Gray-King assay

B Just coherent, breaks into powder on handling 

G Hard, no shrinking, same volume as original coal (standard) 

G3 Highly swollen, fills tube without length change 

G9 Very strong swelling with increased length 

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Board Rank Code Numbers are pardy assigned on the Gray-King assay and pardy on the volatile matter. The Gray-King assay procedure can also permit evaluation of yields of tar, gas, and Hquor. 

Coal Rank Gray-King Assay Volume of gas... 

It appears that the discrepancy in the results reported above is caused chiefly by the difference in the method of conducting the coal-sulfur reaction. If coal and sulfur are mixed intimately (in 2 1 proportion) and heated in a Gray-King assay retort from room temperature to 360°C. for one hour and maintained at this temperature for another hour (as was done by Mazumdar et al. (17, 18) in their initial studies on coal dehydrogenation), followed by... 

Two samples of coke prepared at 600°C. were crushed to 72 B.S. mesh size and treated with hydrogen from 300-600°C. for an hour, and the treatment was continued for another hour at 600°C. (to simulate Gray-King assay conditions). The stream of hydrogen gas (including other gases formed) was collected. The gas was analyzed, and the results are presented in Table VII. 

The assays are conducted at 500°C or 600°C (930°F or lllO F), even though they tend at these temperatures to underestimate gas volumes and to show maximum tar plus light oil yields, and both are sufficiently precise to yield mass balances of 100 0.3%. The Gray-King assay can also be carried out at 900°C (1650°F) to provide information about the quality of the solid residue. 

Some of the most common methods to evaluate the suitability of a coal or coal blend for coke production are the free-swelling index test, Gray-King assay, Roga assay, various dilatometer tests, and Gieseler plastometer test. In addition, research using larger amount of coal sample is also performed by means of a pilot coke oven. 

Table 3.10 Gray-King assay coke types [11],...

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