scholarly journals Hydrogen removal in circulating vacuum degasser under conditions of PJSC “NLMK”

2021 ◽  
Vol 64 (8) ◽  
pp. 543-549
Author(s):  
K. N. Pleshivtsev ◽  
O. Yu. Sheshukov ◽  
A. A. Metelkin ◽  
O. I. Shevchenko
Keyword(s):  
High Performance ◽  
Metal Removal ◽  
Converter Shop ◽  
Theoretical Calculations ◽  
Gas Bubbles ◽  
Vacuum Treatment ◽  
Direct Transfer ◽  
Vacuum Degasser ◽  
Neutral Gas ◽  
Surrounding Space

For high­quality steel smelting, stage­by­stage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specifed hydrogen content, the metal in the steel out­of­furnace treatment at Converter Shop No. 2 (CS­2) of PJSC “Novolipetsk Metallurgical Plant” (“NLMK”) is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum derassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufciently studied. To increase efciency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS­2 of PJSC “NLMK”, both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm.). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS­2 of PJSC “NLMK” is removal of hydrogen into the bubbles of carrier gas.

scholarly journals Understanding the biogeochemical mechanisms of metal removal from acid mine drainage with a subsurface limestone bed at the Motokura Mine, Japan

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Shigeshi Fuchida ◽  
Kohei Suzuki ◽  
Tatsuya Kato ◽  
Masakazu Kadokura ◽  
Chiharu Tokoro
Keyword(s):  
Acid Mine Drainage ◽  
Mine Drainage ◽  
Metal Removal ◽  
Theoretical Calculations ◽  
Exchange Capacity ◽  
Treatment Technique ◽  
Manganese Compound ◽  
Edge Structure ◽  
Acid Mine ◽  
Copper Zinc

AbstractSubsurface limestone beds (SLBs) are used as a passive treatment technique to remove toxic metals from acid mine drainage (AMD). In this study, we investigated the mechanisms and thermodynamics of metal (manganese, copper, zinc, cadmium, and lead) precipitation in the SLB installed at the Motokura Mine. Field surveys in 2017 and 2018 showed that the pH of the SLB influent (initially 5–6) increased to approximately 8 in the drain between 24 and 45 m from the inlet. This increase was caused by limestone dissolution and resulted in the precipitation of hydroxides and/or carbonates of copper, zinc, and lead, as expected from theoretical calculations. Manganese and cadmium were removed within a pH range of approximately 7–8, which was lower than the pH at which they normally precipitate as hydroxides (pH 9–10). X-ray absorption near-edge structure analysis of the sediment indicated that δ-MnO2, which has a high cation-exchange capacity, was the predominant tetravalent manganese compound in the SLB rather than trivalent compound (MnOOH). Biological analysis indicates that microorganism activity of the manganese-oxidizing bacteria in the SLB provided an opportunity for δ-MnO2 formation, after which cadmium was removed by surface complexation with MnO2 (≡ MnOH0 + Cd2+  ⇄  ≡ MnOCd+  +  H+). These findings show that biological agents contributed to the precipitation of manganese and cadmium in the SLB, and suggest that their utilization could enhance the removal performance of the SLB.

Magnetically tightened form-stable phase change materials with modular assembly and geometric conformality features

2021 ◽  
Author(s):  
Yongyu Lu ◽  
Dehai Yu ◽  
Haoxuan Dong ◽  
Jinran Lv ◽  
Lichen Wang ◽  
...  
Keyword(s):  
Phase Change ◽  
High Performance ◽  
Magnetic Particles ◽  
Phase Change Materials ◽  
Stable Phase ◽  
Free Standing ◽  
Modular Assembly ◽  
Significant Step ◽  
Dynamic Assembly ◽  
Surrounding Space

Abstract Recently, phase change materials (PCMs) have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, the present PCMs seriously suffer inevitable leakage and low thermal conduction. Magnetism can produce invisible field effects in the surrounding space. If there exist magnetic particles within this region, the effects will act on them emerging various fascinating phenomena. Inspired by this, we introduce hard magnetic particles (which can keep the effect after removing the magnetic field) to PCMs synthesizing an unprecedented magnetically tightened form-stable PCMs (MTPCMs), achieving multifunctions of leakage-proof, dynamic assembly and morphological reconfiguration, superior high thermal (increasing of 1400%~1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength. Novel free-standing temperature control and high-performance thermal and electric conversion systems based on MTPCMs are furthermore developed. This work is a significant step toward exploiting a smart PCM for electronics and low-temperature energy storage.

scholarly journals Search for HI Bubbles Around WR Stars: WR 149

1996 ◽  
Vol 169 ◽  
pp. 619-620
Author(s):  
C. Cappa de Nicolau ◽  
V.S. Niemela ◽  
U. Herbstmeier ◽  
B. Koribalski
Keyword(s):  
Interstellar Medium ◽  
Neutral Hydrogen ◽  
Gas Bubbles ◽  
Stellar Winds ◽  
Hydrogen Distribution ◽  
Neutral Gas ◽  
Rayet Star

The interaction of strong stellar winds with the interstellar medium creates large cavities or interstellar bubbles surrounded by expanding outer shells. 21-cm line (HI) observations have revealed the presence of such neutral gas bubbles around several WR stars (e.g. Niemela & Cappa de Nicolau 1991 and references therein; Dubner et al. 1992).Continuing our search for HI bubbles around WR stars, we have analyzed the neutral hydrogen distribution in the vicinity of the Wolf-Rayet star WR149, a highly reddened WN6-7 star located at 6.5 kpc in the direction (l,b) = (89.°53,+0.°65).

scholarly journals Platinum–copper single atom alloy catalysts with high performance towards glycerol hydrogenolysis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xi Zhang ◽  
Guoqing Cui ◽  
Haisong Feng ◽  
Lifang Chen ◽  
Hui Wang ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Reaction Pathway ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Value Added ◽  
Catalytic Performance ◽  
Single Atom ◽  
Glycerol Hydrogenolysis ◽  
Single Atom Alloy

AbstractSelective hydrogenolysis of biomass-derived glycerol to propanediol is an important reaction to produce high value-added chemicals but remains a big challenge. Herein we report a PtCu single atom alloy (SAA) catalyst with single Pt atom dispersed on Cu nanoclusters, which exhibits dramatically boosted catalytic performance (yield: 98.8%) towards glycerol hydrogenolysis to 1,2-propanediol. Remarkably, the turnover frequency reaches up to 2.6 × 103 molglycerol·molPtCu–SAA−1·h−1, which is to our knowledge the largest value among reported heterogeneous metal catalysts. Both in situ experimental studies and theoretical calculations verify interface sites of PtCu–SAA serve as intrinsic active sites, in which the single Pt atom facilitates the breakage of central C–H bond whilst the terminal C–O bond undergoes dissociation adsorption on adjacent Cu atom. This interfacial synergistic catalysis based on PtCu–SAA changes the reaction pathway with a decreased activation energy, which can be extended to other noble metal alloy systems.

scholarly journals Copper Precipitation Behavior during Continuous Cooling and Subsequent Aging of Powder-Forged Fe-2.5Cu-C Alloy

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1350
Author(s):  
Sui Wang ◽  
Yake Wu ◽  
Tengyu Zhang ◽  
Feng Jiang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
High Performance ◽  
Theoretical Calculations ◽  
Combined Effects ◽  
Precipitation Behavior ◽  
Subsequent Aging ◽  
Continuous Cooling ◽  
Copper Precipitation ◽  
Secondary Precipitates

Microstructure and property evolution of a powder-forged Fe-2.5Cu-C alloy during continuous cooling and subsequent aging were investigated to improve its mechanical properties. During continuous cooling, copper precipitates formed were consistent with the interphase mechanism when the cooling rate was less than 7 °C/s; however, the hardness of the specimen was always higher at faster cooling rates because finer grains and harder phases formed. During subsequent aging, copper precipitates formed and/or coarsened continuously while the hardness of the alloys was greatly influenced by the combined effects of the primary and secondary precipitates, as revealed by the theoretical calculations. In addition, the forming and evolving mechanisms of the copper precipitates at different stages were also discussed based on the experimental results. This study will provide guidance to the industry for achieving high performance in the powder-forged products by treatment manipulation.

Origin of the extra capacity in nitrogen-doped porous carbon nanofibers for high-performance potassium ion batteries

2020 ◽  
Vol 8 (35) ◽  
pp. 18079-18086 ◽  
Author(s):  
Fang Liu ◽  
Jiashen Meng ◽  
Fanjie Xia ◽  
Ziang Liu ◽  
Haoyang Peng ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Porous Carbon ◽  
Experimental Analysis ◽  
High Performance ◽  
Theoretical Calculations ◽  
Potassium Ion ◽  
Nitrogen Doped

The origin of the extra capacity of freestanding and porous N-doped carbon nanofibers was clearly revealed by systematic experimental analysis and theoretical calculations.

scholarly journals Highly Asymmetric Reduction of New Benzofuryl and Benzothiophenyl α-Amino Ketones

Proceedings ◽  
2019 ◽  
Vol 41 (1) ◽  
pp. 49
Author(s):  
Agnieszka Tafelska-Kaczmarek ◽  
Marcin Kwit ◽  
Bartosz Stasiak
Keyword(s):  
High Performance ◽  
Asymmetric Reduction ◽  
Theoretical Calculations ◽  
Transfer Hydrogenation ◽  
Central Position ◽  
Chiral Hplc ◽  
Naturally Occurring ◽  
Approved Drugs ◽  
High Yields ◽  
Derivatives Of

Heterocyclic compounds play an important role in medicinal chemistry and occupy a central position in synthetic organic chemistry. Both benzofuran and benzothiophene are considered as very important structures due to their diverse biological and pharmacological profile. Many clinically approved drugs are synthetic and naturally occurring substituted benzofuryl and benzothiophenyl derivatives in conjunction with other heterocycles. Therefore, a new series of α-amino ketone (containing various azole rings) derivatives of benzofuran and benzothiophene are synthesized and subjected to the transfer hydrogenation with formic acid, catalyzed by RhCl[(R,R)-TsDPEN](C5Me5). The corresponding optically active β-amino alcohols are obtained in high yields and excellent enantioselectivities (93%–99%), as determined by chiral HPLC (high-performance liquid chromatography). The absolute configuration of the products is confirmed by means of ECD (electronic circular dichroism) spectroscopy, supported by theoretical calculations.

scholarly journals Dynamic oxygen adsorption on single-atomic Ruthenium catalyst with high performance for acidic oxygen evolution reaction

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Linlin Cao ◽  
Qiquan Luo ◽  
Jiajia Chen ◽  
Lan Wang ◽  
Yue Lin ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
High Performance ◽  
Theoretical Calculations ◽  
Cost Effective ◽  
Carbon Support ◽  
Oxygen Adsorption ◽  
Single Atom ◽  
Intrinsic Activity ◽  
Acid Media

Abstract Achieving active and stable oxygen evolution reaction (OER) in acid media based on single-atom catalysts is highly promising for cost-effective and sustainable energy supply in proton electrolyte membrane electrolyzers. Here, we report an atomically dispersed Ru1-N4 site anchored on nitrogen-carbon support (Ru-N-C) as an efficient and durable electrocatalyst for acidic OER. The single-atom Ru-N-C catalyst delivers an exceptionally intrinsic activity, reaching a mass activity as high as 3571 A gmetal−1 and turnover frequency of 3348 O2 h−1 with a low overpotential of 267 mV at a current density of 10 mA cm−2. The catalyst shows no evident deactivation or decomposition after 30-hour operation in acidic environment. Operando synchrotron radiation X-ray absorption spectroscopy and infrared spectroscopy identify the dynamic adsorption of single oxygen atom on Ru site under working potentials, and theoretical calculations demonstrate that the O-Ru1-N4 site is responsible for the high OER activity and stability.

scholarly journals Design of high performance p-type sensitizers with pyridinium derivatives as the acceptor by theoretical calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (18) ◽  
pp. 10569-10576
Author(s):  
Zhi-Dan Sun ◽  
Jiang-Shan Zhao ◽  
Karuppasamy Ayyanar ◽  
Xue-Hai Ju ◽  
Qi-Ying Xia
Keyword(s):  
Electron Donor ◽  
High Performance ◽  
Theoretical Calculations ◽  
P Type

Based on triphenylamine as an electron donor and thiophene as a π-linker, Series P and A p-type sensitizers were designed to investigate the effects of the different acceptors on the properties of the sensitizers.

The Pozzolanic Reaction of Silica Fume

2012 ◽  
Vol 1488 ◽  
Author(s):  
Ole M. Jensen
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Cement Hydration ◽  
Theoretical Calculations ◽  
Pozzolanic Reaction ◽  
Interfacial Transition Zone ◽  
Strength Development ◽  
Micro Structure ◽  
Cementitious Binder ◽  
Portland Cement Hydration

ABSTRACTSilica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy of activation of the pozzolanic reaction of silica fume is estimated. The results show that the pozzolanic reaction of silica fume has notable differences from Portland cement hydration.

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