Comparative clarification performance of three different short retention time clarifiers in one Louisiana sugarcane factory

Sugarcane juice clarification is integral to the raw sugar manufacturing process. A comparative investigation between three short retention time (SRT) clarifiers of different designs, operating in parallel at one Louisiana (LA) sugarcane factory, was undertaken to evaluate their performance across a processing season. The factory used a hot lime clarification process in one Fletcher Smith clarifier and two LLT clarifiers; LLT1 had 9 turbulence reduction devices (TRDs) and LLT2 had 18 TRDs. Five samples of Hot Limed Flashed Juice (HLFJ) and Clear Juice (CJ) were collected each day, taking into account the retention times across each SRT clarifier, with a 30 min interval between samplings. Sampling periods were repeated six times during the 2019 processing season, with 120 samples collected. Overall, the LLT clarifiers performed slightly better than the Fletcher Smith clarifier, with slightly lower CJ turbidity, CJ calcium and phosphate values, and greater removal of turbidity, calcium, and phosphates. This may be explained by (i) the more stable flow of the juice fed into the LLT clarifiers and/or (ii) the addition of flocculant in each TRD of the LLTs, which meant the flocculant was more uniformly distributed into the juice in a high-velocity zone and guaranteed its effective mixing with the juice. Comparing the performance of the two LLT clarifiers, there was no statistical difference between them. However, the LLT1 performed slightly better than the LLT2, which may be a result from the clarifiers processing a different juice flow rather than design. As the three clarifiers processed the same HLFJ, it allowed for a comparison of total sucrose losses across clarification. Season average values of sucrose losses measured using high performance liquid chromatography across the Fletcher Smith, LLT1, and LLT2 clarifiers were 0.210, 0.363, and 0.336%, respectively, but not significantly different at p<0.05. The Fletcher Smith clarifier had slightly lower sucrose losses than the LLT clarifiers, resulting from its relatively lower residence time. Overall, the average value of sucrose losses for all three clarifiers in this factory was 0.306%, equivalent to 605,868 lbs of raw sugar, and represented a profit loss of US$152,981 and $0.20/TC for the whole season.