Challenges in starting up natural gas compression units
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For the re-liquefaction of LNG BOG, before starting the compressor it is necessary to take into account that the temperature of this LNG BOG is around minus 160 degrees Celsius, a temperature that the compressor cannot handle. So how can the compressor be started? First, ways need to be found to heat the BOG entering the cold box; under normal operation, the BOG that enters the cold box is heated by the BOG that returns to the cold box after passing through the compressor. But what to do if there is no BOG back-cooler while driving? One solution is to use nitrogen to start the compressor; the nitrogen that has been compressed by the compressor flows into the cooling tank. Then, the BOG from liquefied natural gas is introduced into this cooling tank, where it is heated to reach the appropriate temperature for entry into the compressor. After that, the normal procedures for starting the compressor can be followed!
Air heating seems to work too, right?~~~~~
Firstly, the temperature of the BOG entering the compressor at the beginning is generally at room temperature; it isn’t that low. It is only after prolonged operation that the temperature of the BOG decreases, but it’s highly unlikely for it to reach -160 degrees. If it did drop that low, the compressor would shut down. Secondly, if the temperature is often that low, then it should be designed with an air vaporizer at the inlet.
Is it possible to heat it first with nitrogen? Excessive nitrogen in natural gas can cause the pressure in LNG storage tanks to rise; in more severe cases, it can even lead to the LNG inside the tanks rolling around. Why can’t the cooling capacity of BOG be recovered before it is fed into the BOG compressor in the process?
With our compressors, there is no need to heat the intake air; Bengbu Zhidada welcomes you