METHOD AND APPARATUS FOR REGULATORY CONTROL OF PRODUCTION AND TEMPERATURE IN A MIXED REFRIGERANT LIQUEFIED NATURAL GAS FACILITY

A CONTROL SYSTEM FOR A PROCESS OF LIQUEFIED NATURAL GAS PRODUCTION (LNG) FROM NATURAL GAS USING A HEAT EXCHANGER (210) AND A CLOSED LOOP REFRIGERANT CYCLE (226) EMPLOYS INDEPENDENT, DIRECT CONTROL OF BOTH PRODUCTION AND TEMPERATURE BY ADJUSTING REFRIGERATION TO MATCH A SET PRODUCTION. THE CONTROL SYSTEM SETS AND CONTROLS LNG PRODUCTION AT A REQUIRED PRODUCTION VALUE, AND INDEPENDENTLY CONTROLS LNG TEMPERATURE BY ADJUSTING THE REFRIGERATION PROVIDED TO THE NATURAL GAS STREAM. ONE EXEMPLARY METHOD EMPLOYS COMPRESSOR SPEED, FOR EXAMPLE, AS A KEY MANIPULATED VARIABLE (MY) TO ACHIEVE FAST AND STABLE LNG TEMPERATURE REGULATION. OTHER COMPRESSOR VARIABLES RATHER THAN SPEED MAY BE KEY MVS, DEPENDING ON THE TYPE OF MR COMPRESSORS EMPLOYED, AND MAY BE THE GUIDEVANE ANGLE IN A CENTRIFUGAL COMPRESSOR OR THE STATOR BLADE ANGLE IN AN AXIAL COMPRESSOR. THE SECOND EXEMPLARY METHOD EMPLOYS A RATIO OF TOTAL RECIRCULATING REFRIGERANT FLOW TO LNG FLOW AS THE KEY MANIPULATED VARIABLE TO EFFECTIVELY CONTROL THE LNG TEMPERATURE. (FIGURE 1)