Fuel Cell Tail Gas Decarbonization for Hydrocarbon Cracking
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Solution Overview
Problem
Hydrocarbon cracking systems face challenges in reducing carbon emissions due to the presence of hydrogen in tail gases, which complicates carbon capture techniques and increases carbon dioxide concentrations in flue gases.
Innovation Solution
A process involving the separation of cracking product streams into hydrogen-rich methane and other streams, followed by the use of a fuel cell with an anode and cathode separated by a solid oxide or molten carbonate element to convert methane and hydrogen into carbon dioxide and water, generating electricity and shifting carbon capture focus to the tail gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If carbon capture process is applied to flue gas from hydrocarbon cracking furnace, then carbon dioxide concentration is reduced, but the presence of hydrogen in tail gases complicates the carbon capture technique and increases carbon dioxide concentration in flue gases
Solution Approach 1:
The patent extracts hydrogen from the tail gas stream using a separator before the fuel cell. This removes the complicating factor (hydrogen) from the carbon capture process, allowing simpler carbon dioxide separation techniques to be applied to the remaining flue gas without the interference of hydrogen combustion products.
Solution Approach 2:
The patent segments the flue gas treatment into two distinct stages: first separating hydrogen-rich streams using a separator, then applying carbon capture techniques to the remaining gas. This segmentation simplifies each individual process step compared to treating the mixed stream as a whole.
2Object-generated harmful factors
If fuel cell is used to convert methane and hydrogen to electricity, then carbon dioxide emissions are reduced, but additional equipment (separator, fuel cell) is added to the system
Solution Approach 1:
The patent converts the harmful components (methane and hydrogen in tail gas) into useful electricity through the fuel cell. The methane and hydrogen that would otherwise be wasted or require complex treatment are transformed into a beneficial energy source, powering the system while reducing carbon dioxide emissions.
Solution Approach 2:
The fuel cell system generates electricity that can be used to power the hydrocarbon cracking system itself, making the system partially self-sufficient. The waste gases from the cracking process provide fuel for the fuel cell, which in turn provides power for the overall system operation.
3Productivity
If hydrogen-rich methane stream is separated and processed, then carbon capture efficiency is improved, but the separation process requires additional equipment and operational steps
Solution Approach 1:
The separator performs multiple functions: it separates hydrogen-rich methane from other cracking products, prepares the fuel stream for the fuel cell, and facilitates subsequent carbon capture operations. This multi-functionality justifies the addition of separation equipment by providing several benefits from a single unit.
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 reduces carbon dioxide emissions by capturing CO2 from the tail gas, generates electricity for system use, and avoids nitrogen-related issues, thereby improving the sustainability and efficiency of carbon capture in hydrocarbon cracking systems.
Implementation Method 1
converting, at the anode of the fuel cell, methane and hydrogen received from the hydrogen-rich methane stream or from the methane product stream to carbon dioxide and water to generate electricity
Implementation Method 2
a separating element (e.g., a solid oxide element or a molten carbonate element) positioned between the anode and the cathode
Data Source
AI summary
Processes and systems that utilize a fuel cell for carbon capture from a petrochemical stream that contains hydrogen and methane. The petrochemical stream can be the tail gas of a hydrocarbon cracking system, or any other petrochemical stream containing hydrogen and methane. The petrochemical stream can be separated into a hydrogen product stream and a methane product stream, before sending the methane product stream to the fuel cell. The fuel cell converts methane to carbon dioxide and hydrogen to water, while generating electricity that can be used to power equipment.