Numerical simulation of non-stationary regime of a submerged combustion setup operation

Abstract

Relevance. The need to evaporate large quantities of brines at potash industry enterprises. Evaporation of brines in surface evaporators is difficult due to the encrustation of heat exchange surfaces by salt deposits. Therefore, such evaporation is most expedient to be carried out in submerged combustion apparatuses, since they do not contain heat-transmitting surfaces. However, in this type of apparatus, malfunctions may occur due to uncontrolled solid phase deposition. At the moment, the dynamics of the solid phase in submerged combustion devices is poorly studied. This study is part of a scientific program aimed at a comprehensive review of the laws of motion of solid particles in submerged combustion apparatuses. Aim. To study the hydrodynamic processes in the submerged combustion setup in the time interval corresponding to the beginning of its operation; describe the patterns of solid phase motion as a function of time. Object. Laboratory setup of submerged combustion. A simplified model of the thermal mode of operation without the subsequent transition of the liquid phase to steam is analyzed. Methods. The study was conducted by numerical experiment. The hybrid finite volume method was used in simulation in combination with the technology of the finite element method. The multiphase system was considered as two coexisting subsystems: gas–liquid and liquid–solid. Results. The paper considers the final time interval of the setup operation. It is found that during the time under consideration, a stationary mode of solid particle deposition is achieved. The authors have detected liquid flow velocity oscillations, leading to fluctuations in the mass flow rate of solid particles at the bottom of the setup. It was found that the velocity at the tip of the flue gas jet escaping from the burner nozzle, as well as the pressure at the nozzle section, have a similar form of oscillation. The authors substantiated the hypothesis about the determining influence of the instability of the jet movement of flue gases on the oscillatory behavior of the entire hydrodynamic system.

Keywords

• submerged combustion
• numerical modeling
• unsteady mode
• three-phase flow
• gas–liquid–solid
• sedimentation