A Novel Two Degrees of Freedom System for Measuring Iron Ore Water Content on a Conveyor Belt

Water content or moisture of materials is a parameter widely used in the industry. In mining, it is an important variable to control in iron ore production. High moistures may cause instability of iron ore piles and may make transport by ship unfeasible. Therefore, this paper presents the development of a system for measuring iron ore moisture on a conveyor belt (laboratory-scale). The structure that supports the sensor has two degrees of freedom, which allow perpendicular and parallel movements. The parallel movement makes the relative velocity between the measurement cell and the ore almost zero. The vertical movement allows the sensor to be placed at different depths in the ore. These sets enable real-time and in situ measurements. The system uses the capacitive method to determine the dielectric constant of the iron ore located between the sensor electrodes and, consequently, the moisture. This system has a measuring range of 0 to 14% on a dry basis and presents an uncertainty up to 0.07 percentage points for a 2-standard-deviation confidence level. In the validation process, the absolute error was less than 0.34 percentage point in the mining interest range of 6 to 14%. The founded results achieve a significant advance in the development of real-time equipment for measuring ore moisture since there is no device capable of doing it with the necessary level of accuracy and precision. For mining, this kind of system represents a big step to take corrective and preventive decisions around iron ore moisture control.