REFERENCES
125
The vapours from the DT represent a hot stream with high heat content
and moderate temperature, while the vapours from the evaporators have
high heat content and very low temperature. Several hot streams exist with
low heat content and high temperature, such as edible oil stripper vapours,
mineral oil stripper vapours, wastewater evaporator vapours, waste water and
edible oil.
The three large cool streams are miscella from the extractor, solvent to
the extractor and air to the DC. A small cool stream is water from the
solvent–water separator.
A composite hot stream and cool stream curve can be plotted (see
Figure 4.9). The temperature range at which the two curves near each
other (the ‘pinch’ range) is then determined. Ideally, heat recovery devices
should be employed such that cooling water will not be used to cool any indi-
vidual hot stream above the upper end of this pinch temperature range and
steam will not be used to heat any individual cool stream below the lower end
of this pinch temperature range. Using this tool, modern solvent extraction
plants are achieving up to 96% of maximum potential heat recovery in the
solvent extraction process.
References
Kemper, T.G. & Farmer, R.D. (1999) US patent 5 992 050 (to French Oil Mill Machinery
Company).
Kirschenbauer, H.G. (1944)
Fats and Oils
. New York, NY: Reinhold Publishing Corp.,
pp. 122–123.
Schumacher, H.O. (1985) US patent 4 503 627 (to H.O. Schumacher).
Wan, P.J. & Wakelyn, P.J. (1997)
Technology and Solvents for Extracting Oilseeds and
Nonpetroleum Oils
. Champaign, IL, USA: AOCS Press, pp. 14–18.