(58d) Analysis of Different Solvent Performance in UKy-CAER’s 0.7 MWe CO2 Capture Pilot Plant

To mitigate costs associated with implementing post-combustion CO₂ capture (PCCC) technologies, and to make them commercially viable for application in electric power generation and utility plants, different research paths are continually being explored. To this end, UKy-CAER has developed and scaled up its PCCC technology at a 0.7 MWe scale integrated with a 750 MWe commercial coal-fired power plant at E.W. Brown Generating Station located in Harrodsburg, Kentucky in a project which was primarily funded by the U.S. Department of Energy, National Energy Technology Laboratory (DOE NETL).

In the UKy-CAER CO₂ technology, novel concepts are employed in a heat integrated process to maximize heat utilization to lower the parasitic energy of the capture process. These include, first, a two-stage stripping process for solvent regeneration for enhanced solvent capacity and a reduction in the associated energy for regeneration. Here, after the conventional primary steam-driven solvent regeneration, the lean solvent is sent to a secondary air-stripping column where air is used counter-currently to further lower the lean loading of the solvent providing a higher free-amine solvent to the top of the absorber. The higher CO₂ volume air from the top of the secondary stripper is recycled to the plant boiler as secondary combustion air, which in turn would increase the amount of CO₂ entering the absorber. The lower liquid phase CO₂ concentration from the leaner solvent and higher gas phase CO₂ concentration will increase the driving force for CO₂ diffusion through the liquid/gas reaction film with resultant higher mass transfer. Second, a heat integrated liquid desiccant-based cooling tower loop recovers waste energy from the CCS, improves power plant efficiency and reduces parasitic load. The benefits for economic savings are derived with the use of advanced solvents with the process.

In this work, the performance of two advanced solvents were evaluated to demonstrate the energy savings of the process. For the more energy efficient advanced solvent, a reduction of about 36% in regeneration energy was obtained relative to DOE reference case 10. The energy ranged from 900 – 1500 Btu/Ib CO₂ from the parametric studies. The impacts of process parameters such as solvent circulation, lean loading, stripping temperatures, intercooling effects among others were examined. The heat integrated process is impacted by many process variables acting in tandem. Statistical analysis was used to determine the relative impacts of process variables and showed that intercooling effects in the absorber were more significant for the faster kinetics solvent from the observed temperature profile providing insights to the different behavior of the solvents and how the process could be operated to maximize the energy savings.