Slag Deposits Research Articles

Options for managing alkaline steel slag leachate: A life cycle assessment

Management of steel slag (a major by-product of the steel industry) includes the treatment of highly alkaline leachate (pH > 11.5) from rainwater infiltration of slag deposits to prevent adverse impact upon surface or ground waters. This study aims to compare different treatment options for steel slag leachate through a life cycle assessment (LCA). Five options were compared: active treatment by acid dosing (A-H2SO4), active treatment by carbon dioxide dosing (A-CO2), active treatment by calcium chloride dosing (A-CaCl2), passive treatment by cascade and reedbeds with pumping (P-P), and passive treatment by cascade and reedbeds in a gravity-driven configuration (P-G). The functional unit was 1 m3 of treated leachate with pH < 9, considering 24 h and 365 days of operating, maintenance operations every year, and service life of 20 years. Inventory data were obtained from project designers, commercial suppliers, laboratory data and field tests. The environmental impacts were calculated in OpenLCA using the ELCD database and ILCD 2011 method, covering twelve impact categories. The A-CaCl2 option scored worse than all other treatments for all considered environmental impact categories. Regarding human toxicity, A-CaCl2 impact was 1260 times higher than the lowest impact option (A-CO2) for carcinogenics and 53 times higher for non-carcinogenics (A-H2SO4). For climate change, the lowest impact was calculated for P-G < P-P < A-H2SO4 < A-CO2 < A-CaCl2, while for particulate matter/respiratory inorganics, the options ranked as follows P-G < P-P < A-CO2 < A-H2SO4 < A-CaCl2. The major contributor to these impact categories was the Solvay process to produce CaCl2. Higher uncertainty was associated with the categories particulate matter formation, climate change and human toxicity, as they are driven by indirect emissions from electricity and chemicals production. Both passive treatment options had better environmental performance than the active treatment options. Potential design measures to enhance environmental performance of the treatments regarding metal removal and recovery are discussed and could inform operational management at active and legacy steel slag disposal sites.

Atmospheric CO2 Sequestration in Iron and Steel Slag: Consett, County Durham, United Kingdom.

Carbonate formation in waste from the steel industry could constitute a nontrivial proportion of the global requirements for removing carbon dioxide from the atmosphere at a potentially low cost. To utilize this potential, we examined atmospheric carbon dioxide sequestration in a >20 million ton legacy slag deposit in northern England, United Kingdom. Carbonates formed from the drainage water of the heap had stable carbon and oxygen isotope values between -12 and -25 ‰ and -5 and -18 ‰ for δ13C and δ18O, respectively, suggesting atmospheric carbon dioxide sequestration in high-pH solutions. From the analyses of solution saturation states, we estimate that between 280 and 2900 tons of CO2 have precipitated from the drainage waters. However, by combining a 37 year long data set of the drainage water chemistry with geospatial analysis, we estimate that <1% of the maximum carbon-capture potential of the deposit may have been realized. This implies that uncontrolled deposition of slag is insufficient to maximize carbon sequestration, and there may be considerable quantities of unreacted legacy deposits available for atmospheric carbon sequestration.

The Misérègne slag deposit (Valle d'Aosta, Western Alps, Italy): Insights into (pre-)Roman copper metallurgy

The Misérègne hamlet (Fénis village, Valle d'Aosta region, Italy) rises on a huge metallurgical slag deposit, whose origin has so far been unknown. Here we provide the first detailed textural, mineralogical and chemical characterization of the slags and the results of radiocarbon dating of charcoal fragments contained therein. Three types of slags are found, i.e., coarse, massive and flat, which are composed of olivine, spinel and pyroxene crystals in a glassy matrix rich in anorthite ± magnetite/ulvöspinel crystallites. All the slags contain matte droplets, which show a Cu-enrichment from the coarse and the massive slags (intermediate solid solution, ~CuFeS2, or bornite solid solution, ~Cu5FeS4 + abundant pyrrhotite solid solution, ~Fe1−xS) to the flat slags (bornite only). Olivine morphology indicates slow cooling for the massive slags (mostly euhedral crystals), rapid cooling for the coarse slags (dendritic crystals) and slow cooling followed by quenching, consistent with tapping, for the flat slags (euhedral-dendritic transitional crystals). Bulk slag compositions and olivine-spinel geothermometry suggest that the coarse and massive slags are genetically related (T = 880–1090 °C and T = 860–1140 °C for coarse and massive slags, respectively), while the flat slags are distinct higher-temperature melts (T = 1020–1415 °C). The data suggest a multiple-step smelting process, by which an impure chalcopyrite ore, was first smelted to produce relatively Cu-poor matte and coarse and massive slags; the matte was then reprocessed at higher temperature to produce more copper metal and flat slags. Based on radiocarbon dating, the Misérègne slags date back to the II-I century BCE and thus constitute the earliest known record of metallurgical activity in the north-western Italian Alps.

Strategy for Ecologically Closure of Ash and Slag Deposits Using Energetic Crops

In the field of renewable energy, national targets imposed by the European Directive on promoting the use of energy from renewable sources is to reach 24% of gross final consumption of energy by 2020. This paper presents a solution for this target and for sustainable management of ash and slag closed deposits by plantation of energetic crops. Process of plantation was assessed by tracking energetic crops by determining the capacity of metals accumulation in wood biomass, correlations between the crops diameter and height, chemical composition of ash. The obtained data were compared with similar data recorded for other intensive crops. Amount of biomass harvested from 5.3 kg/m2 green table (after 3 years) reveals a good development and production of plantation wood, grown on the surface of ash and slag deposit. Based on obtained experimental data, we propose a model of vegetation with energy plants (Salix sp.) of a deposit of ash and slag after its closure was achieved. By implementing experimental model these surfaces can be reinserted in landscape and economic circuit, being in accordance with the provisions of Order No. 757 of 26/11/2004 for approval the Technical Normative of Waste Storage.

Archaeomagnetic Dating of Pyrotechnological Contexts: a Case Study for Copper Smelting Sites in the Central Timna Valley, Israel

This study is focused on establishing age constraints for several copper slag deposits at the centre of the Timna Valley (Israel) via reconstruction of their ancient geomagnetic intensities as recorded by the individual slag samples at the time of their formation. The results show a correlation between the location of the slag deposits (labelled as individual ‘mounds’ in our survey) and their inferred ages, reflecting varying socio‐economic and political dynamics in the region. While the slag mounds found at the unprotected foothills represent a variety of dates (mostly Early Islamic), the slag mounds on the hilltops are chronologically constrained to the early Iron Age (late 11th to 10th centuries bce), supporting the idea for a need for protection during this period. Furthermore, in comparing the new data with previous archaeomagnetic studies from Timna, we can assert the existence of simultaneous copper production at the archaeological Sites 30, 30a and 34. This gives further support to the claim of intense smelting in the central Timna Valley during the early Iron Age. Finally, this project demonstrates the potential of archaeomagnetic experiments to provide chronological insights, and their particular advantage in addressing pyrotechnology‐related cases.

Deposition and slagging in an entrained-flow gasifier with focus on heat transfer, reactor design and flow dynamics with SPH

Two different types of coal are evaluated in a generic gasifier. The gas and discrete phase in a gasifying process was computed in ANSYS Fluent to determine particle trajectories and deposition rates at the wall. This information serves as input for the slagging tool developed by the authors to simultaneously compute the processes of deposit built-up and slag flow. The tool utilizes the method SPH (Smoothed Particle Hydrodynamics), and due to the particle nature of this method, each particle representing the slag gets its own physical properties such as viscosity or thermal conductivity. Thus the slag's surface and interfaces between solid and liquid layers can be determined without problems. The tool detects critical parts in the gasifier that show increased slag deposit and determines the thickness, temperature profile, and particle distribution of the slag layer. One Puertollano coal and one Colombian coal are evaluated in terms of their slagging propensities, which show different behavior in deposition build-up and flow dynamics. Areas with a low amount of slag matter inside the deposit produce an insulating effect, which changes the physical properties of the slag layer. Predicting the slagging propensities of different types of coal using data acquired from slag simulations can support the gasifier design process.

Early Bronze Age copper production systems in the northern Arabah Valley: New insights from archaeomagnetic study of slag deposits in Jordan and Israel

This paper presents results of an archaeomagnetic study of slag from four Early Bronze (EB) Age copper production sites in the Faynan Copper Ore District and the northern Arabah Valley (modern Israel and Jordan). The results provide age constraints for metallurgical activities at these sites. Together with previously published data, they indicate copper production around ca. 2900 cal. BCE (EB II-III transition) and between ca. 2600-1950 cal. BCE, spanning the later part of the EB III and the entire EB IV period. These data strongly suggest a direct link between Faynan and the Old Kingdom of Egypt, which is reflected in the most significant phase of copper production and trade in the northern Arabah prior to the Iron Age, and in a settlement wave in the Negev Highlands. In addition, the results indicate that during the late EB II copper was smelted up to 40 km away from the mines. This is evident at the unique cultic site of Ashalim, located on the main road between Faynan, southeast of the Dead Sea, and the settled areas in the core of Canaan.

New methods for investigating slag heaps: Integrating geoprospection, excavation and quantitative methods at Meroe, Sudan

This paper describes a multifaceted approach to the investigation of iron slag heaps, focusing on one of the slag heaps at the Royal City of Meroe in Sudan. This study marries together geoprospection data (gradiometry and electrical resistivity transects), topographic data and quantitative excavation data, to provide an analysis and comparison of the total volume, slag component and slag composition of a slag-heap. Significantly, the results demonstrate the limitations of using a topographic only model, but also demonstrate how volumetric modelling must be integrated within quantitative characterisation of slag-heap composition. In this case, quantitative sampling of the slag deposits revealed the composition of the slag assemblage was dominated by a newly defined category of slag which has major implications for reconstructing iron technologies in the Meroitic civilisation. This research highlights the dangers of applying simplistic models and basic investigative strategies to iron slag heaps and furthers the debate on applying volumetric modelling and excavation sampling to unexcavated areas of the finite and important resource of archaeometallurgical deposit sequences.

Deposition and slag flow modeling with SPH for a generic gasifier with different coal ashes using fusibility data

In the simulation of entrained flow reactors for gasification processes, not only the gasification reactions are of interest, but also an understanding of the behavior of the ash particles is crucial since the impact on the operating conditions due to slagging cannot be neglected. In this work a new approach for modeling slagging processes was developed. Most of the conventional models for slag flows are based on an Eulerian approach, but a Lagrangian approach could give a better representation of the free surfaces and the multiphase flow. Therefore, the particle method SPH (Smoothed Particle Hydrodynamics) was chosen to model the slag flow. This method offers advantages over the conventional models for slagging, especially in the field of multiphase simulations. Free surfaces are naturally represented and even break-ups of the slag deposit can be simulated without numerical instability. Here the hydrodynamic SPH method is adjusted by taking into account the non-newtonian behavior of the partly solidified slag, depending on the coal ash composition, temperature and thermochemical properties. The latter was achieved by using FactSage. The interface between liquid and solid slag is represented by a multiphase model. The deposition rate was given as an input parameter to determine the deposition build-up and subsequently the melting process was calculated. The deposition and slag-flow happens simultaneously. To model the complex flow behavior of partly molten slag, the ash fusion test results for two specific coal types were used to determine duration and form of the melting process. Combined with the FactSage data, the slag flow was simulated for a generic gasifier wall and the slag build-up of the two different coal ashes was compared between each other.

Germination and juvenile development of plants on municipal solid waste incineration (MSWI) slag

In order to find sufficient greening measures for MSWI slag deposits, germination and juvenile plant growth on fresh as well as artificially aged municipal solid waste incineration slag were investigated for seeds of three widely used commercial test species (Phleum pratense, Lepidium sativum, and Trifolium alexandrinum) and the widespread weed Amaranthus retroflexus. Adapted Austrian standard tests comprised 2 moisture levels, 2 slag types and 4 different slag concentrations. L. sativum grew well on aged slag, whereas its juvenile growth was clearly inhibited on fresh slag. The grass P. pratense performed better on fresh than on aged slag. Under moist conditions A. retroflexus grew well on aged and on fresh slag, but was the only species with a marked germination delay throughout all mixtures of aged slag. The species with the most continuous development under all conditions was T. alexandrinum. Even on pure aged slag it grew sufficiently under moist conditions. Moderate portions of even fresh MSWI slag do not necessarily inhibit plant germination and growth; only pure slag has a negative effect throughout all species. For successful greening of MSWI slag, various substrate properties like water holding capacity and soil texture seem to be as relevant as nutrient supply, toxicity, salinity and extreme pH.

Application of Exploratory and Spatial Data Analysis (EDA-SDA) to the Investigation of Metal Contamination in Groundwater from Electric Arc Furnace Slag and Dust

Electric arc furnace (EAF) dust and slag, materials which contain high metals in their composition, were improperly disposed in an industrial steel mill site between 1963 and 1999. Previous environmental investigations identified anomalous concentrations of metals in local groundwater but failed to relate these abnormalities to the disposed material or to natural geochemical processes. Aiming to identify the origin of such abnormalities, exploratory and spatial data analysis (EDA-SDA) method was applied on a hydrogeochemical data set obtained through 5 sampling campaigns in 32 groundwater monitoring wells installed upstream and downstream of the area impacted by the steel mill activities. Boxplot class-based and Eh vs. pH maps of physicochemical log-transformed data identified that wells located under the influence of EAF slag deposits in topographic hollows had lower Eh potential and increased electrical conductivity and pH, when compared to wells in the topographical nose of the surveyed area. Metal distribution maps showed that Al, Ca, K, Mg, Na, and Sr were consistently higher in topographic hollows while concentrations of Co, Cu, Cr, and Li were higher near the former steel-making plant, located in the topographical nose. Ba, Fe, Mn, and Zn, important indicators of EAF slag and dust, were observed in both topographic settings. Variable clustering was able to capture the relations among metals and thus validate the log-normalized data structure to be used into wells clustering. Clustering through the mclust algorithm carried out for two and three clusters allowed the distinction among localities that received an input of metals from dust or slag and those not influenced by either residue. This paper demonstrates that EDA-SDA is an effective method to identify areas under the influence of contamination from industrial activities from areas not affected by anthropogenic contamination.

High Chrome Refractory Characterization: Part II. Accumulation of Spinel Corrosion Deposits in Radioactive Waste Glass Melters

High Cr2O3 containing Monofrax™ K‐3 is a robust refractory that is used in radioactive waste glass melters worldwide. Monofrax™ K‐3 contains highly reduced phases. Conversely, many of the radioactive feeds being processed are highly oxidizing. The K‐3 refractory corrosion rates in oxidizing (high nitrate) feeds were ~1.8–2.8 times higher than the rates determined using reducing feeds. The corrosion product formed is a mixture of spinel and glass (slag) that can accumulate on the melter floor. A methodology to calculate the depth of slag deposits from refractory corrosion is presented and verified with slag measurements from the Defense Waste Processing Facility (DWPF) melter after it had processed oxidized feeds for 1.75 years. The calculations show that had the facility continued to process oxidized feeds the melter lifetime (based on when the deposits could have reached and blocked the pour spout riser) would have been ~4.5 years. The DWPF changed to a reducing flow sheet after ~3 years of operation. The lifetimes of Melter #1 and Melter #2, assuming a failure due to pour spout blockage, are calculated as 7.7–12 years based on corrosion rates measured with reducing feeds. Lifetimes of 9 and &gt;11 years have actually been achieved.

Ecological conditions of ponds situated on blast furnace slag deposits located in South Gare Site of Special Scientific Interest (SSSI), Teesside, UK.

Slag, a by-product from the iron and steel industry, has a range of applications within construction and is used in wastewater treatment. Historically considered a waste material, little consideration was given to the environmental impacts of its disposal. South Gare (a Site of Special Scientific Interest) located at the mouth of the Tees estuary, UK, formed on slag deposits used to create a sea wall and make the land behind permanent. Over time, ponds formed in depressions with the water chemistry, being significantly impacted by the slag deposits. Calcium levels reached 504mg/L, nitrate 49.0mg/L and sulphate 1,698mg/L. These levels were also reflected in the composition of the sediment. pH (5.10-9.90) and electrical conductivity (2,710-3,598µS/cm) were variable but often notably high. Pb, Cu and Cd were not present within the water, whilst Zn ranged from 0.027 to 0.37mg/L. Heavy metal levels were higher in surface sediments. Zinc was most dominant (174.3-1,310.2mg/L) followed by Pb (9.9-431mg/L), Cu (8.4-41.8mg/L) and Cd (0.4-1.1mg/L). A sediment core provided a historical overview of the ponds. The ponds were unfavourable for aquatic biodiversity and unsuitable for drinking water abstraction.

Determination of the Activity of Bottom Slag and Deposits on the Pool Walls of the Mr Reactor

The MR multicircuit research reactor is being dismantled at the National Research Center Kurchatov Institute. During the disassembly process, the experimental circuits and working channels were moved from the reactor’s swimming pool into the storage pool. A spectrometric study of the bottom slag and deposits on the walls of the reactor’s swimming and storage pools was conducted. The complex α-, β-, and γ-spectrometric studies showed that the specific activity of the bottom slag and deposits on the walls of the MR pools is significantly higher than that of the water. In terms of these activity values, the slag and wall deposits can be classed as high-level wastes.

Understanding Slag Freeze Linings

Slag freeze linings, the formation of protective deposit layers on the inner walls of furnaces and reactors, are increasingly used in industrial pyrometallurgical processes to ensure that furnace integrity is maintained in these aggressive, high-temperature environments. Most previous studies of freeze-linings have analyzed the formation of slag deposits based solely on heat transfer considerations. These thermal models have assumed that the interface between the stationary frozen layer and the agitated molten bath at steady-state deposit thickness consists of the primary phase, which stays in contact with the bulk liquid at the liquidus temperature. Recent experimental studies, however, have clearly demonstrated that the temperature of the deposit/liquid bath interface can be lower than the liquidus temperature of the bulk liquid. A conceptual framework has been proposed to explain the observations and the factors influencing the microstructure and the temperature of the interface at steady-state conditions. The observations are consistent with a dynamic steady state that is a balance between (I) the rate of nucleation and growth of solids on detached crystals in a subliquidus layer as this fluid material moves toward the stagnant deposit interface and (II) the dissolution of these detached crystals as they are transported away from the interface by turbulent eddies. It is argued that the assumption that the interface temperature is the liquidus of the bulk material represents only a limiting condition, and that the interface temperature can be between T liquidus and T solidus depending on the process conditions and bath chemistry. These findings have implications for the modeling approach and boundary conditions required to accurately describe these systems. They also indicate the opportunity to integrate considerations of heat and mass flows with the selection of melt chemistries in the design of future high temperature industrial reactors.

The legacy of American copper smelting: industrial heritage versus environmental policy

Throughout world history, copper has been a significant metal for a vast number of cultures, from the oldest civilisations on record to the Bronze Age and Greek and Roman antiquity. Though replaced by iron as the primary metal for tools and weapons in ancient civilisations, copper found new resurgence in the nineteenth century when it was discovered to have particularly high thermal and electrical conductivity. Copper mining quickly escalated into a large-scale industry, and because of its vast reserves and innovative mining techniques, the United States seized the reins of global production with the opening of significant copper mines in Tennessee and Michigan in the 1840s and Montana in the 1870s. Copper-mining prosperity and America's dominance of the industry came with a heavy environmental price, however. As rich copper deposits declined with increased mining efforts, large deposits of leaner ores--oftentimes less than one percent pure--had to be mined to keep pace with America's technological thirst for copper. Processing such ore left an inordinate amount of industrial waste, such as tailings and slag deposits from the refining process and toxic materials from the ores themselves, and copper mining regions around the United States began to see firsthand the landscape degradation wrought by the industry. In The Legacy of American Copper Smelting , Bode J. Morin examines America's three premier copper sites: Michigan's Keweenaw Peninsula, Tennessee's Copper Basin, and Butte- Anaconda, Montana. Morin focuses on what the copper industry meant to the townspeople working in and around these three major sites while also exploring the smelters' environmental effects. Each site dealt with pollution management differently, and each site had to balance an EPA-mandated cleanup effort alongside the preservation of a once-proud industry. Morin's work sheds new light on the EPA's efforts to utilise Superfund dollars and/or protocols to erase the environmental consequences of copper-smelting while locals and preservationists tried to keep memories of the copper industry alive in what were dying or declining post-industrial towns. This book will appeal to anyone interested in the American history of copper or heritage preservation studies, as well as historians of modern America, industrial technology, and the environment.

Recycling of Local Qatar?s Steel Slag and Gravel Deposits in Road Construction

Every year, the State of Qatar generates about 400,000 tons of steel slag and another 500,000 tons of gravel as a result of steel manufacturing and washing sand, respectively. The two materials (by-products) are not fully utilized to their best market values. At the same time, infrastructural renewal will take place in Qatar over the next ten years, and there will be a greater demand for aggregates and other construction materials as the country suffers from the availability of good aggregates. This paper presents results obtained on the use of steel slag, gravel and gabbro (control) in hot mix asphalt concrete (HMAC) paving mixtures and road bases and sub-bases. Tests were conducted in accordance with Qatar Construction Specifications (QCS-2010) and results were compared with QCS requirements for aggregates used in these applications. Based on the data obtained in this work, steel slag and gravel aggregates have a promising potential to be used in hot mix asphalt concrete paving mixtures on Qatar’s roads, whether in asphalt base and asphalt wearing courses or as unbound aggregates in the base and sub-base pavement structure.

Identification of Heavy Metals in Wild Plants Grown on Battery Waste

The presence of heavy metals in concentrations higher than their natural level in the environment poses a threat to man, his resources and other components that make up the environment. This study was carried out on wild plants and soil in an abandoned slag deposit site of Exide Battery. Lead (Pb), Cadmium (Cd), Nickel (Ni) and Chromium (Cr) in plant shoots, plant rocks and soil were determined with “Atomic Absorption Spectroscopy”. The trend of accumulation in the plant and soil followed the concentration trend of Pb > Ni > Cr > Cd. The mean concentrations of Pb, Ni, Cr and Cd in the soils were 3262.0 ± 8212.99 mg/kg, 27.89 ± 10.23 mg/kg, 21.65 ± 6.25 mg/kg and 0.60 mg/kg respectively. The mean concentrations of Pb, Ni, Cr, and Cd in plants shoots were 259.21 ± 1012.55 mg/kg, 7.30 ± 10.39 mg/kg, 6.64 ± 10.55 mg/kg and 0.90 ± 1.17 mg/kg respectively. The mean concentrations of Pb, Ni, Cr and Cd in plants roots were: 1515.78 ± 4776.01 mg/kg, 12.86 ± 16.06 mg/kg, 4.60 ± 3.52 mg/kg and 0.76 ± 1.20 mg/kg. From the results obtained it showed that plants have the ability to absorb heavy metals from contaminated soils. Some of these plants had accumulated heavy metals in their tissue but still thrived. The resistant nature and accumulative property of these plants could be looked into and enhanced for phyto-remediation.

Extensive weathering of zinc smelting slag in a heap in Upper Silesia (Poland): Potential environmental risks posed by mechanical disturbance of slag deposits

Slags from base metal smelting are often deposited for over 100years with no barriers between the heap and the surrounding environment. Observations at the external surfaces of the slag heaps may not reflect the state of the slag material inside the slag heap. A slag heap from Zn–Pb ore smelting (Świętochłowice, Upper Silesia, Poland) was disturbed during recent slag removal and the freshly uncovered surfaces are examined in this study. The material forming the interior of the slag heap is fine-grained (up to 5cm) and strongly weathered (called the weathered slag zone) in contrast to the large slag boulders on the surface of the slag heap (up to 2m), which are only slightly weathered. The weathered slag zone is composed of gypsum and hematite plus a mixture of primary and other secondary phases. The weathered material as a whole is chemically more homogenous than unweathered slags and has lower Si and higher Fe, Pb (up to 3wt.%) and Cd (up to 560mg/kg) concentrations. SEM images show that primary slag phases are porous and disintegrated. The examined surfaces are 3–4m high and 10–30m wide suggesting that such slag weathering may have occurred in more extensive parts of the slag heap. Weathering affects slag types with different phase compositions and is therefore controlled by specific conditions occurring within the heap, not by the type of slag. These conditions are so far not well defined, but may include prolonged slag deposition, slow water transfer within the heap and interaction of slags with acid rains common in the Upper Silesia region.The weathered slag zone, when confined within the slag heap, acts as a sink for many potentially toxic elements, decreasing their release to the environment. However, this may change dramatically when the zone is uncovered and its deposit conditions change. Potential risks encompass release of potentially toxic elements from the heap, transport of fine grained particles to the surrounding environment and release of elements when the material is deposited in nearby soils or waters, as well as when it is reused as a construction material.

Experimental Investigation of Biomass Slag Deposit on the Surface of Super-Heaters

Growing attention had been drawn to the use of biomass as fuel for electricity generation in China. However, as a fairly new imported technology in localization, it had met serious problems with slagging and fouling of the super-heaters. The slag deposit on the first super-heaters in a biomass boiler was characterized by XRD, SEM-EDS and XRF to make clear the reason for the slag deposit. According to the results, alkali metal such as K, Na and Ca were predominant in the slag deposit. NaCl and KCl in the form of halite and sylvite were confirmed by XRD.