Polymerization Reactor Draft Tube Helical Stirrer Mixing
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Solution Overview
Problem
Existing polymerization reactors face challenges in achieving ideal mixing of reactants across varying viscosities, leading to inconsistent molecular weight distribution and composition, and struggle with scalability without affecting polymer properties.
Innovation Solution
A polymerization reactor assembly with a draft tube and helical stirrer, featuring distinct sections and secondary mixing means, rotates to force reaction mixtures through specific sections, ensuring turbulent mixing and controlled flow direction, which enhances homogeneity and maintains polymer quality across viscosity ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polymerization reactors are used with standard mixing configurations, then the reactor structure is simple and easy to manufacture, but the mixing of reactants is inconsistent leading to poor molecular weight distribution and composition uniformity
Solution Approach 1:
The reactor is divided into distinct functional sections: a draft tube section for downward flow, an outer annular section for upward flow, and a mixing section. This segmentation allows each zone to perform a specific function in the overall mixing process, creating controlled circulation patterns that improve molecular weight distribution and composition uniformity.
Solution Approach 2:
The draft tube acts as an intermediary structure that directs and controls the flow of reactants. By introducing reactants through the draft tube and forcing them to circulate through defined paths, it mediates the mixing process between the inward flow and outward flow sections, ensuring consistent mixing regardless of viscosity changes.
2Productivity
If reactor temperature is increased to achieve faster reaction rates, then productivity increases, but temperature gradients become excessive and control becomes difficult
Solution Approach 1:
The circulation flow pattern creates a self-regulating system where reactants are continuously circulated through the reactor. This continuous circulation distributes heat more uniformly throughout the reaction mixture, preventing excessive temperature gradients and providing better temperature control while maintaining high reaction rates.
3Productivity
If the reactor is scaled up to increase production capacity, then productivity increases, but mixing efficiency decreases and polymer properties become inconsistent
Solution Approach 1:
The segmented design with distinct draft tube and annular sections creates scalable flow patterns. When scaled up, the same circulation principles apply, maintaining consistent mixing efficiency and polymer property consistency across different reactor sizes.
Solution Approach 2:
The reactor utilizes vertical circulation flow in addition to radial mixing, creating a three-dimensional mixing pattern. This multi-dimensional approach to mixing scales more effectively than conventional single-plane mixing, maintaining mixing efficiency as reactor size increases.
4Manufacturing precision
If helical ribbon mixers are used to improve mixing at high viscosity, then mixing effectiveness increases, but the mixers become difficult to control and consume excessive energy
Solution Approach 1:
The system uses fluid dynamics and circulation flows to achieve mixing, replacing the need for high-energy mechanical helical ribbon mixers. The circulation pattern created by the draft tube configuration provides effective mixing through controlled fluid motion rather than intensive mechanical agitation, reducing energy consumption.
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 configuration achieves nearly ideal mixing at both low and high viscosities, maintaining narrow molecular weight distribution and consistent polymer properties, even during reactor upscaling, with reduced circulation times and energy consumption.
Implementation Method 1
ensuring turbulent mixing and controlled flow direction, which enhances homogeneity
Implementation Method 2
The circulation flow is high and circulation times are short. This results in high number of circulations per mean residence time and a relative well back-mixed system.
Data Source
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AI summary
The present invention relates to a process for polymerization of at least one olefin monomer in a polymerization reactor assembly, the polymerization reactor assembly comprising a reactor (1) having a housing (2) defining an inner space (3), the reactor (1) comprising a) at least one inlet (4); b) at least one outlet (5); c) a draft tube (6) having a substantially cylindrical shape and an inner space (7), wherein the draft tube (6) is located within the inner space (3) of the reactor (1) so that an upper opening (10) and a lower opening (11) of the draft tube (6) are fluidly connected with the inner space (3) of the reactor (1), and d) a stirrer (12) located within the inner space (3) of the reactor (1) and comprising a stirrer blade (14) having a helical shape, wherein the axis (8) of the draft tube and the axis (15) of the stirrer blade (14) are coinciding, the stirrer blade (14) extending concentrically with respect to the draft tube (6) and the housing (2) of the reactor (1), and e) secondary mixing means (23) for mixing the fluid inside the reactor (1) by rotating motion, wherein the inner space (3) of the reactor (1) comprises sections A, B, C, and D, wherein section A is the space defined by the upper end of the housing (2) of the reactor (1) and a first plane (10a) oriented transversally to the axis (8) of the draft tube and arranged at the upper end of the stirrer (12), section B is the space defined by the housing (2) of the reactor (1), the outer surface of the draft tube (6), the first plane (10a) and a second plane (11a) oriented transversally to the axis (8) of the draft tube and arranged at the lower opening (11) of the draft tube (6), section C is the space defined by the lower end of the housing (2) of the reactor (1) and the second plane (11a), and section D is the inner space (7) of the draft tube (6), wherein the stirrer (12) is rotatable inside the housing (2) of the reactor (1) to provide a mixing motion to fluids if present inside the reactor (1), the process comprising the steps of I. introducing the at least one olefin monomer, at least one polymerization catalyst, and at least one solvent via the at least one inlet (4) into section C to form a reaction mixture, II. rotating the stirrer (12) to force at least a part of the reaction mixture from section C via section B to section A and from section A via section D to section C, III. thereby polymerizing the at least one olefin monomer forming a polymer in said reaction mixture, IV. withdrawing at least a part of the reaction mixture via the at least one outlet (5) from section A to obtain an olefin polymer as a product.