CO Shift Conversion Device with Membrane-Based CO2 Removal
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Solution Overview
Problem
The existing CO shift conversion processes require a large amount of catalyst and are inhibited by chemical equilibrium, leading to low CO conversion rates and increased start-up time, particularly in fuel cell systems, due to catalyst poisoning by CO2.
Innovation Solution
A CO shift conversion device and method that preliminary lowers CO2 concentration using a membrane-based CO2 removing unit, followed by a catalyst layer with a copper-zinc-based catalyst, which improves CO conversion rates by mitigating CO2 poisoning effects, allowing for multiple stages of catalyst layers to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large amount of shift conversion catalyst is used to sufficiently lower CO concentration, then CO conversion rate improves, but heating time increases and start-up time is extended
Solution Approach 1:
The patent applies preliminary action by removing CO2 from the reformed gas before it enters the shift conversion catalyst. This preliminary CO2 removal prevents catalyst poisoning before it occurs, allowing the catalyst to maintain high activity throughout operation. The CO2 removal unit is positioned upstream of the shift conversion catalyst, performing the harmful CO2 removal action in advance, which eliminates the need for excessive catalyst quantity and reduces heating time.
2Productivity
If the reaction temperature is lowered to favor equilibrium toward products, then CO concentration decreases, but reaction rate decreases
Solution Approach 1:
The patent applies parameter changes by removing CO2 from the gas composition before the shift conversion reaction. This changes the equilibrium parameters of the reaction system. By reducing CO2 concentration, the equilibrium shifts toward products according to Le Chatelier's principle, improving CO conversion rate without requiring low temperature operation. This allows the reaction to proceed at higher temperatures with both fast reaction rate and high conversion.
3Productivity
If CO2 concentration in the gas is high, then chemical equilibrium restricts shift conversion reaction progress, but removing CO2 requires additional equipment and complexity
Solution Approach 1:
The patent introduces a CO2 removal unit as an intermediary component between the reformed gas source and the shift conversion catalyst. This intermediary removes the harmful CO2 substance before it can poison the catalyst or restrict equilibrium progress. The CO2 removal unit acts as a mediator that prepares the gas stream for optimal shift conversion operation, preventing catalyst deactivation without requiring complex multi-stage catalyst systems.
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
The method significantly improves CO conversion rates without increasing catalyst usage, producing hydrogen gas with reduced CO concentrations suitable for fuel cells, by addressing CO2 poisoning and optimizing catalyst performance across multiple stages.
Implementation Method 1
a CO2 removing unit removing CO2 contained in a gas introduced and transmitting a processed gas whose CO2 concentration is lower than that of the introduced gas to a downstream side, the CO2 removing unit being formed of a membrane which selectively passes CO2
Implementation Method 2
the catalyst layer is composed of a CO shift conversion catalyst having a property that a CO conversion rate decreases with an increase of the concentration of CO2 contained in the gas flowing inside due to a CO2 poisoning action and the CO shift conversion catalyst includes a copper-zinc-based catalyst
Implementation Method 3
CO and water vapor (H2O) contained in a mixed gas (in this case, reformed gas) are reacted, and thereby converted to CO2 and hydrogen (H2)
Data Source
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AI summary
The present invention provides a CO shift conversion device and a CO shift conversion method which improves CO conversion rate without increasing usage of a shift conversion catalyst. A CO shift conversion device includes: a CO shift converter 10 having a catalyst layer 5 composed of a CO shift conversion catalyst and performing CO shift conversion process on a gas flowing inside; and a CO2 remover 51 removing CO2 contained in a gas introduced. The catalyst layer 5 is composed of a CO shift conversion catalyst having a property that a CO conversion rate decreases with an increase of the concentration of CO2 contained in a gas flowing inside. The concentration of CO2 contained in a gas G0 to be processed is lowered by the CO2 remover 51 and, after that, the resultant gas is supplied to the CO shift converter 10 where it is subjected to the CO shift conversion process.