System and method for operating a liquefaction train
AssigneeShell Oil Company
InventorsJeroen VAN DE RIJT, Pierre Christian Marie CARRETTE, Hossein KHAJAVI
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Abstract
A method for operating a main cryogenic heat exchanger for use in a natural gas liquefaction process, involves monitoring or predicting variations in the flow rate of a feed gas stream provided to the main cryogenic heat exchanger. When a variation of the flow rate exceeding a predetermined threshold value is monitored or predicted, a control scheme is started to control one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of a compressed mixed refrigerant stream in a refrigerant loop.
Claims12
A method of operating a main cryogenic heat exchanger for use in a natural gas liquefaction process, the method comprising
- receiving a feed gas stream at an inlet of the main cryogenic heat exchanger at a flow rate,
- cycling a mixed refrigerant through a refrigerant loop, the refrigerant loop comprising at least a refrigerant compressor unit comprising a suction side and a discharge side, wherein cycling comprises discharging a compressed mixed refrigerant stream from the discharge side and passing the mixed refrigerant through the main cryogenic heat exchanger to allow the mixed refrigerant to exchange heat with the feed gas stream in the main cryogenic heat exchanger and thereby cool the feed gas stream,
- wherein the method further comprises
- monitoring or predicting variations in the flow rate of the feed gas stream and
- in case a variation of the flow rate exceeding a predetermined threshold value is monitored or predicted, starting a control scheme which control scheme comprises
- controlling one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of the compressed mixed refrigerant stream.
The system for use in a natural gas liquefaction process, the system comprising
- a main cryogenic heat exchanger for receiving a feed gas stream at an inlet of the main cryogenic heat exchanger at a flow rate,
- a refrigerant loop comprising at least a refrigerant compressor unit comprising a suction side and a discharge side, wherein the refrigerant loop is arranged to cycle a mixed refrigerant through the refrigerant loop, wherein cycling comprises discharging a compressed mixed refrigerant stream and passing the mixed refrigerant through the main cryogenic heat exchanger to allow the mixed refrigerant to exchange heat with the feed gas stream in the main cryogenic heat exchanger and thereby cool the feed gas stream, the refrigerant loop further comprising one or more compressor recycle valves and associated recycle lines arranged to recycle part of the compressed mixed refrigerant stream,
- wherein the system further comprises a controller arranged to
- monitor or predict variations in the flow rate of the feed gas stream,
- determine a monitored or predicted variation of the flow rate exceeding a predetermined threshold value and in response thereto
- start a control scheme which control scheme which control scheme comprises controlling the one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of the compressed mixed refrigerant stream.
Dependencies are inferred from the claim text.