On-line Capacitive Moisture Measurement of Iron Ore Concentrate

Abstract

Accurate moisture determination of iron ore concentrate, also referred to as ore concentrate, is important to the production of iron ore pellets. Existing methods have long response times, sampling variability and/or require manual work. Capacitive methods for moisture determination show promising signs of solving several of these problems.

To determine the feasibility of constructing an on-line measurement sensor utilising capacitive methods, a small-scale prototype consisting of a rotary conveyor dish, a capacitive sensor and measurement electronics was constructed. The sensor consists of two pairs of electrodes, each of which constitutes a capacitor with the surrounding material as dielectric. By placing the sensor below the rotational dish, allowing the measured iron ore concentrate to compose most of the dielectric medium, its permittivity, which will vary with its moisture content, can be measured as a change in capacitance.

Testing was performed to determine the effects of varying frequency, mass and speed of the measured material. The results show that even though there seems to be a strong correlation between the measured capacitance and the moisture content, it is hard to draw any direct conclusions on the correlation due to high local variability in the material, leading to uneven sampling and poor verification tests. Further tests on a larger scale are suggested to remedy these problems.