Stripping Section Baffle for FCC Vapor Isolation
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Solution Overview
Problem
In the fluid catalytic cracking (FCC) process, the high hydrocarbon partial pressure in the stripping section leads to over-cracking of product gases into undesired by-products due to prolonged residence time of product vapors with catalyst, which is exacerbated by the dense catalyst bed design intended to protect stripping internals from erosion.
Innovation Solution
A process and apparatus that evacuates stripped gaseous hydrocarbons from the stripping section through a passage isolating them from catalyst, reducing vapor residence time and hydrocarbon partial pressure, thereby minimizing over-cracking by directing gaseous products through a chamber containing catalyst using a baffle to guide them away from the dense catalyst bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense catalyst bed is maintained in the stripping section to protect stripping internals from erosion, then the stripping internals are protected from catalyst erosion, but the residence time of product vapors with catalyst is prolonged leading to over-cracking
Solution Approach 1:
The patent extracts the harmful interaction between product vapors and catalyst by providing a separate vapor removal path. The vapor withdrawal system removes hydrocarbon vapors from the stripping section before they can contact the catalyst bed, thereby eliminating the over-cracking problem while maintaining the dense catalyst bed for erosion protection.
Solution Approach 2:
The patent segments the stripping section into distinct zones: a catalyst stripping zone where catalyst flows downward, and a vapor withdrawal zone where hydrocarbon vapors are removed. This segmentation is achieved through strategically placed withdrawal ports and baffles that separate vapor flow paths from catalyst flow paths, allowing independent optimization of both functions.
2Object-generated harmful factors
If the residence time of product vapors with catalyst is reduced to prevent over-cracking, then over-cracking is minimized, but the protection of stripping internals from erosion is compromised
Solution Approach 1:
The patent introduces an intermediary vapor withdrawal system that acts as a mediator between the incoming hydrocarbon vapors and the catalyst bed. The withdrawal ports and associated piping system intercept vapors early in the stripping section and remove them via a separate pathway, preventing direct contact with the catalyst bed while maintaining the bed's protective function.
3Loss of substance
If steam stripping is used to remove hydrocarbons from spent catalyst, then hydrocarbon vapors are removed from catalyst, but the partial pressure of hydrocarbon increases leading to over-cracking
Solution Approach 1:
The patent extracts hydrocarbon vapors from the stripping section atmosphere through strategically placed withdrawal ports. These ports are positioned to intercept vapors as they are released from the catalyst during steam stripping, removing them from the system before they can accumulate and increase partial pressure to levels that cause over-cracking.
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 reduces coke production by 15 wt% relative to conventional operations, preserving desired liquid products and preventing erosion of stripping internals while maintaining efficient catalyst separation.
Implementation Method 1
evacuates stripped gaseous hydrocarbons out of the stripping section... reducing vapor residence time and hydrocarbon partial pressure
Implementation Method 2
A baffle may be interposed on the periphery of the stripping section for directing stripped gaseous products to the passage
Implementation Method 3
catalyst can potentially cause erosion of internal equipment... operating the dense catalyst bed with a designed height above the stripping internals to buffer the stripping internals from erosion
Data Source
AI summary
In an FCC apparatus and process gas and catalyst exit from a riser, are disengaged from each other and the catalyst is stripped. Product gases are evacuated from catalyst that can over crack the product gases to other undesired products. A baffle in or above the stripping section can direct product gases into a passage that evacuates the product gases to product recovery in isolation from the catalyst.