Compact Fuel Processing System for High-Purity Hydrogen Production
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Solution Overview
Problem
Existing fuel processing systems for hydrogen production face issues such as insufficient water vaporization leading to water-starved conditions, excessive carbon monoxide, and inefficient hydrogen separation, resulting in reduced efficiency and increased costs due to the need for large catalyst volumes and hydrogen loss in pressure swing adsorption systems.
Innovation Solution
A compact fuel processing system with an up-flow reformer tower and down-flow preferential CO oxidizer tower design, where water is introduced counterflow to the hydrogen-rich gas, ensuring complete vaporization and using loose catalyst pellets, and separating air into pure oxygen and nitrogen to reduce gas volume and eliminate nitrogen in the hydrogen stream, allowing for efficient production of high-pressure pure hydrogen, nitrogen, and carbon dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water is sprayed over inert packing in the reformer tower, then water is provided for the water/gas shift reaction, but insufficient residence time prevents complete vaporization and water may drain into the shift reactor damaging the catalyst
Solution Approach 1:
The patent introduces water at a location upstream where it receives maximum heat exposure from the hot reformate gas before entering the shift reactor. This preliminary heating action ensures water is fully vaporized and heated to reaction temperature before contacting the catalyst, preventing thermal shock and damage while maximizing conversion efficiency.
2Reliability
If less water is used to prevent catalyst damage, then catalyst protection is improved, but the conversion to hydrogen becomes water-starved leaving excess carbon monoxide
Solution Approach 1:
The patent uses two separate shift reactors in series - a high-temperature shift reactor followed by a low-temperature shift reactor. This duplicated approach allows the first reactor to handle the bulk conversion with sufficient water, while the second reactor performs final polishing to reduce CO to below 10 ppm, achieving both catalyst protection and high hydrogen conversion efficiency.
3Ease of operation
If pressure swing adsorption is used to separate hydrogen, then hydrogen separation is achieved, but hydrogen loss occurs during purges reducing efficiency
Solution Approach 1:
The patent separates air into nitrogen and oxygen components, using the nitrogen for purge operations and the oxygen for the reforming reactions. This recovery and reuse of nitrogen eliminates the need to discard hydrogen-rich gas during purge cycles, preventing hydrogen loss while maintaining effective system purging.
4Device complexity
If air is used as the oxidizer in the reformer, then the system is simpler, but nitrogen enters the hydrogen stream requiring separation
Solution Approach 1:
The patent extracts and separates the nitrogen component from air using pressure swing adsorption, removing it before the gas enters the reformer. This leaves pure oxygen to serve as the oxidizer in the reforming reaction, ensuring nitrogen-free hydrogen production while maintaining system simplicity through the use of standard air separation technology.
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 design enhances water utilization, reduces carbon monoxide levels, minimizes catalyst volume and costs, and avoids hydrogen waste, achieving efficient and compact production of hydrogen-containing reformate with less than 10 ppm CO and pure hydrogen, nitrogen, and carbon dioxide.
Implementation Method 1
water is introduced downwardly, in counterflow with the output of a generator of hydrogen-rich gas, thereby providing superior mix of the water and hydrogen/CO mixture; the up flow design results in complete vaporization of the water
Implementation Method 2
The up flow design results in complete vaporization of the water before reaching the water/gas shift reactors
Implementation Method 3
the water/gas shift reaction converts water and CO to CO2 and hydrogen
Implementation Method 4
down-flow packs of preferential carbon monoxide oxidizer catalyst
Implementation Method 5
preferential carbon monoxide oxidizer catalyst
Implementation Method 6
separating air into pure oxygen and nitrogen to reduce gas volume and eliminate nitrogen in the hydrogen stream
Implementation Method 7
a compressor to compress the reformate output to a high pressure
Data Source
AI summary
Substantially pure oxygen is provided to an up flow reformer (49a) from a separator (108) downwardly impelled water droplets (53) mix with the outflow (58) of a CPO (59), flowing upwardly through high temperature (68) and low temperature (73) water gas shift reactors. The reformer output flows through a mixer (79) to a down-flow PrOx containing two beds (82, 94) of preferential CO oxidation catalyst therein. A series of compressors (120-122) compress water and carbon dioxide out of the gaseous flow to provide pure, pressurized hydrogen. Oxygen (111) is separated (105, 108) from nitrogen (112).