Ammonia-Assisted CO2 Capture and Formate Production
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Solution Overview
Problem
Current CO2 electrolyzers fed with captured CO2 from air or flue gases require energy-intensive regeneration and pressurization processes, and bicarbonate electrolyzers using bipolar membranes suffer from inadequate local CO2 concentration and high electrical energy consumption.
Innovation Solution
An integrated flow electrolyzer system using ammonia (NH3) to capture CO2 as ammonium bicarbonate (NH4HCO3), which is then converted into formate in a thermal decomposition-driven process, substituting bipolar membranes with anion exchange membranes to reduce energy consumption and enhance CO2 concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bipolar membranes are used in bicarbonate electrolyzers to generate CO2 in situ, then CO2 can be produced from captured bicarbonate, but the local CO2 concentration remains inadequate and electrical energy consumption increases significantly
Solution Approach 1:
The patent extracts and removes the bipolar membrane component from the electrolyzer system, replacing it with a simpler membrane structure. This eliminates the energy-intensive water dissociation process while maintaining CO2 supply through alternative mechanisms, directly addressing both the energy consumption and CO2 concentration issues
Solution Approach 2:
The patent changes the operating parameters and chemical composition of the electrolyte system by using ammonia-based capture solutions instead of traditional bicarbonate systems. This parameter change enables more efficient CO2 release and higher local CO2 concentrations at the electrode surface without requiring the additional energy input from bipolar membranes
2Quantity of substance
If captured CO2 is released by heating the capturing media at 120-150°C, then CO2 can be regenerated for storage and transportation, but energy-intensive regeneration and pressurization processes are required
Solution Approach 1:
The patent replaces the thermal heating mechanism with an electrochemical approach. Instead of using heat to release CO2 from the capturing media, the system uses electrochemical reactions at the electrode surface to generate and concentrate CO2 in situ, eliminating the need for energy-intensive thermal regeneration and pressurization equipment
Solution Approach 2:
The patent introduces ammonia-based capture solutions as an intermediary substance that facilitates CO2 capture and subsequent electrochemical conversion. This intermediary enables a more energy-efficient pathway from CO2 capture to utilization, avoiding the high-temperature heating step required by traditional thermal release methods
3Productivity
If CO2 electrolyzers are fed with pressurized and purified CO2 gas, then the electrolysis process can proceed efficiently, but energy- and capital-intensive regeneration processes are required to produce the purified CO2
Solution Approach 1:
The patent merges the CO2 capture, regeneration, and electrolysis processes into a single integrated system. The CO2 capture solution is directly fed into the electrolyzer without requiring separate purification and pressurization stages, combining multiple functions into one streamlined process that maintains electrolysis efficiency while reducing overall system complexity
Solution Approach 2:
The patent creates a multi-functional system where the same ammonia-based solution serves multiple purposes: capturing CO2 from flue gases, serving as the electrolyte medium, and providing the source of CO2 for electrochemical conversion. This universal approach eliminates the need for separate purification and regeneration equipment, reducing both energy consumption and device complexity
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 a 3-fold increase in in-situ CO2 concentration, a 23% increase in formate faradaic efficiency, and a 35% reduction in cell voltage, while utilizing 99.8% of the CO2 capturing agent, making the process more sustainable and efficient.
Implementation Method 1
CO2 can be captured by ammonia (NH3) solution to form ammonium bicarbonate (NH4HCO3)
Implementation Method 2
the BPM requires an additional potential of 0.828 V (under standard conditions) for H+ generation by water dissociation
Implementation Method 3
CO2 can be electrochemically converted into valuable chemicals and fuels (i.e., the CO2 reduction reaction, or CO2RR)
Data Source
AI summary
The present disclosure relates to an electrochemical method for converting captured CO2 into formate (HCOO−). This method involves capturing waste CO2 by co-absorption of the waste CO2 with green ammonia (NH3) to form ammonium bicarbonate (NH4HCO3) and converting the ammonium bicarbonate (NH4HCO3) into formate (HCOO−), wherein said converting is carried out in an integrated flow electrolyzer system. Another aspect of the present disclosure relates to an integrated flow electrolyzer system comprising an alkaline electrolyzer for producing green NH3 from NO3−, an NH3—CO2 absorbing unit whereby waste CO2 is co-absorbed with ammonia (NH3) to form ammonium bicarbonate (NH4HCO3), and a bicarbonate electrolyzer for converting the ammonium bicarbonate (NH4HCO3) into formate (HCOO−).