Improved Fuel Conversion in Chemical Looping Combustion using Novel Volatiles Distributors and Effective Manganese-based Oxygen Carriers
Doktorsavhandling, 2024

Chemical looping combustion (CLC) is a promising carbon capture technology, as CO2 generated during combustion is inherently obtained in a concentrated form. As the technology moves from pilot-scale to larger-scale operations, factors such as fuel conversion and the development of robust and economically feasible oxygen carriers become increasingly critical. In this thesis, two ways to improve the fuel conversion in the fuel reactor are studied: i) use of a volatile distributor to achieve improved gas-solids contact and ii) use of effective and cheap oxygen carrier materials.

Poor contact between volatiles from solid fuels such as biomass, and oxygen carriers is one reason for insufficient gas conversion in the fuel reactor of CLC systems based on interconnected fluidized beds. Hence, the concept of a volatiles distributor (VD) is proposed for achieving a uniform cross-sectional distribution of volatiles, providing better gas-solids contact and improving the gas conversion in the fuel reactor. In this work, it is clearly demonstrated that the use of the VD results in a more uniform cross-sectional distribution of volatiles under different fluidization regimes. Adjusted designs of the VD were found to improve the uniformity of the horizontal distribution of the simulated volatiles. CFD simulations additionally reveal the improved gas-solids mixing, highlighting the potential of the VD for addressing incomplete conversion of high-volatile fuels in fluidized bed systems. The effectiveness and design flexibility of the VD, together with the most suitable drag model identified in the CFD simulations, are instructive for the large-scale application of the VD.

In chemical looping with oxygen uncoupling (CLOU), the conversion of volatiles and char in the fuel reactor can be notably enhanced compared to regular CLC. This justifies studies of CLOU oxygen carriers with sufficient reactivity, mechanical stability, and reasonable production costs. This thesis covers the investigations of four natural manganese ores and one manufactured calcium manganite as oxygen carriers in a 300 W circulating fluidized-bed system together with detailed characterizations of the fresh and spent oxygen carrier samples. CLC operations with non-calcined manganese ores proceed as smoothly as with calcined ones, indicating that an energy-intensive pre-calcination step for manganese-based oxygen carriers in large-scale applications is not necessary. The content of Fe in manganese ores plays a crucial role in their O2 release. A sufficiently high content of Ca in manganese ores facilitates the formation of perovskite phase, which enhances both the O2 release and reactivity. The manufactured calcium manganite demonstrates higher oxygen release capacity and CH4/syngas conversion compared to the four natural ores, offering another effective way of increasing fuel conversion in the fuel reactor.

In conclusion, the fuel conversion in CLC could be improved using the novel volatiles distributor, as demonstrated in both cold-flow model fluidized bed and CFD simulations, and effective manganese-based oxygen carriers characterized by sufficient mechanical stability and economic feasibility.

Calcium manganite

Chemical looping combustion

CO2 capture

Volatiles distributor

Chemical looping with oxygen uncoupling

Manganese ores

Gas-solids contact

Lecture hall HA3, Hörsalsvägen 4, Göteborg (Online defence Password: DrLi)
Opponent: Professor Stuart Scott, University of Cambridge, UK


Xiaoyun Li

Chalmers, Rymd-, geo- och miljövetenskap, Energiteknik

An experimental study of a volatiles distributor for solid fuels chemical-looping combustion process

Fuel Processing Technology,; Vol. 220(2021)

Artikel i vetenskaplig tidskrift

CFD modeling of a fluidized bed with volatiles distributor for biomass chemical looping combustion combustion

Chemical Engineering Science,; Vol. 295(2024)

Artikel i vetenskaplig tidskrift

Xiaobao Wang, Xiaoyun Li, Lan Yi, Anders Lyngfelt, Tobias Mattisson, Xiaoqin Wu, Qingang Xiong, Hao Luo. Numerical Evaluation and Optimization of Volatiles Distributors with Different Configurations for Biomass Chemical Looping Combustion

Xiaoyun Li, Robin Faust, Anders Lyngfelt, Pavleta Knutsson, Tobias Mattisson. Non-calcined manganese ores as oxygen carriers for chemical looping combustion with oxygen uncoupling in a circulating fluidized bed reactor system

Xiaoyun Li, Robin Faust, Victor Purnomo, Daofeng Mei, Carl Linderholm, Anders Lyngfelt, Tobias Mattisson. Performance of a perovskite-structured calcium manganite oxygen carrier produced from natural ores in a batch reactor and in operation of a chemical-looping combustion reactor system

Carbon removal cost can be significantly reduced with chemical-looping combustion.
Climate change has intensified in recent years, with rising global carbon dioxide (CO2) levels and significant annual emissions. To achieve the climate targets for limiting global warming to 1.5 °C, rapid and massive reductions in greenhouse gas emissions are essential but not enough. Thus, carbon removal technologies, such as bioenergy carbon capture and storage (BECCS), will be crucial for removing excessive CO2 accumulated in the atmosphere. Chemical-looping combustion of renewable biomass (bio-CLC) with carbon transportation and storage is a promising BECCS technology for atmospheric CO2 removal, since the CO2 from combustion can be obtained in pure form without the need of costly and energy-consuming gas separation.

While bio-CLC is a well-proven technology in small pilot-scale units, its widespread industrial application is closely related to the expectations of much lower cost of CO2 capture with CLC. In this work, the goal is to further improve the economic performance by addressing costs associated with incomplete fuel conversion and oxygen carriers. Two approaches to improve the fuel conversion in the CLC system were addressed: gas-solids contact, specifically focusing on combustibles from solid fuels like biomass, i.e. volatiles, and the reactivity of the solids, i.e. the oxygen carrier.

The current work provides the first detailed experimental and modelling proof-of-concept of a device, here named volatiles distributor, which is shown to give a more uniform cross-sectional distribution of volatiles and therefore enhance gas-solids contact. Together with detailed material characterizations, the operational performance of four natural manganese ores and one calcium manganite capable of releasing oxygen provide a comprehensive understanding of the main active phases and primary elements distributions in these materials and demonstrate their potential for improving fuel conversion. By improving fuel conversion with the volatiles distributor and manganese-based oxygen carriers, this research underscores the potential for large-scale CLC application at a lower cost.

Högeffektiv syrebärare av billiga råvaror för användning i kemcyklisk förbränning av biomassa

ÅForsk (21-277), 2021-06-21 -- 2022-11-30.

Fördelning av flykt vid inmatning av fasta bränslen i fluidiserad bädd

Energimyndigheten (46626-1), 2019-09-01 -- 2024-05-31.



Kemiska processer



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5504



Lecture hall HA3, Hörsalsvägen 4, Göteborg (Online defence Password: DrLi)


Opponent: Professor Stuart Scott, University of Cambridge, UK

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