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  • 1.
    Andersson, Jim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Methanol production via pressurized entrained flow biomass gasification: Techno-economic comparison of integrated vs. stand-alone production2014In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 64, p. 256-268Article in journal (Refereed)
    Abstract [en]

    The main objective with this work was to investigate techno-economically the opportunity for integrated gasification-based biomass-to-methanol production in an existing chemical pulp and paper mill. Three different system configurations using the pressurized entrained flow biomass gasification (PEBG) technology were studied, one stand-alone plant, one where the bark boiler in the mill was replaced by a PEBG unit and one with a co-integration of a black liquor gasifier operated in parallel with a PEBG unit. The cases were analysed in terms of overall energy efficiency (calculated as electricity-equivalents) and process economics. The economics was assessed under the current as well as possible future energy market conditions. An economic policy support was found to be necessary to make the methanol production competitive under all market scenarios. In a future energy market, integrating a PEBG unit to replace the bark boiler was the most beneficial case from an economic point of view. In this case the methanol production cost was reduced in the range of 11–18 Euro per MWh compared to the stand-alone case. The overall plant efficiency increased approximately 7%-units compared to the original operation of the mill and the non-integrated stand-alone case. In the case with co-integration of the two parallel gasifiers, an equal increase of the system efficiency was achieved, but the economic benefit was not as apparent. Under similar conditions as the current market and when methanol was sold to replace fossil gasoline, co-integration of the two parallel gasifiers was the best alternative based on received IRR.

  • 2.
    Boman, Christoffer
    et al.
    Umeå university.
    Nordin, Anders
    Umeå universitet.
    Westerholm, Roger
    Stockholm University.
    Pettersson, Esbjörn
    Evaluation of a constant volume sampling set-up for residential biomass fired appliances: influence of dilution conditions on particulate and PAH emissions2005In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 29, p. 258-268Article in journal (Refereed)
  • 3.
    Difs, Kristina
    et al.
    Division of Energy Systems, Department of Mechanical Engineering, Linköping Institute of Technology.
    Wetterlund, Elisabeth
    Trygg, Louise
    Division of Energy Systems, Department of Mechanical Engineering, Linköping Institute of Technology.
    Söderström, Mats
    Division of Energy Systems, Department of Mechanical Engineering, Linköping Institute of Technology.
    Biomass gasification opportunities in a district heating system2010In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 34, no 5, p. 637-651Article in journal (Refereed)
    Abstract [en]

    This paper evaluates the economic effects and the potential for reduced CO2 emissions when biomass gasification applications are introduced in a Swedish district heating (DH) system. The gasification applications included in the study deliver heat to the DH network while producing renewable electricity or biofuels. Gasification applications included are: external superheater for steam from waste incineration (waste boost, WB), gas engine CHP (BIGGE), combined cycle CHP (BIGCC) and production of synthetic natural gas (SNG) for use as transportation fuel. Six scenarios are used, employing two time perspectives – short-term and medium-term – and differing in economic input data, investment options and technical system. To evaluate the economic performance an optimisation model is used to identify the most profitable alternatives regarding investments and plant operation while meeting the DH demand. This study shows that introducing biomass gasification in the DH system will lead to economic benefits for the DH supplier as well as reduce global CO2 emissions. Biomass gasification significantly increases the potential for production of high value products (electricity or SNG) in the DH system. However, which form of investment that is most profitable is shown to be highly dependent on the level of policy instruments for biofuels and renewable electricity. Biomass gasification applications can thus be interesting for DH suppliers in the future, and may be a vital measure to reach the 2020 targets for greenhouse gases and renewable energy, given continued technology development and long-term policy instruments.

  • 4.
    Gabra, Mohamed
    et al.
    Luleå tekniska universitet.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Salman, H.
    Luleå tekniska universitet.
    Development of a sugar cane residue feeding system for a cyclone gasifier1998In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 15, no 2, p. 143-153Article in journal (Refereed)
    Abstract [en]

    For the smooth and continuous operation of a cyclone gasifier, the fuel must be fed continuously and without interruption or large fluctuations. A feeding system for bagasse/cane trash powder was therefore designed, built and tested. It consisted of a feeding bin with four feeder screws in the bottom which deliver the fuel to two downcomers from which the fuel is injected by steam into the gasifier. During the first tests, the low bulk density and cohesive characteristics of a crushed bagasse/cane trash powder were found to cause an accumulation of the fuel in the feeding system, creating difficulties for the flow into the gasifier. In addition, once the flow of the crushed bagasse/cane trash powder is interrupted by a build-up in the downcomer channels, the crushed bagasse/cane trash powder becomes progressively compacted into a dense structure, resulting in blockage of the discharge. It was found possible to eliminate this problem by changing the shape of the slivers of the crushed bagasse/cane trash powder to render them more homogeneous. This was achieved by pelletizing the crushed bagasse or cane trash before grinding it to powder.

  • 5.
    Gabra, Mohamed
    et al.
    Energy Technology Centre, Piteå.
    Nordin, Anders
    Avdelningen för oorganisk kemi, Umeå universitet.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Kjellström, Björn
    Alkali retention/separation during bagasse gasification: a comparison between a fluidised bed and a cyclone gasifier2001In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 21, no 6, p. 461-476Article in journal (Refereed)
    Abstract [en]

    Biomass fuelled integrated gasification/gas turbines (BIG/GTs) have been found to be one of the most promising technologies to maximise electricity output in the sugar industry. However, biomass fuels contain alkali metals (Na and K) which may be released during the gasification processes and cause deleterious effects on the downstream hardware (e.g. the blades of gas turbines). Much research has therefore been focused on different kinds of gas cleaning. Most of these projects are using a fluidised bed gasifier and includes extensive gas cleaning which leads to a high capital investment. Increasing alkali retention/separation during the gasification may lead to improved producer gas quality and reduced costs for gas cleaning. However, very little quantitative information is available about the actual potential of this effect. In the present work, comparative bench-scale tests of bagasse gasification were therefore run in an isothermal fluidised bed gasifier and in a cyclone gasifier to evaluate which gasification process is most attractive as regards alkali retention/separation, and to try to elucidate the mechanisms responsible for the retention. The alkali retention in the fluidised bed gasifier was found to be in the range of 12-4% whereas in the cyclone gasifier the alkali separation was found to be about 70%. No significant coating of the fluidised bed's bed material particles could be observed. The SEM/EDS and the elemental maps of the bed material show that a non-sticky ash matrix consisting of mainly Si, Al and K were distributed in a solid form separated from the particles of bed material. This indicates the formation of a high temperature melting potassium containing silicate phase, which is continuously scavenged and lost from the bed through elutriation.

  • 6.
    Gabra, Mohamed
    et al.
    Luleå tekniska universitet.
    Pettersson, Esbjörn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Backman, Rainer
    Energy Technology Centre in Piteå, Division of Chemical Engineering, Åbo Akademi University.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Evaluation of cyclone gasifier performance for gasification of sugar cane residue. Part 1: gasification of bagasse2001In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 21, no 5, p. 351-369Article in journal (Refereed)
    Abstract [en]

    A method for avoiding excessive amount of alkali compounds and carryover particles in producer gas from gasification of sugar cane residue has been studied and evaluated. The cane sugar residue is gasified in a two-stage combustor at atmospheric pressure, where the first stage is a cyclone gasifier. The cyclone works as particle separator as well. This paper covers the results obtained for gasification of bagasse. Bagasse powder was injected into the cyclone with air and steam as transport medium. The gasification tests were made with two feeding rates, 39 and 52 kg/h. Seven experiments were conducted with the equivalence ratio being varied. The heating values of the producer gas are sufficient for stable gas turbine combustion. About 60-70% of the alkali input with fuel was separated from the producer gas in the cyclone. However the total alkali contents of the producer gas was found to be higher than in ABB Stal PFBC gas turbines and at least an order of magnitude higher than what is required by most gas turbine manufacturers for operation of a gas turbine. The carryover particles concentrations in the producer gas were found to be in the range of that for PFBC gas turbines, but higher than what is required by most gas turbine manufacturers for operation of a gas turbine. Samples studied with scanning electronic microscope give indication that most of the carryover particles are below 10 μm in size. Fly ash-melting tests have not shown any major ash melting up to 1200°C, but it was found that some of the particles entrained with producer gas were partially melted. Integrated experiments with a gas turbine need to be done for accurate evaluation of the possibilities to use the producer gas from the gasification of bagasse to run a gas turbine without problems of hard deposits and corrosion on the turbine blades. In part 2 of this two-part paper the results from cane trash gasification tests are reported.

  • 7.
    Gabra, Mohamed
    et al.
    Luleå tekniska universitet.
    Pettersson, Esbjörn
    Backman, Rainer
    Energy Technology Centre in Piteå, Division of Chemical Engineering, Åbo Akademi University.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Evaluation of cyclone gasifier performance for gasification of sugar cane residue. Part 2: gasification of cane trash2001In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 21, no 5, p. 371-380Article in journal (Refereed)
    Abstract [en]

    In Part 1 of this two-part paper, results from gasification of bagasse in a cyclone gasifier have been reported. In this paper results from gasification of cane trash in the same cyclone gasifier are presented. The cane trash powder is injected into the cyclone with air as transport medium. The gasification tests were made with two feeding rates, 39 and 46 kg/h at two equivalence ratios of 0.25 and 0.20 and the gasification temperature ranging from 820°C to 850°C. It was found that the heating value of the producer gas is in the range of 4.5-4.8 MJ/Nm3(dry gas), which is sufficient for stable gas turbine combustion. Significant alkali separation has been achieved in the cyclone stage. However, the alkali levels and carryover particle concentrations in the producer gas were found to be higher than allowable in a gas turbine. Despite high ash melting temperatures found by the TGA-DTA, deposition problems cannot be excluded since some carryover particles in the producer gas seem to have been melted and since some gasification of K and Na compounds is indicated. As an overall assessment, cane trash appears as a more problematic fuel than bagasse for this application. Integrated experiments with a gas turbine need to be done for accurate evaluation of the possibilities to use the producer gas from the gasification of cane trash to run a gas turbine without problems of hard deposits and corrosion on the turbine blades.

  • 8.
    Hassan, Salman
    et al.
    Luleå tekniska universitet.
    Kjellström, Björn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Pneumatic conveying of wood powder by using a steam-jet ejector2000In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 19, no 2, p. 103-117Article in journal (Refereed)
    Abstract [en]

    Wood powder and sawdust are two fuels which will be tested in a pressurized cyclone-gasifier. The gasifier will be a part of combined cycle power plant where a gas turbine is run by the product gases from the gasifier and a steam boiler will use the exhaust gas from the turbine. To inject the fuel into the cyclone, a steam-jet ejector seems to be appropriate due to its simplicity and the possibility of using the steam produced by the boiler for feeding of the fuel. Three types of wood powder with different particle-size distribution have been tested in different ejector geometries. The results show that the steam-jet ejector is suitable as a feeding pump for wood powder and sawdust. For commercial wood powder fuel with particle size below 1 mm, a powder to steam mass flow ratio of about 25 and with coarser sawdust a mass flow ratio of at least 10 can be reached. The pressure gain required to overcome the pressure drop in the cyclone gasifier can be achieved. The relative pressure gain seems to be independent of the size distribution of the particles.

  • 9.
    Hebenstreit, Babette
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Schnetzinger, R.
    Bioenergy 2020+ GmbH.
    Ohnmacht, R.
    Bioenergy 2020+ GmbH.
    Höftberger, E.
    Bioenergy 2020+ GmbH.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Haslinger, W.
    Bioenergy 2020+ GmbH.
    Toffolo, Andrea
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Techno-economic study of a heat pump enhanced flue gas heat recovery for biomass boilers2014In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 71, p. 12-22Article in journal (Refereed)
    Abstract [en]

    An active condensation system for the heat recovery of biomass boilers is evaluated. The active condensation system utilizes the flue gas enthalpy exiting the boiler by combining a quench and a compression heat pump. The system is modelled by mass and energy balances. This study evaluates the operating costs, primary energy efficiency and greenhouse gas emissions on an Austrian data basis for four test cases. Two pellet boilers (10 kW and 100 kW) and two wood chip boilers (100 kW and 10 MW) are considered. The economic analysis shows a decrease in operating costs between 2% and 13%. Meanwhile the primary energy efficiency is increased by 3–21%. The greenhouse gas emissions in CO2 equivalents are calculated to 15.3–27.9 kg MWh−1 based on an Austrian electricity mix. The payback time is evaluated on a net present value (NPV) method, showing a payback time of 2–12 years for the 10 MW wood chip test case.

  • 10.
    Joppich, A.
    et al.
    Vienna University of Technology, Institute of Thermal Turbomachines and Powerplants.
    Salman, Hassan
    Luleå tekniska universitet.
    Wood powder feeding, difficulties and solutions1999In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 16, no 3, p. 191-198Article in journal (Refereed)
    Abstract [en]

    pneumatic fuel feeding system for wood powder fired gas turbines was incorporated at the Vienna University of Technology. One of the most important requirements of fuel feeding is a very homogeneous mass flow of wood powder. Therefore, the performance of the mechanical conveying part of the feeding system has been studied experimentally at flow rates corresponding to the operation range. Beside screw feeding, a vibrator is used to homogenize the flow rate. While the screw feeder shows large fluctuations, the vibrator conveyer reduces them considerably. The tests also show that for each flow rate a certain optimum amplitude of the vibrator exists at which the fluctuations reach a minimum. Furthermore, a linear function is observed between optimum oscillation amplitude and feeding rate.

  • 11.
    Kirtania, Kawnish
    et al.
    Monash University, Melbourne, VIC.
    Bhattacharya, Sankar
    Monash University, Melbourne, VIC.
    Pyrolysis kinetics and reactivity of algae-coal blends2013In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 55, p. 291-298Article in journal (Refereed)
    Abstract [en]

    This paper presents results from a thermogravimetric analysis and modelling based study using a fresh water alga, Chlorococcum humicola, and a Victorian Brown Coal and their blends at different proportions. Pyrolysis was studied using the pure coal and pure algae as well as their blends to a final temperature of 1000°C at different heating rates to understand the kinetics. The kinetic data of pure algae and pure coal were used to predict the pyrolysis characteristics of coal-algae blends at various heating rates using a modified distributed activation energy model which closely matched the experimental data. The experimental results also indicate that there is no chemical interaction between the algae and coal during pyrolysis. © 2013 Elsevier Ltd.

  • 12.
    Koullas, D.P.
    et al.
    National Technical University of Athens.
    Christakopoulos, Paul
    Kekos, D.
    National Technical University of Athens.
    Koukios, E.G.
    National Technical University of Athens.
    Macris, B.J.
    National Technical University of Athens.
    Effect of alkali delignification on wheat straw saccharification by fusarium oxysporum cellulases1993In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 4, no 1, p. 9-13Article in journal (Refereed)
    Abstract [en]

    The effect of alkaline delignification of wheat straw on the chemical composition and the subsequent enzymic hydrolysis of the pretreated straw are reported. Both hot (120°°C) and cold (20–36°°C) delignification were investigated, using either aqueous or organic alkaline solutions. The treated lignocellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Both delignification and saccharification yield showed linear relationships with the level of alkali used. Under the chosen experimental conditions 70–100% hydrolysis was achieved either by hot or cold delignification. Delignification to at least 50% appeared crucial for total polysaccharide conversion.

  • 13. Kudahettige-Nilsson, Rasika
    et al.
    Holmgren, Marie
    Umeå Plant Science Centre, Department of Plant Physiology, Umeå University.
    Madavi, Batol
    Tarbiat Modares University.
    Nilsson, Robert
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sellstedt, Anita
    Umeå Plant Science Centre, Department of Plant Physiology, Umeå University.
    Adaptability of Trametes versicolor to the lignocellulosic inhibitors furfural, HMF, phenol and levulinic acid during ethanol fermentation2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 90, p. 95-100Article in journal (Refereed)
    Abstract [en]

    Ligno-cellulosic biofuels, notably ethanol produced in processes involving biological fermentation, have high potential as renewable alternatives to fossil fuels. However, ligno-cellulose pretreatment procedures generate substances that inhibit current biocatalysts. Thus, efficient methods are required for improving these organisms' tolerance or developing new biocatalysts with higher tolerance to the inhibitors. For this, greater knowledge of the mechanisms involved is needed. Therefore, we examined effects of common inhibitors (phenol, levulinic acid, HMF (hydroxymethylfurfural) and furfural) on growth, utilization of sugars (xylose, mannose and glucose) and enzyme activities of a tolerant organism, the white-rot fungus Trametes versicolor, during 15-day incubations. The fungus metabolized and grew in the presence of all the inhibitors (singly and together) at the applied concentration (0.2–0.6 g/L). When all inhibitors were added, no significant effect of sugar utilization was shown. However, levulinic acid added solely reduced xylose (but not xylose-degrading enzymes) and mannose utilization, but not glucose utilization. Physiological and biotechnological implications of the findings are discussed such as usage of T. versicolor as a detoxifying agent in ethanol production.

  • 14.
    Lagerkvist, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Landfill gas activity of the IEA bioenergy agreement1995In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 9, no 1-5, p. 399-413Article in journal (Refereed)
    Abstract [en]

    Landfill gas (LFG) is a renewable source of useful energy. Its world wide annual energy potential is in the range of a few hundred TWh. Today it is only marginally exploited. LFG is also an important contributor to the atmospheres CH4-content, it can be estimated to contribute about 25% of the methane coming from anthropogenic sources. In comparison to many other sources of methane emissions such as peat bogs, rice paddies, termites and sheep, landfills can be considered to be point sources, i.e. they are stationary and of limited extension. For this reason landfill gas (LFG) utilisation is one of the most cost effective ways to combat the greenhouse effect. The aim of the IEA activity on LFG is to promote information exchange and co-operation between national programmes in order to promote the proliferation of landfill gas utilisation. During the period 1992–1994 the LFG activity has had six participating countries: Canada, Denmark, Norway, The Netherlands, Sweden, UK and USA. In the past three-year period, the activity has been mainly directed towards establishing networks and obtaining an over-view of data related to LFG in the member countries. Numerous contacts have been established and perhaps of most importance for the future of the activity are the links towards organisations involved in the development of landfill technology, such as ISWA and SWANA. The gathering and evaluation of data within the LFG area from the member countries has resulted in a number of documents that are to be published within the near future. These documents cover information on LFG utilisation, landfill research, landfill gas potentials, landfill emission assessment and also non-technical barriers to LFG utilisation.

  • 15.
    Leduc, Sylvain
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), A-2361 Laxenburg, Austria.
    Schmid, Erwin
    University of Natural Resources and Applied Life Sciences (BOKU), A-1180 Vienna, Austria.
    Obersteiner, Michael
    International Institute for Applied Systems Analysis (IIASA), A-2361 Laxenburg, Austria.
    Riahi, Keywan
    International Institute for Applied Systems Analysis (IIASA), A-2361 Laxenburg, Austria.
    Methanol production by gasification using a geographically explicit model2009In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 33, no 5, p. 745-751Article in journal (Refereed)
    Abstract [en]

    Methanol mixed with 15% gasoline appears to be a viable alternative energy source for the transportation sector. Produced from gasification of certified wood coming from well-managed forests, its production could be considered as sustainable and the well-to-wheel emissions can be reduced significantly. The physical flows of the entire bio-energy chain consisting of harvesting, biomass transportation, methanol production by gasification, methanol transportation, and methanol distribution to the consumers are assessed and costs are estimated for each part of the chain. A transportation model has been constructed to estimate the logistic demands of biomass supply to the processing plant and to the supply of gas station. The analysis was carried out on a case study for the geography of Baden-Württemberg, Germany. It has been found that a typical optimal size for methanol production of some 130,000 m3, supplies about 100 gas stations, and the biomass supply requires on average 22,000 ha of short-rotational poplar, with an average transportation distance of biomass of some 50 km to the methanol processing plant. The methanol production costs appear to be most sensitive with respect to methanol plant efficiency, wood cost, and operating hours of the plant. In an area where biomass is spread heterogeneously, apart from the demand, the geographical position of the plant would appear to have a major impact on the final biofuel cost.

  • 16. Lundgren, Joakim
    et al.
    Hermansson, Roger
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Experimental studies during heat load fluctuations in a 500 kW wood-chips fired boiler2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 26, no 3, p. 255-267Article in journal (Refereed)
    Abstract [en]

    Several long-term experiments with fluctuating thermal outputs have been carried out in a newly developed biomass fuelled boiler suitable for small district heating networks. The experiments have been performed by either using the furnace only or the furnace together with a water heat store. Comparisons between these two operation strategies have been made concerning emissions and overall performance. Furthermore, the plant has been run to match a simulated heat demand during different seasons, in order to study the performance of the system during more realistic operation conditions. The results are very satisfactory concerning both performance and emissions, using any of the control strategies. Typical emissions of CO and NOx during the experiments are in the range of 10–50 mgNm−3 (5–25 mgMJ−1) and 130–175 mgNm−3 (60–90 mgMJ−1), respectively. However, during summer when the heat demand is low or zero, operational problems will occur if the heat store is excluded. Therefore, the main conclusion is that the most appropriate solution for a small district-heating system is to use a water heat store to match the heat load variations, while the furnace operates at as constant thermal output as possible.

  • 17.
    Lundgren, Joakim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hermansson, Roger
    Dahl, Jan
    Experimental studies of a biomass boiler suitable for small district heating systems2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 26, no 5, p. 443-453Article in journal (Refereed)
    Abstract [en]

    Extensive experiments have been carried out in a newly developed furnace suitable for small district heating networks. The fuel is wood-chips with moisture content in the range of 30-58%. One of the unique features of this new furnace is the broad thermal output span, which makes it possible to run the boiler down to 10% of maximum heat load, with maintained low emissions of CO and total hydrocarbons (THC). The aim of this study has been to evaluate the performance of the combustion chamber during steady-state operation in the complete thermal output range. The experiments show very good results over the entire thermal output range. In the range 60 kW up to 500 kW, the average CO content in the stack gases is typically below 25 mg Nm-3(20 ppm) and the NOx concentration below 195 mg Nm-3(95 ppm) during steady state conditions. At lower thermal outputs, the average CO content is below 105 mg Nm-3(84 ppm). (All values standardised to 10 vol% O 2.)

  • 18.
    Lundmark, Robert
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Athanassiadis, Dimitris
    SLU Swedish University of Agricultural Sciences.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Supply assessment of forest biomass: A bottom-up approach for Sweden2015In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 75, p. 213-226Article in journal (Refereed)
    Abstract [en]

    As there is increasing interest in the use of biomass for energy in Sweden, the potential availability and harvesting costs of forest roundwood, harvesting residues and stumps were estimated up to the year 2069 in 10-year intervals, using a high spatial resolution GIS. In each individual forest area, an average harvesting cost per forest assortment was estimated, based on the geographic and other properties of the area. Using cost structure and resource availability, marginal cost curves were constructed to allow analyses of the effects of changing market conditions and different policy frameworks. Based on geographically explicit data, the results indicated that the average harvesting costs would be 21–24 € m−3 for roundwood, depending on the type of harvesting and extraction operation. The corresponding cost estimate for harvesting residues was 23–25 € m−3 and 35 € m−3 for stumps. The harvesting cost estimates lie on the steeper part of the marginal cost curve, suggesting that increases in the supply of woody biomass can only occur at significantly higher harvesting costs. From a policy perspective, this suggests that subsidies aimed at reducing the harvesting costs will only have limited success in increasing the harvested volumes, given current technology. Therefore, for future development in the supply of forest assortments for energy generation, it is important to consider not only the supply potential, but also the integration of improvements in harvesting and transportation systems.

  • 19.
    Lundmark, Robert
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Shahrammehr, Shima
    Forest biomass and Armington elasticities in Europe2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 1, p. 415-420Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to provide estimated Armington elasticities for selected European countries and for three forest biomass commodities of main interest in many energy models: roundwood, chips & particles and wood residues. The Armington elasticity is based on the assumption that a specific forest biomass commodity is differentiated by its origin. The statistically significant estimated Armington elasticities range from 0.52 for roundwood in Hungary to approximately 4.53 for roundwood in Estonia. On average, the statistically significant Armington elasticity for chips & particles over all countries is 1.7 and for wood residues and roundwood 1.3 and 1.5, respectively. These elasticities can provide benchmark values for simulation models trying to assess trade patterns of forest biomass commodities and energy policy effects for European countries or for the EU as a whole.

  • 20.
    Mamma, D.
    et al.
    National Technical University of Athens.
    Christakopoulos, Paul
    Koullas, D.
    National Technical University of Athens.
    Kekos, D.
    National Technical University of Athens.
    Macris, B.J.
    National Technical University of Athens.
    Koukios, E.
    National Technical University of Athens.
    An alternative approach to the bioconversion of sweet sorghum carbohydrates to ethanol1995In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 8, no 2, p. 99-103Article in journal (Refereed)
    Abstract [en]

    The ethanol fermentation of juice and press cake, resulting from the squeezing of sweet sorghum stalks at high pressure, was investigated. The juice was fermented by Saccharomyces cerevisiae and yielded 4.8 g ethanol per 100 g of fresh stalks. The press cake was fermented directly to ethanol by a mixed culture of Fusarium oxysporum and Saccharomyces cerevisiae and yielded 5.1 g ethanol per 100 g of fresh stalks. An overall ethanol concentration and yield of 5.6% (w/v) and 9.9 g of ethanol per 100 g of fresh stalks respectively was obtained. Based on soluble carbohydrates, the ethanol yield from press cake was doubled while the overall theoretical yield was enhanced by 20.7% due to the bioconversion of a significant portion of cell wall polysaccharides to ethanol. The process was found promising for further investigation.

  • 21.
    Mandova, Hana
    et al.
    Bioenergy Centre for Doctoral Training, School of Chemical and Process Engineering, University of Leeds.
    Leduc, Sylvain
    International Institute for Applied Systems Analysis (IIASA).
    Wang, Chuan
    Swerea MEFOS, Luleå.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA).
    Patrizio, Piera
    International Institute for Applied Systems Analysis (IIASA).
    Gale, William Jeffrey
    Centre for Integrated Energy Research, University of Leeds.
    Kraxner, Florian
    International Institute for Applied Systems Analysis (IIASA).
    Possibilities for CO2 emission reduction using biomass in European integrated steel plants2018In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 115, p. 231-243Article in journal (Refereed)
    Abstract [en]

    ron and steel plants producing steel via the blast furnace-basic oxygen furnace (BF-BOF) route constitute among the largest single point CO2 emitters within the European Union (EU). As the iron ore reduction process in the blast furnace is fully dependent on carbon mainly supplied by coal and coke, bioenergy is the only renewable that presents a possibility for their partial substitution. Using the BeWhere model, this work optimised the mobilization and use of biomass resources within the EU in order to identify the opportunities that bioenergy can bring to the 30 operating BF-BOF plants.

    The results demonstrate competition for the available biomass resources within existing industries and economically unappealing prices of the bio-based fuels. A carbon dioxide price of 60 € t−1 is required to substitute 20% of the CO2 emissions from the fossil fuels use, while a price of 140 € t−1 is needed to reach the maximum potential of 42%. The possibility to use organic wastes to produce hydrochar would not enhance the maximum emission reduction potential, but it would broaden the available feedstock during the low levels of substitution.

    The scope for bioenergy integration is different for each plant and so consideration of its deployment should be treated individually. Therefore, the EU-ETS (Emission Trading System) may not be the best policy tool for bioenergy as an emission reduction strategy for the iron and steel industry, as it does not differentiate between the opportunities across the different steel plants and creates additional costs for the already struggling European steel industry.

  • 22.
    Mansikkasalo, Anna
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    Changes in European forest raw material trade: Consequences of implementing the RES2020 Directive2012In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 37, p. 150-160Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to assess possible changes in the European trade patterns of forest raw material arising from the implementation of the RES2020 Directive. The analysis is done by developing a partial general equilibrium model of the European trade in forest raw materials. The results suggest that the ambitious EU energy policy goal, stimulating the use of forest raw materials, will boost its trade. In the RES2020 scenario the total trade in by-products will increase with 61 percent – from 38 million to 61 million cubic metres solid volume compared to the baseline scenario. For logging residues the amount increases from 50 million to 104 million cubic metres solid volume – or by 110 percent in the RES2020 scenario compared to the baseline. Since the national goals in the RES2020 Directive are mandatory in contrast to the indicative recommendations stated in previous EU energy policies on renewables this study concludes that a more ambitious goal will inevitably affect the input competing industries. This stresses the need to thoroughly account for different aspects when evaluating the consequences of different policies.

  • 23.
    Matsakas, Leonidas
    et al.
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Optimization of ethanol production from high dry matter liquefied dry sweet sorghum stalks2013In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 51, p. 91-98Article in journal (Refereed)
    Abstract [en]

    The ability of sweet sorghum to be utilized as feedstock for ethanol production at high initial dry material concentration was investigated. Sweet sorghum, after being dried, was liquefacted employing commercial cellulase solution Celluclast® 1.5L, in order submerged fermentation to be permitted under high-solids concentrations. The presence of a separate enzymatic liquefaction step at 350 kg m−3 initial DM enhanced both ethanol production and productivity by 29.76% and 250%, respectively. Response surface methodology, based on the central composite design was applied to explore the combined effect of liquefaction duration and enzyme loading in order liquefaction conditions to be optimized. When the optimum conditions were tested using an enzyme load of 8.32 FPU g−1 of dry material for 8.6 h at 50 °C, high productivity (3.0 kg m−3 h−1) and final ethanol production (62.5 kg m−3) were achieved.

  • 24.
    Natarajan, E
    et al.
    Centre for New and Renewable Sources of Energy, Department of Mechanical Engineering, Anna University.
    Öhman, Marcus
    Gabra, M
    Luleå tekniska universitet.
    Nordin, A
    Energy Technology Centre, Department of Inorganic Chemistry, Umeå University.
    Liljedahl, T
    Department of Chemical Engineering and Technology, Chemical Technology, Royal Institute of Technology.
    Rao, A N
    Centre for New and Renewable Sources of Energy, Department of Mechanical Engineering, Anna University.
    Experimental determination of bed agglomeration tendencies of some common agricultural residues in fluidized bed combustion and gasification1998In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 15, no 2, p. 163-169Article in journal (Refereed)
    Abstract [en]

    Ever increasing energy demand and the polluting nature of existing fossil fuel energy sources demonstrate the need for other non-polluting and renewable sources of energy. The agricultural residues available in abundance in many countries can be used for power generation. The fluidized bed technology seems to be suitable for converting a wide range of agricultural residues into energy, due to its inherent advantages of fuel flexibility, low operating temperature and isothermal operating condition. The major ash-related problem encountered in fluidized beds is bed agglomeration which, in the worst case, may result in total defluidization and unscheduled downtime. The initial agglomeration temperature for some common tropical agricultural residues were experimentally determined by using a newly developed method based on the controlled fluidized bed agglomeration test. The agricultural residues chosen for the study were rice husk, bagasse, cane trash and olive flesh. The results showed that the initial agglomeration temperatures were less than the initial deformation temperature predicted by the ASTM standard ash fusion tests for all fuels considered. The initial agglomeration temperatures of rice husk and bagasse were more than 1000°C. The agglomeration of cane trash and olive flesh was encountered at relatively low temperatures and their initial agglomeration temperatures in gasification were lower than those in combustion with both bed materials. The use of lime as bed material instead of quartz improved the agglomeration temperature of cane trash and olive flesh in combustion and decreased the same in gasification. The results indicate that rice husk and bagasse can be used in the fluidized bed for energy generation since their agglomeration temperatures are sufficiently high.

  • 25.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jackson-Etang, Ayuk
    Mathew, Aji P.
    Jonoobi, Mehdi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanowhiskers separated from a bio-residue from wood bioethanol production2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 1, p. 146-152Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to explore the utilization of industrial bio-residues as a source of raw material for the industrial production of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chemical extraction and bleaching, and then separated to nanowhiskers by mechanical treatments such as ultrasonication, high-pressure homogenization as well as chemical acid hydrolysis.The chemical compositions and characteristics of the bio-residue were studied before and after purification using a TAPPI standard, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphology of the isolated nanowhiskers was characterized using atomic force microscope (AFM). The chemical composition of the used bio-residue was found to be 49.5 wt% cellulose, 42.1 wt% lignin and 8.4 wt% extractives. The crystallinity of the bio-residue was 14.5% and it increased to more than 73% after the purification process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diameters in the 10-20 nm range.

  • 26.
    Oller, Albert Bach
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Umeki, Kentaro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Fuel conversion characteristics of black liquor and pyrolysis oil mixtures: Efficient gasification with inherent catalyst2015In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 79, p. 155-165Article in journal (Refereed)
    Abstract [en]

    Alkali metals inherent in black liquor (BL) have strong catalytic activity during gasification. A catalytic co-gasification process based on BL with pyrolysis oil (PO) has the potential to be a part of efficient and fuel-flexible biofuel production systems. The objective of the paper is to investigate how adding PO into BL alters fuel conversion under gasification conditions. First, the conversion times of single fuel droplet were observed in a flat flame burner under different conditions. Fuel conversion times of PO/BL mixtures were significantly lower than PO and comparable to BL. Initial droplet size (300–1500 μm) was the main variable affecting devolatilization, indicating control by external heat transfer. Char oxidation was affected by droplet size and the surrounding gas composition. Then, the intrinsic reactivity of char gasification was measured in an isothermal thermogravimetric analyser at T = 993–1133 K under the flow of CO2–N2 mixtures. All the BL-based samples (100% BL, 20% PO/80% BL, and 30% PO/70% BL on mass basis) showed very high char conversion. Conversion rate of char gasification for PO/BL mixtures was comparable to that of pure BL although the fraction of alkali metal in char decreased because of mixing. The reactivities of BL and BL/PO chars were higher than the literature values for solid biomass and coal chars by several orders of magnitude. The combined results suggest that fuel mixtures containing up to 30% of PO on mass basis may be feasible in existing BL gasification technology.

  • 27.
    Ouraich, Ismail
    et al.
    Tillväxtanalys, Internationalisation and Structural Change, Östersund.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Ecosystems Services and Management, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Forsell, Nicklas
    Ecosystems Services and Management, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Lundmark, Robert
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Social Sciences.
    A spatial-explicit price impact analysis of increased biofuel production on forest feedstock markets: a scenario analysis for Sweden2018In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 119, p. 364-380Article in journal (Refereed)
    Abstract [en]

    The present paper introduces an integrated spatially explicit framework for assessing price impact on forestry markets in Sweden. The framework is based on the “soft-link” of a price determination model, the SpPDM model with the BeWhere Sweden model. The aim is to analyse the impacts of increased forest-based biofuel production for transportation within the Swedish context by 2030. To that effect, we develop scenarios analyses based on the simulations of successive biofuel production targets, under different assumptions concerning the competition intensity for forest biomass and the use of industrial by-products. The results suggest marginal impacts on the prices of forest biomass. The average across spatial-explicit prices varies from 0% to 2.8% across feedstocks and scenario types. However, the distribution of the spatial-explicit price impacts displays large variation, with price impacts reaching as high as 8.5%. We find that the pattern of spatial distribution of price impacts follows relatively well the spatial distribution of demand pressure. However, locations with the highest price impacts show a tendency of mismatch with the locations of the highest demand pressure (e.g. sawlogs). This is a counterintuitive conclusion compared to results from non-spatial economic models. The spatial-explicit structure of the framework developed, and its refined scale allows such results to be reported. Hence, from a policy-making perspective, careful analysis should be devoted to the locational linkages for forestry markets of increased biofuel production in Sweden.

  • 28.
    Panagiotou, Gianni
    et al.
    Technical University of Denmark.
    Topakas, Evangelos
    National Technical University of Athens.
    Moukouli, Maria
    National Technical University of Athens.
    Christakopoulos, Paul
    Olsson, Lisbeth
    Chalmers University of Technology.
    Studying the ability of Fusarium oxysporum and recombinant Saccharomyces cerevisiae to efficiently cooperate in decomposition and ethanolic fermentation of wheat straw2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 8, p. 3727-3732Article in journal (Refereed)
    Abstract [en]

    Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae F12 were used to ferment carbohydrates of wet exploded pre-treated wheat straw (PWS) directly to ethanol. Both microorganisms were first grown aerobically to produce cell mass and thereafter fermented PWS to ethanol under anaerobic conditions. During fermentation, soluble and insoluble carbohydrates were hydrolysed by the lignocellulolytic system of F. oxysporum. Mixed substrate fermentation using PWS and corn cobs (CC) in the ratio 1:2 was used to obtain an enzyme mixture with high cellulolytic and hemicellulolytic activities. Under these conditions, activities as high as 34300, 9100, 326, 24, 169, 27 and 254 U dm−3 of xylanase, endoglucanase, β-glucosidase, arabinofuranosidase, avicelase, feruloyl esterase and acetyl esterase, respectively, were obtained. The replacement of the enzyme production phase of F. oxysporum by the addition of commercially available enzymes Celluclast® 1.5 L FG and Novozym® 188 in 3:1 ratio for the treatment of PWS, resulted in a 3-fold increase in the volumetric ethanol productivity without increasing the ethanol production significantly. By direct bioconversion of 110 kg m−3 dry matter of PWS, ethanol concentration (4.9 kg m−3) and yield (40 g kg−1 of PWS) were similarly obtained by F. oxysporum and the mixed culture, while productivity rates as high as 34 g m−3 h−1 and 108 g m−3 h−1 were obtained by F. oxysporum and the mixed culture, respectively.

  • 29.
    Rhén, Christofer
    et al.
    Swedish University of Agricultural Sciences.
    Öhman, Marcus
    Gref, Rolf
    Swedish University of Agricultural Sciences.
    Wästerlund, Iwan
    Swedish University of Agricultural Sciences.
    Effect of raw material composition in woody biomass pellets on combustion characteristics2007In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 31, no 1, p. 66-72Article in journal (Refereed)
    Abstract [en]

    Char yield, char combustion time and char combustion rate of pellets made from different tree parts of Norway spruce and industrially made stem wood pellets of Norway spruce and Scots pine were studied. The pellets were incinerated in a laboratory scale oven at various temperatures, gas flows and oxygen concentrations. It was found that the combustion time for a single pellet mostly depended on the raw material composition and to a minor extent on the density. Pellets made of bark had up to a 50% longer char combustion time compared to that of stem wood pellets, due to differences in char yield. Industrially made stem wood pellets of pine and spruce sawdust were found to have small differences in combustion characteristics. The variations in combustion characteristics of pellets are discussed in relation to composition of raw material.

  • 30.
    Sundberg, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. RISE Research Institutes of Sweden, Department of Energy and Circular Economy, Borås, Sweden.
    Hermansson, Sven
    RISE Research Institutes of Sweden, Department of Energy and Circular Economy, Borås, Sweden. Södra Skogsägarna Ekonomisk Förening, Skogsudden, Växjö, Sweden.
    Tullin, Claes
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Traceability of bulk biomass: Application of radio frequency identification technology on a bulk pellet flow2018In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 118, p. 149-153Article in journal (Refereed)
    Abstract [en]

    Radio frequency identification (RFID) technology has been used since the 1950s in a wide range of applications. In the energy sector, there is a potential to use the technology to follow biomass fuels throughout a supply chain. In addition to logistic information, the RFID tags can be used to convey vital information of the fuel properties directly to the energy plant to be used at the moment of combustion. A detailed knowledge of the fuel composition at the moment it reaches the furnace can be used to improve energy efficiency, reduce emissions and limit problems with fouling and slagging. In this work, RFID technology was used in three separate trials to trace wood pellets, from the production site to the furnace. In the trials, RFID tags were added to batches of pellets containing 5% or 100% peat. In this way it was possible to follow the shift in pellet quality from standard pellets (100% wood) to the pellets containing the RFID tags by monitoring the change in flue gas composition. From the results it can be concluded that RFID tags indeed can be used to convey logistic information and thus information of fuel quality parameters throughout a supply chain for wood pellets. However, work on optimization is needed to design the RFID carrier properly to mix well with the pellets as illustrated in a separate trial. Finally, an economic estimate indicates that the marginal cost to implement a RFID system would be less than 1% of the total production cost of wood pellets.

  • 31.
    Tarantili, P.A.
    et al.
    National Technical University of Athens.
    Koullas, D.P.
    National Technical University of Athens.
    Christakopoulos, Paul
    Kekos, D.
    National Technical University of Athens.
    Koukios, E.G.
    National Technical University of Athens.
    Macris, B.J.
    National Technical University of Athens.
    Cross-synergism in enzymatic hydrolysis of lignocellulosics: Mathematical correlations according to a hyperbolic model1996In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 10, no 4, p. 213-219Article in journal (Refereed)
    Abstract [en]

    The effect of cross-synergism in enzymatic hydrolysis of ball-milled Avicell, alkali-treated straw cellulose (ATSC), cotton and filter paper was investigated using mixtures of Fusarium oxysporum and Neurospora crassa enzymes. The experimental data were fitted according to an empirical hyperbolic model which utilized two parameters, the maximum conversion (xmax) and the enzymatic hydrolysis time corresponding to 50% of xmax (). The model can predict conversion of polysaccharides as a function of hydrolysis time. Both model parameters were found to be strongly dependent on the crystallinity index as well as on the degree of delignification of the substrate. Up to 60% cellulose hydrolysis can be achieved when the crystallinity index of Avicell is reduced from 94.8% to 63.3%. The percentage increase of xmax due to delignification was higher than the corresponding increase of . The extent of cross-synergism depends strongly on crystallinity index and degree of delignification. This type of synergism has been found to be significant in the case of substrates which are resistant to hydrolysis, such as Avicell (with high crystallinity index) or cotton. Cross-synergistic phenomena caused by enzymatic mixtures can double cellulose hydrolysis yield with delignified straw as compared to the hydrolysis yields achieved by single-microorganism cellulases.

  • 32.
    Trubetskaya, Anna
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Department of Chemical and Biochemical Engineering, Technical University of Denmark.
    Jensen, Peter Arendt
    Department of Chemical and Biochemical Engineering, Technical University of Denmark.
    Jensen, Anker Degn
    Department of Chemical and Biochemical Engineering, Technical University of Denmark.
    Glarborg, Peter
    Department of Chemical and Biochemical Engineering, Technical University of Denmark.
    Larsen, Flemming Hofmann
    Department of Food Science, University of Copenhagen.
    Andersen, Mogens Larsen
    Department of Food Science, University of Copenhagen.
    Characterization of free radicals by Electron Spin Resonance Spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 94, p. 117-129Article in journal (Refereed)
    Abstract [en]

    The concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000°C) in biomass char have been studied. A room-temperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7·1016 and 1.5·1018 spins g−1. The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 103–104 K s−1. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g = 2.0026–2.0028) and PAH radicals (g = 2.0027–2.0031) were formed.

  • 33. Trubetskaya, Anna
    et al.
    Jensen, Peter Arendt
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Jensen, Anker Degn
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Stiebel, Markus
    Department of Mechanical Engineering, Institute for Energy Systems, Munich University of Technolog.
    Spliethoff, Hartmuth
    Department of Mechanical Engineering, Institute for Energy Systems, Munich University of Technolog.
    Glarborg, Peter
    Department of Chemical and Biochemical Engineering, Denmark Technical University.
    Larsen, Flemming Hoffmann
    Department of Food Science, Spectroscopy and Chemometrics, University of Copenhagen.
    Comparison of high temperature chars of wheat straw and rice husk with respect to chemistry, morphology and reactivity2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 86, p. 76-87Article in journal (Refereed)
    Abstract [en]

    Fast pyrolysis of wheat straw and rice husk was carried out in an entrained flow reactor at high-temperatures (1000–1500) °C. The collected char was analyzed using X-ray diffractometry, N2-adsorption, scanning electron microscopy, particle size analysis with CAMSIZER XT, 29Si and 13C solid-state nuclear magnetic resonance spectroscopy and thermogravimetric analysis to investigate the effect of inorganic matter on the char morphology and oxygen reactivity. The silicon compounds were dispersed throughout the turbostratic structure of rice husk char in an amorphous phase with a low melting temperature (≈730 °C), which led to the formation of a glassy char shell, resulting in a preserved particle size and shape of chars. The high alkali content in the wheat straw resulted in higher char reactivity, whereas the lower silicon content caused variations in the char shape from cylindrical to near-spherical char particles. The reactivities of pinewood and rice husk chars were similar with respect to oxidation, indicating less influence of silicon oxides on the char reactivity.

  • 34.
    Wagner, Katharina
    et al.
    Bioenergy 2020+ GmbH, Güssing, Austria.Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Häggström, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mauerhofer, Anna Magdalena
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Kuba, Matthias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Bioenergy 2020+ GmbH, Güssing, Austria. Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden .
    Skoglund, Nils
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hofbauer, Hermann
    Institute of Chemical, Environmental & Bioscience Engineering, TU Wien, Vienna, Austria.
    Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure2019In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, article id 105251Article in journal (Refereed)
    Abstract [en]

    Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca- and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca- and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.

  • 35.
    Wahlund, Bertil
    et al.
    Kungliga tekniska högskolan, KTH.
    Yan, Jinyue
    Westermark, Mats
    Kungliga tekniska högskolan, KTH.
    Increasing biomass utilisation in energy systems: a comparative study of CO2 reduction and cost for different bioenergy processing options2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 26, no 6, p. 531-544Article in journal (Refereed)
    Abstract [en]

    Emissions of greenhouse gases, such as CO2, need to be greatly reduced to avoid the risk of a harmful climate change. One powerful way to mitigate emissions is to switch fuels from fossil fuels to renewable energy, such as biomass. In this paper, we systematically investigate several bioenergy processing options, quantify the reduction rate and calculate the specific cost of reduction. This paper addresses the issue of which option Sweden should concentrate on to achieve the largest CO2 reduction at the lowest cost. The results show that the largest and most long-term sustainable CO2 reduction would be achieved by refining the woody biomass to fuel pellets for coal substitution, which have been done in Sweden. Refining to motor fuels, such as methanol, DME and ethanol, gives only half of the reduction and furthermore at a higher specific cost. Biomass refining into pellets enables transportation over long distances and seasonal storage, which is crucial for further utilisation of the woody biomass potential.

  • 36.
    Wiinikka, Henrik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Gebart, Rikard
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Experimental investigations of the influence from different operating conditions on the particle emissions from a small-scale pellets combustor2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 645-652Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to determine how different design parameters in an idealised small-scale combustor affect the emission of particulates in the flue gas and to provide insight that can be used for design optimisation. The design parameters are the primary air factor, the total air factor and the magnitude of swirling flow in the combustion chamber. Particles from the reactor were collected from two different sampling lines, one located in the combustion zone, just above the fuel bed, and the other in the flue stack after the reactor. The measurements show that this burner gives very low emissions of particulates and CO in the flue gas. Furthermore, the concentration of particles in the flue gas is uncoupled to the concentration of particles immediately above the fuel bed, probably as a result of a well-designed secondary air supply. The variable that had the strongest effect on the total particulate emission from the combustor was the total air factor. In order to understand the qualitative differences in the flow nature between different operating conditions, CFD simulations of the flow field were also performed.

  • 37.
    Xiong, Shaojun
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Bozaghian, Marjan
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Samuelsson, Robert
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Hellqvist, Sven
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Calcium oxide as an additive for both conservation and improvement of the combustion properties of energy grass: A preliminary study2017In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 99, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Degradation of biomass is one of the major reasons for high costs of feedstock collection, transport, and storage, which is largely associated with biomass moisture and microbial activities. Our concept is to add calcium oxide (CaO) to the biomass already when it is collected and in its natural (wet) condition. When a suitable quantity of CaO is added to moistened biomass, an alkali microenvironment will be formed with a pH exceeding 9, based on the reaction CaO + H2O ↔ Ca(OH)2. As a consequence, microbial activities are largely inhibited. The Ca(OH)2 will then successively react with CO2, following the reaction Ca(OH)2 + CO2 ↔ CaCO3 + H2O. The CaCO3 will reside in the feedstock throughout the entire production chain and end up as an additive/sorbent to improve combustion by decreasing slagging. Two experiments were conducted and proved the concept works for at least reed canary grass, but, as expected, the strength of the effect was dependent on the CaO dosage and initial biomass moisture.

  • 38. Öhman, Marcus
    et al.
    Boman, C
    Hedman, H
    Nordin, A
    Boström, D
    Slagging tendencies of wood pellet ash during combustion in residential burners2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 585-596Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems can lead to reduced accessibility of the combustion systems as well as bad publicity for the market. The objectives of the present work were to; (i) evaluate how different raw materials for pellets affect the accessibility of the existing burner equipment, (ii) determine which of the ash forming element(s) that could be responsible for the deposit/slagg formation and, (iii) estimate the critical slagging temperature for the different raw materials. Stored and fresh materials from sawdust, logging residues and bark were used as raw material in three different pellet burners. The results showed that the slagging properties were relatively sensitive to the variations in total ash content and ash forming elements of the fuel. It is therefore recommended that ash rich fuels like bark and logging residues should not be used in the existing residential pellet burners. Both fuel and burner type affected the amounts of ash deposit produced. The degree of sintering (i.e. the strength of the deposits) was mostly affected by the fuel composition. Subsequent controlled sintering test of the produced deposits/slags showed critical slagging temperatures of about 850-900 °C for stored bark and about 1000 °C for fresh bark and stored and fresh materials from sawdust and logging residues. The results further indicated that the Si-content in the fuel correlated (relatively) well to the sintering tendencies in the burners. Chemical equilibrium models were used to interpret the experimental findings, and good quantitative agreements between modelling and experimental results were generally obtained.

  • 39. Öhman, Marcus
    et al.
    Nordin, A
    Hedman, H
    Jirjis, R
    Reasons for slagging during stemwood pellet combustion and some measures for prevention2004In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 27, no 6, p. 597-605Article in journal (Refereed)
    Abstract [en]

    Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems lead to reduced accessibility of the appliances and also bad publicity for the pellet market. The objectives of the present work were therefore to: (i) determine the critical levels of the problematic ash components in stemwood pellets regarding slagging, (ii) document the variations of these problematic elements in the outgoing pellets from two pellet-mills during one operational season, (iii) determine how frequently these elements exceed the critical levels, (iv) determine how different sub-processes in the pelletising process (especially the dryer) effect the slagging properties of the pellet, and if possible (v) suggest some measures for prevention. A significant number of wood pellets reported to be problematic and problem-free, regarding slagging in ordinary residential pellet burners, were collected from the Swedish market. The ash compositions of these fuels were analysed and the results compiled in a database. Partial Least-Squares Discriminant Analysis (PLS-DA) and F-tests were used to statistically identify both the critical ash components and the critical levels of these components that separated the two reported classes. In addition, chemical equilibrium model calculations were used to interpret the findings. The variations of these elements in the in-going raw material and in the produced pellets were determined during one season in two pellet mills equipped with exhaust gas dryers. The results showed that the problematic wood-pellets had a significantly higher amount of Si, but also Al and Fe, in the fuel ash. The critical level of Si (given as SiO2) was about 20-25 wt% of the fuel ash, i.e. pellets with levels in or over this range resulted in slagging problems in residential burners. This critical Si content was exceeded once and twice for the analysed samples in the two studied pellet mills. In one of the studied mills, this was because of contamination by sand of the raw material during storage and handling, and in the other mill the reason was found to be contamination of the raw material by elutriated particles from the dryer fuel. The major conclusion of the work is that both raw materials and drying fuels/processes should be carefully treated to avoid mineral contamination, and an additional cyclone separator could potentially also be used to improve the pellet quality.

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