Creating drier solids

Creating drier solids

Xelletor decanter centrifuge from Flottweg Separation Technology

Biosolids dewatering can offer enormous potential savings for operators of sewage treatment plants. Depending on system capacity, 1 percent more dry substance can lead to cost-savings in the five- to six-digit range. With that potential savings in mind, Flottweg Separation Technology has introduced the Xelletor decanter centrifuge, which uses innovative technology to improve dewatering performance, reduce polymer consumption, save energy and maximize capacity.

The key to the device’s dewatering performance is a deeper liquid pool inside the centrifuge, translating to greater volume and higher throughput. The deeper pool enables production of solids that are drier on average by 2 percentage points (for example, 27 percent versus 25 percent for conventional technology).

“The big advantage is that the capacity and the performance of the centrifuge in general are increased, while the external diameter of the centrifuge remains the same,” says Christopher Margilas, Flottweg Separation Technology sales engineer. “Another positive point is that the deeper pool moves the solids discharge closer to the axis of rotation, reducing the energy consumption by up to 25 percent, whereas the capacity is up to 15 percent higher than traditional centrifuges on the market.”

To enable the deeper pool, the scroll that removes the settled solids from the centrifuge uses a tubular space frame design instead of the traditional solid scroll body. This significantly reduces the shear force applied to the flocculated feed, reducing breakage of the floc and enabling an average 20 percent reduction in polymer consumption. In addition, due to the narrow weir diameter, the distance between feed pipe and the pool surface becomes shorter. So, the feed has to overcome a shorter distance and hits the pool surface at a lower circumferential speed. As a result, the friction between incoming product from the feed pipe and the rotating liquid in the bowl is reduced, which results in lower shear forces and polymer demand. The liquid is discharged over a smaller area, which means less energy has to be supplied by the drive motor.

This is in addition to a feature of the company’s basic design that reduces energy consumption by directing the liquid discharge to help rotate the bowl. That yields an additional 25 percent savings, for an overall up to 50 percent reduction in energy consumed. Centrifuges are offered in three models with a total throughput range of 50 to 525 gpm. 859-448-2331;


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