The behavior of Hg release from iron ores during temperature-programmed heat treatment (TPHT) in air is studied, primarily using an online monitoring method. The Hg release behavior during TPHT ...depends significantly on the type of ore being processed, involving the evolved forms, Hg
0
and Hg
2+
, and those that remain thermally stable up to 950 °C. Furthermore, TPHT experiments for model Hg compounds suggest the presence of several types of Hg forms (HgCl
2
, Hg
2
Cl
2
, HgS, HgO, HgSO
4
, and associated mineral Hg) in the considered iron ores. The findings of this study provide insights for designing an efficient method for the removal of Hg from iron ore and gaseous Hg.
In the present the study, the hydrothermal removal of gangue components (Si, Al, and P) from iron ore as a means of producing high-grade iron ore from low-grade iron ore (limonite) is investigated. ...Ores of different types and countries of origin are treated with several kinds of solvents, and the effects of temperature and type of solvent on the extent of gangue removal are rationalized in terms of the chemical and physical compositions of the iron ores used. Relatively good correlation is observed between the Al and P contents of the iron ore specimens used in this study, while the gangue content correlates with the iron content. When the iron ores are treated with distilled water at 16.5 MPa and temperatures up to 350 °C, the removal rate is low, irrespective of the type of iron ore. Furthermore, gangue removal by hydrothermal treatment with 1 M NaOH is higher than those when 1 M NaHCO3 and 1 M Na2CO3 solutions are used. The effects of NaOH concentration and temperature on gangue removal by hydrothermal treatment are investigated using 5 M NaOH, and removal rates of 10–91% for Si, 39–70-% for Al, and 38–76% for P are achieved by treatment at 300 °C for most of the specimens. In addition, there is good correlation between the removal rates of Al and P by hydrothermal treatment with 5 M NaOH. Although the development of pores by calcination of iron ore positively affects gangue removal at room temperature by NaOH leaching, no such effect is observed for hydrothermal treatment with NaOH up to 350 °C. The specific surface areas and pore volumes of the in iron ore specimens decrease after hydrothermal treatment with NaOH. In addition, the α-FeOOH observed in the iron ores before hydrothermal treatment with NaOH is transformed to Fe2O3 in the treated samples. These results demonstrate that this method is effective for converting low-grade iron ores into high-grade iron ores with low porosity, low gangue content, and high Fe content (Fe2O3).
•The gangue in iron ore is removed by hydrothermal treatment to obtain the high-grade iron ore.•Removal extents of 10–91% for Si, 39–70-% for Al, and 38–76% for P are achieved by the treatment.•The FeOOH in iron ore changed to Fe2O3 during hydrothermal treatment.
•Hg evolution profile depends on type of iron ore.•Hg in iron ore exists as H2O, AcOH/HCl, KOH, HCl/HNO3, HNO3 soluble and insoluble fraction.•A large part of Hg in iron ore can remove by H2O ...treatment.•Hg species that evolves until high temperature are mainly H2O soluble Hg.
In this study, to clarify the evolution of Hg during the heating process of iron ore, a combination of sequential leaching and temperature-programmed heat treatment (TPHT) was utilized to investigate the form of Hg in iron ore and volatile Hg species during heating. The TPHT of fractions obtained from the sequential leaching of Indonesian hematite revealed that the water-soluble Hg was composed of Hg species that evolved at both low and high temperatures and at least seven species were identified. One of these species may be HgCl2, which was inferred from comparisons to the TPHT results of model compounds. The Hg species leached in AcOH/HCl and KOH exhibited two evolution peaks in the temperature ranges of 300–600 °C and 500–850 °C, respectively. HNO3-soluble Hg species were mainly Hg volatilized in the range of 750–850 °C. HCl/HNO3-soluble Hg evolved in the range of 600–900 °C and consisted of at least three Hg species. Based on the information obtained through the TPHT of each the fractions mentioned above, the Hg evolution behaviors of five iron ores were curve-fitted and it was determined that the Hg species that volatilized up to 950 °C in all samples were mainly water-soluble Hg species.
Synopsis: Elucidation of Hg morphology in iron ore and the evolution behavior is useful for controlling Hg release from ironmaking industry.
To develop an advanced desulfurization process that can be carried out under mild conditions without pressurized hydrogen or catalysis that has been evaluated for the extraction of thiophenic sulfur ...from a model fuel using the ionic liquids, 1-alkyl-3-alkyl imidazolium alkyl sulfate at room temperature was investigated. Six types of halogen-free ionic liquids with different alkyl chain lengths were prepared. The extraction yield of dibenzothiophene was higher than that of diphenylsulfide and diphenyldisulfide. The extraction yield of dibenzothiophene increased linearly with an increase in the length of alkyl chains and the mass ratio of the ionic liquid to the model fuel. The effect because of the change in the type of solvent was not appreciable, and dibenzothiophene was efficiently removed regardless of whether tetralin, benzene, or n-dodecane was used as the solvent.
The effect of various oxygen-containing compounds added and/or inherent O-species on coal fluidity and coke strength has been investigated in detail. When several O-containing compounds, which have ...different O-containing groups, are added independently to caking coal, the MF value almost decreases, and the extent of the decrease being ether < ketone < lactone < hydroxyl < acid anhydride < < ether/hydroxyl/lactone < carboxyl group. The COOH content in four coals used increases with decreasing C%, and the MF values decrease with increasing the content. The evolution of gaseous O-containing species (CO, CO2, and H2O) during carbonization at 3 °C/min of four coals up to 400 °C has been studied mainly with a flow-type quartz-made fixed-bed reactor to clarify the effect of the amount of O-containing gases evolved with the Gieseler fluidity of coal particles. A positive correlation is found between the amount of CO, CO2, or H2O evolved up to 400 °C and the COOH content in coal. However, a negative correlation between MF and O-containing gases evolved up to 400 °C is observed. It is suggested that the COOH amount and/or O-containing gases evolved have adverse effects on the thermoplasticity of coal. When the indirect tensile strength of coke prepared from pelletized samples is plotted against MF values, a positive correlation is found, whereas an inverse correlation is observed between the indirect tensile strength and COOH in coals used or the O-containing gases evolved up to 400 °C during carbonization. These observations indicate that some of the oxygen-functional groups naturally present in coal have a negative effect on coal fluidity and that this effect is particularly strong in carboxyl, which can readily be decomposed into gaseous oxygen-containing species during heating up to the initial softening temperature.
The behavior of Hg released from iron ores during temperature-programmed heat treatments (TPHTs) in air has been mainly studied using an online monitoring method. The Hg release behavior in TPHT ...significantly depends on the type of ore being processed, which includes forms evolved as Hg0 and Hg2+, and forms that remain thermally stable up to 950°C. In addition, the TPHT experiments for model Hg compounds suggested the presence of several types of Hg forms (HgCl2, Hg2Cl2, HgS, HgO, HgSO4, and associated mineral-Hg) in the iron ores used. The amounts and proportions of suggested forms of Hg species substantially depend on the type and composition of the iron ore used. These observations may be important in designing an efficient method for the removal of Hg from iron ore and gaseous Hg.
The objective of this study was to elucidate in detail the Hg adsorption performance of Cl-loaded carbons obtained after chlorination of rice husk char (RC). Firstly, chlorine ...content/morphology/porosity of Cl-loaded carbons prepared were investigated. Subsequently, Hg adsorption performance of Cl-loaded carbon was tested. The effect of Cl on Hg adsorption was then investigated by comparing the adsorption performance of Cl-loaded carbons prepared from RC and demineralized RC (DRC). Cl content of RC and DRC reached a maximum value at 600 °C, and then decreased by 1000 °C. The pore properties of RC chlorinated residue increased with increasing chlorination temperature. The Hg adsorption performance of the RC chlorinated residues increased with increasing chlorination temperature. The maximum Hg adsorption capacity of RC chlorinated residue obtained at 1000 °C, 10min reached 620 mg/g; the capacity of chlorinated residue treated with DRC at 1000 °C, 10min was larger than that of DRC chlorinated at 600 °C, which is largest Cl content. The adsorption kinetics and isotherm could be expressed by pseudo-first-order and Langmuir equations, respectively. The comparison of the porosity and Hg adsorption of DRC and RC chlorinated residue obtained at 1000 °C, 10min indicated that Cl-adsorbed on the carbon in RC during chlorination may also be involved in Hg adsorption.
Carbon/carbon composites were prepared by pyrolysis of mixtures of coke oven gas tar and low-grade cokes or pyrolyzed chars from lignite and sub-bituminous coals. The indirect tensile strength of ...each composite prepared reached approximately 7.5 MPa, which is comparable to those of high-grade cokes used in commercial blast furnaces. Although the CO2 gasification rates of the composites prepared from low-grade cokes decreased compared to those of the original samples, those of the composites prepared from pyrolyzed chars were almost the same. From the results of mercury intrusion porosimetry analysis and O2 adsorption temperature-programmed-desorption tests of samples before and after compositing, it was suggested that the decrease in gasification rates of composites prepared from cokes occurred owing to a decrease in the pores and number of active sites on the original cokes.
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•High-strength composites are possible to prepare from low rank coal, low grade coke, and tar.•The increasing strength occurred due to fill of carbonaceous materials derived from tar into pores.•Gasification rate of composite was lowered by 0.2–0.77 times, compared with original samples.•TPD measurements revealed the decrease of active sites for gasification by compositing.•Gasification rate decreased by decreasing pore volume and number of active site.
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