Method to optimize thermodynamic expansion in gas liquefaction processes

摘要

For gas liquefaction processes, thermodynamic expansion is optimized by use of a hydraulic turbine expander for liquefied gases which can be adjusted to different flow rates and differential pressures by varying the rotational speed and/or guide vane position. The turbine expander is disposed in-line between an upstream system for gas liquefaction and a downstream system for liquefied gas handling including a terminal vessel for storage or phase separation. The invention further includes a device to measure the terminal pressure at an inlet pipe of and/or inside the terminal vessel, and a device to control the turbine expander in response to pressure measurements. The turbine controller sets the rotational speed and/or the guide vane position of the expander depending on changes in the terminal pressure such that the pressure inside the terminal vessel remains constant at a certain target value for different thermodynamic, hydraulic or chemical conditions of the gas liquefaction process. In the preferred embodiment the terminal pressure measuring device provides corresponding electronic, optical or mechanical signals to the turbine controller which determines the rotational speed and/or guide vane position in such a way that the pressure drop across the turbine expander and the downstream system continuously meet the target value of the terminal pressure.