Design and development of a downstream separation process for ethylene recovery within the e-Refinery framework

Design and development of a downstream separation process for ethylene recovery within the e-Refinery framework

Snoeks, Casper (TU Delft Applied Sciences)

Eral, H.B. (mentor)
Huesman, A.E.M. (graduation committee)
Kortlever, R. (graduation committee)
Burdyny, T.E. (graduation committee)

Delft University of Technology

2021-03-01

Electroreduction of CO2 into high-valued chemicals is a promising way to reduce CO2 emissions while simultaneously producing bulk chemicals currently produced from fossil-fuel feedstocks. The downside of this process is that conversion rates are low, meaning the resulting product stream is a complex gas mixture consisting primarily of reactants and by-products and a relatively small amount of product. This study focuses on the development of a new downstream separation process to capture ethylene from a mock-up reaction mixture (mole fractions C2H4/CO2/CO/H2/H2O : 20/55/15/15/5), based on low driving forces and suitable for application in a 100kW test case within the e-Refinery. An extensive literature study of numerous separation techniques for gases was conducted and adsorption was chosen as the most suitable option. After screening of various adsorbents, active carbon was selected as the most potential sorbent. Based on a selectivity analysis, the primary focus was on the behaviour of C2H4/CO2 on active carbon. Using a simple, custom-build set-up, transient breakthrough experiments were performed for this gas mixture and the resulting selectivity for an equivolume feed, yielded a lower separation performance than expected based on the ideal adsorption solution theory, respectively a selectivity of 1.5–1.7 versus 3.2–3.5. Additionally a theoretical model was developed using MATLAB, which described the velocity profile inside the adsorber column and could qualitatively predict breakthrough behaviour. Further analysis led to the conclusion that for a more accurate quantitative match between experimental and numerical results, isotherm parameters should be obtained from the same type of active carbon. Ultimately this technique could be used to increase the ethylene content in a CO2-bearing stream and pave the way for a new, energy-efficient method to obtain hydrocarbons, ethylene in this case, from an electrolyzer cell.

Adsorption
Ethylene capture
Breakthrough times
Activated carbon
Separation technology
e-Refinery
Numerical model

http://resolver.tudelft.nl/uuid:bcf6dd0c-ec98-474e-8d52-6f821f3ddd9a

2021-03-02

Student theses

master thesis

© 2021 Casper Snoeks