| 1. |
- Alevanau, Aliaksandr, 1965-, et al.
(författare)
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Applicability of Scaling Approach for Analysis of Pyrolysis and Gasification of Porous Structures Composed of Solid Fuel Particles
- 2012
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Ingår i: ISRN Mechanical Engineering. - : Hindawi Publishing Corporation. - 2090-5122 .- 2090-5130.
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Tidskriftsartikel (refereegranskat)abstract
- Experimental research on the pyrolysis and gasification of randomly packed straw pellets was conducted with an emphasis on the reactive properties of the shrinking porous structure of the pellets. The apparent kinetics of such pyrolysis was approximated by the random pore, grain, and volumetric models. The best approximation results were obtained with the grain and random pore models. The self-organized oscillations of the pellet conversion rate during pyrolysis were observed. Two complementary explanations of the phenomenon are proposed.
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| 2. |
- Alevanau, Aliaksandr, et al.
(författare)
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Parameters of high temperature steam gasification of original and pulverised wood pellets
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:10, s. 2068-2074
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Tidskriftsartikel (refereegranskat)abstract
- Experiments on gasification of chars obtained from original and pulverised wood pellets were conducted in atmosphere of water steam and nitrogen under temperatures of 800, 900 and 950 degrees C. Molar flow rates of carbon containing product gases were measured and approximated using different models with respect to extents of carbon conversion in char of the pellets. Comparison of the random pore, grain and volumetric models revealed the best applicability for approximations of the random pore model. Apparent activation energies obtained as a result of application of the models to the data from experiments with char of original pellets were higher in comparison to those of pulverised pellets, except for a grain model. Approximations under 800 degrees C showed relatively big deviations from experimental data on the beginning of char gasification. This is attributed to catalytic effects from alkali metals in the pellets.
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| 3. |
- Alevanau, Aliaksandr, et al.
(författare)
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Prospective side effects of the heat and mass transfers in micro-porous structure of char during intermediate and final stages of the high-temperature pyrolysis
- 2013
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Ingår i: Nonlinear Phenomena in Complex Systems. - 1561-4085 .- 1817-2458. ; 16:3, s. 287-301
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Tidskriftsartikel (refereegranskat)abstract
- The general problem of a decrease of activation energy for reactions of thermal decomposition in ligno-cellulosic materials in the end of the high-temperature pyrolysis has been discussed. Experiments emphasizing the differences between the starting, intermediate and final stages of the process were conducted. A hypothesis to solve the problem from the point of view of a fundamental fractal theory was formulated. The conclusions of the discussions related to the hypothesis gave a description of new experiments to prove the fundamental theory on diffusion processes with naturally or artificially created conditions for self-organization.
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| 4. |
- Alevanau, Aliaksandr, 1965-
(författare)
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Study of the Apparent Kinetics of Biomass Gasification Using High-Temperature Steam
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Among the latest achievements in gasification technology, one may list the development of a method to preheat gasification agents using switched ceramic honey combs. The best output from this technology is achieved with use of water steam as a gasification agent, which is heated up to 1600 °C. The application of these temperatures with steam as a gasification agent provides a cleaner syngas (no nitrogen from air, cracked tars) and the ash melts into easily utilised glass-like sludge. High hydrogen content in output gas is also favourable for end-user applications.Among the other advantages of this technology is the presumable application of fixed-bed-type reactors fed by separately produced and preheated steam. This construction assumes relatively high steam flow rates to deliver the heat needed for endothermic reactions involving biomass. The biomass is to be heated uniformly and evenly in the volume of the whole reactor, providing easier and simpler control and operation in comparison to other types of reactors. To provide potential constructors and exploiters of these reactors with the kinetic data needed for the calculations of vital parameters for both reactor construction and exploitation, basic experimental research of high-temperature steam gasification of four types of industrially produced biomass has been conducted.Kinetic data have been obtained for straw and wood pellets, wood-chip charcoal and compressed charcoal of mixed origin. Experiments were conducted using two experimental facilities at the Energy and Furnace Division of the Department of Material Science and Engineering (MSE) at the School of Industrial Engineering and Management (ITM) of the Royal Institute of Technology (KTH) and at the Combustion Laboratory of the Mechanical Engineering Department of the University of Maryland (UMD), USA.The experimental facility at the Energy and Furnace Division has been improved with the addition of several constructive elements, providing better possibilities for thermo-gravimetric measurements.The obtained thermo-gravimetric data were analysed and approximated using several models described in the literature. In addition, appropriate software based on the Scilab package was developed. The implementation of the isothermal method based on optimisation algorithms has been developed and tested on the data obtained under the conditions of a slow decrease of temperature in experiments with the char gasification in small-scale experimental facilities in the Energy and Furnace Division.The composition of the gases generated during the gasification of straw and wood pellets by high-temperature steam has been recorded and analysed for different experimental conditions.
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| 5. |
- Alevanau, Aliaksandr, et al.
(författare)
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Study of the effects of gaseous micro-expansion on the efficiency of convective heat transfer during pyrolysis
- 2013
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 106, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of temperature in the proximity of wood pellets (8 mm diameter) and thin wooden stick slices (5 cm diameter and 5 mm thickness) were conducted to estimate the effects of mixing between the evolving volatiles and hot steam (T > 700°C) flowing around the particles. Measurements of mass loss of the slices were conducted to estimate the apparent kinetic parameters of their pyrolysis. A simple kinetic model of the process (type II by Pyle and Zaror (1984) [20]) was investigated. The experiments showed a plateau-like part in the graphs of temperature measured in the proximity to the samples. The existence of this plateau-like part agrees with the general data of calorimetric measurements of pyrolysis, which show extensive energy consumption in the beginning of an active production of volatiles. A hypothesis regarding feedback on the process due to the micro-expansion and mixing of volatiles in the convective boundary layer is discussed.
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| 6. |
- Biswas, Amit, et al.
(författare)
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Change of pyrolysis characteristics and structure of woody biomass due to steam explosion pretreatment
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:10, s. 1849-1854
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) pretreatment has been implemented for the production of wood pellet. This paper investigated changes in biomass structure due to implication of steam explosion process by its pyrolysis behavior/ characteristics. Salix wood chip was treated by SE at different pretreatment conditions, and then pyrolysis characteristic was examined by thermogravimetric analyzer (TGA) at heating rate of 10 K/min. Both pyrolysis characteristics and structure of biomass were altered due to SE pretreatment. Hemicellulose decomposition region shifted to low temperature range due to the depolymerization caused by SE pretreatment. The peak intensities of cellulose decreased at mild pretreatment condition while they increased at severe conditions. Lignin reactivity also increased due to SE pretreatment. However, severe pretreatment condition resulted in reduction of lignin reactivity due to condensation and re-polymerization reaction. In summary, higher pretreatment temperature provided more active biomass compared with milder pretreatment conditions. © 2011 Elsevier B.V. All rights reserved.
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| 7. |
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| 8. |
- Biswas, Amit Kumar, et al.
(författare)
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Steam pretreatment of Salix to upgrade biomass fuel for wood pellet production
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:9, s. 1711-1717
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) pretreatment is served to separate the main components of woody biomass. In general there is a noticeable gap in literature in terms of application of steam explosion process to upgrade biomass fuel for wood pellet production. In order to study the influence of steam explosion pretreatment on biomass fuel, Salix wood chips was used as raw material. Four different SE experiments were performed by varying two key process factors; time and temperature. Elementary quality and ash properties of the pretreated residue were investigated. Moreover, physical and thermochemical properties of the pellet, produced from the residue, were also investigated. Reduction in ash content especially in alkali metals was observed in steam treated residue. Pretreatment of biomass also enhanced carbon content and reduced oxygen amount in the fuel which enhanced the heating value of the fuel. Moreover, pretreatment enhanced pellet density, impact resistance, and abrasive resistance of pellet. However, small degradation in ash fusion characteristics and char reactivity was also observed as the severity of the process increased.
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| 9. |
- Biswas, Amit Kumar, 1984-
(författare)
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Thermochemical behavior of pretreated biomass
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mankind has to provide a sustainable alternative to its energy related problems. Bioenergy is considered as one of the potential renewable energy resources and as a result bioenergy market is also expected to grow dramatically in future. However, logistic issues are of serious concern while considering biomass as an alternative to fossil fuel. It can be improved by introducing pretreated wood pellet. The main objective of this thesis is to address thermochemical behaviour of steam exploded pretreated biomass. Additionally, process aspects of torrefaction were also considered in this thesis. Steam explosion (SE) was performed in a laboratory scale reactor using Salix wood chips. Afterwards, fuel and thermochemical aspects of SE residue were investigated. It was found that Steam explosion pretreatment improved both fuel and pellet quality. Pyrolysis of SE residue reveals that alerted biomass composition significantly affects its pyrolysis behaviour. Contribution from depolymerized components (hemicellulose, cellulose and lignin) of biomass was observed explicitly during pyrolysis. When devolatilization experiment was performed on pellet produced from SE residue, effect of those altered components was observed. In summary, pretreated biomass fuel characteristics is significantly different in comparison with untreated biomass. On the other hand, Process efficiency of torrefaction was found to be governed by the choice of appropriate operating conditions and the type of biomass.
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| 10. |
- Boström, Mathias, et al.
(författare)
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Lithium atom storage in nanoporous cellulose via surface-induced Li-2 breakage
- 2013
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 104:6, s. 63003-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a physical mechanism that enhances a splitting of diatomic Li-2 at cellulose surfaces. The origin of this splitting is a possible surface-induced diatomic-excited-state resonance repulsion. The atomic Li is then free to form either physical or chemical bonds with the cellulose surface and even diffuse into the cellulose layer structure. This allows for an enhanced storage capacity of atomic Li in nanoporous cellulose.
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