Mechanisms and kinetics of zinc and iron separation enhanced by calcified carbothermal reduction for electric arc furnace dust

Jiayong Qiu,Shui Yu,Jiugang Shao,Kaiqi Zhu,Dianchun Ju,Chunyu Chen,Dexing Qi,Fei Wang,Ni Bai,Rui Mao,Xiaoming Wang 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.4

A high basicity charge prepared with electric arc furnace dust (EAFD), carbonaceous reducing agent and CaO is proposed. The mechanisms of enhancing separation of zinc and iron by calcified carbothermic reduction of the high basicity charge were analyzed by combining thermal analysis kinetics and experiment. The influences of roasting temperature, carbon ratio (nc/no, molar ratio of carbon in graphitic carbon powder to oxygen in EAFD), and CaO dosage on phase transition and dezincification ratio in EAFD were investigated. The results show that the intermediates Ca2Fe2O5 and Fe0.85−xZnxO can be produced from the zinc-iron separation of zinc ferrate during the process of calcified carbothermic reduction of EAFD. Addition of CaO and C results in the following transition pathways: ZnFe2O4+ CaO→Ca2Fe2O5+ZnO→Ca2Fe2O5+Zn(g)→CaO+Fe; Fe0.85−xZnxO+CaO→Ca2Fe2O5+FeO+ZnO→CaO+Fe+Zn(g). In the range of nc/no of 0.4–1.2 and roasting temperature of 1,000–1,100 °C, the addition of CaO can promote reduction and dezincification. Based on the Kissinger-Akahira-Sunose (KAS) and Coats-Redfern methods, the kinetic results show that the calcified carbothermic reduction process can be divided into three stages: initial stage (α=0–0.3), middle stage (α=0.3–0.45), and final stage (α=0.45–1.0). The average activation energy of the initial stage is 305.01 kJ·mol−1, and the reaction mechanism is one-dimensional diffusion. The average activation energy is 315.67 kJ·mol−1 for the middle stage and 288.22 kJ·mol−1 for the final stage. The chemical reaction equation is found to be the most suitable mechanism in the medium and final stages. It is also found that the addition of CaO can reduce the average activation energy by about 32 kJ·mol−1 and shorten the intermediate stage of the reaction.

Combining Non-Contrast CT Signs With Onset-to-Imaging Time to Predict the Evolution of Intracerebral Hemorrhage

Song Lei,Qiu Xiaoming,Zhang Cun,Zhou Hang,Guo Wenmin,Ye Yu,Wang Rujia,Xiong Hui,Zhang Ji,Tang Dongfang,Zou Liwei,Wang Longsheng,Yu Yongqiang,Guo Tingting 대한영상의학회 2024 Korean Journal of Radiology Vol.25 No.2

Objective: This study aimed to determine the predictive performance of non-contrast CT (NCCT) signs for hemorrhagic growth after intracerebral hemorrhage (ICH) when stratified by onset-to-imaging time (OIT). Materials and Methods: 1488 supratentorial ICH within 6 h of onset were consecutively recruited from six centers between January 2018 and August 2022. NCCT signs were classified according to density (hypodensities, swirl sign, black hole sign, blend sign, fluid level, and heterogeneous density) and shape (island sign, satellite sign, and irregular shape) features. Multivariable logistic regression was used to evaluate the association between NCCT signs and three types of hemorrhagic growth: hematoma expansion (HE), intraventricular hemorrhage growth (IVHG), and revised HE (RHE). The performance of the NCCT signs was evaluated using the positive predictive value (PPV) stratified by OIT. Results: Multivariable analysis showed that hypodensities were an independent predictor of HE (adjusted odds ratio [95% confidence interval] of 7.99 [4.87–13.40]), IVHG (3.64 [2.15–6.24]), and RHE (7.90 [4.93–12.90]). Similarly, OIT (for a 1-h increase) was an independent inverse predictor of HE (0.59 [0.52–0.66]), IVHG (0.72 [0.64–0.81]), and RHE (0.61 [0.54– 0.67]). Blend and island signs were independently associated with HE and RHE (10.60 [7.36–15.30] and 10.10 [7.10–14.60], respectively, for the blend sign and 2.75 [1.64–4.67] and 2.62 [1.60–4.30], respectively, for the island sign). Hypodensities demonstrated low PPVs of 0.41 (110/269) or lower for IVHG when stratified by OIT. When OIT was ≤ 2 h, the PPVs of hypodensities, blend sign, and island sign for RHE were 0.80 (215/269), 0.90 (142/157), and 0.83 (103/124), respectively. Conclusion: Hypodensities, blend sign, and island sign were the best NCCT predictors of RHE when OIT was ≤ 2 h. NCCT signs may assist in earlier recognition of the risk of hemorrhagic growth and guide early intervention to prevent neurological deterioration resulting from hemorrhagic growth.

Preliminary numerical study of single bubble dynamics in swirl flow using volume of fluid method

Li, Zhongchun,Qiu, Zhifang,Du, Sijia,Ding, Shuhua,Bao, Hui,Song, Xiaoming,Deng, Jian Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.4

Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather of spacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flow not only changed the bubble generation in the near wall field, but also affected the bubble behaviors in the center region of the subchannel. The interaction between bubble and the swirl flow was one of the basic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding on the bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in the present paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface was captured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at different pressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtained based on the bubble parameters captured by VOF. The simulation cases in the present study included single bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble moved toward the center with high velocity when the swirl magnitude was high. The largest bubble had the highest lateral migration velocity in the present study range. The effect of pressure was small when bubble size was the same. The prelimenery simulation result would be beneficial for better understanding complex two phase flow phenomena in fuel assembly with spacer grid.

Modeling and Analysis of an Avionic Battery Discharge Regulator

Qian Chen,Haihong Yu,Xiaoming Huang,Yi Lu,Peng Qiu,Kai Tong,Jiazhuo Xuan,Feng Xu,Xiaohua Xuan,Weibo Huang,Yajing Zhang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

The avionic battery discharge regulator (BDR) plays an important role in a power-conditioning unit. With its merits of high efficiency, stable transfer function, and continuous input and output currents, the non-isolated Weinberg converter (NIWC) is suitable for avionic BDR. An improved peak current control strategy is proposed to achieve high current-sharing accuracy. Current and voltage regulators are designed based on a small signal model of a three-module NIWC system. The system with the designed regulators operates stably under any condition and achieves excellent transient response and current-sharing accuracy.

Domain Decomposition Strategy for Pin-Wise Full-Core Monte Carlo Depletion Calculation with the Reactor Monte Carlo Code

Jingang Liang,Kan Wang,Yishu Qiu,Xiaoming Chai,Shenglong Qiang 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.3

Because of prohibitive data storage requirements in large-scale simulations, the memoryproblem is an obstacle for Monte Carlo (MC) codes in accomplishing pin-wise threedimensional(3D) full-core calculations, particularly for whole-core depletion analyses. Various kinds of data are evaluated and quantificational total memory requirements areanalyzed based on the Reactor Monte Carlo (RMC) code, showing that tally data, materialdata, and isotope densities in depletion are three major parts of memory storage. Thedomain decomposition method is investigated as a means of saving memory, by dividingspatial geometry into domains that are simulated separately by parallel processors. For thevalidity of particle tracking during transport simulations, particles need to be communicatedbetween domains. In consideration of efficiency, an asynchronous particle communicationalgorithm is designed and implemented. Furthermore, we couple the domain decompositionmethod with MC burnup process, under a strategy of utilizing consistent domain partition inboth transport and depletion modules. A numerical test of 3D full-core burnup calculationsis carried out, indicating that the RMC code, with the domain decomposition method, iscapable of pin-wise full-core burnup calculations with millions of depletion regions.

Modeling and Analysis of an Avionic Battery Discharge Regulator

Chen, Qian,Yu, Haihong,Huang, Xiaoming,Lu, Yi,Qiu, Peng,Tong, Kai,Xuan, Jiazhuo,Xu, Feng,Xuan, Xiaohua,Huang, Weibo,Zhang, Yajing The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

The avionic battery discharge regulator (BDR) plays an important role in a power-conditioning unit. With its merits of high efficiency, stable transfer function, and continuous input and output currents, the non-isolated Weinberg converter (NIWC) is suitable for avionic BDR. An improved peak current control strategy is proposed to achieve high current-sharing accuracy. Current and voltage regulators are designed based on a small signal model of a three-module NIWC system. The system with the designed regulators operates stably under any condition and achieves excellent transient response and current-sharing accuracy.

Preparation of Carbon Nanotubes/Polyurethane Hybrids as a Synergistic Absorbent for Efficient Oil/Water Separation

Tao Zhang,Bin Gu,Fengxian Qiu,Xiaoming Peng,Xuejie Yue,Dongya Yang 한국섬유공학회 2018 Fibers and polymers Vol.19 No.10

Polyurethane (PU) hybrid materials have attracted a great deal of attention as oil-absorbents in oil/water separation because they combine the surface properties of nanomaterials and the excellent absorption properties of PU. Herein, we report a facile two-step process to synthesize the oil-absorbing hybrid materials by integrating carbon nanotubes (CNTs) into porous PU foam architectures. First, the multi-walled carbon nanotubes (MWCNTs) were modified by oxidation in binary H2SO4-HNO3 mixed acid, followed by grafting the silane coupling agent (KH 570) on the on surfaces of MWCNTs. Then, the MWCNTs/PU hybrid materials were synthesized using isocyanate and polyether polyol as monomers for polymerization and surface modified MWCNTs as inorganic components. The physical and chemical properties of hybrid materials were validated by XRD, TEM, SEM, N2 sorption and contact angle analysis. The surface grafted MWCNTs possess superhydrophobic properties with the maximum water contact angle of 153 o. The SEM results indicate that the WCNTs/PU hybrid materials consisted of spherical structures with microscale holes, which can separate oils from oil/water mixtures with high absorption properties and high selectivity. Effects of the various MWCNTs contents on the oil absorption behavior of the WCNTs/PU hybrid materials were investigated. The results show that the modified MWCNTs significantly improves the oil absorption properties with the optimal MWCNTs content of 3 %. By combining the structural features of WCNTs and PU foams, the hybrid materials not only exhibit excellent absorption properties for various types of oils and organic solvents, but also show excellent oil recoverability and absorbent regenerability. The as-synthesized WCNTs/PU hybrid have significant potential as oil absorbents for efficient separation of oils and organic solvents from water.

Layered double hydroxide functionalized biomass carbon fiber for highly efficient and recyclable fluoride adsorption

Tao Zhang,Bencheng Zhao,Qiuyun Chen,Xiaoming Peng,Dongya Yang,Fengxian Qiu 한국응용생명화학회 2019 Applied Biological Chemistry (Appl Biol Chem) Vol.62 No.-

The removing of fluoride from water is highly desired from the viewpoint of environmental protection and sustainable development due to the adverse impacts on human and ecosystem. In this study, the hierarchical porous layered double hydroxide (LDH)/biomass carbon fiber (BCF) has been successfully fabricated by the combined sol–gel, carbonization and hydrothermal processes using sustainable bamboo fibers as raw material based on the assembly the LDH nanosheets on BCF surfaces. Structural characterization indicates that the LDH nanosheets were attached to the BCF surface via in situ crystal growth. N2 sorption measurements show that the LDH/BCF has relatively uniform accessible mesochannel size of 3.56 nm, and the surface area is as high as 39.89 m2/g. The resulting LDH/BCF exhibit a noticeable enhanced adsorption capacity for fluoride removal compared to that of Al2O3/ BCF, accompanied by 15.21 mg/g of the adsorption capacity. The presence of the high negative charge anions had negligible influence on fluoride adsorption. Importantly, recovery adsorption capacity for fluoride was obtained for LDH/BCF for 5 consecutive cycles without a significant decrease in its adsorption properties. Therefore, the current research can offer a green approach to fabricate LDH/BCF with hierarchical structures for efficient removing fluoride from water, and the fabricated LDH/BCF will be an excellent candidate for pollution control based on the synergistic effects of BCF and LDH, high adsorption properties with good reusability.