Current hydrogen liquefiers’ energy consumption is between (11.9 and 15.0) kWh/kgLH2, and liquefaction cost is between (2.5 and 3.0) US$/kgLH2. In comparison, liquefied natural gas’s (LNG) energy consumption is » 0.33 kWh/KgLNG and cost < 0.3 US$/kgLNG. The high-power consumption and cost are partly due to using a low molecular weight refrigerant (H2), which requires multiple stages of compression. As a result, the use of mixed refrigerants (MRs) has been proposed for more efficient liquefaction cycles to be explored to lower the power and number of stages required for compression and thus reduce the total OPEX and CAPEX. However, the experimental data situation for MRs (especially for ternary and higher order mixtures) at temperatures below 100 K and, consequently, the accuracy of existing models is poor. Thus, the lack of reliable data and models for MRs thermophysical properties (such as density, heat capacity, speed of sound, enthalpy, and phase equilibrium) will obscure attempts to identify the most efficient liquefaction cycle. Moreover, the limitations and uncertainty of existing fluid property models implemented in process simulation tools, such as Aspen HYSYS, will increase design and operational margins.
This project will explore various liquefaction processes based on Brayton cycles, employing new mixed refrigerants mixtures of (hydrogen + helium + neon + nitrogen), through the following main outcomes:
A basic simulation in Aspen HYSYS for a selected MRs liquefaction cycle, with a particular focus on the impact and sensitivity of various properties on the overall performance of the liquefaction process. This sensitivity analysis will be used to design the final experimental plan.
An assessment of the available thermophysical property data for mixed refrigerant mixtures and the performance of existing models. This will include identifying strategic gaps and providing a detailed plan for future experimental measurements to generate the required reference data.
An experimental campaign to measure the vapor-liquid and solid-liquid equilibria and speed of sound of (hydrogen + helium + neon + nitrogen) mixtures at temperature conditions between (100 and 15) K, pressures up to 10 MPa, and various compositions, with neon content higher than 10%. The speed of sound data will be used to derive other thermodynamic properties such as density, heat capacity, and compressibility.
Partners: The University of Western Australia, INPEX, Woodside
Researchers: Dr Saif Al Ghafri, Associate Professor Paul Stanwix
Duration: 3 years