Conical Drum Element Flow Channels for Pulp Screening
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Solution Overview
Problem
Current pulp screening technologies face challenges in efficiently distributing pulp evenly over the screening surface, preventing clogging, and maintaining high screening capacity while effectively removing impurities and preventing flocculation.
Innovation Solution
The drum element for the screen features a conically shaped casing with surface elements and flow channels that decrease in cross-sectional area, combined with foil bits that create pressure pulsations to distribute pulp evenly and prevent clogging, ensuring efficient screening and high capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drum rotors are used in pulp screens, then the screening process can operate continuously, but the pulp distribution over the screening surface becomes uneven and clogging occurs
Solution Approach 1:
The drum element is segmented into multiple flow channels (typically 3-6) arranged circumferentially around the drum axis. Each flow channel receives pulp independently and distributes it along a sector of the screening surface, ensuring even coverage and preventing any single area from becoming overloaded and clogged.
Solution Approach 2:
The flow channels are designed with varying cross-sectional areas along their length, creating different flow characteristics in different zones. The cross-section decreases from the pulp inlet end to the outlet end, generating pressure gradients that optimize pulp distribution locally across the screening surface.
2Productivity
If the drum rotor rotates at high speed to maintain high screening capacity, then productivity increases, but pulp flocculation occurs reducing screening efficiency
Solution Approach 1:
The drum element creates periodic pressure variations in the pulp flow through its rotating flow channels. This periodic action prevents continuous high-speed rotation from causing uniform shear forces that lead to flocculation, instead creating alternating high and low pressure zones that keep pulp fibers separated.
Solution Approach 2:
The flow channel cross-sectional area changes along the length of the drum element, creating varying flow velocities and pressure conditions. This parameter variation prevents uniform high-speed flow conditions that cause flocculation, while still maintaining overall high productivity through optimized flow distribution.
3Productivity
If the flow channel cross-sectional area is large to handle high pulp volumes, then screening capacity increases, but the drum element size and device complexity increase
Solution Approach 1:
Instead of increasing flow channel cross-sectional area in a single dimension, the invention distributes pulp flow across multiple flow channels arranged circumferentially around the drum. This transforms a single large-channel problem into multiple smaller channels, maintaining handling capacity while reducing individual channel complexity and overall drum size.
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 ensures even pulp distribution, prevents clogging, and maintains high screening capacity by utilizing the conical shape and pressure pulsations to effectively separate impurities, enhancing the overall screening process.
Implementation Method 1
flow channels that decrease in cross-sectional area... combined with foil bits that create pressure pulsations to distribute pulp evenly
Implementation Method 2
The cross-sectional area of the flow channels is arranged to decrease from a first end of the flow channels towards a second end of the flow channels... forces pulp from the flow channels to the screening chamber
Data Source
Figure 1~23
Figure 2a~2b
Figure 2c~2d
AI summary
A drum element (11) for a screen (1) for screening pulp. The drum element (11) comprises a first end (11') and a second end (11 ") opposite to the first end (11'), at least one flow channel (25, 25a, 25b) arranged to extend from at least one end (11', 11 ") of the drum element (11) towards an opposite end (11', 11 ") of the drum element (11) for a flow of pulp, and foil bits (29) arranged at an outer circumference of the drum element (11).