Compact NGL Recovery Assembly With Integrated Overhead Rectification
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Solution Overview
Problem
Conventional cryogenic expansion processes for natural gas liquids recovery are inefficient in recovering C2 and C3 components due to lack of additional rectification and require surplus compression capacity, leading to significant losses and increased capital and operating costs.
Innovation Solution
A novel process that integrates additional rectification by combining flash expanded streams with column overhead vapor, using a heat and mass transfer means to provide continuous contact between vapor and liquid phases, enhancing recovery without additional residue gas compression and reducing capital costs through a compact arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
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 and C3 components is insufficient leading to significant losses
Solution Approach 1:
The invention divides the vapor stream into two separate streams: one stream is expanded through an expansion machine to produce cold expanded vapor, while the other stream is condensed to produce liquid. These two segmented streams are then recombined in the fractionation column, allowing for improved separation efficiency and reduced component losses without complicating the overall process flow
Solution Approach 2:
The invention introduces a vertical dimension to the separation process by implementing an upper absorber section above the feed point in the fractionation column. This additional spatial dimension enables the liquid from the expansion machine to flow downward and absorb C2 and C3 components from the rising vapor stream, significantly improving recovery efficiency
2Manufacturing precision
If additional rectification is implemented to improve recovery efficiency, then the separation precision increases, but the device complexity and capital costs increase
Solution Approach 1:
The invention merges the expansion machine outlet with the fractionation column by directing the expanded vapor directly into the column above the feed point. This integration allows the expansion cooling effect to occur within the column environment, providing additional rectification without requiring separate equipment or complex interconnections
Solution Approach 2:
The fractionation column is designed to perform multiple functions: it serves as both the primary separation vessel and the location for the expansion machine outlet. The upper portion of the column acts as an absorber section while the lower portion performs traditional fractionation, allowing a single device to achieve enhanced separation precision without adding dedicated equipment
3Loss of substance
If traditional fractionation columns are used, then the equipment simplicity is maintained, but the recovery of C2 and C3 components is insufficient
Solution Approach 1:
The invention applies preliminary cooling action by expanding a portion of the vapor stream through an expansion machine before it enters the fractionation column. This pre-cooling and partial condensation occurs above the feed point, creating a liquid phase that will subsequently absorb hydrocarbon components as it flows downward through the column, thereby improving recovery precision
Solution Approach 2:
The liquid stream from the expansion machine acts as an intermediary medium that facilitates the transfer of C2 and C3 components from the vapor phase to the liquid phase. This intermediary liquid flows downward through the column, absorbing hydrocarbon components and enabling more precise recovery without requiring additional separation equipment
4Productivity
If surplus compression capacity is added to improve recovery, then the productivity increases, but the power consumption and operating costs increase
Solution Approach 1:
The expansion machine serves a dual function: it expands the vapor stream to drive the compression process while simultaneously providing cooling to enable condensation and absorption. The cold expanded vapor from the expansion machine is used directly within the process to cool and condense other streams, allowing the system to serve itself and reducing the need for additional compression capacity and associated power 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
Achieves C2 recoveries exceeding 95% and C3 recoveries of 99% with reduced power consumption, increasing process efficiency and annual revenue, while minimizing environmental emissions by reducing piping and potential leak sources.
Implementation Method 1
a heat and mass transfer means to provide continuous contact between vapor and liquid phases
Implementation Method 2
the vaporization occurring during expansion of the liquids results in further cooling of the stream
Implementation Method 3
provide continuous contact between vapor and liquid phases, enhancing recovery
Implementation Method 4
cryogenic processes have become popular because of the availability of economical equipment that produces power while simultaneously expanding and extracting heat from the gas being processed
Implementation Method 5
The expanded stream, comprising a mixture of liquid and vapor, is fractionated in a distillation (demethanizer or deethanizer) column
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 tower overhead vapor is directed to an absorbing means and a heat and mass transfer means inside a processing assembly. A portion of the outlet vapor from the processing assembly is compressed to higher pressure, cooled and substantially condensed in a heat exchange means inside the processing assembly, then expanded to lower pressure and supplied to the heat and mass transfer means to provide cooling. Condensed liquid from the absorbing means is fed to the tower.