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Nitrogen Rejection Units


Natural gas processing equipment requires a wide range of engineering and manufacturing capability. Nitrogen rejection units (NRUs) require a different technical approach than liquefied petroleum gas (LPG) or natural gas liquids recovery (NGL). Sep-Pro has built both.

According to the Gas Research Institute, nitrogen rejection from natural gas is necessary in about 17% of US gas reserves. Most pipeline standards require that natural gas contain less than 4% nitrogen. If there is too much nitrogen present in a pipeline, there is a danger of vaporlock or combustion. Nitrogen also dilutes the heating value of the gas, resulting in a lower BTU and decreased value. High-nitrogen natural gas is essentially stranded, as it cannot feasibly be transported through pipelines to market.

Nitrogen rejection is a difficult technical separation because of the similar molecular size of nitrogen (N2) and methane (CH4) and the lack of a selective reactivity such as there is with carbon dioxide or hydrogen sulfide in an amine plant.

Pressure swing adsorption, cryogenic separation, and lean oil absorption have been employed to remove nitrogen from natural gas. 

* Pressure swing adsorption (PSA) uses a zeolite adsorbent to selectively separate nitrogen from methane. The gas is then regenerated from the adsorbent with a combination of pressure and thermal changes. PSA is used for gas dehydration, carbon dioxide removal, nitrogen rejection, and hydrocarbon dew point control.

* Cryogenic separation employs low temperature thermodynamic separation based on the comparative boiling points of methane (-259¡ÆF) and nitrogen (-320¡ÆF) . As the mixture cools, methane will condense before nitrogen, allowing the two to be separated.

* Lean oil absorption absorbs the methane away from the nitrogen in a higher molecular weight hydrocarbon and then regenerates the absorbed methane either through staged pressure reductions or through thermally-driven distillation.

Sep-Pro leases or sells NRU equipment ranging from 300MSCFD to 5MMSCFD feed with nitrogen from 6-45% by volume. NRU can be used in conjunction with gas to liquids (GTL), liquefied petroleum gas (LPG), molecular sieves and cryogenic equipment. Sep-Pro has numerous stranded gas solutions.

Leasing is an option for almost all of Sep-Pro's natural gas processing equipment. NRU equipment leasing is attractive because it minimizes the producer's risk. Sep-Pro will solve your nitrogen rejection problem with the technical approach that is appropriate.

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