Application of Hybrid Coolers for Base Load LNG Liquefaction Plants

Abstract

Hybrid coolers are heat exchangers that use evaporative cooling to remove process heat. They have been used in other industries for more than 50 years and can serve as desuperheaters and condensers for the refrigeration propane loop or as the depropanizer overhead condenser units. The chief advantage of the Hybrid cooler compared to the DAC is its lower heat sink temperature for process heat removal. A Hybrid cooler cools the process fluid to a temperature that approaches the lower wet bulb temperature as opposed to the higher ambient dry bulb temperature for the DAC. Furthermore, the HYBD could have a lower temperature at approach comparing with the DAC. A lower propane condenser outlet temperature translates into lower propane compressor discharge pressure and lower overall compressor horsepower. Eventually there is more LNG production revenue when the compressor power savings from lower discharge pressure requirements are used to increase the feed rate to produce more LNG products. Based on $3.5/MMBtu of LNG and $1.50 /MMBTU of feed gas, in a twenty-year lifecycle, the estimated additional LNG revenue for a 4 train 5 MTPA LNG plant can range between $535.2 and $4,184.8 million dollars depending on site location.