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BOND INDEX & HARDGROVE GRINDABILITY INDEX TESTS FOR BIOMASS & COAL
Orla Williams a*, Carol Eastwick a, Ed Lester a, Donald Giddings a, Norman Byrne b a Efficient Fossil Energy Technologies EngD Centre, Division of Energy and Sustainability, Faculty of
Engineering, The University of Nottingham, University Park, Nottingham NG7 2RD, UK b EDF Energy plc., Production Performance Team, Cottam Power Station, Outgang Lane, Retford,
DN22 0EU, UK Abstract:
Biomass power and co-firing provides a significant proportion of bioenergy in Europe, however operational issues with storage, conveyance and milling have restricted the use of biomass in coal fired power stations. One of the main issues in selecting biomasses for power generation, which will be used in coal mills, is estimating their grindability and energy consumption in comparison to coal. Traditional gauges of coal grindability such as the Hardgrove Grindability Index have been shown to be ineffective in predicting the grindability of poor coals, coal blends and biomass. The Bond Index has been developed to estimate the energy consumption of materials in full size horizontal tube and ball mills, but limited testing has been conducted to assess its effectiveness on biomasses. A correlation between Bond Index and Hardgrove Grindability Index is known for coals, but has not been tested for biomasses.
In this study, several biomasses, including olive cake, wood pellets, and eucalyptus pellets, and one standard Columbian coal used in UK coal fired power stations, were tested for the Hardgrove Grindability Index under BS 1016-112:1995 / ISO 5074:1994 standards. The same fuels were then tested in a F.C. Bond Index Testing machine. The olive cake and coal were sieved to 3.35 mm prior to testing and the biomass pellet samples were milled as received to replicate standards in industry. The biomass was sieved to 1 mm and the coal to 75 micron to replicate the final product size required for the two fuels for combustion so that a realistic comparison of the final required product could be conducted. Additionally the removed sample for each run was subjected to proximate analysis and intrinsic analysis in a Thermogravimetric analysis tester. Keywords: Bond Index, Hardgrove Grindability Index, Biomass, Comminution
Acknowledgement: This research is funded and supported by the Biomass & Fossil Fuel Research Alliance (BF2RA) and EDF Energy plc., as well as the Research Council UK (RCUK). The project is an Engineering Doctorate at the Efficient Fossil Energy Technologies Engineering Doctorate Centre in the Department of Chemical Engineering at the University of Nottingham. The authors would like to thank RCUK, BF2RA, EDF Energy plc and the Efficient Fossil Energy Technologies Engineering Doctorate Centre for financial support and guidance. * Corresponding author: e-mail: [email protected]