Prelimer suspended solids can be separated. - ASSBT Proceedings

plants that utilize the conventional separation of precipitated suspended solids after 1 st
carbonation, where sedimentation in a clarifier is fo llowed by fi ltration of the
concentrated sludge, testing of OUI system on a full plant scale required an extra piece of
equipment--another clarifier. With proper piping plant operators can gradually switch
filtration from the conventional processing to our new process wi thout additional filters,
but two clarifiers are needed during the switchover. The fonowing list of steps compares
the conventional process with our new Prelimer separation system:
Conventional ] st Carb Separation
l. Raw juice to Pre]jmer
2. Prelimer effluent to Main Limer
"J. MainLimer to 1st Carb
4. 1st Carb effluent to clarifier
5. Underflow to fi Itration
6. Overflow & filtrate to 2nd Carb
7. 2nd Carb to filtration
8. Fihrate to sulfitation
9.
10.
11 .
N w Prelimer Solids Separation
Raw juice to Pre]jmer
Pre]jmer effluent treated
Treated emuent to clarifier
Underflow to filtratIOn
Overflow & filtrate to Main Limer
Main 1imer to 1 st Carb
1 st Carb to clarifier
Underflow recyled to Prelimer
Overflow to 2nd Carb
2nd Carb to flitratlOn
Filtrate to sulfitation
Please note that it very well may be that double carbonation will not be necessary,
because ofthe elimination ofimpurities at the preli mer and the fact that the juice to the
1st carbonation is clear.
Whenever work was done at any ofthe sugar plants, the first order ofbusiness was to do
some lab scale testing. These tests were to establish the effectiveness of the polymer
additions at the glven time and place. All sedimentation tests were conducted using a
500 ml graduated cylinder. A well stirred sample was poured into the cylinder filling
same to the 500 ml mark. Ifany treatment was to be added to the sample it was
introduced into the cylinder prior to adding the juice sample (however, we found Ilttle or
no difference when the treatment was added afterward) The sampJe was then m ixed in
the cylinder using a coited wire stirrer that was passed up and down throllgh the sample
several times. After the stirrer was removed a stop watch was started and the time
requi red for the interface (between the sludge level and the clear supernatant) to reach
the various levels in the cylinder was noted and recorded (for instance, the 450 ml level.
then the 400 mllevel etc.). By graphing the time required versus the cylinder level one
can compare untreated settling rates against various treatments employed. Because of
the turbulence caused by stirring in the cylinder, a sma ll amount oftime is required to get
the interface ofthe sludge level established. This causes a curvature in the upper part of
the time versus interface graph. While this does not cause much of a problem in
comparing graphs, the turbulence effect can be eliminated by extending the constant
settling rate straight line of the curve back ~ard and moving the entire graph till the
extension passes through zero time and 500 ml. Three or four of the settling rate curves
may be superimposed on a single graph fo r easy direct comparison of treatments.
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