One-time start-up scheme of the refrigerant compressor in LNG plant

Multiple start-up of refrigerant compressor in LNG plant can lead to the dual problem of material loss and environmental pollution, so it is in urgent need to optimize the start-up of refrigerant compressor. In this paper, the Kunlun Energy Huanggang LNG Plant was selected as the example. After refrigerant is filled in the ethylene refrigeration cycle system, the compressor shall be started immediately before the pressure rises to the design value, or the pressure will be too high, leading to the failure of compressor start-up due to excessive start-up load. And after each failure, the compressor shall not be started again until the pressure is released to 0.6 MPa. Based on multiple start-up data of the ethylene compressor in the Kunlun Energy Huanggang LNG Plant from 2015 to 2017, mathematical modeling was conducted by means of analytic hierarchy process. And by virtue of comparison and selection, the compressor one-time start-up scheme was proposed as follows. When the compressor is in the period of low-speed rotation (2 200 r/min), turn on the blowdown valve to cool the machine sufficiently, and then raise the speed. In the process of speed rising, when the inlet temperature is lower than －40 ℃, the pressure is lower than the dew-point pressure corresponding to the current temperature and the opening of the surging valve is regulated to the electric current of compressor less than 1 200 A, the machine suffers no vibration and interlock overload, and thus the one-time start-up succeeds. This solution solves the multiple start-up of compressor and provides the reference for the scientific operation start of other LNG plants.