2. Sugarcane processing
In a typical sugarcane mill, the stages illustrated in Fig. 1 are present.
The typical mill has an upfront section that is common to the ethanol distillery and sugar factory composed by the following processes: cane reception, cane preparation and juice extraction. The extracted juice is sent to the juice treatment system, in which impurities are removed from the juice in order to provide an adequate material for the subsequent steps; although most of the operations of juice treatment are common for both sugar and ethanol production, each process has its own specificities. During processing in the sugar factory, a concentrated residual solution obtained after sugar crystallization (molasses) is produced. Sugarcane juice from the ethanol juice treatment is blended with molasses, fermented using yeast (which is recovered and reused in the fermentation process), and the fermentation product containing ethanol is sent for distillation and dehydration. In the sugar house the juice is concentrated, crystallized, centrifuged and dried.
All the energy (steam and electricity) needed in this process is produced by the mill using sugarcane bagasse as fuel. In many mills surplus power is generated for sale to the grid. Some mills have been recovering a fraction of the sugarcane straw (sugarcane tops and leaves) and using it as fuel as well, however this is not yet a common practice in Brazilian facilities due to high recovery costs and questions about short and long term soil implications (Cardoso et al., 2013). However, sugarcane burning phase out provides an opportunity for straw use. In Sections 2.1–2.3 the prevailing process technologies are briefly described.
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2.1. Shared operations
2.1.1. Cane reception
Upon arrival at the factory, mechanically harvested sugarcane is discharged upon tables and sent to the cleaning system or directly to the feeding tables that lead to the cane preparation section. In the