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Øyvind Skreiberg - One of the best experts on this subject based on the ideXlab platform.
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Upgrading Biomass Fuels via wet torrefaction: A review and comparison with dry torrefaction
Renewable and Sustainable Energy Reviews, 2016Co-Authors: Quang-vu Bach, Øyvind SkreibergAbstract:Biomass pretreatment is an essential step prior to several thermochemical conversion processes. Wet torrefaction, a Biomass pretreatment method in hydrothermal media or hot compressed water at temperatures within 180-260 °C, has been receiving a lot of attention because it possesses some advantages over other pretreatment methods. Apart from the undoubted benefits of upgrading Biomass Fuels to closer to coal properties, wet torrefaction has the capacity to work with wet or even extremely wet Biomasses and enhance the ash removal from the Biomass. The technology has recently attracted great interest from both academic groups and industrial companies. This review aims at providing a comprehensive overview of recent research and development activities in the field with focus on improvements in the chemical, physical and fuel properties of the solid product after wet torrefaction. Moreover, a brief introduction to dry torrefaction, a more conventional thermal pretreatment of Biomass in the absence of oxygen under atmospheric pressure and in a temperature range of 200-300 °C, is also given and compared with wet torrefaction. Main differences in the properties of the solid products from the two torrefaction methods are also discussed.
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effects of wet torrefaction on pyrolysis of woody Biomass Fuels
Energy, 2015Co-Authors: Quang-vu Bach, Khanh-quang Tran, Øyvind Skreiberg, Thuat T TrinhAbstract:The pyrolysis of Norway spruce and birch woods under nitrogen atmosphere was studied by means of a thermogravimetric analyzer operated in the non-isothermal mode, followed by a kinetic analysis employing a three-pseudo-component model with nth-order reactions. Raw woods and the woods treated via wet torrefaction in the conditions of various temperatures (175, 200, 225 °C) and holding times (10, 30, 60 min) were included in this work. The study showed that wet torrefaction resulted in higher pyrolysis peaks for the woods, but less mass of volatiles was released during pyrolysis. The effects of wet torrefaction on pyrolysis of the lignocellulosic components are different. The activation energy of hemicellulose was significantly reduced by wet torrefaction. However, those for cellulose and lignin were slightly increased by wet torrefaction.
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comparative assessment of wet torrefaction
Energy & Fuels, 2013Co-Authors: Quang-vu Bach, Khanh-quang Tran, Øyvind Skreiberg, Roger A Khalil, Gulaim A SeisenbaevaAbstract:Wet torrefaction of typical Norwegian Biomass Fuels was studied within the temperature window of 175–225 °C, using a benchtop autoclave reactor of 250 mL in volume from Parr Instrument. Two types of local Biomass Fuels were employed as feedstock, Norway spruce (softwood) and birch (hardwood). Effects of process parameters including pressure, reaction temperature, holding time, and feedstock particle size on the yield and properties of the solid products were investigated. It appears that birch wood is more reactive and produces less solid products than spruce wood in the same wet torrefaction conditions. Increasing pressure above the saturated vapor pressure of water enhances the torrefaction rate. Both reaction temperature and holding time have significant effects on solid product yield and fuel properties of wet torrefied Biomass. The yield of solid products is slightly reduced with decreasing feedstock particle size. The ash content of Biomass fuel is significantly reduced by wet torrefaction. In addit...
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tga and macro tga characterisation of Biomass Fuels and fuel mixtures
Fuel, 2011Co-Authors: Alexandra Skreiberg, Øyvind Skreiberg, Judit Sandquist, Lars SorumAbstract:The thermal behaviour of selected Biomass Fuels and mixtures as wood, demolition wood, coffee waste and glossy paper was investigated using a thermogravimetric analyzer (TGA) and a macro-thermobalance (macro-TGA). A kinetic model, involving first-order independent parallel reactions, was applied to results obtained from pyrolysis TGA experiments. The pyrolysis rate was considered as the sum of the main Biomass pseudo-components, namely cellulose, hemicellulose and lignin. Additionally, the thermal behaviour of the same Fuels was investigated at combustion conditions in the TGA, including ignition behaviour. The thermogravimetric analysis showed that each single fuel had pyrolysis and combustion characteristics based on its own main pseudo-components (hemicellulose, cellulose and lignin). The pyrolysis and combustion characteristics of selected fuel mixtures and the gas composition analysis from macro-TGA experiments showed respectively quantitative and qualitative summative behaviour based on the single Fuels.
Ingwald Obernberger - One of the best experts on this subject based on the ideXlab platform.
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fuel indexes a novel method for the evaluation of relevant combustion properties of new Biomass Fuels
Energy & Fuels, 2012Co-Authors: Peter Sommersacher, Thomas Brunner, Ingwald ObernbergerAbstract:The increasing demand for Biomass Fuels leads to the introduction of new Biomass Fuels into the market. These new Biomass Fuels (e.g., wastes and residues from agriculture and the food industry, short rotation coppices, and energy crops) are usually not well-defined regarding their combustion behavior. Therefore, fuel characterization methods with a special focus on combustion-related problems (gaseous NOx, HCl, and SOx emissions, ash-melting behavior, and PM emissions) have to be developed. For this purpose, fuel indexes are an interesting option. Fuel indexes are derived from chemical fuel analyses and are checked and evaluated regarding their applicability by measurements performed at lab- and real-scale combustion plants for a large variety of Fuels. They provide the possibilities for a pre-evaluation of combustion-relevant problems that may arise from the use of a new Biomass fuel. A possible relation to describe the corrosion risk is, for instance, the molar 2S/Cl ratio. The N content in the fuel is...
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experimental investigation of nitrogen species release from different solid Biomass Fuels as a basis for release models
Fuel, 2008Co-Authors: Gerhard Stubenberger, Robert Scharler, Selma Zahirovic, Ingwald ObernbergerAbstract:Abstract Experimental data on the release of NOx precursors from solid Biomass Fuels during thermal conversion are necessary to study N release in general and to supply reliable data for the purpose of packed bed and gas phase conversion model development and validation. In this work the release of NOx precursors was studied at a lab-scale pot furnace (batch reactor) by taking measurements during the conversion process of solid Biomass in a packed bed. The investigations were carried out with relevant woody Biomass Fuels, which cover a broad range of fuel N contents: sawdust, bark, waste wood and MDF board. The most important NOx precursor detected above the fuel bed under fuel rich conditions was NH3, while HCN was almost insignificant with the exception of sawdust. NO was detected mainly under air rich conditions. Furthermore, the experimental data were utilised to derive release functions for the relevant NOx precursors NO, NH3 and HCN. The release functions were implemented in an in-house empirical packed bed combustion model, which serves as a basis for a subsequent CFD N species gas phase calculation.
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physical characterisation and chemical composition of densified Biomass Fuels with regard to their combustion behaviour
Biomass & Bioenergy, 2004Co-Authors: Ingwald Obernberger, Gerold ThekAbstract:Abstract With respect to the use of densified Biomass Fuels in fully automatic heating systems for the residential sector a high quality of these Fuels is required. Several European countries already have implemented standards for such Fuels. In other countries such standards are in preparation or planned. Furthermore, in some countries also standards from associations are existing (e.g. from the Austrian Pellets Association). In addition to these national standards, European standards for solid Biomass Fuels are under development. For producers of densified Biomass Fuels, especially for pellet producers, it is therefore very important to produce high-quality Fuels keeping the limiting values of the standards addressed. However, in this context it has to be considered that as a high fuel quality as is necessary for the combustion of densified Biomass Fuels in automatic small-scale furnaces is not necessary if these Fuels are used in larger industrial furnaces as they are equipped with more sophisticated flue gas cleaning, combustion and process control systems. Two pellet qualities, one for industrial and one for small-scale consumers seem to be more meaningful. Within the framework of the EU-ALTENER-project “An Integrated European Market for Densified Biomass Fuels (INDEBIF)” a questionnaire survey of European producers of densified Biomass Fuels was performed. In this connection the possibility was offered to the producers to participate in an analysis programme with their Fuels. An overview was obtained of the qualities of densified Biomass Fuels offered in the European market, covering pellets and briquettes from Austria, Italy, Sweden, Spain, Norway and the Czech Republic. The parameters analysed were the dimensions of the Fuels, the bulk and the particle density, the water and the ash content, the gross and the net calorific value, the abrasion, the content of starch (as an indication for the use of biological binding agents), the concentrations of C, H, N, S, Cl, K as well as of the heavy metals Cd, Pb, Zn, Cr, Cu, As and Hg. These parameters have been chosen following the Austrian, German, Swiss and Swedish standards for densified Biomass Fuels. The results showed that a majority of the participating producers produce Fuels of high quality. However, wood pellets of some producers show a high abrasion, one of the most important quality parameters for pellets. An increased amount of fines often causes failures in the feeding systems used in the residential heating sector. In order to decrease abrasion, the addition of small amounts of biological binding agents (e.g. maize or rye) is possible. This kind of additive is most common in Austria. Moreover, some producers obviously use not only chemically untreated raw materials or additives, which increase the content of pollutants. Such Fuels cause problems regarding emissions, deposit formation and corrosion. Emission problems are expected due to increased contents of N, Cl, S as well as heavy metals. Increased concentrations of heavy metals additionally contaminate the ash, increased Cl concentrations raise the risk of corrosion. Moreover, an increased content of K has a negative effect on the ash melting behaviour and causes higher aerosol formation, which enhances deposit formation and particulate emissions.
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concentrations of inorganic elements in Biomass Fuels and recovery in the different ash fractions
Biomass & Bioenergy, 1997Co-Authors: Ingwald Obernberger, Friedrich Biedermann, Walter Widmann, Rudolf RiedlAbstract:Abstract Inorganic elements and compounds in Biomass Fuels influence the combustion process and the composition of the ashes produced. Consequently, knowledge about the material fluxes of inorganic elements and compounds during Biomass combustion for different kinds of bioFuels and their influencing variables is of great importance. The results gained will especially influence the future design and control of Biomass furnaces and boilers in order to prevent slagging, fouling and corrosion and to assist in the definition of quality requirements for bioFuels as well as the possibilities of a sustainable ash utilization. For this reason, comprehensive test runs were carried out in several Biomass combustion plants equipped with different combustion technologies and using various Biomass Fuels (wood chips, bark, straw and cereals). During continuous observation periods of at least two days, samples of the Biomass and the different ash fractions were taken and analysed. Furthermore, the most important operating data of the plants were recorded. The results of the material balances for inorganic elements showed that the concentrations of environmentally relevant heavy metals (especially Cd and Zn) in Biomass ashes increase with decreasing precipitation temperature and particle size. This effect is independent of the biofuel used. Consequently, a major requirement for a sustainable ash utilization is a fractionated heavy metal separation, distinguishing between different fly-ash fractions and taking the temperature of fly-ash precipitation into consideration for new furnace technologies. Research has also shown that straw and cereals, as well as their ashes, contain significantly lower amounts of heavy metals than woody bioFuels and wood ashes. The same principles pointed out for environmentally relevant heavy metals are also valid for K, Na, Cl and S. The high concentrations of these elements in the filter fly-ash as well as in the boiler fly-ash are of great relevance for reactions that can take place in the boiler section where the flue gas is subjected to a considerable temperature gradient which is accompanied by chemical reactions, phase transitions and precipitation processes that can support or initiate fouling and corrosion. These effects are of special importance for bioFuels that are rich in alkali metals and Cl such as straw and cereals.
Quang-vu Bach - One of the best experts on this subject based on the ideXlab platform.
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Upgrading Biomass Fuels via wet torrefaction: A review and comparison with dry torrefaction
Renewable and Sustainable Energy Reviews, 2016Co-Authors: Quang-vu Bach, Øyvind SkreibergAbstract:Biomass pretreatment is an essential step prior to several thermochemical conversion processes. Wet torrefaction, a Biomass pretreatment method in hydrothermal media or hot compressed water at temperatures within 180-260 °C, has been receiving a lot of attention because it possesses some advantages over other pretreatment methods. Apart from the undoubted benefits of upgrading Biomass Fuels to closer to coal properties, wet torrefaction has the capacity to work with wet or even extremely wet Biomasses and enhance the ash removal from the Biomass. The technology has recently attracted great interest from both academic groups and industrial companies. This review aims at providing a comprehensive overview of recent research and development activities in the field with focus on improvements in the chemical, physical and fuel properties of the solid product after wet torrefaction. Moreover, a brief introduction to dry torrefaction, a more conventional thermal pretreatment of Biomass in the absence of oxygen under atmospheric pressure and in a temperature range of 200-300 °C, is also given and compared with wet torrefaction. Main differences in the properties of the solid products from the two torrefaction methods are also discussed.
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effects of wet torrefaction on pyrolysis of woody Biomass Fuels
Energy, 2015Co-Authors: Quang-vu Bach, Khanh-quang Tran, Øyvind Skreiberg, Thuat T TrinhAbstract:The pyrolysis of Norway spruce and birch woods under nitrogen atmosphere was studied by means of a thermogravimetric analyzer operated in the non-isothermal mode, followed by a kinetic analysis employing a three-pseudo-component model with nth-order reactions. Raw woods and the woods treated via wet torrefaction in the conditions of various temperatures (175, 200, 225 °C) and holding times (10, 30, 60 min) were included in this work. The study showed that wet torrefaction resulted in higher pyrolysis peaks for the woods, but less mass of volatiles was released during pyrolysis. The effects of wet torrefaction on pyrolysis of the lignocellulosic components are different. The activation energy of hemicellulose was significantly reduced by wet torrefaction. However, those for cellulose and lignin were slightly increased by wet torrefaction.
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comparative assessment of wet torrefaction
Energy & Fuels, 2013Co-Authors: Quang-vu Bach, Khanh-quang Tran, Øyvind Skreiberg, Roger A Khalil, Gulaim A SeisenbaevaAbstract:Wet torrefaction of typical Norwegian Biomass Fuels was studied within the temperature window of 175–225 °C, using a benchtop autoclave reactor of 250 mL in volume from Parr Instrument. Two types of local Biomass Fuels were employed as feedstock, Norway spruce (softwood) and birch (hardwood). Effects of process parameters including pressure, reaction temperature, holding time, and feedstock particle size on the yield and properties of the solid products were investigated. It appears that birch wood is more reactive and produces less solid products than spruce wood in the same wet torrefaction conditions. Increasing pressure above the saturated vapor pressure of water enhances the torrefaction rate. Both reaction temperature and holding time have significant effects on solid product yield and fuel properties of wet torrefied Biomass. The yield of solid products is slightly reduced with decreasing feedstock particle size. The ash content of Biomass fuel is significantly reduced by wet torrefaction. In addit...
Mikko Hupa - One of the best experts on this subject based on the ideXlab platform.
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ash related issues in fluidized bed combustion of Biomasses recent research highlights
Energy & Fuels, 2012Co-Authors: Mikko HupaAbstract:Finland and Sweden are leaders in the use of Biomass Fuels in large-scale boilers. In these countries, the dominating large-scale combustion technology for Biomass Fuels is fluidized-bed combustion (FBC). Biomass Fuels differ in many ways from the standard fossil Fuels used in FBC, such as coal. They often have high moisture contents, lower heating values, and a variety of impurities, such as chlorine, sulfur, phosphorus, nitrogen, and a variety of ash-forming metals. FBC of Biomass Fuels is often connected with operational challenges, which are related to the fuel chemistry and fuel properties. Bed sintering, superheater fouling, and high-temperature corrosion are crucial factors to take into account when Fuels are selected for FBC. It is of vital interest to find ways of predicting the degree of these kinds of ash-related problems for various Fuels or fuel mixtures. This paper reviews some of the recent progress in our understanding of the fate and behavior of ash-forming matter in FBC. The following to...
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chemical forms of ash forming elements in woody Biomass Fuels
Fuel, 2010Co-Authors: Johan Werkelin, Bengtjohan Skrifvars, Maria Zevenhoven, Bjarne Holmbom, Mikko HupaAbstract:Abstract Advanced fuel characterization helps to predict ash fouling and slagging. Chemical fractionation analysis, i.e. sequential leaching in H2O, NH4Ac(aq), and HCl(aq), was applied to the Biomass of spruce, pine, birch, and aspen. All of the Cl in the samples and most of the K, Na, and P were water-soluble; most of the Mg and Mn, and some of the Ca were leached in NH4Ac; most of the Ca was leached in HCl; and most of the Si and S remained insoluble in the Biomass. Ion Chromatography found the water-soluble Cl, P, and S present as Cl−, PO 4 3 - , and SO 4 2 - , respectively, and equimolar concentrations of C 2 O 4 2 - as leached Ca in the acid fraction. The Biomass solids were determined for anionic groups by methylene blue sorption. The contents were lowest in the wood samples (22–118 mmol/kgD.S.) and highest in the bark samples (130–453 mmol/kgD.S.). The closing of the ion charge balance led to a quantitative model for the ash-forming matter: water-soluble salts (KCl, K2HPO4, and K2SO4), acid-soluble minerals (CaC2O4), non-soluble minerals (SiO2), and organically associated ash-forming elements (ionically bonded Ca2+, Mg2+, Mn2+, and K+, and covalently bonded P and S).
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the ash chemistry in fluidised bed gasification of Biomass Fuels part ii ash behaviour prediction versus bench scale agglomeration tests
Fuel, 2001Co-Authors: Maria Zevenhovenonderwater, Mikko Hupa, Rainer Backman, Bengtjohan Skrifvars, T Liliendahl, Christer Rosen, Krister Sjostrom, Klas Engvall, Anders HallgrenAbstract:This paper is part II in a series of two. Ash behaviour modelling of the gasification of four Biomass Fuels is compared with pilot-scale experiments carried out in a pressurised fluidised bed gasifier at the Royal Institute of Technology (KTH) and an atmospheric test rig of Termiska Processer AB (TPS). Experiments were provocative with respect to agglomeration of the bed material. Thus, in the experiments, the agglomeration was allowed to happen without any corrective changes in the operation. Small-scale experiments showed clear defluidisation in five cases. Some degree of bed disturbance or agglomeration occurred in seven out of 13 cases. In nine of these cases, agglomerates were also found in the samples analysed with SEM/EDX analyses. In six out of 13 cases, the thermodynamic multi-phase multi-component equilibrium calculations were in agreement with SEM/EDX analysis, i.e. predicted formation of agglomerates. In two cases, no or small amounts of agglomerates were predicted, nor were these found with SEM/EDX analysis. In two cases out of 13, the modelling predicted some degree of agglomeration while no agglomerates could be detected with SEM/EDX analysis. However, in these cases, agglomerates were found in the pilot-scale experiments. Thus it is shown that the thermodynamic multi-phase multi-component equilibrium calculations are a useful prediction tool for the formation of agglomerates in (pressurised) fluidised bed gasification of Biomass Fuels thereby enhancing the understanding of the chemistry involved.
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the ash chemistry in fluidised bed gasification of Biomass Fuels part i predicting the chemistry of melting ashes and ash bed material interaction
Fuel, 2001Co-Authors: Maria Zevenhovenonderwater, Rainer Backman, Bengtjohan Skrifvars, Mikko HupaAbstract:Abstract This paper is part I in a series of two describing the modelling of the ash-chemistry of seven Biomass Fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The Fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600–900°C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the Fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620°C with each of the seven Biomass Fuels fired. In silica-rich cases such as when firing Miscanthus, Reed Canary Grass, Arundo Donax or using a Si-rich bed material a melt can be expected at temperatures above 770°C. The amount of melt is rather high, i.e. 12–100% of the original ash formed. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620°C. At temperatures above 800°C, a silicate melt can form as well. The amount of melt was high, i.e. 60–300% of the original ash formed, showing a significant contribution of the bed material.
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bed agglomeration characteristics during fluidized bed combustion of Biomass Fuels
Energy & Fuels, 2000Co-Authors: Marcus Ohma, Anders Nordi, Engtjoha Skrifvars, Raine Ackma, Mikko HupaAbstract:The in-bed behavior of ash-forming elements in fluidized bed combustion (FBC) of different Biomass Fuels was examined by SEM/EDS analysis of samples collected during controlled agglomeration test r ...
A Williams - One of the best experts on this subject based on the ideXlab platform.
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pollutants from the combustion of solid Biomass Fuels
Progress in Energy and Combustion Science, 2012Co-Authors: A Williams, J M Jones, M PourkashanianAbstract:Abstract This review considers the pollutants formed by the combustion of solid Biomass Fuels. The availability and potential use of solid bioFuels is first discussed. This is followed by the methods used for characterisation of Biomass and their classification. The various steps in the combustion mechanisms are given together with a compilation of the kinetic data. The chemical mechanisms for the formation of the pollutants: NOx, smoke and unburned hydrocarbons, SOx, Cl compounds, and particulate metal aerosols are outlined. Examples are given of emission levels of NOx and particulates from combustion in fixed bed combustion, fluidised bed combustion and pulverised Biomass combustion and co-firing. Modelling methods for pollutants are outlined. The consequential issues arising from the wide scale use of Biomass and future trends are then discussed.
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combustion properties of some power station Biomass Fuels
Fuel, 2010Co-Authors: L I Darvell, A Williams, J M Jones, B Gudka, X C Baxter, A Saddawi, Alf MalmgrenAbstract:In this study, the combustion properties of three of the UK's commonly imported Biomass Fuels for co-firing, which are palm kernel expellers, shea residue, and waste from olive oil production are examined. The Fuels were characterised and their thermal decomposition properties were studied by thermogravimetric analysis (TGA). Additionally the products from their devolatilisation were identified by gas chromatography-mass spectrometry (py-GC-MS) analysis of the evolved vapours and tars from high heating rate pyrolysis tests. Finally, chars from the Fuels were prepared, analysed, and combustion studies were conducted by TGA-MS to determine the conversion of char-nitrogen to different nitrogen-containing species. In general, the main constituents of their ash fractions were K, Si, Ca and Mg, resulting in high alkali indices, which predict a large tendency to fouling. The pyrolysis and combustion kinetic parameters, estimated from TGA studies of these Fuels and their chars, are much lower than those reported in the literature for lignocellulosic Biomass. It is suspected that there is oil/fat evaporation processes overlapping with the decomposition of their lignocellulosic fractions, which significantly affects the apparent kinetics. The pyrolysis conditions used promoted depletion of nitrogen in the char, resulting in approximately 79-91% of the fuel-N being released with the volatiles. In combustion of the char, NOx and N-2 are the major nitrogen compounds detected. Another primary product, HCN, was detected from the combustion of some of the fuel chars, as well as C2N2.
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modelling methods for co fired pulverised fuel furnaces
Fuel, 2009Co-Authors: M Gharebaghi, M Pourkashanian, J M Jones, R Porter, A WilliamsAbstract:Co-firing of Biomass and coal can be beneficial in reducing the carbon footprint of energy production. Accurate modelling of co-fired furnaces is essential to discover potential problems that may occur during Biomass firing and to mitigate potential negative effects of Biomass Fuels, including lower efficiency due to lower burnout and NOx formation issues. Existing coal combustion models should be modified to increase reliability of predictions for Biomass, including factors such as increased drag due to non-spherical particle sizes and accounting for organic compounds and the effects they have on NOx emission. Detailed Biomass co-firing models have been developed and tested for a range of Biomass Fuels and show promising results.