Héctor Hernández

Co-production of ethanol, hydrogen and biogas using agro-wastes. Conceptual plant design and NPV analysis for mid-size agricultural sectors

Abstract A parametric cost analysis is presented for the co-production of ethanol, hydrogen and biogas considering financial and operational conditions of mid-size agricultural sectors. A hypothetical feedstock based on wheat straw is employed whose price is related to its polysaccharides content. Production costs are calculated using the Net Present Value ( NPV ) technique for a given process flowsheet as a function of plant capacity (100 to 2,100 ton DS/day) versus feedstock polysaccharides concentration (i.e. price). The co-production scheme is compared against an ethanol-only production strategy. The lowest cost was 0.42 USD/l etOH for 2,100 ton DS/day using the minimum polysaccharide-concentration feedstock for the co-production scheme, compared against 0.51 USD/l etOH if only ethanol is produced. A detailed account of cost contributions is presented for the 2,100 ton DS/day capacity plant. Feedstock contribution reaches 47% for some schemes. Enzymes and operation costs also play an important role (20-30% and 16-27% respectively).

Design and Optimization of Thermally Coupled Distillation Sequences for Purification of Bioethanol

An important problem in the bioethanol production process is the purification of ethanol from a dilute solution, i.e., approximately 10% ethanol in water. The key factor in the purification process is the formation of the ethanol-water binary homogeneous azeotrope, and an additional process is required to obtain high purity ethanol that can be used in motor vehicles. This study examines the design and optimization of three extractive distillation options (two with thermal coupling) for the purification of a representative mixture of ethanol and water. These extractive arrangements can produce ethanol as distillate with the required purity and energy savings, reduction in CO2 emissions, high thermodynamic efficiencies and good control properties.

Design and optimization of thermally coupled extractive distillation sequences

Abstract In this paper, design and optimization procedures are developed for a conventional extractive distillation sequence and a thermally coupled extractive distillation scheme. The proposed methodologies detect the optimal values of the design variables in order to guarantee the minimum energy consumption. It was found that the optimum energy consumption can be related to the minimum total annual operating cost, minimum greenhouse gas emissions, higher thermodynamic efficiencies and good theoretical control properties. The methodologies were applied to the study of the separation of several close boiling point mixtures using the two distillation sequences. The results showed that the energy savings predicted in the complex extractive distillation sequence can be achieved along with reductions in greenhouse gas emissions.

Design and Control of New Intensified Distillation Systems for Quaternary Separations using Genetic Algorithms

Abstract The design and optimization of a coupled distillation system is a non-linear and multivariable problem. The complexity of this kind of problem leads to the high difficulty for solving it. This paper addresses the application of genetic algorithms to the optimization of intensified distillation systems for quaternary distillations. For that purpose, we used a multi-objective genetic algorithm with restrictions, written in Matlab™ coupled to process simulator Aspen Plus™ for the evaluation of the objective function.

CONTROL PROPERTIES ANALYSIS OF ALTERNATE SCHEMES TO THERMALLY COUPLED DISTILLATION SCHEMES

� � � Abstract: Recently, on the assumption that the presence of the recycle stream in thermally coupled distillation schemes (TCDS) might origin a difficult operation, some alternate arrangements that might provide better operational properties have been proposed. In this work, on the framework of singular value analysis, control properties of two alternate schemes were assessed and compared with their corresponding TCDS. The results show that the alternate schemes, in which the recycle streams are removed, do not necessarily provide an improvement on the control properties. Copyright