Membrane Dehydration for Natural Gas Emission Control
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Solution Overview
Problem
Existing natural gas dehydration systems using glycol solvents emit toxic organic compounds, volatile organic compounds (VOCs), and greenhouse gases like methane, posing health and environmental hazards, and requiring improved emission control to meet stringent regulations.
Innovation Solution
Integration of a gas separation membrane unit using asymmetric polyimide membranes to selectively remove water vapor and recover methane, reducing emissions by recycling dehydrated gas back into the natural gas stream, and utilizing a vacuum or sweep gas to enhance water permeation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If glycol-based dehydration systems are used to remove water from natural gas, then dehydration efficiency is improved, but toxic organic compounds and greenhouse gases are emitted into the environment
Solution Approach 1:
The patent extracts and removes harmful organic compounds and greenhouse gases from the dehydration process off-gas stream using a membrane separation unit. The membrane selectively permeates water vapor while retaining organic compounds, effectively separating the harmful substances from the natural gas stream for appropriate disposal or recycling.
Solution Approach 2:
The patent changes the physical parameters of the off-gas stream by applying vacuum pressure or temperature control to enhance water vapor permeation through the membrane. By controlling pressure differential and temperature, the system optimizes water removal while preventing organic compound emission.
2Object-generated harmful factors
If off-gas is vented or flared to control emissions, then environmental regulations are met, but valuable methane gas is lost
Solution Approach 1:
The patent recovers valuable methane gas from the off-gas stream by selectively removing only water vapor through membrane separation. The dehydrated natural gas containing valuable methane is recycled back into the production stream, while only the necessary water component is discarded, achieving both emission control and resource recovery.
Solution Approach 2:
The patent implements a feedback loop where the dehydrated off-gas is recycled back to the dehydrator inlet or production stream. This closed-loop system continuously recovers valuable methane while maintaining emission control, turning what would be waste into a useful resource.
3Object-generated harmful factors
If conventional combustion methods are used to incinerate off-gas organics, then organic emissions are reduced, but energy consumption and operating costs increase
Solution Approach 1:
The patent replaces the thermal combustion system with a membrane separation system that uses physical separation based on selective permeability. This substitution eliminates the need for high-energy combustion processes while achieving equivalent or superior organic compound emission control through physical rather than thermal means.
Solution Approach 2:
The patent changes the approach from thermal treatment (combustion) to physical separation (membrane permeation). By controlling pressure and concentration gradients across the membrane, the system achieves organic compound removal with minimal energy input compared to combustion.
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 emissions by 97.7%, recovers valuable methane, and lowers operating costs, while meeting environmental and health regulations, with a 3-year payback on investment.
Implementation Method 1
The gas separation membrane has a high selectivity for water over organic compounds and may be an integrally skinned asymmetric polyimide membrane
Implementation Method 2
The driving force for water permeation is established by applying a vacuum on the permeate side of the membrane unit
Implementation Method 3
by flowing a sweep gas, for example warm and dry air, through the permeate side of the unit
Data Source
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AI summary
The off-gas from the still and flash tank of an existing glycol-based dehydration unit (containing water vapor, methane, BTEX (benzene, toluene, ethylbenzene, xylene), VOCs (volatile organic compounds)) is sent directly to a gas separation membrane system for dehydration. The gas separation membrane has a high selectivity for water over organic compounds (for example, the membrane described in WO2005/007277A1). The driving force for water permeation is established by applying a vacuum on the permeate side of the membrane unit or by flowing a sweep gas, for example warm, dry air through the permeate side of the unit.