Membrane Electrolytic CO2 Separation With Ammonia Recovery
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Solution Overview
Problem
Existing carbon dioxide capture and storage systems using ammonia absorbents require chemical pH adjustments to recover ammonia, leading to increased system size and energy consumption, and lack efficient methods for simultaneous separation of carbon dioxide and ammonia.
Innovation Solution
A carbon dioxide-separating apparatus utilizing a cation and anion exchange membrane system with separate cathode and anode channels for ammonia and carbon dioxide separation via electrolytic separation, eliminating the need for direct chemical pH adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical pH adjustment is used to recover ammonia absorbent, then ammonia can be recovered, but system size increases and energy consumption increases
Solution Approach 1:
The system divides the pH adjustment process into separate cathode and anode channels with distinct functions. The cathode channel performs pH increase for ammonia recovery while the anode channel performs pH decrease for CO2 release, allowing simultaneous separation and absorbent regeneration without requiring separate chemical addition systems.
Solution Approach 2:
Ion exchange membranes act as intermediaries to selectively transport ions between channels. The cation exchange membrane allows NH4+ transport to the cathode, while the anion exchange membrane allows HCO3- transport to the anode, enabling controlled pH adjustment without direct chemical addition and reducing system complexity.
2Reliability
If chemical pH adjustment is used to recover ammonia absorbent, then ammonia can be recovered, but energy consumption increases
Solution Approach 1:
The system replaces thermal energy-intensive chemical pH adjustment processes with electrical energy-driven electrochemical reactions. Electric current directly drives the pH increase at the cathode and pH decrease at the anode, eliminating the need for external chemical addition and associated energy consumption.
Solution Approach 2:
The system changes the pH parameter spatially and temporally through electrochemical reactions. The cathode channel maintains high pH for ammonia recovery while the anode channel maintains low pH for CO2 release, allowing continuous absorbent regeneration with controlled energy input.
3Reliability
If conventional stripping tower process is used, then carbon dioxide can be separated, but high temperature operation is required
Solution Approach 1:
The system utilizes phase transitions of CO2 through electrochemical pH control. At the anode, low pH conditions cause HCO3- to convert to CO2 gas which is then separated. This electrochemical phase transition occurs at ambient temperature, replacing thermal stripping.
Solution Approach 2:
The system changes the pH parameter to control CO2 separation instead of using temperature. The anode channel maintains low pH to promote CO2 release from HCO3-, enabling separation at ambient temperature conditions.
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
Enables simultaneous and selective separation of ammonia gas and carbon dioxide gas without additional chemicals, reducing system size and enabling continuous operation by reusing the absorbent.
Implementation Method 1
a cation exchange membrane and an anion exchange membrane spaced apart from each other to form a capture channel, through which a capture solution flows
Implementation Method 2
When power is applied to the cathode current collector plate and the anode current collector plate, ammonium ions in the capture solution pass through the cation exchange membrane and move to the cathode channel, and bicarbonate ions in the capture solution pass through the anion exchange membrane and move to the anode channel
Data Source
AI summary
Proposed is an apparatus for separating CO2 gas captured with ammonia gas as an absorbent and the ammonia gas from a capture solution. The apparatus includes cation and anion exchange membranes spaced apart from each other to form a capture channel therebetween for a capture solution flow, cathode and anode current collector plates and their corresponding cation and anode exchange membranes forming cathode and anode channels therebetween, respectively. In the separate channels, basic and acidic solutions flow. Power applied to the collector plates drives ammonium and bicarbonate ions from the capture solution through the membranes, and then the ions convert into ammonia and CO2 gases in a chemical reaction, respectively. Through the power application with the basic and acidic solution flows through the corresponding channels, and a flow-conductive acid/base electrolytic separation method, gas separation without directly adding an acidic or basic solution to a capture solution is possible.