Compact NGL Processing Assembly With Integrated Rectification
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Solution Overview
Problem
Conventional cryogenic expansion processes for natural gas liquids recovery are inefficient in recovering C2, C3, and heavier hydrocarbon components due to losses in the demethanizer column, particularly in plants lacking upper absorber sections and surplus compression capacity, leading to reduced product recovery and increased operational costs.
Innovation Solution
A novel process that integrates additional rectification using a heat and mass transfer means within a compact processing assembly, allowing indirect cooling and simultaneous mass transfer to enhance the recovery of C3 components without requiring additional compression or fractionation capacity, thereby reducing capital and operating costs and environmental emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cryogenic expansion processes are used for natural gas liquids recovery, then the process simplicity and ease of operation are maintained, but the recovery efficiency of C2, C3, and heavier hydrocarbon components is reduced due to losses in the demethanizer column
Solution Approach 1:
The invention divides the fractionation process into two distinct sections: a demethanizer section for removing methane and a rectifying section for recovering C2, C3, and heavier hydrocarbons. This segmentation allows each section to be optimized for its specific function, with the rectifying section specifically designed to minimize hydrocarbon losses while maintaining process simplicity.
2Productivity
If additional rectification equipment is added to improve C3 component recovery, then the product recovery increases, but the device complexity and capital investment increase
Solution Approach 1:
The invention merges the rectifying section with the existing demethanizer column structure, integrating additional mass transfer means within the same vessel. This combination achieves enhanced C3 component recovery (99% recovery) without requiring a completely separate fractionation tower, thereby limiting the increase in device complexity and capital investment.
3Use of energy by moving object
If traditional heat exchange and mass transfer methods are used, then the process design is conventional and straightforward, but the power consumption and environmental emissions are higher
Solution Approach 1:
The invention enables the processing assembly to serve itself by using the cold product streams from the fractionation process to provide cooling for the incoming gas feed. This self-service heat exchange system reduces or eliminates the need for external refrigeration, thereby reducing power consumption and associated environmental emissions from compression and refrigeration equipment.
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 C2 recoveries exceeding 89% and C3 recoveries of 99%, with significant economic benefits and improved efficiency, while reducing power consumption and potential environmental impacts by minimizing piping and flanged connections.
Implementation Method 1
The heat and mass transfer means provides indirect cooling and continuous contact between the liquid stream and the combined vapor stream so that it also functions to provide mass transfer between the vapor and liquid phases
Implementation Method 2
During expansion a portion of the liquid will vaporize, resulting in cooling of the total stream
Implementation Method 3
The flash expanded stream is then supplied as top feed to the demethanizer
Implementation Method 4
The heat and mass transfer means provides continuous contact between the condensed liquid and the combined vapor stream so that it also functions to provide mass transfer between the vapor and liquid phases, thereby providing rectification of the combined vapor stream
Implementation Method 5
The expanded stream, comprising a mixture of liquid and vapor, is fractionated in a distillation (demethanizer or deethanizer) column. In the column, the expansion cooled stream(s) is (are) distilled to separate residual methane, nitrogen, and other volatile gases as overhead vapor from the desired C2 components, C3 components, and heavier hydrocarbon components as bottom liquid product
Data Source
AI summary
A process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C2 (or C3) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the expanded first stream is heated to form a vapor fraction and a liquid fraction. The vapor fraction is combined with the tower overhead vapor, directed to a heat and mass transfer means inside a processing assembly, and cooled and partially condensed by the expanded first stream to form a residual vapor stream and a condensed stream. The condensed stream is combined with the liquid fraction and supplied to the tower at its top feed point.