Tubular LDPE Reactor CTA Injection for Fouling Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing tubular LDPE production processes face challenges with reactor fouling due to premature polymerization, which affects heat transfer efficiency and production rates, particularly when Chain Transfer Agents (CTAs) are injected in conventional methods, leading to fouling in compressors and preheaters.
Innovation Solution
A process involving the injection of a compressed make-up CTA system at specific locations within the tubular reactor, including upstream from the preheater, to achieve optimal mixing and minimize premature polymerization, with a log coefficient of variation relationship that ensures effective flow distribution and reduced fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If make-up CTAs are injected into the primary compressor system, then production rate is improved, but reactor fouling increases due to premature polymerization
Solution Approach 1:
The patent applies preliminary action by injecting make-up CTAs upstream from the preheater, allowing the CTAs to be distributed and mixed into the ethylene flow before the polymerization initiation temperature is reached. This preliminary distribution prevents premature polymerization in the preheater and compressor system, thereby reducing reactor fouling while maintaining high production rates.
2Object-generated harmful factors
If make-up CTAs are injected at the suction of the hyper compressor, then fouling in the hyper compressor system is reduced, but preheater fouling increases due to longer preheater length requirement
Solution Approach 1:
The patent changes the spatial dimension of CTA injection by moving it upstream from the preheater, creating a new injection zone before the preheater. This dimensional shift allows CTA distribution to occur in a different location and time frame, preventing premature polymerization in both the compressor system and preheater, thereby eliminating the need for extended preheater length.
3Stability of the object's composition
If make-up CTAs are injected directly to the reactor through a high pressure pump, then mixing behavior is improved, but cold spots are generated decreasing heat transfer
Solution Approach 1:
The patent uses the preheater as an intermediary zone where make-up CTAs are injected upstream and allowed to mix with the ethylene flow before entering the main reaction zone. This intermediary mixing approach ensures homogeneous CTA distribution without creating cold spots, as the mixing occurs in a controlled temperature environment that maintains heat transfer efficiency.
4Productivity
If very high level of CTA is used to reduce high molecular weight polymer, then fouling is reduced and production rate is improved, but premature polymerization increases generating fouling in compressor system
Solution Approach 1:
The patent applies preliminary action by injecting very high levels of make-up CTAs upstream from the preheater, allowing complete distribution and mixing into the ethylene flow before polymerization initiation. This preliminary action ensures that high CTA concentrations are present throughout the reaction zone to suppress high molecular weight polymer formation and reduce fouling, while preventing premature polymerization in the compressor system by maintaining proper spatial separation between injection point and reaction zone.
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 flow mixing, reduces fouling in the preheater and reactor, and improves heat transfer efficiency, allowing for higher production rates and better control over polymer properties such as melt index and molecular weight distribution.
Implementation Method 1
Reaction is initiated by radicals achieved from dissociation of peroxides
Implementation Method 2
injecting a compressed make-up CTA system at the location L1, at a distance (L-L1)/Dpreheater from 145 to 1000
Implementation Method 3
high pressure free radical polymerization process
Data Source
Figure 1A~2
Figure 3~5
Figure 6~7
AI summary
A process to form an ethylene-based polymer in a reactor system, said process comprising at least the following steps: a) injecting a first initiator mixture into the tubular reactor at location L along the reactor, b) injecting a compressed make-up CTA system at the location L1, at a distance (L-L1) from 145*Dprehehater to 1000*Dpreheater, upstream from L, and wherein Dpreheater = the inner diameter of the pre-heater in meter (m); and wherein L1 is located in the preheater, and c) optionally, injecting one or more additional compressed make-up CTA system(s) into the preheater, at one or more location: LiLi+1, Ln (2 ≤ i and 2 ≤ n), upstream from L1, and each location is, independently, at a distance from 145*Dprehehater to 1000*Dpreheater, and wherein n equals the total number of injection locations of the make-up CTA system(s) injected into the preheater, upstream from L1, and wherein (L-L1) is less than each (L-Li), (L-Li+1), (L-Ln); and d) polymerizing a reaction mixture comprising at least ethylene, the first initiator mixture, and the compressed make-up CTA system of step b), and wherein the process has a log coefficient of variation (log(CoV1)), at L1, that meets the relationships described herein.