Abstract: The emission of flue gas in the iron and steel industry is high and contains a series of pollutants which that vary widely, especially in sintering process. With the depth of pollution control in China and the increasingly stringent emission standards, the flue gas pollutants of the steel industry require urgent management. At present, the sintering flue gas is mainly treated in the desulfurization and dust removal stages. Moreover, the measures for the management of nitrogen oxides and other pollutants have not yet been fully implemented in China's steel industry. Almost all the air pollution control techniques in the industry are aimed at single pollutant purification, where only few are targeted for multi-pollutant purification. Currently, the single pollutant treatment techniques can be divided into wet, semi-dry, and dry. Among them, the semi-dry and dry methods have gradually attracted much attention because of their high purification efficiency, compactness, and cost-effectiveness. Thus, they have become the main single pollutant treatment technologies for the sintering flue gas emission in the iron and steel industry. The present commonly used multi-pollutant removal technology is a single pollutant purification technique in series. With the increasingly stringent environmental standards in the steel industry, the original pollution control technologies and concepts have shown obvious deficiencies. This has seriously affected the development of China's iron and steel enterprises and smog management process. In addition, the tandem technology of single pollutant removal processes has the disadvantages of large area and high energy consumption. However, the simultaneous purification of multi-pollutants involves a simple process, short process flow, and low operation cost, and thus, it has become a research hotspot. Based on China's iron and steel industry sintering flue gas emission standards, emission characteristics, and current pollutant control technology, the technical ideas, characteristics and existing problems of multi-pollutant-coordinated control technology were analyzed, such as activated carbon adsorption process, LJS-FGD synergy pollutant purification process, MEROS technology, and a new type of dense semi-dry flue gas comprehensive management technology. Finally, some reasonable suggestions were presented for the development of multi-pollutants co-purification technology in the iron and steel industry.
Abstract: As a natural material, stone can suffer from initial damage (such as bedding and microfracture) during the diagenetic stage and rock defects (such as joints and faults) are formed after diagenesis. Under the influence of these defects, the properties of rock strength, deformation, and failure will also change. Studying the mechanical characteristics of defective rock can truly reflect the actual situation in the field. For the original hole fissures, actual rock engineering often contains fillings that decrease the stress concentration of the surrounding area of the hole; according to the type of filling, the filling can withstand the corresponding pressure. Thus, it is necessary to study the influence of the filling on the mechanical properties of porous rock damage. To study the influence of the filling material on the mechanical properties and the deformation and failure characteristics of the hole-bearing rock (with each specimen containing one hole), hole-bearing marble (with each specimen containing one hole), and plaster filling, the appropriate specimens were prefabricated in an indoor environment. The law of crack propagation of the specimens was analyzed based on the results of the uniaxial compression and acoustic emission tests and the results of CT scanning of the specimens before and after failure. The results are given as follows:(1) In comparison with hole-bearing marble, the peak stress of the marble specimen with the filled hole increases by 10.62%. Before the peak stress of the specimens, the pre-peak features are similar, and both specimens exhibit a stress reduction phenomenon; however, the post-peak characteristics are different, and the characteristics of partial deformation are more obvious. (2) After the peak stress phase, the acoustic emission features of the perforating hole in each hole-bearing specimen are more remarkable, and the crack propagation is more rapid than those of the gypsum-filled specimens, indicating the gypsum filling stems the crack expansion of the specimens. (3) A difference is found between the destruction model of the marble specimen with a hole and that of the marble specimen with the hole filled with gypsum. Each crack is relatively single for the specimen of marble with a hole, and main cracks exhibit tensile damage; moreover, wing cracks are more developed in the end, and some of those cracks propagate toward both sides, resulting in a block falling off. However, cracks around the hole are thinner and more dispersed, forming "X" shear damage because of the mutual crossing of the cracks.
Abstract: The top and bottom boundaries of sand-drained ground were visualized as impeded boundaries to investigate the effects of the pervious behaviors of the cushion above the top and the substratum below the bottom during the consolidation process of sand-drained ground. Based on the axisymmetric consolidation equations and the equal strain assumption, the consolidation solution of sand-drained ground with impeded boundaries was obtained using Hansbo's method for vacuum and surcharge preloading. The effects of the pervious coefficients of top and bottom boundaries on the consolidation degrees and settlements of vacuum preloading and surcharge preloading were analyzed. The similarities and differences between the solution and Indraratna et al.,'s solution and Zhou et al.,'s solution were compared under vacuum preloading alone. The results reveal the following:(1) for either vacuum or surcharge preloading, the consolidation degree of the ground increases with the increasing pervious coefficients of the boundaries when the consolidation time factor is the same; (2) for vacuum preloading, the larger the pervious coefficient of the bottom boundary is, the smaller the final settlement of the ground is, and the smaller is the settlement at the same time factor during the consolidation process; the larger the pervious coefficient of the top boundary is, the greater is the settlement at the same time factor during the consolidation process; (3) for surcharge preloading, the larger the pervious coefficient of the bottom or top boundary is, the larger is the settlement at the same time factor during the consolidation process while the final settlement remains constant; (4) when the top boundary is permeable during vacuum preloading, the consolidation degree of Zhou et al's solution is higher than the consolidation degree of the proposed solution, and the consolidation degree of the solution is higher than the consolidation degree of Indraratna et al's solution. The level of perviousness of the bottom boundary of ground should be reduced to increase the final consolidation settlement under vacuum preloading.
Abstract: Jordisite (MoS2) is one of the most difficult minerals to deal with in the development of molybdenum-containing mineral resources because of its characteristics of fine molybdenum content, low liberation degree, easiness of slime formation, and poor floatability. Much attention has been paid to develop an effective, economical, and eco-friendly processing method. In this study, a nonionic surfactant Tween 20 was used to improve the leaching of jordisite in the presence of Acidithiobacillus ferrooxidans. The effects of Tween 20 on the metabolic activity of A. ferrooxidans and on the bioleaching of jordisite were tested. After the bioleaching process, the jordisite was characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicate that the addition of Tween 20 has a negative effect on the Fe2+-oxidizing activity of A. ferrooxidans, but it is favorable for the sulfur-oxidizing activity of the bacteria. When added in low and high concentrations, Tween 20 enhances and reduces the bioleaching efficiency of jordisite, respectively; thus, it has a significant influence on the bioleaching. After 40 days, a dosage of 30 mg·L-1 Tween 20 increases the molybdenum extraction yield from 42.21% to 54.10% compared with the bioleaching without Tween 20. It is found that the presence of Tween 20 can accelerate the bio-oxidation of the elemental sulfur generated in the jordisite bioleaching process, consequently increasing the bacteria concentration. Meanwhile, Tween 20 addition reduces the amount of jarosite and elemental sulfur present on the minerals surface, weakening the passivation layer on the minerals surface. This accelerates the jordisite dissolution process, thereby increasing the molybdenum leaching efficiency.
Abstract: Pure aluminum is commonly used as the cathode electrode in the traditional hydrometallurgy applications of zinc electrowinning. However, with the decrease of zinc concentrate grade and increase of the impurity ions in the electrolyte, the corrosion consumption of the cathode material increases gradually. To further improve the corrosion resistance and electrocatalytic activity of the aluminum cathode, the electrochemical behavior of manganese as an additive for pure Al cathode material, such as Al-Mn alloy, was studied herein. Using the analysis methods of electrochemical impedance spectroscopy, cathodic polarization, galvanostatic polarization, and Tafel curves, the effect of Mn content on the electrochemical behavior of Al-Mn alloy in 40℃ constant temperature conditions and a solution containing Zn2+ at 65 g·L-1 and H2SO4 at 150 g·L-1 was investigated. The results show that the corrosion resistance of Al alloy containing Mn increases obviously compared to that of pure Al electrodes, and the increase of the Mn content could decrease the corrosion current. Moreover, the corrosion potential and the Mn content do not exhibit obvious change trends. When the Mn content reaches 1.5%, the corrosion current reaches the lowest value of 1.11 mA·cm-2 and the corrosion potential reaches the minimum of -1.0954 V. When the electrical potential of cathode becomes zero, the exchange current density is influenced by the Mn content and the exchange current density i0 exhibits an initial increasing trend and then declines with the increase of the Mn content. When the Mn content is 1.5%, the exchange current density of the Al alloy cathode reaches the maximum of 3.7462×10-16 mA·cm-2; this value is much higher than that of the pure Al electrode (4.8027×10-33 mA·cm-2). The overall change amplitude is obvious, and the electrocatalytic activity of the Al-Mn electrodes is much improved compared with a pure Al electrode. The electrochemical process is controlled by the electrochemical mass transfer. Considering the corrosion resistance and electrocatalytic activity of the electrode material, the Al-Mn alloy containing 1.5% of Mn can be used as an ideal electrolytic zinc cathode.
Abstract: Rubidium is a very active and highly dispersed rare alkali metal, which has a wide range of applications in space technology, electronics, bioengineering, and materials science. To date, no single mineral with the industrial exploitation of rubidium has been found. Rubidium is mainly associated with cesium lithium mica, pollucite, carnallite, potash, seawater, and salt lake brine. In recent years, a large amount of rubidium muscovite has been found in China, and they have become an important resource for extracting rubidium. If comprehensively explored, they will alleviate the shortage of rubidium resources in China. Therefore, it is imperative to develop a simple and highly efficient process for rubidium muscovite exploration. Here, a chlorination roasting process was proposed to recover rubidium from the distinctive rubidium-containing muscovite. According to the differential thermal analysis and thermogravimetric analysis (DTA-TG) curves of chlorinated roasting, the temperature of the chlorination reaction using calcium chloride is about 100℃ lower than that of sodium chloride, and the chlorination is more efficient with CaCl2 than NaCl. Subsequently, the impact of chlorination temperature on the rubidium extraction rate was investigated. The results show that the rubidium can be chlorinated only when the chlorination temperature reaches 800℃, whereby the rubidium extraction rate is 96.71%. The rubidium chlorination rate largely increases with, especially after 800℃; this shows that the high temperature is beneficial to the chlorination roasting of rubidium. Finally, the kinetics results of the chlorination roasting of the kaolin ore show that the extraction rate of rubidium is controlled by the chemical reaction, and the activation energy in the roasting temperature range is 42.22 kJ·mol-1.
Abstract: To solve the problems of slow training, weak generalization ability, and low prediction accuracy in the traditional prediction model established in terms of the BP neural network, a method of the quality prediction of the continuous casting bloom based on the extreme learning machine (ELM) was proposed to predict the degree of the center porosity and the central segregation of 60Si2Mn continuous casting bloom produced by Fangda Special Steel. Comparing the prediction models of the BP neural network and the GA-BP neural network, the results show that the prediction accuracy of the model based on ELM is improved to 85% and 82.5% in the center loose and central segregation, respectively, and the operation time is reduced to 0.1 s. The model can rapidly and accurately analyze the quality of a continuous casting billet, thus providing a new method for the online application of continuous casting billet quality prediction.
Abstract: The air environment strongly influences the damage behaviors of superalloys at high temperatures. To investigate the microscopic damage mechanisms during high-temperature fatigue crack growth in standard heat-treated GH4169 superalloys, low-cycle-fatigue crack growth tests were conducted at 650℃ with initial stress intensity factor ΔK=30 MPa·m1/2 and stress ratio R=0.05 under the air environment. The fracture surface, outside surface, and central sectioned surface of the specimen were observed and analyzed using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the main fatigue crack initiates and propagates intergranularly, followed by the appearance of intergranular secondary cracks, whose quantity and length increase along the propagating direction of the main crack. In the rupture stage, a dimpled morphology appears on the fracture surface. Oxidation occurs at the interfaces between δ phases and the matrix during the fatigue crack propagation process, which leads to secondary cracks propagating along the interfaces. This leads to their inflection, which in turn retards their propagation. A grain-boundary oxidation damage zone exists at the outside surface of the specimen near the main crack. The size and degree of grain-boundary cracking increase along the propagating direction of the main crack.
Abstract: 6061 aluminum alloy is a material that is widely used for manufacturing aircraft. Boron-sulfuric acid anodization is often used in the surface treatment of aluminum alloy to improve the corrosion resistance of the alloy in an outdoor atmosphere. However, few studies have been conducted on the galvanic corrosion of an anodized 6061 aluminum alloy coupled with high strength structural steel in an industrial-marine atmospheric environment. In this work, the outdoor atmospheric exposure test of an anodized 6061 aluminum alloy coupled with 30CrMnSiNi2A steel of different surfaces was conducted in an industrial-marine atmospheric environment. The corrosion behavior and mechanism of the anodized 6061 aluminum alloy coupled with steel were investigated by means of electrochemical measurement, corrosion product analysis, mechanical property testing, fracture analysis, and other measurements. After a one-year exposure test, the values of strength σb and elongation δ of the anodized 6061 aluminum alloy coupled with Cd-Ti plated 30CrMnSiNi2A steel decrease by 6.45% and 4.39%, respectively and have the lowest decline rate compared with the most serious decline rates of 10% and 62.28%, respectively, for the anodized 6061 coupled with naked 30CrMnSiNi2A steel and the moderate decline rates of 6.77% and 10.74%, respectively, for the uncoupled samples. The intergranular corrosion and pitting on the surface of anodized 6061 aluminum alloy result in a significant decrease in the mechanical property, with the deepest crack of intergranular corrosion reaching 150 μm. The sulfide in Qingdao atmosphere not only corrodes the surface of the samples to form aluminum sulfate but also permeates into the grain boundary to promote intergranular corrosion.
Abstract: Ca and Sr are the most effective modification elements in the casting of the Al-Si alloy, and they are usually added before casting when the alloy is in the form of the middle alloy. However, in the aluminum scrap melting regeneration industry, small amounts of Ca and Sr are often contained in the raw materials; as a result, controlling the mechanisms responsible for their contents in the raw aluminum scrap materials is a prerequisite for the reuse of such aluminum scrap during the melting process. This study aims to present the experimental investigation of the influences of the melting temperature and the holding time on the variational principles of the Ca and Sr percentage in an industrial A356 ingot during the melting process. The results indicate that the variations in the mass fractions of Ca and Sr both show Exp3P2 laws that continued decreasing gradually with the holding time and that the change rates of the mass fractions of Ca and Sr both improve with an increase in the melting temperature. Based on thermodynamic and dynamic analysis, the reactions of[Ca] and[Sr] with oxygen in the melt occur and CaO and SrO are produced in the first stage of aluminum scrap melting regeneration process; subsequently, Al2O3·6CaO and Al2O3·SrO are produced by the reactions of CaO and SrO with Al2O3, respectively, before the mass fractions of Ca and Sr finally decrease after slagging. In the middle and later stages of the melting regeneration process, the Ca and Sr percentages are reduced by[Ca] and[Sr] diffusing to the melt surface and then deoxidizing Al2O3. The apparent activation energies of Ca and Sr oxidation reactions calculated at 660~740℃ during the A356 melting process are 182.6 kJ·mol-1 and 117.8 kJ·mol-1, respectively, demonstrating that the both reactions are controlled by the chemical reaction process. The Ca and Sr mass fraction prediction models are established according to their variations and the forecast error is less than 10% by the production verification; thus, both mass fraction prediction models can be used to predict the mass fractions of Ca and Sr in scrap aluminum melting regeneration.
Abstract: With the rapid development of precision guidance and radar detection technologies, radar absorbing materials have gained popularity. Traditional radar absorbing materials are limited because of a high density and narrow absorption band. To improve the absorption properties of traditional radar absorbing materials, developing radar absorbing material with thin-layer, light-weight, broadband and strong-absorbing is necessary. The effects of Co-doping on the structure, morphology, and microwave absorption properties of reduced graphene oxide (RGO)/Fe3O4 composites were studied in this paper. The RGO/Fe3O4 and Co-doped RGO/FeFe3O4 composites were prepared via a one-step hydrothermal method. The effects of Co on the microstructure, phase composition, and valence state of the composite were analyzed using scanning electron microscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The relative complex permittivity and permeability of RGO/Fe3O4 and Co-doped RGO/Fe3O4 composites were within 2-18 GHz, as recorded by a vector network analyzer. The influence of Co-doping on the microwave absorption property of RGO/Fe3O4 was simulated. The results show that a part of Co participates in the hydrothermal reaction to form CoCO3, Co3O4, and Co2O3, whereas some Co exists in a simple form, and the Fe3+ coordination on the graphene oxide (GO) surface is affected through the positive and negative charge attraction mechanism, inducing Fe3O4 adhesion on the graphene surface. Co-doping improves the composites' electrical conductivity and magnetic loss ability thereby significantly enhancing their wave absorption property. Compared with RGO/Fe3O4, the maximum reflection loss of Co-doped RGO/Fe3O4 composites increases by 3.44 dB, and the effective absorption bandwidth of Co-doped RGO/Fe3O4 is broadened by 2.88 GHz when the matching thickness is 2.0 mm, whereas the maximum reflection loss increases by 8.45 dB, and the effective absorption band is broadened by 2.73 GHz when the matching thickness is 2.5 mm. The structure and morphology of RGO/Fe3O4 significantly changes by Co addition, which effectively improves the composites' absorption properties.
Abstract: Carbon-fiber reinforced polymer (CFRP) composites possess high specific stiffness and strength and have been widely used as structural materials in aerospace and aircraft engineering. In many practical applications, such as wing skin, loading condition is a complexity of tension, bending, and torsion. Therefore, fabricating CFRP composite laminates of multiple-angled plies is necessary to achieve balanced mechanical properties and meet the loading requirements under different working conditions. However, considering the size and weight limitations, designing a quasi-isotropic laminate with standard ply thickness (0.125 mm) is difficult. The recently developed spread-tow technique has provided a promising strategy to fabricate composite laminates of thin and light plies for the production of thinner and lighter laminates and structures and improvement of mechanical performance. Laminates fabricated using thin plies exhibit much higher strength in tension, compression, and impact as compared with standard-ply laminates because of the associated positive size effects. In the thin-walled structure, buckling stability is the primary factor determining the mechanical performance. In this study, composite cylindrical shells with different ply thickness (0.125, 0.055, and 0.020 mm) were fabricated via cross-ply and balanced stacking using the spread-tow technique, and their buckling behaviors under axial compression were studied. The experimental results show that with decreasing ply thickness, the critical buckling loads of composite cylindrical shells with cross-ply and balanced stacking under axial compression increase, whereas the buckling mode of composite cylindrical shells remains constant. Mechanical analysis indicates that the bending stiffness variation and interlaminar shear stress distribution play a key role in increasing the critical buckling load of the composite cylindrical shells, and the application of thin plies effectively improves the local buckling performance of the thin-walled composite structures.
Abstract: This paper investigates the anti-icing effect of hydrophobic coating, which has similar characteristics with a superhydrophobic surface. First, the factors affecting the wettability of water droplets on a solid surface were theoretically analyzed. Using hydrolytic condensation reaction, low-surface-energy materials were prepared based on a modified vulcanized silicone resin. Different sizes of silica particles were added in a fluorinated silicone resin to prepare the superhydrophobic coatings, considering the fractal theory. In the coating test characterization phase, the microstructure of the particles-doped coating surface and the contact angle of water droplets on different coating surfaces were investigated and analyzed. To visually analyze the effect of coating anti-icing property, icing tests were carried out in an icing wind tunnel after coating the test pieces by different coatings. The results show that the surface of the hydrophobic coating mixed with particles of different sizes forms a composite microstructure, which has a better roughness. The contact angle test result shows that the contact angle of water droplets on the fluorinated silicone resin-coated surface is 10° higher than that on the ordinary silicone resin-coated surface, and increases by nearly 20° in the coating with different particle sizes compared with the uniformly sized particles coating, thus achieving a superhydrophobic surface effect. The different coated test pieces were set in an icing wind tunnel to test their anti-icing abilities, and the results indicate that the superhydrophobic coating with a fractal structure after being cured does not only have a lower icing weight, which is reduced by 35.6% and 25.9% at the wind speed of 5 m·s-1 and 15 m·s-1, respectively, compared with the uncoated surface, but also has longer anti-icing effect than the uniformly rough surface. Therefore, the designed superhydrophobic coating has an outstanding anti-icing ability. In conclusion, the designed superhydrophobic coating achieves a superhydrophobic surface and has a better anti-icing performance, as confirmed through a series of performance tests.
Abstract: With an aim to address the disadvantages of the artificial bee colony algorithm of slow convergence speed and ease of falling into the local optimum in the later period of the evolution process as well as to improve the traditional artificial bee colony algorithm, the concept of the "global optimum" in particle swarm optimization is introduced. Therefore, an improved artificial bee colony algorithm, called particle bee colony (PBC), is proposed herein. First, the concept of degree toward optimum is proposed for measuring the degree to which the leader approaches or is removed from the "global optimum" in a limited iteration process. The individuals' values of degree toward optimum denote their "development potentials." The individuals that have a low degree toward optimum require a great mutation extent to find a good solution. Second, a new colony of bees, initiated by the particle bee, is uniquely developed. In mutation period, the leader will be changed into the scout or the particle bee according to the value of the degree toward optimum. The appearance of particle bees can increase the population diversity and expand the search area to a large extent. Next, analysis reveals that the sequence of population of the PBC is a finite homogeneous Markov chain and the population evolution process is monotonous. On the basis of the above observations, it can be proved that the population sequence of the proposed algorithm converges to the global optimum solution set with probability 1. Last, the algorithm proposed in this study is applied to numerical simulations of several classical test functions. Furthermore, the proposed algorithm is compared with the traditional artificial bee colony algorithm and other improved bee colony algorithms. The simulation results show that PBC increases the population dispersion and broadens the search area, thereby allowing the proposed algorithm to achieve fast convergence rate and high optimization accuracy.
Abstract: With the rapid development of service computing, cloud computing, internet of things, e-commerce, and modern logistics industry, cross-domain logistics services cooperation has become the main development trend of the modern logistics industry. The dynamic optimal composition of web services in logistics has become the key technology to create large and powerful logistics services based on the available logistics services of different companies that achieve seamless convergence of logistics services, satisfy user complex requirements, and realize the value addition. Recently, owing to the technologies of web services, cloud computing, and service sciences, an increasing number of logistics companies have registered themselves as logistics web service providers. The logistics services composition should satisfy the user's global QoS constraints and provide the best quality of service (QoS.) Currently, with the rapid development of cloud computing, e-commerce, service computing, and modern logistics industry, many logistics services are available on the network providing similar functions and different levels of QoS. These factors make the problem of determining the optimal composition of a logistics service a typical Np-hard problem. This study proposes a method to achieve the dynamic optimal composition of domain QoS and resource-aware logistics services and to realize logistics services that are dynamic, offer quality of domain services, and are aware of resource requirements. First, the learning artificial bee colony algorithm (LABC) is proposed; LABC is applied to decompose the global QoS constraints into local QoS constraints that logistics task nodes must satisfy and to transform the global optimization problem of logistics service composition into a local optimal service selection problem. Second, during the process of logistics service process execution, for each task node, the logistics service with best domain QoS evaluation, which can satisfy the local QoS constraints and resource requirements, is chosen to achieve a high-quality dynamic logistics service and optimal composition of service. The results of simulation experiments show that the proposed method is feasible and effective.
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
