Nitrogen content must be removed down to below 1 mol % based on the LNG specifications. Nitrogen will lower the liquefaction temperature, which will then increase the power consumption. Nitrogen is also an inert gas which do not support combustion. Hence, when a gas with high nitrogen content is burned, it will lead to unstable combustion. Nitrogen rejection unit (NRU) is used to remove nitrogen from residue gas to produce a treated gas which has minimum amount of nitrogen content. Petro Gasgen offers highly efficient nitrogen rejection units that can satisfy most industrial needs.

How It Works?

Nitrogen rejection methods can be classified into cryogenic and noncryogenic processes. Cryogenic process uses the boiling points difference between nitrogen and methane for separation process. Joule-Thomson effect is applied to cool of the high-pressure gas and separation in a distillation column to produce nitrogen overhead product and a methane-rich bottom. Noncryogenic process applies the pressure swing adsorption (PSA). Adsorbent for instance, zeolite is used in PSA to separate nitrogen from methane in a cyclic process. The methane adsorption process occurs at high pressure. Natural gas with low nitrogen content will be produced at low pressure which will require recompression to the pipeline pressure. The rejected nitrogen will need to recompress to the feed section because the hydrocarbon content in it is somewhat significant.