Double Cone Reactor for Olefin Polymerization Thermal Homogeneity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fluidized bed reactors face issues with polymer product inhomogeneity due to temperature variations among polymer particles, leading to operational discrepancies and agglomeration, especially with large particles, which affects heat transfer and reactor efficiency.
Innovation Solution
A double cone reactor design with a top zone of decreasing cross-sectional diameter, a middle zone of constant diameter, and a bottom zone of increasing diameter is used, ensuring the polymer particle temperature does not exceed 120% of the operating temperature set point, enhancing thermal homogeneity and heat transfer rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional fluidized bed reactors operate at moderate superficial gas velocity values, then gas-solids mixing efficiency is improved and solids carryover is limited, but temperature variations between polymer particles increase leading to product inhomogeneity
Solution Approach 1:
The reactor is divided into distinct zones (bubbling zone, emulsion zone, transition zone) with different flow characteristics and heat transfer properties. The bubbling zone provides intense mixing while the emulsion zone maintains thermal homogeneity, allowing each zone to optimize for its specific function rather than requiring uniform conditions throughout the entire reactor
Solution Approach 2:
The fluidized bed is segmented into multiple functional regions with different gas velocity profiles and particle concentration levels. This segmentation allows simultaneous achievement of good mixing in the bubbling zone and thermal homogeneity in the emulsion zone, resolving the contradiction between mixing efficiency and temperature uniformity
2Stability of the object's composition
If heat transfer rates from polymer particles to gas phase are increased, then polymer product homogeneity is improved, but large particles form agglomerates due to insufficient heat removal
Solution Approach 1:
The transition zone acts as an intermediary region between the high-velocity bubbling zone and the low-velocity emulsion zone. This intermediate region provides gradual acceleration of gas velocity and gradual change in particle concentration, allowing smooth transition of particles without sudden thermal shocks that would cause stickiness and agglomeration
Solution Approach 2:
The reactor operates with dynamically varying gas velocity profiles across different zones and time. The gas velocity is highest in the bubbling zone for intense mixing, then transitions through the transition zone, and is lowest in the emulsion zone for thermal homogeneity. This dynamic velocity profile allows the system to achieve both good mixing and thermal control without causing particle agglomeration
3Temperature
If polymer particles are maintained at controlled temperature not exceeding 120% of set point, then thermal homogeneity is improved and agglomeration is reduced, but reactor design complexity increases
Solution Approach 1:
The reactor uses the fluidization process itself to achieve temperature control without external intervention. The gas flow patterns and particle circulation within the fluidized bed naturally create the temperature gradients and heat transfer conditions needed to maintain thermal homogeneity. The system self-regulates temperature through its own hydrodynamics rather than requiring external cooling/heating systems
Solution Approach 2:
The reactor achieves temperature control by changing the gas velocity parameter across different zones. By varying the superficial gas velocity from high in the bubbling zone to low in the emulsion zone, the system controls heat transfer rates and particle residence times, thereby maintaining thermal homogeneity through parameter optimization rather than structural complexity
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 design achieves a narrow particle size distribution and increased homogeneity of polymer products, reducing agglomeration and operational challenges, allowing for higher production throughput and improved control over polymer quality.
Implementation Method 1
polymerizing at least one olefin in the presence of a polymerization catalyst in the fluidized bed formed by particles of a polymer of the at least one olefin suspended in an upwards flowing stream of the fluidization gas
Implementation Method 2
temperature variation between the polymer particles in a fluidized bed reactor, as a result of limitations in heat transfer from the polymer particles to the reaction medium (gas phase)
Data Source
AI summary
The present invention relates to a process for polymerizing at least one olefin in gas phase in a fluidized bed in a polymerization reactor having a top zone of a generally conical shape as such that the equivalent cross-sectional diameter is monotonically decreasing with respect to the flow direction of the fluidization gas, a middle zone in direct contact with and below said top zone of a generally cylindrical shape and a bottom zone in direct contact and below said middle zone and of a generally conical shape as such that the equivalent cross-sectional diameter is monotonically increasing with respect to the flow direction of the fluidization gas, comprising the steps of: a) introducing a first stream of fluidization gas into the bottom zone; b) polymerizing at least one olefin in the presence of a polymerization catalyst in the fluidized bed formed by particles of a polymer of the at least one olefin suspended in an upwards flowing stream of the fluidization gas in the middle zone; c) withdrawing a second stream comprising the fluidization gas and optionally particles of a polymer of the at least one olefin from the top zone; characterized in that the temperature of the particles of the polymer of the at least one olefin in the fluidized bed (TPP) does not exceed 120% of the operating temperature set point (TS) of the polymerization reactor, wherein TPP and TS are both given in ° C., and the use of said process for polymerizing an olefin homo- or copolymer having a narrow particle size distribution.