Mesoscopic Fluid-Particle Flow and Vortex Structural Transmission in a Submerged Entry Nozzle of Continuous Caster.

Understanding the essence of the flow oscillations within a submerged-entry nozzle (SEN) is essential to control flow patterns in the continuous casting mold and consequently increase the superficial quality of steel products. A numerical study of the mesoscopic fluid-particle flow in a bifurcated pool-type SEN under steady operating conditions is conducted using the lattice Boltzmann method (LBM) coupled with the large eddy simulation (LES) model. The accuracy of the model has been verified by comparing vortex structures and simulated velocities with published experimental values. The LBM modeling is also verified by comparing the "stair-step" jet patterns observed in the experiment. The geometrical parameters and operational conditions of physical experiments are reproduced in the simulations. By comparing the time-averaged velocities of Reynolds-averaged Navier-Stokes equations (RANS) with LBM models, transient mesoscopic fluid-particles and related vortex structures can be better reproduced within the SEN. The visualization of internal flow within the SEN is illustrated through the mass-less Discrete Phase Model (DPM) model. The trajectories show that the LBM-LES-DPM coupled model is good at predicting the transient vortical flow within the SEN. A large vortex is found inside the exit port and continuously changes in shape and size therein. The monitoring points and lines within the SEN are selected to illustrate the velocity variations and effective viscosity, which can reflect the oscillating characteristics even under stable operating conditions without changes at the exit from the SEN. Furthermore, the formation, development, diffusion, and dissipation of the vortex structures from the exit port of the SEN are also investigated using the Q criteria. The comparison of the power spectrum with high-frequency components along the exit port indicates that the flow oscillations must originate from within the SEN and are intensified in the exit port. The mesoscopic LBM model can replicate the fluid-particle flow and vortex structure transmission as well as their turbulence effects inside the SEN in detail.

A Hybrid Ensemble Model Based on ELM and Improved AdaBoost.RT Algorithm for Predicting the Iron Ore Sintering Characters.

As energy efficiency becomes increasingly important to the steel industry, the iron ore sintering process is attracting more attention since it consumes the second large amount of energy in the iron and steel making processes. The present work aims to propose a prediction model for the iron ore sintering characters. A hybrid ensemble model combined the extreme learning machine (ELM) with an improved AdaBoost.RT algorithm is developed for regression problem. First, the factors that affect solid fuel consumption, gas fuel consumption, burn-through point (BTP), and tumbler index (TI) are ranked according to the attributes weightiness sequence by applying the RReliefF method. Second, the ELM network is selected as an ensemble predictor due to its fast learning speed and good generalization performance. Third, an improved AdaBoost.RT is established to overcome the limitation of conventional AdaBoost.RT by dynamically self-adjusting the threshold value. Then, an ensemble ELM is employed by using the improved AdaBoost.RT for better precision than individual predictor. Finally, this hybrid ensemble model is applied to predict the iron ore sintering characters by production data from No. 4 sintering machine in Baosteel. The results obtained show that the proposed model is effective and feasible for the practical sintering process. In addition, through analyzing the first superior factors, the energy efficiency and sinter quality could be obviously improved.

Effect of permanent magnetic field on scale inhibition property of circulating water.

Effect of a permanent magnet field on the scale inhibition property of circulating water was investigated. Orthogonal experiments of L16(45) were performed and analyzed using the range analysis method. The operating parameters included magnetic field intensity, initial concentration of Ca2+ and Mg2+, magnetic treatment time, temperature, and flow velocity. Scale inhibition rate, hardness, relative variation in the proportion of free water molecules, electrical conductivity, and relative variation of molecular energy were chosen as the objectives. In addition, the morphology and the composition of CaCO3 and MgCO3 scale were studied by X-ray diffraction analysis. The optimal conditions were initial concentration of 900 mg/L, magnetic field intensity of 0.5 T, temperature of 303 K, time of 54 h and flow velocity of 0.17 m/s. The nuclear magnetic resonance results demonstrated that the number of hydrogen bonds increased between water molecules and hydrated ions. The magnetic field can promote the increase in the number of hydrogen bonds, which can inhibit the formation of calcium and magnesium carbonate precipitation. Moreover, the ratio of calcite, aragonite and vaterite will be changed at different magnetic field intensities, and the aragonite ratio will reach the peak at the optimum conditions.

A new gasification and melting incineration process of MSW with co-current shaft furnace.

In all the municipal solid waste (MSW) disposal technology, incineration with gasification and melting has been taken as a environmentally sound and zero emission technology owing to avoiding second-pollution of heavy metals and dioxin. In this background, a new direct gasification and melting incineration process with co-current shaft furnace is put forward. In this process, MSW and combustion-supporting air are co-current from top to bottom in a shaft furnace. Fuel gas from pyrolysis and gasification burns completely in the bottom in order to offer energy for slag melting. The simulation experiment of the co-current shaft furnace has been done. The results of simulation experiment show that the temperature on the condition of co-current is much higher than on the condition of countercurrent at the bottom of reaction tube and so is the CO2 quantity discharged from reaction tube. It can be concluded that the co-current shaft furnace is more suitable for direct gasification and melting incineration process.