The fate of As, Pb, Cd, Cr and Mn in a coal during pyrolysis

Transformation of As, Pb, Cd, Cr, and Mn in Chinese Datong coal during pyrolysis was studied. Experiments were carried out in a fixed-bed quartz reactor with a heating rate of 20 degreesC min(-1). Effects of the final temperature (300-1000 degreesC) and atmosphere (N-2 and H-2 at 0.1 MPa) were examined. Chemical form distribution of the elements in the coal and coal-derived chars (obtained at 1000 degreesC under N-2 and H-2) was investigated. As, Pb, Cr, Cd, and Mn in the coal and the chars were classified into five chemical forms (ion exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and in the residue) by a sequential dissolution method. Results show that As, Pb, and Cd are more volatile and tend to enrich in the volatile phase in the pyrolysis. Cr and Mn are relative non-volatile and tend to enrich in the solid phase. H-2 atmosphere promotes the release of the elements. The elements in all the five chemical forms undergo transformation in pyrolysis, and As, Pb, Cr and Cd show similar behavior. (C) 2003 Elsevier Science B.V. All rights reserved.