Method for producing a methane-rich stream and a C<sub>2</sub><sup>+</sup> hydrocarbon-rich stream, and associated equipment
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Solution Overview
Problem
Current methods for separating C2+ hydrocarbons from natural gas, such as cryogenic expansion, are economically constrained and require significant equipment bulk, with high methane extraction output and safety concerns, particularly in floating or safety-sensitive areas.
Innovation Solution
The method involves expanding a second fraction of the feed stream in a second dynamic expansion turbine to a pressure equal to the first pressure, cooling, and partially liquefying it to form a cooled reflux stream, which is injected into a distillation column, along with additional heat exchange steps to enhance separation efficiency and reduce equipment bulk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cryogenic expansion methods are used to separate C2+ hydrocarbons from natural gas, then ethane recovery rate is improved, but equipment bulk and complexity increase
Solution Approach 1:
The feed stream is divided into two fractions: a first fraction that is cooled and expanded through a turbine, and a second fraction that bypasses the heat exchanger and is expanded directly. This segmentation allows different portions of the feed to follow different processing paths, reducing overall equipment bulk while maintaining high recovery rates
Solution Approach 2:
Only part of the feed stream (the first fraction) undergoes full cryogenic cooling and expansion through the turbine. The second fraction takes a shorter path with direct expansion. This partial application of the full cryogenic process reduces equipment requirements while still achieving high ethane recovery through the combined streams
2Productivity
If cryogenic expansion methods are used to separate C2+ hydrocarbons from natural gas, then ethane recovery rate is improved, but device complexity increases
Solution Approach 1:
The processing system is segmented into two parallel paths: one for the first fraction through the heat exchanger and turbine, and another for the second fraction that bypasses these components. This segmentation simplifies the overall device complexity by allowing certain components to be optional or reduced in scale
Solution Approach 2:
The expansion turbines serve multiple functions: they expand the hydrocarbon stream for separation, generate power to drive compressors, and provide cooling through the expansion process. This multi-functionality reduces the need for separate dedicated equipment, thereby reducing overall device complexity
3Productivity
If outside refrigerants such as propane are used in cryogenic expansion, then methane extraction output is improved, but safety concerns increase in floating or safety-sensitive areas
Solution Approach 1:
The system uses the feed stream itself (natural gas containing methane and ethane) as the working fluid for expansion and cooling, rather than introducing outside refrigerants like propane. The hydrocarbons in the feed stream serve their own separation and cooling needs, eliminating the need for additional hazardous refrigerant materials
Solution Approach 2:
The expansion turbines act as intermediaries that convert the pressure energy of the feed stream into mechanical work and cooling effect, eliminating the need for outside refrigerants. The turbines mediate the energy transformation directly using the feed stream's own properties
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 significantly reduces energy consumption while maintaining high selectivity for ethane extraction, achieving ethane recovery rates greater than 90% with reduced power consumption and minimal use of outside refrigerants.
Implementation Method 1
expanding a turbine feed fraction formed from the light head stream in a first dynamic expansion turbine up to a first pressure
Implementation Method 2
cooling the first fraction of the feed stream in a first heat exchanger
Implementation Method 3
injecting at least part of the first expanded fraction coming from the first turbine into a first distillation column
Data Source
AI summary
This method comprises a separation of a feed stream (16) into a first fraction (41A) and a second fraction (41B). It comprises injecting the first cooled feed fraction (42) into a first separating flask (22) to produce a light head stream (44).The method comprises expanding a turbine feed fraction (48) resulting from the light head stream (44) in a first turbine (26) up to a first pressure and injecting the first expanded fraction (54) into a distillation column (30).The method comprises expanding the second fraction of the feed stream (41B) in a second turbine (40) up to a second pressure substantially equal to the first pressure.The second expanded fraction (91A) from the second dynamic expansion turbine (40) is used to form a cooled reflux stream (91B) injected into the column (30).