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The majority of the power plants in India are fed with non-coking coals where the coals are dispatched from their respective mines via wagons loaded by a rapid loading system or pay loader. The usual top size of coal is 200 mm and sampling is carried out manually from wagons. The manual method of wagon-top sampling of large size raw coal is not only difficult but also violates some of the fundamental principles of sampling. As per sampling requirements, samples are to be drawn from the full depth of the wagons, which is impossible to be done manually. Since the ash distribution in the different size fractions is not homogeneous, the results from the samples, which do not reflect the true size distribution of the lot, are likely to be biased. More importantly, sample collection by shovel from the top is a function of human discretion and not governed by the equiprobability rule. In another case, the sample has been collected by a cross-belt type auto mechanical sampler for 200 mm size coal at one o...

The settling rate of coal fine particles by interaction with proper coagulants and flocculants is important in the water treatment/dewatering process. The standard test for measuring sedimentation rates is the jar test; the method is simple and direct. However, this method suffers from a number of disadvantages, despite its widespread application, it runs the risk of introducing large error due to the possible misinterpretation of the interface and the error may vary from person to person. To overcome this problem, different methods have been used for measuring the settling characteristics. In the present article, a German-made DCAT-11 instrument having bottom load weighing facilities synchronized with a computer to record the data and having facilities to measure up to 0.01 mg accuracy was used for testing a coal fines sample collected from an operating coal washery. The results show that the data obtained by the jar test are replicated by the data obtained from the instrument.