Abstract
Carbon removal from the atmosphere and Carbon Capture and Storage (CCS) from biomass have
recently been emphasized as important contributors to reach EU climate neutrality by 2050.
Chemical Looping Combustion (CLC) is an attractive technology in this respect, as it can convert
biogenic fuels with high electric efficiency and relatively low carbon capture cost [1].
The work described in this paper was in support of the BioNETzero project, funded through the
EU’s Horizon Europe program, that aims to advance biomass utilization for sustainable heating
and/or power generation [2]. One of the technologies that is explored is chemical looping
combustion based on biomass feedstocks, which will be demonstrated in experimental facilities at
pilot scale. Although there is broad experience of conducting numerical simulations to study
fluidized bed reactor hydrodynamics, including non-reacting CLC applications, there have
historically been few studies evaluating reacting biomass-fueled CLC. Previous simulations
employed three dimensional unsteady non-reacting CFD to evaluate the hydrodynamic behavior
of the 150kW CLC unit at SINTEF Energy. This work was done using the Neptune_CFD code,
which is based on an Euler-Euler framework [3]. The present work aims to extend the previous
simulations to include the reacting portion of the CLC process, which is a key step in the CFD
validation and subsequent CLC scale up design activities.
Numerical simulations of biomass combustion in the 150kW CLC unit of SINTEF Energy in
Trondheim, Norway, are performed using full three-dimensional unsteady computational fluid
dynamics (CFD) simulations. In addition to the air and the fuel reactors, the simulations also
include the lifter that transfers solids from the bottom of the fuel reactor to the bottom of the air
reactor. Furthermore, to obtain the appropriate pressure conditions within the unit, which is
required in order to predict the correct circulation rates, all connecting parts, such as loop seals
and cyclones, are also a part of the simulation domain. By comparing with results from
corresponding test campaigns [4], the simulations verify that, even for this design that does not
include a carbon stripper and has a relatively short residence time in the fuel reactor, the CO2
capture rate is high, above 95%, and the biomass-fuel conversion rate is around 80% without
oxygen polishing. This justifies that the simulation framework used in this work can be utilized as
a tool to design a modified fuel reactor with an increased fuel conversion rate. This is strictly
required for fuels with less reactive chars than the woody biomass used in these studies. In addition
to this, the simulations are also used to investigate in more detail the solid circulation rate, which
is not known from the experiments, as well as reactor design issues, like for example the propensity
for particle build-up in the air reactor cyclone. The numerical experiments performed in the
simulations are also intended to provide informed design guidance for larger scale reactors, where
fuel conversion is expected to be higher. Furthermore, studies evaluating the impact of different
oxygen carriers on the overall system performance could provide useful insights prior to producing
and acquiring new material.
The validated CFD simulation framework will be used to assist in reduced order modeling
approaches and surrogate model development that will be instrumental in the scale up to industrial
applications. This approach aims to provide more informed decision-making for the full-scale
process designer across a range of conditions and to provide risk mitigation prior to large scale
project execution.
ACKNOWLEDGEMENTS
BioNETzero is an EU-funded project that has received funding from the European Union’s
Horizon Europe Research and Innovation Programme under Grant Agreement N 101146616.
The Neptune_CFD code and usage license was made available through IMFT. High Performance
Computing resources were provided by the CALMIP supercomputing cluster at IMFT.
REFERENCES
[1] A. Lyngfelt, A. Brink, Ø. Langørgen, T. Mattisson, M. Rydén and C. Linderholm, "11,000 h
of chemical-looping combustion operation—Where are we and where do we want to go,"
International Journal of Greenhouse Gas Control, vol. 88, pp. 38-56, 2019.
[2] "BioNETzero," [Online]. Available: https://bionetzero.eu/.
[3] L. Sun, E. Masi, O. Simonin, Ø. Langørgen, I. Saanum and N. E. L. Haugen, "Threedimensional
unsteady numerical simulation of a 150 kWth full-loop chemical looping
combustion pilot with biomass as fuel: A hydrodynamic investigation," Chemical
Engineering Science, vol. 260, no. 117835, 2022.
[4] Ø. Langørgen, I. Saanum, R. Khalil and N. E. L. Haugen, "Evaluation of CLC as a BECCS
technology from tests on woody biomass in an auto-thermal 150-kW pilot unit,"
International Journal of Greenhouse Gas Control, vol. 130, no. 104006, 2023.