| 摘要 |
The present invention relates to a process of liquefying a gaseous, methane-rich feed to obtain a liquefied product by supplying the gaseous, methane-rich feed at elevated pressure to a first tube side of a main heat exchanger at its warm end, cooling, liquefying and sub-cooling the gaseous, methane-rich feed against evaporating refrigerant to get a liquefied stream, removing the liquefied stream from the main heat exchanger at its cold end and passing the liquefied stream to storage as liquefied product, removing evaporated refrigerant from the shell side of the main heat exchanger at its warm end, compressing in at least one refrigerant compressor the evaporated refrigerant to get high-pressure refrigerant, partly condensing the high-pressure refrigerant and separating the partly-condensed refrigerant into a liquid heavy refrigerant fraction and a gaseous light refrigerant fraction, sub-cooling the heavy refrigerant fraction in a second tube side of the main heat exchanger to get a sub-cooled heavy refrigerant stream, introducing the heavy refrigerant stream at reduced pressure into the shell side of the main heat exchanger at its mid-point, and allowing the heavy refrigerant stream to evaporate in the shell side, cooling, liquefying and sub-cooling at least part of the light refrigerant fraction in a third tube side of the main heat exchanger to get a sub-cooled light refrigerant stream, introducing the light refrigerant stream at reduced pressure into the shell side of the main heat exchanger at its cold end, allowing the light refrigerant stream to evaporate in the shell side, and controlling the liquefaction process using a process controller to determine simultaneously control actions for a set of manipulated variables in order to optimize at least one of a set of parameters while controlling at least one of a set of controlled variables. |
