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921.
Lambertus G. Manders Martin Meister Jens Bausa Klaus-Dieter Hungenberg 《Macromolecular Symposia》2011,302(1):289-296
Summary: To safeguard runaway reactions in industrial scale, qualified methods have to be used. While mechanical safety devices are usually installed, their design may be problematic as the runaway kinetics must be known. This may not be the case for many processes due to the required flexibility and possible unanticipated deviations from recipes. It is shown that runaway kinetics can be very fast and can lead to high conversions. Therefore, a method is proposed that does not depend on kinetics but limits the amounts of unreacted monomer in the reactor by monitoring the conversion and by quantitatively determining the hazardous potential. If a potential violation is observed, feeds to the reactor are interrupted. 相似文献
922.
The thermal degradation of two polyethylene samples (LDPE and HDPE) has been carried out in a batch reactor under dynamic conditions. The evolution of products generated after regular intervals of 5 min (temperature increments of approximately 25 °C) has been analyzed. The behaviour of LDPE and HDPE has been compared, and no differences in the quantity and weight fraction of the gaseous products obtained have been found. For both polymers, n-paraffins are the major products at the very beginning of the process, while as the decomposition proceeds 1-olefins are more abundant. The condensed fraction is much larger than the gaseous fraction and its analysis reveals some differences between the behaviour of LDPE and HDPE at the beginning of the degradation process. These differences disappear at higher temperatures where more similar trends are observed. 1-Olefins, n-paraffins, dienes and olefins with wide carbon number distributions are the most important condensed compounds obtained in the thermal degradation of both polyethylenes. The formation of 1-olefins and n-paraffins begins at slightly lower temperatures than for dienes and olefins. On the other hand, as the temperature increases, the amount of low and high molecular weight compounds increases at the expense of intermediate molecular weight products and the former become the most important by the end of the degradation process. This behaviour could be related to the thermal cracking of waxes through secondary reactions. 相似文献
923.
Michael Dolan Narendra Dave Leigh Morpeth Richard Donelson Daniel Liang Michael Kellam Song Song 《Journal of membrane science》2009
Amorphous alloy membranes composed primarily of Ni and early transition metals (ETMs) are an inexpensive alternative to Pd-based alloy membranes, and these materials are therefore of particular interest for the large-scale production of hydrogen from carbon-based fuels. Catalytic membrane reactors can produce hydrogen directly from coal-derived synthesis gas at 400 °C, by combining a commercial water–gas-shift (WGS) catalyst with a hydrogen-selective membrane. In order to explore the suitability of Ni-based amorphous alloys for this application, the thermal stability and hydrogen permeation characteristics of Ni–ETM amorphous alloy membranes has been examined. A fundamental limitation of these materials is that hydrogen permeability is inversely proportional to the thermal stability of the alloy. Alloy design is therefore a compromise between hydrogen production rate and durability. Amorphous Ni60Nb40−XZrX membranes have been tested at 400 °C in pure hydrogen, and in simulated coal-derived gas streams with high steam, CO and CO2 levels, without severe degradation or corrosion-induced failure. Ni–Nb–Zr amorphous alloys are therefore prospective materials for use in a catalytic membrane reactor for coal-derived syngas. 相似文献
924.
Makoto Ozawa Yukihiro Tsutsumi 《Proceedings of the American Mathematical Society》2003,131(12):3945-3954
We show that if there exists an essential accidental surface in the knot exterior, then a closed accidental surface also exists. As its corollary, we know boundary slopes of accidental essential surfaces are integral or meridional. It is shown that an accidental incompressible Seifert surface in knot exteriors in is totally knotted. Examples of satellite knots with arbitrarily high genus Seifert surfaces with accidental peripherals are given, and a Haken 3-manifold which contains a hyperbolic knot with an accidental incompressible Seifert surface of genus one is also given.
925.
926.
This article reviews the engineering development and safety aspects that are relevant to the nuclear power programme being
pursued in the country. Some of the important aspects have been discussed in detail bringing out the current status and also
the directions for further work. 相似文献
927.
928.
Marco?Ischia Renzo?Campostrini Luca?Lutterotti Elisa?García-López Leonardo?PalmisanoEmail author Mario?Schiavello Fabrizio?Pirillo Raffaele?Molinari 《Journal of Sol-Gel Science and Technology》2005,33(2):201-213
Homogeneous TiO2 gel powders were prepared by hydrolysis and condensation of titanium(IV) isopropoxide with HCl or SnCl2 catalysts, by working under reduced pressure or in air. Ti(IV) alkoxide was previously modified by reaction with formic or acetic acid, used as chelating ligands, when gelation was performed in acidic catalysis. Crude TiO2 xerogels were purified by water reflux treatment in order to induce a low temperature crystallisation to the anatase phase. Both crude and purified TiO2 samples were characterised by XRD, FT-IR, SEM, and N2 adsorption analysis. Thermoanalyses (TG, DTA, DTG, TG-MS, TG-GC-MS) were carried out to quantify the residual organic components in the crude TiO2 gels and to obtain stoichiometric formulas to describe their chemical compositions. XRD data of purified TiO2 powders were processed by means of a Rietveld refinement procedure to determine TiO2 polymorphs, crystallite sizes and cell parameters, before their use in photocatalytic tests. The photoactivity of the purified TiO2 anatase powders was studied by using 4-nitrophenol degradation as probe reaction carried out in a batch and/or a membrane photoreactor. Samples prepared by using formic acid or SnCl2 were the most photoactive, whereas specimens gelled under vacuum treatment showed detrimental effects. 相似文献
929.
P. Singh S. V. L. S. Rao Rajni Pande T. Basak Shweta Roy M. Aslam P. Jain S. C. L. Srivastava Rajesh Kumar P. K. Nema S. Kailas V. C. Sahni 《Pramana》2007,68(2):331-342
At BARC, development of a Low Energy High Intensity Proton Accelerator (LEHIPA), as front-end injector of the 1 GeV accelerator
for the ADS programme, has been initiated. The major components of LEHIPA (20 MeV, 30 mA) are a 50 keV ECR ion source, a 3
MeV Radio Frequency Quadrupole (RFQ) and a 20 meV drift tube linac (DTL). The Low Energy Beam Transport (LEBT) and Medium
Energy Beam Transport (MEBT) lines match the beam from the ion source to RFQ and from RFQ to DTL respectively. Design of these
systems has been completed and fabrication of their prototypes has started. Physics studies of the 20–1000 MeV part of the
Linac are also in progress. In this paper, the present status of this project is presented.
相似文献
930.