EDTA-Enhanced Washing for Remediation of Pb- and/or Zn-Contaminated Soils

The effects of the operating conditions, the initial concentrations of heavy metals in soils, and the competition among heavy metals during ethylenediaminetetraacetic acid (EDTA)-enhanced soil washing were extensively investigated using batch experiments with Pb- and/or Zn-contaminated soils aiming to determine the heavy-metal removal for different types of contaminations and to optimize the process parameters. Pb or Zn removal efficiency was found to be dependent on contact time, pH, concentrations of EDTA, and their initial concentrations in contaminated soils. The experimental results showed that the heavy-metal removal efficiency increased with a higher initial concentration of heavy metals in soils, and the concentrations of heavy metals in the solutions after washing were linearly correlated with their initial concentrations in soils. The study of the competition among heavy metals indicated that when EDTA was present in solution with the concentration less than the stoichiometric requirements, Pb removal efficiency was higher than that of Zn; on the other hand, when EDTA concentration was greater, Pb and Zn removal efficiencies were almost the same.     

Complicating Factors of Using Ethylenediamine Tetraacetic Acid to Enhance Electrokinetic Remediation of Multiple Heavy Metals in Clayey Soils

Batch and electrokinetic experiments were conducted to investigate the removal of three different heavy metals, chromium(VI), nickel(II), and cadmium(II), from a clayey soil by using ethylenediamine tetraacetic acid (EDTA) as a complexing agent. The batch experiments revealed that high removal of these heavy metals (62–100%) was possible by using either a 0.1?M or 0.2?M EDTA concentration over a wide range of pH conditions (2–10). However, the results of the electrokinetic experiments using EDTA at the cathode showed low heavy metal removal efficiency. Using EDTA at the cathode along with the pH control at the anode with NaOH increased the pH throughout the soil and achieved high (95%) Cr(VI) removal, but the removal of Ni(II) and Cd(II) was limited due to the precipitation of these metals near the cathode. Apparently, the low mobility of EDTA and its migration direction, which opposed electroosmotic flow, prevented EDTA complexation from occurring. Overall, this study found that many complicating factors affect EDTA-enhanced electrokinetic remediation, and further research is necessary to optimize this process to achieve high contaminant removal efficiency.     

喷雾推进冷却塔在炼钢氧枪冷却水系统的应用

介绍了喷雾推进通风冷却塔在济钢一炼钢厂氧枪冷却水循环系统中的应用。运行情况表明:较之传统的机械通风冷却塔,喷雾塔具有冷却效果好,节能效益显著,一次性投资省,运行维护可靠方便的优点。该塔在同类型企业中具有广泛的应用前景。     

Hydrothermal Modeling Studies of Cooling Tower Alternatives

The Environmental Effects Committee of the ASCE Energy Engineering Division has been developing a report on “Energy Production and Reservoir Water Quality” for publication. The report covers the regulatory framework that dictates much of the procedures for studies related to this topic, the fundamental reservoir hydrodynamics and water quality modeling used in preparing studies, the kinds of studies that can be prepared at different levels of analysis, and a series of applications that illustrate the problems encountered and applications of the various techniques. This study of hydrothermal modeling as applied to examining cooling tower alternatives for an existing steam electric station on a moderately large reservoir is included in this report and is presented here as an illustration of the types of studies included. This particular study subtended the usual steam electric plant cooling water discharge studies that relate to specific regulatory thermal plume size standards, and had to be designed around developing plant and cooling tower operations that would meet specific fisheries requirements for a zone of passage and refuge for fishes throughout the receiving embayment. After being used in developing cooling tower and plant operating details for the designers to work with, it was required that the hydrothermal modeling results be verified under actual tower operating conditions. In addition, it was required that the impact of the combined operations on dissolved oxygen be examined in detail. This paper covers the background to setting up the study, the kinds of statistical comparisons used to verify the hydrothermal studies, and similar studies for the analysis of dissolved oxygen distributions.     

Chemical-Enhanced Washing for Remediation of Soils Contaminated with Marine Diesel Fuel in the Presence/Absence of Pb

The effects of the operating conditions, the initial concentrations of marine diesel fuel (MDF) and the coexisting Pb in the soil, and the ethylene diamine tetra acetic salt (EDTA) in solution on MDF removal by sodium dodecyl sulfate (SDS) washing were extensively investigated with the aim of optimizing the process parameters and determining the MDF removal efficiency by SDS under different contamination conditions. The experimental results from batch tests indicated that the majority of MDF was removed by SDS in the first 2?h, and its optimal pH was nearly neutral. Increasing the SDS concentration linearly increased the MDF removal efficiency. At a given SDS concentration, the removal efficiency was dependent on the existing forms of MDF in soils, and the free phase of MDF was found to be more easily removed than the adsorbed phase. MDF removal by SDS was significantly reduced by the coexisting Pb in soils, which likely forms a complexation with SDS and thereby enhances the partitioning of MDF in the soil by the re-adsorption of released MDF onto the hydrophobic tails of the adsorbed SDS. EDTA alone, or with SDS, could remove MDF, but the remaining MDF in the contaminated soil after EDTA washing became more difficult to be removed by SDS. Therefore, the EDTA washing followed by SDS washing is not recommended for MDF removal.     

Ultrasonic subgingival root planing and EDTA etching in a one-step procedure

The purpose of the present study was to investigate if ultrasonic debridement and EDTA etching could be combined in a ore-step procedure. Tap water was exchanged for a 24% EDTA solution as irrigation agent during root planing with a piezo scaler. 24 human teeth extracted due to severe periodontal disease were used and the results were evaluated with scanning electron microscopy. Results indicate that synergistic effects (smear removal and exposure of collagen fibers) were negligible with conventional application of the irrigation fluid to the working area of the scaling tip while a marked effect was evident when the EDTA solution was applied directly to the working area of the piezoelectric scaler through a customized tip.     

磁处理对循环冷却水缔合程度的影响

基于L16(45)的正交试验，通过TDS、电导率以及表面张力的极差分析结果和最佳值出现差异的原因，综合研究了磁处理过程中各个因素对循环冷却水缔合程度的影响，发现在离子质量浓度为900 mg/L、温度为35 ℃、流速为0.4 m/s、磁场强度为0.5 T的情况下，TDS和电导率均达到最佳值，水分子的缔合程度和离子质量浓度也相应达到了最大值，此时磁处理的除垢效果最好。但表面张力达到最佳值时，水分子的缔合程度却出现了差异，主要表现为当其最佳值的条件不同于TDS和电导率的最佳条件时，水分子的缔合程度减弱了，结果导致磁处理的除垢效率减弱。当表面张力、TDS、电导率达到最佳值的条件一致时，磁处理是加强水分子缔合程度的，同样也增强了磁处理的阻垢效果。     

热装高炉高温煤气喷雾降温塔工艺计算

高炉原燃料热装工艺能显著提高铁前工序显热资源利用效率,为保证高温高炉煤气的净化回收系统安全,须在干法布袋除尘设施前设置喷雾蒸发降温塔。通过对干式喷雾蒸发降温理论进行分析,结合热装高炉操作变工况条件,推导出全套喷雾蒸发降温塔的理论计算方法。该方法可对塔内喷水量、降温塔出口煤气露点和含湿量、液滴蒸发时间、及塔体结构尺寸等关键技术参数进行便捷准确的计算,且易于计算机编程应用,对实际推广具有积极的意义。     

再生冷却塔优化改造可行性分析

CCPP焦煤二次净化系统运行已有三年多,文章通过对脱萘、脱苯再生冷却塔再生过程中存在的问题,进行论证分析,为下一步再生冷却塔的优化改造提供可行性理论依据。     

万立制氧机组增加氮气产量实践

在分子筛流程中,为了将制氧机组中空气预冷系统水冷塔的氮气替换出来并送入管网,采取了增设水冷机组冷却经污氮冷却的低温水的措施。采取措施后,出塔水温在不使用氮气的条件下达到了设计要求,满足了生产工艺条件,从而增加了氮气产量。     

热态上料高炉煤气蒸发冷却塔的设计及应用分析

热态上料高炉半净煤气的温度为600~700℃,需将其温度降低至250℃以下,以满足布袋除尘系统对煤气温度的要求。高炉煤气蒸发冷却塔作为干式冷却设备,它通过双流喷嘴将冷却水雾化喷入冷却塔内,利用水的汽化潜热将煤气温度迅速降低,同时也降低了煤气的含尘浓度。介绍了蒸发冷却塔原理及其系统组成,就某个项目做出蒸发冷却塔设计计算,并得出相应结论。     

提高电解废液冷却塔制冷能力的实践

分析电解新液温度对析出锌质量的影响,以及空气冷却塔制冷原理及制冷量不足的原因,根据冷却塔的制冷原理,提出几种改进措施并成功用于生产实践,大幅度提高了电解废液冷却塔的制冷能力,有效地控制了电解新液的温度。     

Bromate Formation by Ozone-VUV in Comparison with Ozone and Ozone-UV: Effects of pH, Ozone Dose, and VUV Power

The formation of bromate by ozone–vacuum ultraviolet (VUV) (185+254??nm) process in comparison with ozone and ozone-ultraviolet (UV) (254?nm) processes of coagulated and softened water was studied. The effects of pH (7, 9, and 11), ozone dosage (1, 2, and 4?mg O3/mg C), and VUV power (30, 60, and 120?W) were investigated. Bromate concentrations formed by the ozone-VUV process were up to four and six times less than those by the ozone and ozone-UV processes, respectively. Among the variables studied, ozone dosage had the most effect on bromate formation by the ozone-VUV process. Approximately 64 and 213% increases of bromate concentration were observed when the ozone dosage was increased from 1 to 2 and 4?mg O3/mg C with VUV power of 120?W at pH 7. The bromate formation also increased as VUV power and pH increased. Hydroxyl radical exposure had a positive relationship with ozone dosage and bromate formation. Results further indicated that it might be difficult to achieve the drinking water standard for bromate and high organic matter removal concurrently.     

循环水冷却塔节能改造必要性

介绍传统冷却塔电机减速机传动和十二五期间新研发的节能水能机,并以贵溪冶炼厂循环水冷却塔改造技术为例,即将冷却塔由水能机驱动风机旋转,代替传统冷却塔中的电机、联轴器、减速机,以减少设备投入,降低用电负荷,达到预期节能效果。     

Stimulatory effect of cooling tower biocides on amoebae

Two species of amoebae were isolated from the cooling tower of an air-conditioning system and examined for effects of exposure to four cooling tower biocides, a thiocarbamate compound, tributyltin neodecanoate mixed with quaternary ammonium compounds, another quaternary ammonium compound alone, and an isothiazolin derivative. The amoebae isolated were Acanthamoeba hatchetti and a Cochliopodium species. Two other amoeba cultures, an A. hatchetti culture and Cochliopodium bilimbosum, were obtained from the American Type Culture Collection (ATCC) and were also tested. The cooling tower isolates were more resistant to most of the biocides than the ATCC isolates were. The isothiazolin derivative was the least inhibitory to all four amoeba isolates, and tributyltin neodecanoate mixed with quaternary ammonium compounds was the most inhibitory to three of the four isolates. After exposure to lower concentrations of the biocides, including for one strain the manufacturer's recommended concentration of one biocide, the cooling tower amoeba populations increased significantly compared with unexposed controls, whereas the ATCC isolates were not stimulated at any of the concentrations tested. In some cases, concentrations which stimulated cooling tower amoebae inhibited the growth of the ATCC isolates. These results suggest that cooling tower amoebae may adapt to biocides, underscoring the need to use freshly isolated cooling tower organisms rather than organisms from culture collections for testing the efficacy of such biocides. The stimulatory effect of biocides on amoeba populations is an alarming observation, since these organisms may be reservoirs for legionellae. Biocides used to control microbial growth may actually enhance populations of host organisms for pathogenic bacteria.     

150 mm×150 mm方坯连铸二次冷却工艺的优化

石横特钢厂由R9 m 4机4流连铸机连铸150 mm×150 mm碳素和合金结构钢、高碳钢和焊条钢。通过优化二冷段工艺,将0.5~0.8 MPa水压、0.80~1.30 L/kg比水量和3段手动水冷工艺分别改成0.20~0.30 MPa水压、0.25~0.75 L/kg比水量和4段自动(水+气)水冷工艺后,杜绝了中间裂纹和鼓肚缺陷,并使脱方、缩孔、疏松缺陷降低了50%~80%。     

正火控冷工艺对Q460C钢板组织和性能的影响

采用正火控冷试验研究Q460C钢板的生产工艺,结合力学试验和金相组织研究正火控冷工艺对Q460C钢板组织和性能的影响,结果表明:钢板强度随水冷速度的增加和终冷温度的降低而增加,当冷却速度<3℃/s,对钢板的强度值基本没有影响;当冷却速度>3℃/s,钢板的强度值随冷速升高而提高;正火温度<920℃时,0℃冲击性能随温度的升高而增加,正火温度>920℃时,冲击性能逐渐恶化。     

Size Distribution of Heavy Metal Aerosols in Cooling and Spray Dryer System

The cooling process prior to treating flue gas and the spray dryer process that removes acid components in flue gas are believed to influence the mass and elemental size distributions of heavy metal in fly ash. The main objective of this study was to investigate the effects of operating parameters on the mass and elemental size distributions of heavy metals in fly ash produced from a fluidized bed incineration and a water cooling or spray dryer flue gas treatment system. The operating parameters investigated included (1) the controlling temperature in the gas cooling system; (2) the controlling temperature in the spray dryer system; (3) the addition of organic chloride; and (4) the addition of inorganic chloride. The experimental results indicated that the water cooling process and spray dryer process increase the amount of coarse fly ash (5–125 μm) and increase the total concentration of metal in fly ash. The amounts of fine fly ash (0.1–15.72 μm) and the total concentration of metal in fine fly ash increase with decreasing temperature during the water cooling process. However, the amounts of fine fly ash (0.1–15.72 μm) and the total concentration of metal in fine fly ash decrease with decreasing temperature during the spray dryer process.     

新型喷雾推进通风冷却塔的应用研究

喷雾推进通风冷却塔是具有多项专利技术的新型冷却塔，应用于轧钢循环水的处理还是首次。通过试验研究，为全面替代清水型逆流式玻璃钢冷却塔在冶金行业的使用提供了依据。     

正火控冷工艺对Q370QE钢板组织和性能的影响

采用正火控冷试验研究Q370q E钢板的生产工艺,结合力学试验和金相组织研究正火控冷工艺对Q370q E钢板组织和性能的影响,结果表明:钢板强度随冷却速度的增加和终冷温度的降低而增加,当冷却速率在8℃/s~14℃/s时,终冷温度在600℃~660℃之间,屈服强度增加约10 MPa~50 MPa,抗拉强度增加约0 MPa~20 MPa,组织为细化的铁素体和珠光体,满足桥梁钢所需的力学性能、冲击性能和焊接性能。