Impact of Ash on the Properties of Fluidized Bed Materials
Doctoral thesis, 2022
The utilization of the fluidized bed technology offers the possibility of thermally converting a large variety of biogenic feedstocks. The characteristics of the bed material which is used in the process play a major role regarding the overall process performance. These characteristics are influenced by interactions between the bed material and the fuel ash. The materials investigated within this work were quartz, ilmenite, olivine, and two different feldspars. This work investigates several different properties of the bed material which can be influenced by interactions with the fuel ash. Depending on the combinations of fuel and bed material, as well as the choice of thermal conversion process, these interactions can be beneficial or detrimental.
It was found that quartz and ilmenite have a strong tendency to react with alkali and can thereby mitigate to a certain degree alkali-induced corrosion of metallic components in the reactor. In the case of quartz, this bed material-alkali interaction leads to the formation of alkali-silicates which exhibit a low melting temperature and can therefore cause agglomeration of the bed material.
Olivine and feldspar are more resistant towards agglomeration. Interactions with biomass ash led to the formation of an ash layer which has catalytic properties towards tar removal, which is necessary to avoid problems associated with tar condensation during gasification. After longer residence times, the particles acquire an oxygen carrying ability due to the formation of a surface layer containing Fe and Mn. This decreases the calorific value of the product gas and requires bed material replacement. If fuel containing high amounts of phosphorus is converted, this waste stream can further be utilized for nutrient recovery.
Ilmenite is used in a process which exploits its oxygen carrying ability. Dilution of ilmenite by fuel ash diminishes this property but the necessary replacement of material can be decreased by magnetically separating active ilmenite from inactive ash.
It was found that quartz and ilmenite have a strong tendency to react with alkali and can thereby mitigate to a certain degree alkali-induced corrosion of metallic components in the reactor. In the case of quartz, this bed material-alkali interaction leads to the formation of alkali-silicates which exhibit a low melting temperature and can therefore cause agglomeration of the bed material.
Olivine and feldspar are more resistant towards agglomeration. Interactions with biomass ash led to the formation of an ash layer which has catalytic properties towards tar removal, which is necessary to avoid problems associated with tar condensation during gasification. After longer residence times, the particles acquire an oxygen carrying ability due to the formation of a surface layer containing Fe and Mn. This decreases the calorific value of the product gas and requires bed material replacement. If fuel containing high amounts of phosphorus is converted, this waste stream can further be utilized for nutrient recovery.
Ilmenite is used in a process which exploits its oxygen carrying ability. Dilution of ilmenite by fuel ash diminishes this property but the necessary replacement of material can be decreased by magnetically separating active ilmenite from inactive ash.
ash interaction
layer formation
agglomeration
fluidized bed
catalytic tar removal
oxygen carrying
bed material
EF-salen, Hörsalsvägen 11, Göteborg
Opponent: Professor Maria Zevenhoven, Åbo Akademi University, Finland
Author
Robin Faust
Chalmers, Chemistry and Chemical Engineering, Energy and Material
Role of K and Ca for catalytic activation of bed material during biomass gasification
23rd International Conference on Fluidized Bed Conversion,;(2018)
Paper in proceeding
Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 1. K-Feldspar
Energy & Fuels,;Vol. 33(2019)p. 7321-7332
Journal article
Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 2. Na-Feldspar
Energy & Fuels,;Vol. 33(2019)p. 7333-7346
Journal article
Microscopic investigation of layer growth during olivine bed material aging during indirect gasification of biomass
Fuel,;Vol. 266(2020)
Journal article
Comparison of Ash Layer Formation Mechanisms on Si-Containing Bed Material during Dual Fluidized Bed Gasification of Woody Biomass
Energy & Fuels,;Vol. 34(2020)p. 8340-8352
Journal article
Development of Oxygen Transport Properties by Olivine and Feldspar in Industrial-Scale Dual Fluidized Bed Gasification of Woody Biomass
Energy & Fuels,;Vol. 35(2021)p. 9424-9436
Journal article
Laboratory study of interactions between biomass ash and alkali-feldspar bed material
CFB 2021 - Proceedings of the 13th International Conference on Fluidized Bed Technology,;(2021)p. 491-496
Paper in proceeding
Interactions between Automotive Shredder Residue and Olivine Bed Material during Indirect Fluidized Bed Gasification
Energy & Fuels,;Vol. 35(2021)p. 15935-15949
Journal article
Magnetic Properties of Ilmenite used for Oxygen Carrier Aided Combustion
Other conference contribution
Robin Faust, Ali Valizadeh, Ren Qiu, Alyona Tormachen, Jelena Maric, Teresa Berdugo Vilches, Nils Skoglund, Martin Seemann, Mats Halvarsson, Marcus Öhman, Pavleta Knutsson; Ash Layer Formation in Dual Fluidized Bed Gasification of Wood – Impact of Surface Morphology
Robin Faust, Katharina Fürsatz, Panida Aonsamang, Marcus Sandberg, Matthias Kuba, Nils Skoglund, Pavleta Knutsson; Early Layer Formation on K-Feldspar during Fluidized Bed Combustion with Phosphorus-rich Fuel
Anthropogenic greenhouse gas emissions are a major driver for global warming. Especially the CO2 emissions by burning of fossil fuels for heat and power generation have contributed to an increase in global greenhouse gas concentrations since the industrial revolution. Replacement of fossil fuels with renewable sources is one way of decreasing further CO2 emissions into the atmosphere. Furthermore, the utilization of biomass and waste as fuel for heat and power generation offers the possibility to reduce the dependence on fossil fuel imports.
A suitable technique to achieve efficient conversion of these complex and inhomogeneous feedstocks, is through the application of a fluidized bed. In a fluidized bed reactor, the fuel is immersed in a sand bed and a gas stream is led from below through the bed material. Thereby, the sand acquires fluid-like characteristics which improve the distribution of heat throughout the reactor, which is beneficial for the thermal conversion of inhomogeneous fuels.
An important factor for the efficiency of fluidized bed reactors are the interactions between the sand bed material and the fuel ash. Depending on the process conditions as well as the compositions of fuel and bed material, these interactions can improve the process and facilitate the generation of a gas which can be used to produce, for example, biofuel. In other cases, the interactions can be detrimental and require replacement and disposal of the ash-enriched bed material. Handling and recycling of parts of this waste stream is important to reduce the waste fraction and increase the overall circularity of the process.
This work provides insight into the different challenges and opportunities that exist for the application of renewable fuels for thermal conversion in fluidized bed reactors.
A suitable technique to achieve efficient conversion of these complex and inhomogeneous feedstocks, is through the application of a fluidized bed. In a fluidized bed reactor, the fuel is immersed in a sand bed and a gas stream is led from below through the bed material. Thereby, the sand acquires fluid-like characteristics which improve the distribution of heat throughout the reactor, which is beneficial for the thermal conversion of inhomogeneous fuels.
An important factor for the efficiency of fluidized bed reactors are the interactions between the sand bed material and the fuel ash. Depending on the process conditions as well as the compositions of fuel and bed material, these interactions can improve the process and facilitate the generation of a gas which can be used to produce, for example, biofuel. In other cases, the interactions can be detrimental and require replacement and disposal of the ash-enriched bed material. Handling and recycling of parts of this waste stream is important to reduce the waste fraction and increase the overall circularity of the process.
This work provides insight into the different challenges and opportunities that exist for the application of renewable fuels for thermal conversion in fluidized bed reactors.
Subject Categories
Inorganic Chemistry
Chemical Process Engineering
Materials Chemistry
Bioenergy
Infrastructure
Chalmers Materials Analysis Laboratory
ISBN
978-91-7905-693-3
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5159
Publisher
Chalmers
EF-salen, Hörsalsvägen 11, Göteborg
Opponent: Professor Maria Zevenhoven, Åbo Akademi University, Finland