Huge underground gas reserves, up to 16% of the total reserves, remain unused. The natural gas in these fields is too contaminated for exploitation. With existing technology, cleaning these fields is much too costly. As a result of research done by Ralph van Wissen MSc these fields may in the future become more profitable. In cooperation with Shell, Van Wissen developed a cleaning technique based on the centrifugal separation of gasses. He further built a prototype that can be scaled up to be used in producing natural gas. Van Wissen has obtained a doctorate from the Eindhoven University of Technology on Monday 4 December.
Depleted gas reserves
According to most predictions, the world’s gas reserves will be depleted within this century. Therefore, the discovery of new reserves and the full exploitation of existing reserves are high on the agenda of the big oil and natural gas companies. It is almost impossible to convey the economic value of 16% of the world’s reserves. They represent more that 360 times the annual natural gas production of Shell, Exxon, and BP put together.
Relatively clean gas mixture
These unrecoverable gas reserves are contaminated with CO2 and H2S (hydrogen sulphide). Current cleaning processes, which use selective absorption techniques and membranes technology, are too limited. If the concentration of CO2 and H2S is more than 15%, more energy is lost in these cleaning processes than is gained in natural gas. With the new technique developed by Van Wissen it is possible to clean highly contaminated natural gas (containing 15% to 70% CO2 and H2S) and turn it into a relatively clean gas mixture with only 5% contamination. The resulting energy loss is only a very small percentage. Conventional cleaning processes can be used without much extra costs or waste of energy to further purify this mixture.
Centrifugal gas separator
The trick of the trade is the centrifugal gas separator’s expansion tank. In this tank the gas mixture expands very fast, resulting in the condensation of CO2 and H2S particles. This condensate can be compared to the small cloud of vapor that appears when opening a bottle of champagne. The natural gas and the condensed droplets subsequently flow through a rotating cylinder. In this cylinder, which is made up of many thin channels, the centrifugal powers press the droplets to the outer side of the channels. The CO2 and H2S can then be relatively easily separated from the natural gas.
Prototype
The prototype Van Wissen built can process a gas stream of 60 m3 an hour. Very little, compared to the more than a thousand times larger output of an average natural gas field. That is why Van Wissen paid special attention to the proper dimensioning of his prototype to enable up scaling, so it can be used in actual practice. He succeeded and Shell plans to further develop this technology on the basis of his prototype.