Hydrogen Feeding System for Loop Reactor Molecular Weight Control
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Solution Overview
Problem
The challenge in ethylene polymerization is controlling the molecular weight distribution and hydrogen concentration in loop reactors, leading to non-uniform polymer properties due to fluctuations in reactant concentrations and temperatures along the reactor path.
Innovation Solution
The process involves controlling the hydrogen/ethylene ratio by feeding hydrogen at multiple, spatially separated points along the loop reactor path, which helps maintain a consistent ratio and minimize fluctuations, thereby improving molecular weight distribution and compositional homogeneity of the polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydrogen is fed at a single point in the loop reactor, then the device complexity is low, but the compositional homogeneity and molecular weight distribution of the polymer deteriorate due to fluctuations in hydrogen/ethylene ratio along the reactor path
Solution Approach 1:
The hydrogen feeding system is segmented into multiple injection points distributed along the loop reactor path. This segmentation allows hydrogen to be introduced at different locations, maintaining a more uniform hydrogen/ethylene ratio throughout the reactor and improving polymer compositional homogeneity and molecular weight distribution.
Solution Approach 2:
Different regions of the reactor receive hydrogen at optimized locations to address local variations in reactant concentration. By placing hydrogen feed points at specific positions along the loop reactor, the system achieves local optimization of the hydrogen/ethylene ratio, resulting in improved overall compositional uniformity.
2Productivity
If the loop reactor length is increased to improve productivity, then the output increases, but the compositional uniformity deteriorates due to greater variations in reactant concentration along the reactor path
Solution Approach 1:
The extended reactor path is segmented into multiple zones with distributed hydrogen injection points. This allows the longer reactor to maintain uniform reactant ratios across its entire length, enabling increased productivity without sacrificing compositional uniformity.
Solution Approach 2:
The problem of maintaining uniformity along the reactor path is addressed by adding the dimension of multiple spatial feeding points. Instead of relying on a single feed point, hydrogen is introduced at multiple locations along the reactor path, effectively managing composition control in extended reactor configurations.
3Manufacturing precision
If multiple spatially separated hydrogen feeding points are used to improve compositional homogeneity, then the molecular weight distribution improves, but the device complexity increases
Solution Approach 1:
The hydrogen feeding system is divided into multiple injection points to achieve precise control over molecular weight distribution. Each feeding point contributes to maintaining the optimal hydrogen/ethylene ratio in its local zone, collectively achieving superior molecular weight distribution control throughout the reactor.
Solution Approach 2:
The multiple hydrogen feeding points enable better feedback control of the polymerization process. By monitoring polymer properties and adjusting hydrogen feed rates at different points, the system can maintain optimal molecular weight distribution through dynamic adjustment of local feeding conditions.
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 results in polymers with improved optical properties and compositional homogeneity, reducing the variation in hydrogen/ethylene ratio to less than 10% between the reactor inlet and outlet, leading to more consistent polymer properties.
Implementation Method 1
feeding at least one polymerization catalyst into the reactor; polymerizing said monomer and said optional co-monomer(s) to produce a polymer slurry
Implementation Method 2
The slurry in the reactor is circulated continuously with a pump to maintain efficient suspension of the polymer solid particles in the liquid diluent
Implementation Method 3
The product is discharged from the loop reactor by means of settling legs, which operate on a batch principle to recover the product. Settling in the legs is used to increase the solids concentration of the slurry
Implementation Method 4
The product is further discharged through flash lines to a flash tank, where most of the diluent and unreacted monomers are flashed off and recycled
Data Source
AI summary
The present invention relates to a process for improving the polymerization of ethylene and one or more optional co-monomer(s) in a polymerization loop reactor characterized in that said process comprises the step of controlling the hydrogen/monomer ratio along the path of the reactor by multiple, spatially separated, feeding of hydrogen along the path of the loop reactor. In particular, the invention provides a process for controlling, and preferably narrowing, the molecular weight distribution of the produced polymer particles. In another aspect, the invention relates to a polymerization loop reactor suitable for the polymerization process of ethylene and an optional olefin co-monomer, wherein the molecular weight distribution of the produced ethylene polymer can be controlled.