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Hardgrove Grindability Index
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Hardgrove Grindability Index

geology
Also known as: HGI
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Quick Summary

The Hardgrove Grindability Index (HGI) measures a coal's resistance to crushing. This property is influenced by factors like moisture and ash content, with lignites and anthracites generally being harder to grind than bituminous coals.1

The HGI is determined through the Hardgrove test, where a coal sample is ground in a laboratory mill. The percentage of the coal that passes through a 200-mesh sieve (74 micrometres) is used to calculate the index. This index serves as a guide for selecting appropriate grinding equipment in coal-preparation plants. Grindability, along with hardness, affects the type of machinery used for mining and crushing coal, as well as the energy required for these operations.12

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2 Britannica Sources
  1. coal utilization - Grindability
  2. coal - Other properties

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