Over the years, coal sampling has grown from the original, simple slurry samplers to multi-stage sampling systems that have become more and more comprehensive in order to accommodate rapidly changing sampling requirements and increased tonnage flow rates. As an example, it is not uncommon today to be confronted with coal feed rates as high as 10,000 t/h and with the maximum coal particle size sometimes exceeding 6 inches.
Coal is one of the most difficult materials to sample, due to its variability in composition between non-combustible particles to those which lend themselves to complete burning. The sampling responsibility is further complicated by the objectives to be realized in analytical examination variable and sometimes very high moisture contents, the presence of clay, the size of the lot or consignment to be represented by the sample and finally the degree of sampling precision required.
The proper collection of the sample involves an extensive understanding of the physical characteristics of the coal, the minimum number and weights of increments to be taken, the size consist of the coal and the overall sampling precision that is required.
This paper does not intend to present any new sampling techniques or theory but will confine itself to some practical aspects of coal sampling in the USA.
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