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Diffusion and reaction mechanism of limestone and quartz in fluxed iron ore pellet roasting process

International Journal of Minerals,Metallurgy and Materials 2024年第3期31卷 485-497页

作者： Yufeng Guo Jinlai Zhang Shuai Wang Jianjun Fan Haokun Li Feng Chen Kuo Liu Lingzhi Yang School of Minerals Processing and Bioengineering Central South UniversityChangsha 410083China Technology Center Taiyuan Iron Steel(Group)Co.Ltd.(TISCO)Taiyuan 030003China

The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking *** this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple *** electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting *** results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of *** the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively *** order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 ***_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed ***,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed *** addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.

关键词： fluxed iron ore pellet limestone hematite quartz diffusion reaction

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The Influence of limestone Powder and Metakaolin Co-Blending on the Hydration Process and Mechanical Properties of Q-Phase Cement

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1169-1176页

作者： XIONG Xuan HE Yongjia LÜLinnü MA Jie WANG Fazhou State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan 430070China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics School of ScienceWuhan University of TechnologyWuhan 430070China China Railway Design Corporation Tianjin 300250China

A ternary system comprising Ca_(20)Al_(26)Mg_(3)Si_(3)O_(68)(Q-phase),limestone,and metakaolin is proposed,and its hydration behavior,hydration product phases,microstructure,and mechanical properties are investigated and compared with pure Q-phase *** results indicate that the ternary system exhibits exceptional and sustained compressive strength even under a 40℃environment,significantly outperforming pure *** mechanism lies in that metakaolin effectively inhibits the transformation of metastable ***,the interactions among Q-phase,limestone,and metakaolin further enhance the cementitious *** ternary system effectively addresses potential issues of strength loss in Q-phase cement application,and as a low-carbon cementitious material system,it holds promising potential applications.

关键词： Q-phase limestone metakaolin hydration compressive strength

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Water-induced physicochemical and pore changes in limestone for surrounding rock across pressure aquifers

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Journal of Mountain Science 2024年第9期21卷 3186-3200页

作者： WU Daguo PENG Jianhe XIA Zhenzhao School of Civil and Hydraulic Engineering Hefei University of TechnologyHefei 230009China Anhui and Huaihe River Institute of Hydraulic Research Hefei 230088China School of Civil and Hydraulic Engineering Huazhong University of Science and TechnologyWuhan 430074China

Osmotic water alters the physicochemical properties and internal structures of *** issue is particularly critical in tunnel construction across mountainous regions with aquifers,where pressurized groundwater can destabilize the limestone-based surrounding ***,systematic research into the physicochemical properties and pore structure changes in the limestone under pressurized water is ***,it is essential to develop an interpretable mathematical model to accurately depict how pressurized osmotic water weakens *** this research,a specialized device was designed to simulate the process of osmotic laminar flow within ***,four main tests were conducted:mass loss,acoustic emission(AE),mercury intrusion porosimetry(MIP),and fluorescence *** results gained from tests led to the development of a“Particle-pore throat-water film”*** model explains water-induced physicochemical and pore changes in limestone under osmotic pressure and reveals evolutionary mechanisms as pressure *** on experimental results and model,we found that osmotic pressure not only alters limestone composition but also affects pore throats larger than 0.1μ***,osmotic pressure expands pore throats,enhancing pore structure uniformity,interconnectivity,and *** effects are observed at a threshold of 7.5 MPa,where cohesive forces within the mineral lattice are surpassed,leading to the breakdown of erosion-resistant layer and a significant increase in hydrochemical erosion.

关键词： Water rock reaction Geochemistry Osmotic pressure Pore scale study limestone Pressure aquifer

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Influence of limestone Addition on Combustion and Emission Characteristics of Coal Slime in the 75 t/h CFB Boiler with Post-Combustion Chamber

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Journal of Thermal Science 2023年第5期32卷 1849-1857页

作者： WANG Chao SONG Guoliang YANG Zhao XIAO Yuan YANG Xueting JI Zengcai LYU Qinggang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Science&Technology of ChinaHefei 230026China University of Chinese Academy of Sciences Beijing 100049China Dalian National Laboratory for Clean Energy Dalian 116023China

Coal slime can be disposed in quantity and fully utilized in a well-designed circulating fluidized bed(CFB)boiler,but the nitrogen oxides(NO_(x))and sulphur dioxide(SO_(2))emissions generated in the combustion of coal slime have contributed to serious atmospheric *** Temperature&Post-combustion Technology,a novel and high-efficient way to reduce the NO_(x)emission in the process of combustion,is applied to a 75 t/h CFB boiler burning exclusively coal slime,which will succeed to meet the ultra-low NO_(x)emission *** further explore an appropriate method to reduce the SO_(2)emission under the condition of new technology,the experiments were conducted on a 75 t/h CFB boiler with post-combustion chamber to study the influence of limestone addition on the combustion and emission characteristics of coal *** experimental results showed that High Temperature&Post-combustion Technology combined with the sorbent injection in the furnace is a very promising technology to control the NO_(x)and SO_(2)emissions *** addition can cause the slight decrease in combustion *** addition will lead to the increase in NO_(x)emission in the combustion of coal *** 75 t/h coal slime CFB boiler,the desulfurization efficiency of limestone injection in furnace is close to 98%,achieving the ultra-low SO_(2)*** meet the standard of ultra-low NO_(x)and SO_(2)emission,the two technologies for simultaneous removal of NO_(x)and SO_(2)emissions are economical and feasible currently:Removal of SO_(2)under ultra-low NO_(x)emission and Removal of NO_(x)under ultra-low SO_(2)emission.

关键词： coal slime CFB boiler NO_(x) SO_(2) limestone simultaneous removal

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The formation of orthogonal joint systems and cuboidal blocks:New insights gained from flat-lying limestone beds in the region of Havre-Saint-Pierre(Quebec,Canada)

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3079-3093页

作者： Shaocheng Ji Yvéric Rousseau Denis Marcotte Noah John Phillips Département des Génies Civil Géologique et des MinesÉcole Polytechnique de MontréalMontréalQuébecH3C 3A7Canada Department of Geology Lakehead UniversityThunder BayOntarioP7B 5E1Canada

Vertical orthogonal joints are a common feature in shallow crustal *** are several competing theories for their formation despite the *** examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec,Canada(north shore of Saint-Lawrence River)to test conceptual models of joint formation in a natural *** the region,the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 *** joint-spacing-to-bed-thickness ratios(s/t)are much larger in these beds(s/t=4.3 for systematic joints,and 6.4 for cross-joints)than those in higher strained strata along the south shore of the Saint-Lawrence River(s/t=1),highlighting the effect of tectonic strain in decreasing fracture spacing and block *** high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached(as hypothesized in previous studies).We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic *** presence of ladder-shaped orthogonal joints suggests a state of effective stress withσ_(1)^(∗)≫0>σ_(2)^(∗)>σ_(3)^(∗)and whereσ_(2)^(∗)-σ_(3)^(∗)is within the range of fracture strength variability at the time of *** research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.

关键词： Plato's cuboids Orthogonal joints Fracture spacing limestone Layered rock mechanics Appalachian geology

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Numerical study on maldistribution of gas-solid flow in multiple-branching limestone-conveying pipelines of circulating fluidized bed

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Particuology 2019年第5期17卷 14-21页

作者： Shahong Zhu Man Zhang Juanli Zhang Junfu Lyu Hairui Yang Key Laboratory for Thermal Science and Power Engineering of Ministry Education State Key Laboratory of Power Systems Department of Energy and Power Engineering. Tsinghua University. Beijing 100084 China

As one of the most important auxiliary systems of a circulating fluidized bed boiler,the limestone pneumatic conveying system is of great significance to its *** of powder in the different injecting ports seriously limits inner-furnace desulfurization performance owing to inefficient mixing of limestone powder and *** gas-solid flow characteristics of an industrial-scale multiple-branching limestone-conveying pipeline system of a 200 MW circulating fluidized bed boiler were studied using a computational particle fluid dynamics *** maldistribution intensity was studied under different operating conditions of air velocity and particle mass flow *** results indicated that when the air velocity increased,the maldistribution was mitigated,but when the particle mass flow rate increased,the maldistribution *** solve this problem,two improved schemes were proposed:adding a deflector at different angles and changing the height of pipeline *** to the simulation,the maldistribution could be efficiently mitigated using a distributor height in the range of 100-120 mm and a deflector angle of 10°-30°.

关键词： Circulating fluidized bed limestone Pneumatic conveying Multiple-branching pipeline Maldistribution

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Spatiotemporal evolution of carbon sequestration of limestone weathering in China

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Science China Earth Sciences 2019年第6期62卷 974-991页

作者： Huiwen LI Shijie WANG Xiaoyong BAI Yue CAO Luhua WU State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Puding Comprehensive Karst Research and Experimental Station Institute of Geochemistry Chinese Academy of Sciences and Science and Technology Department of Guizhou Province University of Chinese Academy of Sciences

Carbonate carbon sequestration(CS) can aid in solving the problem of terrestrial residual carbon sinks and imbalances in the global carbon budget. Thus, complete understanding of the magnitude, spatiotemporal distribution, and evolution of this sequestration is highly desirable. On the basis of random forest regression and maximal potential dissolution model for carbonate, we estimated the CS of typical carbonate weathering in China from 2000 to 2014, that is, the sequestration of limestone weathering, using long-term ecologic, meteorological, hydrological raster data, and monitored data from 44 watersheds in China and surrounding regions. We extended our analyses by systematically exploring the spatiotemporal pattern and evolution trend of the flux and total sequestration. High levels of ionic activity coefficients of Ca^(2+) and HCO_3^- in limestone regions were observed to be mainly distributed in Northern and Northwestern China with a clear gradient from northwest to southeast. With a contrary spatial pattern, the annual average CS flux(CSF) of limestone weathering in China was estimated to be 4.28 t C km^(-2) yr^(-1), with high values mainly in the karst zones in Southeastern China. The mean CSF in different latitudes showed that Southern China(south of 28.14°N) was the region with the largest interannual fluctuation of flux and CSF increases as latitude decreases. The mean CSF in subtropical and tropical(TR) regions was the maximum of all major climate types, and for the frigid(F), mid-temperate(MTE), warm temperate(WTE), and temperate(TE) major climates; the CSF in the desert(D)subdivided climate was the minimum of these climates. By contrast, the values in grassland(G) and broad-leaved forest subdivided climate were the maximum. The pixel-based trend analysis indicated that the CSF of limestone weathering in China was slightly increasing in the period 2000–2014 with a rate of 0.036 t C km^(-2) yr^(-1). Furthermore, the annual total CS was estimated to be 7.0

关键词： limestone Chemical weathering carbon sink Spatiotemporal evolution Dissolution Random forest

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Hydration properties and thermal analysis of cement-based materials containing limestone powder

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Journal of Central South University 2017年第12期24卷 2932-2939页

作者： ZHOU Wei LI Liang LIU Shu-hua LIU Xing-hong State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China School of Water Resources and Hydropower Engineering Wuhan University Wuhan 430072 China School of Civil Engineering The University of Queensland Brisbane 4072 Australia School of Civil Engineering and Architecture Wuhan University Wuhan 430072 China

The hydration and thermal properties of cement-based materials containing various proportions of limestone powder as a partial replacement for ordinary Portland cement, were investigated and reported. Both compressive and flexural strengths of cement mortar with various contents of limestone powder were tested to study the influence of limestone powder on the strength development of resulting mixtures. The hydration heat and its rate of evolution were also tested, which clearly showed that the replacement percentage of limestone powder had significant effects on the total hydration heat but only a modest influence on the rate of heat evolution of cement-limestone binder. Importantly, the reduction coefficient of limestone powder on the hydration heat, needed for estimation of adiabatic temperature rise of cement-limestone binder, was found to be approximately 0.51. Fundamental thermal properties of these concrete mixtures containing limestone powder were also studied. Increasing the percentage of limestone powder resulted in a significant reduction in the adiabatic temperature rise but only a slight increase in other thermal properties such as thermal conductivity, thermal diffusivity and specific heat. In addition, thermal analysis using finite-element modelling indicated that inclusion of limestone powder did not significantly affect the rate of temperature rise nor the occurrence time of the highest temperature at early ages.

关键词： limestone powder cement mortar hydration properties thermal properties

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Overburden management in open pits: options and limits in large limestone quarries

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International Journal of Mining Science and Technology 2019年第2期29卷 217-228页

作者： Claudio Oggeri Taddeo Maria Fenoglio Alberto Godio Raffaele Vinai Department of Environment Land and Infrastructure Engineering Politecnico di Torino College of Engineering Mathematics and Physical Sciences University of Exeter

The management of overburden is an important task in open pit exploitations. Site topography and morphology as well as geological and geotechnical properties of natural and remoulded materials are the most important factors affecting the disposal phase. Economic and environmental requirements must be followed in order to achieve the best reclamation results, keeping into account site constraints such as slope stability, hauling and dumping issues, and interactions with groundwater. This paper deals with the above mentioned issues, illustrating a rational approach applied on the case of a large limestone quarry where the thickness of the overburden is relevant and the spoil material has to be dumped in a flooded pit. The proposed multidisciplinary approach led to the selection of most suitable methods for excavation, transportation and disposal. The selection was based on a detailed laboratory and site characterisation that defined favorable and adverse factors to be considered during the preliminary study of a large quarrying project.

关键词： Open pit Overburden Soil testing limestone quarry Muck On-site testing

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Molybdenite-limestone oxidizing roasting followed by calcine leaching with ammonium carbonate solution

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Transactions of Nonferrous Metals Society of China 2017年第7期27卷 1618-1626页

作者： Qiu-sheng ZHOU Wei-tao YUN Jun-tao XI Xiao-bin LI Tian-gui QI Gui-hua LIU Zhi-hong PENG School of Metallurgy and Environment Central South University Changsha 410083 China

Oxidizing roasting of molybdenite with lime can significantly reduce SO2pollution compared with the traditional roastingwithout ***,the calcine is subsequently leached by sulfuric acid,resulting in serious equipment corrosion and abundantnon-recyclable *** this work,a novel process,in which the molybdenite was roasted with CaCO3followed by(NH4)2CO3solution leaching,was proposed to improve the art of lime roasting-sulfuric acid *** roasting of molybdenite withCaCO3was investigated through thermodynamic calculation,thermogravimetric analysis and roasting *** results showthat the products of the oxidizing reaction of MoS2in the presence of CaCO3and O2are CaSO4,CaMoO4and *** MoS2conversion rate achieves approximately99%and the sulfur-retained rate attains approximately95%with aCaCO3-to-MoS2molar ratio of3.6at500°C for1h by adding5%mineralizer A(mass fraction).The leaching results show that theleaching rate of Mo reaches98.2%at85°C for7h with a(NH4)2CO3concentration of600g/L and a liquid-solid ratio of10mL/*** results presented are potential to develop a novel cleaner technique for ammonium molybdate production.

关键词： molybdenite limestone ammonium carbonate oxidizing roasting leaching

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