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| Courtesy of J.Daigle (Lula-Westfield) |
(Amended 8/17/05)
The following parameters can be used for maintaining good operation of vacuum mud filters.
| For a properly operating filter: |
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% Pol in filter cake |
1.5 -3.0 |
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% Humidity in filter cake |
75-80 |
| Vacuum: |
High = 15-20”; |
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Low = 6-8” |
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| Cake thickness |
1/4-1/2 “ |
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| Temperature of wash water |
175°F |
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| Speed of Rotation (estimated) |
= 1 rotation in 2-6 min for
10' diameter drums |
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= 1 rotation in 3-9 min for
8’ diameter drums |
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| Bagacillo |
20-30 lbs/ton of cane |
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| Wash water % mud |
150% |
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If the sucrose in filter cake is high, the following simple checks should be made:
VACUUM: Low vacuum should be from 6-8 inches; High vacuum from 15-20 inches
The purpose of the low vacuum is to allow the cake to form on the screens. The purpose of the high vacuum is to permit washing and drying of the cake. If the low side vacuum is inappropriate, cake will not form or it will be too thin. If the high side vacuum is too low, the washing and drying of the cake will be poor, producing high pol in mud.
WASH WATER: Water pressure should be between 30-40 psi to enable the nozzles to work properly, covering all areas of the filters. A lower pressure reduces the area covered by the spray and can produce streams rather than sprays, removing the mud from the filter. Water temperature is also important. Too low a temperature allows microbial growth (Leuconostoc) and too high a temperature melts sugar cane wax.
NOZZLES: All should be operating correctly. A strainer on the water supply is necessary.
BAGACILLO: An excess of bagacillo produces thicker filter cake and more mud. With constant bagacillo addition, cake thickness is controlled by speed of rotation.
MUD TOO SOFT: The texture of the mud affects % pol in cake. It is more difficult to remove sucrose from soft mud. Soft mud is usually caused by difficulties in clarification and, when it occurs, the cause should be investigated.
WASH WATER % FILTER CAKE: The ideal quantity of wash water is 150% on filter cake. Lower values can produce higher pol loss. Higher values usually have little effect. When the water runs off the surface, it is an indication that the filter cake will not accept more water.
If the filter operator routinely checks the listed parameters, good work may be obtained from the filters and sugar loss can be minimized. Problems at the filter station can also act as an early warning of clarification difficulties.