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Beet Sugar Processing

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By Bento, Luis San Miguel
Posted on 2010-10-17    Last edited on 2010-10-17

White beet sugar is produced in Beet Sugar Factories directly from sugar beet.
Sugar beet is produced in temperate/cold weather countries. During circa of three months per year beet is harvested and processed in the factories to produce white sugar. In some countries it is possible to ha two beet campaings per year.

In the field beet leaves are separated from the beet root, containing the sucrose. I the factory beet roots are washed befor the processing to separate sand, stones and leafs. It is important to have a efficient washing in order to have to maintain the transpor water quality, where beet roots are transported by water, and to save the process equipemt against erosion.
After ashig beet roots are cuted in small pieces, as french fries, named cossettes.
Sugar contained in cossettes is extracted with hot water flowing in counter current in special equipment named difusers. Raw beet juice obtained in the difuser contains around 15% of soluble solids and around 13.2% of sucrose and 1.8% of non sucrose.
The residuals obtained in difusion process are named pulp. Pulp after difusion contains 92 - 93% of water. To remove the water pulps are pressed in order to obtain pulps with 10 - 15% of drymatter. These pulps will be used directly as cattle feed. Inorder to obtain a dried pulp, the presses must remove water till 18 - 24% of pulp solids and these pulps are dried in specila driers till circa 90% of dry matter. In some factories molasses is added to dryed paulps forming pulp pelettes.
Raw juice from difuser is then clarified by Carbonatation. Lime (calcium hydroxide) is mixed with the juice and, in a special reaction tank, CO2 is bubbled through the juice and calcium carbonate is formed. This operation is performed in two steps with mud (calcium carbonate and solids) is removed between the two reactors and after the second reactor. Normally the first separation is made by decantation and the second by press filtration.
Carbonated juice, with circa of 15.5% of soluble solids, is then evaporated in a set of evaporatores, normally five effects, in order to obtain a syrup with circa 70% of soluble solids.
Beet syrup is the crystallized in Vacuum Pans,normally in batch pans, in three steps. In the Pans sucrose in solution is crystallized and the resulting product, containing sugar crystals and the mother syrup,  is named massecuite. I
Massecuite discharged fron the Vacuum Pans is  centrifuged in high speed machines in order to separate crystals from syrup.  In the first crystallization step, A boiling, white sugar is produced. Syrup separated in the centrifugals in this step is named Molasses A. In a second step, B boilong, A molasses is crystallized and B sugar and B molasses is obtained. B sugar is melted and mixed with syrup comming from evaporators. B molasses is boiled in the last crystallization step, C boiling. C massecuite is cooled a a recrystallization is performed is special cooling crystallizers. This massecuite is centrifuged in continulas centrifuges and C molasses, named Final Molasses or simply Molasses is obtained. Normally in this molasses 1 kg of non sugars is associated with 1.5 kg of sugar.

 

Bibliogaphy

"Manuel de Sucrerie", 4th Edition, 1984, Ed. by Raffinerie Tirlemontoise S.A.

 

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