Catalyst Mixing Riser with Downward and Horizontal Streams
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Solution Overview
Problem
Existing processes for mixing carbonized and regenerated catalysts in fluid catalytic cracking (FCC) units face challenges in achieving thorough mixing, leading to uneven catalyst temperatures and non-selective cracking, which affects the quality of product hydrocarbons.
Innovation Solution
The process involves feeding a first catalyst stream downwardly and a second catalyst stream horizontally into a riser, with specific angular trajectories and elevations, to facilitate thorough mixing by utilizing the momentum and gravity, thereby reducing the overall height requirements of the mixing chamber and improving temperature uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large mixing chamber is used to ensure thorough mixing of catalyst streams, then mixing quality is improved, but capital cost and catalyst inventory requirements increase
Solution Approach 1:
The mixing chamber is segmented into distinct zones: an upper zone where the first catalyst stream enters downwardly and a lower zone where the second catalyst stream enters horizontally. This segmentation allows thorough mixing to occur in a more compact volume by creating localized mixing regions rather than requiring a uniformly large chamber throughout.
Solution Approach 2:
The patent introduces angular trajectory control as an additional dimension for mixing. By specifying that catalyst streams enter at particular angles (downwardly for the first stream, horizontally for the second stream), the invention utilizes directional components to enhance mixing efficiency within a reduced chamber volume, transforming a purely volumetric approach into a spatial-vectorial approach.
2Temperature
If catalyst streams are fed at different angles and elevations to improve mixing, then temperature uniformity is improved, but device complexity increases
Solution Approach 1:
Different regions of the mixing chamber are assigned different functions based on local catalyst entry characteristics. The upper region handles the downwardly fed first catalyst stream while the lower region handles the horizontally fed second catalyst stream. This local differentiation of entry conditions creates optimal mixing and temperature uniformity in each zone without requiring complex overall device design.
Solution Approach 2:
Instead of feeding both catalyst streams horizontally or vertically as in conventional designs, the patent inverts the approach by feeding one stream downwardly and the other horizontally. This inverted configuration allows the streams to intersect and mix more effectively, improving temperature uniformity while maintaining relatively simple conduit geometry.
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 catalyst temperatures, reducing the formation of undesirable products and enhancing the efficiency of the cracking process by ensuring thorough mixing of the catalyst streams before contacting the hydrocarbon feed.
Implementation Method 1
feeding a first catalyst stream downwardly to the riser
Implementation Method 2
feeding a first catalyst stream downwardly to the riser while feeding a second catalyst stream horizontally to the riser fosters thorough mixing
Data Source
AI summary
A process and apparatus for mixing streams of regenerated and carbonized catalyst utilizes a ramp or bend provided on only one of the catalyst conduits to provide mixing advantages.