Mixing Unit Rotor Stator Design for Homogeneous Media Distribution

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Solution Overview

Problem

Existing mixing apparatuses in fiberlines face challenges in achieving even and homogeneous distribution of treatment media within fiber suspensions due to increased flow rates and shorter residence times, leading to inadequate mixing efficiency.

Innovation Solution

A mixing unit with a rotor shaft featuring multiple rotor bodies that counter-rotate to create multiple turbulent flow zones, combined with stator bodies that introduce shear rates and prevent centrifugal separation, ensuring prolonged mixing and homogeneous distribution of treatment media.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the flow rate through the mixing apparatus is increased to meet higher production capacity, then productivity increases, but the residence time in the mixing chamber decreases leading to shorter mixing zones and reduced mixing efficiency

Engineering Contradiction:
Improveproduction capacityVSAvoidresidence time
Core Design Contradiction:
ProductivityVSDuration of action of moving object

Solution Approach 1:

The mixing chamber is divided into multiple mixing zones by introducing additional rotor bodies and stator bodies along the axial direction. This segmentation creates several turbulent flow regions in series, allowing the fiber suspension to undergo multiple mixing stages during its passage, thereby compensating for the reduced residence time at higher flow rates.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent extends the mixing process from a single radial mixing zone to multiple axial zones by arranging rotor and stator bodies sequentially along the axial direction. This dimensional extension increases the total mixing path length and residence time without significantly increasing the chamber volume, thus maintaining mixing efficiency at higher productivity levels.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If multiple rotor bodies are added to create multiple mixing zones, then mixing efficiency is improved, but device complexity increases

Engineering Contradiction:
Improvemixing efficiencyVSAvoidstructure complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The rotor bodies and stator bodies are designed as standardized, interchangeable components that can be stacked in series. Each rotor-stator pair functions as an independent mixing module with the same structural design, allowing for simplified manufacturing and assembly. The modular approach reduces overall device complexity while achieving multiple mixing zones.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

Multiple rotor bodies are mounted on a common rotor shaft, and multiple stator bodies are positioned concentrically around the rotor shaft. This nested arrangement allows multiple mixing zones to be compactly organized within the mixing chamber without requiring separate chambers or complex support structures, thereby reducing device complexity.

Inventive Principle:
Principle #7Nested doll (Nesting)

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 solution enhances mixing efficiency by prolonging the residence time in turbulent flow zones, preventing solid body rotation, and ensuring uniform distribution of treatment media, even at higher production volumes.

Implementation Method 1

the rotor body (11b) being arranged to create turbulence in a turbulent flow zone (208)

Methodology Applied
Scientific EffectTurbulence: Turbulence

Implementation Method 2

the rotor bodies being arranged to counter-rotate. Such a counter-rotation of the rotor bodies will prevent solid body rotation of the fiber suspension and thereby enable good mixing

Methodology Applied
Scientific EffectCounter-rotation:

Implementation Method 3

the stator body having an extension in the radial direction, the rotor and stator bodies being adapted to interact to produce a turbulent flow in between them

Methodology Applied
Scientific EffectShear stress: Shear Stress

Implementation Method 4

avoids a centrifugal effect, separating the normally lighter treatment media (especially when the treatment media is in the gaseous state) towards the center axis of the mixing apparatus and the fiber suspension in a radially outward direction

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP2790823B1Mixing unit for use in a mixing apparatus and a mixing apparatus
Publication Date: 2017.09.27 VALMET AB
  • EP2790823B1 patent drawingFigure 1~2
  • EP2790823B1 patent drawingFigure 3~4
  • EP2790823B1 patent drawingFigure 5a~5c

AI summary

A mixing unit (10) for use in a mixing apparatus (100) for mixing chemicals in liquid or gaseous state into a fiber suspension, which apparatus comprises a housing (101) defining a mixing chamber (102), a first inlet (103) for feeding a pulp suspension to the mixing chamber, a second inlet (104) for feeding treatment media into the mixing chamber, a drive shaft (105) connected to a drive device (106) for rotation of the drive shaft in operation, and an outlet (107) for discharging the mixture of pulp suspension and treatment media, said unit (10) for mixing being adapted to be installed in the mixing apparatus and comprising a rotor (11) comprising a rotor shaft (11a) being arranged to be connected to the drive shaft (105) for, in operation, simultaneous rotation with the drive shaft, at least two rotor bodies (11b, 11c) arranged on the rotor shaft (11a), each having a radial extension, the bodies being arranged to be axially separated from each other along the rotor shaft (11a) and adapted to cooperate so as to form multiple mixing zones. A mixing apparatus comprising the mixing unit.