Review of the technical readiness of ultrafiltration membrane-based sugarcane juice clarification and subsequent sugar production

Abstract

The key benefit of sugarcane juice clarification by ultrafiltration (UF) membranes is the reduction in the energy usage for purification. A secondary benefit is the omission of chemical addition. Membrane-based clarification exhibits a high technical readiness level of 6 or 7. Pilot cases have demonstrated the ability of UF to reduce turbidity by >98 % while significantly decolorizing the juice. In this paper, five processes using UF-clarification at the pilot plant scale are reviewed. Two of the pilot processes focused on softening and filtering the sugarcane juice to reduce the polyvalent ion concentration. While another two processes focused on decolorization by size exclusion of impurities with tighter membranes. The final white sugar products from the different pilot processes were between 60 and 600 International Color Units. The lowest color is achieved by an integrated membrane process for clarification, decolorization, and concentration. The two main recommendations for the operation of UF-clarification are (1) pre-filtering the raw sugarcane juice (by screens or centrifugation) and (2) optimizing membrane cleaning protocols. For clarification, the specified membrane molecular weight cut-off should be between 65 and 3000 kDa to achieve a permeate flux for sugarcane juice between 35 and 125 L/(m² hr). Polymeric spiral wound, tubular ceramic, and tubular stainless steel UF membranes are technically suitable options for sugarcane juice clarification. By combining ultrafiltration modeling, which accurately predicts system design and operating parameters, with machine learning models, model predictive controls of sugarcane processes can be achieved. Developmental work utilizing the clarification byproduct in soil application shows promise.