Ship motion induced moisture migration modelling of an unsaturated coal cargo

Mining, processing and shipping of bulk commodities has increased to record levels over the last decade, largely aimed at fuelling the demand for ironmaking and other raw material needs in China. This has required the development of many new ore and mineral resources that are mined below the water table or are subjected to wet mineral processing operations. In other cases, the ores and minerals are simply mined in high rainfall areas. This has made the measurement and control of moisture content a critical issue for safe and economic production and export for most mining companies. It is well known that the migration of liberated moisture from bulk materials can occur through the materials handling chain from pit to port and beyond. It is not uncommon to observe saturated layers either at the base or on the top of bulk material systems after undergoing some type of vibration or oscillation during its journey. These saturation layers have occurred from train wagon and truck journeys, during belt conveyor transportation, and within the holds of ships during maritime transportation. This research aims to develop a simplified model to estimate moisture migration within a bulk commodity induced by oscillatory ship motions, in particular, during coal shipments. The simplified model integrates likely wave induced ship motions, experimental moisture migration results and likely significant storm occurrences through the transport route. Using the simplified model, two coal cargo journeys from Australia to South East Asia within a Panamax size ship and to Europe in a Cape size ship were assessed. The ship bilge pump records were compared to the predicted model which showed an accuracy of at least 92% and 96% for predicting the amount of moisture migrated to the bilges throughout the journey.