WesTech’s patented EvenFlo™ Feedwell achieves peak performance with its simple two-stage design. It significantly improves the overflow clarity while using a lower polymer dosage.
The thickener or clarifier is the major piece of equipment used to recover water in mineral and industrial processes. The one thing all thickeners have in common, the feedwell, is the core of every thickener’s performance.
A thickener relies on a feedwell for even distribution of solids and flocculation of suspended particles. The feedwell receives the feedpipe flow and transitions it to a slow vertical downward flow, while flocculating the suspended solids into floccules that settle quickly.
Conventional thickener feedwell designs have two main shortcomings: short circuiting, where the feed stream momentum carries the flow prematurely down and around the feedwell, past the shelf and deflector, and out of the feedwell; and inefficient flocculation, where only a small area around the inlet of the feed provides good mixing.
Due to these issues, most sites experience the following problems:
The only real option to overcome these inherent flaws is to increase the polymer dosage and increase the rake torque; both add expense or capacity limitations. A thickener that operates efficiently can actually be an untapped source of lowering plant costs.
WesTech introduced the innovative EvenFlo feedwell technology to efficiently address feedwell problems, without using shelves, vanes, or deflectors.
The two-stage design first uses an inner channel to convert the tangential feed energy into a concentric radial flow that empties into the main feedwell.
In the second stage, the flow exits the inner channel through bottom ports, directing the flow radially outward into the feedwell for optimal mixing of flocculant and solids, uniquely utilizing all area of the feedwell volume, which provides even distribution into the thickener.
This method extends the optimum mixing zone around the full periphery of the outer feedwell, providing the largest consistent mix zone in the industry, and creating an environment to sweep the solids, including hard-to-collect ultra-fines, producing clean overflow and fast-settling floccules.
In addition, the EvenFlo’s outer feedwell provides a very robust, effective self-dilution system, with accelerated dilution using airlift pumping or density differential dilution ports, to return clean water to the feedwell from the clarification zone.
Optimizing your thickener’s feedwell with EvenFlo produces consistent cost savings in two ways:
For slurries that require excessive dilution or may have wide swings in dilution requirements, WesTech provides the AirLift™.
The AirLift dilution system employs the use of air lift pumps. These pumps are located next to the feedwell, spaced around the periphery and their discharge communicates with the feedwell through launders (see the image below). The air lift pump draws up clear water from low in the clarification zone, that does not disturb the surface of the thickener, to dilute and mix with the feed slurry in the feedwell.
WesTech has the full range of feed dilution capability with the self-dilution ports or with the AirLift system to optimize the feedwell operation for any of your thickener needs.
Not only a great solution for new thickeners, the EvenFlo is also an excellent choice for retrofits. Replacing a poorly functioning feedwell with an EvenFlo in an existing thickener or clarifier will eliminate many of your problems and save you money in polymer consumption and other operation costs. You will see a quick return on your investment.
The benefits of retrofitting three 135-meter traction thickeners is shown below; the short-circuiting flow seen in the Before photo is corrected by retrofitting an EvenFlo Feedwell in the thickener in the After photo.
Effective flocculation of the full feed flow provides improved overflow clarity and increased underflow density, all while reducing the flocculant dosage. Three-month averages from before and after retrofitting a primary clarifier show:
EvenFlo's dramatic improvement in optimal mixing intensity, extended duration, and preventing of short circuiting is confirmed with computational fluid dynamics (CFD) analysis and validated by a third-party study by CISRO.
CISRO studied floccule generation as a function of feedwell design and mixing intensity (feed velocity). The floccule growth results were displayed, with optimum flocculation depicted as large red spheres and poor flocculation as small blue spheres. Compare the small, effective flocculation area in the shelfed and deflector feedwells to the large, efficient area of the EvenFlo design.
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Download the calculator to find out how much you could save by installing EvenFlo.