应用状态方程预测液化天然气的热物理性质

Use of equations of state in predicting thermophysical properties of LNG

状态方程是预测和关联流体热力学性质的主要工具。将Soave-Redlich-Kwong(SRK)、PengRobins on(PR)、Le e-Ke s le r-Plocke r(LKP)和Modifie d-Be ne dict-We bb-Rubin-Starling(MBWRS)四个适用于气相和液相的状态方程用于预测液化天然气(LNG)的密度、压缩因子、焓、熵和比热容等热物理性质。HYSYS软件预测结果表明,除了比热容之外,四个状态方程预测结果都比较精确。在液化天然气热物性计算中,当流体相超出MBWRS方程适用范围时(Tr≥0.3),MBWRS状态方程的预测结果与LKP、SRK、PR方程的计算结果相比,仍然较为精确,可以用于预测液化天然气热物理性质。

Equation of state （EOS） is the major tool for prediction and correlation of thermodynamic properties of fluid. Four EOSs are widely used for both liquid and gas phases, which are the equations of Soave-Redlich-Kwong （SRK） , Peng-Robinson （PR） , Lee-Kesler-Plocker （LKP） and Modified-Benedict-Webb-Rubin-Starling （MBWRS） , to predict LNG thermophysical properties such as density, compression factor, enthalpy, entropy and specific heat capacity. It turns out that the HYSYS prediction accuracies of the four EOSs are good for all thermophysical properties except specific heat capacity; In LNG thermophysical calculation, when the fluid phase exceeds the applicable range of MBWRS equation （ Tt ≥ 0.3）, the result got from MBWRS equation is still accurate compared with the results got from LKP, SRK and PR equations, so MBWRS equation can be used to predict the thermophysical properties of liquefied natural gas.