Twister Supersonic Gas Conditioning Process

Abstract

Abstract Twister Supersonic Separator is an innovative and revolutionary gas processing system. The Twister technology was developed by Shell. Twister B.V. was launched as a separate company in April 2000 by Shell Technology Investments Partnership, a 50/50 venture between Shell and the Beacon Group. Twister Supersonic Separator is the resulting synergy from combining aero-dynamics with the traditional gas processing concepts of thermodynamics and fluid dynamics. Twister is based on the following concepts (Figure 1):Gas is expanded in a Laval nozzle to supersonic velocities with resulting lower temperatures.Nucleation of water and hydrocarbon occur, followed by growth of liquid droplets.The gas and liquid droplets enter the wing section, where a very high swirl is created and the liquid droplets are centrifuged onto the walls, creating a liquid film.The gas and liquids are separated in the drainage section.Pressure is recovered in the diffuser section, to about 70– 80% of the initial pressure. This is done without chemicals or rotating equipment, and requiring minimum space and weight, thus saving significant capital and operating costs. Figure 2 shows the phase envelope of a natural gas and the water concentration curve. Twister is compared with the Joule-Thompson Valve and the Turbo- Expander. In this example all three processes have the same outlet pressure (sales pressure), which is typical for most applications. Joule-Thompson is an adiabatic process and the least efficient. Turbo-expander is near 85% isentropic efficiency, so it goes deeper into the phase envelope and uses its re-compressor to reach the outlet pressure. However, Twister has about 90% isentropic efficiency, so it goes the deepest into the phase envelope, then recompresses without rotating equipment to the outlet pressure. Twister is effectively a turboexpander/ separator/re-compressor all in one static piece of equipment. Thus, from a theoretical point of view, Twister has the most favorable thermodynamics. The challenge is to translate this theoretical advantage into the operations of actual gas plants.