In this paper, the particle dynamics and free surface in a simplified disc device are studied using experiments and the Discrete Element Method (DEM). Two different kinds of free surface formula for the motion of particles in a disc device are derived and calculated. The disc rotational speed, particle filling rate, and particle materials are used as three experimental control parameters, and the experimental results are compared with the numerical calculation results. In order to obtain the dynamic distribution of particles, the influence of contact friction parameters are discussed by the DEM simulation. Besides the operating conditions, it can be observed that the particle material properties play an important role in particle dynamic distribution and DEM granular flow prediction. The results prove a feasible prediction of the particle free surface physical models, which also provides a method and theoretical basis to predict the particle flow characteristics in the vertical screw conveying.
Boundary conditions in computational fluid dynamics significantly affect the prediction of flow field. However, the outlet boundary conditions for the continuity equation have been rarely investigated. In addition, the velocities at the outlet boundary might not be accurately predicted with the conventional outlet boundary conditions when a flow that has non-uniform density distribution on the outlet boundary is simulated. In the present study, we modified a boundary condition for the continuity equation in consideration of the non-uniform density distribution on the outlet boundary plane, comparing the numerical results of combustion between the conventional and modified boundary conditions. As a result, the proposed boundary condition can resist the generation of an unrealistic temperature field better than the conventional methods.
Computational fluid dynamics was applied for simulations of a three-dimensional fluidized bed to study the effectiveness of various turbulence models coupled with multiphase models in replicating hydrodynamic profiles within the fluidized bed. For bubbling fluidization, the shear stress transport (SST) k–ω model coupled with the Eulerian multiphase model provided close agreement with experimental results reported by other researchers. For the turbulent fluidization regime, neither the Reynolds-averaged Navier–Stokes model nor large eddy simulation (LES)/detached eddy simulation (DES) were adequate in simulating the hydrodynamics within the fluidized bed. The realizable k–ε and SST k–ω models were able to generate voidage and velocity profiles that were in good agreement with experimental results. However, both models over-predicted the particle velocities. The realizable k–ε model coupled with the Eulerian multiphase model produced the best representation of the core-annular fluidization regime. For all fluidization regimes considered, LES/DES was unable to replicate the hydrodynamics observed in experiments because of over-predictions of particle velocities or voidage.
The attrition characteristics of PKM1-SU particles, which are absorbents for pre-combustion CO2 capture, were investigated under various experimental conditions by varying the test apparatus, static bed height, temperature, pressure, gas velocity, and humidity. A fluid catalytic cracking (FCC) catalyst was used as a reference material for comparison. In this study, the attrition characteristics caused by the gas jets of the distributor were evaluated using a conventional ASTM D5757-95 attrition test apparatus and a newly designed high-temperature and high-pressure bubbling fluidized bed attrition test apparatus. The attrition amount (or rate) of particles (PKM1-SU and FCC catalyst) increased with increasing pressure and gas velocity, whereas it decreased with increasing static bed height and temperature. The attrition characteristics of the FCC catalyst were not affected by humidity, whereas those of the PKM1-SU particles were strongly affected. The attrition rates of PKM1-SU were higher during the early period (1 h) than during the later period (2–5 h). Therefore, both the corrected weight loss index at 5 h and the weight loss index at 5 h should be considered.
Indium, gallium, and zinc oxide (IGZO) is a semiconducting material that is widely used in the manufacturing of semiconductors, touch panels, displays, etc. This work aims to shed some light on the recovery and separation of indium, gallium, and zinc from spent IGZO targets by solvent extraction (SX). The process involved leaching, SX in high acidity, stripping, re-extraction in low acidity, and re-stripping, followed by the cementation of the gallium and indium with zinc dust. Triisobutyl phosphate (T-iso-BP) was employed as the extractant to separate the majority of zinc from indium and gallium in the leaching solution. The leaching solution was utilized directly without further adjustment, to avoid consuming an enormous amount of water. The loaded organic (LO) solution was then stripped with HCl solution at pH 2, moving the majority of indium and gallium from LO phase to aqueous phase. The extraction and stripping process enabled the transfer of indium and gallium from the leaching solution (8–8.5 mol/L HCl solution) to HCl solution at pH 2, without diluting the leaching solution with an enormous amount of water. The stripped solution was then extracted with di-(2-ethylhexyl) phosphoric acid to separate indium from gallium. The optimum extraction conditions and stripping conditions were studied. From the actual spent IGZO target, 97.8% of indium with a purity of 98.3% and 96.2% of gallium with a purity of 99.6% were separated and recovered.
At present, the flue aimed temperature in coke oven production is mainly determined by artificial experience, which leads to the lack of theoretical guidance in the control process, and the parameters are difficult to adjust in real time. In this paper, the optimization model of the flue aimed temperature of coke oven is established. The correlation model between coke quality, coke yield, coking energy consumption and the flue aimed temperature is analyzed. Firstly, the factors affecting coke quality, coke yield and coking energy consumption are determined by mechanism analysis. Secondly, an improved grey relational analysis method is proposed to quantitatively analyze the correlation between coke quality, coke yield, coking energy consumption and their influencing factors, so as to determine the input of multi-objective optimization model. Because the neural network has a strong nonlinear approximation effect, the RBF neural network is introduced to establish a prediction model of coke quality, coke yield and coking energy consumption. Then, maximizing coke yield and minimizing coking energy consumption are chosen as the optimization object, the coke quality and production boundary are chosen as constraints, and the local optimization targets as decision variables, whereby the multi-objective optimization model is designed. The multi-objective genetic algorithm is applied to solve this multi-objective optimization problem. The optimal value of the flue aimed temperature of coke oven is obtained. Finally, the practical running results show that the proposed multi-objective optimization model has good applicability.
NOx emission prediction is important for efficient boiler production and waste control. An adaptive data-driven modeling method is proposed to predict the boiler NOx emissions dynamically. In this method, a linear combination kernel is presented to improve the prediction accuracy of least-square support vector machine. The parameters of the kernel are optimized adaptively by a particle swarm optimization algorithm. Additionally, an adaptive moving time window strategy is presented to maintain model performance. The computational results based on the practical data illustrate that the proposed kernel and the adaptive moving time window strategy are positive and the proposed prediction method is superior to some previous prediction methods.
We studied an efficient recovery process for precious metals from secondary resources. The release behaviors of gold and silver were investigated during the heat treatment of an incinerated spent circuit board in a stream of chlorine gas. When the incinerated ash alone was heated in a stream of chlorine, a temperature of 1000°C was required to completely volatilize the gold and silver in the sample. However, the temperature required for the initial release of gold and silver decreased when a mixture of the incinerated spent printed circuit board and carbon particles was heated in a stream of chlorine, and fractions of these metals were captured by the carbon particles. The amounts of gold and silver captured by the carbon particles decreased when the temperature increased above 800°C. To completely volatilize the gold and silver from the sample and to ensure their capture by the carbon particles, the sample was heated to 1000°C in chlorine gas, and the volatilized chlorides were passed through a bed of carbon particles, which was maintained at 800°C. The total amounts of gold and silver from the incinerated printed circuit board were successfully recovered by adjusting the temperature and thickness of the bed of carbon particles.