Method and apparatus for cooling down a cryogenic heat exchanger and method of liquefying a hydrocarbon stream

A method of cooling down a cryogenic heat exchanger adapted to liquefy a hydrocarbon stream, the method comprising the steps of

• receiving, by the cryogenic heat exchanger, the hydrocarbon stream to be liquefied and a refrigerant, to exchange heat between the hydrocarbon stream and the refrigerant, thereby at least partially liquefying the hydrocarbon stream, and to discharge the at least partially liquefied hydrocarbon stream and a spent refrigerant that has passed through the cryogenic heat exchanger,
• recirculating, by a refrigerant recirculation circuit, the spent refrigerant back to the cryogenic heat exchanger, wherein the refrigerant recirculation circuit comprises at least a compressor, a compressor recycle valve, a cooler, and a first Joule Thomson (JT) valve;
• performing a comparison step by a programmable controller, said comparison step comprising:
• (i) receiving one or more refrigerant temperature indications, and providing an indication of a temperature of the refrigerant,
• (ii) comparing the one or more refrigerant temperature indications with one or more associated predetermined threshold values, and
• (iii) based on an outcome of the comparison under (ii) selecting one of an automated warm cooling down procedure of the cryogenic heat exchanger and an automated cold cooling down procedure of the cryogenic heat exchanger;
• wherein the automated cold cooling down procedure is adapted to reduce a temperature of the cryogenic heat exchanger from a cold condition down to LNG production point and is allowed to start with an opened first JT valve,
• wherein the automated warm cooling down procedure comprises an initial opening step, wherein the initial opening step comprises imposing an initial opening of the first JT valve, wherein the initial opening step of the first JT valve according to the automated warm cooling down procedure differs in size of the opened first JT valve according to the automated cold cooling down procedure;
• and
• performing a TROC step by the programmable controller, the TROC step comprising adjusting the opening of the first JT valve based on a determined temperature rate of change (TROC) of the refrigerant over the first JT valve in accordance with an adjustment scheme, wherein the automated warm cooling down procedure and the automated cold cooling down procedure comprise a plurality of different adjustment schemes.