K-Patents SeedMaster 2 - Manual (Page 15)

3 THE SEEDMASTER 2 CRYSTALLIZATION TRANSMITTER … 15
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Fig. 3.2 The SeedMaster 2 enclosure
(Display: supersaturation and crystal content)
3.3 Principle of operation
Contrary to commonly used sensors that measure massecuite parameters only indirectly linked to the really
important ones (supersaturation and crystal content), SeedMaster 2 was designed to provide information on-
line on all of the parameters which are important for the up-to-date control of crystallization.
Its operation is based on the use of the K-PATENTS process refractometer, which became the workhorse of
different industries, including sugar, when accurate on- and in-line measurement of liquid concentration is a
must. Syrup / mother liquor concentration data are not disturbed by the presence of crystals, steam and
vapour bubbles and the colour of the liquid. At the same time the refractometer provides data on massecuite
temperature as well. This means that data on C and T (concentration and temperature) in Eq. 1. are directly
provided by the refractometer. Though not advised, it is possible to use a separate temperature probe and
transmitter, too. Besides these data information on mother liquor purity Q is also required for the on-line
calculation of supersaturation.
Mother liquor purity is equal to feed syrup purity only up to the point of seeding. When the crystals begin and
continue to grow, mother syrup purity begins to drop accordingly. It is therefore not constant during the strike,
and should be calculated on-line together with changing crystal content. This, however, needs the use of
additional on-line data (“Third input”) from some already existing sensor (density, massecuite solids content
(brix), or stirrer motor consumption).
NOTES:
1. The use of stirrer motor power or current consumption as “Third input” is limited to batch vacuum
pans operating without strike cut(s), that is without discharging some part of the massecuite before
the end of the strike. The trend of motor consumption data should look like one of those shown in
Fig. 7.5 or Fig. 7.6.
2. As a last resort, if none of these sensors is available, a single data from the laboratory (updated
from time to time) on crystal content (% by volume) when dropping the charge (vacuum pans
operating in batch mode without strike cut(s)) can be used.
Finally, it is well known that feed syrup quality, characterised by its “m”, “b” and “c” parameters can show
considerable changes, which have to be taken into account when calculating the massecuite parameters.
Syrup quality parameters should be determined by the local laboratory (see: APPENDIX). If it is not possible,
data typical for beet and cane syrups are available. Besides these some additional laboratory data are also
required.
SeedMaster 2 operates in two different modes:
1.
in “Stand-by mode” it is waiting for the start (“activation”) of a new strike (vacuum pans
operating in batch mode);
2. in “Active mode” it is carrying out all of the calculations and operations it was designed for
(batch vacuum pans and continuous crystallizers).