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SCARLET Report Summary

Project reference: 608578
Funded under: FP7-ENERGY

Periodic Report Summary 1 - SCARLET (Scale-up of Calcium Carbonate Looping Technology for Efficient CO2 Capture from Power and Industrial Plants)

Project Context and Objectives:
The calcium carbonate looping (CCL) process is a second generation post-combustion CO2 capture technology using limestone as solid sorbent. The CCL process has a high efficiency and low CO2 avoidance costs compared to first generation CO2 capture technologies, in particular as a retrofit of existing power plants and industrial process plants (e.g. cement, steel, chemical industries). The low price and high availability of natural limestone in various locations on earth is a further advantage of the CCL process which is being investigated in SCARLET.

SCARLET is a 3-year research project funded by the EU 7th Framework Programme coordinated by the Institute for Energy Systems and Technology (EST) of Technische Universität Darmstadt (TUD). The project runs from April 2014 to March 2017. The major aim of the SCARLET project is to obtain reliable information and tools for the scale-up of the CCL process and pre-engineering of a 20 MWth CCL plant by continuous self-sustaining pilot plant operation. The project shall provide a technical, economical, and environmental assessment of this promising technology, as well as the fundamental expertise needed for the scale-up and integration of pre-commercialisation CCL facilities. The following objectives are defined to reach this aim: The key process parameters and control strategies shall be identified by testing the CCL process in an upgraded 1 MWth pilot plant at Technische Universität Darmstadt (see Figure 1) with hard coal and lignite as fuel, aiming a target of at least 90 % CO2 capture and an efficiency penalty lower than 3.5 % points. Scale-up tools and guidelines for CCL reactor design and process layout shall be developed and validated by experimental data from the 1 MWth CCL pilot plant. The results of pilot testing as well as the developed scale-up tools and guidelines shall lead to the design, cost estimation, and risk assessment of a 20 MWth CCL pilot plant using the Emile Huchet Site of E.ON France Power S.A.S. Furthermore, the techno-economical and environmental impact of the CCL application to hard coal and lignite fired power plants as well as cement and steel industry at commercial full scale shall be determined.

Figure 1: Building of 1 MWth CCL pilot plant at TU Darmstadt (left: outside, right: inside)

The SCARLET consortium consists of 11 international members including two universities, a research organization and 8 industrial partners. The strong consortium with an excellent industrial support provides a valid approach to the key challenges for the scale-up of the CCL technology.

Figure 2: SCARLET consortium (2 universities, 1 research organization, 8 industrial partners)

Project Results:
The existing 1 MWth CCL pilot plant has been upgraded for higher capacity and operability in order to bring the plant configuration as close as possible to the set-up of an industrial plant. The CCL process can now be investigated under realistic conditions and with various fuels:

• Upgrade of thermal capacity to allow increased carbonator velocities similar to full-scale CFB plants
• Integration of flue gas recirculation for the calciner to realize oxy-fuel combustion
• Cone valve for controlling the flow of solids between the two CFB reactors
• Coal supply systems for crushed hard coal and for lignite
• Equipment for SO2 and steam addition to the carbonator
• Improved design of reactors and components
• Integration of an automated limestone supply system
• Enhanced sampling systems
• Enhanced measurement equipment

The scheme of the upgraded pilot plant is shown in Figure 3. The flue gas from a coal-fired furnace is introduced into the carbonator, where CO2 is absorbed by CaO. The CaCO3 is regenerated in the calciner at increased temperature by firing coal with O2 and recycled flue gas. Long-term pilot testing fueled with hard coal and lignite will be performed to determine the effect of a number of process parameters (i.e. solids inventory, solids circulation between reactors, reactor temperatures, fuel type and size, steam and sulphur concentration in the carbonator) on the CO2 capture rate and the process efficiency.

Figure 3: Scheme of 1 MWth CCL pilot plant at TU Darmstadt

The first long term test campaign with hard coal has been carried out. The plant was operated for 4 weeks with hard coal in two different particle sizes. Crushed hard coal and pulverized hard coal were fed to the calciner in this test campaign to investigate the effect of different sizes of coal particles in the process. For more than 400 hours, CO2 was captured in the CCL process at various operating points reaching a total CO2 capture efficiency higher than 90% and long-term stability of the process.

The pilot tests provide experimental data for the validation of steady-state and dynamic process models as well as 3D models based on computational fluid dynamics (CFD), which have been developed for the scale-up and optimisation of the CCL process. Steady-state and transient process models of the CCL process have been developed. The models take into account the sorbent reactivity behavior and the particle distribution in the CFB system according to tested models from the literature. The implementation of the physical sub-models was carefully checked and validated using simple simulation cases. The comparison of numerical results with experimental data was in good agreement, proving the prediction of mass and energy balances. Another important task was the development of 3D CFD models using different numerical approaches. A sophisticated drag model using the energy-minimization-multiscale method (EMMS) into the two-fluid model (TFM) was applied. The developed EMMS model was also implemented into the DEM (discrete element method) modeling approach. The accuracy of numerical predictions with the EMMS drag model exceeds the simulation results using conventional drag models such as Gidaspow or Syamlal O’Brien. The reactive flow simulation of the carbonator yielded good results regarding the CO2 concentration at the reactor outlet. However, the developed reactive 3D models need further validation. Especially several sorbent properties need to be determined in order to fully validate the reaction models. The TFM approach, using three Eulerian phases, was also applied to the calciner reactor. The modeling of the calciner reactor was realized by two solid phases, i.e. coal (fuel) and limestone (solid) and one Eulerian gas phase. A parametric study obtained promising results of the calciner. In the next phase of the project, design modifications of selected components will be performed and analyzed by CFD simulation. The developed models will be used for scale-up purposes.

The experience from pilot testing and the validated models will particularly be used for the conceptual design and pre-engineering of a 20 MWth CCL pilot at the Emile Huchet power plant in France, which is considered as the next step towards the industrial implementation of the CCL process. Health, safety, and technical risks will be assessed, and the costs for erection and operation of the 20 MWth CCL pilot will be determined. Finally, the full-scale implementation of the CCL process into hard coal and lignite fired power plants as well as industrial (cement and steel) plants will be evaluated. A techno-economic analysis for each type of host plant will be performed to estimate electricity and CO2 avoidance costs in order to compare the CCL process with other CO2 capture technologies. The environmental impact of CCL applications will be determined by a life cycle analysis.

Potential Impact:
The CCL process has been evaluated to be more efficient than first generation CCS technologies like amine post combustion capture and oxy-combustion. An efficiency penalty as low as 3 % points (without compression of CO2) and CO2 avoidance costs as low as 15-20 €/tCO2 have been determined for a retrofit of coal-fired power plants. Limestone is a non-hazardous natural resource available in large quantities, and CCL does not produce any degradation product or residues with impact on health, safety and environment (HSE). Instead, spent limestone could be utilised for cement production or flue gas desulphurisation. CCL has now been demonstrated for very short periods and is still considered immature for large scale demonstration or even commercial implementation. Hence, more experience should be obtained to be able reach the next technology development step represented by a 20 MWth pilot plant.

SCARLET will bring CCL to this next level of maturity, preparing the ground for pre-commercial demonstration of the technology. By addressing the key challenges and demonstrating the technology at pilot scale of 1 MWth, the project will give confidence for investments into a larger-scale 20 MWth unit. With the help of validated simulation tools for scaling up the CCL process, scaling criteria can be determined to facilitate the design of a future large-scale demonstration project, aiming at short term commercialisation of the process. Besides, the SCARLET project identifies the technical and economic integration of CCL into a commercial power plant, a steel plant, or a cement plant to optimise performance and minimise technical risks, targeting efficiency, reliability, and operability. After successful demonstration of units of the 20 MWth size, the technology will be ready for design and installation of commercial size units on utility boilers and other sources where CO2 reduction is required.

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Meermann-Zimmermann, Melanie (EU-Liaison Officer)
Tel.: +49 6151 16 75972
Fax: +49 6151 16 2478
Record Number: 182023 / Last updated on: 2016-05-25
Information source: SESAM