Bed Plate Grid with Vertical Baffles for Fluidized Bed Reactors
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Solution Overview
Problem
In fluidized bed gas phase polymerization reactors, uneven distribution of liquids beneath the bed plate leads to flooding, sheeting, and reduced product quality due to complex flow patterns and raceways on the bed plate, which can result in inefficient polymerization and reactor flooding.
Innovation Solution
A grid with vertical baffles is implemented beneath the bed plate to divide the area into cells, ensuring homogeneous distribution of the gas and liquid phases, preventing raceways and promoting uniform flow, which is modeled and optimized using Computational Fluid Dynamics to determine the best design for the bed plate and grid configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional bed plate is used in a fluidized bed reactor, then the structure is simple and easy to manufacture, but the liquid distribution becomes uneven causing flooding and sheeting
Solution Approach 1:
The bed plate is segmented into multiple flow cells by vertical baffles, dividing the single large chamber into smaller compartments. This segmentation ensures that liquid and gas flows are distributed more uniformly across each cell, preventing the formation of raceways and improving overall liquid distribution uniformity while maintaining a relatively simple overall structure.
2Productivity
If the recycle gas pipe creates a jet flow, then the gas circulation is maintained, but complex flow patterns and raceways form beneath the bed plate
Solution Approach 1:
Vertical baffles divide the space beneath the bed plate into multiple flow cells, segmenting the complex raceway flow patterns into simpler, more uniform flows within each cell. This maintains gas circulation while stabilizing the flow pattern composition.
Solution Approach 2:
The baffles create localized flow characteristics within each cell, allowing the gas jet to distribute its energy more evenly across multiple smaller regions rather than creating a single dominant raceway. This improves local flow uniformity while maintaining overall gas circulation.
3Volume of moving object
If the discharge port is positioned close to the bed plate, then the reactor design is compact, but the discharge port becomes flooded with liquid
Solution Approach 1:
The baffles create vertical separation within each flow cell, establishing a clearer distinction between the gas-phase discharge region and the liquid accumulation zone beneath the bed plate. This segmentation prevents liquid from reaching the discharge port even when positioned close to the bed plate, eliminating flooding while maintaining compact reactor design.
4Productivity
If uneven liquid distribution occurs in the bed, then the reactor operation continues, but product quality deteriorates due to sheeting and mud formation
Solution Approach 1:
By dividing the bed plate into multiple flow cells with vertical baffles, the system ensures more uniform liquid distribution across the catalyst bed. This prevents localized accumulation that leads to sheeting and mud formation, thereby maintaining high polymerization efficiency while improving product quality.
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 solution effectively reduces liquid pooling and flooding, improves the uniformity of flow patterns, and enhances product quality by ensuring that liquids are evenly distributed across the bed plate, thereby preventing reactor flooding and sheet formation.
Implementation Method 1
an upwardly directed jet comprising monomers, ballast gas and from 3 to 40 weight % of dispersed condensed hydrocarbons having a velocity sufficient to fluidize the bed
Implementation Method 2
a series of vertical baffles traversing the underside of the bed plate dividing the area below the bed plate into a series of cells so that from below the grid an upwardly directed jet... does not experience a raceway across the bed plate
Data Source
AI summary
A fluid dynamic model having at least 5,000,000 cells of the portion of a gas phase reactor from the exit of the condenser to a half a reactor diameter above the bed plate is useful in determining the design of the bottom surface or support structure for a bed plate to minimize liquid pooling below and above the bed plate when operating in condensing mode.