Process Optimization to Reduce Sucrose Loss with Final Molasses: The case of Metahara Sugar Factory
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Date
2011-07
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Addis Ababa University
Abstract
In this study, process Optimization has been applied to D-massecuite boiling, cooling
crystallization, reheating and separation processes in MSF to minimize the high sucrose loss
with final molasses. Mother liquor purity and Purity drop were taken as response variables to
measure the performance of each process towards minimization of final molasses purity. Design
Expert-Response surface methodology was applied to statistically evaluate the data and to solve
optimum values factors and response variables. Economical advantages of the process
optimizations were compared with the factory’s existing working norms. D- massecuite boiling
optimization has resulted in nutsch purity reduction of 0.53 units. Similarly, an increase in
purity drop of 0.80 (from 4.21 to 5.01) across cooling crystallizers was obtained at optimum
cooling time of 17.36h and temperature to 450C for the existing crystallizer’s capacity. The
cooling experimental results have indicated that a purity drop of 6.37 units can be achieved if
crystallizer capacity of MSF increased so as to give cooling time of 34.5h and temperature of
440C. For the existing reheaters, the optimum reheating temperature was found to be 52.50C
which gave a purity rise across reheaters of 0.530 against the value of 0.97 before optimization
and the optimum massecuite flow rate of 19t/h. From the centrifugal separation optimization
result, the optimum spray water was found to be 6.3% massecuite giving a purity rise of 2.44
across centrifugal machines and DFW magma purity of 84.0. The overall effect of process
optimization was a reduction in final molasses purity by 1.43 units (from 34.86 to 33.43) for the
existing capacity of cooling crystallizer which leads to annual saving of 1040.5 tons sugar,
equivalent to 13,526,919 Birr. Additional saving of 12,334825birr/year is expected if enough
crystallizer capacity is installed for MSF.
Key words: Final Molasses, Sucrose Loss, Purity, Purity Drop, Exhaustion, Response Surface
Methodology
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Keywords
Final Molasses; Sucrose Loss; Purity, Purity Drop; Exhaustion; Response Surface Methodology