463790 The Effect of Stirring Rates on Natural Gas Hydrates (NGH) Formation in Flow Reactor System: Experimental and Practical Approach
The liquefaction of natural gas (LNG) is one of the major modes of natural gas transportation between different regions. The liquefaction of natural gas requires cooling up to -161oC and the cost of liquefaction can range from 3 $ to 10 $ per MMBtu (millions of British thermal units). So unless there is a demand for higher LNG prices, the liquefaction cost could negatively affect LNG business and make liquefaction projects unprofitable.
In order to cut down liquefaction cost, the researchers are trying to study gas hydrates as a potential mode of natural gas transportation and storage in future. Gas hydrates are crystalline meta-stable compounds, made up of water and gas molecules. One volume of hydrate can store up to 180 volumes of natural gas at STP (standard temperature and pressure). Therefore, the development of hydrate production plants holds particular importance in future.
In this work, the formation rate of gas hydrates in a high pressure autoclave flow reactor system has been studied at different stirring rates using a magnetic stirrer. In the first phase, the system was first cooled from 20 o C to 2 o C at constant pressure for 18 hours. Then immediately in second phase, the system was left stable at 2 o C for another 18 hours at constant stirring rate. The stirring rates were varied between 100-1400 Rpm (Rotations per minute) for each experiment and the gas hydrate crystal formation was observed by measuring pressure drop across the system during the second phase. The experimental results show that for a chosen system, the stirring rate does have an effect on the rate of gas hydrate crystal formation. The maximum gas hydrate crystal formation was observed within the stirring range of 550-750 RPM. It was found that for a chosen system there exists a threshold stirring limit, above or below which little or no hydrate crystal formation takes place. This fundamental study can be useful for modeling purposes and designing of a pilot scale hydrate production plant to study the economical and safety factor associated with natural gas hydrate storage and transportation.
This work was made possible by NPRP grant # 6-330-2-140 and GSRA # 2-1-0603-14012 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.