Gas-Phase Polymerization Reactor Transport Section Design
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Solution Overview
Problem
The existing gas-phase polymerization reactors with interconnected zones face challenges in maintaining homogeneous polymer flow and preventing obstructions in the transport section connecting the downcomer and riser, leading to partial melting and clogging due to high friction and temperature conditions.
Innovation Solution
The reactor design includes a transport section that is shaped as a descending bend with a gas distribution grid extending along the bending section for an angle of at least 50°, ensuring optimal carrier gas distribution and reducing friction, and a control valve to adjust the polymer flow rate, preventing polymer agglomerates and ensuring regular transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a carrier gas is fed to the inlet of the transport section for pneumatic transfer, then the polymer flow rate from downcomer to riser is improved, but the friction between polymer and wall increases causing superficial melting and polymer chunk formation
Solution Approach 1:
The transport section is designed with a curved descending bend geometry rather than a straight pipe, allowing the polymer flow to follow a smoother path that reduces abrupt changes in direction and minimizes wall friction. The curved shape enables gentler contact between polymer particles and section walls throughout the descent.
Solution Approach 2:
A gas distribution grid is introduced within the transport section to provide localized carrier gas distribution along the curved path. This ensures that carrier gas is available at multiple points along the transport section, maintaining polymer flowability without requiring excessive gas flow rates that would increase friction and melting.
2Device complexity
If the transport section is designed as a straight pipe, then the structure is simpler, but the polymer flow becomes blocked due to high friction and temperature conditions
Solution Approach 1:
The transport section employs a curved descending bend design that replaces the straight pipe configuration. This curvature allows the polymer flow to transition smoothly from the downcomer to the riser, reducing abrupt directional changes and minimizing wall friction that would otherwise cause blocking and agglomerate formation.
3Device complexity
If a gas distribution grid covers only the inlet of the transport section, then the device complexity is reduced, but the polymer flowability is not ensured due to partial blocking
Solution Approach 1:
The gas distribution grid is segmented into multiple zones along the curved transport section, with gas distribution outlets positioned at intervals along the bend. This segmentation ensures that carrier gas is distributed throughout the entire transport path, maintaining polymer flowability from the downcomer inlet through the curved section to the riser, and preventing blocking and agglomerate formation.
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 enhances the operability and efficiency of the polymer transfer from the downcomer to the riser, maintaining polymer flowability and preventing clogging, thus ensuring continuous and homogeneous polymer circulation without partial melting or agglomerate formation.
Implementation Method 1
The transfer of polymer between dowcomer and riser is generally achieved by means of pneumatic transport, i.e. by feeding a carrier gas to the inlet of the transport section
Implementation Method 2
a second polymerization zone (denominated as 'the downcomer'), through which they flow in a densified form under the action of gravity
Implementation Method 3
The polymer particles flow upwards through a first polymerization zone (denominated as 'the riser') under fast fluidization or transport conditions
Data Source
Figure 1
Figure 2
AI summary
A gas-phase polymerization reactor having interconnected polymerization zones comprising: - a riser through which the polymer particles flow upwards under fast fluidization conditions or transport conditions; -a dowcomer through which the polymer particles flow downward in a densified form under the action of gravity, the bottom of said downcomer being connected to the lower region of said riser by means of a transport section, said transport section being designed as a bend descending from the downcomer to the riser.