Displaced Peripheral Valve Seals in Drum Pulp Washers
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Solution Overview
Problem
The existing compartmented drum washing arrangements face issues with filtrate separation and mixing across different washing stages, leading to contamination and reduced washing effectiveness due to incorrect placement of seals in the peripheral valve, resulting in capacity and pressure drop problems.
Innovation Solution
The peripheral valve seals are moved in the rotation direction of the drum to ensure correct filtrate collection, allowing for increased channel volume and height, thereby reducing pressure drops and enhancing capacity and washing effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the peripheral valve seals are placed in line with the longitudinal seals defining washing stages, then the valve structure is simple and easy to manufacture, but the filtrate from different washing stages mixes and contaminates each other
Solution Approach 1:
The peripheral valve seals are deliberately displaced asymmetrically relative to the longitudinal seals. Specifically, the first peripheral valve seal is displaced in the rotation direction of the drum relative to the first longitudinal seal, while the second peripheral valve seal is displaced opposite to the rotation direction relative to the second longitudinal seal. This asymmetric arrangement ensures that filtrate channels from different washing stages are correctly directed to appropriate valve sections, preventing mixing and contamination while maintaining a relatively simple valve structure.
2Productivity
If the filtrate channels are made shallow to reduce volume, then the washing apparatus capacity is reduced, but pressure drops in the channels are decreased
Solution Approach 1:
Instead of merely increasing channel depth (one dimension), the solution optimizes the three-dimensional configuration of channels and seals. The displaced peripheral valve seals create optimized channel geometries that account for length, depth, and cross-sectional area simultaneously. This multi-dimensional optimization allows channels to have sufficient volume for high capacity while maintaining adequate cross-sectional area to reduce pressure drops, resolving the contradiction between capacity and pressure drop.
3Reliability
If the peripheral valve seals are displaced in the rotation direction of the drum, then the filtrate collection is improved and contamination is reduced, but the valve structure becomes more complex
Solution Approach 1:
The displacement of peripheral valve seals is applied locally and selectively rather than uniformly across all seals. Each peripheral valve seal is displaced according to its specific position and function: the first seal is displaced in the rotation direction, while the second seal is displaced opposite to the rotation direction. This localized, differentiated approach ensures reliable filtrate collection for each washing stage without unnecessarily complicating the overall valve structure.
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 solution ensures proper handling of filtrate, increasing washing effectiveness and capacity by allowing for deeper channels and improved filtrate separation across different stages, reducing contamination and pressure drops.
Implementation Method 1
The static pressure causes the displaced liquor to pass through a perforated metal sheet mounted on the rotary drum
Implementation Method 2
the filtrate at overpressure is caused to pass through the metal sheet. The increased pressure difference effects an improved dewatering of the pulp
Data Source
Figure 1~2
Figure 3
AI summary
A washing arrangement for washing and dewatering cellulose pulp, comprising a rotary drum (1) with a plurality of external compartments (2) on the drum for the pulp to be washed, which compartments are defined by axial compartment walls (3) distributed along the circumference of the drum, a stationary cylindric casing (8) enclosing the drum, whereby a ring-shaped space is defined between the casing and the drum and where the ring-shaped space by means of longitudinal seals in the axial direction of the drum is divided into a forming zone for forming the pulp in the compartments of the drum, at least one washing zone for washing the pulp at overpressure, and a discharge zone for feeding out the washed pulp, and where the filtrates from different washing stages are collected in a peripheral valve located at the end wall of the drum, where the filtrate stages are separated by seals in the valve, where at least some of the valve seals in the peripheral valve are displaced in relation to the corresponding longitudinal seal, seen in the rotation direction of the drum.