Optimization of the separation paraments in inclined channels of liquid-solid fluidized bed

A new theoretical formula can be used to calculate superficial velocity for particle separation with a critical condition, and it is based on the size, density, terminal velocity, Reynold number of the particle and equipment parameters. In a continuous system, a series of fractionation experiments were conducted to quantify the separation performance for 0–2 mm coal particles under various factors, including channel spacing, solids throughput and split fluidization rate. The separation performance considers the ash content and yield of products varying with the particle size. A great fluidization environment can be created by the 6 mm channel spacing. For the solids throughput of 10.20 t/(m2h) provides a well effective separation in the narrow channels. In addition, the split fluidization of 0.0058 m/s can produce a higher shear induce force in the inclined channels to prevent the low-density particles from being lost in the underflow. The theoretical superficial velocity calculated by the new formula is 0.042 m/s, which can report the particles with the upper and lower size reach at 9-fold to the overflow, it is almost the same as the actual separation fluidization velocity of 0.04 m/s. Meanwhile, the data obtained under each separation condition is basically consistent with data of the sink-float mothed, which shows a good separation performance for the Reflux Classifier.

Design of Thermal Insulation Materials with Different Geometries of Channels

Investigating the large number of various materials now available, some materials scientists promoted a method of combining existing materials with geometric features. By studying natural materials, the performance of simple constituent materials is improved by manipulating their internal geometry; as such, any base material can be used by performing millimeter-scale air channels. The porous structure obtained utilizes the low thermal conductivity of the gas in the pores. At the same time, heat radiation and gas convection is hindered by the solid structure. The solution that was proposed in this research for obtaining a material with porous structure consisted in perforating extruded polystyrene (XPS) panels, as base material. Perforation was performed horizontally and at an angle of 45 degrees related to the face panel. The method is simple and cost-effective. Perforated and simple XPS panels were subjected to three different temperature regimes in order to measure the thermal conductivity. There was an increase in thermal conductivity with the increase in average temperature in all studied cases. The presence of air channels reduced the thermal conductivity of the perforated panels. The reduction was more significant at the panels with inclined channels. The differences between the thermal conductivity of simple XPS and perforated XPS panels are small, but the latter can be improved by increasing the number of channels and the air channels’ diameter. Additionally, the higher the thermal conductivity of the base material, the more significant is the presence of the channels, reducing the effective thermal conductivity. A base material with low emissivity may also reduce the thermal conductivity.

Stability of the Plane Bingham–Poiseuille Flow in an Inclined Channel

We study the stability of laminar Bingham–Poiseuille flows in a sheet of fluid (open channel) down an incline with constant slope angle β∈(0,π/2). This problem has geophysical applications to the evolution of landslides. In this article, we apply to this problem recent results of Falsaperla et al. for laminar Couette and Poiseuille flows of Newtonian fluids in inclined channels. The stability of the basic motion of the generalised Navier–Stokes system for a Bingham fluid in a horizontal channel against linear perturbations has been studied. In this article, we study the flows of a Bingham fluid when the channel is oblique and we prove a stabilizing effect of the Bingham parameter B. We also study the stability of the linear system with an energy method (Lyapunov functions) and prove that the streamwise perturbations are always stable, while the spanwise perturbations are energy-stable if the Reynolds number Re is less than the critical Reynolds number Rc obtained solving a generalised Orr equation of a maximum variational problem.

Characterisation and Modelling of Gravity Pre-Concentration Amenability Using LST Fluidisation in a REFLUXTM Classifier

Samples of the feed, underflow and overflow from water-based separations conducted using a continuous REFLUXTM Classifier involving inclined channels with a 3 mm spacing have been fractionated. Another REFLUXTM Classifier operating in a semi-batch configuration using a dense fluidising medium of lithium heteropolytungstates (LST) was used to determine the density distributions of the three streams. The partition surface of the separator was quantified, and the technique was validated against sink/float data for a −300 + 38 µm chromite ore separation. It was found that the LST flow fractionation determined the D50 with remarkable accuracy across the entire size range, with the Ep values also very good above 75 µm. For water-based continuous separations involving a gold ore covering the size range −1.0 + 0.090 mm, the D50 varied with particle size to the power −0.22 and the Ep remained relatively constant at approximately 170 kg/m3 for each of the narrow particle size ranges. These results were consistent with the partition surface validated based on the much finer size range of the higher density chromite ore. The performance of the continuous system was then modelled, with the results shown to agree well with separations conducted on the feed. This approach has been developed as an alternative to using the sink/float test, thus offering a new option with both a lower cost and minimal health and environmental risk. The findings from this study can in turn be used to assess the amenability of a given ore to gravity pre-concentration.

CONVECTIVE MIXING IN AN INCLINED CHANNEL CAUSED BY TERNARY DIFFUSION UNDER CONDITION OF INCREASING DENSITY OF THE MIXTURE WITH HEIGHT

Using methods of numerical simulation, we studied the quasi-stationary mass transfer of isothermal ternary gas mixtures in the vertical and inclined channels for the zone of flow exit from a given channel into the lower flask of a diffusion cell. Convective mixing is considered under conditions involving an increase in the density of the mixture with the height of the channel. The characteristic features of structured flows were studied at a certain content of the component with the highest molecular weight in the mixture. The convective formations in the vertical and inclined channels are compared. The dynamics of structured convective flows at various inclination angles is analysed. Estimates of the lifetime of a structural formation consisting mainly of the component with the highest molecular weight moving in a gas mixture with a lower density value are given.