Experimental Characterization of a Novel Small-Scale Natural Circulation Loop Methanol Synthesis Reactor

Experimental Characterization of a Novel Small-Scale Natural Circulation Loop Methanol Synthesis Reactor

Basarkar, Pratik (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Large Scale Energy Storage)

van Kranendonk, Jan (mentor)
de Jong, Wiebren (mentor)
Goetheer, Earl (graduation committee)
Stikkelman, Rob (graduation committee)

Delft University of Technology

2018-08-30

The present-day industrialized nations reached high standards of living using cheap fossil fuel energy. The high CO₂ emissions as a result of burning these fuels over the years have started outpacing the natural carbon cycle, resulting in climate changes around the globe. We have reached a point in our history where merely reducing our carbon emissions would not solve the problem, rather carbon has to be captured from the atmosphere and either stored or converted to fuels. Converting the captured CO₂ into methanol has been gaining traction in recent years as it is not only an excellent fuel but also serves as the building block to manufacture other important chemicals like dimethyl ether (DME), paraffin, olefins, plastics and polymers.

This thesis focusses on the complete experimental characterization of a small scale, energy efficient methanol synthesis reactor modelled on the concept developed by Wim Brilman of the University of Twente, with respect to feed flow rates, methanol production and overall efficiency. The problem of comparative energy inefficiency of the Brilman reactor was solved by carrying out the reactions in a novel, natural circulation loop (NCL) fixed packed bed reactor with internal heat recovery using Cu/ZnO/Al₂O₃ as the catalyst. A mixture of H₂ and CO₂ in the molar ratio of 3:1-the optimum ratio for methanol production was fed into the reactor. A sensitivity analysis was carried out with regards to the sampling time of the liquids at the outlet and the reaction temperature. Maximum methanol productivity of 6.8 mmole (millimoles) CH₃OH/g_cat/h was obtained at 228 °C reactor wall temperature and 62 °C condenser wall temperature using 5 mm diameter pellets compared to 4.3 mmole CH₃OH/g_cat/h obtained by Brilman at 210 °C reaction temperature and 85 °C condenser temperature. Also, a high carbon conversion of 99.2% and methanol selectivity of 99.0% was achieved. The energy demand (in MJ/kg_CH3OH) was reduced from 75 in the Brilman reactor to 24 using the current design. From these results, it was established that methanol could be synthesized using a small, lab-scale reactor in an energy efficient manner.
It was further observed that reduced size of the catalyst did not contribute much to methanol yield due to the high-pressure drop. Finally, a brief analysis of the heat losses in the system led to the conclusion that an additional 14.6 W of heat would have enabled autothermal operation.  

methanol synthesis
small-scale
energy efficient

http://resolver.tudelft.nl/uuid:3f5c1c51-d04f-4026-88a5-0bb4c800cf2b

2020-08-30

Student theses

master thesis

© 2018 Pratik Basarkar