Supersonic separation in onshore natural gas dew point plant

Conditioning of natural gas (NG) for sales mainly involves meeting water- and hydrocarbon-dew points (WDP and HCDP, respectively) while assuring high heating value (HHV) specifications achievable through minimal extraction of C5+ components (NGL). This paper compares technically and economically a supersonic separator technology – Twister®, which can promote simultaneously WDP, HCDP and enhanced NGL extraction – to a conventional gas treating technology, consisting of an onshore natural gas dew pointing plant with TEG Dehydration unit coupled to a Joule-Thomson/Low Temperature Separation unit (TEG + JT/LTS). In Twister® technology, water and hydrocarbon dew pointing normally requires pressure drop, which results in more NGL recovery than necessary to meet the established product specifications. An economic scenario was evaluated with NG and crude oil prices of US$ 4.22/GJ and US$ 50/bbl, respectively. The economic performance of each process alternative is evaluated in terms of the net present value (NPV) after 20 years of operation, with an assumed discounted rate of 10%. Twister® based process outperformed conventional TEG + JT/LTS process as the additional revenue from the increased NGL production compensates for the lower revenue from the NG sale resulting from decreased flow rate and lower NG HHV.