Dual-Reflux Heavies Removal Column for High-Pressure LNG Separation
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Solution Overview
Problem
LNG facilities face challenges in minimizing compressor/driver horsepower requirements while efficiently separating heavy hydrocarbon materials from natural gas streams, as operating pressure affects separation efficiency and energy consumption.
Innovation Solution
A method involving a dual-refluxed heavies removal column process, where a first reflux stream with high methane content and a second reflux stream, comprising a portion of the bottoms stream, are introduced into a distillation column at different elevations to enhance separation efficiency and allow operation at higher pressures without reducing separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the distillation column operates at higher pressure to minimize compressor horsepower requirements, then energy consumption is reduced, but separation efficiency of heavy hydrocarbons deteriorates rapidly
Solution Approach 1:
The single distillation column is divided into two separate distillation columns operating at different pressures. The first column operates at higher pressure to minimize compressor horsepower, while the second column operates at lower pressure to ensure efficient heavy hydrocarbon separation. This segmentation allows each column to optimize for its specific function, resolving the contradiction between energy consumption and separation efficiency.
Solution Approach 2:
The system changes the operating pressure parameter between two distinct stages. The first distillation column operates at a first pressure optimized for energy efficiency, while the second distillation column operates at a second pressure optimized for separation efficiency. This parameter change allows the system to achieve both low energy consumption and high separation performance.
2Manufacturing precision
If the distillation column operates at reduced pressure to avoid heavies carryover, then separation efficiency is maintained, but energy consumption and operating costs increase
Solution Approach 1:
The separation process is segmented into two columns: the first column handles the bulk separation at higher pressure (lower energy consumption), while the second column performs the final heavy hydrocarbon removal at lower pressure (higher separation efficiency). This segmentation allows the system to achieve both goals without compromising either.
Solution Approach 2:
The first distillation column acts as an intermediary that pre-separates the heavy hydrocarbons before the stream enters the second column. This intermediary separation reduces the burden on the second column, allowing it to operate at lower pressure with optimized separation efficiency while the first column compensates for the energy consumption.
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 effectively minimizes compressor horsepower requirements and ensures efficient separation of heavy hydrocarbons, maintaining separation efficiency at higher operating pressures, thus reducing energy consumption and operating costs.
Implementation Method 1
separating the cooled predominantly methane stream in a distillation column to thereby produce a bottoms stream and an overhead stream
Implementation Method 2
cooling a predominantly methane stream in a refrigeration cycle
Data Source
AI summary
A liquefied natural gas facility employing a heavies removal column having multiple reflux streams. The reflux streams can have different compositions and can be operable to reduce the critical pressure of the fluids within the heavies removal column in order to permit the column to operate at higher pressures without adversely affecting the horsepower requirements of plant compressor/driver systems.