Chemical transformation of iron compounds during the process of coal pyrolysis in steam

Chemical Decomposition of Iron in Spanish Coal Pyrolysis Identified by Mossbauer Spectroscopy at Different Temperatures

“…Guided by the shape of the spectra (at RT and 80 K) of AA6 char produced at 673, we fitted both in terms of three quadrupole doublets (R, J, P) and they are assigned to rozenite, jarosite and pyrite, respectively. These results are consistent with those reported by Komraus and Popiel (1994). They found that at temperatures below 673 K, the pyrolysis process practically does not change the composition of iron minerals from that observed in the starting coal.…”

“…The corresponding hyperfine Mossbauer parameters are listed in Tables 6 and 7. Mossbauer spectra of BCA chars (Figures 3a, 3b, 3d, 3e and Tables 6 and 7) produced at 673 K and 773 K are well described by superposition of two sextets and two doublets (Sid, P), whereas the two sextets are accounted for the A and B sites of magnetite (Komraus and Popiel 1994). The other doublets Sid and P are respectively close to siderite, Fe/MgCO 3 (Srivastave, 1983) and to pyrite, FeS 2 (Montano, 1977).…”

Chemical Decomposition of Iron in Spanish Coal Pyrolysis Identified by Mossbauer Spectroscopy at Different Temperatures

“…Guided by the shape of the spectra (at RT & 80 K) of AA6 char produced at 673, we fitted both spectra in terms of three quadrupole doublets (R, J, P) and they are assigned to rozenite, jarosite and pyrite respectively. These results are consistent with those reported by Komraus et al (1994). They found that at temperatures below 673K, the pyrolysis process practically does not change the composition of iron minerals from that observed in the starting coal.…”

“…The corresponding hyperfine Mossabuer parameters are listed in Tables (6, 7). Mossbauer spectra of BCA chars (Figs.3a, b, d, e and Tables 6, 7) produced at 673K and 773K are well described by superposition of two sextets and two doublets (Sid, P), whereas the two sextets are accounted for the A and B sites of magnetite (Komraus and Popiel 1994). The other doublets Sid and P are respectively close to siderite, Fe/MgCO 3 (Srivastave, 1983) and to pyrite, FeS 2 (Montano, 1997).…”

“…However, the quadrupole splitting is highly sensitive to such identification. Komrous and Popiel (1994) have further showed that during the pyrolysis processes of coal in a steam water atmosphere, the whole pyrite is transformed into iron oxides (Magnetite, hematite) at temperatures above 873 K. Consequently, goethite in these chars is probably considered the intermediate phase of iron oxides at low temperature pyrolysis. The three characteristic magnetic sextets of pyrrohotite (Fe 1-x S) are clearly identified in the Mossbauer spectra at 80K (Fig.2 right).…”