Series Slurry Reactor Volume Ratio for Heat Removal
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Solution Overview
Problem
Optimizing the size and configuration of multiple slurry phase reactors in series for olefin polymerization is challenging due to conflicting requirements for heat removal, catalyst activity, and product distribution, especially when using different catalyst types, as the ideal reactor size ratio is not obvious and varies significantly under different operating conditions.
Innovation Solution
A process where the second reactor is at least 10% larger than the first reactor, with a solids concentration of 35-60% and a volume ratio of 1:0.6-0.8, allowing for balanced production rates by adjusting residence time and catalyst flow, and using a loop reactor design with specific L/D ratios to optimize cooling capacity and minimize total reactor volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the second reactor is made larger to handle polymer from the first reactor and maintain space time yields, then the heat removal requirement of the larger downstream reactor becomes greater, making it harder to control reaction temperature
Solution Approach 1:
The patent divides the polymerization process into multiple reactors arranged in series, where each reactor handles a specific portion of the total polymerization load. The second reactor is designed to be larger than the first to accommodate the combined polymer production from both reactors, while the segmentation allows each reactor to have optimized cooling capacity proportional to its size and heat generation rate.
Solution Approach 2:
The patent applies different design characteristics to different reactors based on their specific functions. The second reactor, being larger and handling more polymer, is designed with enhanced local cooling capacity in the regions where heat generation is highest, rather than uniformly scaling all dimensions. This allows targeted heat removal where needed while minimizing total reactor volume.
2Productivity
If the reactor volume is increased to maintain similar space time yields in downstream reactors, then the total reactor volume increases, but the heat removal capability becomes insufficient relative to the production rate
Solution Approach 1:
The patent employs dynamic adjustment of operating parameters including slurry circulation rate, cooling medium flow rate, and potentially catalyst feed rate to balance heat generation and heat removal in real-time. The larger second reactor incorporates dynamic cooling control that adjusts to the actual polymerization rate and heat generation, allowing the system to maintain optimal space time yield while adapting heat removal capability to match production demands.
3Adaptability or versatility
If different catalyst types are used in different reactors to achieve desired product distribution, then the ideal reactor size ratio varies significantly between catalyst systems, making it difficult to select an optimal configuration
Solution Approach 1:
The patent designs the multiple reactor system with universal scaling principles that can accommodate different catalyst types. The size ratio between reactors is determined by fundamental heat generation and heat removal relationships that are relatively consistent across different catalyst systems. This universal design approach allows the same reactor configuration to be adapted to various catalyst types (Ziegler-Natta, chromium, metallocene) by adjusting operating parameters rather than redesigning the entire system geometry.
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 configuration minimizes total reactor volume while maintaining flexibility and achieving balanced production rates, efficient heat transfer, and high space-time yields, while reducing the need for recompression in flash tanks by controlling light component concentrations.
Implementation Method 1
The heat of polymerisation is typically removed using indirect exchange with a cooling medium, preferably water, in jackets surrounding at least part of the tubular loop reactor
Implementation Method 2
The slurry is pumped around the relatively smooth path endless loop reaction system at fluid velocities sufficient to maintain the polymer in suspension in the slurry
Implementation Method 3
The product slurry comprising polymer and diluent, and in most cases catalyst, olefin monomer and comonomer can be discharged intermittently or continuously, optionally using concentrating devices such as hydrocyclones or settling legs to minimise the quantity of fluids withdrawn with the polymer
Data Source
AI summary
Process for producing a multimodal polyethylene in at least two reactors connected in series, in which 20-80wt% of a high molecular weight (HMW) polymer is made in suspension in a first reactor and 20-80wt% of a low molecular weight (LMW) polymer is made in suspension in a second reactor in the presence of the HMW polymer, wherein the solids concentration in the second LMW reactor, defined as the mass of polymer divided by the total mass of slurry, is at least 35wt%, most preferably between 45wt% and 60wt%, and/or the the ratio of solids concentration in the first reactor to that in the second reactor is maintained at less than 1.0, preferably between 0.6 and 0.8, and further wherein the volume of the second reactor is at least 10%, preferably at least 30% and more preferably at least 50% greater than the volume of the first reactor.