Eccentric Inlet Cyclone for Olefin Polymerization Dust Removal
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Solution Overview
Problem
Gas-phase polymerization processes face issues with fine dust deposition in recycle gas systems, leading to reactor blockages, product quality impairment, and increased downtimes due to the need for multiple cyclones or acceptance of fine dust in the recycle gas line.
Innovation Solution
A cyclone design with a specific geometry, including an upper section with an eccentric inlet, a tapering middle section, and a cylindrical or truncated cone lower section, optimized with a distance-to-diameter ratio of 3 to 8 for effective particle separation, along with the use of a catalyst poison to prevent agglomeration and improve separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple cyclones are connected in series to ensure satisfactory removal of fine particles, then particle separation efficiency is improved, but device complexity increases
Solution Approach 1:
The cyclone is divided into three distinct sections (upper, middle, and lower) with different geometric characteristics. The upper section has a vertical central axis with eccentric inlet, the middle section tapers downward, and the lower section discharges particles. This segmentation allows each section to perform a specific function, achieving effective particle separation in a single integrated unit rather than requiring multiple separate cyclones.
Solution Approach 2:
The invention introduces a vertical tube extending down into the upper and middle sections of the cyclone, creating an additional dimensional feature that enhances particle separation. This internal tube structure adds a third dimension to the separation process, improving particle removal efficiency without increasing the horizontal footprint or requiring multiple cyclone units.
2Device complexity
If fine dust is accepted in the recycle gas line to avoid multiple cyclones, then device complexity is reduced, but product quality is impaired due to specks in the product
Solution Approach 1:
The cyclone performs preliminary separation of fine particles from the recycle gas before the gas returns to the reactor. By removing particles in advance, the system avoids the need for complex post-processing or multiple cyclones while ensuring product quality is maintained, as particles are removed before they can contaminate the polymer product.
3Manufacturing precision
If cyclone inlet is arranged eccentrically relative to the central axis, then particle separation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The cyclone inlet is deliberately positioned eccentrically (off-center) relative to the central axis of the cyclone body. This asymmetric arrangement creates more effective particle separation by improving the flow pattern and particle removal efficiency. The eccentric inlet is a standard design feature in cyclone separators and does not require exceptional manufacturing precision beyond conventional tolerances.
4Productivity
If the tube extending down into the cyclone has specific Hi/di ratio of 3 to 8, then particle separation at high velocities is improved, but device complexity increases
Solution Approach 1:
The invention optimizes the geometric parameters of the cyclone, specifically the ratio Hi/di (distance from lower end of tube to intersection point divided by tube diameter) to be between 3 and 8. This parameter optimization enables effective particle separation at high gas velocities without requiring multiple cyclones or complex additional structures. The optimized geometry achieves high productivity while maintaining reasonable device complexity.
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 ensures efficient separation of fine particles from the recycle gas at high velocities without the need for multiple cyclones, preventing agglomeration and maintaining product quality by effectively removing fine dust and catalyst poisons, thus reducing downtime and improving reactor performance.
Implementation Method 1
a cyclone located in the recycle gas line for the reduction and precipitation of the solid particles entrained in the recycle gas from the reactor
Implementation Method 2
whose wall extends along a rotationally symmetric body which tapers in a downward direction
Implementation Method 3
the bed comprising polymerizing polymer particles is kept in a fluidized state by introduction of a gas mixture from below
Implementation Method 4
The reaction gas is cooled in a heat exchanger located outside the reactor and is recirculated via a gas distributor plate back into the reactor
Data Source
AI summary
An apparatus for the polymerization of olefins, in particular ethylene, comprising a gas-phase fluidized-bed reactor (1), a recycle gas line (2) connected to the reactor for discharging and recirculating the recycle gas stream comprising the unpolymerized olefin and a cyclone (3) located in the recycle gas line for the reduction and precipitation of the solid particles entrained in the recycle gas from the reactor, with the cyclone comprising an upper section (3a) which has an essentially vertical central axis, whose wall extends along a rotationally symmetric body and which is provided with a cyclone inlet (4) arranged eccentrically relative to the central axis, a middle section (3b) which adjoins the upper section (3a) and whose wall extends along a rotationally symmetric body which tapers in a downward direction, a lower section (3c) for discharging the solid particles precipitated from the recycle gas which adjoins the middle section (3b) and whose wall extends along a rotationally symmetric body and a tube (5) extending essentially axially symmetrically down into the upper section and, if appropriate, the middle section for discharging the recycle gas which has been freed of the particles. According to the invention the ratio Hi of the distance hi from the lower end of the tube (5) extending downward into the cyclone to the intersection (6) of an imaginary extension of the wall of the downward-extending tube (5) with the wall of the middle section (3b) to the diameter di of the downward-extending tube (5) is from 3 to 8, in particular from 4 to 7.