PhD Defence by Qian Ouyang

Principal supervisor
Professor Nicolas von Solms
DTU Chemical Engineering

Co-supervisors
Associate Professor Alexander Shapiro
DTU Chemical Engineering

Dr. Jyoti Shanker Pandey
DTU Chemical Engineering

Examiners
Associate Professor Wei Yan
DTU Chemistry

Associate Professor Livia Bove
Università Roma La Sapienza, Italy

Dr. Peter Herslund
Calsep, Denmark

Chairperson at defence
Associate Professor Xiaodong Liang
DTU Chemical Engineering

Popular Summary

Natural gas (main component CH4) still plays a key role in the global energy system, and carbon dioxide (CO2) is the main greenhouse gas causing global warming.
CH4-CO2 hydrate swapping is an attractive exploitation technique that can recover CH4 gas and store CO2 hydrate. The CH4 trapped in the hydrate is to be replaced by CO2 injected.
Exploitation of natural gas hydrates by injecting CO2 for CH4-CO2 hydrate swapping is such a strategy to harvest energy resources and reduce CO2 emission, contributing to meeting the increasing energy demand and mitigating the greenhouse effect.

This technique suffers from low efficiencies of CH4 gas recovery and CO2 hydrate storage, due to low CO2 injectivity caused by limited mass transfer within sediments. Concurrent CH4 gas recovery and CO2 hydrate storage is a trade-off that needs fully considered strategies for high efficiencies of both.

To tackle these problems, this work conducted the strategy of slow depressurization after CH4-CO2 hydrate swapping, and investigated this process of hydrate exploitation in multiscale systems containing bulk-water and multiple porous media.

The final goals of this combined strategy were to promote CH4 gas recovery and CO2 hydrate storage, and propose a reliable and robust protocol of natural gas hydrate exploitation through CH4-CO2 hydrate swapping combined with multistep depressurization.

The findings of this work accelerated the process of pilot-scale test of hydrate exploitation by this combined strategy.