How is grindability 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.

What is the standard grindability of a coal?

2.2. The standard method of coal grindability is called Hardgrove (ASTM D409), though this method does not provide reproducible and repeatable results for hard coal.

What is grindability test?

The Bond Ball Mill Grindability test is designed to give a measure of the grinding characteristics of a material by finding the amount of size reduction resulting from a controlled energy input. The grindability is useful in evaluating power requirements for grinding.

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.

Which type of coals have 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 HGI used for?

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.

Which coal has the highest grindability index?

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 ore grindability?

The resistance of ore samples to breakage (or hardness) is measured through grindability testing. Several grindability tests have been developed over the years for different applications and each test has its own strengths and weaknesses. Grindability testing is a compromise between test cost and its deliverable(s).

What is the GCV of Indonesian coal?

High GCV Indonesian Coal

Gross Calorific Value 6000 Kcal / Kg
Total Moisture 12-15%
Ash 8-15%
Volatile Matter 38-43%
Size 0- 50 mm

Which type of coals are non caking in nature?

Only bituminous type of coal can be coked. Explanation: Only that coal which has tendency to soften, swell and stick together during strong heating in absence of air can be coked. This property is found only in the bituminous type of coal.

Which coal has maximum percentage of carbon?

Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.

How is the grindability of torrefied biomass determined?

If torrefied biomass has to be used in the existing coal boilers, the grindability of torrefied biomass needs to be determined. Grindability of a material relates to the rate of energy required for grinding from an initial size to a specific particle size distribution.

Which is the best biomass for Hardgrove Grindability?


How are wood pellets and torrefied biomass grindable?

In this study, the effect of torrefaction temperature on the specific grinding energy consumption and the grindability of torrefied wood pellets and wood chips was investigated and compared with that of coal. The applicability of three well-known grinding equations (Kick, Rittinger and Bond) was studied for the torrefied biomass using a knife mill.

How is the bond index used in biomass?

Bond Index Test can be used on biomass to analyse the grinding performance and behaviour of biomasses in a tube and ball mill Allows analysis of impact of different target particle size on grindability Mimics mill chocking and shows impact of pellet particle size on milling behaviour Matching P 80