Determining the Fate and Operational Implications of Alkalis in Chemical Looping Combustion of Biomass
Licentiate thesis, 2020
Measurement of gas-phase alkali release in CLC was addressed through the design and construction of a modular and transportable surface ionization detector (SID) system, customized for alkali emissions measurement from the fuel reactor (FR) and the air reactor (AR) of CLC pilots. Gas-phase alkali emissions measurement showed that approximately 1-10% of fuel alkalis are released to the gas phase in CLC. The FR alkali emissions were found to rise with the fuel’s alkali content, while no definitive correlation was established for AR emissions. With respect to emissions distribution, AR emissions were found to be generally lower than that of the FR. Surprisingly, in several cases, AR emissions were equal or marginally higher than in the FR. Analysis presented in Paper III led to a preliminary conclusion that AR gas-phase alkali emissions likely occur due to char or ash carryover from the FR, whereby the transported alkali compounds release to the gas phase at the higher temperatures of the AR.
Papers I-III also established that >97% of fuel alkalis are retained in solid form. Although a major part of the alkali retention originates from fuel ash formation, significant retention likely occurs due to oxygen carrier interaction with the fuel’s inorganic content. In Paper III it was also found that in CLC, the steam-rich FR atmosphere enhances the gas-phase release of alkalis from decomposition of alkali carbonates and sulphates. This was established in tests comparing CLC operation with oxygen carrier aided combustion (OCAC).
Development of biomass CLC technology was also addressed in this thesis. Paper I demonstrated that gas conversion efficiencies of >96% can be achieved with mixed synthetic and natural oxygen carriers. Experiments in Paper II commissioned a new 10 kW CLC pilot and demonstrated that the implementation of a volatiles distributor in the FR can improve fuel gas conversion efficiency by up to 10 percentage points. Papers I and II also evaluated the interdependencies of the CLC system’s control parameters with gas-phase alkali release. It was concluded that CLC system control parameters, other than temperature, likely do not significantly influence and are not constrained by alkali release behavior.
chemical looping combustion
Chalmers, Space, Earth and Environment, Energy Technology
Chemical-looping combustion in a 100 kW unit using a mixture of synthetic and natural oxygen carriers – Operational results and fate of biomass fuel alkali
International Journal of Greenhouse Gas Control,; Vol. 88(2019)p. 371-382
Gogolev, Ivan, Amir H. Soleimanisalim, Carl Linderholm, and Anders Lyngfelt. "Commissioning, performance benchmarking, and investigation of alkali emissions in a 10 kWth solid fuel chemical looping combustion pilot."
Gogolev, Ivan, Toni Pikkarainen, Juho Kauppinen, Carl Linderholm, Britt-Marie Steenari, and Anders Lyngfelt. "Investigation of Biomass Alkali Release in a Dual Circulating Fluidized Bed Chemical Looping Combustion System."
Förbränningskemi för biomassa med syrebärarmaterial
Swedish Research Council (VR) (2016-06023), 2017-01-01 -- 2024-12-31.
OxyCar-FBC, Oxygen Carriers in Fluidized Bed Combustion of Biomass
Swedish Energy Agency (43936-1), 2017-02-01 -- 2020-01-31.
Chemical Process Engineering
Areas of Advance
Opponent: Docent Patrik Yrjas, Åbo Akademi University, Finland