Open-Channel Feed Dilution Orifices for Thickener Mixing
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Solution Overview
Problem
Existing feed dilution systems in thickener/clarifier settling tanks, particularly those with open-channel infeed conduits, suffer from incomplete mixing of the influent solids slurry with dilution liquor, leading to non-uniform solid concentrations and reduced settling efficiency due to the dilution liquor flowing along the conduit walls rather than mixing effectively with the solids jet.
Innovation Solution
Incorporating orifices with flow guides in the open-channel infeed conduit, positioned to facilitate momentum transfer between the slurry feed stream and clarified liquid, allowing for effective drawing of clarified liquid into the conduit and enhancing dilution of the slurry feed stream without additional moving parts or system head, thereby improving the mixing and dilution process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an open-channel infeed conduit is used for feed dilution, then the system structure is simplified and maintenance is reduced, but the mixing of dilution liquor with solids slurry is incomplete and non-uniform solid concentrations occur
Solution Approach 1:
The open-channel conduit is segmented into multiple sections with side openings at different positions. Each opening allows dilution liquor to enter the conduit at a specific location, creating multiple mixing zones along the conduit length. This segmentation transforms a single poor mixing zone into multiple incremental mixing stages, achieving uniform solid concentration distribution while maintaining the simple open-channel structure.
Solution Approach 2:
The side openings act as intermediary structures that facilitate the interaction between dilution liquor and solids slurry. By providing multiple entry points for dilution liquor along the conduit, these openings serve as intermediate mixing zones where gradual blending occurs, mediating between the separate streams and achieving uniform mixture at the feedwell inlet.
2Device complexity
If dilution liquor flows along the conduit walls, then the open-channel structure is maintained, but effective mixing with the solids jet is prevented
Solution Approach 1:
The conduit is divided into multiple mixing sections by introducing side openings at different positions along its length. This segmentation prevents the dilution liquor from simply flowing along the walls by creating multiple interaction points, where the liquor is progressively drawn into the conduit and mixed with the solids slurry in staged increments.
Solution Approach 2:
The mixing process transitions from a two-dimensional wall-flow pattern to a three-dimensional multi-zone mixing pattern. By adding side openings at different heights and positions, the system utilizes the vertical and longitudinal dimensions of the conduit to create multiple mixing planes, transforming the flow pattern from wall-parallel to volumetric mixing.
3Manufacturing precision
If orifices are added to the open-channel conduit, then dilution and mixing are enhanced, but the device complexity increases
Solution Approach 1:
The side openings serve multiple functions simultaneously: they allow dilution liquor to enter the conduit, create mixing zones, control flow distribution, and maintain the open-channel structure. This multi-functionality reduces the need for additional specialized components like separate injection nozzles or mixing devices, achieving enhanced mixing without proportionally increasing device complexity.
Solution Approach 2:
The system utilizes the existing flow dynamics and hydraulic gradients within the open-channel conduit to drive the mixing process. The kinetic energy of the incoming solids slurry automatically draws dilution liquor through the side openings without requiring external pumps or complex control mechanisms. The conduit structure itself provides the mixing function through its geometric configuration.
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 solution increases the degree of dilution of the feed stream, reduces hydraulic jumps, and maintains reliability with minimal maintenance requirements, as the orifices in open-channel conduits surprisingly work effectively, unlike in closed tubular conduits, leading to improved settling efficiency and uniform solid distribution across the feedwell.
Implementation Method 1
The orifice is positioned proximate to and in fluid communication with the clarified liquid phase in the tank to draw clarified liquid from the tank into the conduit responsive to or by virtue of momentum transfer between the flow of the liquid slurry feed stream in the conduit and the clarified liquid in the tank.
Implementation Method 2
The eductor structure initially dilutes the slurry feed stream with clarified liquid from the tank.
Implementation Method 3
Thickener/clarifier settling tanks are used in a wide variety of industries to separate influent feed slurry comprising a solids, or particulate material, containing fluid to produce a clarified liquid phase having a lower concentration of solids than the influent feed slurry and an underflow stream having a higher concentration of solids than the influent feed slurry.
Data Source
AI summary
An open-channel infeed conduit of a feed dilution system of a thickener/clarifier settling tank is provided with orifices between its upstream inlet end and its outlet end. The orifices are positioned proximate to and in fluid communication with the clarified liquid phase in the tank to draw clarified liquid from the tank into the conduit responsive to or by virtue of momentum transfer between the flow of the liquid slurry feed stream in the conduit and the clarified liquid in the tank.