Disc Filter Secondary Flow for Stable Fiber Dewatering
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Solution Overview
Problem
Disc filters used in the pulp and paper industry face efficiency decreases with increasing freeness of cellulose fiber suspensions due to fiber mat falling back into the suspension, caused by rapid filtrate removal leading to thickened suspension, mechanical scraping, and vacuum loss.
Innovation Solution
Incorporation of injectors to introduce a secondary flow of liquid, such as water or fiber suspension, into the disc filter to promote dilution and agitation, reducing suspension thickening and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid filtrate removal is used to improve dewatering efficiency, then water is removed from suspension faster, but fiber mat falls back into suspension and vacuum is lost
Solution Approach 1:
The patent applies preliminary anti-action by introducing a secondary liquid flow before the harmful effect occurs. The secondary flow counteracts suspension thickening and mechanical scraping effects that would otherwise cause fiber mat to fall back and vacuum to be lost, thereby preventing the deterioration of filtration efficiency
Solution Approach 2:
The patent uses an intermediary substance (secondary liquid flow) to mediate between the filtration process and the suspension. This intermediary flow dilutes the suspension and reduces mechanical scraping, allowing rapid filtrate removal to continue without causing fiber mat collapse and vacuum loss
2Productivity
If filter elements rotate through suspension to separate fiber, then water is extracted through filtering lining, but suspension thickens causing mechanical scraping
Solution Approach 1:
The secondary liquid flow acts as an intermediary that reduces the harmful mechanical scraping effect. By diluting the suspension and reducing its viscosity, the secondary flow minimizes the mechanical scraping action on the fiber mat while allowing continuous fiber separation to proceed
Solution Approach 2:
The patent changes the physical parameters of the suspension by introducing secondary liquid flow. This changes the suspension concentration and viscosity, reducing mechanical scraping effects while maintaining the fiber separation process
3Reliability
If injectors introduce secondary liquid flow to dilute suspension, then suspension thickening is reduced, but device complexity increases
Solution Approach 1:
The secondary liquid flow system serves multiple functions: it dilutes the suspension, reduces mechanical scraping, prevents fiber mat collapse, and maintains vacuum stability. By combining these functions into a single injector system, the patent reduces overall device complexity while improving reliability
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 secondary flow mitigates the effects of suspension thickening, maintaining vacuum and preventing fiber mat damage, thereby enhancing the disc filter's separation efficiency.
Implementation Method 1
Incorporation of injectors to introduce a secondary flow of liquid, such as water or fiber suspension, into the disc filter to promote dilution and agitation
Implementation Method 2
Incorporation of injectors to introduce a secondary flow of liquid, such as water or fiber suspension, into the disc filter to promote dilution and agitation
Implementation Method 3
water is sucked from the suspension, through the filtering lining on the filter sectors and into the flow channels inside the filter sectors, while fiber material is deposited as a fiber mat on the external surfaces of the filtering lining
Implementation Method 4
the filter sectors move out of the suspension and past spray nozzles, which direct jets of fluid towards the fiber mat to thereby loosen the fiber mat from the filtering lining
Data Source
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AI summary
Disclosed herein are disc filters for dewatering a fiber suspension. According to a first aspect, the disc filter includes a vessel comprising an inlet positioned in a wall of the vessel, the inlet introducing a fiber suspension into the vessel. The disc filter further includes a rotor shaft comprising a shaft axis of rotation positioned in a shaft plane, wherein the shaft plane is a horizontal plane. At least one filter element may be coupled to the rotor shaft. At least one injector may be positioned in the wall of the vessel, the at least one injector introducing a secondary flow of liquid into the vessel. The at least one injector may be located in the wall of the vessel at an injector elevation angle on that is greater than -44 degrees and less than or equal to +22 degrees relative to the shaft plane.