Hardgrove method grindability index

ASTM D-5003. Standard Test Method for the Hardgrove Grindability Index (HGI) of Petroleum Coke. 

Grindability index number that indicates the ease of pulverizing a coal in comparison to a reference coal. This index is helpful in estimating mill capacity. The two most common methods for determining this index are the Hardgrove grindability method and ball mill grindability method. Coals with a low index are more difficult to pulverize. 

In the test method (ASTM D-5003), the coke sample is crushed to produce a high yield of particles passing a No. 16 sieve and retained on a No. 30 sieve. These particles are reduced in the Hardgrove grindabiUty machine according to the test method for coal (ASTM D-409). The quantity of particles retained on a No. 200 sieve is used to calculate the Hardgrove grindability index of the sample. Both this test method and the test method for coal (ASTM D-409) produce the same results on petroleum coke samples. 

Hardgrove Grindability Index The weight percent of coal retained on a No. 200 sieve after treatment as specified in ASTM Standard Test Method D409. 

The Hardgrove Grindability Index was originally developed by Babcock and Wilcox to measure the relative ease of pulverizing coal. This ASTM D409-71 method has since been employed for characterizing other particles as well. The method processes 50 g of air-dried particles screened to a size of 16 x 30 mesh (1180 X 600 pm) in a small ball-and-race mill for 60 revolutions. The amount of material (1 200) passing the 200 mesh (75 pm) screen is then measured. The result is then compared with a standard index to arrive at the HGI or the HGI is calculated from the equation... 

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