Multi-zone Reactor for Polyolefin Heat Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current gas fluidized bed reactors for polyolefin production face limitations in heat removal, leading to degradation of polymerization catalysts, polyolefins, and agglomeration, which restrict the production rate due to limited cooling capacity, especially when trying to introduce larger amounts of liquid in the recycle stream without destabilizing the fluidized bed.
Innovation Solution
A multi-zone reactor design with a first, second, third, and fourth zone, where the second and third zones have inner walls with gradually increasing diameters or continuously opening cones, allowing for higher liquid content in the recycle stream without destabilizing the bed, enabling turbulent conditions and increased production rates, and facilitating segregation of polymer particles by size and uniform temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If larger amounts of liquid are introduced in the recycle stream to increase heat removal capacity, then heat removal efficiency is improved, but the fluidized bed becomes destabilized
Solution Approach 1:
The reactor is divided into multiple zones (first zone with distributor plate, second zone with gradually increasing diameter, third zone, and fourth zone) to segment the fluidized bed. This segmentation allows different regions to handle different functions: the lower zones manage liquid introduction and vaporization for heat removal, while the upper zones maintain stable fluidization conditions, thus resolving the contradiction between heat removal capacity and bed stability.
Solution Approach 2:
The second zone features a gradually increasing diameter in the vertical direction, introducing a dimensional change to the reactor geometry. This dimensional variation allows the reactor cross-sectional area to increase with height, enabling better accommodation of vaporized liquid volumes while maintaining stable fluidization conditions in the upper regions, thus allowing higher liquid content in the recycle stream without destabilizing the bed.
2Productivity
If the rate of production of polyolefin is increased to improve productivity, then productivity is improved, but heat removal becomes insufficient leading to degradation and agglomeration
Solution Approach 1:
The process utilizes phase transition of the recycle stream from liquid to vapor. The recycle stream is cooled below its dew point to condense part of it, forming a two-phase stream that is introduced into the reactor. The liquid portion vaporizes upon exposure to reactor heat, providing efficient heat removal. This phase transition mechanism enables sufficient heat removal capability to support higher polyolefin production rates without degradation or agglomeration.
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
The multi-zone reactor design allows for higher polyolefin production rates, improved uniformity in particle size distribution, reduced fines, and enhanced mixing patterns, while maintaining reactor stability and operability, enabling two-stage polymerization and efficient heat management.
Implementation Method 1
cooling the gaseous recycle stream to a temperature below its dew point, resulting in the condensation of at least part of the recycle stream to form a bottom recycle stream containing liquid and gas
Implementation Method 2
The thus formed bottom recycle stream is then introduced into the fluidized bed polymerization reactor, where the liquid portion will vaporize upon exposure to the heat of the reactor, which vaporization will remove heat from the reactor
Implementation Method 3
In one part of the cycle, in a reactor a cycling gas stream is heated by the heat of polymerization
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a multi-zone reactor suitable for the continuous fluidized bed polymerization of one or more α-olefin monomers of which at least one is ethylene or propylene, which multi-zone reactor is operable in condensed mode, which multi-zone reactor comprises a first zone, a second zone, a third zone, a fourth zone and a distribution plate, wherein the first zone is separated from the second zone by the distribution plate, wherein the multi-zone reactor is extended in the vertical direction wherein the second zone of the multi-zone reactor is located above the first zone and wherein the third zone of the multi-zone reactor is located above the second zone, and wherein the fourth zone of the multi-zone reactor is located above the third zone wherein the second zone contains an inner wall, wherein at least part of the inner wall of the second zone is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor wherein the third zone contains an inner wall, wherein at least part of the inner wall of the third zone is either in the form of a gradually increasing inner diameter or a continuously opening cone, wherein the diameter or the opening increases in the vertical direction towards the top of the multi-zone reactor wherein the largest diameter of the inner wall of the third zone is larger than the largest diameter of the inner wall of the second zone.