Restoring the operational capacity of a coupled-loop molasses desugarization separator

Abstract

Maintaining extract product quality while maximizing recovery of the sucrose in the second (extract) loop was becoming increasingly difficult at the American Crystal Sugar Hillsboro molasses desugarization (MDS) facility. Molasses processing rates were reduced to accommodate increasing pressure drops across the second loop. Frequent high pressure shutdowns were leading to increased downtime and poorer separation in the second loop. Fractal plates were removed from second loop cells and viewed under a microscope. Scale was collected and analyzed. Scale was also found in the product stream feeding the second loop. Analysis of the scale indicated it was predominantly calcium oxalate. A fractal plate testing cart was built that allowed a comparison in performance between the scaled (fouled) fractal plates and new plates. Poor flow characteristics were observed in the fouled plates. Several approaches were tried to clean up the fractal plates with varying degrees of success. When the fouled plates were cleaned mechanically, better flow characteristics were observed. The process of mechanical cleaning was utilized in the factory. Pressure drops were markedly lower (as much as 60% less) after clean-up. Work is underway to determine the root cause of the scale that appears from time to time and fouls the separator. This paper reviews the troubleshooting and resolution of a problem that has plagued the process over time.