Process for the recovery of water and energy from the processing of sugar cane in sugar and ethanol production mills

Process for the recovery of water and energy from the processing of sugar cane in ethanol production mills, using the sugar cane straw and bagasse as energy source for an electric energy and steam generation unit and comprising the steps of:

• a—submitting the sugar cane to a juice extraction operation with imbibition by vegetal vapor condensate;
• b—treating and purifying the extracted juice, using vegetal vapor condensate, pre-evaporation vegetal vapor and inputs and producing a clarified juice flow, a sludge flow and a vegetal vapor condensate flow;
• c—treating the sludge flow, producing a filter cake and a recovered juice flow which is returned to the step of treating and purifying the juice;
• d—submitting the clarified juice flow to a pre-evaporation unit, under heating by exhausted steam from the energy generation unit, producing:
• an exhausted steam condensate, to be at least in part returned to the energy generation unit;
• an evaporation vegetal vapor flow;
• and a pre-evaporated juice flow;
• e—cooling the pre-evaporated juice by indirect thermal exchange with at least one of the means defined by a flow of part of the extracted juice (mixed juice) and by a vegetal vapor condensate flow circulating by a cooling tower unit;
• f—fermenting the cooled must constituted by pre-evaporated juice, producing a wine flow, and distillating the wine to produce ethanol and vinasse, wherein:
• the extracted juice (mixed juice) is heated by indirect thermal exchange, before its physical-chemical treatment with at least one of the means defined by a pre-evaporated juice flow and vegetal vapor condensate flows recovered in the process;
• the extracted juice, submitted to the physical-chemical treatment, is heated to about 105° to 110° C., by indirect thermal exchange with the pre-evaporation vegetal vapor flow, transforming the latter in a vegetal vapor condensate flow;
• the step of distillating the wine is carried out with the indirect heating of the wine by at least one of the means defined:
• by part of the pre-evaporation vegetal vapor flow;
• by part of the exhausted steam flow;
• and by a vinasse vegetal vapor flow, producing an alcoholic vapor flow and at least one of the flows defined by vegetal vapor condensate and exhausted steam;
• the alcoholic vapor flow is cooled by indirect thermal exchange with at least one of the flows defined by fermented wine and by vegetal vapor condensate water of the cooling tower unit;
• the vinasse is submitted to a multiple effect vacuum vinasse evaporation unit, under heating by pre-evaporation vegetal vapor, producing:
• a vinasse vegetal vapor flow;
• a last effect vinasse vegetal vapor flow;
• a vegetal vapor condensate flow;
• and a concentrated vinasse flow;
• the wine, to be distillated, is pre-heated by indirect thermal exchange with at least one part of the flows defined by an alcoholic vapor flow of a distillation stage and by a last effect vinasse vegetal vapor flow, producing an alcoholic vapor condensate flow and a vinasse vegetal vapor condensate flow;
• the excess of the vegetal vapor condensate flows which is not used in the process is sent, at least in part, to the cooling tower unit and, if it is still available, stored for posterior treatment.

Process for the recovery of water and energy from the processing of sugar cane in sugar production mills, using the sugar cane straw and bagasse as energy source for an electric energy and steam generation unit and comprising the steps of:

• a—submitting the sugar cane to a juice extraction operation with imbibition by vegetal vapor condensate;
• b—treating and purifying the extracted juice, using vegetal vapor condensate, evaporation vegetal vapor and inputs and producing a clarified juice flow, a sludge flow and a vegetal vapor condensate flow;
• c—treating the sludge flow, producing a filter cake and a recovered juice flow which is returned to the step of treating and purifying the juice;
• d—submitting part of the clarified juice flow to a multiple effect vacuum evaporation unit, under heating by exhausted steam from the energy generation unit, producing:
• an exhausted steam condensate, to be returned to the energy generation unit;
• at least one evaporation vegetal vapor flow;
• a last effect vegetal vapor flow;
• a vegetal vapor condensate flow;
• and a syrup flow;
• e—concentrating the syrup until the crystallization point of part of the sucrose contained therein under heating with at least part of the vegetal vapor flow produced in the evaporation unit, producing a crystallization vegetal vapor flow, a vegetal vapor condensate flow and a crystallized product flow (crystallized mass);
• f—centrifuging the crystallized product, producing an end syrup (molasse) flow and a sugar flow to be dried and bagged, wherein:
• the extracted juice (mixed juice) is heated, at least in part, by indirect thermal exchange with at least one of the flows defined by last effect vegetal vapor of the evaporation unit and by the vegetal vapor from the step of concentrating the syrup for crystallization, transforming said vapor flows in vegetal vapor condensate flows;
• the excess of the vegetal vapor condensate flows, which is not used in the process, is sent, at least in part, to a cooling tower unit and, if it is still available, stored for posterior treatment.