Curved Rotor Element for Pulp Screening
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Solution Overview
Problem
Current pressure screens in the pulp and paper industry are limited in achieving high feed consistencies due to clogging issues and energy constraints, which restrict the efficient processing of thicker pulp suspensions.
Innovation Solution
The design of a rotor element with a curved trailing surface and converging sidewalls that minimizes turbulence and stalling, allowing for smoother pulp flow and higher rotational speeds without significant energy increase, enabling the processing of pulp at higher consistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotor rotational velocity is increased to push fibers through apertures, then screening effectiveness is improved, but energy consumption increases intensively
Solution Approach 1:
The rotor element incorporates a curved trailing surface that guides the pulp flow smoothly along its contour, reducing turbulence and energy loss. The curved geometry allows the flow to follow the surface profile rather than creating chaotic eddies, thereby maintaining screening effectiveness while reducing the energy required to drive the rotor at high velocities.
Solution Approach 2:
The invention modifies the geometric parameters of the rotor element by introducing a curved trailing surface with specific radius of curvature. This parameter change optimizes the flow characteristics, allowing the system to achieve effective screening at lower rotational velocities or with reduced energy input, as the curved surface reduces flow separation and turbulence.
2Productivity
If the pulp consistency is increased to process thicker suspensions, then processing capacity is improved, but the apertures in the screen surface or reject line become clogged
Solution Approach 1:
The curved trailing surface of the rotor element creates a smoother flow transition that prevents abrupt flow separation and reduces turbulence-induced clogging. The curved geometry allows the pulp suspension to flow more uniformly over the screen surface, maintaining aperture openness even at higher consistencies where thicker suspensions would otherwise tend to plug the apertures.
Solution Approach 2:
The invention converts the potentially harmful effect of high-consistency pulp flow into a beneficial pattern by using the curved trailing surface to create a controlled flow separation that actually helps clear the screen surface. The curved geometry transforms what would normally be a clogging-prone turbulent flow into a more controlled flow that maintains aperture clearance.
3Productivity
If the rotor element creates strong pressure shock to press accept through apertures, then screening efficiency is improved, but turbulence increases causing energy loss
Solution Approach 1:
The curved trailing surface replaces abrupt angular surfaces that create strong pressure shocks and turbulence. Instead of creating a sudden flow separation at a sharp edge, the curved surface allows the flow to transition gradually, reducing turbulence intensity and associated energy losses while still maintaining sufficient pressure differential for effective screening.
Solution Approach 2:
The curved trailing surface creates a more dynamic and adaptable flow pattern that responds to changes in pulp consistency and flow conditions. The curved geometry allows the flow to adjust more smoothly to the rotor element surface, reducing energy loss from turbulence while maintaining the necessary pressure shock for screening efficiency under varying operating conditions.
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 enhances the processing capacity of pulp suspensions to higher consistencies, reduces energy consumption, and decreases the thickening of rejects, leading to improved operational efficiency and reduced energy costs.
Implementation Method 1
The trailing surface of the rotor element is curved and the sidewalls thereof converge at least along a part of their length towards the back point of the element... minimizes turbulence and stalling
Data Source
Figure 1a~1d
Figure 2a~2d
Figure 3~4b
AI summary
The present invention relates to an apparatus for screening a fibrous suspension. Especially it relates to the construction of a rotor element for the screen. The rotor element comprises a front surface facing the flow, an upper surface and a sloping trailing surface. Its trailing surface is curved and the sidewalls thereof converge at the back point of the element.