Reforming Exchanger System with Intermediate Shift Reactor
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Solution Overview
Problem
Reforming exchangers face limitations due to metal dusting issues caused by carbon monoxide corrosion, which restricts operating temperatures and pressures and reduces high-grade waste heat recovery, necessitating improved systems to minimize metal dusting.
Innovation Solution
A reforming exchanger system with two exchangers in series and an intermediate shift reactor to convert carbon monoxide to carbon dioxide, reducing the critical Boudouard reaction temperature and allowing further cooling without increasing metal dusting risks, thereby enhancing heat recovery and operational flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shell side outlet gas temperature is increased to minimize metal dusting, then metal dusting is reduced, but high grade waste heat recovery is limited
Solution Approach 1:
The system divides the reforming process into multiple stages by using multiple reforming exchangers in series with an intermediate shift reactor. This segmentation allows different sections of the system to operate at different temperatures and CO concentrations, enabling both metal dusting prevention and heat recovery optimization
Solution Approach 2:
An intermediate shift reactor is introduced between the first and second reforming exchangers to convert CO to CO2. This intermediary device reduces the CO concentration in the gas stream, which lowers the critical temperature for metal dusting and allows the second exchanger to operate at lower temperatures with reduced metal dusting risk
2Reliability
If the mixed feed to the tube side is pre-heated to address metal dusting, then metal dusting is reduced, but duty on external heat source increases
Solution Approach 1:
The system uses the hot reformed gas from the first exchanger to pre-heat the mixed feed in the second exchanger through indirect heat exchange. This self-service approach allows the process to heat the feed using its own hot streams, reducing or eliminating the need for external heat sources while maintaining temperatures that prevent metal dusting
3Reliability
If CO concentration is reduced to minimize metal dusting, then metal dusting is reduced, but reforming reaction efficiency decreases
Solution Approach 1:
The system maintains continuous reforming reactions across multiple exchangers in series. While the intermediate shift reactor reduces CO concentration to prevent metal dusting, the reforming reactions continue uninterrupted in both the first and second exchangers, ensuring continuous syngas production
Solution Approach 2:
The system changes the chemical composition parameters by introducing the shift reaction (CO + H2O → CO2 + H2) at the intermediate stage. This parameter change reduces CO concentration to prevent metal dusting while the overall system maintains high productivity through multiple reforming zones operating at optimized conditions
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 system effectively reduces carbon monoxide concentration, allowing for increased heat recovery and broader operational envelopes by reducing metal dusting risks, while also promoting more reforming reactions through favorable heat transfer conditions.
Implementation Method 1
passing the first gas mixture through a shift catalyst bed contained within the shift reactor to selectively convert carbon monoxide in the first gas mixture to carbon dioxide
Implementation Method 2
catalytic reforming reaction that occurs in the autothermal reformer, which is endotheiniic, to produce a relatively hot reformed gas
Implementation Method 3
The hot reformed gas from the autothermal reformer is then used as a heat source in the reforming exchanger, which is operated as an endothermic catalytic steam reforming zone
Implementation Method 4
One popular technique is to use an autothermal reformer in conjunction with a reforming exchanger. In such processes, one or more hydrocarbons and an oxygen source are supplied to the autothermal reformer. The combustion reaction is exothermic and supplies the heat needed for the catalytic reforming reaction
Implementation Method 5
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 to occur
Implementation Method 6
the chemical equilibrium temperature for the Boudouard reaction: 2CO(g)←→CO2(g)+C(s)
Data Source
AI summary
A reforming exchanger system for syngas production is provided. The reforming exchanger system can have a first and a second reforming exchanger, each with a shell-and-tube configuration, and a shift reactor located intermediate to the first and second reforming exchangers to reduce carbon monoxide concentration in the outlet gas. Processes for forming syngas using the reforming exchanger systems described herein are also provided.