Compressor train start-up using variable inlet guide vanes

A gas compressor train comprising:

• a centrifugal compressor comprised of a compressor inlet, a compressor outlet, a plurality of compressor stages including two intermediate compressor stages, sequentially arranged between the compressor inlet and the compressor outlet, and at least a first set of variable inlet guide vanes at an inlet of a first one of the compressor stages;
• a driver machine drivingly coupled to the centrifugal compressor;
• a controller configured to control the opening and closing of the set of variable inlet guide vanes, wherein prior to start-up and acceleration of the centrifugal compressor, the controller is configured to at least partly close the first set of variable inlet guide vanes, and during the start-up and acceleration of the centrifugal compressor, with the first set of variable inlet guide vanes at least partly closed, the controller is further configured to open the first set of variable inlet guide vanes to increase gas flow through the centrifugal compressor once a predetermined minimum operating speed has been achieved;
• a bleeding line to bleed a portion of the gas flowing from a delivery side of one of the compressor stages and return the bled gas to an inlet of another of the compressor stages upstream of the delivery side when starting rotation of the centrifugal compressor and accelerating the centrifugal compressor up to the predetermined minimum operating speed;
• and
• a first side stream, a second side steam and a third side stream,
• wherein the plurality of compressor stages of the centrifugal compressor comprises a first set of compressor stages including the two intermediate compressor stages, and a second set of compressor stages, the first set of compressor stages arranged in a back-to-back configuration relative to the second set of compressor stages, and
• wherein the first side stream and the second side stream are fluidly coupled to a respective one of the two intermediate compressor stages in the first set of compressor stages, and the third side steam is fluidly coupled to a compressor stage of the second set of compressor stages, said compressor stage of the second set of compressor stages being the most upstream compressor stage in the second set of compressor stages, the third side stream configured to merge with a partly compressed process fluid from an outlet of the first set of compressor stages to form a merged stream, the merged stream fluidly coupled to an inlet of the second set of compressor stages.