RETRACTED: Production of Pure Ethanol from Azeotropic Solution by Pressure Swing Adsorption
−Pressure swing adsorption (PSA) is attractive for final separation in the process of water removal especially for fuel ethanol production. Despite many researches on simulation and experimental works on adsorption of water on 3A zeolite in a fixed bed, none have studied a process with the actual PSA system. The purpose of this research was to study the PSA process with two adsorbers and effects of several parameters. The research also included analysis of kinetic and thermodynamic data of ethanol-water adsorption on commercial 3A zeolites in a single fixed bed. A two-level factorial design experiment was used in this research work to preliminarily screen the influence and interaction among the factors. Effects of important parameters such as initial temperature, feed concentration and feed rate were investigated. It was proven that the Langmuir isotherm could best predict the experimental results. In the PSA pilot test, the principal factors, which had effects on the performance, were feed rate, feed concentration, adsorption pressure and the cycle time. Prediction of the process efficiency in terms of ethanol recovery and enrichment was proposed in the form of regression models. The results of the study in a fixed bed adsorber could help designing a pilotscale PSA unit. The experiments proved to be successful in terms of producing high concentration ethanol with high percentage of ethanol recovery. With further simulation work the process could be scaled up for an industrial use.
Pilot study of bioethanol dehydration with polyvinyl alcohol membranes
Reduction of production costs is an essential part in the development of more economic and competitive production processes. Membrane techniques have a great potential to decrease the separation costs in the biofuel production. In this research, the feasibility of pervaporative dehydration of bioethanol to be processed for vehicle fuel usage was studied. The focus was on the feed prefiltration, energy integration and permeation behaviour, which are important factors for membrane stability and product quality. In addition, they have a major impact on the energy efficiency of the ethanol dewatering. Experiments were done by using activated carbon filtration equipment and pervaporation unit equipped with hydrophilic crosslinked polyvinyl alcohol (PVA) membranes. Results indicate that active carbon filtration can provide an efficient and up-scalable pretreatment method for the pervaporation feed. Further, the tested pervaporation membranes provided adequate selectivity, not only for the retentate (ethanol), but also for the permeate (water). Low ethanol concentration in the permeate favors intense integration of energy flows and energy savings.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME