A Novel Rotary Dryer Filled with Alumina Ceramic Beads for the Treatment of Industrial Wastewaters: Numerical Simulation and Experimental Study

Abstract

In this study, a new type of rotary dryer filled with inert alumina ceramic bead (ACB) fillers was introduced to treat the industrial wastewater, e.g., the high-salt wastewater and landfill leachate. Numerical simulations based on the Discrete Element Method (DEM) on the motion trajectory of ACB fillers in the rotary dryer were conducted, and the parameters of flight structure, rotational speed, and filling degree on the dynamic behavior of ACB fillers were optimized. Under various rotational speeds and filling degrees, the experimental results fit the numerical-simulated results very well. The optimized flight configuration was the straight flights with a length of 65 mm, and the optimized rotational speed and filling degree were 35 rpm and 15%, respectively. Under the optimized condition, both the response variables, the mass of particles in the airborne phase (MAP) and the percentage of occupied area in the airborne region (OAR), have the optimal values, in which the dryer will have a better drying performance. Besides, the lower-right area of the drum is empty which is convenient for the installation of the inlet pipe. The drying experiments of industrial wastewaters were also studied using this ACB filled rotary drum dryer under the optimized conditions. Under the optimal operational conditions, the evaporation capacities of the high-salt wastewater and landfill leachate could reach as high as 49.7 kg/h and 90 kg/h, respectively. This study highlights the integration of evaporation and drying processes of this novel ACB filled rotary dryer and provides an efficient and zero-liquid-emission strategy for the thermal treatment of industrial wastewater.

DEM Simulation of a Rotary Drum with Inclined Flights Using the Response Surface Methodology

“…The response variables were the mass of particles in the active phase (MAP) and passive phase (MPP). This is because the mass and heat transfer between gas and liquid occurs mainly at the surface of the beads in the active phase [23,35,36]. Therefore, MAP is the response variable that is essential for improving gas-liquid distribution and increasing the efficiency of the rotary drum dryer.…”

“…In the application scenario of high salt wastewater treatment, the wastewater can form a film on the surface of the beads. After drying, the residue solids on the surface of the beads can be crushed into powders [23,24], At the exit, the beads can be separated from the solid materials. Nevertheless, there are few studies on the movement of beads in drums.…”

Mathematical Modelling of Rotary Drum Dryers for Alfalfa Drying Process Control

“…-Equation (10), to obtain the mass flow rate of evaporated water G EV(I−C) from the first zone I − C (Figure 1), knowing the product moisture content X I and X C ; -Equation (17), to obtain the mass flow rate of evaporated water G EV(C−E) from the second zone C − E (Figure 1), knowing the product moisture content X I , X C , and X E (as it is forced to be equal to 0.111); -Equations ( 5), ( 8), (14), and (15), to obtain the four unknowns (i.e., the three temperatures T AI , T AE , and T AC , as well as the length of the first zone of the drum L I−C ). The wet-bulb temperature T WB and the air mass flow rate G DAI also appear in the system of equations.…”

“…Considering design guidelines regarding the thermal-hygrometric aspects of rotary drum dryers, the classic ones proposed by Perry et al (2019) [13] are well known, based on equations of the thermal-hygrometric exchange, and simplified and integrated by empirical indications. Again, with regard to the design, computational methods based on finite element analysis have also recently been proposed [14][15][16]. These methods are very useful for analysing and verifying the thermal-hygrometric and fluid dynamic phenomena inside the rotary drum after the dimensions, flow rates, and temperatures have been set.…”