Nickel and Chromium Speciation of Residual Oil Combustion Ash

Abstract

Ash from a low-and high-S (0.33 wt% and 1.80wt% S, respectively) residual oil was produced using a laboratory-scale combustion system at excess O 2 concentrations of $ I and 2 or 3 mol%. High-S ashes are distinguished from low-S ashes by an abundance of (Na, K)x v~+ vtx 0" (0.90> x > 0.54) and lack of (Na, Kj,SO. crystals. Discrete phases of Ni or Cr were not detected using SEM and XRD, even though these metals are relatively abundant -\.5 to 5.5 wt% and 0.08 to 0.1 wt%, respectively. Ni and Cr K-edge XAFS s~ectroscopy analyses indicate that NiSO. and Cr2(SO.h and not the more toxic Ni,S2 and Cr· forms predominate in the ashes. Thermodynamic modeling results support the empirical results in that NiSO•. XH 2 0 and Cr2(SO.h are predicted to be stable low-temperature species in both lowand high-S residual oil ashes produced at S 3 mol% excess O 2,

X-ray Absorption Fine Structure (XAFS) Spectroscopic Characterization of Emissions from Combustion of Fossil Fuels

“…The small variations in the spectra of these PM samples may indicate the presence of additional minor forms of zinc; however, species such as ZnS or zinc ferrite do not appear to be present in significant quantities [10,40]. Alternatively, the variation previous studies [46,47] of commercial ROFA PM and this difference suggests strongly that the short residencetime conditions under which the experiments were run in the experimental furnace are largely responsible for the presence of nickel subsulfide. Hence, to ensure that such potentially harmful species are not formed in commercial operation, it is essential that the combustion be as complete as possible.…”

Nickel Species Emission Inventory for Oil-Fired Boilers

“…These remaining spectral features are consistent with the presence of nickel oxide compounds. 30,41,42 Indeed, the XANES and EXAFS/RSF spectral features in Figure XANES relative step heights, presented in Table 10, are similar because the Ni concentrations in all four ROFAs are also similar (Table 5). A least-squares approach was used to fit XANES spectra for NiSO 4 , NiS, and NiO to the spectra obtained on the Unit B ROFAs.…”

“…However, the RSF spectra are not phase-shift corrected; thus RSF peak positions are .0.3-0.5 Å less than the true distances. XANES and RSF spectra for reagent-grade Ni compounds and synthesized Ni compounds, acquired in previous investigations 28,41,42 were used essentially as "fingerprints" for identifying and quantifying Ni species. In addition to Ni 0 , the following Ni compounds are included in this spectral database: NiS, NiS 2 , Ni 3 S 2 -Ni 7 S 6 mixture, "green" NiO, Ni(OH) 2 …”

Reducing Power Production Costs by Utilizing Petroleum Coke

“…The valance state of V in a baghouse ash was determined using x-ray absorption fine-structure (XAFS) spectroscopy at beam line IV-3 of the Stanford Synchrotron Radiation Laboratory, Stanford University, California. Details of the XAFS spectroscopy procedures have been presented by Huggins and Huffman (14) and Galbreath et al (15,16).…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15] where , is the emissivity of particle and wall, taken as 0.8; F is the Stefan-Boltzmann constant, 1.36 × 10 -12 cal/cm-s K; and T wall is the furnace wall temperature in K. For these calculations, T wall = T g .…”