CO2 Purification Using Membrane-Distillation Recycling
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Solution Overview
Problem
Current processes for carbon dioxide recovery from gas mixtures, such as boiler flue gas and lime kiln gas, are energy-intensive and inefficient, particularly in achieving high purity and recovery rates without the use of solvents like amines.
Innovation Solution
A process integrating membrane technology and carbon dioxide distillation, where a gas mixture is pretreated, fractionated, and then passed through a membrane selective to carbon dioxide, with the carbon dioxide permeate recycled and used as a self-refrigerant to enhance recovery and purity, eliminating the need for solvent-based purification methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solvent-based scrubbing processes are used to recover carbon dioxide from low carbon dioxide content streams, then carbon dioxide recovery is achieved, but energy consumption increases significantly
Solution Approach 1:
The patent changes the physical parameters of the gas mixture by cooling it to below its dew point temperature, causing water vapor to condense and separate. This parameter change enables subsequent membrane separation to work more effectively at lower temperatures, reducing the energy required for compression and processing compared to conventional heated scrubbing processes.
Solution Approach 2:
The patent replaces the chemical absorption mechanism (solvent-based scrubbing) with a physical separation mechanism using temperature-dependent condensation and membrane permeation. This substitution eliminates the need for energy-intensive solvent regeneration processes while achieving comparable or superior carbon dioxide recovery.
2Manufacturing precision
If conventional purification processes are used to achieve high purity carbon dioxide, then product specifications are met, but the process becomes expensive in energy
Solution Approach 1:
The patent performs preliminary cooling and condensation of water vapor before the membrane separation step. This preliminary action removes the majority of water content early in the process, reducing the burden on subsequent drying and purification steps and thereby lowering the total energy required to achieve high purity carbon dioxide.
Solution Approach 2:
The patent introduces a membrane as an intermediary separation medium that selectively permits carbon dioxide to pass through while retaining other gases. This intermediary enables high-purity carbon dioxide recovery without requiring multiple stages of conventional purification, each of which would consume additional energy.
3Quantity of substance
If carbon dioxide is recovered from low carbon dioxide content streams, then carbon dioxide supply is increased, but the process complexity increases
Solution Approach 1:
The patent segments the purification process into distinct functional stages: cooling/condensation, membrane separation, and drying. Each stage performs a specific separation function, making the overall complex process more manageable and easier to optimize. The segmentation allows low carbon dioxide content streams to be processed efficiently through specialized units rather than a single complex system.
Solution Approach 2:
The cooling system serves multiple functions: it condenses water vapor for removal, cools the gas for more efficient membrane separation, and prepares the stream for subsequent drying. This multi-functionality reduces the need for separate equipment and simplifies the overall process design while increasing carbon dioxide recovery from low-concentration streams.
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 process achieves high purity carbon dioxide recovery rates of over 90% from low carbon dioxide content streams, reducing energy consumption and greenhouse gas emissions, while enabling efficient reuse of carbon dioxide for enhanced oil recovery and other applications.
Implementation Method 1
passing the overheads fraction over a membrane selective to carbon dioxide to separate a carbon dioxide permeate from a residue gas comprising the light gases
Implementation Method 2
cooling the compressed gas mixture to below about a dew point temperature of the gas mixture to condense a portion of water vapor present in the compressed gas mixture
Implementation Method 3
fractionating the cooled gas mixture to recover a bottoms fraction comprising carbon dioxide and an overheads fraction comprising carbon dioxide and the light gases
Data Source
AI summary
A process for the recovery of carbon dioxide from a gas mixture that includes pretreating a gas mixture comprising carbon dioxide, water vapor, and one or more light gases in a pretreating system to form a cooled gas mixture, fractionating the cooled gas mixture to recover a bottoms fraction comprising carbon dioxide and an overheads fraction comprising carbon dioxide and the light gases, passing the overheads fraction over a membrane selective to carbon dioxide to separate a carbon dioxide permeate from a residue gas comprising the light gases, recycling the carbon dioxide permeate to the pretreating system, and recovering at least a portion of the bottoms fraction as a purified carbon dioxide product stream is described.