Gas-Solids Reactor Jet Gas Injection for Polyolefin Production Split
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Solution Overview
Problem
In multi-stage reactor assemblies for polyolefin production, achieving control over production split in favor of the gas-solids olefin polymerization reactor without decreasing throughput is challenging, particularly with catalyst systems exhibiting fast decaying activity.
Innovation Solution
Introducing a fluidization gas stream at a point above the distribution plate but below the top end of the gas-solids olefin polymerization reactor, which destroys axially moving powder fountains and generates strong centrifugal forces to separate gas from solids, thereby increasing the production split.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional gas-solids fluidization bed reactors are used with bubbles distributed all over the fluidized bed, then the reactor operates with a certain mixing regime, but the bed level can only be up to a certain height without significantly increasing entrainment of solids, limiting the filling degree and average bulk density of the fluidized bed
Solution Approach 1:
The fluidized bed is segmented into a lower fluidized bed zone and an upper dense phase zone separated by a distributor plate. This segmentation allows the lower zone to maintain fluidization with bubbles for mixing and mass transfer, while the upper zone maintains high bulk density with minimal entrainment, thus resolving the contradiction between maintaining mixing regime and increasing filling degree.
Solution Approach 2:
The distributor plate acts as an intermediary element between the lower fluidized bed zone and the upper dense phase zone. It distributes the upward gas flow uniformly, creating a clear separation between the zones. This intermediary structure enables the system to achieve both good mixing in the lower zone and high bulk density in the upper zone without excessive solid entrainment.
2Adaptability or versatility
If long polymerization times are used in the pre-polymerization reactor and loop reactors (at least 1.5 h), then the production process can accommodate catalyst systems with fast decaying activity, but the catalyst activity is already decreased before reaching the gas-solids olefin polymerization reactor, limiting the production split control
Solution Approach 1:
The invention changes the operating parameters of the gas-solids reactor by creating a two-zone configuration with different gas velocities and residence times. The upper dense phase zone has longer residence time and higher bulk density, which compensates for the catalyst activity decay that occurred in previous reactors, enabling better production split control even with fast-decaying catalysts.
3Productivity
If the bed level is increased to improve reactor productivity, then more polymer can be produced, but solids entrainment into the disengaging zone increases significantly, causing fouling and possible blockage of downstream components
Solution Approach 1:
By segmenting the reactor into two distinct zones with different functions, the system can increase the overall bed level and productivity while the upper zone specifically prevents solid entrainment. The segmentation allows each zone to optimize for its specific function without compromising the other.
Solution Approach 2:
The disengaging zone is extracted and separated from the main fluidized bed by the distributor plate. This extracted zone specifically handles the separation of gas and solids, preventing fouling of downstream components while allowing the main bed to operate at higher levels for improved productivity.
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 allows for an increased production split of the gas-solids olefin polymerization reactor without reducing reactor throughput, improving bulk density and reducing particle carry-over, leading to enhanced reactor productivity and operability.
Implementation Method 1
introducing a jet gas stream through one or more jet gas feeding ports in a jet gas feeding area of the middle zone at the dense phase in the middle zone of the gas-solids olefin polymerization reactor... generates strong centrifugal forces to separate gas from solids
Implementation Method 2
introducing a fluidization gas stream into the bottom zone of the gas-solids olefin polymerization reactor... polymerizing second olefin monomer(s) in the presence of the polymerization catalyst and the first polyolefin to a second polyolefin in a dense phase formed by particles of said second polyolefin suspended in an upwards flowing stream of the fluidization gas
Data Source
AI summary
A process for the production of polyolefins comprising: feeding a slurry comprising at least one polymerization catalyst, at least one carrier liquid, first olefin monomer(s) and optionally at least one first comonomer into at least one loop reactor; polymerizing the first olefin monomer(s) and optionally the at least one first comonomer yielding a first polyolefin; withdrawing the first polyolefin from the loop reactor; feeding the first polyolefin to a gas-solids olefin polymerization reactor, wherein the gas-solids olefin polymerization reactor comprises: a top zone; a middle zone, which comprises a top end in direct contact with said top zone and which is located below said top zone, the middle zone having a generally cylindrical shape; and a bottom zone, which is in direct contact with a bottom end of the middle zone and which is located below the middle zone; introducing a fluidization gas stream into the bottom zone of the gas-solids olefin polymerization reactor; polymerizing second olefin monomer(s) and optionally at least one second comonomer in the presence of the polymerization catalyst and the first polyolefin to a second polyolefin in a dense phase formed by particles of said second polyolefin suspended in an upwards flowing stream of the fluidization gas in the middle zone; introducing a jet gas stream through one or more jet gas feeding ports in a jet gas feeding area of the middle zone at the dense phase in the middle zone of the gas-solids olefin polymerization reactor; withdrawing the second polyolefin from the gas-solids olefin polymerization reactor.