Properties of oxygen carriers based on natural and waste materials at high degrees of reduction
Licentiatavhandling, 2022
The reactivity of the oxygen carriers toward relevant gaseous fuels is an important parameter. It was found that the syngas conversion decreased at higher reduction degrees of oxygen carriers. The by-products, which contain a lower iron content, saw a quicker decrease of syngas conversion compared to that of the ore-based materials. The same trend was seen on the methane conversion. The decrease seen toward different fuels was due to the exhaustion of the available oxygen in the oxygen carrier particles.
The fluidization performance of the bed particles is critical in a fluidized bed setup, a common arrangement for chemical-looping processes. Defluidization was observed on oxygen carriers based on iron ore materials at higher reduction degrees set by syngas, while the iron-based by-products and manganese ores did not defluidize at all. This was caused by the formation of wüstite and/or elemental iron under a highly reducing environment, which later migrated to the particles’ surface and triggered bed agglomeration. Manganese ores seem to be less prone to defluidization compared to the iron ores under highly reducing environment.
The conversion of pine forest residue char, a biomass-based fuel, was investigated at high reduction degrees using ilmenite and iron sand. The hydrogen partial pressure in the bed during the char conversion increased as the oxygen carrier reduction degree increased. The increasing hydrogen partial pressure caused a hydrogen inhibition effect, which subsequently slowed down the char conversion rate. The increasing hydrogen partial pressure was possibly caused by the equilibrium shifting in the water-gas shift reaction and/or the decreasing reactivity of the oxygen carriers themselves. The mass conversion degree thereby affected the char conversion indirectly. There was no significant difference between the reactivity of the char with ilmenite and that with iron sand at higher reduction degrees.
Given these findings, high reduction degrees of oxygen carriers during a chemical-looping operation should preferably be avoided to minimize the risk of performance issues. Despite this, the performance of several oxygen carriers would probably not be affected significantly by a highly reducing environment alone.
high reduction
defluidization
chemical-looping gasification
oxygen carrier
reactivity
Författare
Victor Purnomo
Chalmers, Kemi och kemiteknik, Energi och material
Study of defluidization of iron- and manganese-based oxygen carriers under highly reducing conditions in a lab-scale fluidized-bed batch reactor
Fuel Processing Technology,;Vol. 219(2021)
Artikel i vetenskaplig tidskrift
Effect of the Mass Conversion Degree of an Oxygen Carrier on Char Conversion and Its Implication for Chemical Looping Gasification
Energy & Fuels,;Vol. 36(2022)p. 9768-9779
Artikel i vetenskaplig tidskrift
Performance of iron sand as an oxygen carrier at high reduction degrees and its potential use for chemical looping gasification
Fuel,;Vol. 339(2023)
Artikel i vetenskaplig tidskrift
Kemcyklisk förgasning för produktion av bioflygbränsle med negativa emissioner
Energimyndigheten (51430-1), 2021-01-01 -- 2023-12-31.
Chemical Looping gAsification foR sustainAble production of biofuels (CLARA))
Europeiska kommissionen (EU) (EC/H2020/817841), 2018-11-01 -- 2022-10-31.
Drivkrafter
Hållbar utveckling
Styrkeområden
Energi
Ämneskategorier
Kemiska processer
Infrastruktur
Chalmers materialanalyslaboratorium
Licentiatuppsatser vid Institutionen för kemi och kemiteknik, Chalmers tekniska högskola: 08
Utgivare
Chalmers
KB-salen, Kemigården 4, Chalmers
Opponent: Associate Professor Hao Wu, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Denmark