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  • 201.
    Bozaghian, Marjan
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Rebbling, Anders
    Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Larsson, Sylvia H.
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology, Biomass Technology Centre.
    Thyrel, Mikael
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Xiong, Shaojun
    Swedish University of Agricultural Sciences, Department of Forest Biomaterials and Technology.
    Skoglund, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Umeå University, Department of Applied Physics and Electronics, Thermochemical Energy Conversion Laboratory.
    Combustion characteristics of straw stored with CaCO3 in bubbling fluidized bed using quartz and olivine as bed materials2018Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 212, s. 1400-1408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The addition of Ca-containing compounds can reduce mass loss from agricultural biomass during storage. The resulting alkaline environment is detrimental to microorganisms present in the material. Theoretical analysis of Ca-containing biomass suggests that combustion properties are improved with respect to slagging. To validate the theoretical calculations, barley straw was utilized as a typical model agricultural biomass and combustion characteristics of straw pre-treated with 2 and 4 w/w% CaCO3 for combined improvement of storage and combustion properties were determined through combustion at 700 °C in a bench-scale bubbling fluidized-bed reactor (5 kW) using quartz and olivine sand as bed materials. The combustion characteristics were determined in terms of elemental composition and compound identification in bed ash and bed material including agglomerates, fly ash, particulate matter as well as flue gas measurements. The addition of CaCO3 to straw had both positive and negative effects on its combustion characteristics. Both additive levels raised the total defluidization temperature for both quartz and olivine, and olivine proved to be less susceptible than quartz to reactions with alkali. With Ca-additives, the composition of deposits and fine particulate matter changed to include higher amounts of KCl potentially leading to higher risk for alkali chloride-induced corrosion. Flue gas composition was heavily influenced by CaCO3 additives by significantly elevated CO concentrations likely related to increased levels of gaseous alkali compounds. The results suggest that it is necessary to reduce gaseous alkali compounds, e.g. through kaolin or sulphur addition, if alkali-rich straw is to be co-combusted with Ca-rich biomass or large amounts of Ca-additives

  • 202.
    Bracale, Antonio
    et al.
    Department for Technologies, University of Naples Parthenope.
    Carpinelli, Guido
    Department of Electrical Engineering, University of Naples Federico II.
    Gu, Irene
    Chalmers University of Technology, Department of Signals and Systems.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    A new joint sliding-window ESPRIT and DFT scheme for waveform distortion assessment in power systems2012Ingår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 88, nr 7, s. 112-120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a novel scheme that jointly employs a sliding-window ESPRIT and DFT for estimating harmonic and interharmonic components in power system disturbance data. In the proposed scheme, separate stages are utilized to estimate the voltage fundamental component, harmonics and interharmonics. This includes the estimation of the fundamental component from lowpass filtered data using a sliding-window ESPRIT, of harmonics from a sliding-window DFT with a synchronized window, and of interharmonics from the residuals by applying the sliding-window ESPRIT. Main advantages of the approach include high resolution and accuracy in parameter estimation and significantly reduced computational cost. Experiments and comparisons are made on both synthetic and measurement data. Results have shown the effectiveness and efficiency of the proposed scheme.

  • 203. Brekke, K
    et al.
    Schiavo, L Lo
    Villa, F
    Haber, A
    Kolessar, R
    Westergaard, T
    Esteves, J
    Falcäo, A
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Reti, G
    Monitoramento e regulamentação da qualidade da energia elétrica2010Ingår i: EM, s. 138-147Artikel i tidskrift (Övrigt vetenskapligt)
  • 204. Burman, Jörgen
    et al.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Influence from numerical noise in the objective function for flow design optimisation2001Ingår i: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585, Vol. 11, nr 1, s. 6-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The overall pressure drop in an axisymmetric contraction is minimised using two different grid sizes. The transition region was parameterised with only two design variables to make it possible to create surface plots of the objective function in the design space, which were based on 121 CFD calculations for each grid. The coarse grid showed to have significant numerical noise in the objective function while the finer grid had less numerical noise. The optimisation was performed with two methods, a Response Surface Model (RSM) and a gradient-based method (the Method of Feasible Directions) to study the influence from numerical noise. Both optimisation methods were able to find the global optimum with the two different grid sizes (the search path for the gradient-based method on the coarse grid was able to avoid the region in the design space containing local minima). However, the RSM needed fewer iterations in reaching the optimum. From a grid convergence study at two points in the design space the level of noise appeared to be sufficiently low, when the relative step size is 10-4 for the finite difference calculations, to not influence the convergence if the errors are below 5 per cent for this contraction geometry.

  • 205. Burman, Jörgen
    et al.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Mårtensson, H.
    Volvo Aero.
    Development of a blade geometry definition with implicit design variables2000Ingår i: AIAA Paper 00-671, American Institute of Aeronautics and Astronautics, AIAA , 2000Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a method to create 3-dimensional blade geometries defined in terms of stacked profiles where each profile is described by four NURBS curves. The NURBS representations of the profiles are attractive since they can be exchanged with CAD/CAM systems and grid generators. The blade profiles are defined in terms of traditional design variables, e.g. maximum thickness and camber. A numerical optimisation loop is then used to adjust the basic parameters of the NURBS curves until the requested values of the traditional design variables are obtained. Normally the number of traditional design variables is less than the number of NURBS parametersI.t has therefore been necessaryt o define additional constraints that make the shape corresponding to a given set of traditional design variables unique.

  • 206. Burman, Jörgen
    et al.
    Papila, Nilay
    Shyy, Wei
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Assessment of response surface-based optimization techniques unsteady flow around bluff bodies2002Ingår i: A collection of technical papers: 9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization : Atlanta, Georgia, 4 - 6 September 2002, Reston, Va.: American Institute of Aeronautics and Astronautics, AIAA , 2002Konferensbidrag (Refereegranskat)
    Abstract [en]

    The shape of a trapezoidal obstacle immersed in a 2D unsteady, viscous flow is optimized by response surface (RS) techniques based on combined criteria of minimum total drag and maximum mixing efficacy. Time-dependent Navier-Stokes computations are conducted to supply the database. In order to address the issues related to noise, an outlier analysis based on iteratively re-weighted least square (IRLS) method is applied. The results indicate that optimum designs having a low mean drag coefficient tend to be square-shaped, while designs having a large value of the mixing effectiveness are more trapezoidally-shaped. Both RS and IRLS models yield consistent designs, indicating that the present task is well handled by the techniques employed. In addition, the RS methodology is used to identify domains within the design space within which all designs are, for practical purpose, acceptable.

  • 207.
    Burström, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Energy efficiency and system independenceon condensate system for board machine atIggesund Paperboard in Workington2017Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Iggesund Paperboard in Workington have had problems with unstable heat recoveryon the condensate from dryers on the board machine. The instability in combinationof unreliable heat availability has led to dependence on heat from fresh steam. Thisproject investigates the current system performance and evaluates three suggested systemchanges. Evaluations are done with a model of the system created in Simulink. Byredirecting cold water stream from condenser M216 to shower water tank (S060) freshsteam usage can be reduced from current 25% to 14% of production time. With additionalheat from oce room heating the fresh steam usage can be reduced to 3% of productiontime. With a tap o from M216 to cooling water tank (S050) and a temperature controlthe instability is avoided.

  • 208.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Abid, Fahim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Singh, Gaurav
    Department of Electrical and Computer Engineering, Clemson University.
    Interaction between Grid-Connected PV systems and LED Lamps: Directions for Further Research on Harmonics and Supraharmonics2016Ingår i: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway, NJ, 2016, s. 193-197, artikel-id 7783479Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper discusses different approaches to investigate the interaction through harmonics, interharmonics, supraharmonics, and light flicker, between photovoltaic (PV) inverters and LED lamps in low-voltage installations. Single grid-connected power generators and electronic loads like LED lamps can be easily characterized in terms of harmonics in a given range of frequency. This subject is relatively well understood, and specific standards for measuring and restricting emissions are already established to ensure a low probability of interference. However, when connected together, source and load exhibit behavior that requires further study and understanding. This work presents a discussion serving as a guide for future work on analysis of losses and other impacts of the disturbances regarding this specific load and source interaction. The following are taken into account: the nonlinearity of LED loads and PV converters; the technologies and methods used in control; and the changes in power flow caused by load and power production variations

  • 209.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Including Uncertainties from Customer Connections in Calculating Low-Voltage Harmonic Impedance2019Ingår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 34, nr 2, s. 606-615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method is proposed in this paper to determine the harmonic impedances in low-voltage networks in a stochastic way. The consequences of resonances for harmonic propagation and stability of power converters are summarized. By using Monte Carlo simulation, the method includes the uncertainties in customer impedances, specifically due to electronic loads and local generation. The uncertainty in customer impedance is included by considering probability distribution for the resistive, inductive and capacitive parts of the impedance. The concept of transfer impedance is used for phase-to-neutral connections. A method is developed and applied to two existing low-voltage networks in Sweden. Results show that, for these two networks, the resonant frequencies decrease around 28 % once PV panels are installed. The paper includes a discussion of some of the practical aspects of applying the proposed method.

  • 210.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Supraharmonics Emission Assessment of Multi-level Converters Applied for Photovoltaic Grid-Connected Inverters2017Ingår i: The Renewable Energies and Power Quality Journal (RE&PQJ), ISSN 2172-038X, E-ISSN 2172-038X, Vol. 1, nr 15, s. 143-148, artikel-id 252Artikel i tidskrift (Refereegranskat)
  • 211.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ravindran, Vineetha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Estimation of the Consumer Electronics Capacitance for Harmonic Resonance Studies by a Non-Invasive Measurement Method2018Ingår i: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018, , s. 6Konferensbidrag (Refereegranskat)
    Abstract [en]

    Harmonic resonances in distribution systems are mainly between network inductances and shunt capacitances from capacitor banks and consumer loads. In this paper, particular attention is devoted to the evaluation of capacitances from domestic equipment, serving as a reference for resonance frequency studies. The assessment is performed by simulation and measurements of common low power electronic loads. From the analysis of EMI filters topologies used in AC/DC converters, a non-invasive capacitance measurement estimation method is presented. The method is verified after correlating capacitances with the resonance frequencies obtained from a frequency sweep method. From experimental measurements, the results show that the equivalent shunt capacitances for a set of 24 LED lamps are between 10 and 135 nF.

  • 212.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ravindran, Vineetha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jan, Meyer
    Technische Universität Dresden.
    Experimental Harmonic Analysis of the Impact of LED Lamps on PV Inverters Performance2019Ingår i: 11th Internation Conference on Electric Power Quality and Supply Reliability, Estonia, June 12-15, 2019., 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is known for instance that voltage waveform distortion and network impedance have a significant impact on PV inverter current emissions. Because this, much research is still required to better understand their behavior and impact when multiple common household devices are placed to operate together in the same low-voltage installation. In particular, this paper addresses the harmonic impact of LED lamps on PV inverters performance considering different technologies and number of lamps. The analysis has been carried out with different scenarios considering two types of LED lamps, with and without power factor correction feature, and three different PV inverter technologies. The evaluation of the impacts is simply performed by frequency and time domain analysis, establishing the correlation between the devices current harmonics. The results obtained from the experiments have shown that LED lamps are prone to add a significant impact on the PV inverter current harmonics, and this impact is mainly dependent on the devices used technology

  • 213.
    Börjesson, Pål
    et al.
    Lunds universitet.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ahlgren, Serina
    Sveriges Lantbruksuniversitet.
    Nyström, Ingrid
    f3 och CIT Industriell Energi.
    Dagens och framtidens hållbara biodrivmedel: Underlagsrapport från f3 till utredningen om FossilFri Fordonstrafik2013Rapport (Refereegranskat)
  • 214.
    Bülow, M.
    et al.
    TU Dortmund, Dortmund, Germany.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, C.
    TU Dortmund, Dortmund, Germany.
    Incorporating a concentration-dependent dielectric constant into ePC-SAFT. An application to binary mixtures containing ionic liquids2019Ingår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 492, s. 26-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Primitive thermodynamic models for electrolyte solutions require the dielectric constant ε. This property strongly depends on the concentration of the electrolytes in the mixture. Neglecting this dependency might be reasonable for modeling solutions at low electrolyte concentrations. However, in solutions containing ionic liquids (ILs) and especially for the calculation of liquid-liquid equilibria (LLE) of systems with ILs, liquid phases often contain high IL concentrations. At such conditions, neglecting the influence of concentration on ε is an oversimplification. In this work, an approach to account for the concentration-dependent dielectric constant within the Debye-Hückel theory was implemented into electrolyte Perturbed-Chain Statistical Associating Fluid Theory (original ePC-SAFT). This new approach was then applied to model LLE of binary mixtures containing water and commonly used hydrophobic ILs. These common ILs are comprised of the IL-cations [C n mim] + , [C n py] + , [C n mpy] + , [C n mpyr] + , [C 4 m 4 py] + and the IL-anions [BF 4 ] - , [NTf 2 ] - , [PF 6 ] - , [TFO] - . The LLE of binary mixtures water + IL were modeled at ambient pressure and different temperatures with the new ePC-SAFT and with the original ePC-SAFT [Ji et al. DOI: 10.1016/j.fluid.2012.05.029] without the concentration-dependent ε. Overall, the new approach within ePC-SAFT shows superior modeling as well as correlation capability compared to original ePC-SAFT, which was concluded by comparing both models with LLE data from literature. 

  • 215.
    Carlborg, Marcus
    et al.
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Boström, Dan
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Backman, Rainer
    Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Reactions Between Ash Forming Elements and Two Mullite Based Refractories in Entrained Flow Gasification of Wood2014Konferensbidrag (Refereegranskat)
  • 216.
    Carlborg, Markus
    et al.
    Umeå universitet.
    Boström, Dan
    Umeå universitet.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Backman, Rainer
    Umeå universitet.
    Reactions between ash and ceramic lining in entrained flow gasification of wood: exposure studies and thermodynamic considerations2013Ingår i: Proceedings of the 21st EU BC&E - Copenhagen 2013, Florence Italy, 2013, s. 446-449Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Gasification of biomass in the entrained flow process requires temperatures above 1000°C and pressures above 20 bar. Together with the ash forming elements, a harsh environment is created inside these reactors and degradation of construction material is likely to occur. This will lead to unplanned stops and increased maintenance work resulting in economic loss. In this work, two refractory materials (63 and 83 weight percent alumina) were exposed to synthetic ash composed of K2CO3, CaCO3 and SiO2 to study chemical attack on and interactions with the refractory materials. The exposure went on for 7 days in 1050°C and CO2­atmosphere in a muffle furnace. It was found that potassium (K) is the most active element in attack of the refractories and is transported fastest in the material. A melt composed of K, Ca and Si was formed that prevented penetration of K but it also dissolved aluminum from the refractory materials. X­ray diffraction showed that the crystalline phases leucite, kalsilite, kaliophilite, K(2­x)Al(2­x) SixO4 and wollastonite had formed. Formations of new phases in refractories will cause stress and eventually failure within refractories.

  • 217.
    Carlborg, Markus
    et al.
    Energy Technology and Thermal Process Chemistry, Department of Applied Physics and Electronics, Umeå University.
    Weiland, Fredrik
    RISE Energy Technology Center.
    Ma, Charlie
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Backman, Rainer
    Energy Technology and Thermal Process Chemistry, Department of Applied Physics and Electronics, Umeå University.
    Landälv, Ingvar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. RISE Energy Technology Center.
    Exposure of refractory materials during high-temperature gasification of a woody biomass and peat mixture2018Ingår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, nr 2, s. 777-787Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finding resilient refractory materials for slagging gasification systems have the potential to reduce costs and improve the overall plant availability by extending the service life. In this study, different refractory materials were evaluated under slagging gasification conditions. Refractory probes were continuously exposed for up to 27 h in an atmospheric, oxygen blown, entrained flow gasifier fired with a mixture of bark and peat powder. Slag infiltration depth and microstructure were studied using SEM EDS. Crystalline phases were identified with powder XRD. Increased levels of Al, originating from refractory materials, were seen in all slags. The fused cast materials were least affected, even though dissolution and slag penetration could still be observed. Thermodynamic equilibrium calculations were done for mixtures of refractory and slag, from which phase assemblages were predicted and viscosities for the liquid parts were estimated.

  • 218.
    Carlsson, Isak
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kartläggning och energieffektivisering: KV61, Gärstadverket Linköping2019Självständigt arbete på grundnivå (yrkesexamen), 180 hpStudentuppsats (Examensarbete)
  • 219.
    Carlsson, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Entrained flow black liquor gasification: detailed experiments and mathematical modelling2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Black liquor, a by-product from the Kraft pulping process is a highly viscous fluid consisting of approximately 30% water, 30 % alkali salts and 40 % combustible material. The alkali salts originating from the pulp making process need to be recovered in order for the pulp mill to be economical and to satisfy environmental regulation. Currently, the recovery takes place in a large boiler called Tomlinson recovery boiler named after its inventor. However, a more energy efficient way to recover the chemicals could be via gasification in a pressurized, entrained flow, high temperature gasifier. To demonstrate this technology a development plant (DP1) was built in 2005 by the technology vendor Chemrec. Since then, the plant has been running for more than 10 000 h and frequently been updated and optimized. As steps towards commercialization and scale–up different computational models of varying sophistication are used as design and optimization tools for the process. Still, the engineering tools can only provide sensible predictions if they are properly validated and verified. This licentiate thesis is concerned with validation of a comprehensive mathematical model based on Computational Fluid Dynamics (CFD) describing the gasification reactor and experimental investigations of the process characteristics in the DP1 gasifier. Paper A describes the system design and methodology for high temperature gas sampling during pressurized black liquor gasification. In this work a water-cooled gas sampling probe is installed in the hot part of the DP1 gasification reactor and several gas samples are withdrawn and analyzed. The experimentally obtained data in Paper A are then used as validation data for the CFD-model described in Paper B. In Paper C the obtained data from Paper A are thoroughly analyzed and the influence of reactor operation on producer gas composition is determined. In Paper D black liquor sprays from a gas assisted nozzle is experimentally investigated using high speed photography. Furthermore, the particle content in the cooled producer gas is measured using a particle sizing impactor. The obtained results in Paper D can be used to explain some of the observations in Paper A.

  • 220.
    Carlsson, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Large scale experiments and modeling of black liquor gasification2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Biomass gasification could provide a basis for increased electricity and engine fuel production from a renewable source in the pulp and paper industry. This work focuses on the largest byproduct available at the pulp mills, black liquor. Black liquor is a mixture of spent cooking chemicals, dissolved lignin, dissolved carbohydrates and a small portion of inorganic compounds found in the wood. The conventional technology to recover the cooking chemicals and the chemical energy as heat is combustion in large boilers. Here, gasification could be an alternative, replacing or complementing the boilers. The gasification technology produces a combustible gas that can be cleaned to produce electricity in a gas turbine/engine or, be synthesized into valuable chemicals or liquid engine fuels. The technology has been demonstrated in development scale since 2005 and appears to be promising. Still, commercial plants have not yet been built. This thesis focuses on the understanding of the oxygen blown, pressurized, entrained flow, black liquor gasification technology. The main goals have been to increase the understanding about the dominating mechanisms in black liquor gasification and to develop an engineering tool that can be used to design and optimize, pressurized, entrained flow, black liquor gasifiers. To accomplish these goals gas samples were extracted from the gasification reactor using a gas sampling probe that was developed within this work. Gas samples were also collected downstream the quench located underneath the reactor and the results were compared. Finally, an existing numerical model was developed so it can predict the behavior of the black liquor gasifier within reasonable accuracy.Even though the actual mechanisms in the reactor and quench are very complex it appears that they can be described with relatively simple global mechanisms. The main gas components are dictated by the water gas shift reaction. At the outlet of the reactor the gas composition is not in global thermodynamic equilibrium. However, the main gas components are close to partial equilibrium whilst CH4 and H2S are not. Very little of the available CH4 is reformed outside the flame region and the primary consumption occurs in the flame through oxidation and reformation. When the system pressure is increased, H2S concentration in the gas will increase, the same will happen if the oxygen-fuel ratio is decreased. In the quench, the primary spray flow rate/load (mass flow of black liquor and oxygen) ratio has a critical value of about 0.6 below which the gas concentration of CO2, CO, and H2, is significantly changed. The H2/CO ratio can be changed from about 1.15 to 1.4 by changing the primary spray flow rate/load ratio. The mechanism is associated with the water gas shift reaction and the quenching rate of the gas stream. The computational fluid dynamics reactor model predicts most of the trends when operating conditions are changed and is in good agreement with the experimental results with respect to gas composition and char carbon conversion.

  • 221.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grönberg, Carola
    Energy Technology Centre, Piteå.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Risberg, Mikael
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Spatially resolved measurements of gas composition in a pressurised black liquor gasifier2009Ingår i: Environmental Progress & Sustainable Energy, ISSN 1944-7442, E-ISSN 1944-7450, Vol. 28, nr 3, s. 316-323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Black liquor gasification is a new process for recovery of energy and chemicals in black liquor from the Kraft pulping process. The process can be combined with catalytic conversion of syngas into motor fuels. The potential for motor fuel production from black liquor in Sweden is to replace about 25% of the current consumption of gasoline and diesel. For Finland the figure is even higher while for Canada it is about 14% and for the USA about 2%.

  • 222.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Iisa, Kristiina
    National Renewable Energy Laboratory.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Computational fluid dynamics simulations of raw gas composition from a black liquor gasifier: comparison with experiments2011Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, nr 9, s. 4122-4128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized entrained flow high temperature black liquor gasification can be used as a complement or a substitute to the Tomlinson boiler used in the chemical recovery process at kraft pulp mills. The technology has been proven on the development scale, but there are still no full scale plants. This work is intended to aid in the development by providing computational tools that can be used in scale up of the existing technology. In this work, an existing computational fluid dynamics (CFD) model describing the gasification reactor is refined. First, one-dimensional (1D) plug flow reactor calculations with a comprehensive reaction mechanism are performed to judge the validity of the global homogeneous reaction mechanism used in the CFD simulations in the temperature range considered. On the basis of the results from the comparison, an extinction temperature modification of the steam-methane reforming reaction was introduced in the CFD model. An extinction temperature of 1400 K was determined to give the best overall agreement between the two models. Next, the results from simulations of the flow in a 3 MW pilot gasifier with the updated CFD model are compared to experimental results in which pressure, oxygen to black liquor equivalence ratio, and residence time have been varied. The results show that the updated CFD model can predict the main gas components (H2, CO, CO2) within an absolute error of 2.5 mol %. CH4 can be predicted within an absolute error of 1 mol %, and most of the trends when process conditions are varied are captured by the model.

  • 223.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Iisa, Kristiina
    National Renewable Energy Laboratory, Golden, Colorado.
    High-speed imaging of biomass particles heated with a laser2013Ingår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 103, s. 278-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work two types of lignocellulosic biomass particles, European spruce and American hardwood (particle sizes from 100 μm to 500 μm) were pyrolysed with a continuous wave 2 W Nd:YAG laser. Simultaneously a high-speed camera was used to capture the behavior of the biomass particle as it was heated for about 0.1 s. Cover glasses were used as a sample holder which allowed for light microscope studies after the heating. Since the cover glasses are not initially heated by the laser, vapors from the biomass particle are quenched on the glass within about 1 particle diameter from the initial particle. Image processing was used to track the contour of the biomass particle and the enclosed area of the contour was calculated for each frame.The main observations are: There is a significant difference between how much surface energy is needed to pyrolyses the spruce (about 75% more) compared to the hardwood. The oil-like substance which appeared on the glass during the experiment is solid at room temperature and shows different levels of transparency. A fraction of this substance is water soluble. A brownish coat is seen on the unreacted biomass. The biomass showed insignificant swelling as it was heated. The biomass particle appears to melt and boil at the front that is formed between the laser beam and the biomass particle. The part of the particle that is not subjected to the laser beam seems to be unaffected.

  • 224.
    Carlsson, Per
    et al.
    Energy Technology Centre, Piteå.
    Ma, Charlie
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Molinder, Roger
    Energy Technology Centre, Piteå.
    Weiland, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Öhrman, Olov
    Energy Technology Centre, Piteå.
    Slag Formation During Oxygen Blown Entrained-Flow Gasification of Stem Wood2014Ingår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 28, nr 11, s. 6941-6952, artikel-id 28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Stem wood powders were fired in a mullite-lined pilot-scale oxygen-blown pressurized entrained-flow gasifier. During repeated campaigns involving increases in fuel load and process temperature, slag formations that eventuated in the blockage of the gasifier outlet were observed. These slags were retrieved for visual and chemical characterization. It was found that the slags had very high contents of Al and, in particular, high Al/Si ratios that suggest likely dissolution of the mullite-based refractory of the gasifier lining due to interactions with the fuel ash. Possible causes for the slag formation and behavior are proposed, and practical implications for the design of future stem wood entrained-flow gasifiers are also discussed

  • 225.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Furusjö, Erik
    Chemrec.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Black liquor gasification: CFD model predictions compared with measurements2010Ingår i: 2010 International Chemical Recovery Conference Proceedings, Norcross, GA: TAPPI Press, 2010, Vol. 2, s. 160-171Konferensbidrag (Refereegranskat)
  • 226.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Furusjö, Erik
    Chemrec.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Experiments and mathematical models of black liquor gasification: influence of minor gas components on temperature, gas composition, and fixed carbon conversion2010Ingår i: TAPPI Journal, ISSN 0734-1415, Vol. 9, nr 9, s. 15-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, predictions from a reacting Computational Fluid Dynamics (CFD) model of a gasification reactor are compared to experimentally obtained data from an industrial pressurized black liquor gasification plant. The data consists of gas samples taken from the hot part of the gasification reactor using a water cooled sampling probe. During the considered experimental campaign, the oxygen-to-black liquor equivalence ratio (λ) was varied in three increments, which resulted in a change in reactor temperature and gas composition. The presented numerical study consists of CFD and thermodynamic equilibrium calculations in the considered λ-range using boundary conditions obtained from the experimental campaign. Specifically, the influence of methane concentration on the gas composition is evaluated using both CFD and thermodynamic equilibrium. The results show that the main gas components (H2, CO, CO2) can be predicted within a relative error of 5% using CFD if the modeled release of H2S and CH4 are specified a priori. In addition, the calculations also show that the methane concentration has large influence on the reactor outlet temperature and final carbon conversion.

  • 227.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Marklund, Magnus
    Energy Technology Centre, Piteå.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Comparison and validation of gas phase reaction schemes for black liquor gasification modeling2008Ingår i: Conference Proceedings 2008 AiChE annual meeting: Advances in gasification research, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Pressurized Entrained-flow High Temperature Black Liquor Gasification (PEHT-BLG) is a potential substitute or complement to the recovery boiler traditionally used for the recovery of chemicals and energy in black liquor in the Kraft pulping process. Black liquor consists of roughly 30 % moisture, 35 % inorganic pulping chemicals and 35 % combustible material (i.e. lignin). The PEHT-BLG technology can give an increase in total energy efficiency of the mill and provide new products with high added value, such as green motor fuels. The main parts of the recovery unit in the process are; a slagging refractory lined entrained-flow gasification reactor, with a gas assisted burner nozzle producing small black liquor droplets, used for direct gasification of the black liquor at about 1000 °C to produce a ‘raw' syngas and a liquid smelt containing mainly Na2CO3 and Na2S; a quench cooler beneath the reactor where the product gas and smelt are separated and the smelt is dissolved in water forming green liquor; a counter current condenser (CCC) that cools the syngas and condenses water vapor and any volatile and tar species that may be present. The heat recovered from the gas condensation is used to generate low/medium pressure steam that can be used in the pulp and paper process. Furthermore, the chemicals in the green liquor are recovered as cooking chemicals in the downstream processing. Due to lack of demonstration of long term operation of the technology, a development (pilot) plant for PEHT-BLG (named DP-1) with a capacity of 20 tones dry solids/24h is in operation by the technology vendor Chemrec AB at the Energy Technology Centre in Piteå, Sweden. An important tool for reduction of the technical risk associated with scale up of new technology is a comprehensive CFD model for the PEHT-BLG reactor. The current model includes drying, pyrolysis, char gasification and smelt formation of black liquor droplets as well as a simplified gas phase reaction mechanism. The current model has been validated against the outlet gas composition after the Counter Current Condenser (CCC). The model predicted a CO / CO2 ratio that was approximately 50% higher compared to the measurements. However, it is possible that the well known water-gas shift reaction is active in the quench and this could explain that the experimentally determined gas composition after the CCC differs from the computational results at the outlet from the hot zone. Recently, in-situ measurements have been performed in the DP-1 reactor and a further validation of the model has been made possible. The measurements have been performed by sampling gas with a water-cooled suction probe from the lower part of the hot zone, followed by offline gas analyses. The present paper investigates the difference between the current CFD-model and a modified version with an additional CO + O2 reaction added to the simplified gas phase reaction scheme. The simulation results are compared against measurements obtained by the gas sampling probe in the DP-1 reactor. The results suggest that by implementing the additional CO + O2 reaction local flame temperature was increased significantly. However, the effect on volume average and outlet gas temperature was minimal.The results also showed that the CO + O2 reaction had very little effect on outlet gas composition when the reaction was implemented in the PEHT-BLG-CFD model

  • 228.
    Carvalho, Lara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Opportunities to broaden biomass feedstocks in thermochemical conversion technologies2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Global environmental concerns are motivating a growing interest in broadening the biomass feedstock base in several energy sectors, including (i) the domestic heating sector, presently dominated by stem wood combustion, and (ii) biofuel production, presently dominated by edible crops. The objective of this thesis is to investigate new opportunities to broaden the biomass feedstock in thermochemical conversion technologies. The performance of different feedstocks was therefore investigated for (i) heat production in small-scale combustion systems and (ii) biofuel production in large-scale gasification-based plants. The selected feedstocks were agricultural residues, forest wood, pyrolysis liquid and industrial by-products, such as lignin, black liquor, crude glycerol and fermentation residues.

    The alkali metals content in biomass has an important role in combustion and gasification. Alkali metals can cause ash-related problems in small-scale combustion systems, while they can catalyse gasification reactions thus increasing conversion efficiency. Keeping this effect in mind, the present investigation was based on combustion tests with pelletised agricultural residues (non-woody feedstocks with ash contents of 3-8 wt% on a dry basis) to evaluate their combustion feasibility in several small-scale appliances. Moreover, the potential techno-economic benefits of alkali addition in gasification-based biofuel plants were investigated in two different systems: (i) stand-alone biofuel plant operated with wet-alkali-impregnated forest residues and alkali-rich lignin as well as (ii) biofuel plant integrated with a Kraft pulp mill operated with black liquor (an inherently alkali-rich feedstock) mixed with different blend ratios of pyrolysis liquid, crude glycerol or fermentation residues (co-gasification concept). The techno-economic analysis in large-scale entrained-flow-gasification-based biofuel plants was made with the help of simulation tools.

    The combustion tests have shown that high alkali feedstocks lead to problems with ash accumulation and slag formation in small-scale appliances. The results indicated that non-woody feedstocks can only be burned in appliances adapted to manage high ash content feedstocks. Effective ash cleaning and enhanced combustion controlling mechanisms are relevant characteristics to have in appliances when using these feedstocks. It has been shown that four out of the seven selected feedstocks can be burned in small-scale appliances, while fulfilling the legal European requirements (EN 303-5:2012) in terms of combustion efficiency and emissions. The nitrogen content and ash composition were shown to be important parameters to evaluate whether a feedstock can be utilised in small-scale combustion appliances.

    The techno-economic investigations of the gasification-based biofuel plants have shown that alkali impregnation is an attractive option to increase energy performance and downstream biofuel production. The economic assessment has indicated that alkali impregnation does not significantly increase biofuel production costs, while it allows the application of a new syngas cleaning system that can significantly reduce biofuel production costs. The present study has shown that the vi co-gasification concept has also techno-economic benefits as a result of the (i) alkali content in black liquor and (ii) economy-of-scale effects. These benefits can be enhanced by choosing energy-rich and low-cost blend-in feedstocks. The gasification-based biofuel production routes hereby investigated exhibit a good economic performance since biofuel required selling prices were economically competitive with other biofuel production routes as well as with taxed gasoline.

  • 229.
    Carvalho, Lara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Small-scale combustion of agricultural biomass fuels2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The ambitious targets of the European Union in increasing the use of renewable energies to 20% of Europe’s energy needs, call for urgent changes, including in the biomass sector. The share of solid biomass for heating purposes could be further increased by replacing oil- and gas-fired furnaces with biomass boilers and by expanding the spectrum of biomass raw materials for small-scale combustion systems. The interest in using non-woody biomass fuels for heat production has been increasing in Europe due to two main factors. First, the market for fossil fuels is unstable and their prices are continuously rising. Second, the increase competition for woody biomass between the heating sector and other industries, have increased the price of wood. As a result, the interest for alternative biomass fuels is growing rapidly, covering woody materials of low quality, energy crops and forest residues.The present work aims at investigating the technical feasibility of using non-woody biomass fuels in existing small-scale combustion appliances developed for burning wood. Therefore, combustion tests with different non-woody biomass fuels and in different combustion appliances were performed in standard laboratory conditions and in households under real life conditions (field tests). The laboratory tests were performed using eight different fuels (straw, Miscanthus, maize, vineyard pruning, hay, wheat bran and Sorghum) while in the field tests straw, Miscanthus and maize were burned. The gaseous and particle emissions, the slag tendency and the efficiency of the combustion systems operated with non-woody biomass fuels were analysed and when possible compared with the legal requirements defined in FPrEN 303-5. The limitations of the investigated combustion appliances when operated with non-woody biomass fuels were analysed and discussed.Non-woody biomass fuels could be used for heat production in existing combustion appliances as long as the systems are adapted for burning high ash content fuels. Among the investigated fuels, Miscanthus, vineyard pruning and hay could be burnt in most of the tested combustion appliances while fulfilling the legal European requirements (defined in FprEN303-5) in terms of emissions and efficiency. The non-woody biomass fuels showed problems with ash accumulation and slag formation and could only be burned without unwanted shutdowns in combustion appliances adapted to manage high ash content fuels. Straw, wheat bran and maize were the most problematic fuels regarding slagging. The combustion appliances require appropriate technological developments to manage the strong variability in terms of chemical and thermal properties of the non-woody biomass fuels. The results of the laboratory tests were generally in agreement with the field test results.

  • 230.
    Carvalho, Lara
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kirtania, Kawnish
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Anheden, Marie
    Innventia AB.
    Wolf, Jens
    Innventia AB.
    Techno-economic assessment of catalytic gasification of biomass powders for methanol production2017Ingår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 237, s. 167-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study evaluated the techno-economic performance and potential benefits of methanol production through catalytic gasification of forest residues and lignin. The results showed that while catalytic gasification enables increased cold gas efficiencies and methanol yields compared to non-catalytic gasification, the additional pre-treatment energy and loss of electricity production result in small or no system efficiency improvements. The resulting required methanol selling prices (90-130 €/MWh) are comparable with production costs for other biofuels. It is concluded that catalytic gasification of forest residues can be an attractive option as it provides operational advantages at production costs comparable to non-catalytic gasification. The addition of lignin would require lignin costs below 25 €/MWh to be economically beneficial.

  • 231.
    Carvalho, Lara
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. IVL – Swedish Environmental Institute, Stockholm, Sweden.
    Ma, Chunyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Öhrman, Olov G. W.
    IVL – Swedish Environmental Institute, Stockholm, Sweden;RISE Energy Technology Center AB, Piteå, Sweden.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning: Part 2: Techno-economic analysis2018Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 165, nr Part B, s. 471-482Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning systemcomprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reductionwith zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol productionallowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantagederived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

  • 232.
    Carvalho, Lara
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wetterlund, Elisabeth
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wolf, Jens
    RISE Bioeconomy.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Methanol production via black liquor co-gasification with expanded raw material base: Techno-economic assessment2018Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 225, s. 570-584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Entrained flow gasification of black liquor combined with downstream-gas-derived synthesis of biofuels in Kraft pulp mills has shown advantages regarding energy efficiency and economic performance when compared to combustion in a recovery boiler. To further increase the operation flexibility and the profitability of the biofuel plant while at the same time increase biofuel production, black liquor can be co-gasified with a secondary feedstock (blend-in feedstock). This work has evaluated the prospects of producing biofuels via co-gasification of black liquor and different blend-in feedstocks (crude glycerol, fermentation residues, pyrolysis liquids) at different blend ratios. Process modelling tools were used, in combination with techno-economic assessment methods. Two methanol grades, crude and grade AA methanol, were investigated. The results showed that the co-gasification concepts resulted in significant increases in methanol production volumes, as well as in improved conversion efficiencies, when compared with black liquor gasification; 5-11 and 4-10 percentage point in terms of cold gas efficiency and methanol conversion efficiency, respectively. The economic analysis showed that required methanol selling prices ranging from 55-101 €/MWh for crude methanol and 58-104 €/MWh for grade AA methanol were obtained for an IRR of 15%. Blend-in led to positive economies-of-scale effects and subsequently decreased required methanol selling prices, in particular for low cost blend-in feedstocks (prices below approximately 20 €/MWh). The co-gasification concepts showed economic competitiveness to other biofuel production routes. When compared with fossil fuels, the resulting crude methanol selling prices were above maritime gas oil prices. Nonetheless, for fossil derived methanol prices higher than 80 €/MWh, crude methanol from co-gasification could be an economically competitive option. Grade AA methanol could also compete with taxed gasoline. Crude glycerol turned out as the most attractive blend-in feedstock, from an economic perspective. When mixed with black liquor in a ratio of 50/50, grade AA methanol could even be cost competitive with untaxed gasoline.

  • 233.
    Carvalho, Lara
    et al.
    Bioenergy 2020+ GmbH.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wopienka, Elisabeth
    Bioenergy 2020+ GmbH.
    Challenges in small-scale combustion of agricultural biomass fuels2008Ingår i: International Journal of Energy for a Clean Environment, ISSN 2150-3621, E-ISSN 2150-363X, Vol. 9, nr 1-3, s. 127-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Straw, Miscanthus, maize, and horse manure were reviewed in terms of fuel characteristics. They were tested in existing boilers, and the particulate and gaseous emissions were monitored. The ash was analyzed for the presence of sintered material. All the fuels showed problems with ash lumping and slag formation. Different boiler technologies showed different operational performances. Maize and horse manure are problematic fuels regarding NOx and particulate emissions. Miscanthus was the best fuel tested. Due to the big variation of fuel properties and therefore combustion behavior of agricultural biomass, further R&D is required to adapt the existing boilers for these fuels.

  • 234.
    Carvalho, Lara
    et al.
    Austrian Bioenergy Centre.
    Lundgren, Joakim
    Wopienka, Elisabeth
    Austrian Bioenergy Centre.
    Öhman, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Challenges in small-scale combustion of agricultural biomass fuels2007Ingår i: 9th Conference on Energy for a Clean Environment: Clean Air 2007, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the present work, several agricultural biomass fuels, namely straw, Miscanthus,maize whole crop and horse manure mixed with two bedding materials, woodshavings and straw, were reviewed in terms of fuel characteristics. Furthermore,these fuels were tested in several existing boiler technologies and the particulateand gaseous emissions were monitored. The ash was analysed visually in terms ofpresence of sintered material. As expected, all the fuels showed problems withash lumping and slag formation, especially straw and horse manure. Differentboiler technologies showed different operational performance regarding ash andslag management. Miscanthus was the best fuel tested regarding emissions. Maizeand horse manure are problematic fuels regarding NOx and particulate emissions.Due to the big variation of the fuel properties and therefore combustion behaviourof agricultural biomass, further R&D is required to adapt the existing small-scalecombustion systems for these new fuels. Improvements in the combustionchamber design, controlling technology and ash removal systems of small-scalecombustion systems are therefore essential.

  • 235.
    Carvalho, Lara
    et al.
    Bioenergy 2020+ GmbH.
    Vopienka, Elisabeth
    Bioenergy 2020+ GmbH.
    Pointner, Christian
    Bioenergy 2020+ GmbH.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Verma, Vijay Kumar
    Bioenergy 2020+ GmbH.
    Haslinger, Walter
    Bioenergy 2020+ GmbH.
    Schmidl, Christoph
    Bioenergy 2020+ GmbH.
    Performance of a pellet boiler fired with agricultural fuels2013Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 104, s. 286-296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing demand for woody biomass increases the price of this limited resource, motivating the growing interest in using woody materials of lower quality as well as non-woody biomass fuels for heat production in Europe. The challenges in using non-woody biomass as fuels are related to the variability of the chemical composition and in certain fuel properties that may induce problems during combustion. The objective of this work has been to evaluate the technical and environmental performance of a 15 kW pellet boiler when operated with different pelletized biomass fuels, namely straw (Triticum aestivum), Miscanthus (Miscanthus × giganteus), maize (Zea mays), wheat bran, vineyard pruning (from Vitis vinifera), hay, Sorghum (Sorghum bicolor) and wood (from Picea abies) with 5% rye flour. The gaseous and dust emissions as well as the boiler efficiency were investigated and compared with the legal requirements defined in the FprEN 303-5 (final draft of the European standard 303-5). It was found that the boiler control should be improved to better adapt the combustion conditions to the different properties of the agricultural fuels. Additionally, there is a need for a frequent cleaning of the heat exchangers in boilers operated with agricultural fuels to avoid efficiency drops after short term operation. All the agricultural fuels satisfied the legal requirements defined in the FprEN 303-5, with the exception of dust emissions during combustion of straw and Sorghum. Miscanthus and vineyard pruning were the best fuels tested showing comparable emission values to wood combustion.

  • 236.
    Castro, Guillermo
    et al.
    Inelectra, Caracas.
    Bermúdez, Juan
    Universidad Simón Bolívar, Caracas.
    Jimenez, Manuel
    Universidad Simón Bolívar, Caracas.
    Alvarez, Manuel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Arreaza, Alex
    Derwick Associates of Venezuela.
    AVRs and PSSs Revisited2015Ingår i: 2015 9th International Conference on Electrical and Electronics Engineering: ELECO 2015, Bursa, Turkey, 26 - 28 November 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 1006-1010, artikel-id 7394473Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper a conceptual analysis on the effect ofAutomatic Voltage Regulators (AVR) and Power SystemStabilizers (PSS) for small signal stability (SSS) of powersystems is developed. A modal formulation approachincluding the use of the Participation Matrix is used. TheModal Formulation is performed considering synchronousgenerator (SG) equations for both the Electromotive Forces(EMF) model and the Flux Linkages (FL) model as well asAVR and PSS equations. Then, a selected study case isevaluated to study the effect of the AVR and PSS on thesmall signal stability. For pedagogical purposes acomparison between the basic RLC circuit and asynchronous generator connected to an infinite bus, toclarify the concepts of synchronizing torque and dampingtorque, is presented.1. Introduction

  • 237.
    Chan, Fan Liang
    et al.
    Catalysis for Green Chemicals Group, Department of Chemical Engineering, Monash University.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Tanksale, Akshat
    Catalysis for Green Chemicals Group, Department of Chemical Engineering, Monash University.
    Kinetic Study of Catalytic Steam Gasification of Biomass by Using Reactive Flash Volatilisation2015Ingår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 7, nr 8, s. 1329-1337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reactive flash volatilisation is an autothermal process to convert biomass into tar-free synthesis gas under steam-rich conditions. This article studies the kinetics of reactive flash volatilisation by using Ni, Pt[BOND]Ni, Ru[BOND]Ni, Re[BOND]Ni, and Rh[BOND]Ni catalysts supported on alumina. The rates of mass loss of cellulose, xylan, and lignin were measured and compared with those of the synthetic biomass mixture and pinewood sawdust. The kinetic parameters were calculated with and without catalysts by using a wire-mesh isothermal thermogravimetric analyser in an equimolar steam/N2 atmosphere and high heating rates of 8.6×102, 1.1×103, and 1.3×104 °C min−1 at 700, 750, and 800 °C, respectively. The results revealed three distinct regimes of the rate of mass loss: pyrolytic decomposition, reforming, and char gasification. The catalysts increased the rate of mass loss in the reforming regime. Rh[BOND]Ni and Ru[BOND]Ni supported catalysts showed higher reforming rates than other catalysts. This study provides direct evidence of the in situ catalytic removal of tar during gasification of biomass

  • 238.
    Chang, G.W.
    et al.
    National Chung Cheng University.
    Ranade, S
    New Mexico State University.
    Watson, N.R.
    University of Canterbury.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Monitoring issues and analysis techniques: smart grid aspect of power quality2012Ingår i: 15th International Conference on Harmonics and Quality of Power (ICHQP), IEEE Communications Society, 2012, s. 673-677Konferensbidrag (Refereegranskat)
    Abstract [en]

    In recent years, many countries have started to integrate the power system with more advanced information and communication technologies. With transforming the electrical data to useful information, the stability and reliability of power system operation can be secured. By observing this world-wide trend, it is believed that the development of smart grid would be the vital strategy for energy saving, integration of renewable energy resources, and improvement of power quality. Meanwhile, the related measuring and control equipments are necessary to redesign based on information and communication technologies (ICT), which are key factors to the success of the smart grid implementation. This paper gives an overview of some important issues and techniques for the enhancement of power quality monitoring and analysis when deploying the smart grid.

  • 239.
    Chen, Jingjing
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Wang, Changsong
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Mechanism Study of Heat Transfer Enhancement Using Twisted Hexagonal Tube with Slurry from Biogas Plant2017Ingår i: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, s. 880-885Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Waste-heat recovery from discharged slurries is important to improve the biogas production efficiency but still remains challenge duo to the special properties of slurries in anaerobic digestion process. In this work, numerical study was carried out to investigate the flow field, and heat transfer performance of slurry from biogas plant in the twisted hexagonal and other twisted tubes was simulated with computer fluid dynamic (CFD) for the first time. The numerical method was validated with experimental data from the literature. The heat transfer performance and flow resistance of twisted hexagon tube were calculated and compared with other types of twisted tubes. The enhancement factor of the twisted hexagonal tube reached to 2 and kept optimum at turbulence flow region compared to the twisted tubes with square and elliptical cross section. Meanwhile, the mechanism of heat transfer enhancement with different twisted tubes was further studied, and the optimal field synergy and minimum local circulation flow near the wall are the main reasons for the high performance and low flow resistance of the twisted hexagonal tube.

  • 240.
    Chen, Jingjing
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University.
    Wu, Jiajun
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Wang, Changsong
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Mechanism of waste-heat recovery from slurry by scraped-surface heat exchanger2017Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 207, s. 146-155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Waste-heat recovery from discharged slurries can improve the net raw biogas production in the bio-methane process in order to meet the demand for a next-generation of anaerobic digestion. In this study, a numerical model of a scraped-surface heat exchanger was proposed with the consideration of the complete and precise rheological behaviour of the slurry of animal manure for the first time for achieving highly efficient waste-heat recovery. The rheological model results were verified with new experimental data measured in this work. Subsequently, the convective heat-transfer coefficient of the scraped-surface heat exchanger was calculated numerically with the proposed numerical model, and the performance was determined. Then, the contributions of waste-heat recovery from the slurry to the biogas production using a general shell-and-tube heat exchanger and the scraped-surface heat exchanger were calculated quantitatively and compared. For the case of scraped-surface heat exchanger, the increase of net raw biogas production can be up to 8.53%, which indicates that there is a great potential to increase the net raw biogas production in the bio-methane process using a scraped-surface heat exchanger with low-cost equipment and a compactible structure.

  • 241.
    Chen, Yifeng
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Novel Solvent for CO2 Capture2019Ingår i: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 158, s. 5124-5129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To develop novel solvent for CO2 capture, CO2 absorption performance using the aqueous of polyethylene glycol 200 (PEG200) and choline-2-pyrrolidinecarboxylic acid ([Cho][Pro]) was studied and evaluated systematically in this work, in which the critical properties of PEG200 were estimated with group contribution method, and other thermo-physical properties were determined experimentally or taken from literatures directly and then correlated with empirical equations. The CO2 solubility in PEG200 was measured and represented with the Henry’s law and Poynting correction, while the measured CO2 solubility in PEG200/H2O was correlated with RK-NRTL model. [Cho][Pro] was used as the chemical ingredient to enhance the absorption capacity and rate of CO2 in [Cho][Pro]/PEG200/H2O, and the corresponding properties and CO2 solubility were studied. The kinetic parameters, such as enhancement factor (E), reaction rate constant (k), and activation energy (Ea) of CO2 in [Cho][Pro]/PEG200/H2O were estimated from the new experimental data measured in this work and compared with the commercialized aqueous MEA solution. The process simulation and pilot-testing based on [Cho][Pro]/PEG200/H2O will be performed in the future.

  • 242.
    Chen, Yifeng
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ma, Chunyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Thermodynamic study on aqueous polyethylene glycol 200 solution and performance assessment for CO2 separation2020Ingår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 504, artikel-id 112336Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To develop polyethylene glycol 200 (PEG200) and aqueous PEG200 solutions (PEG200/H2O) as solvents for CO2 separation, in this study, the available thermo-physical properties of PEG200 and PEG200/H2O measured experimentally were surveyed, evaluated, and correlated with empirical equations. The solubility of CO2 in PEG200 was also surveyed, evaluated and described with the Henry's law with the Poynting correction, while the solubilities of CH4 and N2 in PEG200 were determined experimentally and then described with the Henry's law. The CO2, CH4 and N2 solubilities in PEG200/H2O were measured and described with the Redlich–Kwong Nonrandom-Two-Liquid (RK-NRTL) model. In addition, the performances of PEG200, PEG200/H2O and other commercialized physical solvents for CO2 separation were discussed based on the properties, and the biogas upgrading was chosen as the example to quantitatively evaluate the performances of PEG200 and PEG200/H2O with process simulation and compared with the high pressure water scrubbing (HPWS). It shows that the total energy usage and the amount of recirculated solvent for biogas upgrading can decrease by 9.1% and 26.5%, respectively, when H2O is replaced by PEG200 completely.

  • 243.
    Chen, Yifeng
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Sun, Yunhao
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    CO2 separation using a hybrid choline-2-pyrrolidine-carboxylic acid/polyethylene glycol/water absorbent2020Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 257, artikel-id 113962Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Developing novel hybrid absorbents is essential for CO2 separation. In this study, the density and viscosity of a hybrid absorbent (choline-2-pyrrolidine-carboxylic acid/polyethylene glycol/water ([Cho][Pro]/PEG200/H2O)) were measured experimentally, and its CO2 solubility was also determined. The excess mole volume and excess Gibbs energy of activation of the hybrid absorbent were further estimated to understand the molecular structure and interactions between [Cho][Pro]/PEG200 and H2O. The CO2 solubilities in [Cho][Pro]/PEG200 and [Cho][Pro]/H2O were analyzed and described using the Redlich–Kwong non-random-two-liquid (RK-NRTL) model. Furthermore, the CO2 solubility in the hybrid absorbent was predicted using the RK-NRTL model and was compared with the new experimental results for verification. The effect of H2O on the CO2 absorption performance was further analyzed. The performance and cost of the hybrid absorbent were compared with those of other commercialized CO2 absorbents. In addition, the recyclability of the hybrid absorbent for CO2 separation was studied. The results of this study indicated that the hybrid absorbent could be promising for CO2 separation.

  • 244.
    Chen, Yifeng
    et al.
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Zhang, Yingying
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Yuan, Shengjuan
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Liu, Chang
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Yang, Zhuhong
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Thermodynamic Study for Gas Absorption in Choline-2-pyrrolidine-carboxylic Acid + Polyethylene Glycol2016Ingår i: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 61, nr 10, s. 3428-3437Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The solubility of pure CO2, CH4, and N2 in the mixture of choline-2-pyrrolidine carboxylic acid ([Cho][Pro]) and polyethylene glycol (PEG200) (mass ratio = 1:2) was measured experimentally at temperatures from 308.15 to 338.15 K and pressures up to 28 bar, in which [Cho][Pro] is an ionic liquid and PEG200 is a cosolvent with the purpose to decrease the viscosity. It was found that [Cho][Pro]/PEG200 showed a good selectivity for CO2/CH4 and CO2/N2 separation. The measured experimental data points from this work and others were further used to estimate the thermodynamic properties including the Henry's law constants for the gases in [Cho][Pro]/PEG200, the equilibrium constant for the reaction between CO2 and [Cho][Pro], the CO2 absorption enthalpy in [Cho][Pro]/PEG200, and so forth. The consistent results of the CO2 absorption enthalpy at infinite dilution prove the reliability of the thermodynamic properties obtained in this work. The thermodynamic properties of [Cho][Pro]/PEG200 were further compared with other three typical absorbents, and the absorption enthalpy is nearly half of that for 30 wt % MEA aqueous solution. At the same time, the theoretical amount of absorbents needed for [Cho][Pro]/PEG200 is much lower than that of H2O scrubbing. This shows that [Cho][Pro]/PEG200 is a promising absorbent

  • 245. Chen, Yu
    et al.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Martins, Marcia
    Application of transfer function based harmonic study method to an offshore wind farm2012Konferensbidrag (Refereegranskat)
  • 246.
    Cukalevski, Ninel
    et al.
    Mihailo Pupin Institute.
    Milanovic, Jovica V.
    University of Manchester, School of Electrical and Electronic Engineering, The University of Manchester.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    The Power Quality Monitoring for Transmission System in Liberalized Environment2014Konferensbidrag (Refereegranskat)
  • 247.
    Cundeva, Snezana
    et al.
    University of Ss Cyril and Methodius, Faculty of Electrical Engineering and IT, Skopje.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Schwanz, Daphne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hosting capacity of the grid for wind generators set by voltage magnitude and distortion levels2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    The hosting capacity, frequently defined as amount of distributed generation that can be connected to a certain location without resulting in an unacceptable quality or reliability for other customers, is limited. To know how much distributed generation can be connected in the grid it is important to define appropriate performance indicators. In this paper, the hosting capacity of the grid for wind power generation has been studied. Voltage magnitude and distortion levels are the performance indicators used to find the hosting capacity. A discussion is started on the interaction between windpower installations and the grid.

  • 248. Cundeva, Snezana
    et al.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Yang, Kai
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Distortion levels in the grid due to windpower integration2013Konferensbidrag (Övrigt vetenskapligt)
  • 249.
    Cundeva, Snezana
    et al.
    University Ss. Cyril and Methodius Faculty of Electrical Engineering and IT Skopje.
    Krkoleva Mateska, Aleksandra
    University Ss. Cyril and Methodius Faculty of Electrical Engineering and IT Skopje.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hosting capacity of LV residential grid for uncoordinated ev charging2018Ingår i: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The envisaged large penetration of electric vehicles (EVs) in the near future, brings new challenges to low voltage (LV) and medium voltage (MV) grids. For uncoordinated EV charging, the impact on the LV grid may be significant, due to the simultaneity between the residential power peak and the charging of EVs. The amount of EV chargers that can be connected to the grid without endangering the reliability or voltage quality for other customers is called the hosting capacity. This paper presents the analyses of the hosting capacity of a realistic LV residential network with 160 households for EV chargers. A stochastic approach is used, assuming that the EV chargers are randomly distributed over the households and the phases. For different EVs penetration rates in the network, the hosting capacity for slow chargers is determined. The results show that the EV penetration rate that the network can safely accept is 45%.

  • 250.
    Dahl, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rationell elanvändning genom värmeackumulering1987Rapport (Övrigt vetenskapligt)
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