Prediction of Size Distribution of Particles Penetrating Dry Cyclone Separators

The efficiency of cyclones varies widely with the size of particles and complex mathematic formulations are used for predicting the collection efficiency of a single particle size. Numerical integration of the latter, in conjunction with the appropriate in each case input particle size distribution, or direct use of nomographs if lognormal input particle size distribution can be assumed, yields the overall efficiency. In either case, no information is available regarding the size distribution of the penetrating particles. As shown in this paper, lognormal input particle size distributions yield lognormal output particle size distributions. Based on this and on the analysis of functional relations, a set of nomographs is developed directly yielding the mean diameter and standard deviation of penetrating particles as a function of the input particle size distribution parameters and key cyclone design and operating conditions. The above set the stage for the rigorous computation of the size-specific emissions from cyclones and the overall and size-specific efficiencies of secondary control systems that may follow. This analysis is in line with current trends, which, on the basis of health considerations, place emphasis on the size-specific rather than on the overall particle emissions.     

高炉渣余热驱动空气布雷顿循环热力学分析

在高炉渣干式粒化余热回收装置的基础上,提出了高炉渣余热驱动的空气布雷顿循环装置,建立了该循环的有限时间热力学模型,对该装置的余热回收性能进行了研究。通过数值计算,分析了压气机压比、压气机进口相对压降（工质质量流率）和余热回收温度对循环功率、热回收效率和循环热效率的影响。结果表明：通过调整压气机进口相对压降和压气机压比,能使热回收效率和循环功率取得最大值;余热回收温度越高,循环功率、热回收效率和循环热效率也越高,同时,压气机进口相对压降的适用范围也越大。并以循环功率最大为目标,优化了压气机压比和压气机进口相对压降,得到了最大循环功率为51.46kW,最大热回收效率为11.98%,对应的循环热效率为20.71%。     

Simple Guide for Design of Air Vessels for Water Hammer Protection of Pumping Lines

Air vessels offer an effective means of reducing water hammer overpressures and negative pressures due to pump trip in pipelines. The process of sizing air vessels is simplified with the nomographs presented. Both air volume and total vessel size are calculated. The size can be minimized by correct selection of outlet and inlet connector diameter, and guides are provided to make these selections.     

Comparative Fractional Efficiency Predictions by Selected Cyclone Simulation Models

The recently introduced ambient air quality standards for fine particulates expand the use of available control system simulation models, from the prediction of total particulate matter removal efficiencies, to the prediction of PM2.5 and PM10 (particulate matter with diameters less than 2.5 and 10?μm) ones. In order to assess the suitability of cyclone simulation models for this task, the fractional efficiency predictions of six prominent models (Lapple, Leith and Licht, Dietz, Mothes and Loffler, Iozia and Leith, and Mothes and Loffler with the turbulent dispersion coefficient of Salcedo and Coelho) are compared for a number of “standard” cyclone design configurations under a wide range of cyclone diameters and pressure drops. The results reveal a significant discrepancy among model predictions, suggesting that at least some of the models considered are unsuitable for predicting size-specific (e.g., PM2.5 and PM10) cyclone efficiencies. They also show that the sensitivity of fractional efficiencies to changes in the configuration ratios, diameter, and gas pressure drop varies widely, and in some cases even in opposite directions, among models. The above-noted results demonstrate the need for a systematic model validation against credible and sufficiently extensive experimental data sets.     

Graphical Approach for Manpower Planning in Infrastructure Networks

Infrastructure networks such as highways and pipelines have recently been at the center of attention for contractors and owner organizations. Due to their large size and their repetitive/distributed nature, construction and/or maintenance operations for such networks become complex tasks that require huge resources, particularly manpower. In order to provide a transparent tool for quick manpower planning and sensitivity analysis, a graphical approach (using nomographs) is introduced in this paper. The nomographs encode the mathematical formulation, and the results of many optimization experiments, of a distributed model for scheduling large projects with multiple sites. Accordingly, the nomographs can be readily utilized by practitioners to estimate the manpower needed to meet a predefined deadline, under anticipated network-level risks due to unfavorable site conditions. Details on the development of the nomographs are presented in the paper along with an example to demonstrate their usefulness for supporting manpower planning decisions and for what-if analysis. The nomographs also present researchers with a simple yet powerful approach to make research results readily usable by practitioners.     

Potential Improvement in Biofilter Design through the Use of Heterogeneous Packing and a Conical Biofilter Geometry

Due to the heterogeneous distribution of microbial activities in a biofilter, biomass accumulation and clogging often occurs in the inlet sections, leading to a considerable increase in the total pressure drop and shortening of the bed material life span. We propose two new design concepts to optimize biofilter performance and reduce pressure drop by distributing biomass or pressure drop more homogeneously. One concept involves using a heterogenous packing system where the biologically more active inlet sections have larger particles and the less active outlet sections have smaller particles. This provides a more even distribution of microbial activity and pollutant degradation, resulting in a considerable reduction in the total pressure drop. The other concept involves using a conical biofilter geometry instead of the conventional cylindrical form. The varying cross-sectional area counteracts an uneven distribution of microbial activities and thus achieves a more uniform pressure drop along a biofilter. Experimental and/or simulation results showed that heterogeneous packing and conical geometry could result in more cost-effective biofiltration.     

喷雾干燥吸收工艺处理焚烧烟气的研究

从设计的角度出发，通过对危险废物焚烧工艺实际运行监测结果的分析，以控制脱酸烟气进出口温度、化学计量比、碱性液体浓度和碱性液滴粒径等工艺参数来研究危险废物焚烧烟气的净化效率与上述参数之间的关系。     

喷雾干燥吸收工艺处理焚烧烟气的研究

从设计的角度出发,通过对危险废物焚烧工艺实际运行监测结果的分析,以控制脱酸烟气进出口温度、化学计量比、碱性液体浓度和碱性液滴粒径等工艺参数来研究危险废物焚烧烟气的净化效率与上述参数之间的关系。     

阳极结构设计探析

阳极是预焙电解槽的核心部件。阳极质量直接影响阳极电流密度的提高及电解系列强化电流;阳极结构形式及各设计参数的确定与阳极电压降密切相关。本文提出阳极炭块质量标准及设计要求, 以降低电压降为主线, 分析阳极炭块形状尺寸、阳极钢爪数量、钢爪直径与炭碗孔径等对阳极压降的影响; 各项参数选取的依据, 探讨其合理的参数值; 对材料与温度的关系进行力学分析, 探讨减小生产中阳极钢爪热变形的方法。     

声波耦合旋流对转炉一次烟气细颗粒物的去除

针对钢铁厂转炉一次烟气含尘浓度高、颗粒物细的特点,提出一种声波耦合旋流除尘新技术,用于降低转炉一次烟气细颗粒物浓度。采用单因素试验和响应面法研究了声压级、声频率、停留时间及烟气进气方式对颗粒物浓度降低率的影响。单因素试验结果表明,转炉一次烟气颗粒物团聚效率随声压级升高而增大,但存在最佳团聚频率。相比单一声波团聚,声波耦合旋流除尘技术对细颗粒物有很好的团聚效果。响应面法优化试验得出,当声压级为140 dB、声频率为1 400 Hz、停留时间为8 s时,采用旋流进气方式颗粒物浓度降低率最高,达33%。研究结果为提高转炉一次烟气中细颗粒物的去除效率及工艺开发提供参考。     

声波耦合旋流对转炉一次烟气细颗粒物的去除

针对钢铁厂转炉一次烟气含尘浓度高、颗粒物细的特点,提出一种声波耦合旋流除尘新技术,用于降低转炉一次烟气细颗粒物浓度。采用单因素试验和响应面法研究了声压级、声频率、停留时间及烟气进气方式对颗粒物浓度降低率的影响。单因素试验结果表明,转炉一次烟气颗粒物团聚效率随声压级升高而增大,但存在最佳团聚频率。相比单一声波团聚,声波耦合旋流除尘技术对细颗粒物有很好的团聚效果。响应面法优化试验得出,当声压级为140 dB、声频率为1 400 Hz、停留时间为8 s时,采用旋流进气方式颗粒物浓度降低率最高,达33%。研究结果为提高转炉一次烟气中细颗粒物的去除效率及工艺开发提供参考。     

旋风子中气相流动特性及颗粒分离效率的数值研究

采用Fluent软件对轴向进口旋风子内的气相流场和颗粒分离效率进行了三维数值研究。用RNG（重整化群）κ－ε湍流模型模拟气相紊流特性。采用拉格朗日模型对固相颗粒的轨迹进行了模拟,并对固体颗粒的分离效率进行了分析。     

A mathematical model of aluminum depth filtration with ceramic foam filters: Part II. Application to long-term filtration

The mathematical model to compute the efficiency of depth filtration of molten aluminum, previously presented in Part I, was further developed and applied to study long-term filtration. In this case, the incoming suspension entering the unit cell was not assumed homogeneous, and the times and positions of particle at the inlet were obtained stochastically from a random number generator. The particles that were transported by the fluid flow to the wall and collided against this surface remained attached to the wall and accumulated within the domain. The accumulation of particles decreased the effective area for fluid to flow through the pore, causing distortion of the overall velocity field in the domain. The flow field was obtained from the numerical solution of the continuity and Navier-Stokes equations for transient flow, the particle trajectories were calculated using the Langrangian motion equation including the buoyancy, and the viscous drag force corrected for the wall effect. The model predicted a preferred particle accumulation around the windows to form a cake of particles and the effect that inclusion accumulation has on the flow field, pressure drop, and filtration coefficient. This work studied the influence of particle concentration and fluid velocity on the evolution of the filtration coefficient and pressure drop. It was found that these quantities were practically constant for TiB₂ particles suspended in aluminum at a concentration of 1 ppm and filtered during 60 minutes through the unit cell of a 30 ppi foam filter. However, at a particle concentration of 10 ppm, the model predicted that the filtration coefficient and pressure drop changed appreciably for the same period of filtration. The results, obtained from first principles, provide a rationale to explain fluctuations of the filtration coefficient and pressure drop, reported in the literature, without introducing any empirical or probability factor in the respective equations.     

Indoor Air Particulate Filtration onto Activated Carbon Fiber Media

Due to their bad effects on human health and comfort, removing particles and volatile organic compounds from indoor air has become an issue of major interest. In this study, the potential use of five media for particle removal was investigated: a felt, a cloth, and a knitted fabric made entirely of activated carbon fibers, and two prototype nonwovens made of different proportions of activated carbon and glass fibers. Dynamic filtration measurements were performed in experimental conditions as representative as possible of indoor air, with alumina particles (modal diameter: 0.37?μm), at an inlet concentration of 2,500?particles?cm?3 and for two different frontal velocities of air: 0.37 and 0.50?m?s?1. Although this medium was not designed for filtration, felt exhibited a high initial filtration efficiency (74%) for a low pressure drop (less than 210?Pa). Similarly, associating several layers of woven/knitted media in series led to high performances, as it reduced preferential paths for the airflow. Finally, prototype nonwovens appeared more efficient than activated carbon felt, but exhibited higher pressure drops.     

Experimental Study of Flow in a Vortex Drop Shaft

Model experiments were conducted to investigate the performance of a vortex drop structure with a relatively small height to diameter ratio. Detailed measurements of wall pressure and water thickness of annular jet flow were obtained along the vertical drop shaft, and the rate of air entrainment was measured. The results confirmed the high efficiency of energy dissipation in the vortex drop structure even for a relatively small drop height. The air entrainment rate was found to be significant, and good correlation was observed between the rate of air entrainment and the water jet velocity. The one-dimensional frictional free-vortex flow model was extended to include the effects of pressure forces. While the energy loss in the drop shaft can be simulated by correcting the friction factor, both the frictional model and the extended model significantly underpredict the wall pressure.     

直筒式脉冲电旋风除尘器内颗粒浓度分布实验研究

在脉冲电旋风除尘器研究的基础上,对直筒式脉冲电旋风除尘器内的颗粒浓度场进行测试分析,得出在一定入口风速、工作电压、入口粉尘浓度下除尘器内颗粒浓度分布规律及实测回归方程;进行不同供电方式下除尘器内颗粒浓度分布对比实验,研究表明脉冲供电可有效地降低除尘器内粉尘浓度,使除尘器内粉尘浓度分布趋向均匀。     

Method for Estimating Size-Specific Particulate Emission Inventories

Increasing evidence on the detrimental health effects of suspended fine particulates has prompted the introduction of new ambient air quality standards for particles with diameters smaller than 2.5 and∕or 10 μm and has created the need for size-specific inventories. To address this need, “generic” cumulative weight fraction data have been fitted with lognormal particle size distributions, and the resulting mean diameter dm and standard deviation σg values compiled for many sources of practical interest. In addition, nomographs are developed for assessing the mass fraction of particles with diameters <2.5, 6, 10, 15, and 30 μm as a function of the applicable dm and σg. The above data and tools allow easy extension of total particulate matter emission inventories for uncontrolled sources into size-specific ones. Supplemented with published typical efficiencies of control systems in the ranges 0–2.5, 2.5–6, and 6–10 μm, they also allow easy compilation of approximate size-specific inventories for controlled sources. In addition, used in conjunction with graphical models for selected control systems that predict the total efficiency and lognormal size distribution of penetrating particles, they offer a unique rigorous approach for size-specific inventories from controlled sources.     

包钢选矿厂磨矿工艺流程的改进

本文通过对包钢选矿厂原磨矿分级作业状况的分析,认为该工艺存在流程长,设备配置多,能耗高,旋流器分级效率低的问题.经理论计算和现场试验,提出了改进方案并加以实施.主要改进有:对磨矿流程进行了改进,将原三段旋流器分级改为二段;重新修订磨矿分级作业工艺参数;工艺设备重新配置.改进后,在系列原矿处理能力与改进前基本相同的情况下,磨矿最终产品细度及稳定性改进前后相当,能耗大大降低,年创经济效益410万元以上.     

Drop and Energy Characteristics of a Rotating Spray-Plate Sprinkler

A laboratory investigation was conducted to measure wetted radii and drop sizes and to estimate the energy characteristics of a rotating spray-plate sprinkler. Maximum wetted radii were positively related to increasing sprinkler elevation above an irrigated surface and increasing nozzle pressure. Nozzle diameter had a minimal effect on drop size, but nozzle pressure had a significant inverse influence. Energy parameters were calculated for sprinkler operational scenarios. Average kinetic energies over sprinkler-wetted areas were inversely related to nozzle pressure and the square of nozzle pressure. Rapidly and slowly rotating spray plate sprinklers had similar time-averaged specific power distributions. However, the rapidly rotating sprinklers had continuous rotational distribution patterns in space with relatively low peak specific power values that corresponded to natural rainfall intensities of about 20 mm/h. Slowly rotating sprinklers had discontinuous spatial distribution patterns with very high peak values that corresponded to natural rainfall intensities of about 200 mm/h.     

FX660旋流器组优化升级试验研究

银山矿业6500t/d铜硫选矿厂一段磨矿系统采用SABC流程,磨矿分级作业采用8台FX660旋流器(4开4备),该系统投产以来,随着生产的逐步稳定,磨矿系统台效由投产初期的270.8t/h提高到300t/h,旋流器溢流中-74μm级别含量达到65%以上,但+178μm级别含量达到9.36,略高于计划要求。为了降低旋流器溢流中+178μm级别的含量,对FX660旋流器进行优化升级,采用蜗壳预分级进料体新结构旋流器,同时对旋流器溢流管和沉砂嘴直径进行调整,将旋流器溢流中+178μm含量降低了3.02个百分点,-74μm级别提高了1.85个百分点,旋流器分级效率提高了1.77个百分点。分级作业返砂比降低了29.23个百分点。