Experience gained from perforated mill rolls in Reunion

Perforated rolls (also known as Lotus rolls) have been in use for some time in sugar mill tandems. High drainage rates were expected when such designs were provided. However, blockages often occurred, and this design of mill rolls did not spread worldwide. Nowadays, improved design of shell materials, of holes and juice drainage capacity reduces blockages. In Reunion, the two sugar mills implemented perforated rolls in their extraction processes in 2017. The main objectives were to improve juice drainage and reduce maintenance costs of the Messchaert grooves. In the Bois-Rouge sugar factory (bagasse diffusion), one was installed as a top roll in the final dewatering mill. This roll has resulted in very good juice drainage capacity and a decrease in bagasse moisture was observed. Given this experience, a second perforated roll was installed in 2018 as a top roll in the first dewatering mill. In Le Gol sugar factory (a five-mill milling tandem), five perforated rolls were installed in 2017, three in the pre-extractor and two on the last mill. A higher drainage capacity was observed after the pre-extractor. However, the expected effect on bagasse on the final mill was not achieved. Thus in 2018, several perforated rolls were installed along the milling tandem and the experience gained from their use is presented in this paper. Performance on bagasse moisture, juice extraction, and costs are discussed.