Do we want them or not? Gas hydrate inhibition and promotion in practice
Gas hydrates are best known as a flow-assurance issue in oil and gas production. In order to prevent gas hydrate formation at conditions of low temperature and moderate pressure, vast amounts of inhibitors such as methanol and glycol are typically added to the production stream to lower the temperature of hydrate formation to below the production temperature. In order to design on- and offshore processes which handle hydrocarbon streams it is thus necessary to understand (measure and model) phase equilibrium in these multiphase (gas/liquid hydrocarbon/aqueous) systems.
In an effort to reduce the usage of these thermodynamic inhibitors, so-called low-dosage inhibitors have been studied and are in use, where the required amounts are orders of magnitude less. Usually these are polymers which have biodegradability issues, prompting the search for more environmentally friendly inhibitors, perhaps inspired by antifreeze proteins found in nature.
On the other end of the scale, hydrates are being explored as separation agents for power plant flue gas in carbon capture applications, since hydrates are selective for carbon dioxide. Here the formation of hydrates is desirable and research into so-called promoters is underway, looking for substances that lower the pressure of hydrate formation.
Finally, naturally occurring hydrates in the earth may provide an energy source for the future – a resource which might be produced by replacing the methane in the hydrate with carbon dioxide in a so-called “swapping” process, thereby producing potentially carbon-neutral fossil energy.
This talk gives an overview of recent research addressing these various aspects of gas hydrates.