Control of Oxygen Potential and Its Effect on Dephosphorization of Ferromanganese

The relation of Lp(the ratio P content in slag to P content in ferromanganese) and L_(mn),(the ratio Mn content in slag to Mn content in ferromanganese) with C content[C]in ferromanganese were tested by means of the equilibrium experiments of P and Mn between ferromanganese and BaO-BaF_2-MnO slag system.The results show that there exists in ferromanganese an optimum C content[C]* corresponding to maximum L_P and minimum L_(Mn)> which is closely related to oxygen potential in the system and the activity of P in the alloy.The control limits of oxygen potential in dephosphorization of ferromanganese are then analyzed.The theoretical limits and measures to improve ferromanganese dephosphorization with BaO-based slag are studied comprehensively based on previous research.

Assessment of acoustic backscatter intensity surveying on deep-sea ferromanganese crust: Constraints from Weijia Guyot, western Pacific Ocean

Near-bottom observation data from the manned deep submersible Jiaolong with high-precision underwater positioning data from Weijia Guyot,Magellan Seamounts in the Western Pacific Ocean are reported.Three substrate types were identified:Sediment,ferromanganese crust,and ferromanganese crust with a thin cover of sediment.The ferromanganese crusts show clear zoning and their continuity is usually disturbed by sediments on areas of the mountainside with relatively gentle slope gradients.The identified substrate spatial distributions correspond to acoustic backscatter intensity data,with regions of high intensity always including crust development and regions of low intensity always having sediment.Therefore,acoustic backscatter intensity surveying appears useful in the delineation and evaluation of crust resources,although further more work is needed to develop a practicable methodology.

FABRICATION AND INDUSTRIAL APPLICATION OF FERROMANGANESE COMPOSITE BRIQUETTE

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Geochemical characteristics and geological implication of ferromanganese crust from CM6 Seamount of the Caroline Ridge in the Western Pacific

Ferromanganese crusts(Fe-Mn crusts)grow very slow and can be treated as condensed stratigraphic sections recording paleo-oceanographic environmental information and local key geological events during the mineralization process.Geochronology,textures,mineralogy,and geochemistry of a Fe-Mn crust sample from the CM6 Seamount of the Caroline Ridge in the Western Pacific Ocean were analyzed by means of electron probe microanalysis and X-ray diffraction.The Fe-Mn crust shows three layers in textural characteristics from bottom to top.The lower,middle,and upper layers presence mottled,botryoidal,and columnar textures,respectively.Ferruginous vernadite,Fe hydroxide,amorphous silicate minerals,calcite,quartz,and feldspar are the main minerals of the Fe-Mn crust.Using cobalt chronometry method,the cumulative growth time of the Fe-Mn crust was determined to be 11 Ma or 25 Ma,of which25 Ma is inconsistent with other lines of age constraint brought by dating of the substrate.The co-existence of abundant silicate minerals and bioclasts in the middle and lower layers of the Fe-Mn crust diluted the ferromanganese oxide deposits,thus affected the texture,minerals,and geochemical characteristics of the Fe-Mn crust.Variations in Mn Co,Ni,and other elements content and the burial of opal-A recorded the expansion of oxygen minimum zone(OMZ)in the upper layer of the Fe-Mn crust.In addition,the highreflectivity Fe-rich laminae might indicate the surrounding volcanic activity.The Fe-Mn crust sample was determined to be hydrogenic by electron probe micro-analyzer(EPM A).The findings help us understand the geochemical characteristics of the Fe-Mn crust in the Caroline Ridge Seamount in the Western Pacific and the variations of paleo-oceanographic environment clues borne by the Fe-Mn crusts.

Study on Oxygen Potential of Ferromanganese Melt during Desiliconization

The oxygen potential of ferromanganese melt can be measured by oxygen concentration cell using ZrO2 solid electrolyte stabilized by CaO (Mo-MoO2 as contrast electrode). The converted formula of oxygen potential and electromotive force is as follows: ln pO2=20.03-(69 548.8+46 427.7×E)/T. The temperature of desiliconization is 1 350 ℃. BF ferromanganese was desiliconized by the flux 1 which contents of BaCO3, MnO2 and (Fe2O3+CaF2) are 70 %, 5 % and 25 % respectively. When the treatment time is 15 min, Fe2O3 content is 12 % for obtaining maximum rate of desiliconization. The relation of oxygen potential and activity of carbon is as follows: pO2,m/TPa=35.812-0.106×aC. The relation of oxygen potential and manganese loss is as follows: pO2,m/TPa=6.238+0.679×ΔW［Mn］. When the flux 2 which contents of BaCO3, MnO2, BaF2 and Fe2O3 are 60 %, 15 %, 10 % and 15 % respectively is used to desiliconize ferromanganese, the time corresponding to maximum rate of desiliconizaion and maximum oxygen potential is 15 min. The experimental results show that oxygen potential is controlled by C-O reaction, and that oxygen potential for desiliconization and protecting manganese are 6.238 TPa.

Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major,trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types(siliceous,red clay and their transition zone)in the Central Indian Ocean Basin(CIOB)to address their genetic aspects,classification,growth rate,nature of host sediments and influence of REE in the processes of nodule formation.The nodules from CIOB are mostly either hydrogenetic(metals coming from oxygenated bottom water)and diagenetic(metals coming from suboxic sediment pore water)or a combination of both,depending on the source of supply of metal.However,a number of biogeochemical processes mediate this supply of metals which again changes from time to time,making the nodule growth process highly dynamic.This study suggests that at the initial stage of nodule growth,host sediments do not play much role in controlling the growth processes for which REEs can enter both Mn and Fe oxyhydroxide phases equally.Thus,the bottom water signature is imprinted in these early formed nodules irrespective of their host sediment substrate but with gradual growth and burial in the sediment,the main mode of metal enrichment becomes diagenetic through sediment pore water.This tends to increase the concentration of Mn,Ni and Cu over other elements which are retained in the sediment fraction.Among the REEs,Ce concentration of the nodules shows significant positive anomaly due to variation in redox potential and hence its magnitude can be used to get an idea about the metal enrichment procedure and the genetic type of the nodules.However,based on host sediment only,not much difference is found in the magnitude of Ce anomaly in these nodules.On the other hand,discrimination diagram,based on HFSE and REY chemistry,indicates that most of these nodules are of diagenetic origin under oxic condition with a trend towards hydrogenetic field.Further,the genetic type of the ferromanganese nodules from the CIOB are more effectively differentiated by a combination of their major and trace element concentrations rather than solely based on their REE or HFSE chemistry or host sediment substrate.

Copper and zinc isotope variations in ferromanganese crusts and their isotopic fractionation mechanism

Ferromanganese(Fe-Mn)crusts are potential archives of the Cu and Zn isotope compositions of seawater through time.In this study,the Cu and Zn isotopes of the top surface of 28 Fe-Mn crusts and 2 Fe-Mn nodules were analysed by MC-ICP-MS using combined sample-standard bracketing for mass bias correction.The Zn isotope compositions of the top surface of Fe-Mn crusts are in the range of 0.71‰to 1.08‰,with a mean δ^(66)Zn value of 0.94‰±0.21‰(2 SD,n=28).The δ^(65)Cu values of the top surface of Fe-Mn crusts range from 0.33‰to0.73‰,with a mean value of 0.58‰±0.20‰(2 SD,n=28).The Cu isotope compositions of Fe-Mn crusts are isotopically lighter than that of dissolved Cu in deep seawater(0.58‰vs.0.9‰).In contrast,the δ^(66)Zn values of Fe-Mn crusts appear to be isotopically heavy compared to deep seawater(0.94‰±0.21‰vs.0.51‰±0.14‰).The isotope fractionation between Fe-Mn crusts and seawater is attributed to equilibrium partitioning between the sorption to crusts and the organic-ligand-bound Cu and Zn in seawater.The Cu and Zn isotopes in the top surface of Fe-Mn crusts are not a direct reflection of the Cu and Zn isotopes,but a function of Cu and Zn isotopes in modern seawater.This study proposes that Fe-Mn crusts have the potential to be archives for paleoceanography through Cu and Zn isotope analysis.

Characterization of Egyptian Manganese Ores for Production of High Carbon Ferromanganese

This work aims at studying the reactivity of Egyptian manganese ores to be used in the production of ferromanganese alloys in submerged electric arc furnace. Ores with different manganese content (high-medium and low) were selected and characterized by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The main mineralogical compositions in the three ores are pyrolusite (MnO2) and hematite (Fe2O3). Porosity of selected Mn ores was determined. The reactivity of the different ores was carried out through pre-reduction of the selected ores using thermobalance at 900°C and 1100°C and mixture of CO and CO2 gases. The reduction process was done until steady weight. The reduced ores were examined using XRD and SEM. The results showed that pyrolusite in high and medium ores are converted completely to MnO at 1100°C. However, the ore with low manganese content was converted to MnO and Mn3O4. Consequently, it is clear from the results that Mn ores with high and medium MnO2 content are more reactive than those with low MnO2. Therefore, high MnO2 content Mn ores are preferable to get good economic impact during the production of high carbon ferromanganese.

Parameters Affecting the Production of High Carbon Ferromanganese in Closed Submerged Arc Furnace

This study has been performed to investigate the different parameters affecting on the production of high carbon ferromanganese in closed submerged arc furnace. The analysis of industrial data revealed that using manganese ores with low Mn/Fe ratio necessitates higher amount of Mn-sinter in the charge. Using Mn-blend with higher Mn/Fe ratio reduces the coke consumption and this leads to reducing the electrodes consumption. The recovery of Mn ranges between 70 and 80 %. Much higher basic slag has slight effect on Mn- recovery. However, as slag basicity increases, the MnO- content of slag decreases. The manganese content of produced HCFeMn depends mainly on Mn/Fe ratio of Mn-blend. For obtaining HCFeMn alloy containing minimum 75%Mn, it is necessary to use Mn-blend with Mn/Fe ratio of higher than 6. A model for determination of the amount and composition of off-gases has been derived based on the chemical composition and material balance of the input raw materials and the produced alloy and slag. By using this model, the amount of off-gases was found to increase by increasing both Mn-blend and coke consumption.

The initial exploration for ^(26)Al chronology in deep-sea ferromanganese crust

Background The deep-sea ferromanganese crust(DSFC)is a natural archive for recording the history of the Earth’s evolution,as one of the most common authigenic assemblages in marine sediments.Although the depositional age dating using meteoric ^(10)Be has been successfully used in the study on the chronology of DSFC,the research on ^(26)Al has not seen relevant reports in this aspect due to the influence of factors such as measurement sensitivity and ^(26)Al in situ production.Method The first exploration for ^(26)Al chronology in DSFC was carried out by using accelerator mass spectrometry(AMS)measurements of ^(10)Be and ^(26)Al,and the comparison of relationship between isotopic ratios and concentrations of Al and Be.Results The growth rates of G.R=(1.44±0.09)mm/Ma,(3.58±0.29)mm/Ma,(1.52±0.10)mm/Ma and(2.93±0.14)mm/Ma are derived using ^(10)Be/^(9)Be,^(26)Al/^(27)Al ratios,^(10)Be and ^(26)Al concentrations,respectively.Conclusion The ^(26)Al chronological methods have been explored based on a DSFC sample and encouraging results were obtained.The results are preliminary and insufficient;some information is still needed to explain the difference between ^(26)Al and ^(10)Be chronology.

New index of ferromanganese crusts reflecting oceanic environmental oxidation

Ferromanganese crusts (hereinafter crusts) form in aerobic environment and the environmental oxida-tion degree is recorded by the redox sensitive element Co in the crusts. The ages of the layers from the surface to bottom of the crusts are determined, and main element contents at high resolution along the depth sections of three crusts from the Pacific Ocean are analyzed by an electron microprobe. Thus the variations of Co/(Fe+Mn) and Co/(Ni+Cu) with age/depth of the crust layers are obtained. By comparing the ratios of Co/(Fe+Mn) and Co/(Ni+Cu) with the δ 18O curves of the Pacific benthic foraminifera, we find that these two ratios can reflect the variation of the environmental oxidation state under which the crust layers deposit. The evolution of the oxidation degree reflected by the two indexes resembles the evo-lution of temperature since the Oligocene reflected by the δ 18O curves of the Pacific benthic foraminif-era. This suggests that the crust-forming environment after the Oligocene is controlled mainly by the oxygen-rich bottom water originated from the Antarctic bottom water (AABW). However it is not the case prior to the Oligocene. Furthermore it suggests that the environmental oxidation degree controls the formation of the crusts and the Co contents in the crusts. This explains why the Co contents in the crusts increase with time up to now.

Paleoenvironment evolution of the East Philippine Sea recorded in the new-type ferromanganese crust since the terminal Late Miocene

From systemic research of microstructure, geochemistry, uranium-series and 10Be isotope dating on a new-type deepwater ferromanganese crust from the East Philippine Sea, the paleoenvironment evolu-tion of the target area since the terminal Late Miocene was recovered. The vertical section changes of microstructure and chemical composition are consistent in the studied crust, which indicate three major accretion periods and corresponding paleoenvironment evolution of the crust. The bottom crust zone was formed in the terminal Late Miocene (5.6 Ma) with loose microstructure, high detritus content and high growth rate. Reductions of mineral element content, accretion rate and positive Ce-anomaly degree at 4.6 Ma indicate temporal warming, which went against the crust accretion and finally formed an accretion gap in the terminal Middle Pliocene (2.8―2.7 Ma). The more active Antarctic bottom sea-waters in the Late Pliocene (2.7 Ma) facilitated the fast transfer to the top pure crust zone. Hereafter, with the further apart of volcanic source and the keeping increase of eolian material (1.0 Ma), although surrounding conditions were still favorable, mineral element content still shows an obvious reducing trend. It thereby offers new carrier and data for the unclear paleoceanographic research of the target area since the terminal Late Miocene.

New evidence of microbe origin for ferromanganese nodules from the East Pacific deep sea floor

Using a fluorescence microscope and EPMA, abundant microbe "bodies" and clear mi-crobic fluorescent microstructure are determined in the ferromanganese nodules recently collected from the East Pacific deep sea floor. The microbic fluorescent structure shows a close relation to the formation of the ferromanganese nodules. According to their morphological features, the microbes are classified into two types: one is named clumpy microbe, which takes a bar-shaped manganese mineral as a pillar and grows like fasciculate coral, resulting in irregular cauliflorate nodules with rough surfaces; the other is called filamentous microbe, which grows in very thin arcuate and/or concentric circular laminae composed of a microbe layer and a metal (manganese and iron)-rich layer, leading to potato-shaped nodules with relatively smooth surfaces. It also can be seen that the two types of microbes are intergrown together, resulting in nodules complicated in compositions and shapes.

Oxide Inclusions in Ferromanganese and Its Influence on the Quality of Clean Steels

Low and medium carbon ferromanganese produced by oxygen decarburization process and electric silicothermic process was briefly introduced, and the quality of products by these two processes was analyzed. Results showed that the total oxygen content in medium carbon ferromanganese by electric silicothermic process in China, which ranged from 0.039% to 0.171%, was between those of the common and refined products by oxygen decarburization process outside of China. The increments of total oxygen content in liquid steel were estimated when ferromanganese was added for the purpose of Mn element adjustment at the end of smelting. Refined low and medium carbon ferromanganese, which had low total oxygen content, was recommended for composition adjustment of clean steels during final stage of a heat. It is possible that the inclusions in the ferromanganese alloy greatly influenced the quality of clean steel indirectly by affecting the amount, size and composition of inclusions in steel.

The relationship between the growth process of the ferromanganese crusts in the Pacific seamount and Cenozoic ocean evolvement

Base on the Os isotope stratigraphy together with the empirical growth rate models using Co concentrations, the growth ages of the ferromanganese crusts MHD79 and MP3D10 distributed in the seamount of Pacific are confirmed. Through the contrast and research on the previous achievements including ODP Leg 144 and the crusts CD29-2, N5E-06 and N1-15 of the seamount of the Central Pacific, the uniform five growth and growth hiatus periods of them are found, and closely related to the Cenozoic ocean evolvement process. In the Paleocene Carbon Isotope Maximum (PCIM), the rise of the global ocean productivity promoted the growth of the seamount crust; the first growth hiatus (I) of the ferromanganese crust finished. In the Paleocene-Eocene Thermal Maximum (PETM), though the vertical exchange of seawater was weakened, the strong terrestrial chemical weathering led to the input of a great amount of the terrigenous nutrients, which made the bioproductivity rise, so there were no crust hiatuses. During 52-50 Ma, the Early Eocene Optimum Climate (EECO), the two poles were warm, the latitudinal temperature gradient was small, the wind-driven sea circulation and upwelling activity were weak, the terrestrial weathering was also weakened, the open ocean bioproductivity decreased, and the ferromanganese crust had growth hiatus again (II). From early Middle Eocene-Late Eocene, Oligocene, it was a long-term gradually cooling process, the strengthening of the sea circulation and upwelling led to a rise of bioproductivity, and increase of the content of the hydrogenous element Fe, Mn and Co and the biogenous element Cu, Zn, so that was the most favorable stage for the growth of ferromanganese crust (growth periods III and IV) in the studied area. The hiatus III corresponded with the Eocene-Oligocene boundary, is inferred to relate with the global climate transformation, celestial body impact event in the Eocene-Oligocene transition. From the early to the middle Miocene, a large-scale growth hiatus (hiatus period IV) of the ferromanganese crust in the studied area is inferred to relate with temporary warm up climate and ephemeral withdrawal of Antarctic bottom water in the early Miocene. After that, the Antarctic ice sheets extended, the bottom water circumfluence strengthened, the ocean fertility increased, and the once interrupted crust continued to grow in the late Miocene (growth period V).

MAIN FACTORS STUDY OF THE CONTROLLING GEOCHEMICAL CHARACTERISTICS OF FERROMANGANESE NODULES (Ⅰ)——GEOCHEMICAL CHARACTERISTICS OF FERROMANGANESE NODULES

The geochemical characteristics of ferromanganese nodules have been described in detail by the information study of major elements, trace elements, rare earth elements and infrared spectrophotometer, X-ray diffraction, electronic probing, electronic microscope analysis in 57 ferromanganese nodules of different types from the South China Sea and the Northern Central Pacific Basin. The result shows that (ⅰ) the different types of ferromanganese nodules have different geochemical characteristics; (ⅱ) there is a close relationship between Mn/Fe in ferromanganese nodules and their element content, mineral composition, nodule abundance, tenor (Cu+Co+Ni)%, growth Speed and sedimentary environment. It has suggested that Mn/Fe in nodules can be an indicator of classifying ferromanganese nodule types.

CONCENTRATION, SOURCE OF MANGANESE AND IRON IN FERROMANGANESE NODULES AND THE RELATIONSHIP BETWEEN NODULES AND SEDIMENTARY ENVIRONMENTS IN NORTH PACIFIC REGION

The concentration, source of manganese and iron in ferromanganese nodules and therelation between nodules and sedimentary environments are discussed in detail by asynthetical study on chemical information of ferromanganese nodules and correspondingsediment, pore water and geological, biological （bacteria） information in 26 stations fromthe North Pacific region （7- 13°N, 178- 165°W）. The result shows that （i） the concen-tration and distribution characteristics of magnese and iron in ferromanganese nod-ules differ in different types of nodules, however, the concentration decreases with theincrease in grain sizes of nodules; （ii） the source of iron in different types of nodulesis basically the same, i. e. the slow sedimentation of overlying water; （iii） manganesein nodules comes mainly from the diffusion of Mn2+ in the pore water, and Mn2+ fromthe reduction of Mn4+ in sediments by the medium of bacteria. As the distribution of bac-teria is believed to be strongly affected by the sedimentary

STUDY ON MAIN FACTORS OF THE CONTROLLING GEOCHEMICAL CHARACTERISTICS OF FERROMANGANESE NODULES (Ⅱ)——FORMATIVE MECHANISM OF DIFFERENT GEOCHEMICAL TYPE NODULES

Based on the study of geochemical characteristics of the different Mn/Fe ferromanganese nodules, the formative mechanism of different geochemical type ferromanganese nodules are discussed in detail by analysing the relationship between different Mn/Fe nodules and their sediments (rock), pore water, overlying water, biological (bacteria) information from the rare earth element geochemistry, sedimentary geochemistry and biogeochemistry. The result shows that the formation mechanism of different Mn/Fe nodules is obviously different, and according to the formative mechanism, the ferromanganese nodules of the South China Sea and the Northern Central Pacific can be classified principally into three geochemical types: volcanic sedimentary mechanism (Mn/Fe≤1.50), oxidation diagenetic mechanism (Mn/Fe】1.50≤2.50) and suboxic organic diagenetic mechanism (Mn/Fe】2.50).

Effect of ferromanganese additions on non-metallic inclusion characteristics in TRIP steel

The inclusion characteristics in extra low-carbon ferromanganese(ELC-FeMn),low-carbon ferromanganese(LC-FeMn),mid-carbon ferromanganese(MC-FeMn),and high-carbon ferromanganese(HC-FeMn)were evaluated by scanning electron microscopy coupled with energy dispersive spectroscopy.The effect of FeMn alloys on the cleanliness of transformation-induced plasticity(TRIP)steel was studied based on laboratory-scale experiments and thermodynamic calculations.The results show that the main inclusions in ELC-FeMn are MnO-MnS and MnS,and the dominant inclusions in LC-FeMn and MC-FeMn are MnO,MnO-SiO_(2),and MnO-SiO_(2)-MnS.The inclusions in HC-FeMn are diversified.Besides MnO-SiO_(2)inclusion,a certain number of Al-,Si-,and Ti-containing inclusions and enrichment phases of Pb,Sn,and P are observed in HC-FeMn.Before FeMn alloy addition,the main inclusion in steel is Al2O.After alloying with the four different grades of FeMn alloy,the main inclusions in TRIP steel are Al_(2)O_(3),AIN,MnS,AlO3-AIN,AINMnS,and Al_(2)O_(3)-MnS.The MnO and SiO_(2)inclusions from FeMn alloys are not detected in TRIP steel.