What does a low Hardgrove grindability index indicate?
The smaller the HGI, the harder is coal texture and less grindable is the coal. Grindability is an important factor for the design a coal mill.
What is HGI of petcoke?
The Hardgrove Grindability Index (HGI) is a measure of coal’s resistance to crushing. Grinding studies, and the resulting HGI, allow many different types of coal users to evaluate how coals will perform in their mills, allowing them to estimate. grinding power requirements and throughput capacities.
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 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 HGI used for?
The Hardgrove Grindability Index (HGI) is used to determine the grindability of the coal. This index is important for gasifiers that require fine coal as feed, as with entrained flow gasifiers.
How is HGI calculated?
The HGI grindability value is calculated from the following formula: HGI = 13+6,93(50-m) The m value is the weight of oversize expressed in grams. The Hardgrove grindability index value is influenced by petrographic composition of coal.
How is HGI measured?
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).
Why is calculating HGI important?
HGI gives the comparative ease of grinding with reference to standard coal. The higher the HGI the lower is the power requirements, and the finer the particle size. HGI represents a fuel that is easier to grind.
How do you calculate HGI of coal?
What is the hardness of coal?
Anthracite differs from ordinary bituminous coal by its greater hardness (2.75–3 on the Mohs scale), its higher relative density of 1.3–1.4, and luster, which is often semi-metallic with a mildly green reflection. It contains a high percentage of fixed carbon and a low percentage of volatile matter.
What is the bond work index?
Abstract: The Bond work index is a measure of ore resistance to crushing and grinding and is determined using the Bond grindability test. Its value constitutes ore characteristic and is used for industrial comminution plants designing.
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