FCC Riser Spent Catalyst Recycle Conduit Design
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Solution Overview
Problem
The existing fluid catalytic cracking (FCC) processes require the use of a standpipe for spent catalyst recycle, which is cumbersome and necessitates additional equipment for controlling flow and thermal expansion.
Innovation Solution
A recycle conduit is disposed within the shell of the FCC riser, eliminating the need for a standpipe and associated equipment by directly recycling spent catalyst without regeneration back to the reaction zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standpipe is used for spent catalyst recycle, then catalyst flow rate can be controlled, but device complexity increases and additional equipment is required
Solution Approach 1:
The patent removes the standpipe from the system entirely, extracting the problematic equipment while maintaining the essential function of spent catalyst recycle. The recycle conduit is integrated directly into the riser structure, eliminating the need for separate standpipe components including slide valves, expansion joints, and hangers.
Solution Approach 2:
The patent merges the spent catalyst recycle function with the existing riser structure by integrating the recycle conduit within the riser shell. This consolidation combines multiple functions (catalyst transport, flow control, thermal management) into a single integrated structure, reducing overall device complexity.
2Productivity
If a standpipe is used for spent catalyst recycle, then catalyst transport is achieved, but additional equipment for thermal expansion and load absorption is required
Solution Approach 1:
The patent extracts and removes the thermal expansion compensation equipment (expansion joints, hangers) from the system by eliminating the standpipe structure. The integrated recycle conduit within the riser shell naturally accommodates thermal effects without requiring separate compensation mechanisms.
Solution Approach 2:
The recycle conduit serves multiple functions simultaneously: it transports spent catalyst, accommodates thermal expansion, absorbs mechanical loads, and controls flow rate. This multi-functionality eliminates the need for separate specialized equipment for each function.
3Device complexity
If spent catalyst is recycled without regeneration, then process simplicity is improved, but catalyst activity decreases
Solution Approach 1:
The patent applies partial regeneration by recycling spent catalyst that has undergone limited coke burning in the regenerator, rather than requiring complete regeneration. This partial action maintains sufficient catalyst activity while simplifying the overall process, avoiding the need for full regeneration cycles for all recycled catalyst.
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 solution simplifies the catalyst recycling process, reducing equipment needs and enhancing operational efficiency by allowing direct and efficient transport of spent catalyst within the riser, thereby optimizing the FCC process.
Implementation Method 1
Fluidization of the catalyst particles by various gaseous streams allows the transport of catalyst between the reaction zone and regeneration zone
Data Source
AI summary
Disclosed is an FCC apparatus and process in which spent catalyst is recycled to the base of the riser to contact fresh feed through a passage disposed within the riser.