Hardgrove

Hardgrove index Hard lenses Hard metals Hardness... 

R. M. Hardgrove, The delation Tetween Tu/verising Capacity, Power and Grindability, ASME, Chicago, lU., 1993, pp. 6—27. 

The effects of rank on both compressive and impact strength have been studied, and usual minima were found at 20—25% dry, ash-free volatile matter (88—90 wt % carbon). Accordingly, the Hardgrove grindabiUty index exhibits maximum values in this area. 

The development of a continuous grinding index was the focus of work in the late 1970s (59). The laboratory test equipment used is similar to that for the Hardgrove test but permits classifying the product and recycling the oversize material. An improved correlation is obtained that may, however, need to be corrected for the relative sizes of the test grinding balls versus those used in commercial-scale equipment. The continuous grinding index is especially useful for lower rank coals. 

Heating value of the product (SRC) is ca 37 MJ/kg (16,000 Btu/lb). Sulfur contents have been reduced from 2—7% initially to 0.9% and possibly less. Ash contents have been reduced from 8—20% to 0.17% (102). These properties permit compliance with EPA requirements for SO2 and particulate emissions. The SRC is primarily intended to be used as a boiler fuel in either a soHd or molten form (heated to ca 315°C). The soHd has a Hardgrove index of 150 (103). Boiler tests have been successfully carried out using a utiHty boiler. 

Other Tests. The so-called tumbler tests are usually used for testing material like coke, coal, iron ore pellets or tablets. They can be divided into drum tests and ball mill type tests. The latter type is used to derive both the Hardgrove Index and the Bond s Work Index, which are often used to classify the material friability as described in Sec. 3. They are generally more suited to coarse material. The Hardgrove Grindability test requires an initial size range form 595 to 1190 microns. 

Philip L. Walker Hardgrove grindability data for many Pennsylvania anthracites have been determined and reported on in the Proceedings of the 1956 Anthracite Conference held at Pennsylvania State University. 

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