title: Design of a 2 MWₜₕ Indirectly Heated Carbonate Looping Demonstration Facility at a Lime Plant in Germany
Creators: name: Greco-Coppi, Martin
name: Dinkova, Anna
name: Hofmann, Carina
name: Walter, Diethelm
name: Böge, Kyra
name: Ströhle, Jochen
name: Epple, Bernd
Publisher: name: UNSPECIFIED
Year: 2024

description: Lime is crucial for many sectors of the economy including construction, agriculture, power generation, and manufacture. Lime plants are responsible of about 1.4 % of the global anthropogenic emissions of CO2. The majority of these emissions (over 60 %, according to IEA 2020), generated by the calcination of CaCO3 (i.e. process emissions), can only be avoided through efficient CO2 capture.
To capture the CO2 process emissions, post-combustion and oxy-fuel combustion technologies have the potential to be deployed industrially. Among them, Carbonate Looping (CaL) is one of the most promising processes because of its competitive CO2 avoidance costs and low energy requirements (i.e. specific primary energy consumption per CO2 avoided, SPECCA) (e.g. Astolfi et al. 2019). It uses CaO as sorbent to bind CO2 in a carbonator. The CO2 is released in an oxy-fired calciner, operating at around 900 °C, exiting in a high purity stream. For the particular case of the cement and lime industry, the CaL process can exploit the synergies of the calcination; thus, increasing the overall economic and thermodynamic efficiency.
To avoid the manifold penalties associated with oxy-firing the calciner (e.g. capital and operation cost of an air separation unit, contamination of CO2 stream, and increase in SPECCA), the heat can be provided indirectly through an external combustor. A proven way to do this is via heat pipes, which transfer heat by means of evaporation and condensation of a working fluid, e.g. sodium. The viability of this Indirectly Heated Carbonate Looping (IHCaL) process was demonstrated with more than 1000 hours of operation in a 300 kWth pilot facility at the Technical University of Darmstadt, Germany. Some of the most important milestones were: capturing CO2 from real combustion flue gas, with more than 85 % capture rate in the carbonator; recirculation of combustor flue gases into the carbonator; and fuelling of the combustor with propane, coal, and solid recovered fuel (SRF) (Hofmann et al. 2022; Reitz et al. 2016). Nevertheless, still some key elements have to be demonstrated in order to deploy the IHCaL technology into the industrial scale (cf. Greco-Coppi et al. 2021).
This work presents the design of a 2 MWth demonstration facility with the main objective of driving the IHCaL forward into the full-scale application for the decarbonization of lime and cement production. Lime Plant Hönnetal, in Germany, was selected as the host facility. For the design of the demonstration plant, reactor and process simulations were performed. The sorbent reaction and deactivation models were developed using data from thermogravimetric analysis (TGA). The reactor models were validated with the results from the pilot testing in the 300 kWth scale. These models were integrated in the Aspen PlusTM process models and used to optimize the design of the demonstration facility.
The objectives of the demonstration plant are: (i) demonstrate the application of the IHCaL into an industrially relevant environment; (ii) optimize and validate the utilization of solid fuels (including SRF) in the combustor with capture rates higher than 90 %; (iii) deploy a solid/solid heat exchanger to recover heat between the solid circulating streams; and (iv) demonstrate the feasibility to operate the indirectly heated calciner in industrially-relevant conditions (CO2 recirculation and steam fluidization). 
Within this work, the methods for the scale-up will be discussed, the design of the plant will be presented, and the operating conditions will be reported. The construction of the demonstration plant may take place within a follow-up project to the ACT ANICA project, starting in the year 2024. In that case, the demonstration facility would be operative by 2026; thus, enabling a first IHCaL industrial application into a lime or cement plant by 2030.