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Refractory corrosion in biomass gasification
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.ORCID-id: 0000-0003-1170-2203
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)Alternativ tittel
Korrosion av eldfasta material i biomassaförgasning (svensk)
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.

sted, utgiver, år, opplag, sider
Umeå: Umeå Universitet , 2018. , s. 62
Emneord [en]
Refractory corrosion, slag, biomass, gasification
HSV kategori
Forskningsprogram
materialvetenskap
Identifikatorer
URN: urn:nbn:se:umu:diva-152664ISBN: 978-91-7601-944-3 (tryckt)OAI: oai:DiVA.org:umu-152664DiVA, id: diva2:1256564
Disputas
2018-11-09, Hörsal N360, Naturvetarhuet, Johan Bures väg 16, Umeå, 13:00 (svensk)
Opponent
Veileder
Tilgjengelig fra: 2018-10-19 Laget: 2018-10-17 Sist oppdatert: 2023-03-07bibliografisk kontrollert
Delarbeid
1. Interaction between ash forming elements in woody biomass and two high alumina refractories part 1: effects on morphology and elemental distribution
Åpne denne publikasjonen i ny fane eller vindu >>Interaction between ash forming elements in woody biomass and two high alumina refractories part 1: effects on morphology and elemental distribution
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

To gain more knowledge about possibly destructive effects of ash-forming elements in woody biomass on refractory materials in entrained flow gasification, an exposure study was performed on two high alumina refractories. The materials, a pre-fired castable consisting of about 63 weight-% Al2O3, and a phosphate bonded brick with 83 weight-% Al2O3 was exposed to synthetic ash mixtures at 1050°C and 1 atm CO2 for 7 days. This paper presents distribution of ash-forming elements and morphology of the samples microstructure, while identification and distribution of crystalline compounds is presented in a separate paper. In the samples, potassium (K) had infiltrated the materials and reacted with different components, while calcium (Ca) did not seem to have any direct effect during these conditions. The matrix of the castable absorbed much K, became clogged and produced a distinct border between reacted and unaffected matrix. The coarser matrix of the phosphate bonded brick retained much of its porosity and had ash transported further into the material without a clear distinction between reacted and unaffected matrix. Grains with >30 atomic-% Si, formed a layer enriched in K, with a thickness up to 40 µm and cracks propagating through it. Grains mainly consisting of Al2O3 seemed unaffected by the exposure. When the ash was rich in SiO2, a melt was produced that restricted the attack on the refractories to the surface and coarser pores.

Emneord
Refractory corrosion, slag, biomass, gasification
HSV kategori
Forskningsprogram
materialvetenskap
Identifikatorer
urn:nbn:se:umu:diva-152660 (URN)
Forskningsfinansiär
Bio4Energy
Tilgjengelig fra: 2018-10-17 Laget: 2018-10-17 Sist oppdatert: 2023-03-07
2. Interaction between ash forming elements in woody biomass and two high alumina refractories part 2: transformation of crystalline compounds
Åpne denne publikasjonen i ny fane eller vindu >>Interaction between ash forming elements in woody biomass and two high alumina refractories part 2: transformation of crystalline compounds
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

Two high alumina refractories, one brick and one pre fired castable was exposed to pure K2CO3, K2CO3 + CaCO3, and K2CO3 + CaCO3 + SiO2 at 1050°C and a CO2 atmosphere. A stratified investigation of crystalline phases was made with polycrystalline x-ray diffraction, and thermodynamic equilibrium calculations were performed to explore possible formation paths. A monoclinic polymorph of KAlSiO4 was formed to a large extent in both materials exposed to pure K2CO3. Throughout the affected part of the castable and a small layer close to the surface of the brick, a solid solution between KAlO2 and KAlSiO4 formed, K1-xAl1-xSixO2, x = 0.19. The affected area of the castable had 30-50 %wt new phases and made a sharp transition to unaffected material. The concentration of new phases in the brick was decreasing at an even rate from about 40 to 15%wt throughout the whole material thickness of 14 mm. Exposure to K2CO3 and CaCO3 showed the same phases and behavior, but no Ca-bearing phases could be detected. The mixture containing K2CO3, CaCO3 and SiO2 did not penetrate far into the material but formed the same phases in the affected areas. Wollastonite (CaSiO3) formed in the slag on top of these materials. The major mechanism for formation of new phases is suggested to be the formation of an initial melt composed of K2O and SiO2. This liquid is then dissolving refractory components and forms a liquid in equilibrium with KAlSiO4 and K1-xAl1-xSixO2.

Emneord
Refractory corrosion, slag, biomass, gasification, phase transformation
HSV kategori
Forskningsprogram
materialvetenskap
Identifikatorer
urn:nbn:se:umu:diva-152661 (URN)
Forskningsfinansiär
Bio4Energy
Tilgjengelig fra: 2018-10-17 Laget: 2018-10-17 Sist oppdatert: 2023-03-07
3. Characterization of spent spinel-based refractory lining from a 3 MW black liquor gasifier
Åpne denne publikasjonen i ny fane eller vindu >>Characterization of spent spinel-based refractory lining from a 3 MW black liquor gasifier
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Abstract [en]

Black liquor gasification is dependent on minimizing heat loss to the surroundings and thus needs to be well insulated. In combination with the high temperature and basic black liquor, a very corrosive environment is created on the hot face of such a reactor. Therefore the wall system is required to be chemically and thermally stable at the same time as it has insulating properties. These cannot easily be combined in the same material and therefore layers with different properties can be used in combination. Penetration of species through the lining can lead to further reactions with other construction materials, less suited for chemical resistance, corrosion of the pressure shell is an example with catastrophic consequences. This paper investigates two castable and one fused cast spinel (MgAl2O4) refractory after about 1 600 hours, and one fused cast material used for 15 000 hours of operation in a 3 MWth black liquor gasifier. Infiltration of Na, followed by destruction of microstructure, and extensive formation of NaAlO2 was observed throughout the whole castable materials, while it was mainly restricted to the hot face of the fused cast materials. Formation of NaAlO2 leads to a volumetric expansion which eventually lead to an increased pressure on the steel shell. In addition, the expansion of the bricks can cause stress and by that spallation and material loss.

Emneord
Refractory corrosion, black liquor, gasification, spinel
HSV kategori
Forskningsprogram
materialvetenskap
Identifikatorer
urn:nbn:se:umu:diva-152662 (URN)
Tilgjengelig fra: 2018-10-17 Laget: 2018-10-17 Sist oppdatert: 2023-03-07
4. Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture
Åpne denne publikasjonen i ny fane eller vindu >>Ash Formation in Pilot-Scale Pressurized Entrained-Flow Gasification of Bark and a Bark/Peat Mixture
Vise andre…
2016 (engelsk)Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, nr 12, s. 10543-10554Artikkel i tidsskrift (Fagfellevurdert) 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 kWth, 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.

sted, utgiver, år, opplag, sider
American Chemical Society (ACS), 2016
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-130239 (URN)10.1021/acs.energyfuels.6b02222 (DOI)000390072900057 ()2-s2.0-85006511826 (Scopus ID)
Prosjekter
Bio4Energy
Forskningsfinansiär
Bio4Energy
Tilgjengelig fra: 2017-01-16 Laget: 2017-01-14 Sist oppdatert: 2023-03-23bibliografisk kontrollert
5. Exposure of refractory materials during high-temperature gasification of a woody biomass and peat mixture
Åpne denne publikasjonen i ny fane eller vindu >>Exposure of refractory materials during high-temperature gasification of a woody biomass and peat mixture
Vise andre…
2018 (engelsk)Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, nr 2, s. 777-787Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Finding resilient refractory materials for slagging gasification systems have the potential to reduce costs and improve the overall plant availability by extending the service life. In this study, different refractory materials were evaluated under slagging gasification conditions. Refractory probes were continuously exposed for up to 27 h in an atmospheric, oxygen blown, entrained flow gasifier fired with a mixture of bark and peat powder. Slag infiltration depth and microstructure were studied using SEM EDS. Crystalline phases were identified with powder XRD. Increased levels of Al, originating from refractory materials, were seen in all slags. The fused cast materials were least affected, even though dissolution and slag penetration could still be observed. Thermodynamic equilibrium calculations were done for mixtures of refractory and slag, from which phase assemblages were predicted and viscosities for the liquid parts were estimated.

sted, utgiver, år, opplag, sider
Elsevier, 2018
Emneord
Gasification, Oxygen blown, Biomass, Entrained flow, Slag, Refractory
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-143620 (URN)10.1016/j.jeurceramsoc.2017.09.016 (DOI)000418211000047 ()2-s2.0-85029532285 (Scopus ID)
Prosjekter
Bio4Energy
Forskningsfinansiär
Bio4Energy
Tilgjengelig fra: 2018-01-30 Laget: 2018-01-30 Sist oppdatert: 2023-03-07bibliografisk kontrollert

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