Riser Insert for Catalyst Mixing
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Solution Overview
Problem
The existing processes for mixing carbonized and regenerated catalysts in fluid catalytic cracking (FCC) face challenges in achieving uniform temperature equilibrium, leading to non-selective cracking and increased capital costs due to large mixing chamber sizes and increased catalyst inventory requirements.
Innovation Solution
The use of an insert in the reactor riser to obstruct direct passage between catalyst conduits, facilitating thorough mixing of regenerated and carbonized catalyst streams while reducing catalyst volume and pressure drop, by feeding the streams around the insert and using vanes or dimples to enhance swirling and mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large mixing chamber is used to thoroughly mix carbonized and regenerated catalyst, then mixing effectiveness is improved, but capital cost and catalyst inventory requirements increase
Solution Approach 1:
The mixing chamber is segmented by inserting a vertical baffle plate that divides the chamber into two separate mixing zones. Each zone receives one catalyst stream (carbonized or regenerated) and promotes localized mixing before the streams combine, achieving thorough mixing without requiring a larger overall chamber volume
Solution Approach 2:
The baffle plate acts as an intermediary structure that facilitates interaction between the two catalyst streams. By obstructing direct passage and forcing the streams to mix around the baffle, it enables effective mixing while maintaining a compact chamber design
2Reliability
If catalyst streams are mixed without obstruction, then pressure drop is reduced, but mixing effectiveness decreases leading to temperature non-uniformity
Solution Approach 1:
The baffle plate creates localized high-mixing zones at its edges where the catalyst streams interact, while maintaining lower resistance in the central flow path. This localized approach achieves temperature uniformity where needed without creating excessive pressure drop across the entire chamber
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 ensures more uniform temperature distribution between the catalyst streams, reducing non-selective cracking and minimizing capital costs by optimizing catalyst mixing within the existing chamber size, thereby improving the efficiency and selectivity of hydrocarbon conversion.
Implementation Method 1
The insert in the riser between the first catalyst conduit and the second catalyst conduit obstructs direct passage between the first catalyst conduit and the second catalyst conduit
Implementation Method 2
The first stream of catalyst is passed around an insert in the riser to mix with the second stream of catalyst, and the second stream of catalyst is passed around the insert to mix with the first stream of catalyst
Data Source
AI summary
A process and apparatus for mixing streams of regenerated and carbonized catalyst involves passing a catalyst stream around an insert in a lower section of a riser. The insert fosters mixing of the catalyst streams to reduce their temperature differential before contacting hydrocarbon feed.