Batch-wise operated wood stoves for room heating purposes are popular and widespread in Europe. Beside economic and ecological reasons they are also very important for reaching the European CO2 emission targets. However, since they contribute significantly to harmful gaseous as well as particulate emissions, they have to be optimized towards clear emission reduction in real life operation. Catalysts integrated in wood stoves can significantly contribute to reach this target. The results of this study showed an emission reduction potential of
integrated ceramic and metallic honeycomb catalysts of around 30 % to 99 %. Thereby the highest reduction potential was investigated for CO emissions (reduction rate 75 % to 99 %), followed by reductions of VOC emissions (reduction rate 40 % to 60 %) and reductions of PM emissions of around 30 % to 40 %. Long term tests and safety test series lead to the conclusion that integrated catalysts have to be cleaned regularly in order to prevent blocking and to guarantee optimal reduction performance.

A widely applicable kinetic scheme for pyrolysis is still missing. In this work an adaptation of the mechanistic scheme developed by Ranzi et al. (2008) for pyrolysis of small ash free biomass particles is proposed. The scheme is modified to include secondary char formation reactions, which are relevant for particles of a certain thickness, and sugar formation is avoided due to the catalytic effect of alkali metals in biomass. The predictions of the adapted scheme are compared to experimental data from the literature of pyrolysis in fixed beds of particles with a size of around 1 cm. It is shown that the adaptation improves the prediction of the final char yield and its CHO composition and also the yields of the main groups of volatiles, as carbonyls + alcohols, sugars and water vapor. © 2014 Elsevier Ltd. All rights reserved.

A kinetic scheme for the prediction of product composition of torrefaction is presented in this work. The scheme is based on a pyrolysis scheme for fast pyrolysis of small ash free biomass particles and was adapted to consider the presence of secondary char formation reactions, the inhibition of sugar formation due to the catalytic effect of alkali metals in biomass, as well as the typical hemicellulose structure of hardwoods. The torrgas composition predicted by the model is compared to experimental data of torrefaction in a lab-scale packed bed reactor. It is shown that the adapted model is able to predict the yields of the main volatile groups, i.e., permanent gases, light and heavy condensable species and the yields of the several groups in which condensable species were classified based on their structure, i.e., carbonyls and alcohols, furans, phenolics as well as water vapour. Copyright © 2014,AIDIC Servizi S.r.l.

To influence the combustion process of modern biomass furnaces specifically the combustion-controller determines the necessary mass flows. The gaseous mass flows can be adjusted by fans and flaps. To ensure the desired overall performance of the furnace the mass flows need to be set by inner control loops respectively. Within the work described in this paper a model based approach for the control design of the inner control loop is presented exemplarily for the secondary air supply. Thereby a flatness-based feedforward control will be designed by means of an appropriate model. © 2014 Oldenbourg Wissenschaftsverlag GmbH.

Die vorliegende Arbeit widmet sich der Herleitung mathematischer Simulationsmodelle eines Pufferspeichers, eines Solarkollektors sowie eines Plattenwärmeübertragers. Dabei wird das Simulationsmodell des Pufferspeichers anhand eines am Markt verfügbaren Pufferspeichers entwickelt. Die mathematischen Beschreibungen der Simulationsmodelle basieren auf einer partiellen Differentialgleichung zur Beschreibung der Wärmeübertragung in einem durchströmten zylindrischen Rohr. Nach dem Erhalt der mathematischen Modelle werden diese mit einem impliziten Lösungsverfahren numerisch gelöst. Anschließend werden die experimentell zu ermittelnden Parameter des Pufferspeichermodells anhand gezielt durchgeführter Versuche bestimmt. Nach dem Ermitteln der Parameter wird das Simulationsmodell des Pufferspeichers mit einem weiteren Versuch experimentell verifiziert. Schlussendlich bildet das mathematische Modell des Pufferspeichers den untersuchten Pufferspeicher sehr zufriedenstellend ab, womit ein Simulationsmodell vorliegt, das gezielte Untersuchungen ohne aufwändige Versuche ermöglicht. Abschließend wird eine Regelung für die Wärmeübertragung aus dem Solarkollektor in den Pufferspeicher entwickelt. Dabei werden zwei in der Praxis übliche Verfahren untersucht. Bei der ersten Variante erfolgt die Übertragung der Wärme in den Pufferspeicher über ein im Pufferspeicher integriertes Solarregister. Bei der zweiten Variante erfolgt die Übertragung der Wärme über einen Plattenwärmeübertrager vom Wasser-Frostschutzgemisch auf Wasser, welches dann direkt in den Pufferspeicher eingespeist wird. Als Reglerstruktur wird in beiden Fällen ein Standard-Regelkreis mit einer statischen Vorsteuerung verwendet. Anhand von Simulationsstudien werden zunächst die Parameter des PI-Reglers festgelegt und in weiterer Folge die mit der jeweiligen Variante resultierenden Temperaturverläufe des Wassers im Pufferspeicher untersucht und gegenübergestellt. Dabei stellt sich heraus, dass die Temperatur des Wassers im Pufferspeicher, bei gleich bleibender Strahlungsstromdichte der Solarstrahlung Igauf den Solarkollektor, die gewünschte Solltemperatur bei Wärmeübertragung mittels Plattenwärmeübertrager schneller erreicht, als bei Wärmeübertragung durch das Solarregister. Darüber hinaus ermöglicht die Verwendung des Plattenwärmeübertragers eine Schichtung der Temperatur des Wassers im Pufferspeicher und somit eine Speicherung der Wärme auf einen höheren Temperaturniveau.

A transient 3D model for two main zones, namely the fuel bed and the freeboard, of biomass packed bed combustion systems was developed. It integrates the models for the biomass conversion sub-processes and solves the governing equations for the gas and solid phase and their interactions. The intra-particle gradients are included by considering the biomass particles as thermally thick particles. The shrinkage of the packed bed and the variations of the bed porosity due to the uneven consumption of the fuel are taken into account. Detailed kinetic mechanisms are used for the simulation of homogeneous gas phase reactions. To verify the model and to increase the understanding of packed bed combustion, laboratory-scale fixed-bed batch experiments have been performed in a reactor with 9.5 cm diameter and 10 cm length. The model performance was extensively validated with gas phase measurements (CO, CO₂, CH₄, H₂, H₂O and O₂) above the fuel bed, temperatures at different heights in the bed and in the freeboard, and the propagation rate of reaction front. The simulation results are in a good agreement with the measured values. © 2014 Elsevier Ltd. All rights reserved.

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.

Biodiesel (rapeseed oil methyl ester) was aged in a Rancimat device at a temperature of 110°C and an air flow of 10 L/h. Time-resolved analyses applying gas chromatography-flame ionization detection, gas chromatography-mass spectrometry, and ion-exchange chromatography on the formation of aging products were performed. Formic and acetic acid, fatty acids with chain lengths from 5 to 18 carbon atoms, fatty acid methyl esters, and epoxides were quantified. After 12 h of aging, the concentrations of formic and acetic acid were 5600 ± 80 and 1360 ± 80 mg/kg, respectively. Fatty acid concentrations were in the range of <18-4200 mg/kg after 18 h of aging. Linoleic acid methyl ester and linolenic acid methyl ester (19 and 9.1 mass % of the non-aged fuel) were shown to be fully decomposed after 24 and 18 h of aging, respectively. After 51 h of aging, the concentration of oleic acid methyl ester (63 mass % of the non-aged fuel) decreased to 2.2 mass % and trans-epoxy stearic acid methyl ester and cis-epoxy stearic acid methyl ester reached concetrations of 5.9 and 0.7 mass %, respectively. The fuel composition shows only minor changes in early stages of aging, and a strong timely correlation of the formation of aging products with the end of the induction period of fuel was observed. © 2014 American Chemical Society.

Anaerobic digestion (AD) of sugar beet pressed pulp (SBPP) is a promising treatment concept. It produces biogas as a renewable energy source making sugar production more energy efficient and it turns SBPP from a residue into a valuable resource. In this study one- and two-stage mono fermentation at mesophilic conditions in a continuous stirred tank reactor were compared. Also the optimal incubation temperature for the pre-acidification stage was studied. The fastest pre-acidification, with a hydraulic retention time (HRT) of 4 days, occurred at a temperature of 55 °C. In the methanogenic reactor of the two-stage system stable fermentation at loading rate of 7 kg VS/m³ d was demonstrated. No artificial pH adjustment was necessary to maintain optimum levels in both the pre-acidification and the methanogenic reactor. The total HRT of the two-stage AD was 36 days which is considerably lower compared to the one-stage AD (50 days). The frequently observed problem of foaming at high loading rates was less severe in the two-stage reactor. Moreover the viscosity of digestate in the methanogenic stage of the two-stage fermentation was in average tenfold lower than in the one-stage fermentation. This decreases the energy input for the reactor stirring about 80 %. The observed advantages make the two-stage process economically attractive, despite higher investments for a two reactor system. © 2013 Springer Science+Business Media Dordrecht.