Abstract: The present invention relates to a method of controlling the production of a liquefied natural gas product stream (31) obtained by removing heat from natural gas by indirect heat exchange with an expanded heavy mixed refrigerant and an expanded light mixed refrigerant. The method comprises executing a control loop comprising maintaining the flow rate of the liquefied natural gas product stream (31) at a dependent set point and maintaining the flow rates of the heavy mixed refrigerant (60a) and the light mixed refrigerant (65) at operator manipulated set points (80, 81). The method further comprises executing an override control loop comprising: determining an override set point (95?) for the flow rate of the liquefied natural gas and computing an override set point (80?) for the flow rate of the heavy mixed refrigerant and an override set point (81?) to reduce residual available power of the electric motor.

Abstract: The present invention relates to a method of controlling the production of a liquefied natural gas product stream (31) obtained by removing heat from natural gas by indirect heat exchange with an expanded heavy mixed refrigerant and an expanded light mixed refrigerant. The method comprises executing a control loop comprising maintaining the flow rate of the liquefied natural gas product stream (31) at a dependent set point and maintaining the flow rates of the heavy mixed refrigerant (60a) and the light mixed refrigerant (65) at operator manipulated set points (80, 81). The method further comprises executing an override control loop comprising: determining an override set point (95?) for the flow rate of the liquefied natural gas and computing an override set point (80?) for the flow rate of the heavy mixed refrigerant and an override set point (81?) to reduce residual available power of the electric motor.

Abstract: A partially condensed hydrocarbon feed stream is sent to a column. An overhead vapour hydrocarbon stream from the column is then partially condensed by indirect heat exchanging against an expanded cooling fluid flowing through a first section of a cold side heat exchanging channel. The cooling fluid consists of a mixed refrigerant composition, and liquid from the expanded cooling fluid is continuously transformed to vapour thereby forming a residual liquid portion of not evaporated expanded cooling fluid. The residual liquid is used to progressively condense the hydrocarbon feed stream to produce the partially condensed hydrocarbon feed stream that is sent to the column, by allowing the hydrocarbon feed stream to lose heat to the residual liquid passing through a second section of the cold side heat exchanging channel. The liquid component that is condensed out of the overhead vapour hydrocarbon stream is used as reflux for the column.