| 1. |
- Kuba, Matthias, et al.
(författare)
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Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant
- 2015
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 139, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues. (C) 2015 Elsevier B.V. All rights reserved.
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| 2. |
- Kuba, Matthias, et al.
(författare)
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Mechanism of Layer Formation on Olivine Bed Particles in Industrial-Scale Dual Fluid Bed Gasification of Wood
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:9, s. 7410-7418
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Tidskriftsartikel (refereegranskat)abstract
- Utilization of biomass as feedstock in dual fluidized bed steam gasification is a promising technology for the substitution of fossil energy carriers. Experience from industrial-scale power plants showed an alteration of the olivine bed material due to interaction with biomass ash components. This change results mainly in the formation of Ca-rich layers on the bed particles. In this paper, a mechanism for layer formation is proposed and compared to the better understood mechanism for layer formation on quartz bed particles. Olivine bed material was sampled at an industrial-scale power plant before the start of operation and at predefined times after the operation had commenced. Therefore, time-dependent layer formation under industrial-scale conditions could be investigated. The proposed mechanism suggests that the interaction between wood biomass ash and olivine bed particles is based on a solid-solid substitution reaction, where Ca2+ is incorporated into the crystal structure. As a consequence, Fe2+/3+ and Mg2+ ions are expelled as oxides. This substitution results in the formation of cracks in the particle layer due to a volume expansion in the crystal structure once Ca2+ is incorporated. The results of this work are compared to relevant published results, including those related to quartz bed particles
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| 3. |
- Kuba, Matthias, et al.
(författare)
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Thermal stability of bed particle layers on naturally occurring minerals from dual fluid bed gasification of woody biomass
- 2016
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Ingår i: Energy & Fuels. - Washington : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 30:10, s. 8277-8285
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Tidskriftsartikel (refereegranskat)abstract
- The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However, as olivine contains heavy metals such as nickel and chromium, no further usage of the nutrient-rich ash is possible, and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz, and K-feldspar in terms of agglomeration and fracturing at typical temperatures. To this end, samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar, which become mixed into the fluidized bed during operation. Using experimental and thermochemical analysis, it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fracturing of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However, quartz may be less active during the buildup of the layers due to lower amounts of Ca in the initial layer formation.
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| 4. |
- Skoglund, Nils, et al.
(författare)
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Effects of Bed Material Type and Fuel Ash Composition on Layer Formation and Bed Agglomeration in Thermo-chemical Conversion of Biomass and Waste Streams in Fluidized Beds
- 2018
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Ingår i: 23rd International Conference on Fluidized Bed Conversion, 13-17 May 2018, Seoul, Korea.
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Konferensbidrag (refereegranskat)abstract
- The role of fluidized beds is increasingly important for challenging and ash-rich fuels, such as fast-growing biomass and waste streams. From a biomass perspective, the relatively homogeneous woody-type fuels are most commonly used in fluidized beds today whereas the fuel feedstock for waste streams is more heterogeneous. A key issue in enabling a broader fuel feedstock for existing and planned fluidized beds is how the fuel ash interacts with bed materials of different types during combustion or gasification. The resulting bed particle coating, layers, and cracks formed in bed grains are responsible for bed agglomeration and bed material deposition mechanisms, but studies have suggested that there is a possibility to affect melting temperatures of bed ash and reduce interaction between fuel ash and bed material through additives or by fuel blend design. Furthermore, it is of interest to extend the life-time of bed materials in the reactor to reduce the amount of material that is generated as waste streams, as well as increase the timespan between bed replacements.The aim of this review is therefore to summarize some of our previous research in this topic, to discuss current knowledge concerning layer formation and bed agglomeration mechanisms, address the benefit for different bed materials, and discuss how fuel ash composition can be used to reduce bed agglomeration issues. This is achieved by comparing studies from different combustion and gasification facilities using different biomasses as well as agricultural residues and waste streams. In particular, the possibility of using fuel blend design to reduce interaction of fuel ash with bed material will be highlighted. Using such approaches, coupled with a fundamental understanding of how differences between bed materials affect layer formation mechanisms, has the potential to reduce operational issues caused by interactions between fuel ash and bed materials as well as increase the potential fuel feedstock.
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