Vertical Separation Vessel Design for Ethylene Polymerization
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Solution Overview
Problem
Current high-pressure polymerization processes for ethylenically unsaturated monomers with free-radical initiators face challenges in separating polymeric and gaseous components efficiently, leading to polymer carryover in gas streams, fouling, and the need for frequent vessel cleaning, while also requiring large, costly separation vessels.
Innovation Solution
A process involving a vertically arranged cylindrical separation vessel with a specific inlet pipe design and operating conditions to separate polymer-monomer mixtures at controlled pressures and temperatures, minimizing polymer carryover and fouling, and allowing for extended production periods without vessel cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional separation vessels are used for separating polymeric and gaseous components, then separation can be achieved, but polymer carryover in gas streams occurs and fouling requires frequent vessel cleaning
Solution Approach 1:
The patent applies parameter changes by optimizing the separation vessel operating conditions (temperature and pressure) to maintain the polymer in a liquid state during separation. By controlling the temperature above the polymer's melting point and pressure to maintain liquidity, the polymer behaves differently in the separation vessel compared to conventional operations, reducing carryover and fouling while improving separation efficiency
Solution Approach 2:
The patent utilizes phase transitions by ensuring the polymer remains in a liquid phase throughout the separation process. By maintaining temperature above the melting point and appropriate pressure, the polymer transitions from a solid-like state in the reactor to a liquid state in the separator, enabling better separation from the gas phase and reducing adhesion to vessel walls, thereby minimizing fouling and carryover
2Reliability
If large separation vessels are used to improve separation efficiency, then separation performance increases, but vessel size and cost increase
Solution Approach 1:
The patent uses parameter changes (temperature and pressure control) to alter the physical state of the polymer to liquid, which significantly improves separation efficiency. This allows the use of smaller separation vessels because the liquid-phase polymer separates more effectively from the gas phase, reducing the volume needed while maintaining or improving separation performance
Solution Approach 2:
The patent implements periodic action through extended production periods between cleanings. By optimizing operating parameters to reduce fouling and carryover, the system enables longer operational cycles without vessel cleaning, effectively increasing productivity without requiring larger vessel capacity
3Object-generated harmful factors
If frequent vessel cleaning is performed to remove fouling, then fouling is reduced, but production time is lost and productivity decreases
Solution Approach 1:
The patent applies parameter changes by maintaining temperature above the polymer melting point and controlling pressure to keep polymer in liquid phase during separation. This significantly reduces fouling on vessel walls and internals, allowing extended production periods without cleaning and thereby maintaining high productivity
Solution Approach 2:
The patent implements preliminary action by pre-heating the polymer-monomer mixture to above the melting point before it enters the separation vessel. This preliminary temperature adjustment ensures the polymer remains in liquid phase throughout separation, preventing fouling before it can occur and enabling continuous operation without frequent cleaning interruptions
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 achieves low polymer carryover, reduces fouling, and enables efficient separation with smaller vessel designs, maintaining high separation efficiency and allowing for fast grade changes in ethylene homopolymer and copolymer production.
Implementation Method 1
separating the polymer-monomer mixture at a pressure of from 0.12 MPa to 0.6 MPa and a temperature of from 120° C. to 300° C. into a gaseous fraction and a liquid fraction
Implementation Method 2
separating the polymer-monomer mixture into a gaseous fraction and a liquid fraction
Data Source
AI summary
A process for separating polymeric and gaseous components of a polymer-monomer mixture at a pressure of from 0.12 MPa to 0.6 MPa and a temperature of from 120° C. to 300° C. in a separation vessel is provided. The separation vessel has a vertically arranged cylindrical shape with a ratio of length to diameter L/D of from 0.6 to 10 and an inlet pipe capable of introducing the polymer-monomer mixture into the separation vessel which the inlet pipe extends vertically from the top of the separation vessel into the separation vessel. Further a process for preparing ethylene homopolymers or copolymers from ethylenically unsaturated monomers in the presence of free-radical polymerization initiators at temperatures from 100° C. to 350° C. and pressures in the range of from 110 MPa to 500 MPa comprising such a process for separating a polymer-monomer mixture is provided.