Fluidized-Bed Polyethylene Polymerization with Particle-Sized Support
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Solution Overview
Problem
Existing gas phase polymerization processes in fluidized bed reactors face issues with sheeting and agglomeration due to the use of metallocene catalysts, leading to reactor fouling and increased costs from additives, and the accumulation of polymer fines, which complicates process control and increases costs.
Innovation Solution
Selecting a particulate support for the polymerization catalyst with specific particle size distribution, specifically d10 of at least 18 microns, d50 of at least 40 microns, and d90 of no more than 100 microns, reduces polymer fines and minimizes reactor fouling, allowing for higher superficial gas velocities and improved cooling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metallocene catalysts are used in fluidized bed reactors, then polymer properties such as narrow molecular weight distribution and improved structural performance are achieved, but sheeting and fouling in the reactor system increase
Solution Approach 1:
The patent changes the particle size parameters of the catalyst support material, specifying a d10 of at least 18 microns, d50 of at least 40 microns, and d90 of no more than 100 microns. This parameter change in the support material properties resolves the contradiction by preventing sheeting and fouling while maintaining the benefits of metallocene catalysts.
2Object-generated harmful factors
If static control agents are added to control sheeting, then sheet formation is reduced, but process cost and complexity increase
Solution Approach 1:
The patent extracts and eliminates the need for static control agents by using appropriately sized catalyst support material. The larger particle size support (d10 ≥ 18 microns) inherently prevents sheeting without requiring additional chemical additives or complex monitoring systems, thus removing the harmful effect without adding complexity.
3Productivity
If higher operating temperatures are used, then production rate increases, but particle agglomeration and runaway reactions increase due to heat transfer issues
Solution Approach 1:
The patent changes the particle size distribution parameters of the catalyst support to prevent agglomeration, enabling operation at higher temperatures for increased production rate. The larger support particles (d50 ≥ 40 microns) maintain better heat transfer characteristics and prevent the formation of hot spots that would cause runaway reactions.
4Quantity of substance
If smaller particle size catalyst support is used, then catalyst surface area increases, but polymer fines accumulation and reactor fouling increase
Solution Approach 1:
The patent optimizes the particle size parameters of the catalyst support material to achieve a balance between surface area and fines generation. By specifying d10 ≥ 18 microns, d50 ≥ 40 microns, and d90 ≤ 100 microns, the patent maintains sufficient catalyst surface area while preventing the generation of excessive polymer fines that lead to reactor fouling.
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 significantly reduces reactor fouling and the need for additives, enabling higher production rates and more efficient operation by controlling particle size distribution and maintaining uniform reactor conditions.
Implementation Method 1
The reaction is maintained in a two-phase fluidized bed of granular polyethylene polymers and gaseous reactants by a fluidizing gas which is passed through a distributor plate near the bottom of the reactor vessel
Implementation Method 2
heat of reaction is transferred to the circulating gas stream. This gas stream is compressed and cooled in an external recycle line
Data Source
Figure 1~2
Figure 3
AI summary
A process for producing polyethylene polymers including contacting ethylene and at least one C3 to C8 alpha-olefin comonomer with a polymerization catalyst on a particulate support in a fluidized bed polymerization reactor under conditions effective to polymerize at least part of the ethylene and comonomer and produce the polyethylene polymers, wherein the support has a d10 particle size as measured by laser diffraction of at least 18 microns, is provided.