Modernizing Your Assay Lab for Lateritic Nickel Ore Mining – Observing the Present
The mining sector faces numerous challenges and struggles every day to maximize efficiency while maintaining cost-effectiveness. As part of this two-part series, I will share some experiences on how current practices are applied to a mine-site laboratory in Part 1 and discuss the potential for utilizing the newest technologies in Part 2 to address the challenges and achieve operational goals.
Nickel has become one of the most valuable commodities in the present time. It is also becoming an increasingly important material in global green energy initiatives, particularly in lithium-ion battery development used to power electric vehicles.
As it is widely used in alloys to give other metals the hardness, strength, and corrosion resistance they require, nickel mining continues to grow with Australia, Canada, Indonesia, and the Philippines among the leading markets.
Closer Look at Nickel Mining
Nickel is often mined from two types of ore deposits: lateritic nickel ores and magmatic sulfide deposits. Lateritic nickel ores are formed by intensive tropical weathering of olivine-rich ultramafic rocks like dunite, peridotite, komatiite, and their serpentinized derivatives.
Based on my years of experience involved with the nickel mining industry in the Philippines, a typical operation involves hundreds of samples to be analyzed round-the-clock each day. Trucks transporting the minerals to a stockpiling station are required to make a temporary stop at the sampling station for samples to be taken to the on-site lab for analysis.
Due to the huge bulk of samples that are highly heterogeneous, the proper sampling technique is required to ensure the samples taken preserve the representative character of the bulk material. “Coning and quartering” is one of the common approaches, where the original sample is formed into a cone-shaped pile and then flattened into a disk.
The disk is divided into four quadrants. Two opposite quadrants are shoveled into a second pile, mixed, and then coned and quartered again. This sequence continues until the selected material has been reduced to a size small enough for a useful laboratory sample.
Parameters Analyzed
Most of the time, only three major parameters are analyzed in an on-site laboratory: moisture, flow moisture point, and chemical composition analysis.
As with lateritic ore, the valuable content is in the soil exposed to the elements. Sun and rain will affect the water and moisture content, which will affect the chemical concentration per weight due to dilution factors. As such, it is important for any buyer to know the moisture content and hence determine the actual weight and value of the materials.
On average, the water content in the sample will range from 20 to 50 percent. A simple method of determination is by proper sampling and a quantity of the samples are then weighed before and after being placed in a heating oven, usually at approximately 105 degrees Celsius, for an hour to ensure all trapped moisture are evaporated. The weight difference can then be used to calculate the moisture content of the sample.
Cargoes that contain a certain proportion of small particles and a certain amount of moisture may liquefy when the moisture content exceeds the Transportable Moisture Limit (TML). In the resulting viscous fluid state, cargo may flow to one side of the ship with a roll one way but not completely return with a roll the other way, causing the ship progressively to reach a dangerous heel and capsize suddenly. The TML is determined by sampling the cargo correctly and determining the FMP.
The flow table test is primarily used to determine the FMP of relatively homogenous mineral cargos. The test requires a cargo sample in the form of a truncated cone to be placed on a flow table, raised, and dropped repeatedly, around 50 times, from a measured height.
The elements of values need to be determined as it will define the price of each batch. For typical analysis, Fe, Ni, and Co are the main elements to be determined. However, for mining exploration purposes, all elements need to be known and screening is necessary as some elements will increase or decrease the value of the ore.
Chemical analysis can be performed with various techniques from manual titration to AAS/ICP-OES. Many mining labs prefer the EDXRF method as this technique uses minimal sample preparation, is easy to operate, and provides the fastest sample-to-results. There is no sample dissolution or harsh chemicals involved in the analysis.
Collected samples are dried in an oven, pulverized into a fine powder, and then pressed into a solid pellet using a hydraulic press, which can then be analyzed directly in an EDXRF instrument. Occasionally a sample will be taken for titration analysis for cross-checking.
The mining sector faces numerous challenges including demand uncertainty, operational costs, and productivity challenges. As an on-site laboratory at the mining location always prioritizes the most critical issue by maximizing efficiency while maintaining cost-effectiveness, DKSH is ready to support the mining industry to achieve these operational goals.
We offer a unique set of physical, chemical, and structural analysis solutions designed to support the mining industry in various phases including exploration, ore sorting, process monitoring, and environmental check.
Sources:
About the author
Alan Boey has been in the X-ray analytical instrument business for the past 14 years, servicing various industries from minerals and mining, metal manufacturing to electronics and semiconductor businesses. Alan is now engaged with DKSH as a regional product manager for Southeast Asia, specializing in X-ray analytical instruments and providing solutions to fulfill market requirements in material analysis with X-ray diffraction techniques as well as elemental determination via X-ray fluorescence methods.
