Mass Balance Minerals Processing Plant. In a minerals processing plant, some main flows are monitored in line to follow the production. When there is a project in the plant (improvement project or expansion project) accurate information of all flows in the plant are required. This is done through manual mass measurement and characterization of the flows in the laboratory. The results of the measurements and the lab analysis are used in a specific software tool that allows us to simulate the whole plant. The thesis consists in performing field work (measuring the flows and taking samples for the laboratory), assisting the laboratory for the analysis and modelling the plant and looking for potential improvements that can be applied to the ordinary procedure..