Sweep Gas Membrane Separation for CO2 Capture

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Solution Overview

Problem

Current membrane-based gas separation technologies face challenges in efficiently and economically removing carbon dioxide from combustion gases, particularly in large-scale industrial settings like power plants, due to limitations in membrane selectivity and pressure ratios, which restrict the concentration of carbon dioxide that can be achieved.

Innovation Solution

A process involving membrane-based gas separation using a sweep gas on the permeate side to enhance the driving force for carbon dioxide removal, combined with multiple membrane separation steps and carbon dioxide capture technologies, which selectively permeable membranes to concentrate carbon dioxide and recycle it back to the combustion process, reducing the carbon dioxide content in flue gas emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional membrane-based gas separation is used without sweep gas, then the process is simpler, but carbon dioxide removal efficiency is insufficient

Engineering Contradiction:

Improvecarbon dioxide removal efficiencyVSAvoidprocess complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

A sweep gas stream is introduced as an intermediary on the permeate side of the membrane to enhance carbon dioxide removal. The sweep gas creates a concentration gradient that drives carbon dioxide through the membrane more effectively, acting as a mediator to improve separation efficiency without requiring complex pressure control systems

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the operational parameters by introducing a sweep gas flow rate parameter and adjusting the composition of the permeate stream. By varying the sweep gas flow and composition, the system optimizes carbon dioxide removal efficiency while maintaining flexible control over the separation process

Inventive Principle:

Principle #35Parameter changes

2Productivity

If total pressure difference is applied by compressing feed stream, then carbon dioxide permeation is enhanced, but energy consumption increases

Engineering Contradiction:

Improvecarbon dioxide permeation rateVSAvoidenergy consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The invention replaces the mechanical compression system with a sweep gas-based driving force mechanism. Instead of using compressors to create pressure differential, the system uses the concentration gradient created by sweep gas flow to drive carbon dioxide permeation, significantly reducing mechanical energy consumption

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The sweep gas system enables the membrane process to be self-driven by the concentration gradient it creates. The permeate side composition is continuously refreshed by the sweep gas, maintaining a natural driving force for permeation without requiring external energy input for pressure maintenance

Inventive Principle:

Principle #25Self-service

3Productivity

If high carbon dioxide concentration is achieved in permeate stream, then capture efficiency improves, but membrane selectivity requirements increase

Engineering Contradiction:

Improvecarbon dioxide capture efficiencyVSAvoidmembrane selectivity requirement

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention applies partial action by using sweep gas to achieve sufficient carbon dioxide removal without requiring perfect membrane selectivity. The sweep gas compensates for moderate membrane performance by continuously refreshing the permeate side concentration, allowing high capture efficiency with less demanding membrane materials

Inventive Principle:

Principle #16Partial or excessive action

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 carbon dioxide emissions to less than 5 vol% in flue gas, facilitating more efficient capture and sequestration, while minimizing energy consumption and capital costs by utilizing existing combustion air as the sweep gas and optimizing membrane module configurations.

Implementation Method 1

a driving force for transmembrane permeation may be supplied by passing a sweep gas across the permeate side of the membranes, thereby lowering the partial pressure of a desired permeant on that side to a level below its partial pressure on the feed side

Methodology Applied

Scientific EffectPermeation: Permeation

Implementation Method 2

lowering the partial pressure of a desired permeant on that side to a level below its partial pressure on the feed side

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS8025715B2Process for separating carbon dioxide from flue gas using parallel carbon dioxide capture and sweep-based membrane separation steps

Publication Date: 2011.09.27 MEMBRANE TECHNOLOGY & RESEARCH INC

AI summary

A gas separation process for treating flue gases from combustion processes, and combustion processes including such gas separation. The invention involves routing a first portion of the flue gas stream to be treated to a carbon dioxide capture step, while simultaneously flowing a second portion of the flue gas across the feed side of a membrane, flowing a sweep gas stream, usually air, across the permeate side, then passing the permeate/sweep gas to the combustor.