Pumped Citrus Peel

April 14, 1998

Last month Vincent presented a paper at the Citrus Engineering Conference of the ASME. This paper, Pumped Peel - Five Years Later, discusses advances in citrus peel processing technology.

In 1940 Dan Vincent was awarded a patent covering the mixing of hydrated lime with citrus peel. The lime attacks the peel and makes it possible to dewater it with a screw press. From that day forward the lime/peel chemical reaction was done in reaction conveyors.

It was Brazilian citrus companies that introduced a process whereby the orange peel is pumped and the reaction is completed in tanks. This has the advantages of using pipes and tanks instead of screw conveyors. This technology was the subject of a 1993 paper at the annual ASME conference.

Since then the Florida processors have leapfrogged the Brazilian technology. The greatest advances are attributable to Ralph Cook, best known as the inventor of the TASTE juice evaporator. Cook Machinery did two feedmills (both using Vincent presses!) improving on the pumped peel concept. The major changes were: (a) Better tramp metal separation; (b) Drastic improvement in the reaction tank; (c) The use of pre- presses ahead of the normal "hard" presses; (d) The use of spent caustic (a waste) as part of the liming system; and (e) Using molasses, with no press liquor, as a pumping medium.

In 1997 Vincent contracted to convert a Tropicana feedmill to our own pumped peel technology. The most notable feature is the elimination of the reaction tank: the reaction takes place in the mixing tank and in the pipeline. Another feature is direct (hard) piping the peel from the mixing tank directly to the presses.

It was found that progressive cavity pumps were suitable even when using a low ratio of molasses to peel. This eliminated the need for pre-presses at Tropicana.

The new systems represent a significant simplification of peel processing technology. Initial capital investment and operating maintenance costs have been reduced accordingly.

Issue 75