Centrifugal Feedwell Clarifier Flow Distribution
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Solution Overview
Problem
Conventional clarifier feedwell designs result in high velocity variations and angular momentum, leading to turbulent flow and inefficient settling in clarifiers due to tangential feed, dual counteracting streams, and tall feedwell heights, which disrupt the quiescent flow required for effective separation.
Innovation Solution
A feedwell design utilizing a tangential inlet proximate the center of the feedwell roof to impart centrifugal force for uniform flow distribution, combined with a continuous sidewall and baffles to minimize angular momentum and fluid shear, ensuring low average fluid speed and controlled vorticity within the clarifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If tangential feed is used to introduce influent into the clarifier, then the influent can be introduced into the tank, but high angular momentum is added to the clarifier which disrupts overall clarifier flow by short-circuiting the flow field
Solution Approach 1:
The feedwell is segmented into multiple feed points arranged circumferentially around the central axis, with each feed point introducing influent at a different angular position. This segmentation distributes the angular momentum inputs throughout the feedwell volume, allowing them to cancel each other out and prevent the development of significant net rotation in the discharged flow.
Solution Approach 2:
The feedwell employs asymmetric feed point positioning and potentially asymmetric internal geometry to disrupt the formation of coherent rotational flows. By introducing feed at non-uniform angular intervals and using asymmetric baffle arrangements, the design prevents the symmetric reinforcement of angular momentum that would occur with uniform tangential feeding.
2Stability of the object's composition
If dual counteracting identical tangential feed streams are used, then angular momentum is canceled, but flow bias within the unit is exacerbated so that overall flow improvement is minimal
Solution Approach 1:
Different feed points around the circumferential array are given different local characteristics, including variations in feed flow rates, feed angles, and positioning heights. This local differentiation ensures that no single feed stream dominates the flow pattern, and the cumulative effect produces uniform axial discharge without the flow bias problems of identical counteracting streams.
3Stability of the object's composition
If relatively tall feedwell is used for flow settling purposes, then flow settling is improved, but when the clarifier is operated with liquor fluid surface below the feed height, a waterfall is created which adds unwanted turbulence and entrains air into the fluid
Solution Approach 1:
The discharge mechanism transitions from a vertical waterfall flow (one-dimensional free fall) to a controlled radial or axial discharge through optimized outlet geometry. The feedwell outlet is designed to discharge flow horizontally or axially along the tank periphery rather than allowing it to cascade vertically, eliminating the waterfall effect and its associated turbulence and air entrainment while maintaining effective flow settling through the segmented feed approach.
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 achieves a more uniform and axial flow pattern within the clarifier, reducing fluid shear and vorticity, thereby enhancing the efficiency of solid settling and clarifier performance by minimizing turbulence and air entrainment.
Implementation Method 1
centrifugal force of a spinning fluid is used to spread the influent feed into one having a more uniform flow distribution. In one aspect of the invention, this spin is added to the influent via a tangential feed proximate the center of the feedwell roof.
Implementation Method 2
the influent is fed along the underside of the roof from an inlet that is located proximate the central axis to form a fluid flow that is substantially uniformly disposed around the central axis and flows substantially radially outward from the central axis along and below the underside of the roof toward and substantially parallel to the inside portion of the wall member
Data Source
AI summary
Apparatus and methods are provided for controlling influent feed to produce a substantially uniform flow to a clarifier tank (2) to thereby enhance the settling efficiency within the clarifier. The apparatus comprises a feedwell (24) having a roof (26) and continuous sidewall (28) that together define a feedwell main body enclosure. Influent is fed via a relatively inboard tangential feed mechanism (108) to the inside of the roof (26) from an entry point proximate the center of the roof (150). Influent energy is properly distributed via the action of centrifugal force to generate a uniform axial flow within the feedwell main body which, in turn, is fed into the clarifier tank. Optional baffle members (152, 158) may be provided in the housing to slow angular momentum of the influent which, due to its original feed location, would necessarily be at a relatively low level.