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Tong L.-G.,University of Science and Technology Beijing | Tong L.-G.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Li L.,University of Science and Technology Beijing | Gu J.-C.,University of Science and Technology Beijing | And 5 more authors.
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2015

The weld pool shape is one of important factors related to the welding process and quality, which not only determines the shape of weld seam, but also has an important influence on microstructure, mechanical properties and quality of weld seam. In order to research the properties of the melting time and depth of fusion at filling bead affected by the next layer under different heat inputs, the two dimensional multi-layer welding process with composite welding groove of X80 pipeline steel used by the birth-and-death elements method of the finite element software ANSYS was build. When the heat input of filling bead increased from 13.25 kJ/cm to 14.57 kJ/cm, the increase percentage of melting time was half of that from 12.04 kJ/cm to 13.25 kJ/cm. Meanwhile the increment of each layer's depth of fusion was constant, which remained as 0.45 mm. © 2015, Science Press. All right reserved.


Xia D.,University of Science and Technology Beijing | Xia D.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Wu H.,University of Science and Technology Beijing | Lei X.,Beijing Pureenergy Technology Development Co.
Fuel | Year: 2014

A sequential cycle of coal gas production with high heating value was developed consisting of reduction and oxidation reactions. Steam and air are used as gasification agents in the reduction zone while the reaction between char and air in the oxidation zone is exothermic and provides heat for the reduction zone. Coal ash and unburned char are circulated between the two zones and heated in the oxidation zone. The reduction zone and the oxidation zone form a circulation system, and high heating value coal gas can be produced in it continuously. The feasibility of the proposed cycle was verified by preliminary experiments; and a system model was built with Aspen Plus software, in order to evaluate the operation conditions, to get accurate parameters for the cycle and provide a design basis for a serial production of large equipment. The simulation results show the effect of air-to-coal ratio in the reduction zone (Ra-red) and steam-to-coal ratio (Rs) over some parameters, like lower heating value (LHV), production rate (ṁ) and compositions of coal gas. In addition, pilot experiments were carried out based on the model; coal gas LHV was established between 8.40 and 9.24 MJ/N m 3. The simulation results were according with the experimental data under the same operation conditions in 3 different cases. As a result, coal gas LHV was increased by more than 87.50%, comparing the experiment with the typical Winkler fluidized bed gasifier, which uses air and steam as gasification agents as well. © 2014 Elsevier Ltd. All rights reserved.


Xie Z.-Y.,University of Science and Technology Beijing | Feng J.-X.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry
Journal of Central South University | Year: 2013

The behavior of the active layer of material bed within rotary kilns plays a key role in industrial applications. To obtain its influences on industrial process, different regimes of particle motion have been simulated by discrete element method (DEM) in three dimensions under variant rotation speeds, filling degree, based on the background of induration process of iron ore pellets. The influences of the mentioned factors on the maximum thickness of the active layer and the average velocity of particles have been investigated. The average velocity of particles increases with Froude number following the power function over a wide range, and the maximum thickness rises with increasing rotation speed in a way of logarithm. The influence of the filling degree f on the maximum thickness exhibits a good linearity under two classic regimes, but the increasing of the average velocity of the active layer is limited at f=0.4. This basic research highlights the impact of the active layer within rotary kilns, and lays a good foundation for the further investigation in mixing and heat transfer within the particle bed inside rotary kilns. © 2013 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhang H.,University of Science and Technology Beijing | Zhang H.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Liu Y.-S.,University of Science and Technology Beijing | Hao Z.-T.,University of Science and Technology Beijing | And 2 more authors.
Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering | Year: 2015

Two-film gas transfer theory was applied to analyze carbon dioxide absorption across the gas-liquid interface with diethanolamine (DEA) solution. Mathematical models were developed to describe the dependence of CO2 transfer rate on pH value and the degree of rate enhancement due to chemical reactions with DEA. Various concentrations of carbonic species in the bulk liquid [i.e., ΔCΔt(RNHCOO-), ΔCΔt(HCO3 -) and ΔCΔt(CO3 2-)] in time were considered to affect total mass transfer rate. Various technological parameters, such as DEA concentration, CO2 flow rate and ratio of absorption blends were controlled. The results show that CO2 transfer rate is mainly contributed by CO3 2- and HCO3 -, but the transfer rate of RNHCOO- is not significant. The CO2 transfer rate is promoted by the increase of DEA concentration, but the effect will decrease after pH value falls to 8.2. When CO2 flow rate increases, the transfer rate will increase until 70 mL/min. Blend solution is better than single DEA solution in CO2 absorption, but the effect of the ratio of blend is not significant on contribution ratio of carbonic species to total mass transfer rate. ©, 2015, Science Press. All right reserved.


Dou R.,University of Science and Technology Beijing | Wen Z.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Zhou G.,China ENFI Engineering Corporation
Applied Thermal Engineering | Year: 2016

A 2D axisymmetric inverse heat-conduction model based on the Levenber-Marquardt method was built. The equivalent Nusselt number Nuequ of air jet impinging on a stainless steel plate with finite thickness were obtained. Radiant heat transfer is significant when the temperature of the target plate is high, which induces the nonlinear feature of the inverse heat-conduction problem. The results of the experiments and the inverse analysis provide the following findings. First, the inverse heat-conduction model is accurate. Second, Nuequ maintains a relatively small value before the onset of the air jet. After the air jet starts, however, the values of Nuequ within the stagnation zone (dimensionless radius R/Dn≤&1.0) increase dramatically, reach the peak points in the next 20s, and then remain nearly constant until the end of the experiments. Third, the radial distribution of Nu;bsubesub shows that it decreases rapidly within the region of R/D;bsubesub≤;8.0. When R/Dn exceeds 10, Nuequ appears unaffected by the Reynolds number and R/Dn. Lastly, Nuequ decreases slowly with the increase in time, which indicates that radiant heat-transfer flux decreases with target plate temperature. © 2015 Elsevier Ltd. All rights reserved.


Cao H.,University of Science and Technology Beijing | Liu X.-L.,University of Science and Technology Beijing | Liu X.-L.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Wen Z.,University of Science and Technology Beijing | And 3 more authors.
Gongcheng Kexue Xuebao/Chinese Journal of Engineering | Year: 2015

The reduction kinetics of sintering ore used as an oxygen carrier in the chemical looping combustion was experimentally investigated by thermogravimetry. The redox reactivity of sintering ore was compared with that of self-made Fe2O3/Al2O3 oxygen carriers prepared by the dissolution method. Experiments were conducted on the reduction of sintering ore by diluted hydrogen during the temperature range of 500 to 1250 ℃, and 30 cycles of redox reaction experiments were performed at 950 ℃. Experimental data was analyzed by four kinetic models. It is found that sintering ore can be used as an oxygen carrier with a reduction conversion larger than 80%, complete oxidization, and a good performance of recyclability. The reduction reaction rate and final fractional conversion of sintering ore both increase with rising temperature from 500 ℃ to 950 ℃, while both have a trend of decline when the temperature is above 1100 ℃. The second order reaction model (M2) can properly fit the experimental data of the reduction of sintering ore in the first reaction stage (Fe2O3-Fe3O4/FeO, reduction conversion X<25%) during the temperature range of 500 to 950 ℃, achieving the apparent activation energy E=36.018 kJ·mol-1 and the pre-exponential factor A0=1.053×10-2 s-1, whereas the shrinking core model (M4) fits well in the second reaction stage (Fe3O4/FeO-Fe, reduction conversion X>25%), achieving the apparent activation energy E=51.176 kJ·mol-1 and the pre-exponential factor A0=1.066×10-2 s-1. ©, 2015 All right reserved.


Zhang X.,University of Science and Technology Beijing | Wen Z.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Dou R.,University of Science and Technology Beijing | Zhou G.,University of Science and Technology Beijing | Zhang F.,University of Science and Technology Beijing
Applied Thermal Engineering | Year: 2014

An experimental study of heat transfer between a hot metallic surface and water droplets sprayed by a commercial flat pattern air-atomized spray nozzle was conducted. A lattice grid was used to measure the local spray density (Q) along the horizontal (X) and vertical (Y) axes of the local spray region. By measuring the temperature evolution inside the test plate, the surface heat flux was calculated by the inverse heat conduction problem. In the case of no obvious run-off flow on the surface, the temperature TCHF and heat flux qCHF at the critical heat flux (CHF) point increased with Q. Besides, the values of TLeid and qLeid for the Leidenfrost point also showed similar variation. When V = 1.11 × 10-5 m3 s-1, the CHF points at locations around the spray center were forced to transfer to higher surface temperature, due to the run-off water flow from the spray center. Based on the results obtained, mathematical correlations were proposed, signifying the dependence of heat flux in different boiling regimes for water flow rates V ≤ 0.83 × 10-5 m 3 s-1. The results obtained in this study will provide a theoretical basis for predicting the temperature of the cold-rolled strip during the spray-cooling process and for designing the cooling process. © 2014 Elsevier Ltd. All rights reserved.


Zhang X.,University of Science and Technology Beijing | Wen Z.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Dou R.-F.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Zhang R.-J.,University of Science and Technology Beijing | Li Z.-Q.,University of Science and Technology Beijing
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

Evolution of recrystallization microstructure and hardness of cold rolled 430 stainless steel during isothermal annealing in the range of 650°C to 875°C were studied, and the recrystallization kinetics model was established. The results show that annealing temperature has significant effect on the recrystallization incubation time and the time for complete recrystallization, the recrystallization is completed at 825°C for 5 min and at 850°C for 34 s, however, full recrystallization is not observed, in the experimental time range for the temperature lower than 800°C. Finally, the recrystallization kinetics of this material is established by JMAK type model, the values of the Avrami exponent is in the range of 0.5 to 1.0, and its activation energy is 309.12 kJ/mol.


Zhang X.,University of Science and Technology Beijing | Wen Z.,Beijing Key Laboratory for Energy Saving and Emission Reduction of Metallurgical Industry | Dou R.,University of Science and Technology Beijing | Zhou G.,University of Science and Technology Beijing | Li Z.,University of Science and Technology Beijing
Materials Science and Engineering A | Year: 2014

This study investigates the effect of the annealing temperature on the microstructure, strength, elongation, and anisotropy properties of cold-rolled SUS430 stainless steel by a continuous annealing experiment. The SUS430 stainless steels of cold-rolled reductions of 84% and 60% were used in this study. The evolution of the microstructure and mechanical properties of SUS430 stainless steel during the annealing process was obtained. As continuous annealing proceeds, the softening behavior of the cold-rolled SUS430 stainless steel strip presented a two-stage trend characterized as recovery and recrystallization. Recovery mainly occurred at a temperature ranging from 600°C to 700°C. The hardness of the strip presented a certain decrease and unobvious change in microstructure was observed in this stage. Recrystallization of the deformed grains initiated at the temperature higher than 700°C, and the hardness of the strip decreased significantly. The mean recrystallized grain size of the sample cold rolled to 84% and 60% reductions are 13.5μm and 20μm, respectively. The tensile and yield strength of the specimens decrease as annealing temperature increases, and the elongation displays a sigmoidal increase with annealing temperature. Annealing temperature has little influence on the mean Lankford value (rm); however, an increase in cold-rolled reduction from 60% to 84% increases the value of rm from 0.9 to 1.3.The yield strength Re, the elongation δ, and the quantitative relationship between the yield strength Re and the softening fraction X were determined for cold-rolled SUS430 stainless steel in the range of εC R=1.0-2.2. The results of our study provide a theoretical basis for the prediction of the mechanical properties of cold-rolled SUS430 stainless steel as well as for the development of new annealing processes. © 2014 Elsevier B.V.

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