The minerals industry is understanding the benefits of onbelt microwave monitors being used to provide operators with moisture analysis of their ore every minute. For example, if plants have regular, minute by minute analysis of the moisture content of the incoming ROM, then down-stream processes may be adjusted to achieve greater efficiencies and in fact, increase yields.
One of the most common moisture monitor applications in recent times has been to monitor ore
shipments as they are being loaded, so as to ensure that the moisture content is less that the
transportable moisture limit (TML). TML represents the maximum safe moisture content before the
shipment is at risk of rolling over due to the shifting load caused by excess water in the cargo hold.
Data from an on belt moisture monitor can alert the operators of high moisture content during the loading, who many then decide to stop the loading. Real-Time Instruments has designed, manufacture and market their MoistScan microwave moisture monitor for these purposes. Analyses are updated continuously, which, along with average values, are communicated to the plant usually via 4-20 mA current loop outputs.
Without an online moisture analyser, it is very difficult to measure accurately. Whilst the laboratory
moisture measurement of a few grams of ore is accurate, sampling and preparation errors are often
significant. As soon as the ore is handled, moisture is lost. As it is crushed and divided dust is lost, i.e. the dry fines are being lost and thereby lowering the average moisture content.
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The crushing and dividing process adds heat to the ore, which again dries and lowers the measured moisture content. These problems are greater in heavy, dense ores like copper than in fine, light, homogenous ores. However, an onbelt moisture monitor does not suffer from these issues, providing the operators with an accurate measure of the entire ore body in real-time.
The benefits of having real-time information on the moisture content of minerals include improving
saleable product, dry tonnage accounting, dewatering of ore, to assist in the drying of the ore, dust
control, and quality control.
Increasing Saleable Product
A cost-effective way of increasing saleable ore is through better management of moisture using online analysis and control. A 1% increase in saleable ore can translate into massive improvements in profit margins. Online monitoring of moisture can provide the accurate process control necessary to enable decrease the set tolerance levels for the amount of moisture in ore whilst continuing to provide a product that is within specification.
Dust Management
Online moisture analysis is an essential component of modern dust management systems. Many ores are low in lump content with significant levels of dust particulates. Airborne dust particles can pose a major environmental concern. The MoistScan can be incorporated into a whole-of-site dust
management strategy where multiple analysers are used to monitor the moisture level of incoming and outgoing ores.
The percentage moisture reported by the analysers can be compared to known dust extinguishable moisture levels (DEM’s) for each ore. Where the moisture is lower than the DEM, the right amount of water is added to the belt via automatically controlled spray bars, eliminating dust and preventing overdosing, which is a waste of a precious resource.
Dry Tonnage Accounting
Dry tonnage reconciliation or metallurgical accounting as it is often referred to, is increasingly being
implemented in pit to port mining operations throughout the world. Online moisture analysis enables calculation of dry tonnage as opposed to wet tonnage where only a traditional belt scale is employed.
Typically an online moisture analyser will be installed along with belt weighers at critical measurement points in the process. This is especially the case where change of ownership of the product occurs or where individual business units within a single integrated operation measure productivity.
Dewatering
In many plants, the MoistScan is used in association with dewatering equipment such as centrifuges,
vacuum filters and other solid-liquid separation technology. Water addition commonly begins at the
mine where it is applied to suppress dust, starting at the face and at transfer points and then throughout its transport out of the mine.
Consequently, the material arriving at the preparation plant is already wet. Both economic and practical consideration dictates that water may have to be removed to a predetermined level after it has been processed and before it is dispatched. A MoistScan can be installed to identify if there is too much moisture, thereby causing handling, transportation and safety issues.
Drying
Drying of ores using rotary and other types of dryers is an energy-intensive process. It is also an area where major gains in efficiency are achievable. The MoistScan is used for manual or automated control of dryer parameters so as to optimize residence times of the material in the dryer. In drying processes, the MoistScan is typically employed at either the entry of or exit to the dryer. The information from the MoistScan is used in a PID control loop enabling feed-back or feed-forward control.
Quality Control
One of the most popular uses of the MoistScan in the minerals industry is for quality control as
customers become more discerning and product specifications become tighter. In many processes the amount of moisture is critically important. Too much moisture or too little moisture can result in an endproduct that is out-of-spec causing potential payment penalties, hence it becomes a very useful tool to Quality Control Officers.
Over the last two decades the use of online moisture analysers that provide real-time data on the
moisture content of ore as it travels on a conveyor belt has become increasingly common. Real time
Instruments (RTI) is the global leader in online moisture analysis. With over 700 MoistScan analysers
installed throughout the world, and it is the most popular online moisture analyser on the market today.
In the minerals industries, the analysers are installed at strategic places including on the ROM (Run-of- Mine) belt after the primary crusher, on the outfeed conveyor of an underground operation, on the feed conveyor to the beneficiation plant, on the product conveyor from the beneficiation plant, and on the train load out conveyor after the product stockpile.
Contact Michael Edwards, RTI’s African Sales Manager, MichealE@rtiaustralia.com, to discuss your particular application.
