Chemical characteristics of tars produced in a novel low-severity, entrained-flow reactor

Abstract

aggregation of iron atoms occurred more easily over bituminous coals than brown coals even at the same loading. This is because brown coals have more surface functional groups that can interact with iron species. Conclusions The use of Mossbauer and EXAFS techniques was demonstrated to be quite effective in revealing the type of iron species formed during pyrolysis of Fe(N03)3-loaded brown coal in an inert atmosphere. The main species observed at low temperatures was highly dispersed FeO-OH. At higher temperatures, reduced species, like 7-Fe, a-Fe, and Fe3C, became predominant.The change of chemical forms of iron species during heat treatment was affected not only by temperature but also (30) Yamashita, H.; Tomita, A. Unpublished data. by iron loading. The aggregation and reduction of iron species were rather slow in the low-loading samples.(62603014), is acknowledged. Coal Corporation of Victoria, Australia, kindly supplied the raw brown coal. The X-ray absorption experiments were performed under the approval of the Photon Factory Program Advisory Committee (87-139). We thank Dr. M. Nomura of KEK-PF for his advice in measuring EXAFS spectra. Thanks are due to Dr. A. Kunii of the Faculty of Science and the staff of the Cyclotron and Radioisotope Center at Tohoku University for Mossbauer spectroscopy measurements.

Determination of the Forms of Nitrogen Released in Coal Tar During Rapid Devolatilization

“…This result would be consistent with the presence of dimers in the tar, and helps rationalize the difference between the measured value of MW Cl and the reported values of the average tar molecular weight. 3,11,12 The average molecular weight of attachments (MW δ ) in the tar and char are much lower than that found in the parent coals (see Figure 3). While MW δ decreases steadily with rank in the coals, the values of MW δ in the tars change only slightly with rank, with no distinguishable trend.…”

“…1 The elemental compositions of the chars and tars from these experiments are similar to those seen by other researchers. [2][3][4][5] The results of the solid-state 13 C NMR analyses of the tars from the 1080 K condition were reported in the last semi-annual report. The solid-state 13 C NMR analyses of the chars from the 1080 K conditions have now been completed; this data set represents the first matched coal/char/tar chemical structural data obtained using solid-state 13 C NMR.…”

“…Several sets of data indicate that tar molecular weight distributions peak in the range of 250 to 400 daltons. 3,11,12 The tars in this study have molecular weights per cluster in the range of 170 to 240 daltons. These results seem to indicate the presence of species in the tars that contain more that one cluster per molecule (i.e., dimers and trimers rather than monomers).…”

“…Most NO x in coal combustion systems comes from nitrogen in the fuel, rather than from nitrogen in the air. Practical emission control strategies include burner design strategies (e.g., low NO x burners), overfire air, reburning, selective non-catalytic reduction (SNCR) using reduction agents such as NH 3 or urea, and selective catalytic reduction (SCR). The order listed also reflects the order of increasing costs for implementation.…”

Clean Coal Program Research Activities

“…The chemical structure of coal tar differs significantly from the parent coal as evaluated by 13 C-NMR (Watt et al, 1996;Perry et al, 2000). The average molecular weight of tar produced at atmospheric pressure is ~350 amu (Freihaut et al, 1989). The number of carbons per cluster and the cluster molecular weight are lower in the tar than in the parent coal due to the preferential evaporation of lighter constituents of the metaplast.…”