Method and apparatus for liquefying a hydrocarbon stream

A method of controlling the liquefaction of a hydrocarbon feed stream comprising at least the steps of:

• (i) liquefying the hydrocarbon feed stream according to a method at least comprising the steps of:
• (a) providing a hydrocarbon feed stream;
• (b) passing the hydrocarbon feed stream through an NGL recovery system to separate the hydrocarbon feed stream into at least a methane-enriched overhead stream and a C2+ enriched bottom stream;
• (c) passing the methane-enriched overhead stream through at least a first compressor to provide a methane-compressed stream;
• (d) liquefying the methane-compressed stream to provide a first liquefied stream;
• (e) reducing the pressure of the first liquefied stream to provide a mixed-phase stream;
• (f) passing the mixed-phase stream through an end gas/liquid separator to provide an end gaseous stream and a liquefied hydrocarbon product stream;
• (g) passing the end gaseous stream through one or more end-compressors to provide an end-compressed stream;
• and
• (h) feeding at least a recycle fraction of the end-compressed stream into the methane-enriched overhead stream;
• (ii) adjusting the temperature (Tx) of the first liquefied stream to change the amount of the end gaseous stream from the end gas/liquid separator;
• and
• (iii) controlling the amount of the recycle fraction of the end-compressed stream being fed into the methane-enriched overhead stream.

A method of maximizing the production of a liquefied hydrocarbon stream, comprising at least the steps of:

• (a) providing a liquefaction system comprising at least an NGL recovery system, a main refrigerant circuit and a first refrigerant circuit and an end gas/liquid separator to separate an end gaseous stream from a mixed-phase stream and an end compressor to provide an end-compressed stream, the main refrigerant circuit comprising at least one or more main refrigerant compressors, and the first refrigerant circuit comprising one or more first refrigerant compressors;
• (b) passing a hydrocarbon feed stream through the NGL recovery system to produce a methane-enriched overhead stream from the hydrocarbon feed stream;
• (c) controlling the liquefaction of the methane-enriched overhead stream in the liquefaction system, by adjusting the temperature (Tx) of the first liquefied stream to change the amount of the end gaseous stream from the end gas/liquid separator;
• and
• (d) controlling the amount of a recycle fraction of the end-compressed stream being fed into the methane-enriched overhead stream;
• (e) driving each of the one or more main refrigerant compressors and the one or more first refrigerant compressors at their maximum load.

Apparatus for liquefying a hydrocarbon stream, the apparatus at least comprising:

• (a) an NGL recovery system to extract a C2+ stream from a hydrocarbon feed stream to provide at least a methane-enriched overhead stream and a C2+ enriched bottom stream;
• (b) at least a first compressor to provide a methane-compressed stream from the methane-enriched overhead stream;
• (c) a main cooling stage to liquefy the methane-compressed stream to provide a first liquefied stream;
• (d) a pressure reducing device to reduce the pressure of the first liquefied stream to provide a mixed-phase stream;
• (e) an end gas/liquid separator to separate the mixed-phase stream into an end gaseous stream and a liquefied hydrocarbon product stream;
• (f) one or more end-compressors to compress the end gaseous stream to provide an end-compressed stream;
• and
• (g) a recycle fraction line connecting the end-compressed stream with the methane-enriched overhead stream to feed at least a recycle fraction of the end-compressed overhead stream into the methane-enriched overhead stream.