Abstract

The northern Chile is a zone with large needs of water sources, at present, enforces are dedicated to the use of seawater in the mining operation, which is expensive since the mining operations are located at significant height and large distance from the coastline. Therefore, an economical alternative could be to reduce the water consumption by means of reuse, which requires the removal of impurities (particles or chemicals) of the water before reuse. This may be accomplished by Dissolved Air Flotation (DAF), which is a clarification process used for removing particles in water treatment. The use of DAF for water treatment and reuse (or recycling) is rapidly increasing in the mining sector. A DAF reactor for particle removal was modelled by using computational fluid dynamics (CFD). In order to validate the model, a pilot DAF reactor is under construction, in which experiments will be carried out and the results compared with the CFD simulations. The validated model could be then used in optimization and operation of similar reactors working at other scales, conditions, or configurations; e.g., a multi- step DAF, for saving energy. Basically, the process consists of a coagulation-flocculation pre-processing followed by a cleaning process using DAF. Water containing air dissolved is introduced at high-pressure and air micro-bubbles are formed when the overpressure is released. Micro-bubbles collide with the particles forming bubble-particle bounds, which travel to the surface of the cell forming a particle-laden foam that is removed from the system. The CFD model uses an Eulerian description of the phases: the continuous water phase and the two discrete phases, namely the bubbles without particles and the bubbles bounded to particles. The system is solved for the velocity-fields, the pressure, and the air volume fraction; from these parameters the particle removal efficiency is then obtained.