How do I find HGI of coal?
HGI for coal is determined by grinding 50 g of sample in a ball and ring type mill for 60 revolutions, after which the product is sieved through a 200 mesh sieve (75 micron screen) (Speight, 1994). HGI is computed by measuring the undersize of the product. Coals with higher HGI are easy to grind (Speight, 1994).
What do you mean by grindability of coal?
The grindability of a coal is a measure of its resistance to crushing. Two factors affecting grindability are the moisture and ash contents of a coal. In general, lignites and anthracites are more resistant to grinding than are bituminous coals.
What is grinder index?
A measure of the grindability of a material under specified grinding conditions, expressed in terms of volume of material removed per unit volume of wheel wear.
How is grindability calculated?
Ball Mill Grindability (Gpb) = (gm/rev) average of last three grinding cycles to give 250\% circulating load.
Which coal has the highest grindability index?
4. Which type of coals have the highest grindability index? Explanation: Grindability is the ease with which a coal can be grounded. The grindability index of pulverised coal is about 100.
What is volatile matter coal?
Volatile matter is defined as the gases driven off when coal is heated to 950°C (1742°F) in the absence of air under specified conditions and is consisted of short and long chain aliphatic carbon atoms (linked in open chains) or aromatic hydrocarbons (one or more six-carbon rings characteristic of benzene series) and …
What is creep feed grinding?
Creep feed grinding is characterized by lower workpiece speeds and higher depths of cut resulting in a larger arc length of contact between the grinding wheel and workpiece when compared with reciprocating or pendulum grinding.
What is grindability test?
A grindability test is a procedure that evaluates the resistance of a material to ball milling. This test is an effective way to calculate and compare the Bond Work Index (BW¡) of different ores. The higher the Bond Work Index, the more difficult it is to grind the material.
What is high volatile coal?
High-volatile bituminous coals (high volatile B and C) are classified using gross calorific (heating) value. High volatile bituminous C coals have calorific values of 11,500 to 13,000 Btu/lb. High volatile bituminous B coals have calorific values of 13,000 to 14,000 Btu/lb.
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