LDPE Reactor Injector Geometry for Uniform Reactive Fluid Mixing
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Solution Overview
Problem
Existing reactor systems for high-pressure ethylene polymerization face issues with inadequate distribution of reactive fluids, leading to back mixing and material build-up, which affects the quality and consistency of polyethylene production, especially in severe production environments.
Innovation Solution
A reactor system with a device for injecting and mixing reactive fluids, featuring a cylindrically shaped injector part with a downstream nozzle and a fin-shaped support structure made from a single piece of metal, designed to minimize asymmetrical turbulence and prevent back mixing, with a tapered nozzle and wedge-shaped fronts to streamline fluid flow and reduce fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional injector design is used to introduce reactive fluid into the reaction vessel, then the injection process is simple, but the reactive fluid is not sufficiently dispersed into ethylene gas causing local homopolymerization and gel-like materials
Solution Approach 1:
The injector design segments the reactive fluid injection into multiple stages: pre-mixing zone, main injection zone, and dispersion zone. The fluid is first pre-mixed with inert gas, then injected through multiple nozzle arrays arranged in segments along the reactor length, ensuring gradual dispersion rather than concentrated local injection
Solution Approach 2:
An intermediary inert gas (nitrogen or carbon dioxide) is introduced to carry and disperse the reactive fluid throughout the ethylene gas stream. This intermediary medium prevents direct contact between concentrated reactive fluid and ethylene, avoiding local homopolymerization while ensuring uniform distribution
2Productivity
If high pressure conditions are used for LDPE production, then polymerization efficiency is improved, but material build-up and fouling occur in the reactor system
Solution Approach 1:
The system performs preliminary action by pre-mixing the reactive fluid with inert gas and pre-heating the mixture before introduction to the high-pressure reaction zone. This preliminary preparation ensures controlled reaction initiation and prevents sudden localized reactions that cause material build-up
Solution Approach 2:
The design converts the high-pressure condition, which normally causes fouling, into a benefit by using compressed inert gas to actively disperse reactive fluid. The high pressure that would concentrate reactants is instead used to drive the inert gas flow pattern that ensures uniform distribution, turning a harmful effect into a dispersing mechanism
3Reliability
If multiple separate components are used for the injector assembly, then manufacturing and assembly are flexible, but mechanical strength and reliability decrease under severe conditions
Solution Approach 1:
The injector assembly merges multiple functional components (support structure, mounting brackets, nozzle holders, and injection manifolds) into a single integrated unit. This monolithic structure eliminates weak points at connection interfaces and ensures uniform stress distribution under high-pressure conditions, significantly improving mechanical reliability
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 solution ensures even distribution of the reactive fluid, reduces back mixing and fouling, and maintains mechanical integrity under harsh conditions, enabling efficient production of high-quality ethylene polymers at high pressures and temperatures.
Implementation Method 1
The device ensures even distribution of the injected fluid in a turbulent flow of the process fluid with a reduced back mixing
Data Source
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AI summary
The invention relates to a device (100) for injecting and mixing a reactive fluid in a flow of a process fluid for the preparation of polyolefins, comprising: • an annular part (101) having an outer wall and an inner wall (102), wherein the annular part (101) is arranged for having a flow of the process fluid in a transport direction (F); • a support structure (103) connected to the inner wall (102) of the annular part (101); • an injector part (104) mounted on the support structure (103), wherein the injector part (104) is cylindrically shaped and wherein the cylindrical axis A-A' of the injector part is parallel with a central axis of the annular part and is in the central part of the annular part (101); wherein the injector part (104) comprises a nozzle (105) for injecting the reactive fluid, disposed at a downstream side of the injector part relative to the transport direction (F); • a supply channel (106) extending from the outer wall of the annular part (101) through the support structure (103) to the nozzle (105) of the injector part (104), and wherein the annular part (101), the support structure (103) and the injector part (104) are made from a single piece of metal.