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[en] Hydrogen-producing granules formation was studied in a Continuos Stirred Tank Reactor (CSTR). The aim of this process is to later transfer the mixed liquor to a Up-flow Anaerobic Sludge Blanket (UASB) reactor to reduce its start-up period. Vinasses from a national bioethanol-producing industry (from sugar cane) were used as substrate and their anaerobic fermentation was carried out under mesophilic conditions. The seed sludge was collected from an UASB reactor operated in an industrial wastewater treatment plant and it was heat treated to inactivate methanogenic bacteria. Total viable and non-viable material growth curves were generated and it was determined that the exponential growth phase of the thermally pretreated mixed culture was between 20 and 120 h. Finally, the anaerobic fermentation of the vinasses in batch mode for 70 hours, and then in continuous CSTR mode for 7 days, showed to be an effective method for accelerating the formation of hydrogen-producing granules. Using this method, granules with an average size of 1.24 mm were achieved. The good efficiency of the process is attributed to high mass transfer in the CSTR reactor (author)
[es]
Se estudio la formacion de granulos productores de hidrogeno en un Reactor de Tanque Agitado Continuo (CSTR), por sus siglas en ingles), con el fin de transferirlos luego a un reactor Up-flow Anaerobic Sludge Blanket (UASB, por sus siglas en ingles) y asi acortar el tiempo de arranque del mismo. El sustrato utilizado fueron vinazas provenientes de una agroindustria nacional productora de etanol a partir de melazas de cana de azucar y su fermentacion anaerobia se llevo a cabo bajo condiciones mesofilicas. Los lodos para realizar la inoculacion del sistema se tomaron de un reactor UASB de una planta de tratamiento de agua industrial, a los cuales se les realizo un tratamiento termico con el objetivo de inhibir el crecimiento de bacterias metanogenicas. Se generaron curvas de crecimiento de materia viable y no viable total, con las cuales se determino que la fase de crecimiento exponencial de las bacterias en cultivo mixto pretratadas termicamente se encontraba entre las 20 y las 120 h. Finalmente, la fermentacion anaerobica de las vinazas durante 70 horas en modo 'batch' (por lotes) y posteriormente durante 7 dias en modo continuo tipo CSTR, demostro ser un procedimiento efectivo para acelerar la formacion de los granulos productores de hidrogeno, lograndose obtener granulos con un tamano promedio de 1,24 mm. La alta eficiencia del proceso se le atribuye a la elevada transferencia de masa que se obtiene en el reactor CSTR (autor)Journal
Tecnologia en Marcha; ISSN 0379-3982; 
; v. 27(1); p. 38-47
; v. 27(1); p. 38-47
[en] Specific features of calcium-thermic reduction of UF4 in a water-cooled plant are under consideration. Plant design is schematically represented and processing procedures for metallic uranium castings production are described. A particular attention is paid to service life of the basic part of the plant, namely, of reaction water cooled chromium bronze tube. 2 refs., 1 fig
Source
Chebotarev, N.T. (ed.); Ministerstvo Rossijskoj Federatsii po Atomnoj Ehnergii, Moscow (Russian Federation); Gosudarstvennyj Nauchnyj Tsentr Rossijskoj Federatsii, Moscow (Russian Federation). Vserossijskij Nauchno-Issledovatel'skij Inst. Neorganicheskikh Materialov; Voprosy Atomnoj Nauki i Tekhniki; (no.1); 95 p; 1995; p. 89-92; ISSN 0321-222X;
No abstract available
Journal
Chaos, Solitons and Fractals; ISSN 0960-0779; ; v. 91; p. 709
; v. 91; p. 709
[en] A gas-liquid microfluidic reactor was used to prepare polymer nanoparticles (PNPs) containing the drug 7-ethyl-10- hydroxy camptothecin (SN-38) from a series of poly(methyl caprolactone-co-caprolactone)-b-poly(ethylene oxide) (P(MCL-co-CL)- b-PEO) amphiphilic block copolymers with variable MCL content in the hydrophobic block. All three copolymers formed spheres with 20 nm core diameters by TEM, although some rigid rod-like aggregates were also formed by the PMCL-50 and PMCL-75 copolymers. SN-38 encapsulation efficiencies (EE = 2.7%-3.0%) and loading levels (DL = 2.0%-2.9%) were similar for the three copolymers. In vitro release kinetics became significantly slower as the MCL content increased, with release half times increasing monotonically from 3.4 to 6.2 h as the MCL content of the hydrophobic block increased from 50% to 100%. The ability to systematically tune release half times via controlled variation in the hydrophobic block composition, while maintaining constant PNP size and loading levels, represents an intriguing chemical handle for the optimization of SN-38 nanomedicines. (author)
Journal
Canadian Journal of Chemistry; ISSN 0008-4042; ; v. 97(5); p. 337-343
; v. 97(5); p. 337-343
[en] Modeling is an important tool to study and evaluate the behavior of the chemical process. Combination of simulation and control, it exhibits various characteristics of the process and provides the right direction to obtain the desired results from the chemical reactors. This paper discusses the various technical aspects of modeling, simulation and control in the process industries. The utilization and the relationship among the three techniques, modeling, simulation and control have been discussed. A case study is then presented for a batch reactor (in a sugar manufacturing plant) to use the modern techniques for modeling, simulation and instrumentation control. Presenting various scenarios on the above discussed techniques, the task has been dealt with comprehensively. (author)
Journal
Nucleus (Islamabad); ISSN 0029-5698; ; v. 46(3); p. 167-176
; v. 46(3); p. 167-176
[en] We show that the theorem of equipartition of entropy production is important for the understanding of the state of minimum entropy production in diabatic distillation. The theorem is not valid in a strictly mathematical sense. We explain why, when and in what sense this theorem is a good approximation to the optimal state in diabatic distillation. In order to make these predictions, we use a hypothesis for the state of minimum entropy production of an optimally controlled system, which was formulated on the basis of results of entropy production minimisation in chemical reactors. The hypothesis says that the state of minimum entropy production is characterised by approximately constant local entropy production and thermodynamic forces, given that there is sufficient freedom in the system. We present numerical results which are in agreement with the predictions. The results show that a column with constant tray entropy production in the stripping section and in the rectifying section is a good approximation to the optimal column, except when the total heat transfer area is low. The agreement between the two columns becomes better and better as the total heat transfer area and the number of trays increase. The fact that the predictions and the numerical results agree very well gives support to the validity of the hypothesis
Journal
[en] The scope of the paper is a theoretical analysis of the impact of the temperature of the cooling agent on the so called: 'Liapunov's time' in a model of a tubular chemical rector. For a chaotic solution, the values of Liapunov's time were found to be relatively low. This means that the chaotic state of the reactor is unpredictable even after relatively short observation time.
Journal
Chaos, Solitons and Fractals; ISSN 0960-0779; ; v. 41(5); p. 2647-2651
; v. 41(5); p. 2647-2651
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