High-Pressure Polymerization Blow Down System
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Solution Overview
Problem
High-pressure polymerization processes for polyethylene production face safety risks due to rapid ethylene decomposition, leading to explosive conditions and reactor contamination, which complicates shutdown and startup procedures, reducing operational efficiency and yield.
Innovation Solution
A high-pressure polymerization system with a reactor blow down system that includes an emergency valve for controlled expansion of polymerization contents into an aqueous quenching medium, followed by separation and transfer to a dump vessel, allowing for rapid depressurization and contamination prevention, enabling safe shutdown and immediate restart.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polymerization process is interrupted and the plant is depressurized after detecting a leakage, then safety is improved, but productivity decreases due to time-consuming shutdown and startup procedures
Solution Approach 1:
The blow down vessel is pre-filled with quenching water before any emergency occurs. When a disturbance is detected, the emergency valve immediately directs the polymerization mixture into this pre-prepared quenching medium, enabling instant safe shutdown without needing to first prepare quenching facilities or perform sequential safety preparations.
Solution Approach 2:
The system rushes through the dangerous high-pressure state by immediately diverting the polymerization mixture into the blow down vessel upon detecting any disturbance. This rapid transition skips the dangerous period where ethylene could decompose explosively, allowing the system to quickly move from a hazardous state to a safe state without prolonged exposure to risk.
2Stress or pressure
If the reactor content is disposed into the blow down vessel with hot ethylene and hot polymer, then pressure is reduced, but the system becomes contaminated with oxygen during subsequent purging operations
Solution Approach 1:
The blow down vessel maintains an inert atmosphere throughout the emergency shutdown process. By keeping the vessel filled with quenching water and operating under controlled conditions, the system prevents oxygen from entering the polymerization mixture during depressurization. This inert environment eliminates the need for extensive nitrogen purging operations that would otherwise be required to remove oxygen contamination before restart.
3Object-generated harmful factors
If extensive purging with nitrogen and ethylene is performed before restart, then system contamination is removed, but startup time increases
Solution Approach 1:
The harmful oxygen is extracted from the system by directing the polymerization mixture into the blow down vessel's quenching water, where oxygen is excluded. This extraction of the harmful element (oxygen) during the emergency shutdown eliminates the need for time-consuming purging operations, allowing the system to restart quickly without extensive nitrogen and ethylene purging cycles.
4Speed
If the emergency valve opens to allow expansion into the blow down vessel, then rapid depressurization is achieved, but the complexity of the blow down system increases
Solution Approach 1:
The blow down system is segmented into distinct functional components: the blow down vessel containing quenching water, the emergency valve for rapid isolation, and the discharge pathway. This segmentation allows each component to perform its specific function efficiently - the valve provides rapid opening/closing, the vessel provides immediate quenching capacity, and the system achieves fast depressurization without requiring complex integrated mechanisms.
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 solution safely interrupts polymerization during disturbances, reduces pressure rapidly, prevents reactor contamination, and allows for immediate restart, enhancing operational safety and efficiency by avoiding manual intervention and the need for extensive purging.
Implementation Method 1
opening the first emergency valve b2), thereby allowing the content of the polymerization system made from or containing polymer and gaseous components to expand into the reactor blow down vessel
Implementation Method 2
contacting the content of the polymerization system in the reactor blow down vessel with the aqueous quenching medium, thereby obtaining an aqueous polymer slurry
Implementation Method 3
separating the aqueous polymer slurry and the gaseous components
Data Source
AI summary
A process for polymerizing ethylene in a high-pressure polymerization system having a continuously operated polymerization reactor and a reactor blow down system having an emergency valve, a reactor blow down vessel containing an aqueous medium and a reactor blow down dump vessel, wherein the process includes the steps of monitoring the polymerization system for a disturbance, opening the emergency valve when a disturbance occurs to allow the content of the polymerization system to expand into the reactor blow down vessel, contacting the content of the polymerization system in the reactor blow down vessel with the aqueous medium to obtain an aqueous polymer slurry, separating the polymer slurry and gaseous components, and transferring the polymer slurry to the reactor blow down dump vessel.