The process adopted in the manufacture of sugar is Double Sulphitation Process.
Sugar Factory consists of the following five main stations:
Mill house is the cane crushing unit which consists of cane carrier, cane cutter having cutting knives, milling tandem, bagasse carrier and conveyor. Cane feeding to the cane carrier is done by unloaders and feeder table. As the cane carrier moves, the cane kicker evens out cane load in the cane carrier and then two sets of cane knives cut the cane into small pieces. This process of cane cutting is called ‘cane preparation. These cane pieces then, pass through different mills and the juice is extracted. The mills are driven by D.C.motors. The residue which comes out of the mill after extraction of juice is called bagasse.
Boiler generates steam by burning the bagasse. The steam is used in powerhouse, boiling house, curing house. The steam required by the Sulphitation process varies from 42 – 45 % on cane crushed per hour.
The high pressure steam generated by the boiler is utilized for production of power by the turbo-alternators. The power produced is used for captive needs and the surplus power is exported to the government grid. The low pressure steam that comes out from the turbo alternator is utilized for boiling the extracted juice.
The juice extracted by the mills is measured by juice flow system. The measured juice is heated in juice heater in two stages. First the juice is heated by the vapours from fourth and third bodies of evaporator in different heaters. This heating is called primary heating. The heated juice is treated with milk of lime and sulphur-di-oxide to coagulate maximum impurities and sent for secondary heating. The secondary heating is done with vapours from second body of evaporator and vapours from the first body or exhaust steam. The treated juice is passed to clarifier, where in clear juice is removed from the top and settled mud at the bottom is separated. To extract sugar from the mud, it is taken to vacuum filter in which juice and filter cake are separated. Juice is taken back to process and the mud is disposed as solid waste. Clear juice from clarifier is taken to evaporator for evaporating its water content. First body is heated by exhaust steam, and other bodies by the vapours of the previous body. The total water evaporated in the evaporator is 75-80 % percent. The juice after evaporation is called as syrup. This syrup is normally of 60 % solids of its total weight. The syrup is then sulphited in syrup Sulphitation tower.
Sulphited syrup is taken to pan floor for making sugar crystal. Three massecuites boiling systems is normally adopted, in which, A, B and C Massecuites are boiled. A-massecuites is formed by boiling syrup, sugar melt ,‘A’ light molasses and on ‘B’-single cured sugar as seed. This A-Massecuite is boiled till it attains the required size of sugar crystal and it is dropped into crystallizers and cooled. After exhaustion of sugar in solution, the ‘A’ massecuite is passed on to the centrifugals for separating sugar crystals from the massecuite. The separated ‘A’ sugar is bagged after drying. ‘A’-Light and ‘A’-Heavy molasses are pumped to pan floor and are used for making ‘A’- and ‘B’-Massecuite respectively.
‘B’-Massecuite boiled in ‘B’ pans is dropped into B- Crystallizers and then it is cured in ‘B’-Centrifugal machines. ‘B’-heavy molasses and ‘B’-single cured sugar are obtained separately. ‘B’-single cured sugar is used as seed for A massecuite. ‘B’-heavy molasses is used for making ‘C’-Massecuite in C-pans. ‘C’-Massecuite is dropped into ‘C’-Crystallizers where it is cooled. ‘C’-Massecuite is then taken to ‘C’-fore worker centrifugal machines for curing. Final molasses and ‘C’-single cured sugar are obtained. ‘C’ Single cured sugar is again cured in another centrifugal machine in which ‘C’-double cured sugar and ‘C’-light molasses are obtained. ‘C’-light molasses are taken to pan floor and is used in making ‘C’-Massecuite. ‘C’-double cured sugar is melted and is used in making ‘A’ Massecuite.
Sugar discharged from ‘A’ Machine is dropped on to grass hopper conveyors. By passing hot air in hoppers the sugar is dried and taken to grader in which powder and rori’s are separated. The required grade sugar is bagged.