The production of ultra clean coal by sequential leaching with HF followed by HNO3

Steel, KM and Patrick, JW (2003) The production of ultra clean coal by sequential leaching with HF followed by HNO3. Fuel, 82 15-17: 1917-1920. doi:10.1016/S0016-2361(03)00149-2


Author Steel, KM
Patrick, JW
Title The production of ultra clean coal by sequential leaching with HF followed by HNO3
Journal name Fuel   Check publisher's open access policy
ISSN 0016-2361
Publication date 2003-10-01
Sub-type Article (original research)
DOI 10.1016/S0016-2361(03)00149-2
Volume 82
Issue 15-17
Start page 1917
End page 1920
Total pages 4
Publisher ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND
Language eng
Abstract A UK bituminous coal with particle size < 62 mum and containing 5.0 wt% ash and 2.4 wt% S was treated with a two-stage leaching sequence of aqueous HF followed by aqueous HNO3. The ash and S contents reduced to 0.2 wt% and 1.3 wt%, respectively. In addition, the calorific value (CV) dropped from 31.5 to 29.5 MJ/kg, and the N content increased from 2.0 to 2.8 wt%, due to attack on the carbonaceous matrix during the HNO3 leach. Interestingly, this attack only occurs when HNO3 reacts with and dissolves pyrite, suggesting that it is the products of reaction between HNO3 and pyrite which react with the coal. It is proposed here that localised concentrations of sulphuric and nitric acids at the pyrite site may react to form the powerful nitrating agent NO2+ which then reacts with the carbonaceous coal matrix. The fluoride content of the coal increases from 80 to 3240 ppm after the HF leach, yet drops to 130 ppm following the HNO3 leach. The mineral matter remaining in the coal after the leaching sequence consists largely of Fe, which is most likely present as finely disseminated unreacted pyrite.
Keyword Ultra clean coal
Coal demineralisation
Hydrofluoric acid
Nitric acid
Pyrite
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Engineering, Architecture and Information Technology Publications
 
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Created: Sat, 11 Jul 2009, 01:25:47 EST by Dr Karen Steel on behalf of School of Chemical Engineering