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Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
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2016 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 12, p. 10543-10554Article in journal (Refereed) Published
Abstract [en]

Pressurized entrained-flow gasification (PEFG) of bark and a bark/peat mixture (BPM) was carried out in a pilot scale reactor (600 kW(th), 7 bar(a)) with the objective of studying ash transformations and behaviors. The bark fuel produced a sintered but nonflowing reactor slag, while the BPM fuel produced a flowing reactor slag. Si was enriched within these slags compared to their original fuel ash compositions, especially in the bark campaign, which indicated extensive ash matter fractionation. Thermodynamically, the Si contents largely accounted for the differences in the predicted solidus/liquidus temperatures and melt formations of the reactor slags. Suspension flow viscosity estimations were in qualitative agreement with observations and highlighted potential difficulties in controlling slag flow. Quench solids from the bark campaign were mainly composed of heterogeneous particles resembling reactor fly ash particles, while those from the BPM campaign were flowing slags with likely chemical interactions with the wall refractory. Quench effluents and raw syngas particles were dominated by elevated levels of K that, along with other chemical aspects, indicated KOH(g) and/or K(g) were likely formed during PEFG. Overall, the results provide information toward development of woody biomass PEFG and indicate that detailed understanding of the ash matter fractionation behavior is essential.

Place, publisher, year, edition, pages
2016. Vol. 30, no 12, p. 10543-10554
National Category
Bioenergy
Identifiers
URN: urn:nbn:se:umu:diva-130239DOI: 10.1021/acs.energyfuels.6b02222ISI: 000390072900057OAI: oai:DiVA.org:umu-130239DiVA, id: diva2:1065813
Available from: 2017-01-16 Created: 2017-01-14 Last updated: 2018-10-17Bibliographically approved
In thesis
1. Refractory corrosion in biomass gasification
Open this publication in new window or tab >>Refractory corrosion in biomass gasification
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Korrosion av eldfasta material i biomassaförgasning
Abstract [en]

To stop the net emission of CO2 to the atmosphere, we need to reduce our dependency of fossil fuels. Although a switch to a bio-based feedstock hardly can replace the total amount of fossils used today, utilization of biomass does still have a role in a future in combination with other techniques. Valuable chemicals today derived from fossils can also be produced from biomass with similar or new technology. One such technique is the entrained flow gasification where biomass is converted into synthesis gas. This gas can then be used as a building stone to produce a wide range of chemicals.

Slagging and corrosion problems are challenges presented by the ash forming elements in biomass during thermochemical energy conversion. The high temperature in the entrained flow process together with ash forming elements is creating a harsh environment for construction materials in the reactor. Severe corrosion and high wear rates of the lining material is a hurdle that has to be overcome to make the process more efficient.

The objective of this work is to investigate the nature of the destructive interaction between ash forming elements and refractory materials to provide new knowledge necessary for optimal refractory choice in entrained flow gasification of woody biomass. This has been done by studying materials exposed to slags in both controlled laboratory environments and pilot scale trials. Morphology, elemental composition and distribution of refractories and slag were investigated with scanning electron microscopy and energy dispersive X-ray spectroscopy. Crystalline phases were investigated with X-ray diffraction, and thermodynamic equilibrium calculations were done in efforts to explain and make predictions of the interaction between slag and refractory.

Observations of slag infiltration and formation of new phases in porous materials indicate severe deterioration. The presence of Si in the materials is limiting intrusion by increasing the viscosity of infiltrated slag. This is however only a temporary delay of severe wear considering the large amount of slag that is expected to pass the refractory surface. Zircon (or zirconium) (element or mineral?) based material show promising properties when modeled with thermodynamic equilibrium, but disassembling of sintered material and dissociation of individual grains was seen after exposure to a Si- and Ca-rich slag. Fused cast materials have a minimal slag contact where the only interaction is on the immediate hot face. Dissolution was however observed when exposed to a silicate-based slag, as was the formation of NaAlO2 after contact with black liquor.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2018. p. 62
Keywords
Refractory corrosion, slag, biomass, gasification
National Category
Energy Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:umu:diva-152664 (URN)978-91-7601-944-3 (ISBN)
Public defence
2018-11-09, Hörsal N360, Naturvetarhuet, Johan Bures väg 16, Umeå, 13:00 (Swedish)
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Available from: 2018-10-19 Created: 2018-10-17 Last updated: 2018-10-18Bibliographically approved

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Carlborg, MarkusBackman, Rainer

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