| 1. |
- Rönnbäck, Marie, et al.
(author)
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Combustion Processes in a Biomass Fuel Bed-Experimental Results
- 2008
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In: Progress in Thermochemical Biomass Conversion. - Oxford, UK : Wiley Blackwell. - 9780470694954 - 0632055332 - 9780632055333 ; , s. 743-757
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Book chapter (other academic/artistic)abstract
- Combustion processes in a biomass bed are investigated experimentally. Special attention is paid to the influence of primary airflow and particle properties on the ignition front, its temperature and on the composition of the gas leaving the front. Two test rigs have been built: a large rig in the same size as a boiler for domestic use and a small laboratory test rig. In both rigs the ignition front moves in opposite direction to the primary airflow. Three combustion regimes are identified: a sub-stoichiometric regime with incomplete consumption of oxygen, a sub-stoichiometric regime with complete consumption of oxygen and an over-stoichiometric regime. The results show that a fuel with higher density and thermal conductivity (but in other respects similar to other fuels) has a wider sub-stoichiometric regime where oxygen is cornpletely consumed. If the particle size is increased (for the same fuel quality) the airflow range of this regime becomes shorter and starts at higher airflow.
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| 2. |
- Yu, C, et al.
(author)
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A modelling study on cellulose particle pyrolysis under fluidized-bed conditions.
- 2008
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In: Progress in thermochemical biomass conversion. - Oxford : Blackwell science. - 9780470694954 - 0632055332 - 9780632055333 ; , s. 1091-1106
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Conference paper (peer-reviewed)abstract
- To study biomass pyrolysis processes, a numerical model is developed in this work focusing on the cellulose constituent. A single cellulose particle is supposed to experience pyrolysis at a fairly high heating rate in the case of typical fluidized bed conditions. The model involves the pyrolytic kinetic scheme and the detailed heat and mass transfers caused by radiation, conduction, diffusion and convection with respect to the solid, liquid and gas products from pyrolysis. From the solution of the model, the central role of the reaction heat versus a slow heat supply through the particle is identified. The dynamic characteristic of the pyrolysis and the evolutions of the internal pressure and the flow of the products are analyzed quantitatively. Computation of the model shows the importance of particle permeability, whereas the liquid phase of active cellulose and inter-particle secondary reaction of volatile play a negligible role during the pyrolysis under a typical fluidized bed conditions both for small and large particles. Various predictions by the model provide a good understanding of the complex process of biomass pyrolysis, which can be useful for applications of thermochemical conversions of biomass.
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| 3. |
- Yu, C, et al.
(author)
-
Modeling potassium release in biomass pyrolysis
- 2008
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In: Progress in thermochemical biomass conversion. - Oxford : Blackwell science. - 0632055332 - 9780470694954 - 9780632055333 ; , s. 1107-1115
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Conference paper (peer-reviewed)abstract
- Alkali compound emission during biomass thermochemical conversion gives rise to a number of problems such as agglomeration, slag, fouling and metal corrosion in the conversion process system. Understanding the behaviour of alkali emission from biomass fuels is important to solve these problems. In this work, a study focused on the potassium compound release in biomass pyrolysis is carried out. The transformation of the element, K, is interpreted based on literature and the present study. A mathematic model of the potassium compounds emitting from biomass during pyrolysis is proposed. The different existing forms of potassium in biomass, the chemical equilibrium of the compounds at the pyrolytic environment and the potassium compound release due to vaporization at high temperature are taken into account in the model. The result of the mathematic model provides an understanding of the alkali compound release in biomass pyrolysis and the effects of the pyrolytic temperature, the fuel composition and residence time on the release process.
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| 4. |
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| 5. |
- Davidsson, K. O., et al.
(author)
-
The Pyrolysis Kinetics of a Single Wood Particle
- 2008
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In: Progress in Thermochemical Biomass Conversion. - Oxford, UK : Wiley-Blackwell. - 9780470694954 ; , s. 1129-1142
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Book chapter (other academic/artistic)abstract
- Experimental results from birchwood and pinewood pyrolysis in a new single particle reactor are presented. Apparent lunetic parameters for the mass-loss of wood particles (5-800 mg) at temperatures from 300 to 860°C are determined. Kinetic parameters for the evolution of CO, CO2, H2O, H2 and CH4, are also established. The drylng process was examined and it was found that drying and pyrolysis increasingly overlap in time as temperature rises and that the overlap is substantial above 450 °C.
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| 6. |
- Romey, I., et al.
(author)
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Concept for a Decentralised Combined Heat and Power Generation Unit for Biomass Gasification
- 2001
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In: Progress in Thermochemical Biomass Conversion. - Oxford, UK : Wiley-Blackwell. - 9780470694954 ; , s. 499-508
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Book chapter (other academic/artistic)abstract
- The development of an improved process for decentralised combined heat and power generation from biomass gasification was the main goal of this project. Based on gasification tests performed in a bench-scale pressurised fluidised gasifier a concept for an allothermal gasification unit was made. Air-blown as well as steam-blown tests were carried out considering three different kinds of biomass (birch, salix, and crushed pelletised straw) against a wide spectrum of operation conditions with different bed-materials (silica sands, magnesite and dolomite). The aim of the gas quality optimisation was the production of a fuel gas (syngas) with a high H2 and low tar content suitable for a gas engine. The tar content was measured with SPA method and a gravimetric method. The tests were performed at the Royal Institute of Technology, Stockholm, in close co-operation with the University of Essen. Jenbacher AG designed a new type of cylinder head for the direct feeding of the hot pressurised syngas into the gas engine in co-operation with the Technical University of Graz. Taking the results obtained into account a concept of decentralised combined heat and power generation (CHP) unit with an electrical power output of 1 MW was set up.
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| 7. |
- Rönnbäck, Marie, et al.
(author)
-
Combustion process in a biomass fuel bed --experimental results
- 2001
-
In: Progress in Thermochemical Biomass Conversion. - 0632055332 ; 1, s. 743-757
-
Conference paper (peer-reviewed)abstract
- Combustion processes in a biomass bed are investigated experimentally. Special attention is paid to the influence of primary air flow and particle properties on the ignition front, its temperature and on the composition of the gas leaving the front. Two test rigs have been built: a large rig in the same size as a domestic boiler and a small laboratory test rig. In both rigs the combustion front moves in opposite direction to the primary air flow. Two combustion regimes are identified: a sub-stoichiometric regime with complete consumption of oxygen and an over-stoichiometric regime. The results show that a fuel with higher density and thermal conductivity (but in other respects similar) has a wider sub-stoichiometric regime. If the particle size is increased the air flow range becomes shorter and starts at higher air flow.
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