The wood fuel market is connected to the forest­based industry in various ways: the sawmill by­ products such as sawdust and wood chips are usually used as raw material in the panel, pulp and paper industry and are increasingly pelletized to supply the energy commodity market. Hence, the question arises whether or not prices of these woody biomass commodities are integrated. Threshold cointegration and asymmetric error correction models are used to analyze the price dynamics between roundwood, wood pellets and sawmill by­ products. Results indicate that a statistical significant price transmission between sawmill by­products and wood pellets, but wood pellet and roundwood prices are not integrated. The price transmission between wood pellets and sawdust as well as wood chips is asymmetric. The Granger Causality test reveals that the prices of sawdust and wood chips depend on the price of wood pellets.

ie Biomasseverbrennung spielt eine zentrale Rolle bei der Bereitstellung von Wärme aus erneuerbaren Energieträgern. Konventionelle Biomasse-Brennstoffe werden jedoch aufgrund einer steigenden Anzahl stofflicher Verwertungsmöglichkeiten, wie z.B. der Umwandlung in Chemikalien, teurer und schwieriger zugänglich. Agrarbrennstoffe, die bisher nur selten oder gar nicht in Biomasse-Kleinfeuerungen eingesetzt wurden, stellen eine vielversprechende Alternative zu konventionellen Brennstoffen dar. Diese Agrarbrennstoffe, wie zum Beispiel Kurzumtrieb, Maisspindeln oder Stroh sind kostengünstig und in ausreichender Menge vorhanden. Der Einsatz von Agrarbrennstoffen in konventionellen Biomasse-Kleinfeuerungen ist jedoch aufgrund stark variierender Brennstoffeigenschaften mit erhöhten Anforderungen an das Verbrennungssystem verbunden. Erhöhte N, S, Cl, Alkalimetall- und Aschegehalte sowie niedrigere Aschenschmelzpunkte können zu aschebedingten Problemen (Ascheschmelze, Ascheablagerung und Korrosion) sowie erhöhten Konzentrationen von gasförmigen (CO, NOx, HCl und SOx) und partikelförmigen Emissionen bei der Verbrennung führen.

Ziel der in diesem Beitrag präsentierten Arbeiten war die Erhöhung die Brennstoffflexibilität einer handelsüblichen Biomasse-Kleinfeuerung um damit eine Verbrennung von Agrarbrennstoffen mit niedrigen Schadstoffemissionen und einem hohen Wirkungsgrad zu ermöglichen. Hierzu wurde eine modellbasierte Regelung entwickelt, welche insbesondere eine gezielte Einstellung des Luftverhältnisses in der Primärverbrennungszone ermöglicht und damit das Risiko der Ascheschmelze reduziert und Schadstoffmissionen verringert. Soft-Sensoren bestimmen relevante Brennstoffeigenschaften während des Betriebs, welche von der modellbasierten Regelung zur automatischen Anpassung an geänderte Brennstoffeigenschaften genutzt werden. Die modellbasierte Regelung wurde um eine CO-lambda-Optimierung ergänzt, welche auf Basis von Messwerten des Restsauerstoffgehalts und der CO-Emissionen den Wirkungsgrad der Verbrennung maximiert und gleichzeitig die Schadstoffemissionen verringert. Zur weiteren Verringerung von partikelförmigen Schadstoffemissionen wurde ein am Markt verfügbarer Elektrofilter adaptiert und nach dem Wärmeübertrager der Biomasse-Kleinfeuerung angebracht.

Dieses Verbrennungssystem wurde durch umfassende Testläufe mit begleitenden Emissionsmessungen sowie Brennstoff-, Staub- und Ascheanalysen bewertet. Der Einsatz der modellbasierten Regelung führte zu einem stabileren Betrieb bei allen Leistungen und für alle Brennstoffe. Der Elektrofilter zeigte sehr zufriedenstellende Abscheidegrade für alle untersuchten Brennstoffe und Anlagenleistungen. Dadurch konnte die Brennstoffflexibilität der handelsüblichen Biomasse-Kleinfeuerung erhöht und die Verbrennung von Agrarbrennstoffen ermöglicht werden.

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.

In cooperation between Vienna University of Technology and Bioenergy 2020+ a project was done which had the objective to evaluate the prospects for the production of Biofuels by integration in existing Austrian biomass industry. The advantages of such integration are the good access to renewable energy resources like wood chips, existing infrastructure for electricity and heat, existing logistics of resources and the utilization of waste heat from Biofuel production to substitute fossil fuels. One work package included the process simulation of thermo-chemical biomass gasification and the production of a second generation Biofuel by the use of Fischer – Tropsch (FT) - synthesis. The process simulation tool IPSEpro was used for the simulation. The simulation of technical processes allows the prediction of the behavior of processes on the base of mathematical models. The quality of a simulation model depends substantially on the used model and the process parameters. The used technologies in the process simulation were the biomass gasification with the Fast Internal Circulating Fluidized Bed (FICFB) – gasification system and the Fischer –Tropsch (FT) - synthesis. The FICFB was developed by the Vienna University of technology. This gasification technology is used in the well known demonstration plant is Güssing (Austria). The produced product gas is nearly nitrogen free and has a high content of hydrogen (45 – 35 Vol%_dry) and carbon monoxide (25 – 20 Vol%_dry). These product gas components are used in the FT - synthesis for the production of FT – raw product. A FT - Trial Plant is also situated in Güssing since the year 2005. A slurry reactor is used in the Trial Plant for the FT – synthesis. The target for the simulation was the production of FT – raw product as well as the substitution of fossil fuels. The waste heat of the process should be used for the production of steam. An amount of 120 tons per hour of fossil produced steam should be substituted. The
Off-Gas of the FT – process was also used for the production of steam. Two different models for location number one were considered. The used fuel was wood chips. The data out of the simulation were used to calculate the economic efficiency of the plants. An important parameter was the price of the FT – raw product per liter. The total costs and the production capacity were set equal to calculate the marginal revenue. Also a sensitivity analysis was done to evaluate the effects of rising fuel costs and increased investment costs.

Energy systems have increased in complexity in the past years due to the everincreasing integration of intermittent renewable energy sources such as solar thermal or wind power. Modern energy systems comprise different energy domains such as electrical power, heating and cooling which renders their control even more challenging. Employing supervisory controllers, so-called energy management systems (EMSs), can help to handle this complexity and to ensure the energy-efficient and cost-efficient operation of the energy system. One promising approach are optimization-based EMS, which can for example be modelled as stochastic mixed-integer linear programmes (SMILP). Depending on the problem size and control horizon, obtaining solutions for these in real-time is a difficult task. The progressive hedging (PH) algorithm is a practical way for splitting a large problem into smaller subproblems and solving them iteratively, thus possibly reducing the solving time considerably. The idea of the PH algorithm is to aggregate the solutions of subproblems, where artificial costs have been added. These added costs enforce that the aggregated solutions become non-anticipative and
are updated in every iteration of the algorithm. The algorithm is relatively simple to implement in practice, re-using almost all of a possibly existing deterministic implementations and can be easily parallelized.
Although it has no convergence guarantees in the mixed-integer linear case, it can nevertheless be used as a good heuristic for SMILPs. Recent theoretical results shown that for applying augmented Lagrangian functions in the context of mixed-integer programmes, any norm proofs to be a valid penalty function. This is not true for squared norms, like the squared L 2 -norm that is used in the classical progressive hedging algorithm. Building on these theoretical results, the use of the L 1 and L-infinity-norm in the PH algorithm is investigated in this paper. In order to incorporate these into the algorithm an adapted multiplier update step is proposed. Additionally a heuristic extension of the aggregation step and an adaptive penalty parameter update scheme from the literature is investigated. The advantages of the proposed modifications are demonstrated by means of illustrative examples, with the application to SMILP-based EMS in mind.

A mathematical model is developed to simulate synthesis gas production by methane steam reforming process in a fixed bed reactor filled with catalyst particles. Due to the endothermic nature of the reforming reactions heat is supplied into the reactor by means of electrical heating, therefore, the reactor and catalyst particles are exposed to significant axial and radial temperature gradients. A pseudo heterogeneous model is used in order to exactly represent diffusion phenomena inside the reactor tube. Heat and mass transfer equations are coupled with detailed reaction mechanisms and solved for both the flow phase and within the catalyst pellets. The reaction has been investigated from a modeling view point considering the effect of different temperatures ranging from 873 to 1073 (K) on methane conversion and hydrogen yields. The result provides temperature and concentration distribution along the reactor axial and radial coordinates and strong radial temperature gradients particularly close to the entrance of the reactor have been found. © 2013 Elsevier B.V.

Current levels of ambient air fine particulate matter (PM_2.5) are associated with mortality and morbidity in urban populations worldwide. In residential areas wood combustion is one of the main sources of PM_2.5 emissions, especially during wintertime. However, the adverse health effects of particulate emissions from the modern heating appliances and fuels are poorly known. In this study, health related toxicological properties of PM₁ emissions from five modern and two old technology appliances were examined. The PM₁ samples were collected by using a Dekati® Gravimetric Impactor (DGI). The collected samples were weighed and extracted with methanol for chemical and toxicological analyses. Healthy C57BL/6J mice were intratracheally exposed to a single dose of 1, 3, 10 or 15mg/kg of the particulate samples for 4, 18 or 24h. Thereafter, the lungs were lavaged and bronchoalveolar lavage fluid (BALF) was assayed for indicators of inflammation, cytotoxicity and genotoxicity. Lungs of 24h exposed mice were collected for inspection of pulmonary tissue damage. There were substantial differences in the combustion qualities of old and modern technology appliances. Modern technology appliances had the lowest PM₁ (mg/MJ) emissions, but they induced the highest inflammatory, cytotoxic and genotoxic activities. In contrast, old technology appliances had clearly the highest PM₁ (mg/MJ) emissions, but their effect in the mouse lungs were the lowest. Increased inflammatory activity was associated with ash related components of the emissions, whereas high PAH concentrations were correlating with the smallest detected responses, possibly due to their immunosuppressive effect. © 2012 Elsevier B.V.

Glycerol is a co-product compound of biodiesel production with an interesting heating value. In this work pyrolysis kinetic parameters for a pellet made with a mass fraction of 90% sawdust and a mass fraction of 10% glycerol are derived through thermogravimetric analysis. A new parallel reaction scheme with four components (cellulose, hemicellulose, lignin and glycerol) is adopted and the kinetic triplet for each component is derived using a model fitting approach applied to this particular kind of pellet. The isoconversional method Kissinger-Akahira-Sunose is employed both to provide initial values for model fitting simulations and to check final results. Results show that activation energies and pre-exponential factors are respectively: 149.7 kJ mol⁻¹ and 1.98*10¹¹ s⁻¹ for hemicellulose, 230.1 kJ mol⁻¹ and 1.84*10¹⁷ s⁻¹ for cellulose, 154.3 kJ mol⁻¹ and 5.14*10⁹ s⁻¹ for lignin, 74.5 kJ mol⁻¹ and 2.17*10⁵ s⁻¹ for glycerol with a first reaction order for all components, except for lignin (n = 2.6). Through evolved gas analysis it was demonstrated that the thermal degradation of glycerol contained in the pellet can increase hydrogen content in pyrolysis gases.

In the presented work the fuel quality and basic data about production processes of wood pellets from
all over Europe are investigated. For this purpose pellets producers were interviewed and fuel samples were analysed. Information from 91 companies was evaluated, covering about 50% of the European pellets production capacity, and pellets samples of 51 companies from 18 different countries were examined. It was found, that the raw material for pellets production is mainly taken from local resources. 75% of the plants process soft wood, whereas the use of hard wood is more common in Eastern Europe, Italy, Spain and France. Regarding the fuel properties of the pellets, differences were mainly found with regard to ash content and mechanical durability. In spite of these strong variations, almost all samples fulfilled the requirements according to the respective quality standard declared, and a clear correlation of valid standards and available pellets qualities was observed.