Properly understanding of sludge rheological properties is important for designing of pumping and translating. Effect of thermal hydrolysis on rheological properties of municipal sludge was studied using a rheometer (DHR-2) with concentric cylinder geometry. Test results indicated both raw and thermal treated sludge displayed non-Newtonian rheological behavior with shear thinning, exhibiting thixotropic properties and viscoelasticity. The Herschel–Bulkley model could represent their flow behavior more accurately than other models. However, for the raw sludge, as solid content reached 120 g/L, fluidity disappeared, and all the rheological models could not describe it accurately. After thermal hydrolysis, the consistency index (k) decreased significantly, while the flow index (n) increased, suggesting that thermal treated sludge was much closer to the Newtonian fluid compared to the raw sludge. Both raw and treated sludge exhibited strong dependence on solid content and temperature. Correlations between solid content, temperature, and viscosity were expressed by an exponential equation and an Arrhenius type equation, respectively. Analysis of thixotropic properties illustrated that evolution of viscosity over time could be expressed by a first-order (solid content lower than 100 g/L) and a second-order thixotropic kinetic equation (solid content higher than 100 g/L), respectively, for raw sludge. For treated sludge, it could be simulated by a first-order thixotropic kinetic equation. Furthermore, the dynamic test indicated viscoelasticity of treated sludge decreased remarkably. For treated sludge, as the solid content was larger than 120 g/L, viscoelastic parameters were linearly correlated with logarithm frequency.

•Capillary forces were the root cause for the formation of shrinkage cracks.•Surface tension of filtrate linearly decreased with increasing CTAB concentration.•CTAB was adsorbed onto iron ore concentrates by electrostatic attraction.•Contact angle reached maximum when the monomolecular adsorption layer formed.•CTAB could avoid or reduce shrinkage cracks of filter cakes to some extent.During the dewatering process of iron ore concentrates, the formation of shrinkage cracks severely interferes with the filtration process and causes high cake moisture. Until now, effective countermeasures and mechanism study about shrinkage cracks are still insufficient. In the previous researches, capillary forces have been considered to be the driving potential for the shrinkage cracks, which were related with liquid surface tension and particle contact angle. Thus, surface tension and contact angle were both changed in this paper by using a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB). Moreover, the zeta potential, adsorbance and infrared spectra were respectively measured before and after CTAB coating to analyze the change of interfacial properties and the influence on the extent of shrinkage cracks. The results indicate that the tendency of filter cakes to form shrinkage cracks can be weakened with the decrease of capillary forces.

•We present an experiment to achieve threshold friction volume fraction’s value.•We present the modified friction viscosity equation for granular flow.•Kinetic friction term is the key to simulate particle’s blocking.•Granular temperature’s function is used to measure granular motion hysteresis.This paper focus on the numerical method of dense granular flow dynamics in two motion states: quasistatic and rapid movement. At first, threshold volume for friction, which joins particles collision and friction stress regimes together, is obtained from the experiment of three kinds of quartz sand accumulation in measuring cylinder by gravity. After that two movement experiments are performed to protrude dense granular flow motion characteristic. One is the experiment of particle’s blocking in the L-pipe and the other is the experiment of particles’ mixing by impeller for three kinds of quartz sand. The former is regarded as a representative of quasistatic and the latter is treated as a representative of granular flow rapid movement. Then two numerical simulations are conducted with the two corresponding experiments and the numerical results are inspected by the experimental data. The mathematical method is employed to describe the difference between the two different models of motion. And then the influence of modificatory friction viscosity equation is investigated in accordance with fact motion. The emphasis is the relationship between numerical method and granular flow motion characteristic. This modificatory method effectively bridges particles collision and friction stress regimes in the sand free fall and expresses the hysteresis quality in the process of dense granular flow motion speedup.

Isobaric vapor–liquid–liquid equilibrium (VLLE) data were measured for the ternary system water + cyclohexane + acrylic acid at 200 mmHg (absolute pressure). The apparatus are a modified dynamic recirculating still equipped with mixing section for experimental test and a gas chromatography (Agilent GC7890A) for analyzing, respectively. The VLLE data have been used to verify the dependability of the NRTL, NRTL-HOC, and UNIQUAC-HOC models prediction results for the water + cyclohexane + acrylic acid system. The parameters for these models were obtained using experimental data regression. Comparing the predictions and experimental data, the HOC equations have a good effect in vapor phase prediction with a strong self-polymerization of compounds system, and the NRTL-HOC model has a more acceptable prediction of the VLLE data than the UNIQUAC-HOC model.

Phosphotungstic acid (HPW) supported on activated carbon (AC) was applied to catalyze deep oxidation desulfurization of fuel oil with the assist of ultrasound. The sulfur-conversion rate was evaluated by measuring the concentration of dibenzothiophene (DBT) in n-octane before and after the oxidation. Supporting HPW on AC has been verified to play a positive role in UAOD process by a series of contrast tests, where only HPW, AC or a mixture of free HPW and AC was used. The influences of catalyst dose, ultrasound power, reaction temperature, H2O2:oil volume ratio and the reuse of catalyst on the catalytic oxidation desulfurization kinetics were investigated. The DBT conversion rate of the reaction catalyzed by supported HPW under ultrasound irradiation was higher than the summation of the reactions with HPW only and AC only as catalyst. With the increase of loading amount of HPW on AC, ultrasound power, H2O2:oil volume ratio and reaction temperature, the catalytic oxidation reactivity of DBT would be enhanced. The optimum loading amount of HPW was 10%, exceed which DBT conversion would no longer increase obviously. DBT could be completely converted under the optimized conditions (volume ratio of H2O2 to model oil: 1:10, mass ratio of the supported HPW to model oil: 1.25%, temperature: 70 °C) after 9 min of ultrasound irradiation.

Cavitation is a complex physical phenomenon affected by many factors, one of which is the gas dissolved in the medium. Researchers have given some efforts to the influence of gas content on sonoluminescence or some specific chemical reactions in and around the bubble, but limited work has been reported about the influence on the ultrasonic cavitation field distribution. In this work, the intensity distribution of the ultrasound field in a cleaning tank has been measured with the hydrophone. After analysed and visualised by MATLAB software, it was found that the cavitation intensity distribution in degassed water was much better than that in tap water. And further study proved that degassing process can improve the cavitation effect dramatically both in intensity and scope. Finally, the cavitation fields in mediums with different gas content were measured and the specific influence of air content on cavitation field was discussed.

Waste cooking oil (WCO) is becoming the most promising alternative feedstock to produce biodiesel due to its low cost in China. In this study, NKC-9 ion-exchange resin and H-beta zeolite were selected as heterogeneous catalysts in the WCO esterification process and their esterification characteristics were compared by orthogonal experiments. NKC-9 resin showed higher activity and achieved a higher final conversion compared with H-beta zeolite under the same reaction conditions. Reusability experiments showed that NKC-9 resin still exhibited high activity after 5 runs. The effects of the mole ratio of alcohol to oil, reaction time, reaction temperature and the catalyst dose were investigated by multifactor orthogonal analysis. The influence of the free fatty acid (FFA) content was also investigated, and the result showed that the esterification rate could be as high as 98.4% when the FFA content was 6.3wt%.

Phosphotungstic acid/activated carbon (PTA/AC) catalysts with various AC sizes or PTA content have been synthesized and characterized by N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy and temperature programmed desorption of ammonia. These catalysts were then evaluated in terms of the removal of dibenzothiophene (DBT) by ultrasoundassisted oxidative desulfurization process. The results showed that the DBT conversion obviously increased with the decrease of AC support size and the increase of PTA content. After supporting PTA on AC, the DBT conversion can be improved by 38.9% after ultrasound irradiation for 10 min. In addition, the stability tests of PTA/AC showed that the catalytic oxidative activity of PTA/AC was nearly kept constant after ultrasound irradiation for 20 min, which makes it a promising catalyst to use in ultrasound-assisted oxidative desulfurization process.

Isobaric vapor–liquid–liquid equilibrium (VLLE) data for the ternary system cyclohexane + water + acetic acid were measured at 101.3 kPa. A modified dynamic recirculating still equipped with a mixing section was used to determine the VLLE. The experimental data indicate that a binary heterogeneous azeotrope is present at 342.16 K with a composition of 0.3 and 0.7 mole fractions of water and cyclohexane, respectively. The VLLE data have been used to test the reliability of the UNIQUAC and NRTL models in the prediction of VLLE. The two model parameters were obtained using VLE and LLE data correlation, respectively. The results indicate that the NRTL model has an acceptable prediction of the VLLE data, and the UNIQUAC model has a prediction of the heterogeneous region.