Fuel Cell Desulfurization Shutdown Gas Management
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Solution Overview
Problem
During shutdown of a fuel cell unit, noxious gases like methane can be desorbed from the desulfurization unit and cause coking of the reformer and fuel cell units if not properly managed, especially when insufficient water is supplied to the reformer unit.
Innovation Solution
Incorporating an outlet valve to close the flow between the desulfurization and reformer units, and a drain valve to redirect noxious gases away from the fuel cell unit during shutdown, along with using parallel desulfurization reactors to alternate desulfurization duties and reduce the risk of noxious gas transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the desulfurization unit operates during shutdown, then sulfur compounds are removed from the fuel, but noxious gases like methane are desorbed and transferred to the reformer unit causing coking
Solution Approach 1:
The system is divided into separate functional zones: the desulfurization unit with its own combustion chamber is segmented from the reformer unit. This segmentation allows the desulfurization unit to handle noxious gases independently through controlled combustion, preventing their transfer to the reformer unit and avoiding coking while maintaining desulfurization functionality.
2Use of energy by moving object
If water supply to the reformer unit is reduced during shutdown, then energy consumption is lowered, but noxious gases cause coking due to insufficient steam reforming
Solution Approach 1:
The harmful function of noxious gas transfer is extracted and contained within the desulfurization unit. The combustion chamber located within the desulfurization unit combusts noxious gases like methane locally, extracting the harmful effect from the overall system and preventing it from reaching the reformer unit, thereby avoiding coking even when water supply is reduced.
3Object-affected harmful factors
If the outlet valve is closed during shutdown, then noxious gas transfer to the reformer unit is prevented, but pressure builds up in the desulfurization unit
Solution Approach 1:
The previously harmful noxious gases (methane) are converted into a beneficial heat source through controlled combustion in the combustion chamber. This combustion process generates heat that maintains temperatures sufficient to prevent condensation and coking in the reformer unit, while the combustion itself consumes the noxious gases, eliminating the need for complex pressure management 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
This solution effectively prevents or reduces coking of the reformer and fuel cell units by limiting the transfer of noxious gases during shutdown, enhancing the operational safety and longevity of the fuel cell device.
Implementation Method 1
During a normal operation of the fuel cell unit materials of the desulfurization unit may absorb methane
Implementation Method 2
When shutting down the fuel cell unit, e.g. in case of an emergency shutdown, the absorbed methane may be desorbed
Implementation Method 3
the reformer unit is embodied as a steam reformer unit... provided to process the fuel by addition of water vapor for generating the fuel gas containing gas mixture
Implementation Method 4
The water supply unit comprises at least one vaporizer, which is fluidically arranged upstream of the reformer unit and which is provided for vaporizing the supplied water
Data Source
Figure 1
Figure 2
AI summary
The invention is based on a fuel cell device, which is provided to be operated with a fluidic fuel, with a desulfurization unit (12a; 12b), which is provided to desulfurize the fuel at least partially, with a reformer unit (14a; 14b), which is provided for generating at least one fuel gas, and with a fuel cell unit (16a; 16b). It is proposed that the desulfurization unit (12a; 12b) is provided for at least limiting a transfer of at least one noxious gas from the desulfurization unit (12a; 12b) into the reformer unit (14a; 14b) and/or into the fuel cell unit (16a; 16b) at least when shutting down the fuel cell unit (16a; 16b).