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On the suitability of agricultural by-products for the manufacture of granular activated carbon 总被引:1,自引:0,他引:1
An investigation of several agricultural by-products revealed that their suitability for activated carbon production is not determined by general material-specific features (elemental composition) but by type-specific features. A coarse-cellular structure (as in wood), which is indicated by porosities of the raw materials higher than 35% is disadvantageous. A specific change in the properties of cokes (porosity, density, hardness) is possible by varying the conditions of pyrolysis. By rapid heating in the pyrolysis step, for instance, macroporous residues are produced. Temperature and burnoff have the greatest influence on the quality of the activated carbon during the activation step. Of the investigated materials, coconut shells yield granular activated carbon of the highest quality. The following order of suitability of raw materials for activated carbon production was established: coconut shells> peach stones> plum stones> hazelnut shells> walnut shells> cherry stones. 相似文献
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We present microfabrication and characterization of truly three-dimensional (3-D) diffuser/nozzle structures in silicon. Chemical vapor deposition (CVD), reactive ion etching (RIE), and laser-assisted etching are used to etch flow chambers and diffuser/nozzle elements. The flow behavior of the fabricated elements and the dependence of diffuser/nozzle efficiency on structure geometry has been investigated. The large freedom of 3-D micromachining combined with rapid prototyping allows one to characterize and optimize diffuser/nozzle structures 相似文献
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Solid absorption is regarded as an option to separate CO2 from high temperature gases. At present, suitable sorbents are limited to calcium or lithium containing oxides. Among the
latter, lithium orthosilicate (Li4SiO4) might be preferred due to its high reactivity for CO2 absorption. Improved sorption properties are obtained by appropriate doping of Li4SiO4. Especially, doping of vacancies into the lattice of crystalline Li4SiO4 seems to be advantageous. This is concluded from sorption experiments of Al- and Fe-doped Li4SiO4 that are presented in this article. In addition, a comparison to eutectic doping by use of potassium is provided. For the
investigation of practical applicability, cyclic absorption/desorption was performed on selected samples. 相似文献
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Jan Ploen Jens Andersch Michael Heschel 《Drug development and industrial pharmacy》2013,39(10):1210-1218
Background: An extended release pellet formulation (ACES®) of the weakly basic drug propiverine was developed with spheronized citric acid crystals as starter cores. Method: Coated pellets, consisting of several layers of functional coatings, were manufactured by fluid bed coating. Different coating levels were examined with regard to their effect on drug release. Release profiles from the formulations with or without pH modifier and the free base as well as the hydrochloride salt of the active ingredient were compared. Results: The coated citric acid starter cores led to a controlled release of the drug and the pH modifier, resulting from modulation of the microenvironmental pH throughout the dissolution period of 17 hours. If microcrystalline cellulose pellets are used as starter cores drug release is strongly pH-dependent. Significant differences in the drug release profiles were observed between the formulations containing the free drug base and those with the hydrochloride salt as a result of an altered microenvironmental pH. Conclusion: The presented extended release pellet formulation is able to maintain a low pH within the pellet core and thus a sufficiently high drug solubility. By maintaining a low pH inside the pellets, a controlled drug release can be achieved. 相似文献
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