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Factory Notes

Twelve Facts For A Better Centrifugal Station

Continuous Centrifugals have been used for many years in the beet and cane sugar industries with some things never changing. This article discusses twelve factors for efficient and good centrifugal station operation. 1.) Good Feeding The good feed of massecuite to the continuous centrifugal is an important factor to the efficient operation of the centrifugal station. The feed must free fall no less then one meter in a single stream. This free fall should accelerate the massecuite to speeds more like the peripheral speed in the landing zone with a feed rope no larger then thirty-five millimeters in diameter. The single stream of a smaller diameter feed rope will turn in the conditioning bowl and spread out to a uniform thickness. An example of a bad feeding system is when the massecuite is falling in multiple streams. When the massecuite flows in multiple streams it does not turn in the conditioning bowl or spread out evenly, but instead puddles at the top of the centrifugal and spills out over the top of the centrifugal causing the centrifugal to run very poorly and to frustrate the operators. 2.) The Optimum Speed The speed needs to be right for the type of massecuite the centrifugal is purging. One of the major problems I have observed in my work is when factories speed up their centrifugal to get higher capacity. Speeding up the centrifugal causes a lower capacity, and leaves factory management asking what happened. The slower the centrifugal is required to turn, the greater the capacity of the centrifugal. To determine the optimum speed you must consult with the factory to determine the maximum safe speed and the run tests at varying speeds. In general, the speed for low raw (low grade) massecuite is 2600 Gs at the basket discharge. High raw massecuite is 1600 Gs at the basket discharge. In Affination machines an additional factor to consider when determining the speed of the basket is the quality of magma. When the magma is good the sugar purges easily and the basket can run at low speeds; when the magma is bad (full of lumps and broken grain) the sugar purges poorly and the basket must run at high speeds. The speed can be from 2000 Gs to 2700 Gs at the discharge of the basket. Again, to determine the optimum speed to purge magma is very difficult; it requires professional help and testing. 3.) Proper Working Screen To obtain the ideal capacity, sugar color, and molasses purity requires tests to find the proper working screens. Professional testing determines the size of the sugar crystals, which helps determine the appropriate size of the slots and the appropriate open space. Ultimately, professional testing results in a high capacity and more efficient running if the centrifuge. The capacity of the centrifugal is directly related to the size of the sugar crystal and the open area of the working screen. An example of how the open area can be related to the capacity of the centrifuge is by changing the screen from a 5% open area to a screen with a 10% open area. These changes in the open area can double the capacity of your centrifuge. Never recycle or save old parts of screen sets to try to make complete screen sets. Always use new and complete working screens from the same set. I recommend that factories

Ted D. Milner

use an old set of working screens to start the sugar mill, then install a new set of screens once the mill has run for a few weeks. Doing this allows the removal of foreign objects and trash left in the factory from maintenance season from the massicuite. Overall the importance of understanding the working screens will result in a more efficient running factory, less recycled loads, lower molasses purities and greater profits. 4.) Good Housekeeping For a smooth running centrifugal station good housekeeping is very important to keep foreign objects and sugar lumps out of the massecuite. A lack of good house keeping allows foreign objects and sugar lumps entering the feeding system causing vibration and poor efficiency of the station. When the centrifugal station is vibrating badly it causes several negative results, the vibrations: shake the sugar off of the screens not allowing the sugar to purge properly; hammering of the bearings resulting in early failure; seal failure; and causes other problems that shortens the life of the centrifuge. 5.) Fully Loaded Basket Understanding the "fully loaded basket" is extremely important in achieving the best operation of the continuous centrifugal, but it is often the most misunderstood term. The term "fully loaded basket" is not the maximum capacity of the centrifugal or the maximum motor load; it is the maximum load the centrifugal will purge with little or no water added while still producing acceptable sugar. In processing low raw (low grade) massecuite wash water should be avoided, water will lower the

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SJ | May 2008

a humus component improving the soil quality (water and nutrient retention / release properties).

Pros & cons of additive based film/bag

Pros: · Much cheaper than starch-based plastics. · Materials are well known. · Does not compete against food use. · These films look, act and perform just like their non-degradable counterparts, except that they are weaker and break down after being discarded. Cons: · Made using fossil fuel (contributes to global warming through the release of carbon dioxide) · Degradation in a sealed landfill is very slow. · Degradation depends on conditions of heat, light, stress, air etc . · No biodegradability established,

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which means cannot be absorb by micro-organisms. Pollution is not visible but exists. · They do not comply with European norms on compostable products. · If mixed with other plastics, the value of recycling is reduced. · For plastic recycling, resin identification code 7 is applicable. · Proprietary additives often include cobalt stearate, which dissociates into toxic cobalt free metal during the degradation process. Garry Smith can be reached at [email protected]

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molasses brix and raise its purity. This graph shows test results that demonstrate the best motor load to run the centrifugal. Part 2 of this article will appear in the next issue of Sugar Journal. Ted D. Milner founded Sugar Technical Solutions, a consulting and design company for the sugar industry. He can be reached at his email: [email protected]

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de todos. El termino de "carga completa en la canasta" que significa la máxima capacidad de la centrifuga, o la máxima carga eléctrica en el motor, el verdadero significado es; la máxima carga de la centrifuga que purgara con poca o nada de agua, mientras sigue produciendo azúcar aceptable. Cuando se procesa mazas de bajo grado tipo "c" el aguan de lavado en la maza debe de evitarse, el agua bajara el grado brix y aumentara la pureza de la miel. Final de la primera parte. Translated by: Luís Rivas, consultant for the sugar industry, Baton Rouge, LA, USA. Email: [email protected]

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