Design Technologies for Multi-scale Innovation and Integration in Post-Combustion CO2 Capture: From Molecules to Unit Operations and Integrated Plants
The efficient capture of CO2 is reasonably regarded as one of the grand challenges for the 21st century , considering that a single coal-fired plant may emit up to 25 million tons of post-combustion CO2 per year . Available capture technologies are predominantly based on the use of intermediate materials, namely solvents that enhance the separation efficiency by selectively dissolving CO2 . Amine-based organic compounds are among the most common solvents employed in the widely utilized chemical absorption process. The globally observed preference towards solvent-based absorption is largely because the technology is well established, 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 the increased energy required for solvent regeneration, environmental aspects associated with the toxicity of the solvent and solvent derivatives, the presence of contaminants that affect the solvent performance and lead to solvent degradation and the corrosion of equipment caused by the solvent itself.
Clearly, such shortcomings require significant advances in solvent performance, supported by the additional introduction of considerable improvements in the overall process systems that emit and capture CO2. Despite previously intense research effort in this direction, solvent-based absorption processes are reported to introduce a cost penalty of over 40% to the operation of the plant . Approximately 70% of these costs are due to the use of thermal separation processes for solvent regeneration . Such estimates bring the capture cost in the range of $52-89 (€36-62)/ton (Note: The original prices reported in  are $45-65 (€31-45)/ton of CO2 for a coal-fired power plant with a capacity of 900-300MW in 2004. The above prices correspond to 2011 rates in $ accounting for inflation and transformed into € using recent exchange rates) of CO2 , which is well above the current trading price (at €16.5 on 24-03-2011).The planned carbon tax in the UK is £16 (€18) in 2013 and £30 (€34) in 2020 (based on 2009 prices) . Therefore, there is a lack of economic incentive in the industry to capture CO2 at the current high cost. A new technology towards breakthrough innovation in solvent based post-combustion CO2 capture for enhanced energy efficiency, improved cost effectiveness and increased process sustainability and environmental benefits is developed. Advances in the identification of highly performing solvents and solvent blends in CO2 absorption, the design of innovative separation equipment internals, and the development of optimal process configurations enable cost reductions of at least 20-30% per ton of CO2 captured. Such achievement can have a tremendous impact in several industrial applications such as gas-fired, coal-fired, and lignite-fired power plants as well as and quick-lime production plants where solvent based post-combustion CO2 absorption can become a viable solution.
The current project adopts a holistic approach towards the fulfillment of the outlined goals accomplished through research and development at multiple levels within an integrated framework.
At the molecular level, the use of computer aided molecular design tools supported by accurate and adequately validated thermodynamic models enables the exhaustive investigation of the performance of multiple solvents and solvent blends in post-combustion CO2 absorption processes. The solvent blends are systematically assessed and rank-ordered against their performance towards the satisfaction of relevant process, economic, operability and sustainability criteria. The optimal solvents and solvent blends are expected to exhibit significantly better characteristics than currently used solvents in terms of energy requirements and overall environmental impact.
At the unit operations level, the design of innovative process configurations and column internals that are specifically tailored for the employed solvents enhance the efficiency of the absorption based separation. Advanced modeling and optimization tools in conjunction with thorough experimental procedures ensure the achievement of high mass transfer rates and optimal flow patterns.
At the plant level, the comprehensive analysis of the interactions among an existing power plant and the added solvent based post-combustion CO2 capture unit enables the optimal allocation of resources for improved energy savings and the efficient integration of the new CO2 capture process components.
Pilot plant testing of the newly developed technology under operating condition encountered in practical applications ensures process stability and consistency.
Several industrial applications in power production and chemicals manufacture are scheduled for comprehensive study, analysis, and evaluation thus resolving all related technical and engineering issues.
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