Fluidized Bed Reactor Heat Management for Olefin Production
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Solution Overview
Problem
The existing methods for producing olefins from light alkanes face challenges in providing reliable and efficient reaction heat and maintaining uniform catalyst bed temperatures, leading to suboptimal production rates and catalyst deactivation due to excessive heating and coke formation.
Innovation Solution
A process using fluidized bed reactors partially embedded in a furnace, where the outside walls are heated by a flue gas generated from combustion, maintaining catalyst bed temperatures between 500° C. and 700° C., and switching reactors between production and regeneration modes to manage coke formation and catalyst activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If light alkane feedstock is preheated to provide sufficient sensible heat for the endothermic reaction, then reaction heat requirement is met, but thermal breakdown of feedstock occurs and catalyst deactivation accelerates
Solution Approach 1:
The patent applies preliminary action by preheating the feedstock to a moderate temperature (e.g., 200-400°C) before entering the reactor, but then immediately supplies additional reaction heat through the catalyst bed itself via controlled combustion of a portion of the feedstock or injected fuel. This two-stage approach provides the necessary reaction heat without subjecting the feedstock to excessive temperatures that would cause thermal breakdown and catalyst deactivation.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a separate heating zone or injected fuel/air mixture that burns within or near the catalyst bed to provide reaction heat. This intermediary heat source supplies the required thermal energy directly to the reaction zone without requiring the feedstock to be preheated to excessively high temperatures, thereby avoiding thermal breakdown while meeting the endothermic reaction heat requirement.
2Productivity
If catalyst bed temperature is increased above 700° C. to improve conversion rate, then light alkane conversion rate increases, but catalyst deactivation occurs too fast
Solution Approach 1:
The patent applies parameter changes by precisely controlling the catalyst bed temperature within an optimized range (500-700°C) through regulated combustion of injected fuel or partial feedstock oxidation. This temperature control maintains high conversion rates while preventing excessive temperatures that would cause rapid catalyst deactivation, thus extending catalyst lifetime while preserving productivity.
Solution Approach 2:
The patent implements periodic action by cyclically regenerating the catalyst in separate regeneration zones where coke is burned off, then redistributing the regenerated catalyst back to the reaction zones. This periodic regeneration cycle maintains catalyst activity over extended periods, effectively extending the operational duration of the catalyst system while maintaining high conversion rates during production phases.
3Use of energy by stationary object
If external heating of fixed bed reactor surfaces is applied to supply reaction heat, then thermal energy is supplied, but non-uniform temperature distribution occurs in catalyst bed
Solution Approach 1:
The patent extracts the heating function from the external reactor walls and relocates it to the interior of the catalyst bed by injecting fuel and air that combust directly within the catalyst particles or in channels through the bed. This internal combustion approach distributes heat generation throughout the catalyst bed volume, eliminating the non-uniform temperature distribution that occurs with external surface heating and ensuring uniform thermal conditions for optimal catalyst performance.
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 enables continuous, commercially attractive olefin production by ensuring uniform heat distribution and extending catalyst life, while avoiding concurrent olefin production and catalyst regeneration in the same furnace, thus achieving high production rates and maintaining process efficiency.
Implementation Method 1
the outside walls are heated by a flue gas generated from combustion
Implementation Method 2
the outside walls are heated by a flue gas generated from combustion
Implementation Method 3
A process using fluidized bed reactors partially embedded in a furnace
Implementation Method 4
contacting a light alkane feed with dehydrogenation catalyst particles
Implementation Method 5
Light alkane dehydrogenation is an equilibrium-limited and highly endothermic reaction
Data Source
AI summary
A process and an apparatus for producing olefins from light alkanes. A light alkane feed is contacted with catalyst particles in each of reactors, wherein each of the reactors is a fluidized bed reactor. At least a portion of the alkane feed is converted to olefins using the catalyst particles, wherein the olefins form a part of a reactor effluent stream. The reactor effluent streams from each of the reactors are merged to form a merged effluent stream. The merged effluent stream is separated into an olefin stream and the other streams. The other streams may comprise a recycle stream and light gases.