Nitrogen Rejection Rectification With Expanded Reflux Refrigeration
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Solution Overview
Problem
Existing nitrogen rejection units (NRUs) face inefficiencies in separating nitrogen-rich fractions from feed fractions containing nitrogen and hydrocarbons, as the compressor's capacity utilization is limited by varying nitrogen concentrations, leading to increased costs and operational limitations, especially in processes like Enhanced Oil Recovery where nitrogen content increases over time.
Innovation Solution
A method where a partial flow of the compressed nitrogen-rich fraction is expanded and evaporated for refrigeration purposes, allowing the compressor to be utilized efficiently across all nitrogen concentrations, and integrating refrigeration capacity to enhance product fraction delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the compressor is used exclusively to maintain nitrogen-rich fraction purity, then nitrogen separation efficiency is improved, but compressor capacity utilization is limited when nitrogen content in feed fraction is low
Solution Approach 1:
The compressor is designed to perform multiple functions: maintaining nitrogen-rich fraction purity and providing refrigeration capacity. By integrating refrigeration into the nitrogen rejection unit, the compressor can utilize its full capacity regardless of nitrogen concentration levels in the feed fraction, thereby resolving the contradiction between separation efficiency and capacity utilization.
Solution Approach 2:
The system changes operational parameters dynamically based on nitrogen content in the feed fraction. When nitrogen content is low, the compressor operates at higher capacities to provide refrigeration; when nitrogen content is high, it focuses on separation. This parameter adjustment allows optimal utilization across varying operating conditions.
2Quantity of substance
If nitrogen content in feed fraction increases over time, then refrigeration demand increases, but compressor operation becomes inoperable above certain nitrogen concentration
Solution Approach 1:
The integrated refrigeration system allows the compressor to maintain operation across the full range of nitrogen concentrations. The refrigeration function becomes increasingly important as nitrogen content rises, allowing the compressor to remain operational even at high nitrogen concentrations where traditional separation-only systems would fail.
Solution Approach 2:
The system ensures continuous useful action by the compressor across all operating conditions. As nitrogen content increases, the compressor continuously provides both separation and refrigeration functions, preventing operational shutdown and maintaining process continuity throughout the feed fraction's lifecycle.
3Adaptability or versatility
If compressor capacity is selected for maximum nitrogen content, then operational range is extended, but compressor is underutilized when nitrogen content is low
Solution Approach 1:
The compressor is designed with universal functionality to perform both nitrogen separation and refrigeration. This allows the system to operate efficiently across the maximum operational range while maintaining high utilization efficiency, as the refrigeration function compensates for reduced separation demands when nitrogen content is low.
Solution Approach 2:
The system dynamically adjusts the balance between separation and refrigeration functions based on real-time nitrogen content. This dynamic operation ensures the compressor remains highly utilized across varying conditions, optimizing both operational range and efficiency rather than operating at fixed parameters.
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 ensures optimal compressor utilization and extends the operational range of nitrogen rejection units, enabling efficient separation and refrigeration, thereby amortizing compressor investment costs and maintaining process stability under changing nitrogen concentrations.
Implementation Method 1
at least a partial flow of the compressed nitrogen-rich fraction is expanded after condensation has taken place and for the purpose of refrigeration is at least partially, preferably completely evaporated
Implementation Method 2
a partial flow of the compressed nitrogen-rich fraction is expanded and evaporated for refrigeration purposes
Implementation Method 3
The partially condensed starting fraction is fed to a pre-separation column T1 via line 1'
Implementation Method 4
via line 3" and expansion valve b to the low-pressure column T2
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for removing a nitrogen-rich fraction from a feed fraction which substantially contains nitrogen and hydrocarbons. According to said method, the feed fraction is subjected to separation into a nitrogen-rich and a methane-rich fraction by rectification, the methane-rich fraction being evaporated and then superheated at as high a pressure as possible relative to the feed fraction to be cooled for refrigeration and the nitrogen-rich fraction being compressed at least temporarily and/or at least partially and being fed to the rectification reaction as a return flow. At least one partial flow (16) of the compressed (C) nitrogen-rich fraction (9') is at least temporarily expanded (f) once condensation (E1) is completed and is at least partially, preferably completely evaporated (E1) for refrigeration.