Polymer Discharge Lines for Gas-Phase Reactor Blockage Prevention
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Solution Overview
Problem
Existing gas-phase polymerization processes face challenges in conveniently discharging polyolefin particles without disrupting continuous polymerization, ensuring polymer quality, and maintaining reliable operation over time, while also being cost-effective.
Innovation Solution
A discontinuous discharge process using at least two horizontal or upward discharge lines with a curvature ratio of R/D ≥ 20, where polyolefin particles are transported from a high-pressure reactor (1.0 MPa to 10 MPa) to a lower-pressure discharge vessel (0.001 MPa to 1.0 MPa), with countercurrent flows from multiple lines to minimize reaction gas exit and prevent blockages, and incorporating a degassing vessel for inert gas assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polyolefin particles are discharged continuously from the gas-phase polymerization reactor, then the polymerization process can run continuously, but the polymer properties may be impaired due to excessive friction and heat generation
Solution Approach 1:
The discharge system is divided into multiple parallel discharge lines (at least two) instead of using a single continuous discharge line. This segmentation allows the polymer to be discharged in separate streams, reducing the friction and heat generation in each individual line while maintaining continuous overall discharge capability.
Solution Approach 2:
The discharge operation is performed periodically rather than continuously through a single line. Each discharge line operates in periodic cycles, opening and closing valves to discharge polymer batches alternately. This periodic action reduces cumulative friction and heat exposure on the polymer particles.
2Device complexity
If the discharge lines have sharp bends to reduce space requirements, then the device complexity is reduced, but blockages occur more frequently
Solution Approach 1:
The discharge lines are designed with large radius bends instead of sharp angles. The curvature ratio R/D (radius of curvature divided by pipe inner diameter) is specified to be at least 20, ensuring smooth transitions that prevent polymer particles from accumulating and blocking the discharge lines, while still achieving compact configuration through optimized curved paths.
3Reliability
If multiple discharge lines are used to reduce blockage risk, then the reliability improves, but the device complexity increases
Solution Approach 1:
Multiple discharge lines are merged into a common discharge vessel where the polymer streams from different lines converge. This merging approach allows the system to benefit from multiple parallel discharge paths (improving reliability and reducing blockage risk) while consolidating the discharge point, thereby limiting the overall increase in device complexity.
4Productivity
If the discharge velocity is increased to improve productivity, then the polymer can be discharged faster, but the reaction gas exit increases
Solution Approach 1:
The total discharge rate is segmented across multiple parallel discharge lines. Each line operates at a moderate velocity that minimizes reaction gas carryover, while the combined output of multiple lines achieves the required total productivity. This segmentation allows maintaining lower velocities in individual lines without sacrificing overall discharge capacity.
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 process effectively controls the discharge of polyolefin particles, reduces reaction gas exit, minimizes the risk of blockages, and maintains polymer quality by limiting the amount of polymer discharged per unit time, allowing for flexible operation and reduced risk of melting or impairing the polymer properties.
Implementation Method 1
transported from the reactor to a discharge vessel by at least two discharge lines
Implementation Method 2
the flow of the polymer particles entering the discharge vessel from one discharge line is countercurrent to the flow of the polymer particles entering the discharge vessel from another discharge line
Implementation Method 3
discharge vessel of a pressure from 0.001 MPa to 1.0 MPa
Data Source
Figure 1
Figure 2~3
AI summary
Process for discharging polyolefin particles from a gas-phase polymerization reactor of a pressure from 1.0 MPa to 10 MPa to a discharge vessel of a pressure from 0.1 MPa to 1.0 MPa wherein the discharging is carried out discontinuously through at least two discharge lines in which the polyolefin particles are transported horizontally or upwards, process for polymerizing olefins at temperatures of from 30°C to 160°C and pressures of from 1.0 MPa to 10 MPa in the presence of a polymerization catalyst in a gas-phase polymerization reactor comprising discharging the obtained polyolefin particles from the gas-phase polymerization reactor by the process for discharging polyolefin particles and apparatus for polymerizing olefins in the gas-phase comprising a polymerization reactor, a discharge vessel and at least two pipes connecting the polymerization reactor and the discharge vessel for discharging polyolefin particles, wherein the discharge lines are constructed in a way that the polyolefin particles conveyed from the polymerization reactor to the discharge vessel are transported horizontally or upwards.