The interest of ethanol production from agro-industry residues as raw material has deserved great attention since these feedstocks may constitute an alternative to fossil fuels as well as represent beneficial effects both from economic and environmental point of view. The sugar cane bagasse (SCB) is presented as an available and cheap opportunity of raw material. Although the SCB is usually burn at the sugar mill for steam and electricity production, there still remains certain amount of residues available for bioethanol production, according with (Albernas et al., 2014).

Fuel ethanol from SCB can be obtained through pretreatment, enzymatic hydrolysis and fermentation process stages. Once the pretreatment is performed, there are several ways for carrying out saccharification and fermentation. The simultaneous saccharification and fermentation (SSF) is one option, which as its name indicates, has the advantage of carrying out simultaneously the enzymatic hydrolysis and fermentation stages on the same processing unit, obtaining directly ethanol as a product. Then, it represents a promising separation technology because end-product inhibition is minimized (as glucose is converted as it is released), and therefore higher solid levels are allowed (Mesa et al., 2011). On the other hand, the number of process equipment is reduced and consequently the investment cost. Also, less energy is required and therefore production costs are also decreased and more sustainable process is achieved.

In this work a preliminary ethanol plant design is proposed. A mixed integer linear programming (MILP) model is formulated in order to obtain the optimal number of parallel units in each stage and their sizes (plant configuration and capacity). The production planning along the time horizon of one year is determined, given by the number of batches to be processed and its size. A formulation based on fixed sizes factors and times for discontinuous stages is proposed, which were obtained by experimental results of Albernas (2014) and Albernas et al. (2015). The model is implemented and solved in GAMS (General Algebric Modeling System). Different production sustainable scenarios are analyzed, for which the investment cost is minimized, and economic profitability indicators are calculated.

References

Albernas, Y., Corsano, G., Morales, M., González, M., Santos, R., & González, E. (2014) Optimal design for an ethanol plant combining first and second-generation technologies. CT&F - Ciencia, Tecnología y Futuro, Vol. 5, No. 5, 97-120.

Mesa, L.; González, E.; Romero, I.; Roiz, E.; Cara, C.; Castro, E. Comparison of process configurations for ethanol production from two-steps pretreatment sugar cane bagasse. Chemical Engineering Journal 2011, 175, 185-191.

Albernas, Y. (2014) Procedimiento para la síntesis y el diseño óptimo de plantas discontinuas de obtención de bioetanol empleando bagazo de caña de azúcar. Tesis en Opción al Grado Científico de Doctor en Ciencias Técnicas, Universidad Central Marta Abreu de Las Villas, Departamento de Ingeniería Química, Santa Clara.

Albernas, Y., Corsano, G., Mesa, L., Santos, R. & González, E. (2015) Estudio de la cinética de la hidrólisis enzimática del bagazo pretratado. Afinidad, Vol. LXXII, No. 570, Abril-Junio, 127-132.