Electrochemical Synthesis Gas Production with CO2 Scrubbing
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Solution Overview
Problem
Current electrolysis methods for converting electrical energy to synthesis gas result in a product with a 1:1:1 ratio of carbon monoxide to hydrogen to carbon dioxide, limiting the efficiency and value of energy storage, especially with high carbon dioxide emissions from fossil fuel combustion.
Innovation Solution
A method and apparatus that electrochemically produce synthesis gas with a minimum proportion of carbon dioxide by reducing CO2 to carbon monoxide in a carbon dioxide electrolysis cell and splitting water to produce hydrogen in a water electrolysis cell, using a gas scrubbing apparatus with catholytes to remove unconverted CO2, allowing for a defined CO/H2 ratio between 1:1.4 and 1:10.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon dioxide is reduced to carbon monoxide in a carbon dioxide electrolysis cell using an aqueous electrolyte, then carbon monoxide production is achieved, but hydrogen is also formed due to water electrolysis and diffusion limitations, resulting in a 1:1:1 ratio of carbon monoxide to hydrogen to carbon dioxide
Solution Approach 1:
The patent divides the electrolysis system into two separate cells: a carbon dioxide electrolysis cell for CO production and a water electrolysis cell for H2 production. This segmentation allows independent control of each electrolysis process, preventing the unwanted co-production of hydrogen in the carbon dioxide electrolysis cell and enabling precise control over the CO/H2 ratio in the final synthesis gas.
Solution Approach 2:
The patent introduces a catholyte circulation system as an intermediary mechanism. The catholyte from the water electrolysis cell is circulated to the carbon dioxide electrolysis cell to absorb unreacted carbon dioxide, and then regenerated in a separate regeneration vessel. This intermediary system enables efficient CO2 removal without directly interfering with the electrolysis reactions, improving both conversion efficiency and product composition control.
2Adaptability or versatility
If a single electrolysis cell is used for carbon dioxide reduction, then the device complexity is low, but the ability to control the CO/H2 ratio in the product gas is limited
Solution Approach 1:
The patent employs multiple electrolysis cells (carbon dioxide electrolysis cell and water electrolysis cell) to enable independent control of CO and H2 production. This segmentation increases device complexity but provides the versatility to adjust the CO/H2 ratio according to different synthesis gas requirements, making the system adaptable to various applications.
Solution Approach 2:
The patent implements a dynamic catholyte circulation system where the flow rates and circulation patterns can be adjusted to control the amount of CO2 absorbed and the final CO/H2 ratio. This dynamic control mechanism allows the system to adapt to different product specifications while maintaining a manageable device complexity through standardized cell designs.
3Productivity
If carbon dioxide is not fully converted in the electrolysis cell, then the electrolysis process is simple, but the proportion of unconverted carbon dioxide in the product gas increases, reducing energy storage efficiency
Solution Approach 1:
The patent uses a catholyte circulation system as an intermediary to remove unconverted CO2. The catholyte absorbs CO2 from the product gas stream, and the saturated catholyte is then regenerated in a separate vessel where CO2 is released and the catholyte is reused. This intermediary approach efficiently removes unconverted CO2 without requiring complex direct purification methods, thereby improving energy storage efficiency.
Solution Approach 2:
The patent implements a regeneration system where the CO2-loaded catholyte is processed to release and recover the absorbed CO2. The regenerated catholyte is then returned to the carbon dioxide electrolysis cell for continued use. This discarding and recovering mechanism ensures high CO2 removal efficiency while maintaining system simplicity through reusable components.
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 enables the production of synthesis gas with a reduced CO2 content, enhancing energy storage efficiency and reducing greenhouse gas emissions by optimizing the CO/H2 ratio and increasing carbon dioxide conversion in the electrolysis process.
Implementation Method 1
The carbon dioxide is reduced to carbon monoxide at a cathode of the electrochemical cell
Implementation Method 2
water is oxidized to oxygen at an anode
Implementation Method 3
the first product gas (PG) is freed of non-reduced carbon dioxide (CO2) in the gas scrubbing apparatus (32) by means of the first catholyte (K1) and/or second catholyte (K2) as absorbent
Data Source
AI summary
Various embodiments may include a method of electrochemical production of synthesis gas comprising: reducing carbon dioxide to a first product gas including carbon monoxide in a carbon dioxide electrolysis cell; splitting water to generate a second product gas including hydrogen in a water electrolysis cell; delivering at least one catholyte from the group consisting of: a first catholyte from the carbon dioxide electrolysis cell and a second catholyte from the water electrolysis cell, into a gas scrubbing apparatus; and removing non-reduced carbon dioxide from the first product gas in the gas scrubbing apparatus using the at least one catholyte as an absorbent.