Development of enhanced sulfur rejection processes. Technical progress report, sixth quarter, 1 January 1994--31 March 1994

摘要

Recent work identified two major reasons why advanced coal cleaning technologies fail to meet a 90--95% rejection of pyrite from coal. They are: superficial oxidation of pyrite as an inadvertent corrosion-type process occurring during mining and processing, and (2) incomplete liberation of pyrite from coal causing a large fraction of the pyrite to remain associated or locked with the coal as middlings. Research suggests two solutions to these problems; Electrochemically-Enhanced Sulfur Rejection (EESR) and Polymer-Enhanced Sulfur Rejection (PESR) processes. The EESR concept uses sacrificial anodes to prevent the oxidation of pyrite. This technique is flexible enough to be implemented during the process of grinding, conditioning or flotation. The PESR process is based on synthesizing polymeric organic reagents whose functional groups react with pyrite, possibly via an electrochemical mechanism, while the hydrophilic polymer chains are stretched over the coal inclusions, rendering the pyrite-coal composite particles nonfloatable. The overall objective of this research is to develop these processes into technologies for improving the rejection of pyritic sulfur from eastern US coals. The objectives of the research carried out during this report period were: to complete characterization of the (minus)100 and (minus)28 mesh Illinois No. 6 pyrite; to review all fundamental studies completed to date on pyrite; to assess the results of microflotation tests and the effectiveness of polymeric depressants for the purpose of planning the next phase of research that is directed at evaluating and optimizing the depression of pyrite using electrochemical control and polymeric depressants. The most significant and reliable results obtained from research to date are presented.