Fluidized Bed Reactor With Tapered Upper Zone
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Solution Overview
Problem
Conventional fluidized bed reactors face issues with plugging of distribution plates due to entrainment of fines, limited production rate, and the formation of large bubbles which affect heat transfer and polymerization efficiency, leading to instability and low-quality polymer production.
Innovation Solution
A fluidized bed reactor design with a decreasing cross-sectional area in the upper zone, coupled with a moving bed reactor, where the upper zone is directly connected to the middle zone, allowing for efficient gas and solid separation and minimizing bubble formation, thereby reducing entrainment and enhancing heat transfer and polymer quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bed level is increased in conventional fluidized bed reactors to increase space-time yield, then productivity increases, but bubble size increases and material entrainment increases
Solution Approach 1:
The reactor is divided into multiple zones with different cross-sectional areas. The upper zone has a smaller cross-sectional area than the lower zone, creating a segmented structure that prevents bubble coalescence and reduces material entrainment while maintaining high productivity
Solution Approach 2:
Different zones of the reactor have different local geometric properties. The upper zone's reduced cross-sectional area creates specific flow conditions that suppress bubble formation and material entrainment, while the lower zone maintains sufficient volume for high productivity
2Object-generated harmful factors
If the cross-sectional area of the reactor is reduced in the upper zone, then bubble size is reduced and material entrainment is reduced, but reactor volume is reduced
Solution Approach 1:
The reactor volume is segmented into zones with different cross-sectional areas. The upper zone has reduced area to control bubbles and entrainment, while the lower zone compensates with sufficient volume for polymerization, maintaining overall productivity
Solution Approach 2:
Instead of uniformly reducing reactor volume, the invention changes the dimensional distribution by reducing cross-sectional area only in the upper zone while maintaining adequate volume in the lower zone, achieving both goals
3Stability of the object's composition
If a distribution plate is used in conventional fluidized bed reactors, then gas distribution is improved, but the distribution plate becomes plugged due to entrainment of fines
Solution Approach 1:
The gas distribution function is segmented between the reactor wall (providing radial distribution) and the bottom zone (providing axial distribution), eliminating the need for a separate distribution plate that would be susceptible to plugging
Solution Approach 2:
The distribution plate component is completely removed from the system. Its gas distribution function is replaced by the combined effect of the reactor geometry and fluidization dynamics in the bottom zone
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 design increases operational stability, reduces the formation of sheets, chunks, and lumps, and allows for higher production rates with improved polymer quality by maintaining a stable fluidized bed and efficient gas-particle distribution, leading to better heat balance and separation of polymer from gas.
Implementation Method 1
The reactor typically contains a fluidized bed comprising the growing polymer particles containing the active catalyst located above a distribution plate separating the bottom and the middle zone of the reactor. The velocity of the fluidization gas is adjusted such that a quasi-stationary situation is maintained, i.e. the bed is maintained at fluidized conditions.
Implementation Method 2
This part in the upper zone of the reactor is characterized by a diameter increase, reducing the gas velocity. Thereby the particles that are carried over from the bed with the fluidization gas for the most part settle back to the bed.
Implementation Method 3
In polyolefin production, olefins are polymerized in the presence of a polymerization catalyst in an upwards moving gas stream.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Reactor assembly for the production of polymers and process for producing polymers in the reactor assembly. The reactor assembly includes a fluidized bed reactor (1) comprising a bottom zone (5), a middle zone (6) and an upper zone (7), an inlet (8) for the fluidization gas located in the bottom zone (5), an outlet (9) for the fluidization gas located in the upper zone (7); the outlet (9) for the fluidization gas being coupled with the fluidized bed reactor (1) via inlet (8) via a gas circulation line; means for separation of solids from gas (2) being connected to said gas circulation line; the equivalent cross-sectional diameter of the upper zone (7) being monotonically decreasing with respect to the flow direction of the fluidization gas through the fluidized bed reactor; the middle zone (6) having an essentially constant equivalent cross-sectional diameter with respect to the flow direction of the fluidization gas through the fluidized bed reactor; characterized in that the ratio of the height of the fluidized bed reactor to the equivalent cross-sectional diameter of the middle zone of the fluidized bed reactor is from 2 to 10; and whereby said upper zone (7) is directly connected to said middle zone (6).