Three-Zone VSS Stripper for Reducing Riser Underflow
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Solution Overview
Problem
Current high containment reactor systems suffer from significant underflow of reactor riser products into the stripper and reactor vessel, leading to undesirable secondary catalytic cracking, reduced product selectivity, and inefficient stripping due to high backmixing and coke formation, with previous cold flow modeling not accounting for the impact of 'soft coke' reactions.
Innovation Solution
Engineering design modifications to the vortex separation system (VSS) exit, stripper entrance, and primary cyclone diplegs, including a three-zone stripper configuration that reduces fluidized bed freeboard activity and superficial velocity, along with independent control of space velocity and catalyst transport rates, to minimize underflow and enhance stripping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a conventional high containment reactor system is used, then product containment is maintained, but significant underflow of reactor riser products occurs into the stripper and reactor vessel
Solution Approach 1:
The stripper is divided into three distinct zones: a first stripping zone with high catalyst inventory and low gas velocity for initial stripping of underflow products, a second stripping zone for intermediate stripping, and a third stripping zone for final stripping. This segmentation allows each zone to perform a specific function, effectively reducing overall underflow while maintaining product containment.
Solution Approach 2:
Different regions of the stripping system are given different properties: the first stripping zone has high catalyst inventory and low gas velocity optimized for capturing underflow products, while upper zones have progressively lower catalyst inventory and higher gas velocities for subsequent stripping stages. This local differentiation optimizes each zone for its specific purpose.
2Productivity
If high backmixing occurs in the stripper, then stripping efficiency is reduced, but product selectivity deteriorates due to secondary catalytic cracking
Solution Approach 1:
The stripping process is segmented into three zones with progressively changing conditions. The first zone operates with high catalyst inventory and low gas velocity to minimize backmixing and secondary cracking, while upper zones handle the bulk stripping. This segmentation allows efficient stripping without sacrificing product selectivity.
Solution Approach 2:
The first stripping zone performs preliminary stripping of underflow products before the catalyst enters the main reactor vessel. By removing these products early in a controlled environment with low gas velocity, secondary catalytic cracking is prevented, preserving product selectivity while maintaining overall stripping efficiency.
3Measurement precision
If soft coke reactions are not accounted for in cold flow modeling, then modeling accuracy is limited, but coke formation potential increases
Solution Approach 1:
The first stripping zone is designed to perform preliminary removal of underflow products and soft coke before they can undergo unwanted secondary reactions in the reactor vessel. This preliminary action accounts for soft coke reactions in the actual process design, improving both modeling accuracy and reducing coke formation potential.
Solution Approach 2:
The soft coke that would normally be a harmful factor leading to coke formation and reduced selectivity is converted into a benefit by using the first stripping zone to deliberately remove it under controlled conditions. The low gas velocity and high catalyst inventory in this zone allow soft coke to be stripped efficiently without causing secondary cracking, transforming a potential harm into a useful stripping mechanism.
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
The modifications significantly reduce underflow, improve product selectivity and stripping efficiency, and reduce coke formation potential by utilizing the 'soft coke' dry gas production for initial stripping, allowing for separate recovery and use in a regenerator combustion chamber to augment enthalpy balance and reduce emissions.
Implementation Method 1
vortex separation system (VSS) exit
Implementation Method 2
primary cyclone diplegs
Implementation Method 3
fluidized bed freeboard activity
Implementation Method 4
soft coke reactions
Data Source
AI summary
This patent application discloses engineering design modifications to the VSS exit, stripper entrance and the primary cyclone diplegs that can significantly reduce the underflow of reactor riser products into the stripper and reactor vessel and thereby produce higher desired product selectivities, improved stripping efficiency and a stripper vent gas, that continuously flows through the reactor vessel, with a low coke forming potential due to its low concentration of ethylene and higher molecular weight material, that could, if desired, be recovered separately from the primary riser products.