On-line analysis of coal is the analysis of coal on a conveyor belt. The largest companies in Indonesia, China,Taiwan,Vietnam and Thailand are all using this technology, first developed in Australia by Scantech. The key to the successful implementation of Scantech on-line analysis is that results are presented in real time and, if required, operators can make immediate changes to their operations to ensure product quality.
Dual Energy Transmission (DUET) is the most commonly used on-line ash measurement technique. The COALSCAN 2100 makes use of this technology. New developments in the DUET ash measurement technology permit coal depths up to 400mm in some cases to be measured. This technology is perfectly suited to monitoring the loading of ships from barges where multiple coal sources may be blended to meet contract specifications.
For example, in Indonesia, operators have to manage up to 72 x 1.5 kg samples per barge (8,000 tonnes) and then send those samples to shore for analysis. Control over coal deliveries can instead be maintained by a COALSCAN 2100 monitoring the coal quality in real time. However, this measurement technique can have problems of inaccuracy due to changes in ash mineralogy. Fortunately, there are now methods for coping with this.
On conveyor belt elemental analysers, known as the COALSCAN 9500X, are now available to analyse the entire stream, avoiding not only the operating and capital costs of sampling, but also the sensitivity of older technologies to variation in ash mineralogy. This technology is known as Prompt Gamma Neutron Activation Analysis (PGNAA). As well as measuring ash, this technology measures the ash oxides and many other parameters useful for efficient plant control. There have been four generations of this analyser, with the latest model requiring minimal maintenance, has very low levels of external radiation and drift-free analysis. The modern designed analysers, such as the COALSCAN 9500X, are now installed directly around the primary belt, and so measure all the material of interest. Direct on-belt analysis of the material of interest has numerous advantages, the most important being that all of the material of interest is ‘seen’ by the analyser, so that there can be no errors from sampling, both by the by-line sampling technique and that used by laboratories for analysis.
Analysers that employ PGNAA technology have the capability to measure the concentration of a number of key elements. With the measurement of the sulphur, and with the use of blending software, the end user can control SOX output levels from the stack by adding a low concentration sulphur coal with a higher concentration coal to produce a resultant product that will ensure that emission levels are within the regulatory levels.
These technologies can all be combined with the microwave moisture monitor, so that a complete analysis of the coal is available in real time. Scantech also produces stand alone moisture monitors. The TBM 210 was developed about 25 years ago. The Scantech moisture analyser measures both the changes in phase and attenuation of the microwave signal, making it the most accurate analysers on the market. It is installed at many sites to assist, for example, monitoring moisture levels in of coal shipments, optimizing washery performance and maintaining appropriate levels of dust suppression. The TBM 230 has recently been introduced. This new moisture monitor penetrates coal bed depths up to about 600mm.
The results from on-line analysis are updated every one, two or five minutes as compared with the laboratory analyses of samples, which may be available hours or even days after the coal has been processed. This delay is even longer for samples collected in remote barge loading facilities. Further, it must also be recognized that no matter how accurate the laboratory analysis is, it is always based on a few grams of sample. There will always be errors involved with sampling, dividing, crushing and then preparing a few grams of sample to represent many thousands of tonnes of coal.
To maintain each analyser, Scantech has developed an extensive service network. The analysers are inherently very reliable and remote access via the internet to most analysers results in any problems usually being rectified very quickly. Additionally, a worldwide group of service agents and Scantech’s own service engineers are available for remote and rapid on site support.
Analysers can be used in many applications; at the mine, the preparation plant, to control train/vessel loading, to monitor received coal at the power station and to measure the coal quality fed to the bunker. Operators can control their plants according to the coal quality they are actually processing, not what they think they are processing. This leads to more efficient plant operations and better asset management. On-line analysis allows more efficient use of the resource, more effective process control and more cost effective methods of mining, processing and burning of coal. On-line analysis should be viewed not simply as an alternative to laboratory analysis. The most beneficial on-line analyser installations are generally those where the user has realized the advantages that real time analysis can bring to their process.