Supersonic Separation of Natural Gas Liquids by Twister Technology

Abstract

The Twister supersonic separator is a unique combination of known physical processes, combining aero- dynamics, thermodynamics and fluid dynamics to produce an innovative gas conditioning process. Condensation and separation at supersonic velocity is the key for achieving a significant reduction in both capital and operating cost. Twister is a proven gas conditioning technology. Condensation and separation at supersonic velocity provides several unique benefits as the short residence time within the Twister tube prevents hydrate problems, thereby eliminating the use of chemicals and associated regeneration systems. A Twister tube designed for 1 MMSm3/d (35 MMSCFD) at 100 bar is approximately 2 m long. The simplicity and reliability of this static device with no rotating parts, operating without chemicals, ensures a simple, environmentally friendly facility, with a high availability, suitable for de-manned operation. Twister can achieve both water and hydrocarbon dew pointing in one unit. The supersonic separation equipment has thermodynamics similar to a turbo expander, combining cyclone gas/liquid separation and re-compression in a compact, tubular device.Processing of natural gas is the largest industrial gas separation application. The U.S consumption of natural gas is higher than 623 billion SCM/y and total worldwide consumption surpasses 2.69 trillion SCM/y. This consumption drives a worldwide market for new natural gas separation equipment of more than $5 billion per year. Natural gas contains many contaminants, water being the most common undesirable component. Most natural gases will be nearly water-saturated at the temperature and pressure of production. Dehydration of natural gas is hence a critical step of the natural gas conditioning process as it reduces the potential for corrosion, hydrate formation and freezing in the pipeline. A conventional method for dehydration in the natural gas industry is the use of a liquid desiccant contactor-regeneration process by TEG. However, there are several operating problems with glycol dehydrators. Suspended foreign matters may contaminate glycol solutions and overheating of the solutions may produce decomposition products. Foaming of solution may also occur with resultant carry-over of liquid. Besides water contamination, natural gas contains liquids that should be commonly removed to meet hydrocarbon dew point specification. An undesirable result of extracting NGL is a lower heating value of the gas product which can reduce its market value. In this paper, Twister supersonic technology is evaluated and compared to conventional Joule-Thompson valve and Turbo- expander.