Optimization of operation scheme with combined BOG treatment process in LNG terminals

Abstract

Two BOG treatment processes are adopted in the Tangshan LNG terminal of PetroChina, including the recondensation and highpressure compression based export processes. However, the LNG cold energy could not be fully used if only the high-pressure compression method is used for BOG treatment in the low export condition. The booster compressor has high operation power and large energy consumption.For this reason, the combined BOG treatment scheme of the Tangshan LNG terminal was studied through the combined numerical simulation and theoretical research with the ASPEN HYSYS software. Meanwhile, the combined operation scheme of the re-condenser and booster compressor was formulated to make full use of the LNG cold energy and reduce the operating power consumption of the booster compressor. The results show that the BOG flow has a great impact on the downstream LNG temperature. To control the downstream LNG temperature change of the re-condenser, the BOG flow should be controlled at first, with the auxiliary of BOG temperature and LNG header flow control. The combined operation scheme after optimization could reduce the power consumption of the compressor by 5%-20%, so that about 9.4×105 kW·h power can be saved annually, with an obvious optimization effect. Generally, the research results could provide a theoretical reference for the calculation of the combined BOG treatment process in the LNG terminal and the formulation of the operation scheme.

Keywords

• lng terminal
• combined bog treatment process
• re-condensation
• high-pressure compression based export
• operation power consumption