhibited the most favorable combustion and emission characteristics (lowest UBC, SOx, NOx, and PM). Moreover, the tendency to form slagging and fouling was slightly reduced (nearly a 20% lower CE, a slightly higher viscosity, and a higher ash melting temperature than in raw kenaf). Consequently, ashless biomass technology can enhance combustion and emission characteristics by eliminating alkali metals and mitigate the formation of slagging and fouling, thereby enabling the partial utilization of herbaceous biomass as fuel in actual power plants. [ABSTRACT FROM AUTHOR]

THE PURPOSE. Comprehensive research of the slagging intensity is the heating surfaces of the BKZ-420-140 boiler unit with solid slag removal at the Abakan CHP when burning non-project fuels. The relevance of the work is due to the technical necessity and economic feasibility of conversion boiler units to combustion of non-design coals. METHODS. The problem has been analyzed by methodology for conducting complex tests, measurements and processing of experimental data, as well as the results of experimental and computational studies of a boiler unit when operating on coals of various qualities. RESULTS. Qualitative and quantitative parameters for assessing the properties of off-design coals and their behavior in real operating conditions of radiation, semi-radiation and convective conditions, taking into account their modes and design functions, have been obtained. CONCLUSION: A computational analysis of the operating modes of boiler units when burning non-design fuels showed that a promising technology for involving non-design coals in the fuel and energy balance of a thermal power plant is providing a scientifically based mixture of design and nondesign fuels.Analysis of the slagging and polluting properties of non-design coals makes it possible to predict changes in the characteristics of the thermal efficiency of heating surfaces and to develop many practical recommendations for optimizing the parameters of the cleaning equipment installed on the boiler.Also, mixtures of fuels were determined for which the wall temperatures of the metal of the outlet stack of the superheater increase, which significantly reduces the strength characteristics of the surface.The assessment and prediction of the reliability of the heating surface is carried out by calculating the temperature of the metal wall in the most heat-stressed place.

Utilizing biomass energy plays a pivotal role not only in mitigating greenhouse gas emissions but also in achieving carbon neutrality and environmental sustainability. The primary objective of this study was to quantify gas emissions, ash properties, and the bioenergy potential of the ginger residue (Zb) combustion in response to the air and oxygen-enriched atmospheres by using thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy. The primary degradation of the Zb combustion occurred between 144 and 432 °C. Compared with the 79 % CO 2 /21 % O 2 atmosphere at the same heating rate, the 79 % N 2 /21 % O 2 atmosphere favored the Zb combustion. The combustion gas products were consistent in both atmospheres and predominantly occurred between 150 and 550 °C. The combustion process in both atmospheres adhered to the mechanism of random nucleation, signifying a highly reactive and favorable reaction system. The joint optimization based on an artificial neural network confirmed that the primary temperature for achieving maximum heat release and minimal gas emissions in both atmospheres varied between 575 and 1000 °C. Overall, Zb serves as an environmentally friendly and renewable resource for biomass energy production. Findings of this study can provide a basis for bioenergy production, pollution control, and optimizing efficiency in the industrial applications of the Zb combustion. [Display omitted] • The increasing heating rate improved combustion efficiency of Zingiber officinale (Zb). • Zb combustion was best described by randomly coalescing nuclei on a single particle. • A majority of gaseous byproducts were emitted between 150 and 550 °C. • Zb ash exhibited high alkalinity, low melting point, and high slagging tendency. • Average activation energy was 172.56 kJ/mol (N 2 /O 2) and 163.25 kJ/mol (CO 2 /O 2). [ABSTRACT FROM AUTHOR]