Method for producing a methane-rich stream and a c2+ hydrocarbon-rich fraction from a natural feed gas stream, and corresponding equipment
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Solution Overview
Problem
Existing processes for recovering C2+ hydrocarbons from natural gas are inefficient and energy-intensive, especially when the feedstock is rich in heavy hydrocarbons like ethane, propane, and butane, and require additional refrigeration cycles that are costly or impractical in installations such as floating factories.
Innovation Solution
A method involving countercurrent heat exchange, recirculation streams, and dynamic expansion to optimize the separation process, reducing energy consumption and maintaining high ethane recovery rates without the need for external refrigeration cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional distillation processes are used to recover C2+ hydrocarbons from natural gas, then separation can be achieved, but energy consumption increases significantly and ethane recovery decreases when feedstock is rich in heavy hydrocarbons
Solution Approach 1:
The patent changes the operating parameters of the distillation column, specifically operating at elevated pressures (50-150 psig) rather than atmospheric pressure. This pressure change modifies the vapor-liquid equilibrium relationships, improving separation efficiency and ethane recovery while managing energy requirements. The reflux temperature is also optimized to enhance condensation efficiency without excessive cooling costs.
Solution Approach 2:
The patent implements preliminary cooling of the feedstock natural gas before it enters the distillation column. By pre-cooling the feed to temperatures below its dew point, the process prepares the material in an optimal state for separation, reducing the energy burden on the distillation column itself and improving overall ethane recovery efficiency.
2Manufacturing precision
If additional refrigeration cycles are added to improve separation selectivity, then C2+ hydrocarbon recovery improves, but device complexity and cost increase
Solution Approach 1:
The patent combines the refrigeration function with the distillation process itself by using the distillation column's condenser as the primary cooling device. The reflux stream provides both the separation function and the cooling function, eliminating the need for separate external refrigeration cycles. This integration maintains high separation selectivity while significantly reducing system complexity.
Solution Approach 2:
The distillation column serves its own cooling requirements through its reflux system. The condensed overhead vapor is returned as reflux, providing continuous cooling without external refrigeration. The system essentially cools itself using the thermal dynamics of the distillation process, eliminating dependency on additional refrigeration infrastructure.
3Temperature
If external propane refrigeration cycles are installed to cool natural gas, then cooling capacity increases, but installation cost and safety risks increase
Solution Approach 1:
The patent extracts the refrigeration function from external propane-based systems and integrates it directly into the distillation column's internal reflux system. By removing the dependency on external refrigeration cycles, the process eliminates the associated high installation costs and safety risks while maintaining effective natural gas cooling capability through the column's own thermal dynamics.
4Productivity
If refrigeration is used to maintain low inlet temperatures for high ethane recovery, then selectivity improves, but energy consumption increases
Solution Approach 1:
The patent utilizes phase transitions (condensation and vaporization) within the distillation column to achieve cooling without external refrigeration. The overhead vapor condenses on the reflux drum, releasing latent heat that is managed within the system. This phase change-driven cooling maintains low inlet temperatures for high ethane recovery while avoiding the continuous energy input required by mechanical refrigeration systems.
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
The method achieves ethane recovery greater than 99% while significantly reducing energy consumption, making it suitable for installations with high C2+ hydrocarbon content and eliminating the need for additional refrigeration cycles, thus improving operational efficiency and reducing costs.
Implementation Method 1
the feedstock natural gas stream is cooled by heat exchange with an overhead stream from the separation column
Implementation Method 2
the cooled feedstock natural gas stream is separated into a light fraction and a heavy fraction in a separator drum
Implementation Method 3
The light fraction is dynamically expanded in an expansion turbine
Implementation Method 4
The expanded light fraction stream is cooled by heat exchange with the feedstock natural gas stream
Implementation Method 5
The cooled and expanded light fraction stream is separated into a vapor phase and a liquid phase in a second separator drum
Implementation Method 6
the bottoms stream rich in C2+ hydrocarbons is pumped and is heated by countercurrent heat exchange of at least a portion of the natural gas feed stream
Implementation Method 7
a separation column, fed with the cooled feedstock natural gas stream, operated at a pressure higher than the pressure of the feedstock natural gas stream, to separate the cooled feedstock natural gas stream into a methane-rich overhead stream and a stream rich in C2+ hydrocarbons at the bottom
Data Source
AI summary
The invention relates to a method including cooling natural feed gas (15) in a first heat exchanger (16), and injecting the cooled natural feed gas (40) into a first disengager (18). The method includes dynamically expanding a turbine feed stream (46) in a first expansion turbine (22), and injecting the expanded stream (102) into a splitter (26). Said method comprises removing, at the head of the splitter (26), a head stream (82) rich in methane, and removing a first recirculation stream (88) from the compressed methane-rich head stream (86). The method includes forming at least one second recirculation stream (96) obtained from the methane-rich head stream (82) downstream from the splitter (26) and forming a dynamic expansion stream (100) from the second recirculation stream (96).