钢铁企业污水深度处理后浓盐水处理实践

随着污水深度处理在钢铁企业的广泛应用,浓盐水合理处理已成为钢铁企业污水深度处理的关键环节。以某钢铁企业浓盐水处理为例,针对原水水质指标和浓盐水控制标准,设计了浓盐水处理工艺流程,介绍了各单元处理原理和作用。通过实际运行,详细分析了对化学需氧量(COD)、氨氮和总氮的处理效果,浓盐水经处理后可以达到《钢铁工业水污染物排放标准》(GB 13456—2012)中特别排放限值要求。一级脱盐浓水处理成本约为6元/m3,二级脱盐超浓水处理成本约为15元/m3。     

表面处理废物特性及处理处置方法探究

表面处理废物含铬、铜、镍、锌等重金属,兼具危害性和资源性。以表面处理废物为主要研究对象,分析了表面处理废物的化学组成、理化特性、重金属含量,同时概括了现有的处理方法,得出不同处理方法的优缺点,并进一步探究了其减量化的可行性。     

硬质合金制品强化处理技术

综述了硬质合金制品的强化处理方法,介绍了热处理、金属熔体渗透处理、振动处理及复合处理技术,并列举了强化处理的实例及其效果。     

污泥处理技术与发展趋势

概述污泥处理传统技术与现状,介绍卫生填埋处理、焚烧处理、土地利用处理、远洋倾倒或深海抛投处理等多种污泥处理技术,并对污泥处置的新技术和发展趋势作相关介绍。     

垃圾渗滤液处理技术研究进展

介绍了渗滤液产生来源和特点,指出垃圾渗滤液是一种非常复杂的、难以生物处理的污水,并对垃圾渗滤液物理化学处理、生物处理及土地处理法进行了探讨,重点介绍了渗滤液的土地处理,包括渗滤液回灌、人工湿地法和渗滤液矿化垃圾生物反应床处理技术,指出了土地法处理垃圾渗滤液无论在技术上还是经济上比较是可行的。     

垃圾渗滤液处理技术研究进展

介绍了渗滤液产生来源和特点,指出垃圾渗滤液是一种非常复杂的、难以生物处理的污水,并对垃圾渗滤液物理化学处理、生物处理及土地处理法进行了探讨,重点介绍了渗滤液的土地处理,包括渗滤液回灌、人工湿地法和渗滤液矿化垃圾生物反应床处理技术,指出了土地法处理垃圾渗滤液无论在技术上还是经济上比较是可行的.     

垃圾渗滤液处理技术研究进展

介绍了渗滤液产生来源和特点，指出垃圾渗滤液是一种非常复杂的、难以生物处理的污水，并对垃圾渗滤液物理化学处理、生物处理及土地处理法进行了探讨，重点介绍了渗滤液的土地处理，包括渗滤液回灌、人工湿地法和渗滤液矿化垃圾生物反应床处理技术，指出了土地法处理垃圾渗滤液无论在技术上还是经济上比较是可行的。     

软土地基处理方法

介绍了软土地基浅层和深层处理的常用处理方法.     

回转窑处理危险废物的工程设计

危险废弃物因其对环境极大的破坏性,以及对人类和牲畜健康的巨大威胁而需特殊处理。热处理法是最有效的危险废弃物处理方法,而回转窑是危险废弃物处理中最有效的设备。介绍了回转窑处理危险废物在国内外的应用现状,在分析各种回转窑特点的基础上,总结出了当前最适合处理危险废物的回转窑的形式。结合工程实际,详细介绍了回转窑处理危险废物系统的设计过程,并对回转窑处理危险废物工程焚烧系统中出现的常见问题进行了深入的剖析。     

凌钢钢渣处理生产实践

介绍了凌钢钢渣处理生产工艺流程、主要设备性能参数及钢渣处理关键技术环节,包括高温钢渣运输、焖渣效果控制、磁选设备安装和布置等,同时介绍了钢渣处理所回收产品的种类和用途,指出钢渣处理过程中存在的问题并提出了解决措施。实践结果表明:凌钢钢渣处理生产线经多次技改后,工艺布置合理,处理效果好,运行费用低,有效解决了钢渣外排带来的经济损失以及环保问题。     

Failure Resistance of Historic Stone Bridge Structure of Charles Bridge. II: Susceptibility to Floods

The paper is a follow-up to the first part devoted to an analogical problem investigated with a view to the degradation of the stone structure due to the effects of nonstress load, and it deals with the probability problem of the bridge structure collapse under the effect of an extreme flood wave. The paper presents the results of the numerical analysis of the response of the historic stone bridge structure of Charles Bridge of the 14th century to the flood wave effect simulated by angular rotation, subsidence, and shifting in the footing bottom of a bridge pier. Special focus is on the effect of interventions into the stone bridge structure dating back to the last major overhaul of 1967–1975, particularly, on the effect of the reinforced concrete slab (tie plate) connecting the opposite bridge breast walls increasing the rigidity of the breast walls and their structurally efficient connection to the vaults of the bridge arches. The numerical analyses performed point out the prevailing negative effects of the implemented interventions in terms of structural rigidity of the stone bridge structure exposed to the effect of a flood wave.     

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.     

New Orleans Levee System Performance during Hurricane Katrina: London Avenue and Orleans Canal South

Hurricane Katrina was one of the worst natural disasters in U.S. history. The effects of the hurricane were particularly devastating in the city of New Orleans. Most of the damage was due to the failure of the levee system that surrounds the city to protect it from flooding. This paper presents the results of centrifuge models conducted at Rensselaer Polytechnic Institute and the U.S. Army Corps of Engineers simulating the behavior of the levees at London Avenue North and South that failed during Hurricane Katrina. Those levees failed without being overtopped by the storm surge. Also included are the results of a centrifuge model of one levee section at Orleans Canal South, which did not fail during the hurricane. The key factor of the failure mechanism of the London Avenue levees was the formation of a gap between the flooded side of the levee and the sheetpile. This gap triggered a reduction of the strength at the foundation of the protected side of the levee. The results are fully consistent with field observations.     

Reliability-Based Optimal Design of Truss Structures Using Particle Swarm Optimization

In this work, the particle swarm optimization method is employed for the reliability-based optimal design of statically determinate truss structures. Particle swarm optimization is inspired by the social behavior of flocks (swarms) of birds and insects (particles). Every particle’s position represents a specific design. The algorithm searches the design space by adjusting the trajectories of the particles that comprise the swarm. These particles are attracted toward the positions of both their personal best solution and the best solution of the swarm in a stochastic manner. In typical structural optimization problems, safety is dealt with in a yes/no manner fulfilling the set of requirements imposed by codes of practice. Considering uncertainty for the problem parameters offers a measure to quantify safety. This measure provides a rational basis for the estimation of the reliability of the components and of the entire system. Incorporating the reliability into the structural optimization framework one can seek a reliability-based optimal design. For the problems examined herein, the reliability indexes of the structural elements are obtained from analytical expressions. The structure is subsequently analyzed as a series system of correlated elements and the Ditlevsen bounds are used for the calculation of its reliability index. The uncertain-random parameters considered in this work are the load, the yield-critical stress; and the cross sections of the elements. The considered design variables of the optimization problem are the cross-sectional areas of the groups, which control the size of the truss, and the heights and lengths that control the shape of the truss. The results of the optimization are presented for a 25-bar truss and a 30-bar arch and the robustness of the optimization scheme is discussed.     

Effect of Upward Seepage on Scour and Flow Downstream of an Apron due to Submerged Jets

The upward seepage through the bed sediment downstream of an apron of a sluice gate structure is a common occurrence due to afflux of the flow level between the upstream and downstream reaches of a sluice gate. The result of an experimental investigation on the characteristics of the scour hole and the flow-field downstream of an apron due to submerged jets under the influence of upward seepage through the bed sediment is presented. Experiments were run for the conditions of submerged jets, having submergence factors from 0.99 to 1.72 and jet Froude numbers from 3.15 to 4.87, over beds of sediments (median sizes = 0.8, 1.86, and 3?mm) downstream of an apron under upward seepage velocities. The characteristic lengths of the scour hole determined from the scour profiles are: the maximum equilibrium scour depth, the horizontal distance of the location of maximum scour depth from the edge of the apron, the horizontal extent of the scour hole from the edge of the apron, the dune height, and the horizontal distance of the dune crest from the edge of the apron, all of which were found to increase with an increase in the seepage velocity. Using experimental results, the time variation of the scour depth is scaled by an exponential law, where the nondimensional time scale decreases linearly with an increase in the ratio of the seepage velocity to the issuing jet velocity. The flow field in the submerged jets over both the apron and within the scour hole was detected using an acoustic Doppler velocimeter. The vertical distributions of time-averaged velocities, turbulence intensities and Reynolds stress at different streamwise distances, and the horizontal distribution of bed-shear stress are plotted for the conditions of scour holes with and without upward seepage. Vector plots of the flow field show that the rate of decay of the submerged jet decreases with an increase in the seepage velocity. The flow characteristics in the scour holes are analyzed in the context of the influence of upward seepage velocity on the decay of the velocity and turbulence intensities and the growth of the boundary layer.     

Reliability-Based Design for External Stability of Mechanically Stabilized Earth Walls

A two-phase approach was used to develop a reliability-based design (RBD) method for external stability of mechanically stabilized earth (MSE) walls. In the first phase, a parametric study was conducted using Monte Carlo simulation to identify parameters that affect the probability of external failure of MSE walls. Three modes of failure were considered: sliding, overturning, and bearing capacity. External stability was assessed by treating the reinforced soil as a rigid mass using the same procedures employed for conventional gravity-type wall systems. Results from the parametric study indicate that the mean and coefficient of variation of the backfill friction angle are significant for sliding, the mean and coefficient of variation of the friction angle of the backfill and coefficient of variation of the unit weight of the backfill are significant for overturning, and the mean and coefficient of variation of the friction angle of the foundation soil and the mean of the backfill friction angle are significant for bearing capacity. In the second phase, a series of additional simulations was conducted where the significant parameters identified in the parametric study were varied over a broad range. Results of these simulations were used to develop a set of RBD charts for external stability of MSE walls. A comparison indicates that similar reinforcement lengths are obtained using RBD and conventional methods and that the inherent probability of external failure in conventional deterministic design is ? 0.001. This probability of external failure is similar to inherent probability of failure reported by other investigators for similar geotechnical structures.     

Artificial Ground Freezing of Fully Saturated Soil: Viscoelastic Behavior

The transport and mechanical properties of saturated soil drastically change when temperatures drop below the freezing temperature of water. During artificial ground freezing, this change of properties is exploited in order to minimize deformations during construction work and for groundwater control. Whereas for the latter only the size of the frozen-soil body is relevant, which is obtained by solving the thermal problem, the design of the ground-freezing work for support purposes requires information about the mechanical behavior of frozen soil. In addition to the quantification of the improvement of mechanical properties during freezing, information about the dilation associated with the 9% volume increase of water during freezing is required in order to assess the risk of damage to surface infrastructure caused by frost heave. In this paper, a micromechanics-based model for the prediction of both the aforementioned phase-change dilation and the elastic and viscous properties of freezing saturated soil is presented. Hereby, the macroscopic material behavior is related to the behavior of the different constituents such as soil particles, water, and ice. Combined with the solution of the thermal problem, the proposed model provides the basis for predictions of the performance of support structures composed of frozen soil.     

Influence of Precipitates on Hydraulic Performance of Permeable Reactive Barrier Filters

A study was conducted to elaborate a predictive model that deals with the hydraulic conductivity reduction of permeable reactive barriers (PRBs) used for the in situ treatment of contaminated groundwater. As PRBs are composed of reactive and permeable filters through which the contaminated groundwater flows, their longevity has to be studied from both hydraulic and chemical points of view. Therefore, one-dimensional (1D) column filtration experiments were performed at a pilot scale, and an integrated model based on the solution of the advection-reaction-dispersion (ARD) mass balance equation was developed to study the space and time evolution of the hydraulic conductivity. This model uses the well-known Kozeny-Carman relation, which considers that permeability depends on the porosity and specific surface of the porous media. The ARD equation is solved by using the PHREEQC software with numerous capacities on the chemical point of view. Thanks to specific assumptions on the geometry of the precipitations, by using the floating-spheres model and the introduction of the “balanced time principle,” the evolution of the profiles of conductivity are computed and compared with those deducted from differential pressure measurements in the laboratory. Results of numerical simulations conducted with the model show that the largest porosity reductions occur on a 10-cm-thick layer at the entrance of the PRB as a result of precipitation of calcite minerals (prefilter).     

Pseudostatic Coefficient for Use in Simplified Seismic Slope Stability Evaluation

Pseudostatic slope stability procedures are commonly used in engineering practice. However, the selection of the seismic coefficient employed in the analysis is often based on precedence without due consideration of the amount of seismic displacement that constitutes satisfactory performance for each particular project and without incorporating the vastly different seismic exposure for sites around the world. In this Note, a rational basis for selecting the seismic coefficient is presented. The proposed procedure requires that the engineer establishes the project-specific allowable level of seismic displacement. The seismic response characteristics of the slope are represented by the fundamental period of the potential sliding mass, and the site-dependent seismic demand is characterized by the 5% damped elastic design spectral acceleration at the degraded period of the potential sliding mass. The level of uncertainty in the estimates of the seismic demand and displacement can be handled through the use of different percentile estimates of these values. With the proposed equations, the engineer can properly incorporate the amount of seismic displacement judged to be allowable and the seismic hazard at the site in the selection of the seismic coefficient.     

采场充填料浆流动与离析规律的试验研究

为研究采场充填料浆流动规律及充填料浆离析分层对充填体强度的影响规律,开展了充填料浆流动相似模拟试验及采场原位充填体力学强度测试试验,研究结果表明：单点下料时充填料浆流动终态坡面趋向于正态分布。流动过程中充填料浆产生离析分层现象,主要表现为充填体物料的粒径沿料浆流动方向呈先增大后减小的趋势,充填体强度沿料浆流动方向呈先减小后增大再减小的倒转“S”形趋势。采场原位充填体强度在下料口附近与标准试块强度接近,在采场中间位置附近的充填体强度最小,在距离下料点采场长度7/10左右的位置充填体强度达到最大值。研究成果能够为充填采场下料管的数量及位置设计提供依据,从而保证充填体的整体质量。