How it works

The Twister® Supersonic Separator has thermodynamics similar to a turbo-expander, combining the following process steps in a compact, tubular device:

• expansion
• cyclonic gas/liquid separation
• re-compression

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.