V Verma and RN Tiwari
Spray Engineering Devices Limited, Mohali, Punjab, India; vivek.verma@sprayengineering.com; rajeevnath.tiwari@sprayengineering.com
Development of innovative technology based on mechanical vapour recompression (MVR) for sugarcane processing is explained. The reuse of thermal waste heat using a compressor allows high heat economy and eliminates the need for external heat generation and rejection units such as boilers, turbines, cooling towers and condensers. Aiming for energy efficiency and 100% bagasse saving, the plants are designed and installed based on an MVR system coupled with falling-film plate evaporators. The design incorporates low-temperature evaporation based on a mechanical vapour recompression (MVR) system using thermal waste heat recycling to eliminate the burning of biomass. This is a transformational shift in the industrial landscape, where the process becomes carbon negative and water positive due to no biomass burning and 100% water recovery. Using this innovative MVR technology, a 250 t cane/day (tcd) plant was engineered, designed, erected, and commissioned without the use of a boiler during 2022-23. For melt concentration at one factory (8,300 tcd), raw sugar melt from an initial concentration of 61% to 74% was achieved with a flow rate of 80 t/h in 2021-22, resulting in a steam saving of 7.0 t/h in when two sets of multi-effect falling-film plate evaporators of total heating surface 4000 m2 were coupled with an MVR system. In phase 2 in 2023-24 for juice evaporation and concentration, three sets of falling-film plate evaporators of total heating surface 7500 m2 with a flow rate 165 m2/h was installed with an MVR system for initial brix of 10-12 Bx to 30-32 Bx and total steam reduction in both phases of 30% on cane from 39% on cane with enhanced plant capacity of 8,300 tcd to 10,800 tcd. In addition, a new 170 kL/day grain-based distillery using an MVR system was installed for ethanol production. By adopting this innovative MVR technology, the sugarcane processing and distillery units can be boiler free with high energy efficiency giving 100% bagasse saving and zero carbon emission.