Integrated NGL and Nitrogen Separation Without Recompression
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Solution Overview
Problem
Existing natural gas processing systems face challenges in efficiently removing nitrogen and recovering Natural Gas Liquids (NGLs) while minimizing capital and operating costs, particularly when dealing with wide ranges of inlet nitrogen concentrations and gas volumes.
Innovation Solution
The integration of heat transfer and process streams between NGL and nitrogen removal sections eliminates the need for recompression, utilizing a High Pressure Rectifier and expander/compressor unit to maintain sufficient pressure for nitrogen removal without additional compression, and employs strategic cooling and heat exchange to enhance NGL recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a nitrogen rejection unit is installed downstream of NGL removal, then nitrogen removal capability is improved, but capital cost and operating cost increase significantly
Solution Approach 1:
The first fractionation column is designed to serve dual functions: it removes NGL components while also providing preliminary separation that reduces the nitrogen load on the second column. This multi-functionality reduces the size and cost requirements for dedicated nitrogen removal equipment
Solution Approach 2:
The system merges the NGL removal and nitrogen removal processes into an integrated two-column fractionation system rather than using separate standalone units. The columns share common infrastructure including heat exchangers, reflux systems, and control mechanisms, reducing overall equipment count and capital cost
2Productivity
If recompression is applied between NGL removal and nitrogen removal steps, then nitrogen removal efficiency is improved, but operating cost and energy consumption increase
Solution Approach 1:
The system performs preliminary nitrogen removal in the first fractionation column at reduced pressure before the expensive recompression step. This preliminary action reduces the nitrogen content of the gas stream entering the recompression stage, making the subsequent high-pressure nitrogen removal more energy-efficient
Solution Approach 2:
The system dynamically adjusts operating parameters including column pressures, reflux ratios, and feed rates to optimize the balance between NGL removal and nitrogen removal. This dynamic operation allows the system to achieve high nitrogen removal efficiency while minimizing compression energy requirements through optimal process conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces equipment count and costs by approximately one-third, achieving over 90% ethane recovery and 99% purity in the nitrogen stream, with a processed sales gas containing less than 4% nitrogen, thereby optimizing NGL extraction and nitrogen removal efficiency.
Implementation Method 1
utilizing expander technology to reduce the inlet pressure from approximately 800 psig down to a pressure level of near 300 psig
Implementation Method 2
Heat Exchanger
Implementation Method 3
two cryogenic fractionating columns
Implementation Method 4
two cryogenic fractionating columns
Data Source
AI summary
A system and method for removing nitrogen and producing a high pressure methane product stream and an NGL product stream from natural gas feed streams where at least 90%, and preferably at least 95%, of the ethane in the feed stream is recovered in the NGL product stream. The system and method of the invention are particularly suitable for use with feed streams in excess of 5 MMSCFD and up to 300 MMSCFD and containing around 5% to 80% nitrogen. The system and method preferably combine use of strategic heat exchange between various process streams with a high pressure rectifier tower and the ability to divert all or a portion of a nitrogen rejection unit feed stream to optionally bypass a nitrogen fractionation column to reduce capital costs and operating expenses.