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  • Börjesson, Pål, et al. (författare)
  • Future Production and Utilisation of Biomass in Sweden: Potentials and CO2 Mitigation
  • 1997
  • Ingår i: BIOMASS & BIOENERGY. - : Elsevier. - 1873-2909 .- 0961-9534. ; 13:6, s. 399-412
  • Tidskriftsartikel (refereegranskat)abstract
    • Swedish biomass production potential could be increased significantly if new production methods, such as optimised fertilisation, were to be used. Optimised fertilisation on 25% of Swedish forest land and the use of stem wood could almost double the biomass potential from forestry compared with no fertilisation, as both logging residues and large quantities of excess stem wood not needed for industrial purposes could be used for energy purposes. Together with energy crops and straw from agriculture, the total Swedish biomass potential would be about 230 TWh/yr or half the current Swedish energy supply if the demand for stem wood for building and industrial purposes were the same as today. The new production methods are assumed not to cause any significant negative impact on the local environment. The cost of utilising stem wood produced with optimised fertilisation for energy purposes has not been analysed and needs further investigation. Besides replacing fossil fuels and, thus, reducing current Swedish CO2 emissions by about 65%, this amount of biomass is enough to produce electricity equivalent to 20% of current power production. Biomass-based electricity is produced preferably through co-generation using district heating systems in densely populated regions, and pulp industries in forest regions. Alcohols for transportation and stand-alone power production are preferably produced in less densely populated regions with excess biomass. A high intensity in biomass production would reduce biomass transportation demands. There are uncertainties regarding the future demand for stem wood for building and industrial purposes, the amount of arable land available for energy crop production and future yields. These factors will influence Swedish biomass potential and earlier estimates of the potential vary from 15 to 125 TWh/yr.
  • Boman, Christoffer, 1970-, et al. (författare)
  • Effects of increased small-scale biomass pellet combustion on ambient air quality in residential areas : A parametric dispersion modeling study
  • 2003
  • Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 24:6, s. 465-474
  • Tidskriftsartikel (refereegranskat)abstract
    • Sweden's goals of contemporaneously reducing CO2 emissions and phasing out nuclear power will require a maximum utilization of biomass fuels. This would imply a significant shift from electricity and fuel oil to biomass generated heat, but must also be accomplished without a deterioration of the local air quality. The most suitable energy carrier seems to be pelletized biomass fuels with their associated low emissions and considerable residential conversion potential. Using an underlying statistical design, a parametric dispersion modeling study was performed to estimate and illustrate the combined effects of source-specific, meteorological and modeling variables on the ambient air quality in a typical residential area for different conversion scenarios. The work nicely illustrated the benefits of combining statistical designs with model calculations. It further showed that the concentration of combustion related ambient THC was strongly related to conditions affecting the source strength, but only weakly to the dispersion conditions and model variables. Time of year (summer or winter); specific emission performance; extent of conversion from electricity; conversion from wood log combustion; and specific efficiency of the pellet appliances showed significant effects in descending order. The effects of local settings and model variables were relatively small, making the results more generally applicable. To accomplish the desired conversion to renewable energy in an ecologically and sustainable way, the emissions would have to be reduced to a maximum advisable limit of (given as CH4). Further, the results showed the potential positive influence by conversion from wood log to low emission pellet combustion.
  • Brage, C., et al. (författare)
  • Tar evolution profiles obtained from gasification of biomass and coal
  • 2000
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 18:1, s. 87-91
  • Tidskriftsartikel (refereegranskat)abstract
    • The tar content of the product gases from gasification of biomass is one of the major factors affecting the subsequent process stages. In this work, evolution profiles of the main tar constituents, i.e. benzene, toluene, indene, naphthalene and phenol were obtained during about 1 h gasification runs of biomass and coal in a pressurised fluidised-bed at 700 and 900 degrees C, 0.4 MPa. Sampling and analysis was achieved, using the solid-phase adsorption (SPA) method, previously developed in our laboratory. Our main objectives were: (1) to illustrate the usefulness of the SPA method; (2) to shed new light on the main factors governing tar evolution. It was found that temperature and the type of feedstock used mainly affected tar yields. For both biomass and coal the concentration of tar products decreased with increasing run time at a rate that was fastest initially. This behaviour, which was much more pronounced for coal, provides evidence that char catalytically affects tar evolution. Accordingly, char accumulates in the bed to a various extent depending on fuel and gradually approaching steady state. Biomass char, contrary to coal char, is readily oxidised during gasification, and thus only small steady-state amounts are available to catalyse tar cracking reactions.
  • Gabra, M., et al. (författare)
  • Alkali retention/separation during bagasse gasification : A comparison between a fluidised bed and a cyclone gasifier
  • 2001
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:6, s. 461-476
  • Tidskriftsartikel (refereegranskat)abstract
    • Biomass fuelled integrated gasification/gas turbines (BIG/GTs) have been found to be one of the most promising technologies to maximise electricity output in the sugar industry. However, biomass fuels contain alkali metals (Na and K) which may be released during the gasification processes and cause deleterious effects on the downstream hardware (e.g. the blades of gas turbines). Much research has therefore been focused on different kinds of gas cleaning. Most of these projects are using a fluidised bed gasifier and includes extensive gas cleaning which leads to a high capital investment. Increasing alkali retention/separation during the gasification may lead to improved producer gas quality and reduced costs for gas cleaning. However, very little quantitative information is available about the actual potential of this effect. In the present work, comparative bench-scale tests of bagasse gasification were therefore run in an isothermal fluidised bed gasifier and in a cyclone gasifier to evaluate which gasification process is most attractive as regards alkali retention/separation, and to try to elucidate the mechanisms responsible for the retention. The alkali retention in the fluidised bed gasifier was found to be in the range of 12-4% whereas in the cyclone gasifier the alkali separation was found to be about 70%. No significant coating of the fluidised bed's bed material particles could be observed. The SEM/EDS and the elemental maps of the bed material show that a non-sticky ash matrix consisting of mainly Si, Al and K were distributed in a solid form separated from the particles of bed material. This indicates the formation of a high temperature melting potassium containing silicate phase, which is continuously scavenged and lost from the bed through elutriation. © 2001 Elsevier Science Ltd. All rights reserved.
  • Gabra, Mohamed, et al. (författare)
  • Development of a sugar cane residue feeding system for a cyclone gasifier
  • 1998
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 15:2, s. 143-153
  • Tidskriftsartikel (refereegranskat)abstract
    • For the smooth and continuous operation of a cyclone gasifier, the fuel must be fed continuously and without interruption or large fluctuations. A feeding system for bagasse/cane trash powder was therefore designed, built and tested. It consisted of a feeding bin with four feeder screws in the bottom which deliver the fuel to two downcomers from which the fuel is injected by steam into the gasifier. During the first tests, the low bulk density and cohesive characteristics of a crushed bagasse/cane trash powder were found to cause an accumulation of the fuel in the feeding system, creating difficulties for the flow into the gasifier. In addition, once the flow of the crushed bagasse/cane trash powder is interrupted by a build-up in the downcomer channels, the crushed bagasse/cane trash powder becomes progressively compacted into a dense structure, resulting in blockage of the discharge. It was found possible to eliminate this problem by changing the shape of the slivers of the crushed bagasse/cane trash powder to render them more homogeneous. This was achieved by pelletizing the crushed bagasse or cane trash before grinding it to powder.
  • Gabra, M., et al. (författare)
  • Evaluation of cyclone gasifier performance for gasification of sugar cane residue : Part 1: Gasification of bagasse
  • 2001
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:5, s. 351-369
  • Tidskriftsartikel (refereegranskat)abstract
    • A method for avoiding excessive amount of alkali compounds and carryover particles in producer gas from gasification of sugar cane residue has been studied and evaluated. The cane sugar residue is gasified in a two-stage combustor at atmospheric pressure, where the first stage is a cyclone gasifier. The cyclone works as particle separator as well. This paper covers the results obtained for gasification of bagasse. Bagasse powder was injected into the cyclone with air and steam as transport medium. The gasification tests were made with two feeding rates, 39 and 52 kg/h. Seven experiments were conducted with the equivalence ratio being varied. The heating values of the producer gas are sufficient for stable gas turbine combustion. About 60-70% of the alkali input with fuel was separated from the producer gas in the cyclone. However the total alkali contents of the producer gas was found to be higher than in ABB Stal PFBC gas turbines and at least an order of magnitude higher than what is required by most gas turbine manufacturers for operation of a gas turbine. The carryover particles concentrations in the producer gas were found to be in the range of that for PFBC gas turbines, but higher than what is required by most gas turbine manufacturers for operation of a gas turbine. Samples studied with scanning electronic microscope give indication that most of the carryover particles are below 10 μm in size. Fly ash-melting tests have not shown any major ash melting up to 1200°C, but it was found that some of the particles entrained with producer gas were partially melted. Integrated experiments with a gas turbine need to be done for accurate evaluation of the possibilities to use the producer gas from the gasification of bagasse to run a gas turbine without problems of hard deposits and corrosion on the turbine blades. In part 2 of this two-part paper the results from cane trash gasification tests are reported. © 2001 Published by Elsevier Science Ltd.
  • Gabra, M., et al. (författare)
  • Evaluation of cyclone gasifier performance for gasification of sugar cane residue : Part 2: Gasification of cane trash
  • 2001
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:5, s. 371-380
  • Tidskriftsartikel (refereegranskat)abstract
    • In Part 1 of this two-part paper, results from gasification of bagasse in a cyclone gasifier have been reported. In this paper results from gasification of cane trash in the same cyclone gasifier are presented. The cane trash powder is injected into the cyclone with air as transport medium. The gasification tests were made with two feeding rates, 39 and 46 kg/h at two equivalence ratios of 0.25 and 0.20 and the gasification temperature ranging from 820°C to 850°C. It was found that the heating value of the producer gas is in the range of 4.5-4.8 MJ/Nm3(dry gas), which is sufficient for stable gas turbine combustion. Significant alkali separation has been achieved in the cyclone stage. However, the alkali levels and carryover particle concentrations in the producer gas were found to be higher than allowable in a gas turbine. Despite high ash melting temperatures found by the TGA-DTA, deposition problems cannot be excluded since some carryover panicles in the producer gas seem to have been melted and since some gasification of K and Na compounds is indicated. As an overall assessment, cane trash appears as a more problematic fuel than bagasse for this application. Integrated experiments with a gas turbine need to be done for accurate evaluation of the possibilities to use the producer gas from the gasification of cane trash to run a gas turbine without problems of hard deposits and corrosion on the turbine blades. © 2001 Published by Elsevier Science Ltd.
  • Hassan, Salman, et al. (författare)
  • Pneumatic conveying of wood powder by using a steam-jet ejector
  • 2000
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 19:2, s. 103-117
  • Tidskriftsartikel (refereegranskat)abstract
    • Wood powder and sawdust are two fuels which will be tested in a pressurized cyclone-gasifier. The gasifier will be a part of combined cycle power plant where a gas turbine is run by the product gases from the gasifier and a steam boiler will use the exhaust gas from the turbine. To inject the fuel into the cyclone, a steam-jet ejector seems to be appropriate due to its simplicity and the possibility of using the steam produced by the boiler for feeding of the fuel. Three types of wood powder with different particle-size distribution have been tested in different ejector geometries. The results show that the steam-jet ejector is suitable as a feeding pump for wood powder and sawdust. For commercial wood powder fuel with particle size below 1 mm, a powder to steam mass flow ratio of about 25 and with coarser sawdust a mass flow ratio of at least 10 can be reached. The pressure gain required to overcome the pressure drop in the cyclone gasifier can be achieved. The relative pressure gain seems to be independent of the size distribution of the particles.
  • Joppich, A., et al. (författare)
  • Wood powder feeding, difficulties and solutions
  • 1999
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 16:3, s. 191-198
  • Tidskriftsartikel (refereegranskat)abstract
    • pneumatic fuel feeding system for wood powder fired gas turbines was incorporated at the Vienna University of Technology. One of the most important requirements of fuel feeding is a very homogeneous mass flow of wood powder. Therefore, the performance of the mechanical conveying part of the feeding system has been studied experimentally at flow rates corresponding to the operation range. Beside screw feeding, a vibrator is used to homogenize the flow rate. While the screw feeder shows large fluctuations, the vibrator conveyer reduces them considerably. The tests also show that for each flow rate a certain optimum amplitude of the vibrator exists at which the fluctuations reach a minimum. Furthermore, a linear function is observed between optimum oscillation amplitude and feeding rate.
  • Koullas, D.P., et al. (författare)
  • Effect of alkali delignification on wheat straw saccharification by fusarium oxysporum cellulases
  • 1993
  • Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 4:1, s. 9-13
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of alkaline delignification of wheat straw on the chemical composition and the subsequent enzymic hydrolysis of the pretreated straw are reported. Both hot (120°°C) and cold (20–36°°C) delignification were investigated, using either aqueous or organic alkaline solutions. The treated lignocellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Both delignification and saccharification yield showed linear relationships with the level of alkali used. Under the chosen experimental conditions 70–100% hydrolysis was achieved either by hot or cold delignification. Delignification to at least 50% appeared crucial for total polysaccharide conversion.
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