78 research outputs found
Green, red and infrared Er-related emission in implanted GaN:Er and GaN:Er,O samples
Er-related luminescence near 1.54 mm ~;805 meV! is observed under below band gap excitation at
4.2 K in GaN:Er and GaN:Er,O implanted samples. The spectrum of the recovered damage samples
is a multiline structure. So far, these lines are the sharpest ones reported for GaN. Well-resolved
green and red luminescences are observed in implanted samples. The dependence of luminescence
on the excitation energy as well as the influence of different nominal fluence and annealing
conditions is discussed. Combining the results obtained from photoluminescence and Rutherford
backscattering spectrometry, different lattice sites for the optical active Er-related centers are
identified
Process flowsheet analysis of pervaporation-based hybrid processes in the production of ethyl tert-butyl ether
BACKGROUND
The manufacturing process of ethyl tert-butyl ether (ETBE) involves the separation of ETBE, mixed C4 hydrocarbons and unreacted ethanol. Unfortunately, the unreacted ethanol forms azeotropic mixtures with ETBE that are difficult to separate by distillation. One of the alternative methods to overcome this limitation is the application of hybrid distillation–pervaporation processes with alcohol-selective membranes.
RESULTS
Simulation tasks were carried out with the process simulation software Aspen Plus and the results of alternative process flowsheets that result from the relative location of the separation technologies (for a target product purity) have been compared on the basis of the required membrane area and energy consumption. Thus, in the case study analyzed seven pervaporation modules located on a sidestream withdrawal, with a total membrane area of 210 m2, are required to obtain 6420 kg h−1 of ETBE with a purity of 95.2 wt%. The retentate stream is returned to the column while the permeate stream, with a high ethanol content, is recycled back to feed the reactors
CONCLUSION
Incorporating pervaporation modules in the process flowsheet for production of ETBE allows unloading of the main separation unit (debutanizer column), thereby reducing energy consumption and operating costs and increasing throughput.Financial support from the Spanish Ministry of Science under the projects CTM2013-44081-R (MINECO, Spain-FEDER 2014–2020), CTQ2015-66078-R and CTQ2016-75158-R is gratefully acknowledged. Adham Norkobilov also thanks the SILKROUTE Project for a PhD scholarship funded by the European Commission through the Erasmus Mundus Action 2 Programme
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