Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - ROLINCAP (Systematic Design and Testing of Advanced Rotating Packed Bed Processes and Phase-Change Solvents for Intensified Post-Combustion CO2 Capture)

Teaser

Solvent-based absorption/desorption systems represent a well-established and the most mature technology for large-scale CO2 capture. The conditions for both absorption and solvent regeneration are relatively easy to meet and the process can be easily retrofitted onto existing...

Summary

Solvent-based absorption/desorption systems represent a well-established and the most mature technology for large-scale CO2 capture. The conditions for both absorption and solvent regeneration are relatively easy to meet and the process can be easily retrofitted onto existing plants. Major downsides involve: a) very large absorption and striping columns required to process power plant flue gases, translating into large capital cost; (b) the high energy (heat) required for solvent regeneration which reduces net electricity output from a power plant, and (c) the environmental aspects associated with the toxicity of the solvent.
ROLINCAP is focusing on two new types of solvents and separation process technologies:
- Phase-change solvents are able to significantly reduce the energetic requirements of solvent regeneration by more than 50% compared to conventional monoethanolamine (MEA) solvent used widely in CO2 capture. Their reaction with CO2, followed sometimes by an increase in temperature, results in separation of large amounts of water and solvent (Figure 1), leaving the CO2 captured in a CO2-rich, liquid stream with much less water and amine (Figure 2). These two liquid phases can be separated mechanically due to difference in density with practically very little energy.
- RPB columns enable a significant enhancement of the mass−transfer rate between the gas and liquid phases (Figure 3) and significant reduction of corresponding capital costs.
Technical objectives
From a technical perspective ROLINCAP has addressed the screening, design and pilot testing of optimum phase-change solvents, RPB columns and advanced absorption/desorption flowsheets that:
• Exhibit as low as possible regeneration energy requirements.
• Enable reductions in the capital expenditures compared to conventional packed bed absorption/desorption systems.
• Combine superior sustainability properties.
• Incorporate significant improvements in column features.
Scientific objectives
The proposed technical objectives were sought through the development and use of advanced computer-aided tools, including:
• Thermodynamic models in the form of the SAFT equation-of-state for the prediction of solvent properties exhibiting multi-phase behaviour.
• An optimization-based CAMD tool with the aim to identify novel phase-change solvents.
• A systematic and holistic sustainability framework to assess the cradle-to-grave environmental impacts
• Optimization-based design of RPB and conventional packed-bed columns in view of phase-change solvents.
• Whole-systems optimization of the power plant, solvent system and separation/compression process.

Work performed

Work has achieved the development of:
Predictive models of the fluid-phase behaviour of aqueous solutions of linear, branched, and cyclic amines, with or without carbon dioxide, were developed within the SAFT-γ Mie group-contribution EoS (Figure 4). Using literature data and data generated within the ROLINCAP project, a total of 12 new groups as well as 55 group-group interactions (Figure 5) were estimated in order to model the mixtures of interest.
We approached for the first time the design of phase-change solvents through optimization-based Computer-Aided Molecular Design (CAMD) (Figure 6). A novel phase-change solvent mixture has been identified and tested experimentally, exhibiting very high equilibrium, cyclic capacity and lower vapour losses compared to existing phase-change solvents.
We considered as part of CAMD, cradle-to-gate LCA metrics describing the impact of all the materials and energy carriers utilized during the solvent production.
We have developed (Figure 7) appropriate models used for the design of advanced flowsheets suitable for phase-change solvents and to assess their performance under the influence of disturbances.
A reference dynamic process model for carbon capture with phase change solvents using PRB for the absorber and the stripper was developed (Figure 8). Case studies were carried out by both steady state and dynamic simulations to investigate the impact of rotating speed, the flow rate of lean solvent on the mass transfer performance as well as the dynamic behaviour of the RPB absorber in the PCC process.
A pilot scale, absorption/desorption pilot plant was constructed and tested (Figure 9). The novel phase-change solvent mixture has exhibited desirable phase-separation, capture performance and regeneration energy requirements.
An RPB absorption-desorption has been constructed and tested for phase-change systems (Figure 10). A novel desorber with an integrated spinning reboiler was also tested. The system was tested with different packing material geometries. Testing of the novel phase-change solvent resulted in very low regeneration energy requirements.
The novel phase-change solvent and process systems were included in a technoeconomic study for integration with a lime and a natural gas power plant. The resulting cost per ton of CO2 captured for the new solvent is much lower than that of conventional CO2 capture solvents.
The work of ROLINCAP resulted in two patents, whereas the new developments in thermodynamic modeling of phase-change solvents have been included in the commercial process simulation software gPROMS. New research projects have also started in on order to further advance the ROLINCAP technologies.

Final results

The progress beyond the state of the art is summarized as follows:
- A computer-aided approach is developed and used to support the identification of new phase-change solvents, the rigorous characterization of phase-change behavior, and their process performance in both packed and rotating packed-bed processes.
- New group-group interaction parameters are developed for structures observed in phase-change solvents.
- They are used in the GC SAFT-γ-Mie EoS to rigorously predict the vapour-liquid-liquid equilibrium performance of phase-change solvents.
- A novel phase-change solvent was selected using a CAMD approach which considers multiple criteria pertaining to thermodynamics, reactivity and sustainability.
- The sustainability assessment is performed during CAMD through a holistic framework.
- Process flowsheets were designed using optimization techniques to determine the optimum operating conditions.
- RPB process models were developed and their operating conditions were determined using optimization approaches.
- Packed bed and RPB pilot plants were developed and tested with a novel phase-change solvent. The RPB plant includes a novel RPB desorber with spinning reboiler.
Potential impacts
Technological impacts
The technologies developed in ROLINCAP resulted in:
• Up to 40% reduction in costs per ton of CO2 captured in power and lime production plants compared to conventional solvent Monoethanolamine
• Experimentally verified regeneration energy requirements of the CO2 capture plant up to 55% lower than conventional solvent Monoethanolamine.
• A novel solvent mixture which exhibits lower corrosion than Monoethanolamine and similar viscosity.
• RPB columns which are approximately 80% shorter compared to packed bed columns.
Socio-economic impacts
Due to the use of phase-change technologies it is expected that:
- The new solvent and process systems developed in ROLINCAP will result in up to 40% lower environmental impacts.
- The much lower cost of CO2 capture will provide significant motivation for the proliferation and wider adoption of CO2 capture systems in industry.

Website & more info

More info: http://www.rolincap-project.eu.