(685c) Modeling and Economic Assessment of Rapid Thermal Vacuum Swing Adsorption of CO2 in Hollow Fiber Adsorbents

In recent years, there has been an increasing interest in capture and separation of carbon dioxide from flue gas due to concerns about rising CO₂ concentrations in atmosphere. The US Department of Energy investigated and concluded that the proposed CO₂ capture and sequestration (CCS) technology for retrofitting the existing coal fired power plants should not increase the cost of electricity beyond 35% [1]. Solid adsorbent based CO₂ separation process can potentially have lower energy requirements than liquid amine based absorption processes, which, in their current form, may increase the cost of electricity by 80% [2].

A novel process contactor in the form of hollow fiber loaded with amine sorbents was proposed and investigated for its application in a rapid thermal swing adsorption (RTSA) of CO₂ from flue gas [3]. Experimental studies of RTSA with hollow fiber amine sorbents demonstrated high breakthrough capacity and good stability during the rapid thermal swing. Also, mathematical modeling for the process was developed, rigorously validated and employed to study the economics of the process [4]. Although the process showed high promise in terms of energy recovery with its heat exchanger type configuration, the economic assessment of the process that meets the product purity and recovery constraints of 95% and 90% respectively could potentially have an increased cost of electricity beyond 35% [5]. The main reason for which is a high mass transfer diffusional resistance of high loaded silica supported amine sorbents, which results in curtailing the desorption step even before sweeping the bed  clean of CO₂. This prohibits the utilization of the maximum swing capacity that can be achieved with the given thermal swing.

In this work an advance over the current process configuration of rapid thermal swing by introducing vacuum in desorption step is investigated.  This can potentially increase the swing due to the additional driving force provided by the lower CO₂ partial pressure during desorption.  As a penalty, this incurs an additional compression step for the low pressure CO₂ which is produced. The design and economics of the proposed rapid thermal swing vacuum adsorption that meets the constraints of CO₂ product purity and recovery will be presented along with an analysis of advanced cases that might further improve the parasitic loads by targeted materials and process improvements.

References

[1]  Feeley. T.J., Fout, T.E., and Jones, A.P., DOE’s Carbon Capture and Sequestration R&D Program, paper presented at the PowerGen conference at Orlando, FL, Dec 2007

[2] NETL, Cost and Performance Baseline for Fossil Energy Plants, Volume 1: Bituminous Cal and Natural Gas to Electricity, Rev 2, Nov 2010

[3] Fan, Y., Lively, R.P., Labreche, Y., Rezeai, F., Koros, W.J., and Jones, C.W., ‘Evaluation of CO₂ adsorption dynamics of polymer/silica supported poly(ethylenimine) hollow fiber sorbents in rapid temperature swing adsorption’, Int. J. Greenhouse Gas Control, 2014, vol. 21, pp-61-71.

[4] Kalyanaraman, J., Fan, Y., Lively, R.P., Koros, W.J., Jones, C.W., Realff, M.J., and Kawajiri, Y., Modeling and Experimental Validation of Carbon dioxide sorption on Hollow Fibers loaded with Silica-supported Poly(ethylenimine), Chem.Engg Journal, 2015, vol 259, 737-751.

[5] Swernath, S., Searcy, K., Rezeai, F.,  Labreche, Y., Lively R.P, Realff M.J., Kawajiri, Y., Optimization and Techno economic Analysis of Rapid Thermal Swing Adsorption of Carbon Capture from Coal Fired Power Plant, Computers Aided Chem.Engg, 2015, vol. 36, 253-278