Pumped Peel

June 16, 1997

Traditionally screw conveyors have been used to convey citrus waste from the juice extraction building through the feedmill. The waste is mostly orange peel, and it is dehydrated and pelleted into animal feed in the feedmill.

About ten years ago Brazilian citrus juice concentrate producers developed a technology to replace the screw conveyors by pumping the peel from extraction to the feedmill. They used a ratio of one part peel to two parts press liquor to liquify the peel prior to pumping. Moyno progressive cavity pumps were used. (The press liquor is the liquid separated from the peel with screw presses.)

This technology was improved two years ago by the Cook Machinery Company. They designed and built a citrus feedmill (using Vincent VP-22 presses) that pumps the peel in the ratio of only one part peel with one part molasses. (The molasses are made from press liquor in a Cook evaporator.)

During the last month a Vincent designed and installed pumped peel system has undergone trials at a Tropicana feedmill. Here the peel is pumped in a ratio of two parts peel to one part molasses. A new design Geremia moyno pump was imported from Brazil to do the pumping.

The Tropicana project has proven remarkably successful. The mixing tank, pump, and pre-presses have performed with minor hitches under a wide range of adverse conditions. The 10" piping burst on occasions; however, the addition of a pressure relief by-pass has solved the problem.

Before peel can be pressed, it must be reacted with lime in order to break down the cell walls. At Tropicana this lime reaction is done in a Keller mixing tank and in the pipeline. The existing 4' diameter by 96' long reaction conveyor is bypassed.

Probably the most innovative feature of the Tropicana system is that the peel is hard piped (under pressure, without a vent) directly to the presses. Two pressing options are being tested. In one, the peel is pumped to a Model KP- 16 for pre-pressing the loose liquid from the peel. The cake from the KP-16 is then pressed again in a heavy duty Model VP-22.

The second option allows for the peel to be pumped directly into a Model VP-22. High capacity runs have been made with pressures up to 50 psi in the inlet hopper, producing press cake with 67% moisture content. The moisture content would have been even lower, but only 30º Brix molasses were available.

Both options work. The use of the KP pre-press appears to relieve problems when it is necessary to process bad (old, underreacted, or underlimed) peel. Further testing and evaluation will continue through June.

We hope to present a paper on this technology at next year's Citrus ASME meeting.

Issue 62