Use of teoslometers to determine the Moisture Characterization Point in ores

摘要

The Moisture Characterization Point (MCP) of an ore is based on the moisture behavior in the unsaturated pores, close to but below the field capacity of the ore. The MCP is an alternative method to determine safe moisture limits for the shipment of ore as compared to geotechnical test methods used to determine the Transportable Moisture Limit (TML) in ores, such as the Proctor Fagerberg test.In this study a soil tensiometer (Hensley 2009) was adapted to measure the suction pressure (pF) as function of the moisture content in the ore. The Moisture Characterization Point (MCP) was defined as a suction pressure of-0,25 bar. This point is below, but relative close to, the field capacity of the ore. The MCP was correlated with the physical and chemical properties of the ores, like particle size, specific surface area and mineral composition of the ores.The results showed a wide variation in the MCP's for nine different ores, varying between a MCP moisture content of 3.8% up to 21.5 %. The results where compared with the TML limit based on the Proctor Fagerberg tests. For most ores the MCP and TML levels are close (on average a relative difference of 10% between the TML and MCP). For ores with a substantially larger difference then 10%o, the ores mineralogy is a dominant factor. The ore mineralogy could be linked to the ore surface area, leading to the conclusion that shipment of ore with goethite content above 35%> is not liable to liquefy.A better understanding of the moisture behavior in ores has assisted in the development of safer cargo schedules (HVIO 2013) to ensure the safe shipping of bulk cargoes.