Hydrogen Generator Shutdown Control to Prevent Catalyst Dew Condensation
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Solution Overview
Problem
Conventional hydrogen generation apparatuses face issues with catalyst degradation due to dew condensation during shutdown, particularly in the converting and selective oxidation units, which can reduce catalyst strength and activity over time.
Innovation Solution
A method for shutting down the hydrogen generation apparatus involves controlling the temperature of the reforming and converting units by using air as a heat transfer medium to maintain the converting unit's temperature above the dew point until the reforming unit reaches a predetermined temperature, thereby preventing dew condensation and catalyst degradation. This method includes setting specific temperature references and using heaters to assist in maintaining optimal temperatures during the shutdown process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If natural cooling is performed by standing for a certain time period without supplying water vapor during shutdown, then the reforming unit can be cooled down, but dew condensation occurs in the converting unit or selective oxidation unit causing catalyst degradation
Solution Approach 1:
The patent applies preliminary action by supplying water vapor to the converting unit and selective oxidation unit before the reforming unit is fully cooled down. This preliminary maintenance of temperature prevents dew condensation and catalyst degradation during the shutdown cooling process.
Solution Approach 2:
The patent maintains continuous protective action by keeping water vapor supply active during the cooling period. This continuous exposure to water vapor ensures the converting and selective oxidation units remain above dew point temperature throughout the shutdown process, preventing harmful condensation.
2Ease of operation
If the supply of raw material gas is stopped immediately after shutdown, then the shutdown process is simplified, but the reforming catalyst is exposed only to water vapor at high temperature causing catalyst degradation
Solution Approach 1:
The patent uses raw material gas as an intermediary substance during shutdown. Instead of stopping raw material supply immediately, it continues supplying raw material gas which serves as a protective atmosphere for the reforming catalyst, preventing direct exposure to water vapor at high temperatures during the critical cooling transition period.
3Reliability
If air is supplied to the converting unit during shutdown to prevent dew condensation, then catalyst degradation is prevented, but energy consumption increases
Solution Approach 1:
The patent applies self-service by utilizing the existing heat from the reforming unit during shutdown to maintain the converting unit temperature above dew point. Instead of requiring external energy input, the system uses its own thermal energy, and only supplements with water vapor supply when necessary, minimizing additional energy consumption while still protecting the catalyst.
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 proposed method effectively suppresses catalyst degradation by ensuring that the converting unit remains above the dew point until the reforming unit is cooled sufficiently, thereby extending the catalyst's lifespan and maintaining its activity over repeated startup and shutdown cycles.
Implementation Method 1
controlling the temperature of the reforming and converting units by using air as a heat transfer medium
Implementation Method 2
using heaters to assist in maintaining optimal temperatures during the shutdown process
Implementation Method 3
dew condensation occurring in the converting unit or the selective oxidation unit
Data Source
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AI summary
A hydrogen generation apparatus for limiting degradation in a catalyst due to dew condensation at the time of shutdown is provided. The hydrogen generation apparatus has a raw material supplier which supplies a raw material, a water supplier which supplies water, a reforming device having a reforming catalyst for generating a gas containing hydrogen by reforming reaction using the raw material and water, a CO reducing device having a CO reducing catalyst for reducing carbon monoxide in the gas containing hydrogen delivered from the reforming device, a combustor which supplies heat necessary for the reforming reaction to the reforming device, a first air supplier which supplies air for combustion to the combustor, a combustion exhaust gas path formed such that the combustion exhaust gas produced in the combustor makes heat exchange with the reforming device and then with the CO reducing device, and a controller which operates the first air supplier so that the temperature of the gas in the CO reducing device does not become equal to or lower than a dew point after shutdown of the combustion operation of the combustor and before a start of a purging operation to purge the interiors of the reforming device and the CO reducing device with a replacement gas.