Search

Abstract: The aim of this study was to estimate the increase in industrial water consumption and withdrawal in a conventional sugarcane ethanol mill due to the introduction of second-generation ethanol production by a bagasse hydrolysis process, and to identify opportunities of water reuse, in order to minimize water withdrawal. Simulations in ASPEN PLUS® software were performed for mass and energy balances. Three cases were evaluated: a conventional ethanol production plant (Case I), and two second-generation plants incorporating bagasse hydrolysis differing only in their glucose concentration processes, namely by evaporation (Case II), and by membrane separation (Case III). Results show that external withdrawals of 738L/t of cane for Case I, 955L/t of cane for Case II and 853L/t of cane for Case III are required to cover the water deficit of the plant. These values are lower than the mandated limit of 1000L/t of cane for the sugar cane industry in the State of São Paulo. Moreover, for Cases II and III, which need large additional amounts of water for the hydrolysis stage, water usages of 10.77 and 9.38L of water per litre of ethanol produced were achieved, approaching the figure of 9.34L water per litre of ethanol produced by the conventional plants (Case I). This highlights the high potential for reduction practices based on the concept of energy and water integration. [Copyright &y& Elsevier]

Sugarcane is one of the most important industries of the Brazilian economy, and its main products are sugar and ethanol. Most of the industrial plants produce both products in an integrated process, in which the sugarcane bagasse is a by-product that can be used as a fuel in the cogeneration system. The bagasse is used as the only fuel of the plant, supplying all energy required for the process, and also producing electricity surplus that may be sold to the grid. In this paper, exergy analysis is used to assess an integrated sugar and ethanol plant with its cogeneration system. The plant was divided into eight sub-systems to evaluate the irreversibility generation in each separately. Data from typical sugarcane factories in Brazil, which produce sugar and ethanol, were used in the process simulation. The analysis has shown that the sub-systems with the highest contribution for the total irreversibility generation of the plant were co-generation, juice extraction and fermentation. Some improvements are proposed, including process thermal integration and the introduction of more efficient equipments for prime mover and steam and electricity generation. The analysis indicated that the total irreversibility could be reduced by 10% should those changes be implemented. [Copyright &y& Elsevier]