Species In Ash Research Articles

Coupling Pyrolysis and Gasification Processes for Methane-Rich Syngas Production: Fundamental Studies on Pyrolysis Behavior and Kinetics of a Calcium-Rich High-Volatile Bituminous Coal

The coupling pyrolysis and gasification (CPG) process in the fluidized bed reactor to produce methane-rich syngas is an attractive technology in efficient and clean utilization of coals. Pyrolysis plays a leading role in this technology and other relevant processes. Pyrolysis behavior, gaseous product evolution, and kinetics of a calcium-rich high-volatile bituminous coal were deeply investigated using thermogravimetry coupled with online Fourier transform infrared spectroscopy. The results showed that inherent minerals in the coal were mainly gypsum, calcite, and quartz. Except for SiO2, CaO is the most abundant species in the coal ash. The first-stage mass loss of coal before 654 °C was attributed to functional group cleavage and aromatic ring condensation reactions, during which the relative content of CH4 was the largest among the hydrocarbon gases. The second-stage mass loss was mainly caused by mineral (calcite and gypsum) decomposition. It has demonstrated that the major source of CH4 formation was...

Spatial distribution of chromium on the corroded tube surface characterised by synchrotron X-ray fluorescence (SXRF) mapping and μ-XANES: Co-existence of Ca-rich ash deposits and oxy-firing flue gas

This study aims to explore the effects of lignite ash deposit, in particular the Ca-bearing species in ash on the tube corrosion under the oxy-firing mode. Two tubes, low-alloy steel T23 and austenite SUS347 have been coated with two ash deposits and exposed to oxy-fuel flue gas at 650°C for a total of 50h. The ash deposits were collected from the combustion of a lignite mixed with and without silica additive in a 30 MWth pulverised coal-fired boiler. In this study, the roles of Ca-bearing species including sulphate, free oxide/calcite have been first time revealed by using synchrotron-based X-ray fluorescence (SXRF) and μ-XANES to detail the spatial distribution of individual elements, and in particular the speciation of Cr on the cross-section of tubes. Carburisation of Cr by CO2 is inhibited remarkably upon the co-existence of flue gas and ash deposit. However, the attack from the species in ash deposit other than sodium sulphate is more influential in accelerating the tube corrosion. Calcium sulphate is corrosive against the Cr-rich protective layer formed on the tube surface, resulting in the formation of Cr sulphide even in an exposure time of 50h. Sulfidation of Cr by calcium sulphate is thermodynamically possible under the exposure conditions tested. Moreover, the free calcium oxide and even calcite in raw coal ash deposit are detrimental, accelerating the breakdown of the two tubes upon the formation of Ca chromite (Cr3+) and even chromate (Cr6+). The resultant chromite penetrated underneath the protective layer that is rich in Cr-rich oxide and Fe-Cr spinel, as well as merged intimately with ash deposits. The detrimental effect of free calcium oxide/calcite is more pronounced than calcium sulphate in the 50h tested here. The use of silica additive to coal combustion immobilised the free Ca oxide, thereby forming an extra protective layer that minimised the oxidation of Cr. Consequently, the whole tube remained intact with little being damaged.

Chemical kinetics of Cs species in an alkali-activated municipal solid waste incineration fly ash and pyrophyllite-based system using Cs K-edge in situ X-ray absorption fine structure analysis

We conducted in situ X-ray absorption fine structure (in situ XAFS) analysis at the Cs K-edge to investigate the chemical kinetics of Cs species during reaction in an alkali-activated municipal solid waste incineration fly ash (MSWIFA) and pyrophyllite-based system. Understanding the kinetics of Cs is essential to the design of appropriate conditions for Cs stabilization. In situ XAFS analysis of four pastes, prepared from NaOHaq, sodium silicate solution, pyrophyllite, and MSWIFA with the addition of CsCl, was conducted in custom-built reaction cells at four curing temperatures (room temperature, 60°C, 80°C, 105°C) for approximately 34h. The results indicated that the change in Cs species during reaction at room temperature was small, while changes at higher temperatures were faster and more extreme, with the fastest conversion to pollucite occurring at 105°C. Further analysis using a leaching test and a simple reaction model for Cs species during reaction showed that the pollucite formation rate was dependent on the curing temperature and had a significant negative correlation with Cs leaching. The activation energy of pollucite formation was estimated to be 31.5kJ/mol. These results revealed that an important change in the chemical state of Cs occurs during reaction in the system.

The Characteristics of Zinc and Arsenic from Co-firing of Municipal Sewage Sludge with Biomass in a Fluidized Bed

Fly ash from the incineration of municipal sewage sludge (MSS) contains high phosphorus content and can be a source of phosphorus resource. However, the utilization is limited due to the enrichment of trace metals in the fly ash. Co-firing of MSS and biomass was proposed to reduce the leaching toxicity of trace metals in the fly ash. The present study studies two typical trace metals, arsenic (As) and zinc (Zn), present in the co-firing of MSS and biomass in a bubbling fluidized bed. The influence of biomass share (the relative amount of biomass in the mixture of biomass and MSS), biomass species, and combustion temperatures on the concentrations, speciation, and the leaching toxicity of Zn and As in fly ash was investigated. The results show that Zn is more stable after co-firing of MSS and biomass. The stability of Zn species in the fly ash was the best at the incineration temperature of 1123 K. The leaching concentration of Zn in the fly ash decreased, from a maximum of 22.53 mg/L to the minimum of 11....

Evaluation of frameworks for ecotoxicological hazard classification of waste

A new harmonized EU regulation for the classification of waste came into effect on 1st June 2015, in which the criteria and assessment methods for the classification of hazardous waste are harmonized with other internationally agreed-upon systems for hazard classification of chemicals (CLP). However, criteria and guidance for the assessment of ecotoxicological hazard (Hazard Property 14, HP14) are still lacking for waste classification. This paper have evaluated and compared two HP14 classification frameworks: (i) a calculation method (summation) for mixtures, and (ii) leaching tests. The two frameworks were evaluated by surveying and evaluating ecotoxicological data for Cu, Zn, K and Ca species in bottom ash from incinerated waste, together with geochemical speciation modelling. Classification based on the summation method proved to be highly sensitive to the choice of speciation and ecotoxicological classification. This results in a wide range of critical concentrations triggering hazardous classification (in particular for Cu and Zn). Important parameters governing the availability of toxic elements, such as transformation from one species to another and complexation on organic or inorganic sorbents, are not accounted for. Geochemical modelling revealed that a testing strategy built on CLP based leaching tests (liquid/solid ratio (L/S)⩾10,000, pH range 5.5–8.5) avoids bias and is superior to the summation method with respect to both precision and accuracy. A testing strategy built on leaching tests, designed for risk assessment purposes, (L/S ratio of 10, natural pH of the ash) severely underestimate the hazard associated with the presence of toxic compounds (Cu and Zn), while simultaneously falsely indicate a hazardousness due to the presence of non-toxic compounds (Ca and K). However, the testing methods adopted by CLP are problematic from a practical and functional point of view. To conclude, the L/S ratio and pH were found to be critical for hazard classification based on leaching test methods. Further studies are needed to develop a relevant, practical and functional testing strategy for HP14 hazardous waste classification.

Volatilisation and transformation behavior of sodium species at high temperature and its influence on ash fusion temperatures

Zhundong coalfield is one of the superhuge coalfields newly mined in the Xinjiang Autonomous Region of China. However, operational practices have shown that power plants frequently encounter ash deposition problems during combustion of Zhundong coals because of the volatilisation of sodium species. To address such an issue, in this paper, volatilisation levels of sodium species of different coal ash samples in different conditions were studied. The effects of atmosphere and ratio between the major elements in coal ash were also studied to find the resolvent for prohibiting volatilisation. The results show that two Zhundong coals both with a higher sodium content but different calcium and silicon content induce different ash fusion temperatures (AFTs). The volatilisation levels of Wucaiwan (WCW) coal ashes which have higher calcium but lower silicon content were much higher than XHS coal ashes during ashing and AFTs test process. Further studies found that most of the sodium species in XHS coal ash which have a higher silica content transform to Na6Ca2Al6Si6O24(SO4)2 at high temperature. However, fewer sodium aluminosilicate but greater amount of Ca3Al2Si3O12 was found in WCW coal ash of 1200°C. By analyzing the coal ash compositions, it was found that the volatilisation of sodium species was insignificant for the samples with a SiO2/Na2O ratio of more than 20 or with a (SiO2+Al2O3)/Na2O ratio of more than 25. Calcium species promoted the volatilisation of sodium species, and the volatilisation was insignificant for the samples with a SiO2/CaO ratio of more than 4.

Trace elements and As speciation analysis of fly ash samples from an Indonesian coal power plant by means of neutron activation analysis and synchrotron based techniques

The elemental characterization of coal fly ash samples is required to estimate the coal burning emissions into the environment and to assess the potential impact into the biosphere. Fly ash samples collected from a coal fired power plant in center Java, Indonesia were characterized by instrumental neutron activation analysis at two different facilities (BATAN, ANSTO) and synchrotron based techniques at Elettra Italy. Assessment of thirty (30) elements and an investigation of the potential toxicity of As species in coal fly ash were presented. The results obtained are discussed and compared with those reported from other regions of the world.

Existence and release of sodium in Zhundong coal: effects of treating temperature and silica additives

Zhundong coalfield is the largest integrated coal basin in China and has been only recently discovered. Zhundong coal contains a high amount of sodium, which induces severe slagging. In this study, the existence and transformation of alkali and alkali earth metals in Zhundong coal were investigated, and the effects of treating temperature and silica additives were determined. The results show that most of the Na and partial Ca species in raw Zhundong coal and ash were soluble. Sulphates were found in ash and did not decompose until 1,150°C. In the ash prepared at 500°C, a specific amount of MgCa(CO3)2 was found in the ash and decomposed at >600°C. The release of Na during ashing is mainly attributed to water-soluble Na because of the insignificant change in the acid-soluble and insoluble Na content in ash with increasing treating temperature. Silica additives have an effective function in capturing Na species at high temperatures. With increasing additive mass, the relative content of water-soluble Na is significantly reduced, but more water-insoluble Na is retained in the residual ash. [Received: May 10, 2014; Accepted: August 21, 2014]

Effect of fuel origin on synergy during co-gasification of biomass and coal in CO2

The effect of fuel origin on synergy in coal/biomass blends during co-gasification has been assessed using a congruent-mass thermogravimetry analysis (TGA) method. Results revealed that synergy occurs when ash residuals are formed, followed by an almost complete gasification of biomass. Potassium species in biomass ash play a catalytic role in promoting gasification reactivity of coal char, which is a direct consequence of synergy during co-gasification. The SEM–EDS spectra provided conclusive evidence that the transfer of potassium from biomass to the surface of coal char occurs during co-pyrolysis/gasification. Biomass ash rich in silica eliminated synergy in coal/biomass blends but not to the extent of inhibiting the reaction rate of the blended chars to make it slower than that of separated ones. The best result in terms of synergy was concluded to be the combination of low-ash coal and K-rich biomass.

Chemical characterization and mobility of metal species in fly ash–water system

The present investigation was conducted to study the leaching characteristics, speciation and fractionation of trace and major elements from fly ash. Five liquid-to-solid ratios (L/S) were selected, ranging from 0.5 to 1. The releasing of trace and major elements from fly ash increased as L/S ratios increased or over time (at pH = 2.88). γ-Al(OH)3, Cd3(PO4)2, azurite, jarosite, MnCO3, Pb(OH)2, quartz (SiO2) and ZnCO3 are the solid phases that control Al, Cd, Cu, Fe, Mn, Pb, Si and Zn activities in fly ash leachates. The sequential chemical extraction tests showed that Al, Cd, Cu, Fe, Mn, Pb, Si and Zn were mainly present in the last three fractions, which were Fe–Mn oxides, organics and residual fractions and their leachability could be well-controlled in common natural environment. According to risk assessment code (RAC); Cd, Cu, Mn and Pb show a medium risk, while Zn and Fe shows low risk level, but Al and Si are considered safe to our environment.

Utilization of oil shale combustion wastes for PCC production: Quantifying the kinetics of Ca(OH)2 and CaSO4·2H2O dissolution in aqueous systems

The ash produced during oil shale combustion is classified as waste, however, one could also view it as a low-cost source of lime for the abatement of SO2 and CO2 emissions as well as for the commercial production of precipitated calcium carbonate (PCC)-type filler material. This study focuses on the dissolution mechanisms of the main water-soluble calcium species in oil shale ash–water systems. Reaction models that describe the dissolution of Ca(OH)2 and CaSO4·2H2O in water were developed and the kinetic parameters of the proposed system composed of differential equations were estimated by optimizing the model reproduction of experimental data. The dissolution kinetics of Ca(OH)2 and CaSO4·2H2O were also simulated using the Aspen Plus process modeling platform.

The Mineralogical Characteristics of the Ashes Derived from the Combustion of Lignite, Coal Washery Rejects, and Mustard Stalk

With coal being the predominant and limited source of energy, extraction of energy from lignite, coal-washery rejects, and agro-wastes through combustion is being attempted globally. During combustion, minerals in the fuels undergo various transformations with corresponding impact on the process. Lignite fly ash, Jamadoba fly ash, and Kalptaru fly ash and corresponding fuels like lignite, coal-washery rejects, and mustard stalk from pulverized fuel, fluidized bed, and grate system of combustion at Neyveli, Jamadoba, Kalpataru, respectively, were characterized. Lignite has better fuel characteristics than washery rejects and mustard stalk. Of the major phases, SiO2, Al2O3, and CaO are common, besides Fe2O3 in lignite fly ash and Jamadoba fly ash, and K2O in Kalptaru fly ash. Among minor phases, MgO, Na2O, SO3, P2O5, and TiO2 are common, despite K2O in lignite fly ash and Jamadoba fly ash, and Fe2O3 in Kalptaru fly ash. Other minerals are mullite, silicates, sulphates, and carbonates of Ca in lignite fly ash; K-Al-Si species in Jamadoba fly ash; K/Ca-Al-Si species, and sulphates and carbonates of Ca in Kalptaru fly ash. These minerals are the product of mineralogical transformations, where source and composition of the fuels and operating conditions are crucial. Overall the combustion of lignite is more successful than that of washery rejects and mustard.

Stability of solid-phase selenium species in fly ash after prolonged submersion in a natural river system

Selenium (Se) chemistry can be very complex in the natural environment, exhibiting different valence states (−2, 0, +4, +6) representing multiple inorganic, methylated, or complexed forms. Since redox associated shifts among most of known Se species can occur at environmentally relevant conditions, it is important to identify these species in order to assess their potential toxicity to organisms. In June of 2009, researchers from the US Army Engineer Research & Development Center (ERDC) conducted investigations of the fly ash spilled 6months previously into the Emory River at the TVA Kingston Fossil Plant, TN. Ash samples were collected on site from both the original ash pile (that did not move during the levee failure), from the spill zone (including the Emory River), and from the ash recovery ditch (ARD) containing ash removed during dredging cleanup operations. The purpose of this work was to determine the state of Se in the spilled fly ash and to assess its potential for transformation and resultant chemical stability from its prolonged submersion in the river and subsequent dredging. Sequential chemical extractions suggested that the river environment shifted Se distribution toward organic/sulfide species. Speciation studies by bulk XANES analysis on fly ash samples showed that a substantial portion of the Se in the original ash pile had transformed from inorganic selenite to a mixture of Se sulfide and reduced (organo)selenium (Se(-II)) species over the 6-month period. μ-XRF mapping data showed that significant trends in the co-location of Se domains with sulfur and ash heavy metals. Ten-d extended elutriate tests (EETs) that were bubbled continuously with atmospheric air to simulate worst-case oxidizing conditions during dredging showed no discernible change in the speciation of fly ash selenium. The enhanced stability of the organo- and sulfide-selenium species coincided with the mixture of the ash material with humic materials in the river, corresponding with notable shifts in the ash carbon- and nitrogen-functionality.

The Phase Transformations during Fluidized-Bed Combustion of Biomass

FactSage6.1 was used to study the phase transformation at high temperature when biomass combustion in a fluidized bed reactor. The results show that eutectic was formed during the reaction process, the eutectics are formed mainly by the reaction between the silica in bed particles and the alkali species in biomass ash. The solid phase transformed to melt layer on the surface of sands particle mainly contains potassium, some calcium and magnesium, and also a few phosphorus and chlorine are found in the melt layer. The result utilizing FactSage equilibrium modeling shown that the distribution ratio of potassium in the gas phase increased with the increase of temperature, moreover, the melt of bed material surface increased when defluidized occurred.

Chemical, mineralogical and morphological changes in weathered coal fly ash: A case study of a brine impacted wet ash dump

The mobility of species in coal fly ash (FA), co-disposed with brine using a wet ash handling system, from a coal fired power generating utility has been investigated. The study was conducted in order to establish if the wet ash dump could act as a salt sink. The ash was dumped as a slurry with 5:1 brine/ash ratio and the dam was in operation for 20 years. Weathered FA samples were collected along three cores at a South African power station's wet ash dump by drilling and sampling the ash at 1.5 m depth intervals. A fresh FA sample was collected from the hoppers in the ash collection system at the power station. Characterization of both fresh FA and weathered FA obtained from the drilled cores S1, S2 and S3 was done using X-ray diffraction (XRD) for mineralogy, X-ray fluorescence (XRF) for chemical composition and scanning electron microscopy (SEM) for morphology. Analysis of extracted pore water and moisture content determination of the fresh FA and the weathered FA obtained from the drilled cores S1, S2 and S3 was done in order to evaluate the physico-chemical properties of the FA. The XRD analysis revealed changes in mineralogy along cores S1, S2 and S3 in comparison with the fresh FA. The SEM analysis revealed spherical particles with smooth outer surfaces for the fresh FA while the weathered ash samples obtained from cores S1, S2 and S3 consisted of agglomerated, irregular particles appearing to be encrusted, etched and corroded showing that weathering and leaching had occurred in the ash dump. The moisture content (MC) analysis carried out on the fresh FA (1.8%) and the weathered FA obtained from the drilled cores S1 (41.4–73.2%), S2 (30.3–94%) and S3 (21.7–76.2%)indicated that the ash dump was water logged hence creating favourable conditions for leaching of species. The fresh fly ash (n = 3) had a pH of 12.38 ± 0.15, EC value of 4.98 ± 0.03 mS/cm and TDS value of 2.68 ± 0.03 g/L, the pH of the drilled core S1 (n = 45) was 10.04 ± 0.50, the EC value was 1.08 ± 0.14 mS/cm and the TDS value was 0.64 ± 0.08 g/L. Core S2 (n = 105) had pH of 10.04 ± 0.23; EC was 1.08 ± 0.06 mS/cm and TDS was 0.64 ± 0.04 g/L, while core S3 (n = 66) had pH of 11.04 ± 0.09; EC was 0.99 ± 0.03 mS/cm and TDS was 0.57 ± 0.01 g/L. The changes in pH values can be attributed to the dissolution and flushing out of alkaline oxides like CaO and MgO from the dumped ash. The variations in pH values shows that the fly ash is acidifying over time and metal mobility can be expected under these conditions. The large decrease of EC in the drilled ash cores S1, S2 and S3 compared to the fresh ash indicated a major loss of ionic species over time in the ash dump. The XRF analysis showed the progressive dissolution of the major aluminosilicate ash matrix which influenced the release of minor and trace elements into the pore water enhancing their mobility as the ash dam acidified over time. Brine co-disposal on the ash may have been responsible for the slight enrichment of some species such as Na (0.27–0.56%), SO42− (0.06–0.08%), Mg (0.57–0.96 %) and K (0.02–0.34%) in the disposed weathered FA. However, there was no significant accumulation of these species in the disposed FA despite continuous addition of large volumes of highly saline brine over the 20 year period that the dump existed, indicating that the ash dam was incapable of holding salts and continually released elements to the environment over the lifetime of the dam.

Laboratory Study on the Mobility of Major Species in Fly Ash–Brine Co-disposal Systems: Up-flow Percolation Test

Apart from the generation of fly ash, brine (hyper-saline wastewater) is also a waste material gen- erated in South African power stations as a result of water re-use. These waste materials contain major spe- cies such as Al, Si, Na, K, Ca, Mg, Cl and SO4. The co- disposal offly ash and brine has been practiced by some power stations in South Africa with the aim of utilizing the fly ash to capture the salts in brine. The effect of the chemical interaction of the species contained in both fly ash and brine, when co-disposed, on the mobility of species in the fly ash-brine systems is the focus of this study. The up-flow percolation test was employed to determine the mobility of some major species in the fly ash-brine systems. The results of the analysed elu- ates from the up-flow percolation tests revealed that some species such as Al, Ca and Na were leached from the fly ash into the brine solution while some species such as Mg, Cl and SO4 were removed to some extent from the brine solution during the interaction with fly ash. The pH of the up-flow percolation systems was observed to play a significant role on the mobility of major species from the fly ash-brine systems. The study showedthatsomemajorspeciessuchasMg,ClandSO4 could be removed from brine solution using fly ash when certain amount of brine percolates through the ash.

Speciation of Copper in Ash from a Fluidized-Bed Boiler Fired with Municipal Solid Waste

Copper is one of the most important trace elements in municipal solid waste (MSW) combustion. Knowledge of the speciation of copper is fundamental for the understanding of the effects of copper compounds on the combustion chemistry, the evaluation of the environmental effects of copper in ash leachates, and the development of methods to recover copper from the MSW combustion ash. In this work, an investigation of the speciation of copper in four ash flows from a bubbling fluidized-bed boiler using synchrotron-based X-ray absorption spectrometry is reported. The results showed that copper occurs in oxidation states 0, +1, and +2 in the bed ash and the cyclone ash, i.e., 10–20% Cu0, 25–35% CuI, and 50–60% CuII, whereas the filter ash contained copper only in oxidation state +2. The most common copper compounds in the bed ash are copper metal, Cu2O, CuO, and mixed oxides, such as CuCr2O4. The cyclone ash probably contained a mix of copper metal, Cu2O, CuCl, Cu(OH)2, and CuSO4·5H2O, possibly also CuO. Copper sulfate was found as one of the major species in the filter ash together with a mix of hydroxides and chlorides.

The effects of leaching methods on the combustion characteristics of rice straw

The effects of leaching methods on the removal rate of alkali metals, the combustion characteristics and ash behaviors of rice straw were studied by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA) and scanning electron microscope coupled with energy-dispersive spectroscopy (SEM/EDS), respectively. The results show that the removal rate of alkali metals, maximum rate of volatile releasing and ash content all increase with the concentration of HNO3 used for leaching. De-ionized water leaching reduces the ash content by 10% and has the same effects on straw combustion characteristics as 2.0 kmol m−3 HNO3. 0.5 kmol m−3 H3PO4 can remove 93% of alkali metals in straw and activate the organic bound alkali metals which retard char combustion dramatically. Experimental results also indicate that the alkali metals in straw may decrease the peak temperature and maximum rate of volatile releasing. The maximum rate of char combustion is subjected to the combined actions of the catalytic effect and melting behavior of alkali species in the straw ash.

Mercury stable isotope fractionation in six utility boilers of two large coal-fired power plants

Coal-fired utility boiler (CFUB) emissions of mercury (Hg) represent the largest anthropogenic Hg source to the atmosphere. Hg stable isotope signatures in coal have been shown to vary among coal deposits and coal basins. There is therefore a substantial interest in tracing CFUB Hg emissions at local, regional and global scales. However, CFUB operating conditions, Hg capture technologies and post-emission Hg transformations may potentially alter the original feed coal Hg isotope signatures. Here we investigate Hg isotopic fractionation between feed coal and coal combustion products in six utility boilers of two large power plants in Huainan City, Anhui Province, China. We observe identical trends in all six boilers: relative to feed coal with δ202Hg ranging from −0.67 to −0.18‰, oxidized Hg species in bottom ash and fly ash are enriched in the lighter isotopes with δ202Hg from −1.96 to −0.82‰. Flue gas desulphurization by-product gypsum shows δ202Hg from −0.99 to −0.47‰. No mass independent fractionation was observed during the transport and transformation of Hg inside the boilers. An isotope mass balance suggests that gaseous stack Hg emissions are enriched by up to 0.3‰ in the heavier Hg isotopes relative to feed coal and that the enrichment depends on the Hg capture technology. The observation that oxidized Hg species are enriched in the lighter isotopes suggests that oxidized and reduced forms of Hg in stack emission carry different isotope signatures. This has implications for near-field and far-field Hg emission tracing.

Rapid invasion by an aggressive pathogenic fungus (Hymenoscyphus pseudoalbidus) replaces a native decomposer (Hymenoscyphus albidus): a case of local cryptic extinction?

Abstract Ash dieback caused by the infectious fungus Hymenoscyphus pseudoalbidus currently threatens the common ash, Fraxinus excelsior , in Europe. An intriguing aspect is the morphological and ecological similarity between H. pseudoalbidus and the native saprotroph Hymenoscyphus albidus . We revisited four localities where H. albidus apothecia were collected from 1989 to 2005 and established the current relationship of the species in these Danish ash stands based on microsatellites and differences in ITS sequences (used as CAPs marker). Scottish collections from 2010 supported the hypothesis that Danish herbarium samples prior to 2005 are identical to H. albidus still found in Scotland. The markers further revealed that herbarium samples from 1989 to 1994 were all H. albidus , while the latest collection (2005) was H. pseudoalbidus , which coincides with the first Danish symptom observations. Collections from 2010 were purely H. pseudoalbidus . We suggest that expanding H. pseudoalbidus excludes H. albidus from its niche resulting in H. albidus becoming a rare species in Denmark, which is perhaps already locally extinct.