LNG Fractionation Feed Splitting for High Ethane Recovery
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Solution Overview
Problem
Current processes for separating ethane and heavier hydrocarbons from liquefied natural gas (LNG) often compromise between high recovery, low utility costs, and process simplicity, requiring significant capital investment and utility consumption.
Innovation Solution
A novel process that splits the LNG feed into two portions, using low-level utility heat and refrigeration from cold LNG to optimize fractionation, reducing the need for high-level utility heat and minimizing capital investment by maintaining processing equipment simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional LNG separation processes are used to achieve high ethane or propane recovery, then separation effectiveness is improved, but capital investment and utility costs increase significantly
Solution Approach 1:
The LNG feed stream is divided into two separate feeds for the demethanizer column. One feed is a cold liquid stream that is pumped directly to the column, while the other is a warmer liquid stream that provides partial vaporization and acts as both feed and internal reflux. This segmentation eliminates the need for complex refrigeration systems and high-level utility heat while maintaining effective separation of ethane and propane from methane.
Solution Approach 2:
The warmer liquid stream serves a dual function: it acts as a feed stream to the demethanizer and simultaneously provides internal reflux through partial vaporization within the column. This self-service approach eliminates the need for separate reflux systems and reduces utility requirements, achieving high recovery without increased capital investment.
2Manufacturing precision
If conventional LNG separation processes are used to achieve high ethane or propane recovery, then separation effectiveness is improved, but utility consumption increases
Solution Approach 1:
The process utilizes temperature parameter variation by introducing a warmer liquid stream (at a temperature higher than the LNG feed) into the demethanizer. This temperature difference causes partial vaporization of the warmer stream, generating internal reflux without requiring external high-level heat utility. The parameter change in temperature enables the system to achieve effective separation with reduced utility consumption.
Solution Approach 2:
The warmer liquid stream undergoes partial vaporization (phase transition from liquid to vapor) within the demethanizer column, generating internal reflux. This phase transition occurs without external heating utilities because the warmer stream's temperature is sufficient to cause vaporization at the column operating conditions. The phase transition effectively provides the reflux needed for high separation effectiveness while minimizing utility 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 achieves high ethane or propane recovery with reduced energy consumption and lower operating costs, while maintaining efficient separation of methane-rich lean LNG and natural gas liquids, thereby minimizing capital investment.
Implementation Method 1
a first fractionation column receiving the heated LNG stream and performing a fractionation of the heated LNG stream to produce a methane-rich lean LNG stream and a natural gas liquids stream
Implementation Method 2
the heated LNG stream is vaporized to form a vapor stream that is separated into a vapor portion and a liquid portion
Data Source
AI summary
A process and apparatus for the recovery of ethane, ethylene, propane, propylene, and heavier hydrocarbons from a liquefied natural gas (LNG) stream is disclosed. The LNG feed stream is divided into two portions. The first portion is supplied to a fractionation column at an upper mid-column feed point. The second portion is directed in heat exchange relation with a warmer distillation stream rising from the fractionation stages of the column, whereby this portion of the LNG feed stream is partially vaporized and the distillation stream is totally condensed. The condensed distillation stream is divided into a “lean” LNG product stream and a reflux stream, whereupon the reflux stream is supplied to the column at a top column feed position. The partially vaporized portion of the LNG feed stream is separated into vapor and liquid streams which are thereafter supplied to the column at lower mid-column feed positions. The quantities and temperatures of the feeds to the column are effective to maintain the column overhead temperature at a temperature whereby the major portion of the desired components is recovered in the bottom liquid product from the column.