Investigation of biomass alkali release in a dual circulating fluidized bed chemical looping combustion system
Journal article, 2021

Chemical looping combustion (CLC) of biomass is a promising technology for power generation with integrated carbon capture. In CLC, alkali content of biomass poses potential issues of bed agglomeration, as well as heat exchanger fouling and corrosion. The fate of biomass alkalis was investigated in a dual-interconnected circulating fluidized bed CLC system. Experiments were conducted in oxygen carrier aided combustion (OCAC) and CLC modes. Ilmenite and braunite oxygen carriers and three biomass fuels (wood pellets, wood char, straw pellets) were tested. Flue gas alkali emissions in the air reactor (AR) and fuel reactor (FR) were measured with a surface ionization detector (SID). Results showed that CLC operation yields gas-phase alkali emissions that are up to 15 times higher than in comparable OCAC operation. Results analysis concluded that increased alkali emissions in CLC arise from the steam atmosphere in the FR, whereby steam accelerates the decomposition of alkali compounds in the biomass. Retention of alkalis in the condensed phase was found to be >97% for ilmenite and >92% for braunite CLC operation. Up to 60?80% of the retention was attributed to fuel ash formation. The residual retention was attributed to absorption of alkalis by the oxygen carriers. Absorption likely occurred mainly through formation of alkali manganates and silicates in braunite, and formation of alkali silicates, aluminosilicates, manganates, and titanates in ilmenite. Gas-phase alkali emissions in the AR, although less than in the FR, were found to occur due to combustion of unconverted fuel carried over from the FR to the AR.


Chemical looping combustion


Oxygen carriers


Ivan Gogolev

Chalmers, Space, Earth and Environment, Energy Technology

Toni Pikkarainen

Technical Research Centre of Finland (VTT)

Juho Kauppinen

Technical Research Centre of Finland (VTT)

Carl Johan Linderholm

Chalmers, Space, Earth and Environment, Energy Technology

Britt-Marie Steenari

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Anders Lyngfelt

Chalmers, Space, Earth and Environment, Energy Technology


0016-2361 (ISSN)

Vol. 297 120743

OxyCar-FBC, Oxygen Carriers in Fluidized Bed Combustion of Biomass

Swedish Energy Agency (43936-1), 2017-02-01 -- 2020-01-31.

Förbränningskemi för biomassa med syrebärarmaterial

Swedish Research Council (VR) (2016-06023), 2017-01-01 -- 2024-12-31.

Subject Categories

Energy Engineering

Chemical Process Engineering




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