Discontinuous TRRA Addition for Polyolefin Reactor Stability
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Solution Overview
Problem
Continuous gas-phase fluidized bed polymerization processes for polyolefins face challenges with heat management, leading to hot spots and agglomerate formation due to variations in catalyst and raw material quality, which limits production rates and reactor stability, and existing solutions reduce catalyst activity and polymer quality.
Innovation Solution
A process where a thermal runaway reducing agent (TRRA) is added discontinuously to the reactor based on specific conditions such as temperature, static voltage, and polymer analysis, allowing localized and timed addition to prevent thermal runaway while maintaining high productivity and catalyst activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous addition of thermal runaway reducing agent is used to prevent thermal runaway, then reactor stability is improved, but catalyst activity and polymer quality deteriorate
Solution Approach 1:
The patent applies periodic action by adding the thermal runaway reducing agent discontinuously rather than continuously. The addition occurs in periodic pulses based on monitored reactor conditions, specifically when temperature deviations indicate developing hot spots. This periodic addition maintains reactor stability by suppressing thermal runaway events while minimizing the total amount of reducing agent introduced, thereby preserving catalyst activity and polymer quality.
Solution Approach 2:
The patent implements feedback control by monitoring reactor temperature at multiple positions and using this information to trigger discontinuous addition of the thermal runaway reducing agent. When temperature sensors detect deviations exceeding predetermined thresholds, indicating developing hot spots, the system responds by adding the reducing agent. This feedback mechanism ensures reactor stability is maintained only when needed, avoiding unnecessary addition that would reduce catalyst activity.
2Device complexity
If cooled recycle gas is used as the sole means of heat removal, then heat management is simplified, but maximum production rates are limited
Solution Approach 1:
The patent introduces the thermal runaway reducing agent as an intermediary substance to assist the cooled recycle gas system in managing heat removal. The reducing agent acts as a chemical mediator that suppresses excessive heat generation at the source by preventing thermal runaway reactions, thereby complementing the physical heat removal capability of the cooled recycle gas. This dual approach enables higher production rates without overwhelming the heat removal system.
3Loss of energy
If high velocity recycle gas is used to increase heat removal rate, then heat management efficiency is improved, but bed stability is compromised
Solution Approach 1:
The patent converts the potentially harmful effect of high recycle gas velocity (which causes bed instability and lifting) into a beneficial approach by using discontinuous chemical intervention instead of continuous high-velocity gas flow. By adding the thermal runaway reducing agent in controlled pulses, the system achieves effective heat management without relying on high gas velocities that would compromise bed stability.
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 approach enables continuous high-productivity polyolefin production with reduced catalyst residues and improved reactor stability, maintaining high production rates without deteriorating polymer quality or reactor operability, and reduces the cost of catalyst systems by 30-40%.
Implementation Method 1
circulating fluids withdrawn from the reactor via a heat exchanger to cool the fluids back into the reactor
Data Source
AI summary
The present invention relates to a process for the continuous preparation of a polyolefin from one or more α-olefin monomers in a reactor system, the process for the continuous preparation of polyolefin comprising the steps of: +feeding a polymerization catalyst to a fluidized bed through an inlet for a polymerization catalyst; +feeding the one or more monomers to the reactor, +polymerizing the one or more monomers in the fluidized bed to prepare the polyolefin; +withdrawing polyolefin formed from the reactor through an outlet for polyolefin; +withdrawing fluids from the reactor through an outlet for fluids and transporting the fluids through first connection means, an heat exchanger to cool the fluids to produce a cooled recycle stream, and through second connection means back into the reactor via an inlet for the recycle stream; wherein a thermal run away reducing agent (TRRA) is added to the reactor in a discontinuous way.