Since batch-wise operated biomass roomheaters are claimed to cause high amounts of gaseous and particulate emissions effective measures for a reduction of these emissions especially in real life operation have to be implemented in the future. For a verification of the real life operation performance as well as for a better product differentiation of biomass room heating appliances on the market advanced testing methods will be necessary in the future. Therefore a new test method for roomheaters called “Stove Testing 2020” (ST2020) was developed. According to the new test method the emission and efficiency performance of roomheaters is determined under operating conditions that are closer to real life. Compared to the existing EN 13240 standard also transient combustion phases are included. For a final evaluation of the test method the reproducibility as well as the real life relevance was analysed by a Round-Robin-Test as well as by field tests. The results showed sufficient reproducibility as well as a high real life relevance of the ST2020 test method. However, due to the strong impact of user behavior on emission and efficiency performance in real life operation further technological improvements of biomass roomheaters have to be strongly supported by effective measures to guarantee a correct operation.

State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the “porous” nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kW_th) concerning the simulation of gas phase combustion and NO_x formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NO_x reduction by primary measures.

Microalgae are seen worldwide as a new and promising feedstock for the energy supply chain.
Because of their high productivity and their ability to convert CO2 into biomass, microalgae are a
potential raw material for biorefineries, avoiding the food versus fuel conflict, and contributing to an
increased share of renewable energy. According to the current state of the art the utilization of algal
biomass for the production of fuel, energy and heat seems to be economically not competitive and the
life cycle assessment shows improvement possibilities in energy consumption (project
Algae&Energy:Austria). There are different options for utilization concepts which are technologically
and economically feasible. New concepts need to be developed and synergies with already existing
technologies need to be used.
Challenges along the value chain:
· Supply of water for cultivation
· Supply of nutrients for cultivation
· Energy consumption during cultivation
· Harvesting and processing of biomass
· Investment and operating costs
One possibility to cover the need of water and nutrients in a cost-effective way is the combination of
microalgae cultivation and waste water treatment. The cultivation of algae using different waste water
types common in Austria is technologically possible. In particular municipal waste water and effluents
from breweries and dairies are suitable as substrate. Due to the usage of this synergy the need for
fresh water and artificial fertilizer for algae cultivation decreases substantially and therefore operating
costs are reduced. Promising production concepts were developed and further research and
development needs were pointed out (project SAM).
After producing algal biomass the harvesting and processing steps for further utilization seem to be
difficult. In particular the high amount of water increases the energy expenditure in most of the
conversion pathways. Hydrothermal liquefaction seems to be promising to reduce the energy intensity
through two major factors: First, the conversion takes place in the liquid phase, and no energy
intensive drying of the algal biomass is needed. Second, the entire carbon which is fixed in the algae
can be used for energy production. The main product of hydrothermal liquefaction is a bio-oil, which
can be further processed in existing refinery processes into biogenic motor fuels, plastics and basic
chemicals (project microHTL).
In Austria many scientific research groups and companies are dealing with microalgae in the energy
system. These research and development efforts comprise different topics and approaches, like
different cultivation system designs (open pond, photobioreactor), biotechnological optimization of
microalgae species, the utilization of algal biomass in energetic and material pathways or the
combination of microalgae cultivation with existing technologies. It is of growing importance to
establish a network of Austrian experts and research groups for enhancement of cooperation and
research within the field of algae (project network biobased industry).
Through the optimization along the entire value chain with special regard to novel concepts of
cultivation, harvesting, processing, conversion and utilization, as well as an enhanced network of
Austrian experts and research groups, microalgae can serve as biogenic feedstock for the energy

In Güssing a nearly nitrogen free product gas can be provided by the Fast Internal Circulating Fluidized Bed (FICFB) – gasification system. The main components of the product gas are hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4). A Fischer – Tropsch (FT-) trial plant uses the product gas components H2 and CO in an exothermic, catalytic reaction to produce hydrocarbon chains. Catalysts based on iron and cobalt are used for the synthesis. In Güssing a slurry reactor is used for low temperature FT – synthesis. The main parts of the plant are the gas cleaning section, the gas compression section, the FT – slurry reactor and the product separation section. In the year 2008 eight experiments with a catalyst based on iron and from April to July 2009 ten experiments with a catalyst based on cobalt were done. Over 1400 operating hours were reached and approximately 170 kg of FT – raw product was produced. The product of the experiments with cobalt catalyst was split into the fractions naphtha, diesel and waxes by vacuum distillation. The long chain waxes of the distillation were used in a hydro – treater to convert them to diesel.

The interest in microalgae products has been increasing, and therefore the cultivation industry is growing steadily. To reduce the environmental impact and production costs arising from nutrients, research needs to find alternatives to the currently used artificial nutrients. Microalgae cultivation in anaerobic effluents (more specifically, digestate) represents a promising strategy for increasing sustainability and obtaining valuable products. However, digestate must be processed prior to its use as nutrient source. Depending on its composition, different methods are suitable for removing solids (e.g., centrifugation) and adjusting nutrient concentrations and ratios (e.g., dilution, ammonia stripping). Moreover, the resulting cultivation medium must be light-permeable. Various studies show that growth rates comparable to those in artificial media can be achieved when proper digestate treatment is used. The necessary steps for obtaining a suitable cultivation medium also depend on the microalgae species to be cultivated. Concerning the application of the biomass, legal aspects and impurities originating from digestate must be considered. Furthermore, microalgae species and their application fields are essential criteria when selecting downstream processing methods (harvest, disintegration, dehydration, product purification). Microalgae grown on digestate can be used to produce various products (e.g., bioenergy, animal feed, bioplastics, and biofertilizers). This review gives insight into the origin and composition of digestate, processing options to meet requirements for microalgae cultivation and challenges regarding downstream processing and products.

Efficient control of energy systems is an important factor in achieving the CO2-emission goals. District heating (DH) networks are an especially relevant example of such energy systems. State-of-the-art control of small and medium-sized DH networks, however, still mainly relies on simple rule-based control concepts. Handling future challenges such as varying prices and intermittent renewable production is difficult to achieve with such control concepts. Optimization-based energy management systems (EMS) are a promising high-level control approach for the efficient operation of DH networks and complex energy systems in general. An especially interesting challenge arises when DH networks grow, as often the opportunity arises to interconnect them. However, if they operated by different owners, the control task becomes challenging, especially for optimization-based EMS. This is because, in the overall objective function, the cost and revenue for any exchange of energy would cancel out. This thesis presents a solution to this challenge. The main focus of this thesis is on the application of distributed optimization methods for EMS in the context of coupled energy systems, operated by multiple owners, especially interconnected DH networks. The presented methods and ideas are evaluated on a practical application of three DH networks in Austria.  

Annex TS3: Hybrid Energy Networks

The aim of the IEA DHC Annex TS3 „hybrid energy networks" is to promote opportunities and to overcome challenges for district heating and cooling (DHC) networks in an integrated energy system context, focusing on the coupling to the electricity and the gas grid.

Ash related problems such as slagging, fouling, and high temperature corrosion in biomass fired boilers are still insufficiently explored due to the complexity of the underlying processes. High temperature corrosion of low alloy steels like 13CrMo4-5 has already been investigated in plants firing chemically untreated wood chips. In this earlier work it has been suggested that the oxidation of the steel is the dominating mechanism in the material temperature range between 450 and 550 °C. Unfortunately the exponential dependence of the material degradation on the flue gas temperature also found within this work cannot be explained with the proposed corrosion mechanism. To determine the dominating corrosion mechanism, additionally test runs have been carried out in a specially designed drop tube reactor. To investigate the time-dependent corrosion behavior of 13CrMo4-5, a newly developed mass loss probe was applied under several constant parameter setups. In addition to these measurements, the time-dependent oxidation of 13CrMo4-5 under air was investigated in a muffle furnace. To gain relevant information regarding the corrosion mechanism prevailing, the deposits as well as the corrosion products have been examined subsequently to the test runs by means of scanning electron microscopy and energy dispersive X-ray analyses. With the experimental data gained it could be shown that the dominating corrosion mechanism strongly depends on the conditions prevailing (e.g., steel temperature, flue gas temperature, and velocity) and can either be the oxidation of the steel by gaseous O₂ and H₂O or a combination of oxidation and active Cl-induced oxidation.

Climate change affects the frequency and intensity of extreme weather, the results of which include production losses and climate-induced crop productivity fluctuations.

Double-cropping systems (DCSs) have been suggested as a way to increase biomass-production while simultaneously delivering environmental benefits. In a three-year field-test, two DCSs based on maize and sorghum as the main crop and rye as the preceding winter crop were compared with each other and compared with 2 single-cropping systems (SCSs) of maize or sorghum; there were comparisons of growth dynamics, optimal harvesting and growing time as well as biomass and methane yield. In addition, the impact of variety and harvest time on the winter rye optimal biomass yield was studied.

The experiments clearly showed the superiority of the DCS over the SCS. Within the DCS, the rye/sorghum combination achieved significantly higher biomass yields compared to those of the rye/maize combination. The highest dry matter biomass yield was achieved during year 1 at 27.5 ± 2.4 t∙ha−1, during which winter rye contributed 8.3 ± 0.7 t∙ha−1 and sorghum contributed 19.2 ± 1.8 t∙ha−1. At the experimental location, which is influenced by a Pannonia climate (hot and dry), the rye/sorghum DCS was able to obtain average methane yields per hectare, 9300 m3, whereas the rye/maize combination reached 7400 m3. In contrast, the rye, maize and sorghum SCSs achieved methane yields of 4800, 6100 and 6500 m3 ha−1, respectively. The study revealed that the winter rye and sorghum DCS is a promising strategy to counteract climate change and thus guarantee crop yield stability.

Ample interest for more efficient utilization of bio-based residues has emerged in the Nordic pulp and paper (P&P) industry, which uses virgin wood as feedstock. Although different bioenergy retrofit technologies for production of liquid, solid, and gaseous bioenergy products have been applied in the existing P&P mills, the number of installations remains small. The lack of profound knowledge of existing bioenergy retrofits hinders the replication and market uptake of potential technologies. This review synthesises the existing knowledge of European installations and identifies the key drivers and barriers for implementation to foster the market uptake of potential technologies. The bioenergy retrofits were reviewed in terms of technical maturity, drivers, barriers and market potential. Based on this evaluation, common drivers and barriers towards wider market uptake were outlined from political, economic, social, technical, environmental, and legal perspective. Technologies already commercially applied include anaerobic fermentation of sludge, bark gasification, tall oil diesel and bioethanol production, whereas lignin extraction, biomethanol production, hydrothermal liquefaction and hydrothermal carbonization are being demonstrated or first applications are under construction. The findings of this review show that a stable flow of residues at P&P mills creates a solid base for retrofitting. New innovative bio-based products would allow widening the companies' product portfolios and creating new businesses. Also, European Union's (EU) legislation drives towards advanced biofuels production. Wider uptake of the retrofitting technologies requires overcoming the barriers related to uncertainty of economic feasibility and unestablished markets for new products rather than technical immaturity. 

Absorptionskälteanlagen können einen wesentlichen Beitrag zur Verringerung von CO2-Emissionen leisten, wenn Wärme aus regenerativen Energieträgern oder Abwärme aus industriellen Prozessen zum Antrieb verwendet wird. Absorptionskälteanlagen weisen bereits jetzt eine hohe Effizienz auf, bei veränderlichen Betriebsbedingungen kann diese je nach vorhandenen Stellgliedern weiter gesteigert werden. Dazu werden im Rahmen des Forschungsprojektes „Heat Pumping Systems Control (HPC)“ zwei Absorptionskälteanlagen – eine mit der Stoffpaarung Ammoniak/Wasser (NH3/H2O) und eine mit der Stoffpaarung Wasser/Lithiumbromid (H2O/LiBr) – untersucht, um für unterschiedliche Anwendungen optimale Betriebsstrategien zu entwickeln. Zur Berücksichtigung der Zustandsänderungen in der Absorptionskälteanlage, werden dynamische Simulationsmodelle in der Modellierungssprache Modelica entwickelt und mit Messdaten validiert.

Im Rahmen dieses Konferenzbeitrags werden Komponentenmodelle für die NH3/H2O-Absorptionskälteanlage und Simulationsrechnungen bei veränderlichen Randbedingungen präsentiert, sowie ein Vergleich mit Messdaten diskutiert.

K-feldspar was utilized as bed material for fluidized bed combustion of bark, chicken manure, and their mixture. Bed samples were extracted after 4 and 8 h and the samples were analyzed with scanning electron microscopy to study the impact of P-rich chicken manure on the bed material. The results were compared to fixed bed exposures with different orthophosphates to investigate their influence in detail.

The fresh bed material used for this study exhibited an uneven surface with many cavities which facilitated the deposition and retention of the fuel ash. Utilizing pure chicken manure as fuel led to the formation of Ca- and P-rich particles which accumulated in these cavities. At the same time, larger ash particles were formed which consisted of the elements found in chicken manure ash. The co-combustion of bark and chicken manure led to the interaction of the two ash fractions and the formation of a thicker ash layer, which consisted of elements from both fuel ashes, namely Ca, P, Si, K and S. The layer appeared to be partially molten which could be favorable for the deposition of ash particles and thereby the formation of a mixed Ca/K-phosphate. Fixed bed exposures of the K-feldspar particles with Na3PO4 or K3PO4 caused particle agglomeration which means presence of alkali-phosphates should be limited.

The co-combustion of bark with chicken manure showed promising results both regarding a shift from Ca-phosphates to more bioavailable Ca/K-phosphates and an acceleration in ash layer formation. The formation of an ash layer after only 4 h of exposure with the mixture of bark and chicken manure could be advantageous for catalytic activation of the bed material.

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.

Biomass upgrading through torrefaction is expected to relevantly reduce biomass trade costs and thus energy costs for the end-user. In this framework, the present work aims at defining crucial technical and cost parameters for the production, fuel properties, supply and end-use of torrefied pellets. The findings are used to compare four real-case wood pellet with corresponding torrefied pellet supply chains. Input data are derived from laboratory fuel, pelletising and storage experiments with torrefied biomass provided from European producers, cost estimations based on experience from related technology engineering and set-up as well as from expert consultations. This allows a step-by-step comparison of cost advantages and additional expenses from pretreatment to end-user. As a result, torrefied pellets turn out to be a certain alternative for wood pellets. The cost comparison demonstrates that the production of torrefied pellets is still much more cost-intensive, but can be partly compensated by reduced transportation costs. At the end-user, heat production in small-scale pellet boilers is technically feasible, but with slightly higher costs. Co-firing torrefied pellets in large-scale coal plants can be cost-competitive to industrial wood pellets, when no additional retrofit and operation and maintenance costs incur.

Gasification is a thermochemical process that transforms carbonaceous matter into a gaseous secondary energy carrier, referred to as product gas. This product gas can be used for heat and power generation but also for syntheses. One possible gasification technology suitable for further synthesis is dual fluidised bed (DFB) steam gasification. The H2:CO ratio, which determines the suitability of the product gas for further synthesis, is influenced by the catalytic activity inside the gasification reactor. Eleven DFB steam gasification experiments were performed comparing the catalytic activity for various bed material and fuel combinations. The bed materials used were K-feldspar, fresh and layered olivine, and limestone, and the fuels gasified were softwood, chicken manure, a bark–chicken manure mixture and a bark-straw-chicken manure mixture. The water-gas-shift (WGS) equilibrium deviation was used to evaluate the catalytic activity inside the gasification reactor. It was shown that both the fuel ash and bed material have an effect on the catalytic activity during gasification. Scanning electron microscopy and energy dispersive X-ray spectrometry showed the initial layer formation for experiments with ash-rich fuels. Isolated WGS experiments were performed to further highlight the influence of bed material, fuel ash and fuel ash layers on the WGS equilibrium.

Firewood roomheaters are popular, widespread and important for reaching European CO₂ emission targets. Since they contribute significantly to local air pollution, they have to be optimized towards minimal emission release, especially in real-life operation. Draught conditions and user behavior, particularly the ignition technique, significantly affect the emission and efficiency performance of firewood roomheaters. This study assessed the effects of the respective parameters experimentally. The results revealed a clear correlation between draught conditions and thermal efficiency. Increased draught conditions up to 48 Pa significantly decreased thermal efficiency by 6%–11% absolutely. However, for gaseous emissions no clear trend was observed. Accordingly, CO and OGC emissions increased at higher draught conditions for one tested roomheater by 30% and 60%, but decreased for two other tested roomheaters by 13%–45%. For PM emissions no effect of increased draught conditions was evident. Top-down ignition technique did not lead to a significant decrease of PM emissions compared to bottom-up ignition. In contrast, bottom-up ignition led to best thermal efficiencies. The use of either spruce or beech as kindling material revealed no significant relevance for the ignition performance.

Oxygen carrier aided combustion (OCAC) is a novel technology that aims to enhance combustion of heterogenous fuels by replacing the inert bed material with an active oxygen carrier. One of the promising oxygen carriers is natural ilmenite which shows decent oxygen transport capacity and mechanical stability under OCAC operating conditions. However, interactions between ilmenite and woody biomass ash lead to the formation of a calcium-rich ash layer, which affects the ability of the oxygen carrier (OC) to transfer oxygen throughout the boiler and subsequently decreases the combustion efficiency. This paper focuses on the time-dependent morphological and compositional changes in ilmenite bed particles and the consequence effects on the oxygen transport capacity and reactivity of ilmenite. Ilmenite utilized in this study was investigated in a 5 kW bubbling fluidized bed combustion unit, utilizing ash-rich bark pellets as fuel. A negative effect of iron migration on the oxygen transport capacity was observed in ilmenite bed particles after 6 h of operation in the bubbling fluidized bed reactor. The decrease in the oxygen transport capacity of ilmenite was found to correlate with the increased exposure time in the fluidized bed reactor and was caused by the migration and subsequent erosion of Fe from the ilmenite particles. On the other hand, the older bed particles show an increase in reaction rate, presumably due to the catalytic activity of the calcium-enriched outer layer on the bed particle surface.

The microalga Acutodesmus obliquus was investigated as a feedstock in semi-continuously fed anaerobic digestion trials, where A. obliquus was co-digested with pig slurry and maize silage. Maize silage was substituted by both 10% and 20% untreated, and 20% ultrasonicated microalgae biomass on a VS (volatile solids) basis. The substitution of maize silage with 20% of either ultrasonicated and untreated microalgae led to significantly lower biogas yields, i.e., 560 dm³ kg⁻¹ VS_corr in the reference compared to 516 and 509 dm³ kg^-1VS_corr for untreated and ultrasonicated microalgae substitution. Further, the viscosities in the different reactors were measured at an OLR of 3.5 g VS dm^-3 d^-1. However, all treatments with microalgae resulted in significantly lower viscosities. While the mean viscosity reached 0.503 Pa s in the reference reactor, mean viscosities were 53% lower in reactors where maize was substituted by 20% microalgae, i.e. 0.239 Pa s, at a constant rotation speed of 30 rpm. Reactors where maize was substituted by 20% ultrasonicated microalgae had a 32% lower viscosity, for 10% microalgae substitution a decrease of 8% was measured. Decreased viscosities have beneficial effect on the bioprocess and the economy in biogas plants. Nonetheless, with regard to other parameters, no positive effect on biogas yields by partial substitution with microalgae biomass was found. The application of microalgae may be an interesting option in anaerobic digestion when fibrous or lignocellulosic substances lead to high viscosities of the digested slurries. High production costs remain the bottleneck for making microalgae an interesting feedstock.

Pyrolysis conditions in charcoal production affect yields, properties, and further use of charcoal. Reactivity is a critical property when using charcoal as an alternative to fossil coal and coke, as fuel or reductant, in different industrial processes. This work aimed to obtain a holistic understanding of the effects of pyrolysis conditions on the reactivity of charcoal. Notably, this study focuses on the complex effects that appear when producing charcoal from large biomass particles in comparison with the literature on pulverized biomass. Charcoals were produced from woodchips under a variety of pyrolysis conditions (heating rate, temperature, reaction gas, type of biomass, and bio-oil embedding). Gasification reactivity of produced charcoal was determined through thermogravimetric analysis under isothermal conditions of 850 °C and 20% of CO2. The charcoals were characterized for the elemental composition, specific surface area, pore volume and distribution, and carbon structure. The analysis results were used to elucidate the relationship between the pyrolysis conditions and the reactivity. Heating rate and temperature were the most influential pyrolysis parameters affecting charcoal reactivity, followed by the reaction gas and bio-oil embedding. The effects of these pyrolysis conditions on charcoal reactivity could primarily be explained by the difference in the meso- and macropore volume and the size and structural order of aromatic clusters. The lower reactivity of slow pyrolysis charcoals also coincided with their lower catalytic inorganic content. The reactivity difference between spruce and birch charcoals appears to be mainly caused by the difference in catalytically active inorganic elements. Contrary to pyrolysis of pulverized biomass, a low heating rate produced a higher specific surface area compared with a high heating rate. Furthermore, the porous structure and the reactivity of charcoal produced from woodchips were influenced when the secondary char formation was promoted, which cannot be observed in pyrolysis of pulverized biomass.

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.

Iron production via blast furnace utilizes coal and coke to reduce iron oxides which results in high greenhouse gas emissions. Biomass-based reducing agents may reduce its fossil carbon footprint. Charcoal as bioreducer has been since the beginning of steelmaking. In order to obtain a reducing agent which is appropriately fluidizable for pulverized coal injection (PCI), the most influential powder characteristics must be named and the influence of thermal pre-treatment and comminution technique on particle properties have to be examined. The aim is to show that particle shape design of a grinding product is feasible to a certain extent by varying mill types and how pyrolyzed wood powder properties technically relevant for powder conveying processes can be influenced .

Introduction and motivation
A key objective for the operation of biomass boilers is to achieve the highest possible efficiency while emitting the lowest possible pollutant emissions. In order to automate this task, CO-lambda optimization methods have been proposed in literature that ensure that the biomass boiler is operated at the lowest excess air ratio at which no relevant pollutant emissions occur, maximizing efficiency as a result. Since this optimal excess air ratio depends on various external factors, such as fuel properties, CO-lambda optimization methods continuously incorporate new measurements of the excess air ratio and the carbon monoxide content of the flue gas and estimate a new optimal excess air ratio during operation.
While achieving promising results in lab-scale tests, none of the CO-lambda optimization methods presented in literature has yet been able to gain practical acceptance. Either they are not robust enough and provide inaccurate estimates of the optimal excess air ratio or they are too slow and do not allow the optimal excess air ratio to be tracked sufficiently quickly. With the goal of providing a method that is fit for practical application, this publication presents a new modular approach for CO-lambda optimization that determines the optimal excess air ratio robustly and quickly, i.e. in real time.

Method
The new approach for CO-lambda optimization approximates the correlation between the excess air ratio and the carbon monoxide content of the flue gas, the CO-lambda characteristic, with a continuous, algebraic, non-linear model function. For this purpose, it uses a recursive-least-squares algorithm to continuously identify the model function’s parameters that lead to the optimal fit with the measured data, which are the excess air ratio and carbon monoxide content of the flue gas. From these model parameters, the optimal excess air ratio is calculated and defined as a desired value for the biomass boiler’s existing controller. This existing controller then ensures, that the biomass boiler is operated with this desired optimal excess air ratio, thus, maximizing efficiency and decreasing pollutant emissions. As a result, this new approach for CO-lambda optimization is entirely modular and can be applied to any biomass boiler with an existing control strategy capable of accurately adjusting the excess air ratio. For the measurement of the carbon monoxide content of the flue gas, a separate sensor has to be used. For this study the commercially available and proven in-situ exhaust gas sensor “KS1D” provided by the company LAMTEC has been used.

Long-term verification
The new approach for CO-lambda optimization was tested and validated at a biomass boiler with a nominal capacity of 2.5 MW that supplies a local heating network and combusts wood chips with a water content ranging from 30 w.t.% to 50 w.t.%. The long-term validation took place over an entire heating period, i.e. 5 months from November to March, during which the biomass boiler was operated alternately with the new approach for CO-lambda optimization and the standard control strategy, which means a constant desired residual oxygen content. In total the new approach for CO-lambda optimization was active for 1155 operating hours while the standard control strategy was active for 1310 operating hours. Compared to the standard control strategy, the new approach for CO-lambda optimization increased the biomass boiler’s efficiency by 3.8%, decreased total dust emissions by 19.5% and reduced carbon monoxide emissions on average (median) by 200 mg/m³. This demonstrates that the new approach for CO-lambda optimization is not only robust enough to run over a long period of time, it also leads to significant improvements in the biomass boiler’s operation. In addition, following these results, this new approach for CO-lambda optimization has also successfully been implemented and demonstrated at another biomass boiler with a nominal capacity of 1 MW where it has already been active for several months. This contribution presents the new approach to CO-lambda optimization in detail and discusses its technological and economic impact.

Three mono-digestion experiments treating slaughterhouse waste with high TKN concentration (~11. g/kg) were applied in lab-scale at mesophilic and psychrophilic conditions to study the impact of high ammonia concentrations and additives. Precipitation of sulphur by addition of ferrous chloride did not influence process behaviour, whereas supplementation of trace elements significantly improved process stability by reducing volatile fatty acid concentration towards zero.The limit of NH₄-N concentration causing a rise of VFAs to 19,000mg/l and reduction of methane by 25% was found between 7.7 and 9.1g/kg which correspond to NH₃ concentrations of 830-1060mg/l.Psychrophilic operation (25°C) lowered inhibitory NH₃ concentration to 140mg/l, but process performance was stable only at low OLR of 0.4kgVS/m³d.Robust performance at highest possible NH₄-N concentration (7.7g/kg), low VFA accumulation and satisfying methane yield of about 280Nm3/t COD was observed at OLR of 2.5kgVS/m³d at 37°C. © 2014 Elsevier Ltd.

A polygeneration process is about to be implemented at the biomass gasification plant in Oberwart, Austria. Apart from conventional heat and electricity production, product gas obtained from steam gasification of wood chips is used for production of hydrogen. A membrane separation process was chosen for this application. Meeting the requirements of robustness and simplicity are benefits of this technology, however, maximizing of purity and output of hydrogen is not given highest priority. Simulation results show the gas compositions of both permeate and retentate stream as a function of different membrane stage-cuts. Basically high hydrogen content in the permeate stream can be achieved, but only with the drawback of low stage-cuts. Moreover, the trade-off between hydrogen purity and hydrogen recovery as well as the influence of the operating pressure on the purity are illustrated.

Solar thermal plants have proven to be a successful player in providing heat for district heating networks. However, to ensure the efficient operation of such plants and to achieve optimal coordination with other heat generation units, thorough monitoring, quality control, and system control are required. These tasks strongly depend on accessible and reliable measurement data, which are often unavailable.

Thus, this report focuses on efficient data gathering, storage, distribution, and validation, covering data
management topics- from sensor selection to permanent data storage. The report is mainly targeted at system designers and plant operators, aiming to provide checklists and recommendations on these topics.

The report considers a general solar district heating plant, as depicted by IEA SHC Task 55  – including a collector field, heat storage, and heating center (including a biomass boiler, heat pump, and other auxiliary heating) up to the interface to the district heating network. The topics are described on a summary level of detail while referring the reader to individual articles in case more information is needed. In addition, research groups may use this report to get an overview of data management in the solar-thermal field and identify related work.

The work consists of five sections: The Required Data section lists recommended measurements and discusses meta information required to interpret the data successfully. The Data Gathering section provides recommendations for data logging – e.g., sampling rate, encoding, and formatting. The Data-Distribution section shows proven examples of architectures for collecting and distributing data. Furthermore, the Data Storage section describes what data storage technologies (e.g., CSV files or relational databases) are currently used. The section also discusses the experiences, advantages, and challenges of the respective technologies. Finally, the Data Validation section lists common data-validation procedures that can be applied to solar-thermal data and links to open-source implementations where available.

With energy systems, the problem of economic planning is decisive in the design of a low carbon and resilient future grid. Although several tools to solve the problem already exist in literature and industry, most tools only consider a single “typical year” while providing investment decisions that last around a quarter of a century. In this paper, we introduce why such an approach is limited and derive two approaches to correct this. The first approach, the Forward-Looking model, assumes perfect knowledge and makes investment decisions based on the full planning horizon. The second novel approach, the Adaptive method, solves the optimization problem in single year iterations, making incremental investment decisions that are dependant on previous years, with only knowledge of the current year. Comparing the two approaches on a realistic microgrid, we find little difference in investment decisions (maximum 21% difference in total cost over 20 years), but large differences in optimization time (up to 12000% time difference). We close the paper by discussing implications of forecasting errors on the microgrid planning process, concluding that the Adaptive approach is a suitable choice.

With energy systems, the problem of economic planning is decisive in the design of a low carbon and resilient future grid. Although several tools to solve the problem already exist in literature and industry, most tools only consider a single “typical year” while providing investment decisions that last around a quarter of a century. In this paper, we introduce why such an approach is limited and derive two approaches to correct this. The first approach, the Forward-Looking model, assumes perfect knowledge and makes investment decisions based on the full planning horizon. The second novel approach, the Adaptive method, solves the optimization problem in single year iterations, making incremental investment decisions that are dependant on previous years, with only knowledge of the current year. Comparing the two approaches on a realistic microgrid, we find little difference in investment decisions (maximum 21% difference in total cost over 20 years), but large differences in optimization time (up to 12000% time difference). We close the paper by discussing implications of forecasting errors on the microgrid planning process, concluding that the Adaptive approach is a suitable choice.

Gegenstand der Arbeit ist der thermische und thermo-chemische Aufschluss von Biertrebern. Dabei werden die Prozessbedingungen wie Chemikalien, Konzentration, Aufschlusstemperatur sowie Aufschlussdauer und deren Einfluss auf die Biogasgewinnung untersucht. Der Nachweis erfolgt entlang den einzelnen Prozessstufen Hydrolyse, Acidogenese und Methanogenese. Die Prozessparameter der Aufschlüsse haben sowohl einen starken Einfluss auf die Hydrolyse der Lignozellulose als auch auf die Bildung thermischer Nebenprodukte. Diese Zwischenprodukte beeinflussen unter anderem den Schritt der Acidogenese stark. Wohingegen die Endprodukte, Melanoidine, anaerob kaum abbaubar sind und damit die Biogasausbeute reduzieren. Die höchsten Methanerträge werden mit einer Behandlungstemperatur von 140 °C erreicht. Unterschiedlich sind dabei die Höhe der zusätzlichen Gaserträge von 28 Vol.-% mit H2O sowie rund 50 Vol.-% mit Lauge und 60 Vol.-% mit Säure. In semi-kontinuierlich beschickten Reaktoren konnten mit unbehandelten Trebern Erträge von 410 m³N CH4/Mg oTS realisiert werden. Thermisch aufgeschlossene Treber ergeben Erträge von 468 m³N CH4/Mg oTS (+14 %). Durch die Zugabe von Lauge zum thermischen Aufschluss kann der Methanertrag auf 558 m³N/Mg oTS (+36 %) gesteigert werden. Auf Grund der Prozessinstabilitäten war der acido-thermisch aufgeschlossene Treber nicht auswertbar. Der Mehrertrag in den Aufschlüssen ist auf die verbesserte Verwertung der Zellulose und Hemizellulose zurückzuführen. Durch die Vorbehandlung der Biertreber gelingt es, die Treberverwertung wirtschaftlicher zu gestalten. Nach der Vergütung im Österreichischen Ökostromgesetz 2012 können Erträge von bis 13 €/Mg FM Treber erreicht werden. Dies ist insbesondere durch eine thermo-chemischen Vorbehandlung möglich

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.

This study analyses the emission factors of two firewood room heaters under testing conditions which emulate real life operation. A 6.5 kW stove with low heat storage capacity and high leakage rate (stove A) is compared with an 8 kW air-tight stove with high heat storage capacity (stove B). Thermal efficiency, carbon monoxide (CO) and organic gaseous compound (OGC) emissions, as well as the thermal heat losses (THL) during cool down phase were investigated in a series of laboratory tests. Furthermore, the influence of closing the air supply dampers at the end of the heating cycle was evaluated. Test results for the whole test cycle (including cool down phase) showed that stove A had CO emissions of 2633 mg/MJ_Output and OGC emissions of 203 mg/MJ_Output, while stove B had CO emissions of 2408 mg/MJ_Output and OGC emissions of 109 mg/MJ_Output, when air dampers were closed. It was also found that user behaviour has a critical influence on the stoves’ performance. Closing the air supply dampers at the end of the stove operation improved the efficiency by up to 5.0 percentage points. Furthermore, the duration of the cool down phase increased, as well as CO and OGC emissions decreased. As a matter of fact, measures to improve the user behaviour as for example user trainings and accurate manuals are of major importance in order to decrease emissions and increase efficiency of domestic heating appliances. Moreover, real life emission factors of other technologies should be established in order to develop a database which can be applied in air quality dispersion models.

Around 2.7 billion people worldwide have no access to clean cooking equipment, which leads to major health problems due to high emissions of unburned products (VOC, CO and soot). A top-lit updraft gasifier cookstove with forced draft was identified as the technology with the highest potential for reducing harmful emissions from incomplete combustion in simple cookstoves. The basic variant of the stove was equipped with a fan for efficient mixing of product gas with air and fired with pellets to increase the energy density of low-grade residues. The development was conducted based on water boiling test experiments for wood and rice hull pellets and targeted CFD simulations of flow, heat transfer and gas phase combustion with a comprehensive description of the reaction kinetics, which were validated by the experiments. Emphasis was put on the reduction of CO emissions as an indicator for the burnout quality of the flue gas. The optimisation was carried out in several steps, the main improvements being the design of a sufficiently large post-combustion chamber and a supply of an appropriate amount of primary air for a more stable fuel gasification. The experiments showed CO emissions <0.2 g/MJdel for wood and rice hull pellets, which corresponds to a reduction by a factor of about 15 to 20 compared to the basic forced draft stove concept. Furthermore, these values are between 5 and 10 times lower than published water boiling test results of the best available cookstove technologies and are already close to the range of automatic pellet furnaces for domestic heating, which are considered to be the benchmark for the best possible reduction of CO emissions.

Wood pellets and wood raw materials such as chips or sawdust emit hazardous gases such as carbon monoxide (CO) and volatile organic compounds (VOCs) during processing and storage. Due to the high toxicity of CO it is necessary to identify the release mechanisms for CO and VOCs. Several studies show that organic extractives decrease during storage as well as the emissions. Therefore, the purpose of this study was to investigate a possible correlation between the organic extractive content and the release of CO and VOCs. Sawdust and pellets from Norway spruce (Picea abies), European larch (Larix decidua) and loblolly pine (Pinus taeda) were examined. Additionally, five different pellet samples from Austrian pellet producers were investigated. Soxhlet extraction with acetone was used to extract the organic content. The concentration of CO and VOCs was measured from stored wood materials and pellets in sealed glass flasks. The highest (3,41 mg CO/kg sample dm/d) and the lowest (0,02 mg CO/kg sample dm/d) release of CO were reported with freshly produced pine pellets and a spruce pellets sample from an Austrian do-it-yourself store, respectively. The results showed that the pelletizing process reduced the content of organic extractives. The emissions of pine samples concerning CO and VOCs were higher than of the spruce and larch samples. Moreover, the organic extractive content also decreased in that order. However, a direct correlation between organic extractive content and released quantities of emissions could not be established.

The current debate on biomass price volatility mainly refers to increased market dynamics and integration as well as renewable energy policy intervention. Higher price volatility leads to additional costs that are often transmitted along the supply chain to the final consumers. We empirically analyze whether or not price volatility of woody biomass commodities has increased in recent years. Results indicate that the price volatility of some woody biomass
commodities has increased, but it is still lower than of fossil fuels.

Der Leitfaden „Energiegemeinschaften im Tourismus“ zeigt, welche Möglichkeiten Energiegemeinschaften für Tourismusbetriebe, ihre Beschäftigten und Menschen, die in Tourismusregionen leben, bieten können und wie eine Energiegemeinschaft ins Leben gerufen werden
kann.

Abattoirs have a large number of energy intensive processes. Beside energy supply, disposal costs of animal by-products (ABP) are the main relevant cost drivers. In this study, successful implementation of a new waste and energy management system based on anaerobic digestion is described. Several limitations and technical challenges regarding the anaerobic digestion of the protein rich waste material had to be overcome. The most significant problems were process imbalances such as foaming and floatation as well as high accumulation of volatile fatty acids and low biogas yields caused by lack of essential microelements, high ammonia concentrations and fluctuation in operation temperature. Ultimately, 85% of the waste accumulated during the slaughter process is converted into 2700 MW h thermal and 3200 MW h electrical energy in a biogas combined heat and power (CHP) plant. The thermal energy is optimally integrated into the production process by means of a stratified heat buffer. The energy generated by the biogas CHP-plant can cover a significant share of the energy requirement of the abattoir corresponding to 50% of heat and 60% of electric demand, respectively. In terms of annual cost for energy supply and waste disposal a reduction of 63% from 1.4 Mio € to about 0.5 Mio € could be achieved with the new system. The payback period of the whole investment is approximately 9 years. Beside the economic benefits also the positive environmental impact should be highlighted: a 79% reduction of greenhouse gas emissions from 4.5 Mio kg CO₂ to 0.9 Mio kg CO₂ annually was achieved. The realized concept received the Austrian Energy Globe Award and represents the first anaerobic mono-digestion process of slaughterhouse waste worldwide.

Wärmeversorgungsanlagen von Gebäuden, bestehend aus Biomasse-Feuerung, Solarkollektoren, Pufferspeicher, Heizkreis und Warmwasserzapfstellen gewinnen aufgrund ihrer Nachhaltigkeit zunehmend an Bedeutung. In den letzten Jahren wurden insbesondere für eine effiziente Regelung der Biomasse-Feuerung sehr gute Konzepte entwickelt. Diese können jedoch zumeist aufgrund unzureichender, übergeordneter Systemregelungen nicht ihr volles Potential ausschöpfen. In ihrer primitivsten Ausführung schaltet eine Systemregelung die Biomasse-Feuerung anhand der Ladehöhe des Pufferspeichers aus und ein. Diese Art der Regelung hat unweigerlich viele Ein-/ Ausschaltvorgänge der Feuerung, sowie eine schlechte Ausnutzung des solaren Eintrags zur Folge. Insbesondere bei Biomasse-Feuerungen sind Ein-/ Ausschaltvorgänge äußerst unwirtschaftlich und führen zu stark erhöhten Schadstoffemissionen. Die häufigen Ein-/ Ausschaltvorgänge verursachen zusätzlich erhöhte Wartungs- und Betriebskosten und schlussendlich eine verkürzte Lebensdauer zahlreicher Komponenten. Um die Ein-/ Ausschaltvorgänge zu minimieren und den solaren Eintrag zu steigern, soll im Rahmen dieser Arbeit ein übergeordnetes, modellprädiktives Regelungskonzept für die gesamte Wärmeversorgungsanlage entwickelt werden. Nach einer theoretischen Einführung in gemischt-ganzzahlige Optimalsteuerungsprobleme sowie ausgewählter Lösungsmethoden werden Prädiktionsmodelle für alle Komponenten der Wärmeversorgungsanlage entwickelt. Aufbauend auf den mathematischen Modellen für die einzelnen Komponenten der Anlage wird eine nichtlineare modellprädiktive Regelung entwickelt. Diese berücksichtigt zusätzlich Wetterprognosen sowie die erwartete Lastabnahme und führt schlussendlich zu einer Minimierung des Brennstoffverbrauchs sowie der Anzahl der Ein-/ Ausschaltvorgänge. Den Abschluss der Arbeit bilden ausführliche Simulationsstudien mit unterschiedlichen Wetterszenarien sowie Vergleiche mit herkömmlichen Regelungsstrategien.  

Diffusion coefficients of various solutes in supercritical water, which were either measured or retrieved from Molecular Dynamics simulations, were reviewed. Diffusion coefficients of molecules relevant for supercritical water processes were calculated with correlations reported in the literature and compared to the values of reference data. For conditions well above the critical point of water the simple Stokes-Einstein equation predicts the diffusion coefficients with an accuracy better than 20%. For conditions near the critical point the Wilke-Chang correlation gives the most accurate results. Diffusion coefficients for typical molecules occurring in supercritical water processes such as O2, N2, CO, CO2, or CH4 are estimated to be in the range of 60 · 10⁻⁹ m²/s at 673 K and 30 MPa. For H2, for which no experimental data are available, much higher diffusion coefficients in the range of 250 · 10⁻⁹ m²/s seem plausible. The data set of binary diffusion coefficients in supercritical water, either determined experimentally or by Molecular Dynamics simulations, should be extended significantly to include more solutes, as well as higher temperatures and pressures.
 

The efficient and flexible conversion of solid biomass into energetic products will be an essential part of a future renewable, independent and reliable energy providing system. The main objective of the project Bio-CCHP is the development of a novel tri-generation system, including biomass gasification, gas cleaning, a Solid Oxide Fuel Cell (SOFC) and a cooling machine with the aim to produce electricity, heat and cold (CCHP), maximizing the efficiency and flexibility of the system. However, the employment of biomass derived product gas as fuel gas for SOFC is facing new challenges for gas quality assurance. For the evaluation of required dry high temperature gas cleaning processes the applied methods of gas characterization have to be accurate and reliable. Therefore, a comprehensive evaluation of analytical methods for the detection of SOFC harmful compounds is conducted within the ongoing project. First results of online and offline sampling and analysis methods employed at air- and steam-operated gasifiers are shown in this paper.

Four different models for heat transfer to the particles immersed in a fluidized bed were evaluated and implemented into an existing single particle model. Pyrolysis experiments have been conducted using a fluidized bed installed on a balance at different temperatures and fluidization velocities using softwood pellets. Using a heat transfer model applicable for fluidized beds, the single particle model was able to predict the experimental results of mass loss obtained in this study as well as experimental data from literature with a reasonable accuracy. A good agreement between experimental and modeling results was found for different reactor temperatures and configurations as well as different biomass types, particle sizes – in the typical range of pellets - and fluidization velocities when they were higher than . However, significant deviations were found for fluidization velocities close to minimum fluidization. Heat transfer models which consider the influence of fluidization velocity show a better agreement in this case although differences are still present.

Although the number of studies investigating the contribution of anaerobic digestion facilities to greenhouse gas (GHG) emissions has increased during the last decade, reliable data with respect to gaseous process losses from these management practices, particularly at commercial scale, is scarce (Liebetrau et al., 2013, Reinelt et al., 2017, Hrad et al., 2015). The dynamic and fugitive nature of methane emissions, changing operating conditions, and different as well as not standardised measurement approaches compromise the precise quantification of the overall emissions from full-scale biogas plants. However, reliable and verifiable emission data from biogas or biomethane facilities are required in order to optimise and improve the plant-specific process efficiency as well as future technology developments. In addition, precise and comprehensive measurement data from full-scale waste treatment facilities are needed for more accurate emission factors (EFs) estimates, which are required for annual reporting according to the Intergovernmental Panel on Climate Change (IPCC) guidelines (IPCC, 2006).
Within the European project “EvEmBi - Evaluation and reduction of different biogas plant concepts” (2018-2021, funded within the 11th ERA-NET bioenergy call) 15 partners from 5 European countries evaluate the existing technologies at biogas plants regarding their methane EFs and develop emission reduction strategies, respectively. The focus of the Austrian research group within this project is the evaluation of Austrian bio-waste plants.
In a first step, emissions from single sources as well as overall plant emissions are quantified. For the latter, the Austrian team uses an open-path technology (Open-Path Tunable-Diode-Laser-Spectroscopy) together with meteorological data (ultra-sonic anemometer) and inverse dispersion modelling (Backward Lagrangian Model). In order to determine comparable EFs, the applied methodologies are based on a measurement guideline developed in the previous project “MetHarmo – European harmonization of method to quantify methane emissions from biogas plants” (funded within the 9th ERA-NET bioenergy call). In addition, the determined EFs of the individual plant concepts are transferred to EFs of the entire plant inventory of the particular countries. For that, a model for EF quantification is used which is based on statistical information on the emissions from different plant components as well as on the distribution of certain technologies present in the participating countries. Furthermore, for the particular biogas plants emission reduction strategies are developed, implemented and verified.
In this presentation, the harmonised approach, first emission results from the Austrian measurement campaigns as well as emission reduction strategies are presented.

In order to evaluate the combustion behaviour of new biomass feedstocks such as short rotation coppice (poplar wood chips), fuels from agriculture (wheat straw pellets) and biomass residues (maize spindle grits), comprehensive test runs investigating both particulate matter (PM) and gaseous emissions were performed. A commercially available small-scale biomass boiler, especially designed to enable high fuel flexibility, was used for this evaluation. The combustion behaviour was determined for various boiler load conditions and primary air ratios while maintaining a constant total air ratio. Based on wet chemical analyses of the fuels, fuel indexes were calculated to deliver primary information on the combustion behaviour to be expected. During the test runs appropriate operating conditions were determined for these new biomass feedstocks in order to optimise combustion parameters and to minimise PM and gaseous emissions as well as to inhibit ash related problems (slagging, ash deposit formation and corrosion). The optimisation of operating conditions by primary measures showed a big potential for a stable boiler operation combined with reduced emissions. The findings provide the basis for a further development of combustion systems as well as control systems for the combustion of new biomass feedstocks.

Assessing the operational behaviour of biomass gasification systems is a crucial basis for further improvements in terms of operational behaviour and robustness in order to increase the technologies’ operational and economic viability. However, in most fixed-bed biomass gasification systems not all parameters required for the assessment can be measured directly. Typically, unknown parameters are determined by using as many balance equations as parameters have to be determined neglecting the additional information provided by other available but not chosen balance equations. Thus, these approaches do not incorporate all measurement data available resulting in a lack of reliability in their results. A detailed analysis of these approaches emphasises that even small deviations in the measurement data can lead to significant deviations in the calculated parameters, demonstrating that individual choices of equations can be highly sensitive regarding measurement uncertainties.

Therefore, an adjusted weighted least squares approach is developed utilizing an overdetermined system of equations incorporating all balance equations simultaneously. Thus, all measurement data available is taken into account, minimizing the influences of measurement uncertainties on the determined parameters. A comprehensive analysis shows that this approach is less sensitive to measurement uncertainties, allowing for a more reliable and accurate assessment of fixed-bed biomass gasifiers.

Keywords: fixed-bed, gasification, mass balance, performance assessment

The majority of renewable energy technologies are volatile in nature. External factors such as weather conditions lead to fluctuations in their produced electricity and heat. This results in a demand either not being covered or dissatisfied since too much electricity and heat is produced in the energy system. Although energy storages can counteract these fluctuations, renewable energy technologies that are capable of producing energy on demand are needed as well. As such, technologies based on the thermochemical conversion of biomass are especially relevant as they are considered to be CO2-neutral. Although most existing implementations are based on combustion of biomass, fixed-bed biomass gasification is of growing relevance due to higher overall efficiencies and low pollutant emissions. Currently, fixed-bed biomass gasifiers are usually operated at steady-state operation to produce the maximum amount of energy possible. This contribution investigates, whether they can be used as a technology for demand-oriented electricity and heat production

Producer gas from biomass gasification contains mainly hydrogen, carbon dioxide, carbon monoxide, methane and some other low molecular hydrocarbons like propylene. This paper reports mathematical simulation and experimental study of steam reforming of methane mixture with propylene in a packed bed reactor filled with nickel based catalysts. Due to the high heat input through the reformer tube wall and the endothermic reforming reactions, a two-dimensional pseudo-heterogeneous model that takes into account the diffusion reaction phenomena in gas phase as well as inside the catalyst particles has been used to represent temperature distribution and species concentration within the reactor. Steam reforming of propylene is faster and more selective than methane and it is shown that addition of propylene to the methane steam mixture reduces the conversion of methane. The obtained results play a key role in optimization and design of a commercial reactor. © 2014 Elsevier Ltd. All rights reserved.
 

The worldwide production of hydrogen in 2010 was estimated to be approximately 50 Mt/a, mostly based on fossil fuels. By using lignocellulosic feedstock, an environmentally friendly hydrogen production route can be established. A flow sheet simulation for a biomass based hydrogen production plant was published in a previous work. The plant layout consisted of a dual fluidized bed gasifier including a gas cooler and a dust filter. Subsequently, a water gas shift plant was installed to enhance the hydrogen yield and a biodiesel scrubber was used to remove tars and water from the syngas. CO2 was removed and the gas was compressed to separate hydrogen in a pressure swing adsorption. A steam reformer was used to reform the hydrocarbon-rich tail gas of the pressure swing adsorption and increase the hydrogen yield. Based on this work, a research facility was erected and the results were validated. These results were used to upscale the research plant to a 10 MW fuel feed scale. A validation of the system showed a chemical efficiency of the system of 60% and an overall efficiency of 55%, which indicates the high potential of this technology

Chemical looping combustion is a highly efficient CO2 separation technology without direct contact between combustion air and fuel. A metal oxide is used as an oxygen carrier in dual fluidized beds to generate clean CO2. The use of biomass is the focus of current research because of the possibility of negative CO2 emissions and the utilization of biogenic carbon. The most commonly proposed OC are natural ores and residues, but complete combustion has not yet been achieved. In this work, the direct utilization of CLC exhaust gas for methane synthesis as an alternative route was investigated, where the gas components CO, CH4 and H2 are not disadvantageous but benefit the reactions in a methanation step. The whole process chain, the coupling of an 80 kWth pilot plant with gas cleaning and a 10 kW fluidized bed methanation unit were for this purpose established. As OC, ilmenite enhanced with limestone was used, combusting bark pellets in autothermal operation at over 1000 °C reaching high combustion efficiencies of up to 91.7%. The fuel reactor exhaust gas was mixed with hydrogen in the methanation reactor at 360 °C and converted with a methane yield of up to 97.3%. The study showed especially high carbon utilization efficiencies of 97% compared to competitor technologies. Based on the experimental results, a scale-up concept study showed the high potential of the combination of the technologies concerning the total efficiency and the adaptability to grid injection.

The aim of this work is to utilize various biogenic fuels without ash slagging and to significantly reduce NOX and particulate matter emissions in comparison to modern combustion technologies. For this purpose, a novel small-scale multi-fuel biomass grate furnace technology was developed and experimentally investigated. It employs a low oxygen concentration in the fixed-bed and a double air staging, including the supply of flue gas recirculation. In this way slagging is prevented on the grate, reducing the release of ash-forming volatiles, NOX emissions are minimized in the reduction zone and an efficient flue gas burnout is achieved in the tertiary zone. Wood pellets and chips as well as miscanthus briquettes were investigated.

The measured total particle emissions showed a reduction of 68% for pellets and 70% for wood chips compared to typical small-scale furnaces. Furthermore, a reduction of NOX emissions of 39% for wood chips, 40% for wood pellets and 45% for miscanthus briquettes was achieved compared to typical small-scale furnaces. The experimental parameter study provided fundamental insights into the various mechanisms involved in this novel technology, which is close to market introduction, and proved its high fuel flexibility and great potential for particulate matter and NOX emission reduction.

Experimental data on the release of NO_x 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 NO_x 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 NO_x 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 NO_x 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. © 2007 Elsevier Ltd. All rights reserved.

In this paper, the activity of a cobalt/molybdenum (Co/Mo) commercial catalyst for the Water Gas Shift Reaction for hydrogen production was investigated in a three fixed-bed reactor pilot plant using a tar-rich synthesis gas from a full-scale biomass gasification plant as feed-stream. A parametric variation study was carried out to assess CO conversion (X_CO) and selectivity for the water gas shift reaction as a function of the operating temperature (T) in the range 300–450 °C. The effects of four dry gas hourly space velocities (GHSV), Case A-Case D, two steam to dry synthesis gas ratios (H₂O/SG), 56% v/v and 67% v/v, and a H₂S concentration in the range 100–220 ppm_v,db were investigated: the highest CO conversion (∼95%) was observed in the base case (Case A GHSV) at 67% v/v H₂O/SG, and 450 °C, the lower the operating temperature the lower the CO concentration, the lower the gas hourly space velocity the higher the CO conversion and the higher the H₂O/SG the higher the CO conversion. The effect of H₂S variation on CO conversion was also studied, keeping the operating temperature constant (≈365 °C) and using the Case D GHSV: CO conversion increased as the H₂S concentration increased and X_CO ≈ 40%. Selectivity was not influenced by the parameters investigated. Finally, the effect of the catalyst on tar removal was studied and a CO conversion close to 85% was found.

Nowadays dynamic building simulation is an essential tool for the design of heating systems for residential buildings. The simulation of buildings heated by biomass systems, first of all needs detailed boiler models, capable of simulating the boiler both as a stand-alone appliance and as a system component. This paper presents the calibration and validation of a boiler model by means of laboratory tests. The chosen model, i.e. TRNSYS "Type 869", has been validated for two commercially available pellet boilers of 6 and 12. kW nominal capacities. Two test methods have been applied: the first is a steady state test at nominal load and the second is a load cycle test including stationary operation at different loads as well as transient operation. The load cycle test is representative of the boiler operation in the field and characterises the boiler's stationary and dynamic behaviour. The model had been calibrated based on laboratory data registered during stationary operation at different loads and afterwards it was validated by simulating both the stationary and the dynamic tests. Selected parameters for the validation were the heat transfer rates to water and the water temperature profiles inside the boiler and at the boiler outlet. Modelling results showed better agreement with experimental data during stationary operation rather than during dynamic operation. Heat transfer rates to water were predicted with a maximum deviation of 10% during the stationary operation, and a maximum deviation of 30% during the dynamic load cycle. However, for both operational regimes the fuel consumption was predicted within a 10% deviation from the experimental values. © 2014 Elsevier Ltd.