Project description: GERG 2004
Evaporation and liquefaction are essential processes in the LNG process chain. High expectations regarding economic efficiency, product quality and environmental safety
lead to increasing demands on these processes. This applies to both the design and the operation of a specific system, e.g. to the optimal use of resources while vaporizing
LNG. Fundamental contributions to optimization and operation of a system are expected from the simulation of processes. Therefore, an accurate representation of thermophysical properties and energy balances of the simulated process is essential. Results of process simulations are highly influenced by the thermodynamic-property
model used. New highly accurate equations of state for natural gas and LNG represent an unused potential for accurate process modelling.
The GERG-2004 [1] is a wide-range equation of state, which is formulated for mixtures consisting of up to 18 specified components. It covers the gas and liquid phase
as well as the supercritical region and the vapor-liquid equilibrium with the highest accuracy possible. The formulation was adopted as the new reference equation of state
for natural gases and the development of a corresponding ISO standard is in process. However, so far the GERG-2004 is not used in commercial, LNG related simulation software.
In order to implement the GERG-2004 into various simulation tools, the software available for GERG-2004 has been adapted to the CAPE-OPEN standard.
Benefits achieved
The GERG-2004 was successfully integrated into common simulation tools as a
CAPE-OPEN Property Package and complex natural gas processes could be simulated. Compared to typical
engineering equations of state, significant differences were found for the calculation of thermodynamic properties, e.g., for saturated liquid densities or in the
two phase region. These differences result in significant changes for design data of modeled LNG vaporization or natural gas liquefaction processes.
[1] Kunz, O.; Klimeck, R.; Wagner, W.; Jaeschke. M. (2007): The GERG-2004 Wide-Range Reference Equation of State for Natural Gases and Other Mixtures.
GERG Technical Monograph 15. Fortschr.-Ber. VDI, Reihe 6, Nr. 557, VDI Verlag, Düsseldorf.
