Multimodal Polyethylene Pipe Process With Interstage Hydrogen Removal
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Solution Overview
Problem
Current multimodal polyethylene polymerization processes face challenges in achieving a balance between mechanical properties such as Charpy impact strength, slow crack growth resistance, and pressure resistance, while maintaining processability, particularly in the production of polyethylene pipes for long-term hydrostatic strength and durability under gas or water pressure.
Innovation Solution
A reactor system comprising a first reactor, a hydrogen removal unit, and a third reactor, where 98.0 to 99.8% of hydrogen is removed from the slurry mixture in the hydrogen removal unit before transferring it to the second reactor, allowing for the production of multimodal polyethylene with improved mechanical properties by controlling the molecular weight and comonomer distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hydrogen is not removed from the first reactor before transferring to the second reactor, then the production process is simpler and faster, but the molecular weight control and mechanical properties of the final polymer are compromised
Solution Approach 1:
The patent extracts hydrogen from the slurry mixture between the first and second reactors using a hydrogen removal unit. This extraction ensures that residual hydrogen from the first reactor does not interfere with the polymerization conditions in the second reactor, thereby enabling precise control over molecular weight and mechanical properties of the final multimodal polyethylene.
Solution Approach 2:
The hydrogen removal unit performs preliminary action by removing hydrogen before the slurry enters the second reactor. This preliminary removal prevents hydrogen from affecting the high molecular weight polymerization in the second reactor, ensuring that the desired molecular weight distribution and mechanical properties are achieved.
2Stability of the object's composition
If high molecular weight polymer is produced in the second reactor with residual hydrogen from the first reactor, then the process is simpler, but the molecular weight distribution and physical properties are compromised
Solution Approach 1:
Hydrogen is extracted from the slurry mixture using a hydrogen removal unit positioned between the first and second reactors. This extraction ensures that the second reactor operates with controlled hydrogen levels, enabling precise molecular weight distribution in the high molecular weight polymer fraction while maintaining production efficiency.
3Strength
If multiple reactors are used to produce different molecular weight fractions, then the mechanical properties are improved, but the process complexity and equipment requirements increase
Solution Approach 1:
The patent segments the polymerization process into multiple reactors, each producing polymer fractions with specific molecular weights. The first reactor produces low molecular weight fraction, the second produces high molecular weight fraction, and the third produces ultra-high molecular weight fraction. This segmentation enables control over mechanical properties while the hydrogen removal unit manages the complexity by selectively removing hydrogen between stages.
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
The process enhances the mechanical properties of polyethylene pipes, including Charpy impact strength and slow crack growth resistance, while maintaining flexibility and durability, effectively addressing the limitations of prior art in polyethylene pipe manufacturing.
Implementation Method 1
a hydrogen removal unit arranged between the first reactor and a second reactor, comprising at least one vessel connected with a depressurization equipment, preferably selected from vacuum pump, compressor, blower, ejector or a combination thereof, the depressurization equipment allowing to adjust an operating pressure to a pressure in a range of 100-200 kPa (abs)
Data Source
AI summary
The present invention relates to a reactor system for a multimodal polyethylene polymerization process, comprising: (a) first reactor; (b) a hydrogen removal unit arranged between the first reactor and a second reactor comprising at least one vessel connected with a depressurization equipment, preferably selected, from vacuum pump, compressor, blower, ejector or a combination thereof, the depressurization equipment allowing to adjust an operating pressure to a pressure in a range of 100-200 kPa (abs); (c) the second reactor; and (d) a third reactor and use thereof as a pipe.