RESUMEN
Falling film evaporation technology is widely used in the treatment of salt-containing wastewater in coal chemical industry. However, there is still a lack of research on the inlet method of vertical falling film evaporation tubes. In this paper, the heat and mass transfer processes of saline wastewater under vertical and tangential inlets were investigated using numerical simulations. On this basis, the differences in flow and heat transfer processes between saline wastewater and pure water under tangential inlet were investigated. The results showed that the flow velocity of saline wastewater with a falling film evaporation tube in a tangential inlet mode was larger. Meanwhile, the turbulence in this way was more intense and the fluid temperature in the vertical tube was higher. Saline wastewater has higher temperature and smaller liquid volume fraction than pure water liquid membrane in the range of 193-1,000 mm from the inlet. The use of tangential inlet method to treat salt-containing wastewater has higher evaporation efficiency and is a very effective way to guide the improvement of heat transfer efficiency.
Asunto(s)
Calor , Aguas Residuales , Bahías , TemperaturaRESUMEN
Cu-BTC was synthesised by hydrothermal method in this study to adsorb and remove the toxic heavy metal hexavalent chromium Cr(VI) in water. The EDTA-chitosan/Cu-BTC was prepared by the surface modification of Cu-BTC with EDTA-modified chitosan. The initial concentration effects of adsorbed chromium solution, adsorbent dosage, adsorption time, adsorption temperature and pH of chromium solution on adsorption capacity were estimated using the single-factor optimisation experiment. Results show that the adsorption capacity of the modified composite was higher than that of Cu-BTC. Cu-BTC and EDTA-chitosan/Cu-BTC exhibited significant adsorption of Cr(VI) under acidic conditions in water and basically independent of temperature. Their adsorption processes conformed with the pseudo-second-order model. The Langmuir adsorption isotherm model obtained the adsorption isotherm, which indicated that the adsorption process was single molecule adsorption. Isotherm fitting obtained the maximum adsorption amounts of Cr(VI) for Cu-BTC and EDTA-chitosan/Cu-BTC at 27.32 and 46.51 mg·g-1, respectively. Factor and principal component analyses show that the main factors affecting the adsorption of Cr(VI) in the EDTA-chitosan/Cu-BTC composites are pH, initial concentration and adsorption time. Therefore, EDTA-chitosan-modified Cu-BTC was a more feasible metal-organic framework material than Cu-BTC because of better adsorption performance, which can be used for adsorption removal of Cr(VI) in water.
RESUMEN
Cr-MnOx/cordierite composites were prepared by Sol-gel, Impregnation, Co-precipitation and Rheological phase reaction method. Various technologies including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), thermogravimetry/differential scanning calorimetry (TG/DCS), and temperature-programmed reduction (TPR) were used to characterize the structure and morphology properties of the synthesized composites. The catalytic ability test of 1,2-dichlorobenzene (o-DCB) over the catalysts was conducted in a fixed-bed flow reactor with a gas hourly space velocity (GHSV) of 30,000 h-1 to investigate the catalytic performance of the prepared composites. The results indicated that the combined Cr2O3 and Mn2O3 phases supported on cordierite possessed a special ball-shaped and better redox property in the catalyst prepared by the Co-precipitation method with a Cr/Mn atomic ratio of 2â¶5, which was conducive to the increase of the synergistic effect and subsequently enhancement of the catalytic performance. Furthermore, it exhibited better stability within 60 h, which indicates a good prospect for industrial applications.
