World Grain - June 2006 - 68

FEATURE: HISTORY OF MILLING TECHNOLOGY PART III

A disc separator manufactured by Carter Day. Photo courtesy of Carter Day.

during the 19th and 20th centuries have included stone removal
by washer and whizzer.
In early machines, pre-cleaned wheat was plunged into
the rising side of a screw rotating in a water tank, conveying
the wheat to a discharge while allowing the higher density
stones to sink. The total immersion had the additional benefit of the agitated water dissolving and washing away mud
balls and surface dirt. However, the wheat absorbed excessive moisture.
A partial solution was to feed the wet wheat into a whizzer,
where beaters on a rotating shaft propel the wheat upwards
against a perforated screen to remove the excess moisture
and scour the individual kernels.
The disadvantages of this system included the need for a
high level of supervision and maintenance, bacterial contamination of the effluent discharge water and the fairly indiscriminate increase in moisture content.
Developments in the mid-to-late 20th century enabled the
replacement of the washer and whizzer by the dry destoner.

The Paddy eliminator, widely used in the rice and oat industries, separated hulled from unhulled kernels by means
of an oscillating deck with complex zig-zag compartments,
which limited its capacity.
In the U.S., Sutton, Steele and Steele, and in Canada, Kipp
Kelly, no doubt inspired by the paddy eliminator, drew air
through a sloping oscillating perforated deck. This greatly
increased the flow rate of the "floating" wheat stream while
stones that remained on the deck were vibrated by the deck
in a counter-flow direction. This provided effective dry stone
removal for the first time.
The simple dry destoner was superseded by the so-called
Gravity Selector, developed by Sangatti in early 1970s. This
machine combined stone removal with a facility for concentrating impurities for more intensive subsequent cleaning.
Also in the U.S., studies were carried out by Glen Fisher
at Kansas State University that led to the development of the
Technovator Grain Tempering Mixer. This machine ensured
that water added to a grain stream was uniformly dispersed
over each and every kernel. The tempering mixer led the way
to provision of a truly controlled tempering system when instrumentation from Chicago, Illinois, U.S.-based Kay Ray
was applied. The Kay Ray moisture control instrument incorporated a cesium source to detect changes in density and
used microwaves to detect water content to a high degree of
accuracy. The Kay Ray equipment was adopted by Simon
and was widely used in sophisticated milling plants.
European engineers soon followed suit and developed
several alternative intensive dampeners and other devices to
achieve similar results. The dry destoner/gravity selector, together with the tempering mixer, finally rendered the washer
and whizzer obsolete and further simplified the operation of
a modern flour milling plant.

FP
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FP SPOMAX S.A .
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Kol isk a 61/63 , POLAND

phone +48 62 592 17 17

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World Grain - June 2006

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