A new method for the simultaneous determination of pyrite content and proximate analysis in coal and lignite

Abstract

Coal Analysis is ordinarily divided into three parts: (1) Proximate analysis, determination of moisture, volatile matter, fixed carbon and ash contents; (2) Ultimate analysis, determination of carbon, hydrogen, sulfur, nitrogen, sometimes phosphorous, ash and oxygen contents; and (3) Calorific value, determination of heat developed by burning a unit weight of fuel. For many coals, economically important calorific values can be accurately determined ((+OR-)1% uncertainty) by the use of proximate analysis only and provides an alternative to the ASTM method. Analysis of sulfur in coal or lignite is environmentally important. With renewed emphasis in alternatives to petroleum fuels, determination of the pyrite content in coal and lignite is important to aid in sulfur removal. Development of a new simultaneous method for determination of pyrite content and proximate analysis in coal and lignite is presented. It combines thermogravimetry and thermomagnetometry and utilizes inert, oxidizing and reducing gases. Results by the new technique are compared to the ASTM method, one set obtained by us on a Fisher Coal Analyzer and one set by the Coal Research Laboratory of the Pennsylvania State University. Comparison of thermo-magneto-gravimetric-analysis with the ASTM method indicates good agreement and comparable accuracy. These studies show that the thermo-magneto-gravimetric-analysis of proximate analysis and pyrite contents in coal and lignite is a viable, precise alternative to the present, more cumbersome ASTM methods. Principle advantages of thermo-magneto-gravimetric-analysis are: (1) ease of determination of both proximate analysis and pyrite, which permits use of unskilled technicians; (2) widespread availability of the apparatus; (3) cost effectiveness due to use of unskilled operators; (4) automation, presently available for proximate analysis on some commercial instruments and is easily accomplished for pyrite analysis, as well; (5) advantage over pyrite analysis by the ASTM method in two situations: first, when pyrite is totally surrounded by acid-insoluble organic-material and secondly where significant amounts of pyrite have been oxidized to FeSO(,4) and; (6) a permanent record of the measurements, which are continuous, is made in contrast to the ASTM method which records only initial and final conditions.