Potassium Ash Interactions with Oxygen Carriers Steel Converter Slag and Iron Mill Scale in Chemical-Looping Combustion of Biomass - Experimental Evaluation Using Model Compounds
Journal article, 2020

Chemical-looping combustion (CLC) is a combustion technology in which a solid oxygen carrier is used to convert fuel. The oxygen carrier is oxidized in air and subsequently transferred to a separate reactor in which it reacts with the fuel. The produced CO2 is inherently separated from the air components, making CLC a promising technology for carbon capture and storage (CCS). CLC of biomass combined with CCS (bioenergy CCS; BECCS) is a way to generate negative CO2 emissions and thus interesting for climate change mitigation. Undesirable chemical reactions between ash and oxygen carriers are a challenge in BECCS because of the reactive nature of biomass ash. This article examines two low-cost steel industry byproducts that have shown desirable fuel conversion properties in CLC: iron mill scale (Glödskal B) and steel converter slag (LD-slag). Their interactions with potassium ash model compounds (KCl, K2CO3,K2SO4, and KH2PO4) in a reducing atmosphere have been investigated. Mixtures of oxygen carriers and potassium salt have been reduced for 6 h in CO and steam in a laboratory-scale fixed-bed reactor at 850 °C. The reduced samples have been analyzed with SEM/EDS and XRD. The reactivity of the mixtures during reduction and oxidation has also been examined by thermogravimetric analysis (TGA). K2CO3 increased the reaction rate for the reduction of Glödskal and inhibited the reactivity of LD-slag. KH2PO4 formed a K−P−Fe component with apparent low melting temperature with Glödskal, causing agglomeration, and decreased the reduction/oxidation rate in TGA. KH2PO4 formed a K−P−Ca component with apparent high melting temperature with LD-slag causing agglomeration but the reduction rate was not affected. The study suggests that the iron mill scale and LD-slag should not be rejected as oxygen carriers for CLC based on potassium ash interaction.

oxygen carriers

potassium salts

chemical-looping combustion

ash interactions


Felicia Eliasson Störner

Chalmers, Space, Earth and Environment, Energy Technology, Energy Technology 2

Fredrik Hildor

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry 2

Henrik Leion

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Environmental Inorganic Chemistry 2

Maria Zevenhoven

Åbo Akademi

Leena Hupa

Åbo Akademi

Magnus Rydén

Chalmers, Space, Earth and Environment, Energy Technology

Energy & Fuels

0887-0624 (ISSN) 1520-5029 (eISSN)

Vol. 34 2 2304-2314

Negative CO2 emissions in the Nordic energy systems

Nordic Energy Research (NER), 2015-11-01 -- 2019-12-31.

Driving Forces

Sustainable development

Subject Categories

Energy Engineering

Atom and Molecular Physics and Optics


Areas of Advance




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