Continuous Solution Polymerization Phase Separation
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Solution Overview
Problem
Continuous solution polymerization processes face challenges in efficiently separating and recovering polymers due to incomplete separation at improper operating conditions, leading to polymer carryover and equipment fouling in the recycle solvent stream.
Innovation Solution
The method involves polymerizing monomers and comonomers in a solvent, determining the composition and critical parameters of the polymer solution online, heating or cooling to within 50°C of the critical temperature, and passing through a pressure letdown valve to induce phase separation into polymer-rich and polymer-lean phases, allowing for efficient recovery of the polymer-rich phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If LCST separation is carried out at improper operating conditions, then the separation process is simpler to operate, but incomplete separation of polymer from polymer-lean phase occurs leading to polymer carryover and equipment fouling
Solution Approach 1:
The patent applies parameter changes by precisely controlling temperature and pressure parameters during LCST separation. The system adjusts the polymer solution temperature to be above the LCST and controls pressure to achieve optimal phase separation conditions, ensuring complete polymer separation while maintaining operational simplicity through automated parameter management
Solution Approach 2:
The patent implements feedback control by continuously monitoring polymer concentration in the polymer-lean phase and adjusting separation parameters accordingly. This feedback mechanism ensures that separation completeness is maintained while preventing polymer carryover and equipment fouling, resolving the contradiction between ease of operation and separation reliability
2Productivity
If polymer solution concentration is increased to improve productivity, then more polymer can be processed, but separation difficulty increases and equipment fouling worsens
Solution Approach 1:
The patent uses parameter changes to manage high-concentration polymer solution separation by adjusting temperature above LCST and optimizing pressure parameters. These parameter adjustments reduce separation difficulty and prevent equipment fouling even when processing high polymer concentrations, thereby maintaining productivity without increasing device complexity
3Reliability
If pressure is reduced to induce phase separation, then polymer-rich and polymer-lean phases separate, but polymer may plate out and foul equipment in the recycle solvent stream
Solution Approach 1:
The patent applies parameter changes by carefully controlling both temperature and pressure during phase separation. The temperature is maintained above LCST while pressure is reduced to induce phase separation. This coordinated parameter control ensures efficient separation while preventing polymer plate-out and equipment fouling in the recycle solvent stream
Solution Approach 2:
The patent implements beforehand cushioning by pre-heating the polymer solution to above LCST before pressure reduction. This preparatory temperature adjustment creates conditions that prevent polymer deposition during the subsequent pressure reduction and phase separation process, thereby preventing equipment fouling before it can occur
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 approach enhances polymer separation efficiency, reducing polymer carryover and fouling in the recycle solvent stream, thereby improving the operational reliability and efficiency of the polymerization process.
Implementation Method 1
A polymer solution can exhibit the Lower Critical Solution Temperature (LCST) phenomenon whereby the polymer solution separates into a polymer-rich liquid phase and a polymer-lean liquid phase above a certain temperature. This separation method involves heating the polymer solution under high pressure, followed by reducing the pressure to a point where two phases (polymer-rich phase and polymer-lean phase) are formed.
Implementation Method 2
heating or cooling the polymer solution to a temperature within 50°C of the critical temperature
Implementation Method 3
heating or cooling the polymer solution to a temperature within 50°C of the critical temperature
Implementation Method 4
passing the polymer solution through a pressure letdown valve into a liquid-liquid separator, where the pressure of the polymer solution is reduced or raised to a pressure within 50 psig of the critical pressure to induce a separation of the polymer solution into two liquid phases
Data Source
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AI summary
Described herein are methods for continuous solution polymerization. The method may comprise polymerizing one or more monomers and comonomers in the presence of a solvent in a polymerization reactor to produce a polymer solution; determining the composition of the polymer solution exiting the polymerization reactor in an on-line fashion; determining at least one of the critical pressure or critical temperature; comparing the critical pressure and/or critical temperature to the actual temperature of the polymer solution and the actual pressure of the polymer solution; heating or cooling the polymer solution to a temperature within 50 °C of the critical temperature; and passing the polymer solution through a pressure letdown valve into a liquid-liquid separator, where the pressure of the polymer solution is reduced or raised to a pressure within 50 psig of the critical pressure to induce a separation of the polymer solution into two liquid phases.