Two Step Nitrogen and Methane Separation Process

Abstract

A system and method for removing nitrogen and producing a high pressure methane product stream from natural gas feed streams is disclosed. A system for also producing natural gas liquids in conjunction with nitrogen removal from natural gas feed streams is also disclosed. The system and method of the invention are particularly suitable for use with feed streams in excess of 50 MMSCFD and up to 750 MMSCFD and containing up to 75 ppm carbon dioxide. Typical power requirements for compressing the methane product stream to produce a suitably high pressure stream for sale are reduced according to the system and method of the invention.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a system and method for separating nitrogen from methane and other components from natural gas streams. The invention also relates to a system and method for integrating natural gas liquids (NGL) extraction with nitrogen removal. The system and method of the invention are particularly suitable for use in recovering and processing feed streams typically in excess of 50 MMSCFD.[0003]2. Description of Related Art[0004]Nitrogen contamination is a frequently encountered problem in the production of natural gas from underground reservoirs. The nitrogen may be naturally occurring or may have been injected into the reservoir as part of an enhanced recovery operation. Transporting pipelines typically do not accept natural gas containing more than 4 mole percent inerts, such as nitrogen. As a result, the natural gas feed stream is generally processed to remove such inerts for sale and transportation of t...

AI Technical Summary

Benefits of technology

"The system and method described in this patent allow for the efficient removal of nitrogen from methane in a two-step process. It is particularly suitable for high flow rates of NRU feed gas and can handle concentrations of carbon dioxide up to 75 ppm. The process involves two fractionating columns, with the first column removing methane and heavier hydrocarbon components from nitrogen, and the second column removing nitrogen from the remaining methane. The overhead stream from the first column feeds the second column. The system and method achieve higher efficiency and reduced compression requirements compared to traditional NRU processes. Additionally, the patent describes the integration of NGL extraction into the two-step process. The system and method have advantages such as higher flow rate processing, reduced compression requirements, and efficient production of a processed natural gas stream and valuable NGL stream."

Problems solved by technology

In traditional nitrogen separation systems, the separation of NGL components is more difficult in streams containing more than 5% nitrogen because nitrogen has a stripping effect, absorbing ethane and heavier components.

Although the present system and method has the disadvantage of higher capital costs associated with additional equipment, compared to prior single column NRU processes, the costs of such are sufficiently offset by the savings in operating expenses, such as those from the reduced compression requirements, and the ability to efficiently produce a suitable processed natural gas stream and valuable NGL stream.

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