Sweep-Based Membrane CO₂ Capture for Gas-Fired Power Plants
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Solution Overview
Problem
Current membrane-based CO2 capture processes for gas-fired power plants are limited by the high temperature of the compressed gas streams, which requires expensive inorganic membranes or extensive cooling, making the process costly and inefficient.
Innovation Solution
Integrating a sweep-based membrane gas separation step between compression stages, allowing for carbon dioxide capture at intermediate pressures (2-10 bar) and temperatures (100-200°C), enabling the use of polymeric membranes and reducing the need for extensive cooling, thus simplifying the process and reducing energy and cost requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If membrane-based CO2 capture is applied to hot compressed gas streams (500-800°C), then CO2 separation can be performed, but expensive inorganic membranes or extensive cooling is required
Solution Approach 1:
The patent applies preliminary cooling to reduce the temperature of compressed gas streams from 500-800°C to below 200°C before membrane separation. This preliminary action enables the use of cost-effective polymeric membranes by preparing the gas stream in advance to meet the temperature requirements of cheaper membrane materials.
Solution Approach 2:
The patent changes the temperature parameter of the gas stream from high (500-800°C) to low (<200°C) to enable the use of polymeric membranes instead of expensive inorganic membranes. This parameter change fundamentally alters which membrane materials are economically viable.
2Ease of manufacture
If extensive cooling is applied to compressed gas streams, then polymeric membranes can be used, but energy requirements and process complexity increase
Solution Approach 1:
The patent merges the cooling function with the existing heat recovery steam generator (HRSG) system. The HRSG, which already cools turbine exhaust for steam generation, is extended to also cool the compressed gas stream for membrane separation, combining two cooling functions into one system and avoiding duplicate cooling infrastructure.
Solution Approach 2:
The heat recovery steam generator is given multiple functions: it cools the turbine exhaust stream for steam generation and also cools the compressed gas stream to enable membrane separation. This multi-functionality eliminates the need for separate cooling systems and reduces overall energy requirements.
3Adaptability or versatility
If CO2 capture is integrated into existing gas turbine plants, then retrofittability is improved, but modifications to highly optimized turbines are required
Solution Approach 1:
The patent segments the CO2 capture system into separate modules (compression, cooling, membrane separation) that can be added to existing gas turbine plants without modifying the turbine itself. This modular segmentation allows retrofittability while maintaining the original turbine's optimization.
Solution Approach 2:
The patent introduces intermediate equipment (separate compressors, heat exchangers, membrane units) that act as mediators between the gas turbine and CO2 separation. These intermediaries enable CO2 capture functionality without requiring direct modifications to the highly optimized turbine design.
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 achieves significant energy and cost savings by enabling efficient CO2 capture with polymeric membranes, reducing the carbon dioxide content in turbine exhaust gases and enhancing the overall economic viability of CO2 separation from gas-fired power plants.
Implementation Method 1
membranes that are selective in favor of carbon dioxide over oxygen and nitrogen
Implementation Method 2
a sweep gas stream, 428, comprising air, oxygen-enriched air or oxygen flows across the permeate side. The membrane separation step divides stream 425 into residue stream 429, depleted in carbon dioxide as compared to feed stream 425, and permeate stream/sweep stream 430
Data Source
AI summary
Sweep-based gas separation processes for reducing carbon dioxide emissions from gas-fired power plants. The invention involves at least two compression steps, a combustion step, a carbon dioxide capture step, a power generate step, and a sweep-based membrane separation step. One of the compression steps is used to produce a low-pressure, low-temperature compressed stream that is sent for treatment in the carbon dioxide capture step, thereby avoiding the need to expend large amounts of energy to cool an otherwise hot compressed stream from a typical compressor that produces a high-pressure stream, usually at 20-30 bar or more.