Hydrogen Generator Start-Up Control for Catalyst Protection
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Solution Overview
Problem
Existing hydrogen generators face challenges in achieving stable start-up due to frequent ignition of the burner, leading to CO emissions and catalyst degradation from water leakage and carbon deposition, which affects the durability and performance of the reforming and CO removing catalyst layers.
Innovation Solution
A hydrogen generator configuration with a controller that manages the heating of the CO removing catalyst layer and reforming catalyst layer, using specified temperature thresholds to prevent steam condensation and carbon deposition, ensuring stable start-up by controlling the water supply and burner operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the burner is frequently ignited to heat the catalyst during start-up, then the catalyst temperature rises to prevent steam condensation and carbon deposition, but CO emissions increase and the system stability deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-heating the catalyst using an auxiliary heater before starting the burner. This ensures the catalyst reaches a temperature above the dew point of steam before material gas is supplied, preventing steam condensation and carbon deposition during the critical start-up phase. The auxiliary heater is activated in advance to prepare the catalyst bed, eliminating the need for frequent burner ignition and associated CO emissions.
2Productivity
If steam is supplied to the catalyst at insufficient temperature, then the steam reforming reaction can proceed, but steam condenses and causes water leakage that degrades the catalyst
Solution Approach 1:
The system performs preliminary heating of the catalyst to a temperature above the steam dew point before introducing steam-containing material gas. This preliminary action ensures that when steam is supplied for the reforming reaction, the catalyst is already at sufficient temperature to vaporize any condensed steam, preventing water leakage and catalyst degradation while maintaining reaction efficiency.
Solution Approach 2:
The patent employs feedback control by monitoring the catalyst temperature and adjusting the auxiliary heater and burner operation accordingly. When the catalyst temperature approaches the steam dew point, the system activates heating measures to prevent condensation. This feedback mechanism ensures the catalyst temperature remains in the optimal range for steam reforming while preventing water-related degradation.
3Productivity
If material gas is supplied alone at high temperature, then the reforming reaction can occur, but carbon deposition occurs on the catalyst and structural elements
Solution Approach 1:
The system supplies water vapor to the catalyst in advance before supplying material gas alone. This preliminary action of introducing steam creates a protective atmosphere that prevents thermal decomposition of hydrocarbons and subsequent carbon deposition on the catalyst and structural elements. The steam acts as a carrier gas that maintains the reducing atmosphere necessary for reforming while preventing coking.
Solution Approach 2:
The patent converts the potentially harmful effect of high-temperature material gas into a beneficial process by introducing water vapor that prevents carbon deposition. The steam, which could otherwise cause water leakage at low temperatures, becomes protective at high temperatures by preventing hydrocarbon decomposition and carbon formation on the catalyst surface and structural elements.
4Reliability
If the catalyst temperature is raised excessively to prevent steam condensation, then water leakage is prevented, but carbon deposition occurs due to thermal decomposition of material gas
Solution Approach 1:
The system uses feedback control to monitor catalyst temperature and adjust heating and gas supply accordingly. When the temperature reaches a level sufficient to prevent steam condensation but below the threshold for significant carbon deposition, the system maintains this optimal range. The feedback mechanism detects temperature changes and adjusts the auxiliary heater and material gas flow to keep the catalyst in the safe operating window, preventing both water leakage and carbon deposition.
Solution Approach 2:
The patent changes the composition and flow rate parameters of the gas phase by introducing water vapor in controlled amounts. This parameter change allows the system to operate at lower temperatures that prevent carbon deposition while still maintaining sufficient temperature to avoid steam condensation. The water vapor content in the gas phase is adjusted as a control parameter to balance between preventing water leakage and avoiding thermal decomposition.
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 inhibits water leakage and carbon deposition, enhancing the durability and stability of the catalyst layers during start-up, reducing the need for frequent burner ignition and maintaining catalyst performance.
Implementation Method 1
a CO removing heater (7) for heating the CO removing catalyst layer (2)
Implementation Method 2
a burner (3) for heating the reforming catalyst layer (1)
Implementation Method 3
a steam reforming reaction in the presence of a catalyst. In the steam reforming reaction, the material gas and steam are made to react with each other on a reforming catalyst having a high temperature
Implementation Method 4
the amount of carbon monoxide is reduced to 10 ppm or less, for example, through a shift reaction in the presence of a shift reaction catalyst
Implementation Method 5
a selective oxidation reaction that is carried out subsequently to mixing with oxygen, utilizing a selective oxidation catalyst
Implementation Method 6
if steam is supplied to the catalyst when the temperature of the catalyst is not sufficiently high, the steam will be cooled and condensed by the catalyst
Implementation Method 7
the water, which has infiltrated into the catalyst, generates a great power within the catalyst owing to its rapid volumetric expansion when it evaporates within the catalyst
Implementation Method 8
carbon deposition could occur on the catalyst, inside the catalyst and on the structural elements of the hydrogen generator surrounding the catalyst, if the material gas, which is a carbon-containing hydrocarbon substance, is supplied alone when the catalyst and the structural elements are at high temperatures
Data Source
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AI summary
A hydrogen generator is described, which comprises: a material supply device (4); a water supply device (5); an evaporator (10); a reforming catalyst layer (1) for generating reformed gas; a CO removing catalyst layer (2) configured to reduce the amount of carbon monoxide contained in the reformed gas generated by the reforming catalyst layer (1); a combustor (3) for heating the reforming catalyst layer (1) and the CO removing catalyst layer (2); a reforming temperature detector (9) for detecting the temperature of the reforming catalyst layer (1); a heater (7) for heating the CO removing catalyst layer (2); a CO removing temperature detector (8) for detecting the temperature of the CO removing catalyst layer (2); and a controller (16) configured to perform control such that the heater (7) heats the CO removing catalyst layer at the time of start-up and such that if the temperature detected by the CO removing temperature detector (8) becomes greater than or equal to a first specified value, the combustor (3) heats the reforming catalyst layer (1) and the CO removing catalyst layer (2), and if the temperature detected by the reforming temperature detector (9) becomes greater than or equal to a second specified value, the water supply device (5) starts supplying of water.