To systematically investigate high-temperature corrosion of superheaters in biomass combined heat and power (CHP) plants, a long-term test run (5 months) with online corrosion probes was performed in an Austrian CHP plant (28 MW_NCV; steam parameters: 32 t/h at 480 °C and 63 bar) firing chemically untreated wood chips. Two corrosion probes were applied in parallel in the radiative section of the boiler at average flue gas temperatures of 880 and 780 °C using the steel 13CrMo4-5 for the measurements. Corrosion rates were determined for surface temperatures between 400 and 560 °C. The results show generally moderate corrosion rates and a clear dependence upon the flue gas temperatures and the surface temperatures of the corrosion probes, but no influence of the flue gas velocity has been observed. The data are to be used to create corrosion diagrams to determine maximum steam temperatures for superheaters in future plants, which are justifiable regarding the corrosion rate. Dedicated measurements were performed at the plant during the long-term corrosion probe test run to gain insight into the chemical environment of the corrosion probes. From fuel analyses, the molar 2S/Cl ratio was calculated with an average of 6.0, which indicates a low risk for high-temperature corrosion. Chemical analyses of aerosols sampled at the positions of the corrosion probes showed that no chlorine is present in condensed form at the positions investigated. Deposit probe measurements performed at the same positions and analyses of the deposits also showed only small amounts of chlorine in the deposits, mainly found at the leeward position of the probes. Subsequent to the test run, the corrosion probes have been investigated by means of scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses. The results confirmed the deposit probe measurements and showed only minor Cl concentrations in the deposits and no Cl at the corrosion front. Because, in the case of Cl-catalyzed active oxidation, a layer of Cl is known to be found at the corrosion front, this mechanism is assumed to be not of relevance in the case at hand. Instead, elevated S concentrations were detected at the corrosion front, but the corrosion mechanism has not yet been clarified.

Der vorliegende Beitrag analysiert die historische Entwicklung der Bioenergienutzung sowie deren aktuellen Stellenwert in der Energieversorgung Österreichs. In weiterer Folge werden auf Basis von Prognosen die zukünftige Entwicklung der Bioenergienutzung in Österreich sowie die damit einhergehenden Herausforderungen umrissen. Aktuelle Leuchtturmprojekte im Bioenergiesektor und Aspekte aus der österreichischen Bioenergieforschung ergänzen den Beitrag.

Management of municipal and commercial waste in Austria frequently involves mechanical-biological treatment (MBT) followed by incineration. A middle-caloric MBT output stream (lower heating value (LHV) = 9.90 MJ/kg WW, particle size = 20-80 mm) with a high proportion of inert material like stones, bricks, and metals (40.5 %m) is currently incinerated. Under favorable market conditions, it could be economically advantageous to split off a low-caloric heavy fraction (HF) that can be landfilled and to incinerate only the remaining, lighter fraction (LF) with a higher heating value. This study analyzes the specific global-warming potential (100-year GWP per tonne of input waste) of such an additional separation step and of the subsequent treatment processes. Four treatment alternatives were considered: a reference scenario without separation and three separation scenarios – a near-infrared (NIR) sensor-based scenario, an X-ray-transmission (XRT) sensor-based scenario, and a mechanical separation scenario using a diagonal sifter (DS). To calculate the specific GWP, the analysis applied techniques from life-cycle assessment (LCA). Primary data were obtained from pilot-scale and full-scale separation experiments, and from equipment manufacturers. Commercial databases provided secondary data. The results consist of separate LCA models for each scenario, including credits for fossil fuels replaced by LF incineration and HF landfill gas utilization. When only direct separation-related emissions are considered, the DS separation has by far the lowest specific GWP, followed by NIR-based separation, and by XRT-based separation. Overall specific GWP is strongly influenced by the choice of separation technology. It is lowest for the XRT scenario, followed closely by the reference scenario, while the DS and NIR scenarios show considerably higher results. Results are dominated by the net emissions from LF incineration. While incineration emissions are largely compensated by credits from replaced fossil fuels, credits for landfill gas utilization are much smaller than direct landfilling emissions. The ranking of the separation scenarios is largely determined by three waste stream characteristics: the ratio of biogenic to fossil carbon content and the LHV in the LF, and the degradable biogenic carbon content in the HF. Changes in important modeling assumptions leave the ranking between scenarios unchanged. It can be concluded that – given the right choice of
separation technology – a small positive effect of sorting on the overall specific GWP is feasible. This
work demonstrates that global warming effects of waste treatment decisions can be estimated and
considered early in the planning stage of treatment system design.

This publication deals with the characterisation of Jatropha curcas seeds and the oil obtained hereof. The analyzed seeds have been harvested from hedges and plantations in the regions of Teriya Bugu and Bla in Mali in the years 2009 and 2010. The oil is obtained through solvent extraction. Parameters analyzed are those which are relevant for processing of the oil into fatty acid methyl ester (FAME, biodiesel), and include acid value, fatty acid profile and contents of S, P, K, Na, Ca and Mg. All oil samples are suitable for processing into biodiesel, but some of them require pre-treatment because of high contents of free fatty acids and phosphorous. The margin of deviation of acid value and element contents throughout the oil samples depends on the way of cultivation, harvest and storage of the Jatropha curcas plants and seeds. Despite high acid values, all oil samples show high oxidation stability. © 2012 Elsevier Ltd.

Der vorliegende Beitrag analysiert die Auswirkungen unterschiedlicher Brennstoffversorgungsszenarios im Calcinator des Zementherstellungsprozesses auf die emittierten CO2-Emissionen. In weiterer Folge werden die Grenzvermeidungskosten für CO2 im Vergleich zum Referenzszenario (100 % PetCoke) berechnet und dargestellt. Als alternative Brennstoffe werden auf Basis von Betriebserfahrungen sowie großtechnischer Versuche die alternativen Brennstoffe hochkalorischer Fluff (Standardszenario) sowie Schilf (Szenario A) und biogen angereicherter Ersatzbrennstoff (Szenario B) und vergleichend dazu in einer Literaturbasierten Analyse getrockneter Klärschlamm (Szenario C) betrachtet. Um die Auswirkung sich ändernder Marktbedingungen auf die Grenzvermeidungskosten abzubilden erfolgt eine Sensitivitätsanalyse hinsichtlich der Brennstoffgestehungskosten für die alternativen Brennstoffe sowie drei unterschiedliche Preisniveaus für Emissionsrechte und Brennstoffgestehungskosten des Referenzbrennstoffes PetCoke.

The aim of the current study was to investigate the feasibility of membrane contactors for continuous ammonia (NH₃-N) removal in an anaerobic digestion process and to counteract ammonia inhibition. Two laboratory anaerobic digesters were fed slaughterhouse wastes with ammonium (NH₄⁺) concentrations ranging from 6 to 7.4 g/L. One reactor was used as reference reactor without any ammonia removal. In the second reactor, a hollow fiber membrane contactor module was used for continuous ammonia removal. The hollow fiber membranes were directly submerged into the digestate of the anaerobic reactor. Sulfuric acid was circulated in the lumen as an adsorbent solution. Using this set up, the NH₄⁺-N concentration in the membrane reactor was significantly reduced. Moreover the extraction of ammonia lowered the pH by 0.2 units. In combination that led to a lowering of the free NH₃-N concentration by about 70%. Ammonia inhibition in the reference reactor was observed when the concentration exceeded 6 g/L NH₄⁺-N or 1-1.2 g/L NH₃-N. In contrast, in the membrane reactor the volatile fatty acid concentration, an indicator for process stability, was much lower and a higher gas yield and better degradation was observed. The chosen approach offers an appealing technology to remove ammonia directly from media having high concentrations of solids and it can help to improve process efficiency in anaerobic digestion of ammonia rich substrates. © 2012 Elsevier Ltd.

In this study the economic boundary conditions for successful active condensation systems are evaluated.
The concept of active condensation utilizes the flue gas enthalpy exiting the boiler by combining a quench for flue gas condensation and a heat pump. Through the heat pump the flue gas can be cooled down below the dew point of the water vapor. Therefore, the sensible heat as well as the latent heat of water can be recovered. This study evaluates the economic viability  for  different  test  cases.  On  the  one  hand  pellet  boilers  of  small  (10kW)  and  medium  (100kW)  size  are considered. On the other hand wood chip boilers of medium (100kW) and big (10MW) size are studied. The economic analysis shows a decrease in operating costs between 2% and 13%. The payback time is evaluated on a net present value (NPV) method, showing a payback time of 2-10 years for the large scale system and approx. 10-35 years for the medium sized ones.

A one-dimensional single particle model is utilised to investigate the effects of radiation temperature, moisture content, particle size and biomass physical properties on the heating rate in biomass particles during pyrolysis. The model divides the particle into four layers - drying, pyrolysis, char and ash layer - corresponding to the four main stages of biomass thermal conversion. The average of the time derivative of the pyrolysis layer centre temperature weighted by the pyrolysis rate is introduced as an appropriate indicator for the heating rate in the particle during pyrolysis. The influencing parameters on the heating rate are summarised in the Biot number and the thermal time constant, to make the investigation of their effects easier. The heating rate is inversely proportional to the thermal time constant. The effect of a variation of the Biot number on the heating rate is negligible in comparison to the thermal time constant. Therefore, the thermal time constant can be sufficiently used to specify the heating rate regimes during pyrolysis. It is found that for thermal time constants of more than 50 s, pyrolysis takes place in a low heating rate regime, i.e. less than 50 K/min. Additionally, the heating rate during pyrolysis of various biomass types under a wide range of thermal conversion conditions has been examined, in order to classify the heating rate regime of pyrolysis in state-of-the-are combustion/gasification plants. The pyrolysis of wood dust and wood pellets is found to happen always in high heating rate regimes. Therefore, the kinetic parameters obtained by conventional TGA systems (typically with heating rates lower than 50 K/min) are not applicable for them. On the contrary, the pyrolysis of wood logs always happens in low heating rate regimes, which indicates that kinetic parameters obtained by conventional TGA systems can be applied. However, pyrolysis of wood chips can undergo low or high heating rate regimes depending on their particle size. Concerning the moisture content, it can be stated that it does not strongly influence the heating rate regime of certain biomass particles. © 2011 Elsevier Ltd. All rights reserved.

Als feste biogene Brennstoffe gewinnen Pellets durch ihre hohe Energiedichte, ihre gleichbleibende Qualität und die wachsende Nachfrage immer mehr an Bedeutung. Bei der Lagerung von Holzpellets werden Emissionen frei, welche aus Abbaureaktionen von Holzbestandteilen entstehen. Es gibt bereits einige Publikationen, welche das Auftreten und die Zusammensetzung dieser Emissionen in Pelletslagern beschreiben. Es fehlen jedoch noch jegliche Nachweise zur Klärung der ursächlichen Reaktionen, weshalb die Untersuchung der Emissionen aus Pellets und deren Rohstoffen erforderlich ist.
Im Zuge dieser Arbeit werden daher zunächst die Freisetzungsraten von Kohlenmonoxid (CO) und flüchtigen organischen Verbindungen (VOC) verschiedener Holzrohstoffe und Pellets in Lagerungsversuchen untersucht. Des Weiteren erfolgt die Bestimmung des organischen Extraktstoffgehaltes dieser Holzproben mittels Soxhletextraktion. Anschließend werden diese Charakteristika einander gegenübergestellt, um mögliche Zusammenhänge zu identifizieren. Bei den untersuchten Holzarten handelt es sich um die Gemeine Fichte (Picea abies), die Europäische Lärche (Larix decidua) sowie um die Weihrauchkiefer (Pinus taeda). Von diesen drei Holzarten werden verschiedene Späne und Pellets miteinander verglichen. Zudem werden unterschiedliche am österreichischen Markt erhältliche Pellets untersucht. Die höchste Freisetzung von CO wird bei frischen Kieferpellets mit 2,88 mg CO/kg Brennstoff (BS) absolute Trockenmasse (atro)/d gemessen. Die geringste Menge an CO wird von einer handelsüblichen Pelletsprobe mit 0,02 mg CO/kg BS atro/d emittiert. Allen untersuchten Holzproben ist gemein, dass in den Lagerungsversuchen höhere Mengen an CO als an VOC freigesetzt werden. Der organische Extraktstoffgehalt der Kieferproben ist am höchsten. Der geringste organische Extraktstoffgehalt tritt bei den Fichtenhobelspänen auf. Bei allen Proben wird festgestellt, dass der organische Extraktstoffgehalt mit der Pelletierung abnimmt. Zudem wird bestimmt, dass sich mit zunehmender Trocknungstemperatur der organische Extraktstoffgehalt verringert. Ein eindeutiger Zusammenhang zwischen Extraktstoffgehalt und freigesetzten Emissionsmengen kann nicht hergestellt werden.

 Ziel der Diplomarbeit war die Bereitstellung von Messdaten für die Entwicklung eines Gasphasenverbrennungsmodells, welches den niedrig-turbulenten Strömungsbereich und den Einfluss der Strähnenbildung auf den Mischungsfortschritt von partiell vorgemischten Flammen über dem Brennstoffbett von Biomasse-Rostfeuerungen abbildet. Diese Arbeit beschäftigt sich mit der Konstruktion und dem Bau eines Flammenreaktors und einer Gasverteilungsstation zur Erzeugung von kalten Strömungen ohne chemische Reaktion und partiell vorgemischten Flammen mit chemischer Reaktion, welche die niedrig-turbulenten Strömungen über dem Brennstoffbett in Biomasse Rostfeuerungen genähert abbilden sollen. Zur Untersuchung der auftretenden Gas- und Luftsträhnen und deren Einfluss auf den Mischungsfortschritt über dem Biomasse Brennstoffbett, wurde für den Versuchsaufbau ein Düsenkonzept zur Gas- und Luftverteilung verwendet. In kalten Strömungen sollen die Mischungseffekte niedrig turbulenter Strömungen sowie der Mischungsfortschritt aufgrund der Strähnenbildung, entkoppelt von chemischen Reaktionen, untersucht werden. In den Flammen gilt es zusätzliche Einflüsse, wie die Expansion des Gases und die chemischen Reaktionen, zu untersuchen. Im Rahmen dieser Diplomarbeit wurden im Flammenreaktor extraktive FTIR- und RGA-Spezieskonzentrationsmessung in kalten Strömungen und in Flammen sowie optische LDA-Gasgeschwindigkeitsmessungen in kalten Strömungen durchgeführt. Für die finalen Messungen wurden nur Gaskonzentrationsmessungen mittels FTIR und RGA durchgeführt und diskutiert, da die LDA-Messeinheit nicht mehr zur Verfügung stand. Die Messergebnisse in kalten Strömungen mit einem CO2/N2-Gasgemisch und einem Luftstrom, liefern rotationssymmetrische CO2- und O2-Konzentrationsprofile. Die Messergebnisse zeigen, dass der Mischungsfortschritt entlang der Strömungsrichtung weitgehend entkoppelt ist von den Gaseintrittsgeschwindigkeiten vGas=2 m/s bis vGas=4. Die Konzentrationsergebnisse der Messungen mit den CO2/N2/Luft-Gemischen konnten mittels einer Stoffbilanz erfolgreich geprüft werden. Die Messergebnisse in kalten Strömungen entsprechen bezüglich der Gasgeschwindigkeiten zwischen 2 und 4 m/s sowie mit den Reynoldszahlen zwischen 800 und 9000 den laminaren bis niedrig-turbulenten Strömungsbedingungen von partiell vorgemischten Flammen über dem Brennstoffbett in Biomasse Rostfeuerungen. Die Messergebnisse der Flammenmessungen mit einem CH4/Luft-Gasgemisch und einem Luftstrom, liefern mit RGA- und FTIR-Messungen nicht reproduzierbare Ergebnisse innerhalb der Flamme und weisen große Gasspeziesasymmetrien in der Flamme auf. Die Messergebnisse zeigen, dass die Gaseintrittsgeschwindigkeiten vGas=2 m/s bis vGas=4 mit dem Verbrennungsfortschritt von CH4 in Strömungsrichtung gekoppelt sind. Die Konzentrationsergebnisse der Flammenmessungen mit einem CH4/Luft-Gemisch konnten mit den vorhandenen Messwerten nicht erfolgreich mittels einer Stoffbilanz geprüft werden. Zusammengefasst liefen die Konzentrationsmessungen in kalter Strömung sehr gute Messergebnisse in Hinblick auf Strömungsstabilität, rotationssymmetrische Strömungsausbildung und Messgenauigkeit. Für Messungen in kalten Strömungen sind die Messverfahren mittels FTIR und RGA zur Konzentrationsmessung und das LDA-Messverfahren zur Gasgeschwindigkeitsmessung zu empfehlen. Die RGA- und FTIR-Konzentrationsmessungen in den Flammen liefern keine zufriedenstellenden Messergebnisse aufgrund von Flammenasymmetrien sowie dem Einfluss der extraktiven Probenahme mittels einer Probenahmelanze. Für Flammenmessungen im Reaktor sind berührungsfreie, optische Messverfahren mit einer hohen Messauflösung zu empfehlen. Durchlichtverfahren benötigen zwei optische Zugänge zum Messraum. Für die Anwendung von Durchlichtverfahren müsste der Flammenreaktor von einem auf zwei optische Zugänge umgebaut werden.  

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 NO_x, HCl, and SO_x 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 an indicator for NO_x emissions, and the sum of the concentrations of K, Na, Zn, and Pb in the fuel can give a prediction of the aerosol emissions, whereas the molar (K + Na)/[x(2S + Cl)] ratio provides a first indication regarding the potential for gaseous HCl and SO_x emissions. The molar Si/K ratio can supply information about the K release from the fuel to the gas phase. The molar Si/(Ca + Mg) ratio can give indications regarding the ash-melting temperatures for P-poor fuels. For P-rich fuels, the (Si + P + K)/(Ca + Mg) ratio can be used for the same purpose. The fuel indexes mentioned can provide a first pre-evaluation of combustion-relevant properties of biomass fuels. Therefore, time-consuming and expensive combustion tests can partly be saved. The indexes mentioned are especially developed for grate combustion plants, because interactions of the bed material possible in fluidized-bed combustion systems are not considered.

Global trade of biomass-related products is growing exponentially, resulting in increasing 'teleconnections' between producing and consuming regions. Sustainable management of the earth's lands requires indicators to monitor these connections across regions and scales. The 'embodied human appropriation of NPP' (eHANPP) allows one to consistently attribute the HANPP resulting from production chains to consumers. HANPP is the sum of land-use induced NPP changes and biomass harvest. We present the first national-level assessment of embodied HANPP related to agriculture based on a calculation using bilateral trade matrices. The dataset allows (1) the tracing of the biomass-based products consumed in Austria in the year 2000 to their countries of origin and quantifying the HANPP caused in production, and (2) the assigning of the national-level HANPP on Austria's territory to the consumers of the products on the national level. The dataset is constructed along a consistent system boundary between society and ecosystems and can be used to assess Austria's physical trade balance in terms of eHANPP. Austria's eHANPP-trade balance is slightly negative (imports are larger than exports); import and export flows are large in relation to national HANPP. Our findings show how the eHANPP approach can be used for quantifying and mapping the teleconnections related to a nation's biomass metabolism. © 2012 Elsevier B.V.

In large scale industrial processes, such as iron production, or in gasification based process chains (coal/biomass to synthesis gas, fuel, or power, etc.), the separation of CO2 (Carbon Capture-CC) can lead to ecological and procedural benefits. Chemical absorption of CO2 is a well proved technology for CC with comparatively low electrical energy demand. However, the high heat demand, absorption kinetics, CO2 capacity and sorbent degradation are limiting factors for the industrial application. Further investigation and development of sorbent-solutions in relation to specific gas conditions are necessary for optimisation. For testing different sorbent-solutions a mobile test plant was designed and built up. Focus of this work was the evaluation of process key data for CC in blast furnace gas under real conditions. The tests have been carried out continuously up to 300 hours. Aqueous monoethanol-amine (MEA), diethanol-amine (DEA) and methyl-diethanol-amine (MDEA) solutions have been investigated. Detailed analyses of the process gas, analyses of used liquids (chemical properties, degradation products) and the examination of process data lead to further development in process design, control strategies for specific applications and give routes for an efficient implementation of CC to increase the benefit in the overall process chain.

Residential wood combustion causes major effects on the air quality on a global scale. The ambient particulate levels are known to be responsible for severe adverse health effects that include e.g. cardio-respiratory illnesses and cancer related effects, even mortality. It is known that biomass combustion derived emissions are affected by combustion technology, fuel being used and user-related practices. There are also indications that the health related toxicological effects are influenced by these parameters. This study we evaluated toxicological effects of particulate emissions (PM ₁) from seven different residential wood combusting furnaces. Two appliances i.e. log wood boiler and stove represented old batch combustion technology, whereas stove and tiled stove were designated as new batch combustion as three modern automated boilers were a log wood boiler, a woodchip boiler and a pellet boiler. The PM ₁ samples from the furnaces were collected in an experimental setup with a Dekati ® gravimetric impactor on PTFE filters with the samples being weighed and extracted from the substrates and prior to toxicological analyses. The toxicological analyses were conducted after a 24-hour exposure of the mouse RAW 264.7 macrophage cell line to four doses of emission particle samples and analysis of levels of the proinflammatory cytokine TNFα, chemokine MIP-2, cytotoxicity with three different methods (MTT, PI, cell cycle analysis) and genotoxicity with the comet assay. In the correlation analysis all the toxicological results were compared with the chemical composition of the samples. All the samples induced dose-dependent increases in the studied parameters. Combustion technology greatly affected the emissions and the concomitant toxicological responses. The modern automated boilers were usually the least potent inducers of most of the parameters while emissions from the old technology log wood boiler were the most potent. In correlation analysis, the PAH and other organic composition and inorganic ash composition affected the toxicological responses differently. In conclusion, combustion technology largely affects the particulate emissions and their toxic potential this being reflected in substantially larger responses in devices with incomplete combustion. These differences become emphasized when the large emission factors from old technology appliances are taken into account. © 2012 Elsevier Ltd.

The present study describes the application of Fischer Tropsch biowaxes as a feedstock in a pilot-scale hydroprocessing unit at operating conditions very similar to industrial size hydrotreating plants of traditional refineries. The project focus on a future coprocessing of biowax/gasoil blends due to produce bio-products derived from lignocellulosic biomass: crack gases, naphtha, kerosene, diesel and a residual product. Hydro-processing plants operating at mild cracking conditions support the production of high amounts in middle distillates at reduced coke formation. Premium bio-diesel and bio-kerosene with excellent cold flow properties are the main objective of the investigations. Various test runs with different hydrotreating catalysts have been conducted due to determine the influence of waxy feedstock on catalyst behavior and product distribution. Depending on the catalyst selected, the fixed bed reactor streamed by hydrogen operates under specified cracking condition defined by the following parameters: reactor temperature, hydrogen pressure and weight hourly space velocity (WHSV). Test runs with selected catalysts - isodewaxing (IDW), hydro-desulphurization (HDS) and the catalytic deparaffination (CDP) catalyst - have been executed at constant process conditions in order to compare the product spectrum and properties of product groups. Highest amounts of bio-diesel and bio-kerosene with excellent cold flow properties can be obtained with the IDW catalyst. This NiW- based catalyst with special additives generates cleaved and reshaped molecular fragments via skeletal isomerisation increasing the isoparaffin content of naphtha and middle distillates. Further investigations with this catalyst type have been executed due to determine the catalyst aging effect in a separate long term test run. The loss of cracking severity during operation of the catalyst can be observed by a steady decline in conversion. Unsaturated hydrocarbons such as olefins and diolefines in the bio-feedstock support the formation of a coke layer on the catalyst surface resulting in reinforced deactivation. As the consequence naphtha and finally the crack gases and the kerosene fraction are shifted to higher molecular fragments increasing the diesel and residue yield. Physicochemical properties of the product groups obtained during the test run vary and especially the cold flow properties from the diesel and kerosene fraction degrade significant. Balancing the conversion decline of the catalyst in operation can be realized by increasing the reactor temperature and the hydrogen pressure, but the effect is time limited.
 

In this study, we investigated the emissions, including odor, from log wood stoves, burning wood types indigenous to mid-European countries such as Austria, Czech Republic, Hungary, Slovak Republic, Slovenia, Switzerland, as well as Baden-Württemberg and Bavaria (Germany) and South Tyrol (Italy). The investigations were performed with a modern, certified, 8 kW, manually fired log wood stove, and the results were compared to emissions from a modern 9 kW pellet stove. The examined wood types were deciduous species: black locust, black poplar, European hornbeam, European beech, pedunculate oak (also known as “common oak”), sessile oak, turkey oak and conifers: Austrian black pine, European larch, Norway spruce, Scots pine, silver fir, as well as hardwood briquettes. In addition, “garden biomass” such as pine cones, pine needles and dry leaves were burnt in the log wood stove. The pellet stove was fired with softwood pellets.

The composite average emission rates for log wood and briquettes were 2030 mg MJ⁻¹ for CO; 89 mg MJ⁻¹ for NO_x, 311 mg MJ⁻¹ for C_xH_y, 67 mg MJ⁻¹ for particulate matter PM₁₀ and average odor concentration was at 2430 OU m⁻³. CO, C_xH_y and PM₁₀ emissions from pellets combustion were lower by factors of 10, 13 and 3, while considering NO_x – comparable to the log wood emissions. Odor from pellets combustion was not detectable. CxHy and PM10 emissions from garden biomass (needles and leaves) burning were 10 times higher than for log wood, while CO and NO_x rise only slightly. Odor levels ranged from not detectable (pellets) to around 19,000 OU m⁻³ (dry leaves). The odor concentration correlated with CO, C_xH_y and PM₁₀. For log wood combustion average odor ranged from 536 OU m⁻³ for hornbeam to 5217 OU m⁻³ for fir, indicating a considerable influence of the wood type on odor concentration.

Heavy fractions resulting from mechanical treatment stages of Mechanical Biological Treatment (MBT) plants are posing very specific demands with regard to further treatment/disposal as they contain a high portion of inert material as well as a high portion of high calorific components. Based on the current Austrian legal situation (landfill ordinance: max. Higher Calorific Value (HCV) for MBT-fractions to be landfilled = 6,600 kJ/kg DM) this waste stream cannot be landfilled but must be thermally treated. In economic terms it is desirable to separate high calorific from inert waste components in order to allow for a material specific routing taking advantage of the difference in the costs for the downstream treatment / disposal.
In this conference contribution results of extensive processing experiments with the heavy fraction from the mechanical stage of the MBT plant of Umweltdienst Burgenland in Oberpullendorf, Austria, are presented. Experiments have been conducted with three different sensor-based automatic sorting systems (NIR – Multiplexer, NIR – Spectral Imaging, X-Ray transmission) as well as two density based processing technologies (wet treatment with a jigger, dry treatment with a cross flow air separation device). In addition a rotary shredder, which allows selective crushing, followed by screening has been investigated.
The performance of the processing options have been evaluated by characterizing the resulting product streams by means of manual sorting in order to evaluate purity and yield achieved by the respective treatment options. In addition to that chemical and physical parameters relevant for further treatment / disposal steps for the resulting product streams have been analysed. The inert fraction has been evaluated regarding the landfilling on a mass waste landfill on one hand and on a C&D waste landfill on the other hand. The high calorific product stream has been evaluated with regard to its thermal utilization.
Complementing the technical evaluation of the processing options an economical assessment of the processing options looked at including the economical implications of the resulting changes in the routing of the waste streams has been conducted.

A workshop on sampling and analysis of gas impurities (mainly condensables (tar)) in gases from thermochemical conversion processes was held in Berlin at the 19th EU BC+E. Here the outcomes are shortly summarized and the activities in the after course of the workshop are briefly discussed. An international working group formed to further discuss the important topics of analytics in these gas families was formed. Further ongoing and planned activities will be mentioned.

In the last years sampling at various gasification plants has been performed at Bioenergy2020+. The equipment, which is based on the recommendations of the tar guideline, has been further developed and adjusted to specific needs. For an evaluation of the procedure different parts of the equipment were tested with a new developed gas-generating unit. Most effort has been performed at the absorption of BTXE-S and PAH in 2-propanol. Additionally new characterisation-methods for pyrolysis samples with SPE (Solid Phase Extraction) have been tested and a qualitative identification of main components could be achieved. Furthermore tests for stabilisation and storage of samples were done. The results of the investigations represent an ongoing optimisation-work with the aim of establishing an international working-group which will compile guidelines for sampling organic and inorganic components at gasification and pyrolysis plants with different new online and offline methods. The appendix delivers some useful data about the substances and dynamic precipitation in an investigated impinger step.

The idea of co-firing biomass in an already existing coal-fired power plant could play a major contribution in the reduction of carbon dioxide emissions. Huge amounts of unused biomass in terms of agricultural residues such as straw, which is a cheap and local feedstock, are often available. But due to the high amount of corrosive ash elements (K, Cl, etc.), the residues are usually not suitable for co-firing in a thermal power plant. Therefore, the feedstock is converted by low temperature pyrolysis into gaseous pyrolysis products and charcoal. A 3 MW pyrolysis pilot plant located next to a coal-fired power plant near Vienna was set up in 2008. For the process, an externally heated rotary kiln reactor with a design fuel power of 3 MW is used which can handle about 0.6-0.8 t/h straw. The aim is to investigate the fundamentals for scale-up to the desired size for co-firing in a coal-fired power plant. In addition to the desired fuel for the process, which is wheat straw, a testing series for DDGS was also performed. The high amount of pyrolysis oil in the gas had positive effects on the heating value of the pyrolysis gas. Chemical efficiencies of this pyrolysis pilot plant of up to 67% for pyrolysis temperatures between 450°C and 600°C can be reached. The focus of this work is set on the pyrolysis products and their behavior at different pyrolysis temperatures as well as the performance of the pyrolysis process. © 2012 Elsevier B.V.

The objectives of the present study were to: (a) develop an appropriate estimation method for assessing the characteristic ash melting temperatures of different biomass fuels by means of thermodynamic equilibrium calculations (TEC) based on ash analysis data, (b) estimate the correlation between the results obtained from TEC and the experimentally received data for the melting temperatures using a TGA/DSC-method (thermogravimetric analysis/differential scanning calorimetry) and, (c) evaluate the applicability of the TEC and DSC methods as prediction tools for the melting behaviour of biomass ashes in relation to the conventional ash melting test according to DIN 51730. The results are presented for four selected biomass ash samples: straw, miscanthus, beech and bark (spruce). The agreement between the results obtained from TEC and experimental results (TGA/DSC and standard ash melting test) was reasonably good. For comparison between the experimental results and TEC regarding the deformation temperature it is recommended to utilize the temperature range between T15 and T30 estimated by TEC at 15 wt% and 30 wt% molten phase respectively. Differences between calculated melting temperatures T30 for straw (770°C) and bark (1,280°C) on the one side, and experimentally determined data on the other side are lower than 100°C. In the case of miscanthus and beech ash the prediction was with a deviation of around 200°C less precise. Flow temperatures measured as per standard test (DIN 51730) show generally a good agreement with the TEC fusion temperatures at 70 wt% of molten fraction (T70) for straw, miscanthus and bark ash. In case of beech ash is the TEC prediction of T70 (>1,600°C) moved to higher temperatures compared to experimental expected 1,380°C. The results of this study in combination with reliable databases and an appropriate calculation model, qualify the thermodynamic equilibrium calculations as a useful technique for a prediction of the ash melting behaviour including the assessment of characteristic melting temperatures.

A pellet burner directly integrated into the solar storage provides heat and domestic hot water for small
residential applications in an environment-friendly way. The objective of this work was to evaluate the system
performance of a storage integrated pellet boiler in laboratory under transient test conditions. Furthermore, the type
test results according to ÖNORM EN 303-5 [1] of the last decade were compared with monitoring data of systems
with separated boiler and heat storage. The laboratory tests allowed finding relevant parameters and losses, which
influence the system performance. A developed computer simulation model shows the potential to optimize the
performance of the investigated boiler.

Due to the increasing number of different online and offline methods and procedures for sampling at gasification and pyrolysis plants a comparison of the measured values is difficult. About the sampling of tars already a number of detailed guidelines and a common approach are established [2]. In terms of discrete chemical impurities the missing of a guideline for sampling at biomass¬ plants is an obstacle for implementing sampling systems in new plants or experimental assemblies. Nevertheless the knowledge is available at several institutions but it has to be collected. Within this paper the basic challenges of sampling are mentioned, the system at Bioenergy2020+ is explained in detail and about the parameters NH3, H2S & HCN useful results of optimisation are reported. This status should help to point out the need of a reliable library of methods. According the first systematisation of offline and online sampling respectively detection a table of application is proposed. The detailed knowledge for this will be treated and exchanged within an established working group which should lead to a guideline (at least methods library) for sampling of trace components as described.

The utilization of biomass for the substitution of fossil fuels to reduce greenhouse gas emissions in biomass steam gasification plants is a promising technology for the production of electricity, heat, and fuels for transportation. Experience from industrial scale dual fluidized bed steam gasification plants showed a modification of the bed material due to the interaction of the bed material (olivine) with biomass ash components and additives. In this paper the influence of bed material modification on the gasification properties of used olivine from an industrial scale plant in Güssing is compared with the case of fresh olivine. The trials were carried out under similar conditions in a pilot plant at the Vienna University of Technology. The pilot plant trials showed an increase in hydrogen and carbon dioxide in the product gas with the used bed material while the content of carbon monoxide in the product gas decreased. The exothermal water–gas shift reaction is enhanced by the used bed material, resulting in a lower energy demand for the gasification. Tar content was decreased by around 80% for tars detected by gas chromatography–mass spectrometry (GCMS) and the composition of the tar showed less components during the trial with used bed material.

The results obtained with the used bed material at the 100 kW pilot plant are in good agreement with those for the 8 MW industrial plant in Güssing, confirming good scale-up properties from the 100 kW plant to industrial scale plants.

A steam blown dual fluidized bed gasification plant was used to yield a nitrogen (N 2) free product gas (synthesis gas) from various biomass fuels. In addition to the variation of process parameters like temperature, steam to carbon ratio, fluidization rate, and the influence of different bed materials, various feedstock inputs affected the generation of the product gas. This study focuses on the gasification of different biomass feedstock. The variation of biomass implies wood chips, wood pellets, sewage sludge pellets, and straw pellets. The chosen evaluated experimental results are all gained from the uniformly operated "classical" 100 kW "DUAL FLUID" gasifier at Vienna University of Technology at constant gasification temperatures between 800°C and 810°C. In the "classical" design, the gasification reactor is a bubbling fluidized bed. The composition and ash melting behavior of each feedstock is displayed, as well as the ranges of the product gas compositions generated. Beside the main gaseous product gas components, typical content ranges of dust and char are highlighted. The content and composition of tar in the product gas is discussed. Further it is possible to present gravimetrical and gas chromatography coupled with mass spectrometry measured tar values. Not less than five significant component-groups of tar will also be outlined for each feedstock. © 2012 American Institute of Chemical Engineers (AIChE).

Die Verbrennung fester Biomasse gewinnt als nachhaltige Form der Energienutzung zunehmend an Bedeutung. Dabei stellt die Forderung nach einem schadstoffarmen Betrieb von Biomassefeuerungsanlagen bei möglichst hohem Wirkungsgrad eine Herausforderung an deren Regelung dar. Ziel dieser Arbeit ist die Untersuchung und Verbesserung eines existierenden, modellbasierten Regelungskonzepts, welches die Methode der Eingangs-Ausgangslinearisierung zur Regelung sowie einen Erweiterten Kalmanfilter zur Zustandsschätzung vorsieht. Die Arbeiten wurden in Kooperation mit dem Kompetenzzentrum Bioenergy 2020+ anhand einer Versuchsanlage (Flachschubrostfeuerung mit einer Kesselnennleistung von 180 kW) durchgeführt. Dabei lassen sich eine Reihe von Störeinflüssen identifizieren, unter anderem etwa die bei dieser Anlage besonders stark ausgeprägten Schwankungen des abgebauten Brennstoffs. Die geeignete Berücksichtigung dieser Störeinflüsse im Kalmanfilter durch Formfilter wird untersucht. Ebenso erfolgt die Modellierung von variablen Totzeiten und Sensordynamiken, die bei der Messung einzelner Größen auftreten, durch zusätzliche Sensormodelle. Auf Basis dieser Ergebnisse wird ein neuer Kalmanfilter vorgeschlagen und implementiert. Die auftretenden Störeinflüsse führen bei der exakt linearisierten Strecke zu einer Abweichung vom geforderten linearen Übertragungsverhalten. Daher wird auch der Regler dahingehend modifiziert, dass die vom Kalmanfilter rekonstruierten Störgrößen bei der Ermittlung des nichtlinearen Zustandsregelgesetzes verwendet werden. Das modifizierte Regelungskonzept wurde abschließend an der untersuchten Anlage implementiert und experimentell verifiziert. Dabei wurden gegenüber der ursprünglichen Regelung eine deutliche Verbesserung bei der Stabilisierung von Vorlauf- und Sekundärzonentemperatur sowie eine geringere Abweichung des Verbrennungsluftverhältnisses im Brennstoffbett vom vorgegebenen Sollwert erzielt.

In this paper, the work on the development and test of a basic design tool for the automatic performance of parameter studies for the optimisation of biomass combustion plants is presented. The model consists of parameterisation and optimisation routines linked with an in-house developed empirical packed bed combustion model as well as gas phase CFD models especially adapted for biomass grate furnaces. To test and verify the routine developed, it has been applied to the optimisation of a 180 kW_th pilot-scale grate furnace. The main focus was on the minimisation of CO emissions and the pressure loss by changing the diameter and angle of the secondary air nozzles. The simulation results show that the time of the optimisation process can be reduced considerably by the automatic routine developed and the evaluation of several independent design parameters is possible. This new procedure forms an important milestone towards automatic CFD-based furnace and boiler optimisations in the future. © 2013 Elsevier Ltd.

To examine relevant combustion characteristics of biomass fuels in grate combustion systems, a specially designed lab-scale reactor was developed. On the basis of tests performed with this reactor, information regarding the biomass decomposition behavior, the release of NO_x precursor species, the release of ash-forming elements, and first indications concerning ash melting can be evaluated. Within the scope of several projects, the lab-scale reactor system as well as the subsequent evaluation routines have been optimized and tests with a considerable number of different biomass fuels have been performed. These tests comprised a wide variation of different fuels, including conventional wood fuels (beech, spruce, and softwood pellets), bark, wood from short rotation coppice (SRC) (poplar and willow), waste wood, torrefied softwood, agricultural biomass (straw, Miscanthus, maize cobs, and grass pellets), and peat and sewage sludge. The results from the lab-scale reactor tests show that the thermal decomposition behavior and the combustion behavior of different biomass fuels vary considerably. With regard to NO_x precursors (NH_x, HCN, NO, N₂O, and NO₂), NH₃ and, for chemically untreated wood fuels, also HCN represent the dominant nitrogen species. The conversion rate from N in the fuel to N in NO_x precursors varies between 20 and 95% depending upon the fuel and generally decreases with an increasing N content of the fuel. These results gained from the lab-scale reactor tests can be used to derive NO_x precursor release models for subsequent computational fluid dynamics (CFD) NO_x post-processing. The release of ash-forming vapors also considerably depends upon the fuel used. In general, more than 91% of Cl, more than 71% of S, 1-51% of K, and 1-50% of Na are released to the gas phase. From these data, the potential for aerosol emissions can be estimated, which varies between 18 mg/Nm³ (softwood pellets) and 320 mg/Nm³ (straw) (dry flue gas at 13% O₂). Moreover, these results also provide first indications regarding the deposit formation risks associated with a certain biomass fuel. In addition, a good correlation between visually determined ash sintering tendencies and the sintering temperatures of the different fuels (according to ÖNORM CEN/TS 15370-1) could be observed. © 2013 American Chemical Society.

The increased demand for energy from biomass enforces the utilization of new biomass fuels (e.g., energy crops, short-rotation coppices, as well as wastes and residues from agriculture and the food industry). Compared to conventional wood fuels, these new biomass fuels usually show considerably higher ash contents and lower ash sintering temperatures, which leads to increased problems concerning slagging, ash deposit formation, and particulate matter emissions. One possibility to combat these problematic behaviors is the application of fuel additives such as kaolin. In contrast to the usual approach for the application of additives based on an experimental determination of an appropriate additive ratio, this study applies novel and advanced fuel characterization tools for the characterization of biomass/kaolin mixtures. In the first step the pure biomass fuels (softwood from spruce and straw) and the additive were chemically analyzed. On the basis of the analysis theoretical mixing calculations of promising kaolin ratios were conducted. These theoretical mixtures were evaluated with fuel indexes and thermodynamic equilibrium calculations (TEC). Fuel indexes provide the first information regarding high temperature corrosion (2S/Cl) and ash melting tendency (Si + P + K)/(Ca + Mg + Al). TEC can be used for a qualitative prediction of the release of volatile and semivolatile elements (K, Na, S, Cl, Zn, Pb) and the ash melting behavior. Moreover, selected mixtures of spruce and straw with kaolin were prepared for an evaluation and validation of the release behavior of volatile and semivolatile ash forming elements with lab-scale reactor experiments. The validation of the ash melting behavior was conducted by applying the standard ash melting test. It could be shown that the new approach to apply novel and advanced fuel characterization tools to determine the optimum kaolin ratio for a certain biomass fuel works well and thus opens a new and targeted method for additive evaluation and application. In addition, it helps to significantly reduce time-consuming and expensive testing campaigns. © 2013 American Chemical Society.

To systematically investigate high-temperature corrosion of superheaters in biomass combined heat and power
(CHP) plants, a long-term test run (5 months) with online corrosion probes was performed in an Austrian CHP plant (28 MWNCV; steam parameters: 32 t/h at 480 °C and 63 bar) firing chemically untreated wood chips. Two corrosion probes were applied in parallel in the radiative section of the boiler at average flue gas temperatures of 880 and 780 °C using the steel 13CrMo4-5 for the measurements. Corrosion rates were determined for surface temperatures between 400 and 560 °C. The results show generally moderate corrosion rates and a clear dependence upon the flue gas temperatures and the surface temperatures of the corrosion probes, but no influence of the flue gas velocity has been observed. The data are to be used to create corrosion diagrams to determine maximum steam temperatures for superheaters in future plants, which are justifiable regarding the corrosion rate. Dedicated measurements were performed at the plant during the long-term corrosion probe test run to gain insight into the chemical environment of the corrosion probes. From fuel analyses, the molar 2S/Cl ratio was calculated with an average of 6.0, which indicates a low risk for high-temperature corrosion. Chemical analyses of aerosols sampled at the positions of the corrosion probes showed that no chlorine is present in condensed form at the positions investigated. Deposit probe measurements performed at the same positions and analyses of the deposits also showed only small amounts of chlorine in the deposits, mainly found at the leeward position of the probes. Subsequent to the test run, the corrosion probes have been investigated by means of scanning electron microscopy/energy-dispersive X-ray spectroscopy analyses. The results confirmed the deposit probe measurements and showed only minor Cl concentrations in the deposits and no Cl at the corrosion front. Because, in the case of Cl-catalyzed active oxidation, a layer of Cl is known to be found at the corrosion front, this mechanism is assumed to be not of relevance in the case at hand. Instead, elevated S concentrations were detected at the corrosion front, but the corrosion mechanism has not yet been clarified.

 Die Anzahl der installierten Biomasse-Kleinfeuerungsanlagen ist in letzter Zeit deutlich gestiegen. Aus diesem Grund ist es umso wichtiger eine schadstoffarme und effiziente Verbrennung zu ermöglichen. Genau diese Anforderung stellt jedoch eine große Herausforderung für deren Regelung dar. Der optimale Restsauerstoffgehalt des Rauchgases, im Sinne von niedrigen Kohlenmonoxidemissionen (CO-Emissionen) bei bestmöglichem Wirkungsgrad, ist sehr stark vom Betriebszustand, von der Anlagengeometrie und vom verwendeten Brennstoff abhängig. Diese Tatsache wird jedoch derzeit bei den Regelungen von Biomasse-Kleinfeuerungsanlagen nicht oder nur teilweise berücksichtigt. Um hohe CO-Emissionen aufgrund von Sauerstoffmangel in jedem Fall zu vermeiden, werden Biomasse-Kleinfeuerungsanlagen üblicherweise mit vergleichsweise hohem Sauerstoff betrieben. Diese Maßnahme geht jedoch mit einer unerwünschten Reduktion des Wirkungsgrades der Feuerung einher. Diese Arbeit hat zum Ziel eine Strategie zu entwickeln, welche das Luftverhältnis sowie auch die Luftstufung während des Betriebes dahingehend anpasst, dass stets ein möglichst effizienter und dennoch schadstoffarmer Betrieb gewährleistet wird. Die im Rahmen dieser Masterarbeit behandelten Arbeiten, wurden anhand einer handelsüblichen Biomasse-Kleinfeuerungsanlage durchgeführt. Die verwendete Anlage wird mit Hackgut betrieben und hat eine Kesselnennleistung von 30 kW. Für die Anwendung einer Strategie zur Reduktion der CO-Emissionen wäre es von großem Vorteil, wenn der CO-Gehalt des Rauchgases gemessen werden könnte. Derzeit gibt es jedoch nur sehr teure Rauchgasanalyseeinheiten, welche für eine dauerhafte Bestimmung des CO-Gehaltes des Rauchgases geeignet sind. Somit war bis jetzt eine Messung des CO-Gehalts nur bei großen Biomassefeuerungsanlagen wirtschaftlich. In dieser Arbeit wurde zunächst eine Marktanalyse zu preiswerten Sensoren zur Detektion unverbrannter Komponenten im Rauchgas durchgeführt. Es wurden ausschließlich Sensoren untersucht, die aufgrund ihres geringen Preises auch wirtschaftlich eingesetzt werden können. Dabei zeigte sich, dass es derzeit zwei Sensoren gibt, welche diese Anforderungen erfüllen. Diese Sensoren dienen jedoch lediglich zur Detektion von unverbrannten Komponenten im Rauchgas und sind nicht in der Lage den CO-Gehalt des Rauchgases exakt zu messen. Aus diesem Grund wurde der Zusammenhang zwischen CO-Konzentration und Sensorsignal untersucht und anschließend mathematisch beschrieben, wobei die wesentlichen Querempfindlichkeiten berücksichtigt wurden. Da die physikalischen Zusammenhänge sehr komplex und zu einem wesentlichen Teil nicht bekannt waren, wurde das mathematische Modell mit Hilfe der experimentellen Modellbildung ermittelt, wobei die verwendeten Messdaten einen möglichst großen Bereich der verschiedenen Einflussparameter beinhalteten. In weiterer Folge wurden umfassende Testläufe zur Untersuchung der Auswirkung der Leistung, des Luftverhältnisses im Brennstoffbett, des gesamten Luftverhältnisses und des Brennstoffwassergehaltes auf die CO-Emissionen durchgeführt. Die Ergebnisse zeigten, dass es für einen möglichst effizienten und gleichzeitig schadstoffarmen Betrieb notwendig ist, das Luftverhältnis im Brennstoffbett sowie den Sekundär"-luft"-massen"-strom in Abhängigkeit der geforderten Leistung zu variieren. Darauf aufbauend wurde eine geeignete Strategie zur Umsetzung dieser Maßnahmen entwickelt und implementiert. Dabei werden die Führungsgrößen für den Restsauerstoffgehalt sowie das Luftverhältnis im Brennstoffbett laufend an die geforderte Leistung angepasst. Zusätzlich dazu wird die Führungsgröße für den Restsauerstoffgehalt durch einen Suchalgorithmus zur Minimierung der CO-Emissionen variiert. Schlussendlich wurde die entwickelte Strategie mit Hilfe eines typischen Lastzyklus experimentell verifiziert. 

Ash components of biomass fuels can cause fouling, slagging, and bed material agglomeration during thermal utilization in fluidized bed combustion and gasification plants. The influence of ash components on these problems in dual fluidized bed biomass gasification plants is investigated in an industrial scale plant in Güssing, Austria. Samples of fouling are analyzed, and the results are evaluated. The samples were analyzed by X-ray fluorescence analysis and thermal analyses such as thermogravimetric analysis, differential thermal analysis, and differential scanning calorimetry. Mass balances of inorganic matter are presented, evaluating different loop configurations. The analyses showed high potassium contents compared to the fuel ash composition in fouling of up to 23% by weight. The potassium content of fly ash with a particle size smaller than 200 μm is half that of coarse fly ash with a particle size larger than 200 μm. The thermal analyses showed a large difference between samples of inorganic streams such as fly ash or fly char and fouling. Different fractions of fly ash samples (particle fraction smaller than 200 μm and particle fraction larger than 200 μm) showed similar thermal behavior: endothermic weight losses at around 400 C and around 720-820 C caused by decomposition of carbonates. The composition of inorganic matters of fly ash and fly char is similar. The elemental composition of deposits at the cyclone wall and the first heat exchanger in the flue gas path showed high potassium contents up to 23.6%. While samples of fly ash and fly char did not show significant melting in their thermal behavior, melting could be detected with fouling at temperatures higher than 1000 C. Mass balances of inorganic matter showed a flow of potassium oxide from the combustion reactor to the gasification reactor, which leads to unexpected high potassium concentrations in the fly char. A reduction of ash loops reduces the amount of potassium that is transferred from the combustion reactor to the gasification reactor. Recommendations are made for the operation of dual fluidized bed gasification plants in terms of ash handling to reduce tendencies for fouling, slagging, and bed material agglomeration. © 2013 American Chemical Society.

Several energy and agricultural commodities have experienced higher price volatility in recent years. Hence, the interest in food and energy security issues as well as price volatility has increased, particularly since the rise in food and energy commodity prices in 2007/2008. Volatility is associated with risk since higher price volatility leads to additional costs that are often shared and transmitted along the supply chain to the final consumers. Volatility of woody biomass prices is also possibly higher due to increased market dynamics and integration as well as renewable energy policy intervention. We compute historic price volatility using the standard deviation of log returns as well as univariate GARCH models and empirically analyze whether or not price volatility of woody biomass commodities has increased in recent years. We also compare the historic price volatility of woody biomass to the price volatility of agricultural commodities and fossil fuels. Results indicate that the price volatility of some woody biomass commodities has increased, but it is still lower than of agricultural biomass and fossil fuels.

In this paper the energy and carbon footprints of pellet imports from Australia, West Canada, and Russia for co-firing in Europe are investigated. Their ecologic and economic performances are proven by applying the Belgian and UK co-firing subsidy systems, which require dedicated sustainability evaluations. Based on the modelling of different subsidy schemes and price scenarios, the present paper identifies favourable conditions for the use of biomass co-firing in Germany and Austria, which currently do not have dedicated co-firing incentives. The present paper shows that under present conditions, co-firing has a narrow financial gap to coal with -3 to 4€ Cent/kWh_el and has low CO₂ mitigation costs compared to other renewables. Moreover, it is shown that co-firing is one of the most cost-attractive options to reach the EU-2020 targets. For policy makers, the support of co-firing is found to be very efficient in terms of cost-benefit ratio. It is proven that the co-firing subsidy schemes might direct supply chain decisions towards options with low energy and carbon impacts. © 2013 Elsevier Ltd.
 

Co-gasification of biomass and plastics was investigated in a 100 kW dual fluidized-bed pilot plant using four types of plastic material of different origins and soft wood pellets. The proportion of plastics was varied within a broad range to assess the interaction of the materials. The product gas composition was considerably influenced by co-gasification, whereas the changes were nonlinear. More CO and CO₂ were measured in the product gas from co-gasification than would be expected from linear interpolation of mono-gasification of the materials. Less CH₄ and C₂H ₄ were formed, and the tar content in the product gas was considerably lower than presumed. With the generation of more product gas than expected, co-gasification of wood and plastic materials also had other beneficial effects. Because of the fuel mixtures, more radicals of different types were available that interacted with each other and with the fluidization steam, enhancing the reforming reactions. Wood char had a positive effect on polymer decomposition, steam reforming, and tar reduction. As a result of the more active splash zone during co-gasification of wood and plastics, contact between gas and bed material was enhanced, which is crucial for catalytic tar removal. © 2013 American Chemical Society.