Papers by Keyword: Mixing Time

Abstract: As large flow rate of argon blowing in the process of bottom argon blowing ladle will cause severe fluctuations and sprays of molten steel, making the slags surface boiled and steel secondly oxidized, melting the refractory materials in the ladle, the flow rate of bottom argon blowing is limited, which will affect the efficiency of stirring. A 1:7 ratio ladle water model is established in the lab, and we will discuss how the diameter (d) of immersed tube, inserting depth (h) and the rate of bottom argon blowing affect the mixing time. The results show that the fluctuations on the steel surface can be diminished by the variations of diameters of immersed tube and inserting depth, the mixing time can be shorted by the increased flow rate of bottom argon blowing.

Abstract: In order to better master the production process and the road performance of rubber asphalt, the paper studied the influence law of mixing method, mixing temperature, mixing time and rubber powder content on the performance of rubber asphalt. The results show that all the indexes except the viscosity of rubber asphalt has little change with different mixing methods, and the rubber asphalt has the best performance under the high-speed stirring molding method but the worst performance under the high-speed shearing molding method. Meanwhile, the performance of rubber asphalt change visibly with different mixing temperatures, on which the excessively high or low production temperature has negative significance, so the optimal production temperature would be recommended as 180~200°C. Furthermore, the mixing time and the rubber powder content are the two critical factors which may greatly affect the performance of rubber asphalt, followed by the mixing temperature and the mixing method.

Abstract: Although small in size, indiscriminate littering of cigarette butts (CBs) can cause serious environmental impact. Several trillion cigarettes produced worldwide annually lead to thousands of kilograms of toxic waste. CBs accumulate in the environment due to the poor biodegradability of the cellulose acetate filters and, in doing so, they have become the most common litter item on our planet. This paper presents some of the results from a continuing study on recycling CBs into fired clay bricks. Physico-mechanical properties of fired clay bricks manufactured with different percentages of CBs (2.5%, 5% and 10%) and also of control brick samples are reported and discussed. To improve the properties, three different mixing times were tested with 7.5% of CBs incorporated in clay bricks, specifically at 15 minutes, 10 minutes and 5 minutes respectively. The impacts of these changes on physical and mechanical characteristics were evaluated. With 15 minutes mixing time, the measurement increased up to 114% and 12% for strength and density respectively compared to 5 minutes mixing time. On the other hand, values for water absorption, initial rate of absorption and tensile strength decreased by 22%, 29% and 5% respectively. Microstructure analyses of CB bricks were also investigated using ESEM. Attempts were also made to improve the properties by incorporating 3% of steel fibre into CB brick samples. Nevertheless, the addition of the steel fibre did not significantly improve the properties or the appearance of the manufactured samples.

Abstract: Selecting a right simulation method is important for accurately predicting flow field in stirred reactor. The Reynolds-Averaged Navier-Stokes (RANS) approach with standard model and large eddy simulations (LES) method were both used to analyze the turbulent flow field in a tubular stirred reactor for leaching. Calculations were performed to study the effects of agitator speed and flux on the turbulent flow field. The velocity at different axial sections gained by the two methods was compared. Results showed that the eddy current, especially in the back of impellor, predicted by LES was better than that by standard model. At the same time，the average relative error of the mean residence time and the mixing time of the former reduced 5% and 13% respectively than that of the latter.

Abstract: The influence of the different airway structure on mixing time of molten steel are studied through using water model experiments. The bubble volume and velocity have been investigated through the PIV for different airway structure in the flow of 1m3/h. Results showed that with the slit distribution same, the smaller the slit width, the greater the volume percentage of the large bubbles and the average velocity of the bubbles in rising, but the shorter the mixing time. Reduce the number of the slit can lead to the volume percentage of the large bubbles and the average velocity of the bubbles in rising decreases, the mixing time extended, and it is more obvious to the mixing time to reduce the number of the inner slit. Inflatable volume<1.1m3/h, with the slit in the outer ring only and the number of slit same, the volume percentage and the average velocity of the large bubbles in rising is larger, the mixing time is reduced. Inflatable volume≥1.1m3/h, the slit evenly distribution is better for mixing.

Abstract: Stirring characteristics of wall oxygen lances of EAF and bath mixing under different conditions were studied by using an 1/10 length scale down of cold model of 100-ton capacity EAF. The effects of horizontal angle, vertical angle of a lance and the distribution of lances along the EAF wall on bath stirring and mixing were researched experimentally. The results showed that the horizontal angle of the lances had significant impact on the local fluid flow and mixing time, whereas the mixing time is less affected by the lance vertical angle relatively. It was found that the shortest mixing time had been obtained in the conditions that the horizontal angles were -3°, 0° and -2° respectively under the modified lance distribution in the variant shape of bath. Compared with the mixing time measured in the conditions of the prototype, the average mixing time for p1, p2 and p3 and the mixing time for p4 point were reduced by 52.3% and 44.7% respectively with the optimum scheme.

Abstract: The effects of the bath shape, oxygen lance nozzles structure, and lance level on liquid steel mixing time and splashing amount were studied by experiment orthogonal design with 1:10 water model for 100 t basic oxygen converter modeling. The results showed that the stirring effect in the bath can be improved by changing the shape on the bath surface around the furnace wall with arc-shaped structure which can shorten the mixing time and reduce the liquid slag and steel splashing amount of the lining, and result in reducing metal lose and prolong the life of the lining.

Abstract: With the increasing demand for high quality steel, various secondary refining techniques have been developed in the past decades. RH powder top blowing process (RH-PTB) is practiced in industry to decrease the impurity content of steel in a more economical way. In the present work, based on similarity theory, RH powder top blowing process was simulated by water model, and the effects of operating parameters on mixing time were investigated. The results show that the injected powder had a negligible effect on mixing time in RH-PTB, and the mixing time increases with top lance gas flowrate and decreases with lifting gas flowrate of up-leg. It was found that the mixing time was no longer decreasing as the lifting gas flowrate was over 15 L/min. Moreover, the height of top lance has some effect on mixing time in the reactor, and it should be adjusted to specific circumstances for purposes.

Abstract: In order to analyze the complex phase transition in the gas-liquid-solid three-phase mixing systems and to predict gas-liquid-solid multiphase mixing time, a novel method combined image processing technology, computational homology and CFD (Computational Fluid Dynamics) numerical simulation is introduced in this study. Firstly, the volume of fluid (VOF) multiphase flow model in FLUENT software is used for the simulation of fluid characteristics. Secondly the patterns produced by phase transition in the stirred tank are binaryzed. Finally evolution profile of the zeroth dimensional Betti numbers and the first dimensional Betti numbers in time series are obtained separately. In fact,some aggregates still remain in the tank after the homogeneous mixing.Comparing with the fractal method to characterize the mixing time, the result shows that this method not only can predict the gas-liquid-solid mixing time by the zeroth dimenstional Betti numbers, but also can predict the amount of these aggregates in the stired tank by the first dimenstional Betti numbers, leading to a useful parameter to characterize the non-uniformity of gas-liquid-solid mixing.

Abstract: Variation of calcium excess, water content and mixing time have been taken into the parameters of the injection test of calcium phosphate paste synthesized via low temperature hydrothermal method. The result indicated that all the parameters are very prominent to influence the material injectability possible to be fully injected out the syringe. Strict control of paste synthesizing parameters has successfully overcome poor injectability of the material.