Co-current Coolant Flow in Ethane ODH Reactors
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Solution Overview
Problem
In oxidative dehydrogenation of ethane processes, the formation of 'hot-spots' in multitubular fixed-bed reactors poses a risk of reactor runaway, and existing solutions to mitigate this, such as reducing tube diameter or operating at lower productivity, are costly and inefficient.
Innovation Solution
Supplying coolant to the reactor's interior shell space in a co-current flow pattern at a low enough rate to allow a 5°C to 30°C temperature increase, thereby minimizing hot-spots without reducing tube diameter or increasing length, and maintaining isothermal conditions on the process side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tube diameter is reduced to increase heat transfer rate, then hot-spot formation is reduced, but reactor construction cost increases and catalyst loading time increases
Solution Approach 1:
The patent changes the coolant flow pattern parameter from conventional counter-current to co-current flow, and optimizes the coolant flow rate to achieve uniform temperature distribution without modifying tube dimensions or reactor structure
Solution Approach 2:
The patent adopts the coolant flow pattern configuration from WO 2001/85333, applying the co-current flow arrangement to achieve thermal management in the oxidative dehydrogenation reactor
2Temperature
If tube length is increased to improve heat transfer, then hot-spot formation is reduced, but pressure drop across the reactor increases
Solution Approach 1:
The patent changes the coolant flow rate parameter to optimize heat transfer efficiency, achieving uniform temperature distribution without increasing tube length or accepting higher pressure drops
3Reliability
If productivity is reduced to avoid hot-spots, then reactor runaway risk is reduced, but ethylene yield decreases
Solution Approach 1:
The patent implements thermal feedback control through co-current coolant flow, where the coolant temperature adjusts automatically along the reactor length to match the exothermic reaction profile, maintaining safe operating conditions at high productivity
Solution Approach 2:
The patent optimizes the coolant flow rate parameter to achieve the optimal balance between heat removal efficiency and productivity, allowing high ethylene yield while preventing hot-spot formation
4Temperature
If catalyst is diluted with inert substance to operate at lower productivity, then hot-spot formation is reduced, but cost increases and catalyst recovery becomes more difficult
Solution Approach 1:
The patent changes the coolant flow rate parameter to control temperature uniformity, eliminating the need for catalyst dilution and maintaining high catalyst concentration for efficient and economical operation
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 effectively prevents or minimizes the risk of reactor runaway while maintaining high productivity, without increasing costs or complicating catalyst recovery, by ensuring a controlled temperature profile throughout the catalyst bed.
Implementation Method 1
a shell in which the tubes are contained through which coolant circulates to facilitate the removal of the reaction heat
Implementation Method 2
the undesirable combustion reactions of ethane and ethylene, both of which are highly exothermic and generate carbon dioxide and/or carbon monoxide
Data Source
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AI summary
Processes and associated reaction systems for the oxidative dehydrogenation of ethane are provided. In particular, a process is provided that comprises supplying a feed gas comprising ethane and oxygen to a multitubular fixed-bed reactor and allowing the ethane and oxygen to react in the presence of an oxidative dehydrogenation catalyst to yield a reactor effluent comprising ethylene; and supplying a coolant to an interior shell space of the multitubular fixed- bed reactor in a flow pattern that is co-current with the flow of the feed gas through reactor.