| 1. |
- Berndes, Göran, 1966, et al.
(author)
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The contribution of biomass in the future global energy supply: A review of 17 studies
- 2003
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In: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 25:1, s. 1-28
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Journal article (peer-reviewed)abstract
- This paper discusses the contribution of biomass in the future global energy supply. The discussion is based on a review of 17 earlier studies on the subject. These studies have arrived at widely different conclusions about the possible contribution of biomass in the future global energy supply (e.g., from below 100 EJ yr-1 to above 400 EJ yr-1 in 2050). The major reason for the differences is that the two most crucial parameters - land availability and yield levels in energy crop production - are very uncertain, and subject to widely different opinions (e.g., the assessed 2050 plantation supply ranges from below 50 EJ yr-1 to almost 240 EJ yr-1). However, also the expectations about future availability of forest wood and of residues from agriculture and forestry vary substantially among the studies. The question how an expanding bioenergy sector would interact with other land uses, such as food production, biodiversity, soil and nature conservation, and carbon sequestration has been insufficiently analyzed in the studies. It is therefore difficult to establish to what extent bioenergy is an attractive option for climate change mitigation in the energy sector. A refined modeling of interactions between different uses and bioenergy, food and materials production - i.e., of competition for resources, and of synergies between different uses - would facilitate an improved understanding of the prospects for large-scale bioenergy and of future land-use and biomass management in general. © 2003 Elsevier Science Ltd. All rights reserved.
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| 2. |
- Berndes, Göran, 1966, et al.
(author)
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The feasibility of large-scale lignocellulose-based bioenergy production
- 2001
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In: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 20:5, s. 371-383
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Journal article (peer-reviewed)abstract
- Global, large-scale use of bioenergy may replace a significant part of present fossil fuel use. We show that labor availability and water resources are large compared to those required to operate a bioenergy system of such size. The present study contradicts the assertion by Giampietro et al. [Bioscience 47(9) (1997) 587], that labor and water availability provide invincible barriers to a large-scale use of biofuels. We examine water and labor requirements under more reasonable assumptions about bioenergy supply options and demand levels. Bioenergy supplies are based on dedicated plantations of lignocellulosic crops and bioenergy demand is based on the renewable intensive global energy scenarios (RIGES). We find that labor and water requirements are an order of magnitude lower than the estimates by Giampietro et al. For instance, labor requirements do not exceed 1 percent of the estimated total work force in any country. © 2001 Elsevier Science Ltd.
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| 3. |
- Hansson, P.A., et al.
(author)
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Air emissions from the fuel supply system of a Swedish CHP plant and the effects of stricter emission regulations
- 2003
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In: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 24:1, s. 59-68
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Journal article (peer-reviewed)abstract
- The purpose of this work was to quantify the energy use and production of air emissions by supply systems for different biofuels used in a typical Swedish combined heat and power plant. In addition, the effects of the future reductions in the total amounts of exhaust gas emissions, as a result of stricter emission regulations for transport and off-road equipment, were studied. A model was developed and used for the calculations. Input data were collected from a plant situated some 100 km from Stockholm in Sweden. Biofuels used by the plant include chips from limbs and tops, by-products from sawmills and chips from willow energy plantations. The results show that residues from sawmills are very favourable in terms of the studied environmental parameters. Air emissions from limbs and tops is 5-8 times greater than that from sawmills. The use of a terminal for temporary storage means that additional transport and loading operations are necessary which result in a 30% increase in air emissions. The most important effects of the stricter emission regulations are that emissions of nitrous oxides (NOx) caused by the supply system will decrease by up to 70% within 10 years and that the unburned hydrocarbon (HC) emissions will decrease by 30-35%. © 2002 Elsevier Science Ltd. All rights reserved.
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| 4. |
- Boman, Christoffer, 1970-, et al.
(author)
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Effects of increased small-scale biomass pellet combustion on ambient air quality in residential areas : A parametric dispersion modeling study
- 2003
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In: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 24:6, s. 465-474
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Journal article (peer-reviewed)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.
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| 5. |
- Brage, C., et al.
(author)
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Tar evolution profiles obtained from gasification of biomass and coal
- 2000
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 18:1, s. 87-91
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Journal article (peer-reviewed)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.
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| 6. |
- Gabra, M., et al.
(author)
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Alkali retention/separation during bagasse gasification : A comparison between a fluidised bed and a cyclone gasifier
- 2001
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:6, s. 461-476
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Journal article (peer-reviewed)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.
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| 7. |
- Gabra, M., et al.
(author)
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Evaluation of cyclone gasifier performance for gasification of sugar cane residue : Part 1: Gasification of bagasse
- 2001
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:5, s. 351-369
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Journal article (peer-reviewed)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.
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| 8. |
- Gabra, M., et al.
(author)
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Evaluation of cyclone gasifier performance for gasification of sugar cane residue : Part 2: Gasification of cane trash
- 2001
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:5, s. 371-380
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Journal article (peer-reviewed)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.
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| 9. |
- Hassan, Salman, et al.
(author)
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Pneumatic conveying of wood powder by using a steam-jet ejector
- 2000
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 19:2, s. 103-117
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Journal article (peer-reviewed)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.
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| 10. |
- Lundgren, Joakim, et al.
(author)
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Experimental studies during heat load fluctuations in a 500 kW wood-chips fired boiler
- 2004
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In: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 26:3, s. 255-267
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Journal article (peer-reviewed)abstract
- Several long-term experiments with fluctuating thermal outputs have been carried out in a newly developed biomass fuelled boiler suitable for small district heating networks. The experiments have been performed by either using the furnace only or the furnace together with a water heat store. Comparisons between these two operation strategies have been made concerning emissions and overall performance. Furthermore, the plant has been run to match a simulated heat demand during different seasons, in order to study the performance of the system during more realistic operation conditions. The results are very satisfactory concerning both performance and emissions, using any of the control strategies. Typical emissions of CO and NOx during the experiments are in the range of 10–50 mgNm−3 (5–25 mgMJ−1) and 130–175 mgNm−3 (60–90 mgMJ−1), respectively. However, during summer when the heat demand is low or zero, operational problems will occur if the heat store is excluded. Therefore, the main conclusion is that the most appropriate solution for a small district-heating system is to use a water heat store to match the heat load variations, while the furnace operates at as constant thermal output as possible.
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