How it works
The Twister® Supersonic Separator has thermodynamics similar to a turbo-expander, combining the following process steps in a compact, tubular device:
- cyclonic gas/liquid separation
Whereas a turbo-expander transforms pressure to shaft power, Twister achieves a similar temperature drop by transforming pressure to kinetic energy (i.e. supersonic velocity):
- Multiple inlet guide vanes generate a high vorticity, concentric swirl (up to 500,000g)
- A Laval nozzle is used to expand the saturated feed gas to supersonic velocity, which results in a low temperature and pressure.
- This results in the formation of a mist of water and hydrocarbon condensation droplets.
- The high vorticity swirl centrifuges the droplets to the wall.
- The liquids are split from the gas using a cyclonic separator.
- The separated streams are slowed down in separate diffusers, typically recovering 70 – 75% of the initial pressure.
- The liquid stream contains slip-gas, which will be removed in a compact liquid de-gassing vessel and recombined with the dry gas stream.
Figure 1 shows a cross-section of a Twister tube with typical process conditions.
Figure 2 compares the thermodynamics of Twister with conventional Joule-Thomson expansion. In this example, the same feed conditions (100 bar/1450 psi, 40°C/104°F) and the same pressure drop (30%) has been assumed for both processes.