| The GOST 21-78 Standard for white sugar sets forth quite high requirements to its quality, including humidity, which shall not exceed 0,14%. Such humidity of white sugar meets the conditions of maintaining its quality when storing in 50-kg sacks at the temperature of 20 to 250Ñ nd relative air humidity of 55 to 70%.
However, when sugar is stored in bulk in silo, sugar shall meet some other requirements:
- humidity – 0,02 to 0,05%;
- permanent temperature during loading – 20 to 250Ñ;
- permissible coloration – not more than 1,0°St;
- ash content – up to 0,01%.
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In order to reach required humidity (for bulk storage), a portion of bound moisture shall be additionally extracted from sugar. Presence of bound moisture in white sugar not only worsens its qualitative parameters, but can also cause its cementation during storage.
Bound moisture is present in the mother liquor film on white sugar grains. Development of bound moisture is caused by re-crystallization of sucrose of the mother liquor film during white sugar drying. This development of bound moisture depends on sugar dying and cooling conditions, and on the design features of dryers and coolers.
There are various methods of sugar drying in the sugar industry, therefore different types of dryers have been developed. The plate dryer is the oldest type. It's a vertical cylindrical vessel, which incorporates a central shaft with circular plates on it. The drum dryer is the most common type. It's a horizontal cylindrical drum with internal arrangements. In the early 70-s, dryers with fluidized layer have been created, where sugar was constantly kept suspended by a flow of the drying agent.
Nowadays, a lot of attention is paid to extraction of bound moisture. Basic researches in this field are aimed at improvement of technology and drying process, as well as at storage of white sugar.
The «TEPLOCOM» Company has developed some original solutions, which guarantee the required sugar humidity (for bulk storage) for various types of dryers.
For example, the Company has developed the technical documentation on upgrading the most common drum dryers. It's the «TEPLOCOM» Company's «know how», which allows performing sugar drying and cooling in one unit.
Another original solution is a high-performance device for sugar dust catching according to the «wet Venturi scrubber» type.
Application of these solutions, combined with development of diagrams and optimal operation modes of dryer-and-cooler complexes, as well as with improvement of aspiration systems, allows reaching positive results in environmental and economical directions.
Efficiency of upgrading the sugar dryer-and-cooler complexes, using the upgraded dryer and scrubber designed by «TEPLOÑOM», has been confirmed by their successful operation at many sugar mills, where the following parameters of the dryer-and-cooler complex operation have been considerably improved:
- yield of ready sugar, meeting the requirements of bulk storage in silo (temperature 20 to 250Ñ, humidity 0,03 to 0,05%);
- increased productivity by 1,5 times on the existing equipment at minimum capital outlays;
- efficiency of purification of used air, extracted from the drying-cooling drum, up to 99,5%;
- decreased sugar losses(~ by 10%) due to lowering the losses with emissions to atmosphere;
- saving production areas due to a lesser area occupied by the dryer-and-cooler complex;
- better sanitary and hygienic conditions of operation in the dryer-and-cooler complex room.
The «TEPLOCOM» Company will undertake development and implementation of the "turn-key" project of upgrading the sugar dryer-and-cooler complex.
