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Shougang Duan,Yufeng Yang,Yong Dong,Yu Wang,Beibei Jiang,Chuanqiang Li,Zhengrong Zhang 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.6
Ultra-fine grain AlCrFe2Ni2Wx(x = 0.1, 0.2, 0.3, 0.4) alloys were designed and prepared by vacuum arc melting, and correspondingmicrostructural evolution and mechanical properties were investigated. All of the alloys show a mixed structurewith FCC + BCC (B2) + TCP phases. The addition of W element has a significant effect on the formation mechanism of themorphology, which promotes the transition from FCC phase to μ phase and inhibits the spinodal decomposition of BCCphase. With the increase of W content, more μ phase precipitates from the FCC phase and grain boundaries. After the dissolutionof W element into matrix, the formed oversaturated solid solution and precipitated μ phase have the effect of solidsolution strengthening and second phase strengthening, respectively. The yield strength and Vickers hardness increasesfrom 765 to 1319.6 MPa and HV 332.2 to HV 461.8, respectively. The addition of W element enhances the strength of thealloys but reduced ductility. The AlCrFe2Ni2W0.1alloy exhibits outstanding comprehensive mechanical properties, with itsfracture strength reaching 2726.5 MPa and a considerable compressive strain of 43.3%, which implies promising potentialengineering application.
Adsorption equilibrium, kinetics and mechanism studies of mercury on coal-fired fly ash
Qiang Zhou,Yufeng Duan,Chun Zhu,Jun Zhang,Min She,Hongqi Wei,Yaguang Hong 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.7
Fly ash samples were collected from the electrostatic precipitator (ESP) of a 600MW pulverized coal boiler firing Zhungeer bituminous coal in China to evaluate and explore its mercury adsorption capacity and mechanism. Samples characterization was conducted to feature their morphologies correlated to mercury content, and experimental studies on mercury adsorption in a fixed-bed apparatus were carried out to further verify its mercury adsorption availability. Based on the experimental data, adsorption isotherm was modeled with Langmuir, Freundlich, and Temkin equations. Adsorption kinetic analysis was also performed. The results show that mercury content of fly ash samples is associated with particle size, unburned carbon content and functional groups of Al-O/Si-O or Si-O-Si/Si-O-Al tetrahedron on fly ash. Increase of initial mercury concentration is beneficial to promote mercury adsorption due to the enhancement of mercury diffusion force onto the fly ash surface, mercury intraparticle diffusion rate and initial mercury adsorption rate. Fly ash with medium size displays better mercury adsorption capacity. Smaller particle size results in higher specific surface area, but brings about low specific surface area utilization rate for mercury adsorption. Freundlich isotherm equation presents better fitting result, indicating that fly ash surface is non-uniform. Mercury adsorption on fly ash at 120 oC is mainly physisorption enhanced by chemisorption with ΔG at −36.73 kJ/mol. The pseudo-first-order kinetic model can describe the adsorption process more accurately and predict mercury adsorption capacity of fly ash preferably, showing that mercury adsorption on fly ash surface in fixed-bed is controlled dominantly by external mass transfer.
Local resistance characteristics of highly concentrated coal-water slurry flow through fittings
Meng Liu,Liangyong Chen,Yufeng Duan 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2
The local resistance characteristics of high concentration coal-water slurry (CWS) flowing through three types of local fittings, namely the gradual contractions, sudden contractions and 90o horizontal elbows, were investigated at a transportation test facility. Results show that the local resistance loss of gradual contractions decreases as the contraction angle increases. When pipe diameter ratio varies little, local resistance loss of sudden contractions changes insignificantly. There is an optimal value of bend diameter ratio, at which the local resistance loss of horizontal elbows is the least. As Reynolds number increases, the resistance coefficients of all the three fittings first reduce and then stabilize, while the three pipes have different ratio of equivalent length to pipe diameter Le/D behaviors, that is, Le/D of the gradual contractions decreases gradually and then keeps stable; that of the sudden contractions diminishes at first and then increases, and that of the horizontal elbows increases linearly.
CFD simulation of coal-water slurry flowing in horizontal pipelines
Liangyong Chen,Wenhao Pu,Changsui Zhao,Yufeng Duan 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.4
An Eulerian multiphase approach based on kinetic theory of granular flow was used to simulate flow of coal-water slurries (CWS) in horizontal pipelines. The RNG k-ε turbulent model was incorporated in the governing equation to model turbulent two-phase flow with strong particle-particle interactions. In this model, the coal particles with bimodal distribution were considered as two solid-phase components, and the moment exchange between solid and liquid as well as that between solid and solid were accounted for. The model was firstly validated with pressure gradient and concentration profile data from the open literature, and then validated with pressure gradient data of the authors’ experiments. The effects of influx velocity, total influx concentration and grain composition were numerically investigated, and the results have displayed some important slurry flow characteristics, such as constituent particle concentration distribution and velocity distribution as well as pressure gradients, which are very difficult to display in the experiments. The results suggest that both gravity difference between large and small particles and strong particleparticle interaction had significant effects on concentration distribution as well as velocity distribution.