Bimodal Polymer Control Reducing Off-Grade Resin
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Solution Overview
Problem
Current polymerization processes face challenges in minimizing the production of off-grade polymer material during transitions between product grades or fluctuations in steady-state manufacturing, leading to economic losses and reactor shutdowns.
Innovation Solution
A method of controlling resin properties in bimodal and multimodal polymer compositions by manipulating process variables using mathematical models to adjust reaction conditions and production rates, minimizing dynamic deviations from desired characteristics and reducing off-grade material production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control methods (feeding retarders, adjusting temperature, removing reactants) are used during product transitions, then the transition can be managed, but significant amounts of off-grade polymer material are produced causing economic loss
Solution Approach 1:
The system performs preliminary calculations of resin properties and determines optimal control actions before the transition is complete. By predicting the bulk average resin properties based on current reactor state and planned changes, the system proactively adjusts process variables to minimize off-grade material production throughout the transition period, rather than reactively responding to quality deviations after they occur.
Solution Approach 2:
The system continuously monitors reactor conditions and resin properties, comparing actual measurements with model predictions. This feedback loop allows real-time adjustment of process variables (temperature, catalyst feed rate, reactant ratios) to maintain resin properties within specification limits during transitions, significantly reducing off-grade material compared to conventional open-loop control methods.
2Productivity
If the reactor operates under steady state conditions, then production efficiency is maintained, but variations can still result in off-grade polymer material leading to revenue loss and shutdown
Solution Approach 1:
During steady-state operation, the system continuously monitors resin properties and compares them against target specifications. When deviations are detected or predicted, the feedback control system automatically adjusts process variables to correct the deviation and maintain product quality within specifications, preventing shutdowns while maintaining high productivity.
Solution Approach 2:
The system uses mathematical models to predict potential quality deviations before they occur during steady-state operation. By calculating expected resin properties based on current reactor conditions and feed rates, the system can proactively adjust process parameters to prevent off-grade material production, maintaining both productivity and quality consistency.
3Loss of time
If product transitions are performed quickly, then production time is reduced, but the amount of off-grade material produced during transition increases
Solution Approach 1:
The system calculates optimal transition trajectories in advance, determining the sequence and magnitude of process variable adjustments needed to minimize off-grade material. By pre-planning the transition path based on mathematical models of resin property evolution, the system can execute transitions efficiently while maintaining quality control, avoiding both overly slow transitions and rushed transitions that produce excessive off-grade material.
Solution Approach 2:
The system dynamically adjusts process variables during transition based on real-time resin property measurements and model predictions. Rather than following a fixed pre-programmed transition schedule, the control system adapts the transition rate and variable adjustments to maintain resin properties within specification limits, minimizing off-grade material while completing transitions in optimal time.
Data Source
Figure 1
AI summary
The invention is directed to a polymerization system and method of controlling resin properties during the production of bimodal and multimodal polymer compositions using at least one manipulated variable to minimize dynamic deviations from polymer characteristics. In particular embodiments, the method of control includes determining a property of the resin based on a current and/or previous values or estimates or process variables or polymer characteristics. In this manner the control actions serve to reduce process upsets or facilitate in transitioning to a new product or grade to reduce the amount of off-grade resin material produced during transition or during steady state manufacture.