Shell-Side Shift Catalyst for Reforming Exchanger Metal Dusting
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Solution Overview
Problem
Reforming exchangers face limitations due to metal dusting, where carbon monoxide corrodes metal surfaces, leading to inefficient operation and restricted operating conditions, limiting high-grade waste heat recovery and heat integration opportunities.
Innovation Solution
Incorporating a shift catalyst bed on the shell side of the reforming exchanger to convert carbon monoxide to carbon dioxide, reducing the risk of metal dusting and allowing for wider operating conditions by decreasing the critical Boudouard reaction equilibrium temperature, thereby enhancing heat recovery and reducing the need for pre-heating the feed gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shell side outlet gas temperature is maintained sufficiently high to prevent metal dusting, then metal surfaces are protected from corrosion, but high-grade waste heat recovery is limited
Solution Approach 1:
The harmful component (carbon monoxide) is extracted from the gas mixture by passing it through a shift catalyst bed, where CO is converted to CO2. This removal of CO eliminates the cause of metal dusting, allowing the outlet temperature to be reduced for better heat recovery without compromising metal surface integrity.
Solution Approach 2:
The harmful carbon monoxide that causes metal dusting is converted into beneficial carbon dioxide through the shift reaction. This transformation turns a problematic substance into a harmless product, enabling lower outlet temperatures and improved heat recovery while maintaining metal surface protection.
2Reliability
If the shell side outlet gas temperature is maintained sufficiently high to prevent metal dusting, then metal surfaces are protected from corrosion, but the operating envelope is restricted to higher temperatures and pressures
Solution Approach 1:
By extracting carbon monoxide through the shift catalyst bed, the patent eliminates the primary constraint on operating conditions. This allows the exchanger to operate at lower temperatures and broader pressure ranges without risking metal dusting, thereby expanding the usable operating envelope.
3Reliability
If feed gas is pre-heated to address metal dusting concerns, then metal surfaces are protected, but duty on external heat source increases
Solution Approach 1:
The shift reaction converts harmful CO into CO2 while generating heat that can be used to preheat the feed gas internally. This eliminates or reduces the need for external pre-heating, maintaining metal surface protection while decreasing external energy requirements.
4Reliability
If feed gas is pre-heated to address metal dusting concerns, then metal surfaces are protected, but heat integration opportunities are limited
Solution Approach 1:
The shift catalyst bed is integrated directly into the exchanger shell side, combining the CO conversion function with the heat exchange function. This internal integration allows heat from the CO2-rich outlet stream to preheat the feed gas, creating heat integration opportunities without adding external pre-heating equipment.
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 solution effectively reduces carbon monoxide concentration in the outlet gas, preventing metal dusting, allowing for increased heat recovery and expanding the operating envelope of the exchanger to include previously undesirable pressures and temperatures, while also reducing costs by enabling the use of thinner metals and optimizing heat transfer conditions.
Implementation Method 1
one or more shift catalysts for converting carbon monoxide to carbon dioxide in the gas mixture
Implementation Method 2
endothermically reformed gas through open-ended tubes filled with reforming catalyst
Implementation Method 3
The hot gas mixture is then passed through the shell countercurrently across or along the tubes in indirect heat exchange to supply the heat necessary for the endothermic reforming reaction
Data Source
AI summary
Reforming exchangers for syngas production are provided. The reforming exchangers can have a shell-and-tube configuration and include a shift catalyst on the shell side of the exchanger to reduce a carbon monoxide concentration in a shell side product gas mixture. Processes for forming syngas using the reforming exchangers are also provided.