Tubular Reactor Outer Copper Layer Corrosion Resistance
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Solution Overview
Problem
High-pressure polyethylene reactors face issues with corrosion of the outer surface due to cooling water, leading to reduced reactor lifetime and undesirable reactions such as ethylene decomposition and molecular weight distribution broadening, which affect product quality and consistency.
Innovation Solution
A tubular reactor design featuring an inner steel material with specific composition and an outer copper layer, combined with a multi-stage compression system and multiple reaction zones with heating/cooling jackets, to manage temperature and pressure effectively, reducing corrosion and enhancing reaction control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water is circulated through the cooling jacket to remove reaction heat, then the reaction temperature is controlled and undesirable reactions are reduced, but the outer surface of the reactor tube corrodes and reactor lifetime is reduced
Solution Approach 1:
A corrosion-resistant coating layer is applied to the outer surface of the reactor tube, serving as an intermediary barrier between the cooling water and the steel tube. This coating prevents direct contact between water and steel, eliminating corrosion while maintaining the cooling function.
Solution Approach 2:
The reactor tube is designed as a composite structure with a steel inner tube providing mechanical strength and a corrosion-resistant outer coating layer providing protection against water corrosion. This composite design allows the system to withstand both high temperature/pressure conditions and resist corrosion from cooling water.
2Productivity
If high operating pressure and temperature are used to achieve high conversion, then productivity is improved, but ethylene decomposition and crosslinking occur leading to product quality issues
Solution Approach 1:
The reactor is divided into multiple zones with different temperature and pressure conditions. By segmenting the reaction process into controlled zones, the system achieves high overall conversion while maintaining product quality in each zone, preventing decomposition and crosslinking that occur in uncontrolled high-temperature regions.
Solution Approach 2:
The reactor operates with dynamically adjusted temperature and pressure parameters along its length. Temperature is controlled to remain below decomposition thresholds while pressure is maintained for high conversion. This parameter optimization allows achieving 95-98% conversion without undesirable side reactions.
3Stress or pressure
If the reactor tube is made thicker to withstand high pressure, then pressure resistance is improved, but heat transfer efficiency decreases and device complexity increases
Solution Approach 1:
The reactor tube uses a composite structure with optimized wall thickness - thick enough to withstand high pressure (1000-4000 bar) but not excessively thick. The composite design with corrosion-resistant coating allows using thinner walls than solid steel would require, improving heat transfer while maintaining pressure resistance.
Solution Approach 2:
The reactor tube has different wall thicknesses at different locations - thicker at ends and thinner in the middle section where heat transfer is most critical. This local optimization maintains structural integrity under pressure while maximizing heat transfer efficiency in the reaction zone.
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 prolongs the reactor's lifespan by minimizing corrosion and maintaining reaction control, leading to improved product quality and consistency by managing temperature and pressure effectively.
Implementation Method 1
the tubular reactor including one or more reaction zones having a heating/cooling jacket
Implementation Method 2
the initiator forms free-radical decomposition products
Implementation Method 3
a primary compressor, optionally in fluid communication with a two-stage secondary compressor
Implementation Method 4
the ethylene is converted to an ethylene-based polymer in a highly exothermic reaction
Data Source
Figure 1
AI summary
Embodiments of the invention provide an apparatus for the manufacture of polyethylene and polyethylene copolymers, The apparatus includes a primary compressor 1st fluid communication with a two-stage secondary compressor, the secondary compressor its fluid communication with a heated conduit in fluid communication with a tubular reactor, the tubular reactor including one or more reaction zones having a heating/cooling jacket, said reactor tube including an inner material and an outer material, said outer material being substantially inert in the presence of water under operating conditions, the tubular reactor in fluid communication with a product separator, and at least one conduit for the transfer of recycled ethylene from the product separator to the secondary compressor. Processes for manufacturing polyethylene and polyethylene copolymers using such an apparatus are also described.