Thermodynamic Properties of Liquefied Natural Gases M. Thol, R. Lentner, C. Tietz, R. Kleinrahm, R. Span, M. Richter Research on LNG Properties at RUB Measurements on Liquefied Natural Gases (LNG) Multicomponent mixtures Binary mixtures Equations of State Enhanced revised Klosek-McKinley equation (eRKM) Binary mixtures Fundamental equation of state in terms of the Helmholtz energy Multicomponent mixtures 2 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Accurate Density Measurements on LNG Multicomponent mixtures 3 mixtures including 3 mixtures including methane, ethane, propane, butane, nitrogen (Set I) methane, ethane, propane, butane, isobutane, pentane, isopentane, nitrogen (Set II) Binary mixtures (Set III) Methane + propane Methane + isobutane Methane + pentane Methane + nitrogen 3 (xC1 = 0.88) (xC1 = 0.97) Identify binary mixtures, which have to be measured to improve a fundamental equation of state (xC1 = 0.99) (xC1 = 0.70, xC1 = 0.97, xC1 = 0.99) Thol et al. | LNG Metrology Workshop 2017, Noordwijk Binary systems with high methane content Equations of State Revised Klosek-McKinley EOS1 Enhanced Revised Klosek-McKinley EOS2 Range of validity Saturated liquid density ρ‘(T) 100 K ≤ T ≤ 115 K at ps Uncertainty Range of validity Δρ/ρ = 0.1% Saturated liquid density ρ‘(T) Homogeneous liquid density ρ(T,p) 100 K ≤ T ≤ 135 K for ps ≤ p ≤ 10 MPa Uncertainty Δρ/ρ = 0.1%, for 100 K ≤ T ≤ 115 K Δρ/ρ = 0.15%, for 115 K < T ≤ 135 K International standard, GIIGNL handbook 1R.D. 2C. International standard, GIIGNL handbook McCarty, Mathematical Models for the Prediction of Liquefied-Natural-Gas Densities, J. Chem. Thermodyn. 14: 837-854 (1982) Tietz, M. Richter, R. Kleinrahm, R. Span, Enhancement of the Revised Klosek and McKinley Method for Density Calculations of Liquefied Natural Gas (LNG) over the Temperature Range from (100 to 135) K at Pressures up to 10 MPa, Fuel Process. Technol. (2016) 4 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Fundamental Equation of State (EOS-LNG) Helmholtz energy for mixtures Ideal gas contribution Reducing parameters correspond to critical parameters of pure fluids Residual fluid contribution Reducing parameters as functions of composition Pure fluid contribution at Departure term corresponding states 5 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Fundamental Equation of State (EOS-LNG) Reducing parameters Departure term Combination of polynomial, exponential and special exponential terms 6 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Adjustable parameters: coefficients, temperature and density exponents, exponential parameters, number of terms Fundamental Equation of State (EOS-LNG) C1C3 No adjustment needed C1C4i New binary specific functions required Deviations calculated with: C1N2 C1C5 7 Thol et al. | LNG Metrology Workshop 2017, Noordwijk GERG-2008 Fundamental Equation of State (EOS-LNG) C1C4i C1C4i C1C5 C1C5 8 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Deviations calculated with: GERG-2008 EOS-LNG Fundamental Equation of State (EOS-LNG) Adjustment of binary specific function for C1C4 Libya Methane Ethane Propane n-Butane Nitrogen 9 81.56 mol-% 13.37 mol-% 3.68 mol-% 0.69 mol-% 0.70 mol-% Oman Methane Ethane Propane n-Butane Nitrogen Thol et al. | LNG Metrology Workshop 2017, Noordwijk 87.89 mol-% 7.27 mol-% 2.93 mol-% 1.56 mol-% 0.35 mol-% Norway Methane Ethane Propane n-Butane Nitrogen 91.80 mol-% 5.70 mol-% 1.30 mol-% 0.40 mol-% 0.81 mol-% Fundamental Equation of State (EOS-LNG) 10 LNG2 LNG5 LNG7 Methane 84.64 mol-% Ethane 12.80 mol-% Propane 1.50 mol-% n-Butane 0.21 mol-% i-Butane 0.22 mol-% Pentane 0.03 mol-% i-Pentane 0.02 mol-% Nitrogen 0.59 mol-% Methane 87.97 mol-% Ethane 7.24 mol-% Propane 2.90 mol-% n-Butane 0.69 mol-% i-Butane 0.64 mol-% Pentane 0.10 mol-% i-Pentane 0.11 mol-% Nitrogen 0.34 mol-% Methane 97.89 mol-% Ethane 1.00 mol-% Propane 0.50 mol-% n-Butane 0.21 mol-% i-Butane 0.18 mol-% Pentane 0.02 mol-% i-Pentane 0.02 mol-% Nitrogen 0.19 mol-% Thol et al. | LNG Metrology Workshop 2017, Noordwijk Adjustment of binary specific functions for: C1C4 C1C4i C1C5 C1C5i Methane + Nitrogen Libya LNG2 Norway Deviations calculated with: GERG-2008 Modified GERG-2008: C1N2 with Lorentz-Berthelot mixing rule Possible reason maybe many-body interaction in multicomponent system??? 11 Thol et al. | LNG Metrology Workshop 2017, Noordwijk xC1 / mol-% xN2 / mol-% Libya 81.56 0.6953 LNG2 84.64 0.5854 Norway 91.80 0.8050 Liquid-Liquid Equilibria In the literature, only methane + hexane and L C1C5: xC1 = 0.5 VLE LLE higher-order hydrocarbons are known to exhibit liquid-liquid equilibria Liquid-liquid equilibria can be found even for “simple” mixtures such as methane + pentanes or butanes V Liquid-liquid equilibria have to be considered L LLE C1C5i: xC1 = 0.5 VLE V 12 Thol et al. | LNG Metrology Workshop 2017, Noordwijk not only for modeling but also during measurements: unreasonable movement of sinker was detected when measuring methane + n-pentane Summary Based on investigations of multicomponent LNG mixtures, binary systems with high methane content were comprehensively studied: New liquid density measurements of C1C3, C1C4i, C1C5 and C1N2 New binary specific functions for C1C4, C1C4i, C1C5 and C1C5i Representation of multicomponent systems was significantly improved: 5 of 6 systems: Δρ/ρ < 0.05% Maximum deviation of LNG2: Δρ/ρ = 0.061% Liquid-liquid equilibria were found for C1C4, C1C4i, C1C5, C1C5i 13 Thol et al. | LNG Metrology Workshop 2017, Noordwijk Outlook The current EOS-LNG has to be evaluated for the representation of other thermodynamic data than density Experimental investigation of additional binary mixtures, e.g. C1C4 or C1C5i filling system of single-sinker densimeter needs to be modified Additional thermodynamic properties have to be measured, in particular speed of sound and vapor-liquid equilibrium Liquid-liquid equilibria have to be considered, even for “simple” systems such as C1C4, C1C4i, C1C5, or C1C5i Fitting techniques have to be modified to allow for: 14 the simultaneous optimization of binary specific functions the application of measurements of multicomponent systems to the fit Thol et al. | LNG Metrology Workshop 2017, Noordwijk RESEARCH 15 Thol et al. | LNG Metrology Workshop 2017, Noordwijk

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