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This work presents the synthesis, design, and simulation of bioethanol separation processes for the actual fermentation broth of a hybrid lignocellulosic feedstock. Different recovery and dehydration alternatives as well as their integrations were explored. For the recovery section, different sequences and technologies were considered and evaluated based on lumped-product streams for the multiphase and multicomponent crude broth: gases, preconcentrated bioethanol, stillage, and solids. For the dehydration section, different purification technologies were configured and analyzed. The synthesized alternatives were compared with the NREL reference case based on the total annual costs (TAC). Among the different recovery scenarios, one new alternative achieved 7% saving on TAC together with a higher concentrated bioethanol stream of 90 wt %. Regarding the dehydration section, extractive distillation together with gas stripping for glycerol recovery was evaluated as the optimal design with 46.2% saving on TAC. The optimal integrated separation process achieved 13.9% saving on TAC with respect the reference case.

BACKGROUND Bioethanol is a green fuel considered to be a sustainable alternative to petro‐derived gasoline. The transport sector contributes significantly to carbon dioxide emission and consequently has a negative impact on the air quality and is responsible for the increase of the greenhouse effect. The availability of environment‐friendly and economical fuels is a worldwide priority. The separation process is a significant technology in the production of fuel grade ethanol in terms of both operating and capital costs. In the present work an alternative distillation sequence for bioethanol separation is presented. The steady state performance and the dynamic beavior are analyzed compared with the classical configuration reported in the literature. RESULTS Ethanol–water azeotropic separation represents a challenge for bioethanol purification. Usually a three column sequence is used to obtain fuel grade bioethanol by extractive distillation. In order to reduce bioethanol purification cost a two column separation sequence is proposed. This configuration shows a 10% saving in capital costs together with higher ethanol recovery and better control properties compared with the classical three column sequence. CONCLUSIONS Based on the steady state and dynamic results obtained, the two‐column configuration represents a valid alternative to the classical configuration for the separation of bioethanol. © 2014 Society of Chemical Industry

Actual lignocellulosic fermentation broth has intrinsic multiphase and multicomponent nature and calls for complex separation systems in both bioethanol recovery and purification Rong, B.-G. Ind. Eng. Chem. Res. 2016, 55, 210]. In this work, we present the synthesis and evaluation of the intensified recovery and purification systems. A three-level methodology intensified the recovery, the purification, and both sections simultaneously. We proposed replacement of flashes by column sections, hybridizing unit operations by reformulating column sections, and relocation of column sections as novel synthesis approaches to formulate hybrid units and divided wall columns. Rigorous simulation in Aspen Plus V8.0 was used to simulate the intensified separation systems. The new intensified alternatives achieved relevant savings, ranging from 17 to 23% in TAC (total annual costs), and ranging from 18 to 28% in TEC (total energy consumption). Moreover, reduction of the number of separation units varied from the original eight units down to three units. Finally, we performed a sensitivity analysis varying the bioethanol concentration in the fermentation broth between the reference case, the intensified system with lowest TAC, and a multieffect distillation column scheme. The intensified system obtained cost savings of 15−20% higher than the multieffect scheme. We concluded that the novel synthesis procedure generated systems that efficiently reduced the energy and capital costs for the bioethanol recovery and purification task.

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