Analysis of freezing risk during LNG evaporation process

Abstract

Liquid natural gas (LNG) boiling process concerns majority of LNG applications because of a need of its regasification. Depending on pressure an equilibrium temperature of LNG is 112-160K. The low boiling temperature of LNG makes the vaporisation process complicated. An important risk of the regasification is related to a possibility of a solid phase formation (freezing of a heating fluid). For a range of important applications the heating fluid is water or water-glycol mixture, characterized by freezing temperature considerably higher than the boiling temperature of LNG. The solid phase formation can lead to an increase of hydraulic pressures losses, deterioration of the heat transfer or even to the destruction of a heat exchanger and any accompanying device. It motivates a need for better understanding and control of a heat transfer related to the regasification to avoid the solid phase formation. The current work analyses a LNG regasification and a risk of solidification in a generalized shell and tube heat exchanger. The conducted study helped to define a critical Reynolds number below which the solidified ice totally blocks the flow.