As an essential piece of equipment in sugar mills, the total capacity of 5th- or 6th-grade press electric motors accounts for more than half of the mill’s entire installed capacity. Currently, we have been relying on relatively conventional control methods—such as constant-speed operation, DC speed regulation, or hydraulic transmission systems—which have led to suboptimal sugar extraction rates. Yet, many factors influence extraction efficiency. If the extraction rate of the press machine could be improved by just 1%, the overall recovery rate would increase by between 0.88% and 0.92%. So what exactly are the underlying reasons for this less-than-ideal performance?

　　1. The efficiency of pressing is typically measured by two indicators: the throughput of sugar-extraction equipment and the extraction rate.

　　Generally speaking, under given conditions of sugar-extraction equipment, increasing the extraction rate often leads to a decrease in the pressing capacity, and conversely, boosting the pressing capacity tends to reduce the extraction rate. Therefore, the processing capacity and the extraction rate are mutually contradictory and mutually restrictive. When making a comprehensive consideration, it is essential to set an appropriate pressing speed that ensures both a sufficient pressing capacity and prevents the extraction rate from dropping too low.

　　2. After being compressed, the fibers in sugarcane expand again as they exit the mill. At this point, the expanded fibers themselves absorb some of the previously extracted juice at the outlet due to their own expansion. Meanwhile, influenced by the mill’s operational efficiency, not all of the sugar content in the sugarcane can be fully extracted. By adopting the technical principle of “increasing the load on the front rollers while reducing the overall machine load to enhance pressing efficiency,” we have modified and narrowed the openings and opening ratios of the mill’s front and rear rollers, thereby increasing the juice-extraction rate of the front rollers, reducing the juice-discharge pressure on the rear rollers, minimizing reabsorption, and lowering the moisture content of the bagasse. As a result, we achieve the ultimate goal of improving both the single-machine and overall plant extraction rates while simultaneously reducing the energy consumption of the mill.

　　3. The degree of crushing and the morphology of the sugarcane are also prerequisites for ensuring efficient extraction in the first-stage mill. When sugarcane is well-crushed, the juice is easier to press out, thus increasing the extraction rate. Of course, this process places certain demands on the sugar-extraction equipment as well.

　　4. The uniformity of the sugarcane layer delivered by the cane conveyor is crucial for improving the extraction rate. If the cane layer is too thick, the pressing will be incomplete; if it’s too thin, the cane layer won’t be fully dried. Both scenarios will negatively affect the extraction rate.

　　5. As the pressing rollers become increasingly worn, the gap between them widens, leading to a decline in extraction efficiency.

　　The five factors mentioned above that influence the sugar extraction rate clearly suggest that the advent of a frequency converter might help resolve this issue. However, for sugar-extraction equipment, it still remains an essential component in the sugar-making process.