Disc Filter Agitator Nozzle Configuration for Settling Prevention
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Solution Overview
Problem
Existing disc filters in pulp mills face challenges in preventing the settling of fine lime mud particles, which leads to dense deposits and mechanical issues, as previous agitation systems either fail to prevent settling entirely or impose excessive mechanical stress on particles, reducing filterability.
Innovation Solution
The implementation of a disc filter agitator system with strategically positioned nozzles, including a first nozzle between collection chutes parallel to the filter surface and a second nozzle at a wall orthogonally oriented, creating a coordinated flow that intensifies circulation and minimizes mechanical impact on particles, along with a recirculation system to enhance agitation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single mammoth pump is arranged in the lowermost position of the vat, then some suspension is withdrawn and directed upwardly, but settling is not prevented at outer ends of the vat and the strong upward flow interferes with precoat on adjacent filter discs
Solution Approach 1:
The single mammoth pump is divided into multiple smaller nozzles distributed across the bottom of the vat. This segmentation allows the agitation function to be distributed throughout the entire vat volume, preventing settling at outer ends without creating a single strong upward flow that would interfere with precoat on filter discs.
Solution Approach 2:
Instead of one strong pump creating a uniform flow pattern, multiple nozzles are positioned at different locations (including outer ends) to create localized agitation zones. Each nozzle provides gentle agitation appropriate for its local area, preventing settling without creating excessive flow that would disrupt precoat formation on adjacent discs.
2Reliability
If reciprocating cradle rake is installed in the bottom of the vat, then sweeping action is provided, but dense packed deposits subject the cradle mechanism to very high mechanical load that led to breakdown
Solution Approach 1:
The mechanical cradle rake system is replaced with a fluid-based agitation system using multiple nozzles. Instead of using mechanical sweeping action that creates high loads on dense deposits, the nozzles create fluid flow patterns that gently agitate the suspension and prevent settling without subjecting the system to high mechanical stresses.
Solution Approach 2:
The patent uses hydraulic agitation through multiple nozzles that spray liquid to create circulation patterns in the suspension. This hydraulic approach replaces the mechanical cradle rake system, providing effective anti-settling action through fluid dynamics rather than mechanical contact, thereby avoiding high mechanical loads on the agitation system.
3Reliability
If small paddle members are attached on the outer periphery of the filter discs, then stirring action is brought about close to the bottom wall, but more load on the discs deflects their position causing intersection with the doctor blade which tears up the filter cloths
Solution Approach 1:
The mechanical paddle members attached to filter discs are replaced with a separate agitation system using nozzles positioned in the vat bottom. This substitution removes the additional mechanical load from the filter discs, preventing deflection and intersection with doctor blades that would tear the filter cloths, while still providing effective stirring action through the nozzle spray patterns.
4Reliability
If excessive pumping and agitation is used to prevent settling, then settling is prevented, but particle size is reduced and filterability is radically reduced as the filter may be blocked
Solution Approach 1:
Multiple nozzles are positioned to create localized, gentle agitation zones throughout the vat rather than one strong pump creating intense turbulence. Each nozzle provides mild circulation appropriate for its location, preventing settling through distributed gentle motion that does not excessively reduce particle size or harm filterability.
Solution Approach 2:
Instead of using excessive agitation force throughout the entire vat, the system applies partial agitation action through multiple nozzles. Each nozzle provides just enough local circulation to prevent settling in its vicinity, achieving effective anti-settling action with minimal overall mechanical energy input, thereby avoiding excessive particle size reduction.
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 effectively prevents settling across the entire vat bottom with reduced mechanical stress on particles, maintaining high filterability by establishing a strong, coherent agitating flow that reduces particle size reduction and filter blockage risks.
Implementation Method 1
both the first and second nozzles (31 and 32 respectively) are oriented such that the outflow from the nozzles coincides and are parallel to the semicircular form of the vat... establishing a strong agitating flow
Implementation Method 2
a recirculation system to enhance agitation efficiency... a portion of the filtrate is used as the additional liquid
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an improved agitator system for a vat in a disc filter used to filter out fine particle material in a raw suspension. The inventive agitator system comprises a first nozzle (31) arranged between two collection chutes and between two walls of these chutes that are oriented parallel with the filter surface of the filter disc (12) and a second nozzle (32) is arranged at one of the walls of the collection chute oriented orthogonally with the filter surface of the filter disc, and wherein both the first and second nozzles (31 and 32 respectively are oriented such that the outflow from the nozzles (41 and 42 respectively) coincides and are parallel to the semicircular form of the vat bottom (10a).