Abstract: On the purpose of improving the utilization level of mine solid wastes and reducing the cost of backfill mining, this article reports an experimental study on preparing cementitious materials for backfilling by using water-granulated nickel slag. Mechanical and chemical activation methods were adopted to improve the cementitious activity of the slag. Taking the strength of backfill bodies as evaluation standards, the hydration activity and cementitious performance of the slag were investigated by changing the grinding fineness and activated agents, and the chemical activation mechanism was analyzed. The results indicate that the cementing agent prepared from the slag (occupying 85% of the total raw materials) can be used to replace cement and meet the production requirements of back-filling materials.
Abstract: A new pipe loop test platform was built to study the influence factors and levels of pressure loss in slurry pipe transportation. The influences of pipe inner-diameter, flow velocity, slurry concentration and particle size on the pressure loss were investigated. It is found that the influence of flow velocity on the pressure loss can be divided into two stages:when the flow velocity is less than the viscous transition flow rate, the pressure loss increases linearly with the increasing of flow velocity;but when the flow velocity is greater than the viscous transition velocity, the pressure loss increases in linear to quadratic polynomials with the increase of flow velocity, and the increasing rate is greater than that of flow velocity. The pressure loss negative-power decreases with the increasing of pipe diameter, but it exponentially increases with increasing slurry concentration. Under the same working condition, the pressure loss of fine-grained slurry is greater than coarse-grained slurry, the viscous transition velocity of fine-grained slurry is larger, but the in-crease in pressure loss of fine-grained slurry with flow velocity is relatively slow.
Abstract: This article presents experimental studies on the effects of H2 on the reduction degree and rate of limonite at different temperatures and kinetic analysis during the hydrogen reduction. The water loss of limonite was investigated by thermal gravimetric analysis. Limonite of 8 to 12 mm in granularity was reduced with 4 L·min-1 H2 at five temperatures of 750 to 950℃. As the reduction reaction proceeded, the reduction degree increased, and the sequence of 5 reduction degree curves was consistent with that of reaction temperature when t>28 min. The apparent activation energy was kinetically calculated to be 15.323 kJ·mol-1, so diffusion is the restrictive step of the reduction reaction.
Abstract: The evolution mechanisms of MgO-Al2O3 in the process of calcium treatment in non-oriented silicon steel were studied by laboratory experiments, with focus on the evolution process in the early and middle of calcium treatment. A small amount of MgO-Al2O3 surrounded by AlN was occasionally detected besides many pure spinels before calcium treatment. CaS or CaO formed as a tran-sient inclusion in the MgO-Al2O3 surface 1.5 min after calcium treatment. The composition from the inner part to outer part of inclu-sions was MgO-Al2O3, CaO-MgO-Al2O3 and CaO-Al2O3 in order 4.5 min after calcium treatment. 10 min after calcium treatment, unreacted MgO-Al2O3 spinels disappeared, and simultaneously CaO-MgO-Al2O3 and CaO-Al2O3 inclusions became homogeneous in composition. The phase stability diagrams of Al2O3/MgO-Al2O3/MgO and MgO-Al2O3/xCaO·yAl2O3 were calculated using thermo-dynamic data. The result showed that it was difficult to modify MgO-Al2O3 spinels with very high aluminum content. In combination with the scanning electron microscopy images, energy-dispersive spectra and element mappings of typical inclusions, the evolution route of an inclusion was described as MgO or Al2O3→MgO-Al2O3→CaO-MgO-Al2O3→CaO-Al2O3, and the alumina content occa-sionally showed a sudden increase besides a common decrease in the middle part of the product.
Abstract: Calcium aluminate clinkers, in which the mass ratio of Al2O3 to SiO2(A/S) is 5, were prepared at 1500℃ for 1h by proportioning pure reagents. The alumina leaching properties and crystal structure of 12CaO·7Al2O3 in the clinkers with different molar ratios of CaO unbonded with SiO2 to Al2O3 (C/A) were studied. The effect mechanism of C/A on the clinkers was also discussed by X-ray diffraction and X-ray fluorescence analysis. When C/A is 1.0 to 1.4, the alumina-leaching ratio improves because the amount of 12CaO·7Al2O3 increases with increasing C/A. When C/A is 1.4, the alumina-leaching ratio reaches the maximum value of 93.30%. In this case, 12CaO·7Al2O3 with defects forms, and the amount of substance of CaO is less than 11.3 mol. With the further increase of C/A, the alumina-leaching ratio decreases, which is because the preferred orientation of 12CaO·7Al2O3 changes from the (211) crystal plane into the (420) crystal plane.
Abstract: Germanium extraction from a high acid leach solution of zinc replacing slag by a new extractant, HBL101, was tested based on the current research status on extracting germanium from zinc smelting slag in hydrometallurgy. Investigations were performed on the effects of feed acidity, extractant concentration, extraction time, extraction phase ratio and temperature on the extraction, the effects of NaOH concentration, stripping time, stripping phase ratio and temperature on the stripping of germanium, and the conditions of extractant transformation. The results show that with 30% HBL101 in 70% sulphonated kerosene (volume fraction) as an extract-ant, the extraction rate of germanium from the solution with 113.2 g·L-1 H2SO4 reaches 98.57% in five-stage counter current extrac-tion with a volume ratio of oil phase to aqueous phase, O/A ratio, of 1:4 at 25℃ for 20 min. Germanium in the loaded organic can be selectively stripped using a 150 g·L-1 NaOH solution and the stripping rate reaches 98.1% in five-stage counter current stripping with an O/A ratio of 4:1 at 25℃ for 25 min. After germanium stripping, copper in the loaded organic can be stripped using a 200 g·L-1 H2SO4 solution and the stripping rate of copper reaches 99.75% in five-stage counter current stripping with an O/A ratio of 2:1 at 25℃ for 20 min. The extractant returns to extraction circularly.
Abstract: Optical microscopy, electron microscopy and physic-chemical phase analysis, in combination with thermodynamic calculations, were used to study precipitates and their precipitation regularity in Ti-microalloyed high-strength steel produced by CSP process. It is found that lots of spherical TiC and Ti(C,N) nanoparticles with a few of irregular shaped Ti4C2S2 above 100 nm in size exist in the steel with a yield strength of 700 MPa. TiN is completely precipitated from the steel before tandem rolling, but TiC mainly precipitates during coiling and cooling. The mass fractions of MC phases in the steel without Mo and the steel containing Mo are 0.049% and 0.043%, respectively. Owing to the addition of molybdenum, the amount of Ti precipitates in the steel containing Mo decreases while the precipitate size becomes smaller. The precipitation strengthening effects of the steel without Mo and the steel containing Mo are 126 MPa and 128 MPa, respectively.
Abstract: Combined with magnetic property measurements of thin grain-oriented silicon steel sheets annealed to different recrys-tallization stages, the deformation and recrystallization texture and microstructure evolution of the sheets was analyzed by using the electron back-scattering diffraction (EBSD) micro-texture analysis technique and X-ray diffraction texture analysis technique. The results show that the deformation texture transforms from {110}{001}to {111}{112} about the transverse direction. Meanwhile, it should be noticed that additional crystal rotation about RD which leads to the occurrence of a weak{001}{100} texture near the sheet surface appears in deformed grains, thus the origin of a cube recrystallization texture can be explained. As the annealing temperature increases, there occur abnormal grain growth and changes in magnetic properties, which are bound up with texture evolution including a beneficial {110} -{100}{001} texture and other weak texture components. Taking both abnormal grain growth and texture evolution into consideration, it is deduced that secondary and tertiary recrystallization occur. There exists crystallographic rotation about the{001} axis between different kinds of textural components at different recrystallization stages, so the recrystallization texture evolution of the sheets is believed to be driven by the growth dominance of grains having {100} rotational relationship with primary grains and the inhibition effect of the sharp Goss matrix. On the other hand, the abnormal growth of Goss grains induced by the strong advantage of {110} surface energy leads to a sharp Goss texture during tertiary recrystallization after annealing at high temperature for long time.
Abstract: The influences of stress ratio, single overload and high-low loading sequence on the fatigue crack growth of Z3CN20-09M cast austenitic stainless steels were studied with compact tension specimens. When the stress intensity factor range is identical, the fatigue crack growth rate increases with the increase of stress ratio. During single overload, the fatigue crack growth rate shows a short period of acceleration followed by a significant decrease, leading to subsequent crack growth retardation. Similarly, high-low loading sequence with the maximum load in the second step lower than that in the first loading step results in significant crack growth retardation in the second loading step. A two-parameter model and Wheeler's model are found to predict well the crack growth behavior under constant-amplitude loading and variable-amplitude loading, respectively.
Abstract: The temperature field, the equivalent plastic strain field, the highest temperature and the cooling problem of INCONEL718 superalloy in radial forging were studied with Forge simulation software. In the first pass, temperature rising is focused on the surface to the half radial distance area. After the second pass, the billet core is the highest temperature area, and the temperature becomes more uniform than before, even if 45℃ higher than the initial. The highest temperature of the billet during radial forging rises firstly and then falls slightly. Thermal radiation is the main cooling mode in all of the cooling methods. The simulation result of equivalent plastic strain indicates that the billet has been forged through after the second pass. At last, a comparison with sample observations shows that the simulation results are reliable.
Abstract: Nanostructured Fe2 O3 visible light photocatalysts with different morphologies were successfully synthesized from mill scales using a hydrothermal method. The leaching efficiency of mill scales was discussed by changing the leaching parameters such as hydrochloric acid concentration, liquid-to-solid ratio and reaction time. The dependences of the morphology and photocatalytic property of as-prepared Fe2O3 on the purity of leachates were investigated during hydrothermal synthesis. When the reflux reaction between 8 g of iron scales and 150 mL of 3 mol·L-1 HCl proceeds at 100℃ for 2 h, the leaching rate of iron scales reaches about 93% and the purity of leachates is high. It is indicated that impurity ions in the leachates play an important role in controlling the microstructure and the crystal growth direction of the nanostructured Fe2O3. Moreover, the nanostructured Fe2O3 has a better photocatalytic property, and it can degrade rhodamine B solution up to about 87% after 60 min under visible light illumination.
Abstract: Using potassium hydroxide as a modifier, Ti element was selectively enriched in potassium metatitanate from titanium-containing electric furnace molten slag, and magnesium aluminium spinel and forsterite were successfully converted to aluminates and silicates after the alkali fusion reaction between potassium hydroxide and the slag. The effects of calcining time, alkali/slag mass ratio and calcining temperature on the enrichment of Ti element and the phase transformation of magnesium aluminate spinel were investiga-ted by X-ray diffraction analysis. When the alkali/slag mass ratio is controlled at 1:2.1, the calcining temperature is 700℃ and the calcining time is 1 h, the highest diffraction peak of potassium metatitanate and the lowest diffraction peak of magnesium aluminium spinel appear, suggesting that the selective enrichment of Ti element and the phase transformation of magnesium aluminium spinel are efficiently realized. It is verified that a higher molar ratio of K2O to TiO2 plays an important role in the formation of potassium metati-tanate. Using this alkali fusion slag obtained under the optimum conditions as raw materials, potassium hexatitanate nanowhiskers can be successfully synthesized by subsequent processing at 850℃.
Abstract: Sm2O3 partly doped La2Ce2O7 ceramic materials for thermal barrier coatings were prepared by high temperature solid-state reaction using La2O3, CeO2 and Sm2O3 as raw materials. Their chemical formula is (SmxLa1-x)2Ce2O7. The phase composition of the samples was studied by X-ray diffraction (XRD). The doping ratio, firing temperature and firing time were investigated by an XRD pattern contrast analysis of the samples made in different conditions. It is found that the sample with fluorite structure has been prepared, and it can maintain its phase structure when the doping molar ratio Sm:La is 1:2 or 1:3. As the doping molar ratio Sm:La is 1:2 at the firing temperature of 1550℃ for 10 h, the prepared (Sm0.33La0.67)2Ce2O7 has a good phase stability at 1600℃. This material can be potentially used as a new material for ceramic thermal barrier coatings.
Abstract: Uniform gas distribution in a radial flow adsorber plays an essential part in its performance. A 3D hydrodynamic and mathematical model of the radial flow adsorber was developed based on experimental studies. The effects of flow patterns, the cross-section ratio of central channel to outer channel, and the opening ratios of the central channel and the outer channel were comparatively studied by using this model. Radial inward flow was proved to have a better performance than radial outward flow, and the∏ type of inward flow is a little better than that of the Z type of inward flow. The best effect can be obtained when the cross-section ratio of central channel to outer channel is 18.9%. The radial non-uniformity of velocity decreases with the decrease of the opening ratio of the central channel, and the effect of flow distribution is better. But if the opening ratio of the central channel is too low, it will cause uneven local flow distribution and high energy consumption. The opening ratio of the outer channel has a little influence on flow distribution in the radial flow adsorber.
Abstract: A mixed integer linear programming (MILP) model for optimization of surplus byproduct gases was built with the mini-mum operation cost as its objective function. Compared with previous optimization models, this model chooses a shorter time period and considers the influence of boiler penalty values (BPV) and gasholder penalty values (GPV) on the optimization results. Calculation results by the model based on real production data indicate that GPV and BPV are sensitive to the optimization results. Thus it is necessary to evaluate GPV and BPV reasonably. Compared with manual operation results, the optimal calculation results are able to re-duce the gas storage fluctuation of the gasholder, improve the electricity generation of boilers by 45.9%, and thus make the operation of the byproduct gas system safe and stable.
Abstract: The process parameter of coiling temperature is the most critical factor to determine the final mechanical properties of strip steel. In the production practice, it is difficult to improve the coiling temperature accuracy of heavy gauge strip steel. Based on the condition characteristics of the laminar cooling process of heavy gauge strip steel, improvement methods were proposed for the temperature field calculating model and the heat transfer coefficient model, and a new similarity-based adaptation model was developed to improve the feed forward control effect of coiling temperature. Field applications prove that the proposed scheme can effectively improve the coiling temperature accuracy of heavy gauge strip steel, and the average hitting rate is about 94.9% for the strips with a thickness more than 12 mm.
Abstract: A batch scheduling problem of hot-rolled bars was discussed according to the influences of process conditions and due date on the continuous production of rolling units. A mathematical model with three objectives to minimize the setup time, tardiness penalty and steel grade bounce penalty was constructed, and a method of the variable neighborhood search algorithm embedding the earliest due date first (EDD) rule was proposed to solve the model. In consideration of constraints in the model, an initial solution was generated by constraint satisfaction technology. Then, to meet the actual production needs, a variable neighborhood search method was designed to minimize the setup time, which is considered as a primary objective. In this algorithm, a hybrid operator is applied in sha-king and local search, and the idea of simulated annealing is introduced to take control of the acceptance of new solutions. Meanwhile, in order to minimize the tardiness penalty and the steel grade bounce penalty, the earliest due date first rule and the steel grade sorting rule are applied. Experiment results show that the model and the algorithm are feasible and effective.
Abstract: Considering the phenomenon of inventory stimulating demand in real life, this article introduces an optimal control model of production inventory systems. In this model, the production rate and price level are control variables, the production rate is bounded, the inventory level is state variables, and the demand rate depends on the inventory level and price level. Three possible solutions are achieved according to different values of model parameters using the maximum principle and are analyzed in detail. By applying the model to a numerical example, a concrete transformation process of the system state is presented. In comparison with the case that demand does not depend on inventory, the impact of demand depending on inventory comes to light.
Abstract: A general chaotic stream encryption scheme is proposed by using two chaotic systems which topologically conjugate with Tent map and a method to generate independent and identically distributed chaotic streams. The stream encryption scheme is similar to the digital envelop, but the difference is that we only transport the initial values of Tent map and the parameters of the two chaotic sys-tems as the initial key. According to the conjugate relation, the initial values of the chaotic systems are obtained to achieve the purpose of masking these initial values. We calculate two independent and identically distributed chaotic key streams based on the two chaotic systems to encrypt the plaintext through twice feedback XOR. An application result of image cryptograph illustrates that the stream en-cryption scheme is effective and secure.
Abstract: Concurrent multipath transfer (CMT) uses the stream control transmission protocol's (SCTP) multihoming feature to distribute data across multiple end-to-end paths in a multihomed SCTP association. Due to the disparity of multipaths, it is facing a great challenge to solve the disorder of received data packets. In order to lighten the reordering degree and then to improve the through-put performance, we need to estimate the bandwidth and round trip time (RTT) of the real-time paths as exactly as possible. In this paper, we use the extended vector Kalman filter to predict the available bandwidth and RTT of each path simultaneously. Based on this, we propose a predictive path selection algorithm for CMT in SCTP. Simulation results show that the path selection algorithm can lessen the data packets disordering by correctly predicting each path's bandwidth and RTT in real time. To bandwidth sensitive scene,the algorithm can converge more quickly than Kalman-CMT and can improve the system total throughput in a certain extent. To time and bandwidth sensitive scene, the algorithm can greatly improve the convergence speed and total throughput than Kalman-CMT.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
