Stripping Vessel Grid Spacing to Prevent Catalyst Accumulation
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Solution Overview
Problem
Existing FCC stripping vessels with structured packing sections often experience catalyst overaccumulation and gas channeling, leading to reduced stripping efficiency and hydraulic issues due to excessive space between the packing and inlet, necessitating a design that minimizes catalyst compression and mal-distribution without additional equipment.
Innovation Solution
Incorporating a grid section above the structured packing in the stripping vessel, with specific spacing to prevent catalyst accumulation, comprising grating with openings to allow catalyst passage, and a second structured packing section with ribbons configured in undulating peaks and valleys to obstruct fluid and catalyst passage, ensuring efficient hydrocarbon removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a structured packing section is installed in an existing stripping vessel, then stripping efficiency is improved, but catalyst overaccumulation occurs due to excessive space between the packing and inlet
Solution Approach 1:
The stripping vessel is segmented into distinct sections: an upper section with a distributed inlet system, a middle section containing structured packing, and a lower section for catalyst collection. This segmentation allows the inlet to be positioned close to the packing while maintaining proper flow distribution, preventing catalyst overaccumulation in any single region.
Solution Approach 2:
The inlet system transitions from a single-point entry to a distributed multi-point entry system across the upper cross-section of the vessel. This dimensional change in inlet configuration allows catalyst to be introduced at multiple locations simultaneously, preventing localized overaccumulation and improving flow distribution across the packing section.
2Quantity of substance
If excessive space exists between the structured packing and inlet, then catalyst can accumulate, but reducing space may cause gas channeling and mal-distribution
Solution Approach 1:
The inlet system is segmented into multiple inlet ports distributed across the upper cross-section, with each inlet positioned at an optimized distance from the packing. This segmentation allows the space to be effectively utilized without creating channeling, as each inlet serves a specific zone and maintains appropriate spacing from the packing.
Solution Approach 2:
Different regions of the vessel are given different inlet configurations and spacing arrangements tailored to local flow requirements. The inlet distribution pattern is optimized locally to prevent both accumulation in some areas and channeling in others, with each zone having customized inlet positioning relative to the packing.
3Productivity
If catalyst accumulates excessively in the stripping vessel, then stripping efficiency decreases, but adding equipment to prevent accumulation increases device complexity
Solution Approach 1:
The distributed inlet system serves multiple functions simultaneously: it prevents catalyst overaccumulation, ensures uniform flow distribution across the packing, and maintains appropriate spacing to prevent channeling. This single structural modification achieves multiple objectives without requiring additional separate equipment.
Solution Approach 2:
The vessel structure itself is modified to prevent catalyst accumulation through the inlet configuration, rather than requiring separate control systems or additional equipment. The geometry and inlet arrangement create self-regulating flow patterns that naturally prevent accumulation and channeling.
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 grid-based design effectively minimizes catalyst overaccumulation and gas bypassing, maintaining efficient catalyst and vapor flow, thereby enhancing stripping efficiency and preventing hydraulic issues in the reactor and standpipe.
Implementation Method 1
the catalytic materials may retain hydrocarbons within their pores, upon the external surface of the catalyst, as well as within the spaces between individual catalyst particles
Implementation Method 2
the catalytic materials may retain hydrocarbons within their pores, upon the external surface of the catalyst
Implementation Method 3
a first stripping section including at least one grid... spaced from the structured packing... so as to minimize an accumulation of catalyst on top of stripping sections
Implementation Method 4
the most common method of stripping hydrocarbons from the catalyst utilizes a stripping gas, usually steam, passed through a stream of catalyst, counter-current to the direction of flow of the catalyst
Implementation Method 5
remove the hydrocarbon vapors which are entrained with the catalyst and adsorbed on the catalyst
Data Source
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AI summary
A stripping vessel for removing hydrocarbons from a catalyst and a process for removing hydrocarbons from a catalyst. In an FCC unit, the stripping vessel includes first and second stripping sections. The first stripping section includes at least one grid having a plurality of interesting members and openings therebetween. The second stripping section includes structured packing such as a plurality of ribbons. The one or more grids are spaced from the structured packing, and from each other, so as to minimize the accumulation of catalyst within the stripping vessel, preferably between 0.91 m (3 ft.) to 1.5 m (5 ft.).