PURGE SENSOR FINDINGS CONFIRMED AT MILLAQUIN MILL

An SRA-funded project in 2021 season investigated the use of a purge sensor to improve the performance of batch centrifugals used in mills to separate molasses from sugar crystals. The research was funded by SRA under the Small Milling Research Program investment scheme.

Interest from the milling sector in using the purge sensor to improve the management of the centrifugal station led to further investigations in the 2022 season.

Batch centrifugals spin at high speed to separate the layer of coloured molasses, known as mother molasses, from the sugar crystals. Hot water is sprayed onto the crystal bed to help remove the mother molasses and achieve the required crystal quality. This washing step is ideally conducted without dissolving an excessive amount of sugar because dissolved sugar and the spun off molasses must be recrystallised.

Currently the fugal station operator must rely on their own vision and hearing to judge the time and centrifugal speed at which the wash should be applied in order to minimise the dissolution of sugar. The purge sensor gives the operator a good indication of when the molasses and water flows from the crystal bed and so identifies the optimum time (or speed) to apply the wash water.

The purge sensor supplied by Neltec Denmark in the 2021 season investigated B massecuites, at Millaquin Mill. It was mounted on the outside of the centrifugal casing and detected the impact of molasses and wash water leaving the crystal bed and hitting the inside wall of the casing.

The following year the industry sought to investigate the sensor when fugalling A massecuites, an earlier stage in the crystallisation process.

In the 2022 season, Millaquin Mill installed the sensor and a one-week investigation followed, funded by QUT and facilitated by Factory Manager Millaquin, Robert Zahn and QUT Chief Investigator Ross Broadfoot.

The Small Milling Research Program investment scheme was developed to deliver investment for relatively low cost, short-term, industry-identified and led research projects.

The results of the purge sensor project were presented to millers at this year’s SRA/QUT Regional Milling Research Seminars held at five locations between Gordonvale and Rocky Point Mill. A paper was also presented at the ASSCT Conference showing results from both seasons.

“The results showed similar conclusions to the two main outcomes of the original project – 1) the sensor can consistently determine the optimum time (speed) to add the wash water and 2) the purging qualities of the massecuites can be defined qualitatively by the speed that the molasses is purged,” Ross Broadfoot said.

“Millaquin Mill has been the first mill to order a purge sensor for each fugal on their station,” said Ross.

“I hope more research will be done at other mills in future to demonstrate the effects and benefits more widely.”

Through investigating new technology such as this the milling sector is making positive steps towards greater efficiencies in the production process while achieving the sugar quality demanded by the world market.