Maximizing Capture Rate

September 18, 2002

The unique fine filtration and capture rate characteristics of the Vincent Fiber Filter have resulted in successful operation in pineapple juice and paper mill shower water applications. The same principle is used in both these two very different installations.

The Fiber Filter separates a sludge of fiber from the flow admitted into the filter machine. Usually the goal is to produce a firm, bulky sludge in order to (a) maximize yield of filtrate and (b) facilitate handling of the sludge.

In other applications the goal is to maximize the capture rate. That is, the need is to have as high as possible a percentage of suspended solids captured in the sludge discharge. Usually this is achieved by simply installing filter sleeves with smaller micron openings. However, because tighter weave fabric results in lower gpm capacity, this is not always practical - nor necessary.

Another way of achieving high solids capture in a Fiber Filter is to reduce the consistency of the solids in the sludge discharge. Reducing the elevation angle of Fiber Filter, other things remaining constant, will result in a watery sludge discharge, along with a higher capture rate.

In the case of pineapple mill juice, excessive wear and poor capacity was being experienced with a centrifuge that is used to filter the juice. A Fiber Filter was added in series, ahead of the centrifuge. This Model FF-12 sees a feed of 100 to 120 gpm, and 118 and 190 micron sleeves are used. Filtrate from this Fiber Filter now goes to the centrifuge. Increased centrifuge capacity and decreased maintenance have been achieved.

The elevation of the Fiber Filter is kept low, resulting in a low consistency sludge discharge of about 5 to 10 gpm. This flow, which contains the majority of the suspended solids, is sent to a decanter. This decanter works well in separating good juice from the sludge.

The second similar application is in filtering shower water used on a paper machine. This shower water keeps the paper machine clean so that the sheet of paper forms and separates, at high speed, without blemishes or tearing. Trash material cannot be conveyed to the paper machine in the shower water, nor should particles large enough to plug the nozzles be present.

In practice it was found that a milkshake-thick 0.5 gpm flow of sludge could be produced by the Fiber Filter. This was with 31 micron sleeves and flow of 200 gpm, with 70 ppm suspended solids in the feed flow. By reducing the elevation, the sludge discharge jumped to 5 gpm. The important part was that the capture rate improved, with the solids in the filtrate dropping from 30 to 18 ppm. The change in waste discharge, from 0.5 to 5 gpm, is insignificant in the overall operation of a paper mill.

Issue 131