The raw natural gas has a low methane content and a high nitrogen content
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What impact does the low methane content and high nitrogen content in the raw natural gas have on the liquefaction process?
Low methane content and high nitrogen content reduce the calorific value of liquefied natural gas and increase processing costs. At the same time, nitrogen needs to be separated separately during the liquefaction process, which increases the complexity of the process and the equipment costs. .
Conduct economic comparisons between the option of not removing N2 and the option of removing N2, to ultimately determine whether it is feasible to remove N2. It is higher than conventional (non-) or low-N2 investment. Of course, N2 itself has certain value for recovery; methane and N2 can be considered as products
At atmospheric pressure, the boiling point of methane is -162°C, and that of nitrogen is -196°C. The higher the nitrogen content, the greater the power consumption per unit of liquefaction. Secondly, the liquefied natural gas is stored in low-temperature storage tanks. Due to the high nitrogen content in LNG, and since nitrogen evaporates more easily than methane, this causes stratification of the LNG within the tank, leading to mixing of the LNG inside it and significant fluctuations in tank pressure over short periods of time.
An increase in the BOG volume in the storage tank may lead to frequent venting. The temperature difference before and after the valve of cold box products is large, resulting in an increased operating power of the refrigerant compressor.