基于GT-Power柴油机颗粒捕集器捕集性能的仿真研究

利用GT-Power软件建立了柴油机颗粒捕集器(DPF)仿真模型,进行了仿真计算。研究了颗粒捕集器本身结构参数对其捕集效率与压降的影响。结果表明,影响颗粒捕集器捕集效率的主要参数有通道密度(CPSI)、过滤体孔隙率、过滤体微孔直径以及过滤壁厚度;影响颗粒物压降的主要参数有通道密度、过滤体渗透率、过滤体孔隙率以及过滤壁厚度。     

改性锰砂滤料处理高铁锰煤矿矿井水

采用KMnO4溶液浸渍法制备了新型改性锰砂滤料,研究了滤料表面性能和过滤处理高铁锰矿井水的效果。结果表明,锰砂滤料除铁锰性能优于石英砂、陶粒以及瓷砂,采用KMnO4溶液浸渍能够提高锰砂滤料的过滤性能,最优的浸渍浓度为5%。5%KMnO4改性锰砂滤料过滤处理高铁锰矿井水的最佳工艺参数为：过滤周期24 h,反冲洗强度3.2 L/（s.m2）,反冲洗时间5 min;通过比表面积测试分析和SEM表征分析发现,KMnO4溶液浸渍能够提高锰砂滤料比表面积,并在锰砂滤料表面形成了氧化膜,从而提高除铁除锰效果,而且浸渍液浓度越高,这种作用越明显。     

Panel Bed Filters for Simultaneous Removal of Fly Ash and Sulfur Dioxide:

Experimental studies of the filtration of dilute aerosols of Dow microspheres by beds of sand have been conducted with flows passing vertically upward, vertically downward, and horizontally. With the use of Happel’s “free surface” model for a granular bed, the results can be correlated reasonably well by semiempirical, semitheoretical considerations taking into account collection by diffusion, gravity settling, direct interception, and inertial impaction. The results are preliminary to experiments to be made on filtration of aerosols by a filter cake of fly ash resting upon a sand bed.     

浸没式超滤膜替代砂滤处理东江水的中试研究

针对传统饮用水处理工艺的升级改造问题,通过中试实验,系统考察浸没式超滤膜替代砂滤处理东江水的出水水质并研究高通量条件下的膜运行条件。结果表明,浸没式超滤膜出水浊度不受原水水质条件影响,均保持在0.1 NTU以下,与砂滤出水相比具有优势,但有机物去除率与砂滤相差不大。膜系统在高通量条件下运行时,过滤周期应作适当的缩短,采用合理的物理清洗来缓解膜污染,并辅助以有效的在线化学清洗可保证膜过滤的长期稳定运行。     

Development and application of kinetic model on biological anoxic/aerobic filter

An up-flow biological anoxic filter (BANF) has been developed to achieve high removal performance of suspended solids and BOD removal as well as nitrogen. With a view to understand treatment mechanisms, we developed a filtration model that incorporates filtration, deposit scoring and biological reactions simultaneously. The biological reactions consist of four types of reaction; dissolution of organic particles; utilization of dissolved organic matter; denitrification; and self-degradation of bacteria. Whereas the reactor is generally assumed to be a plug flow reactor in the filtration model, it is assumed a continuous-flow stirred tank reactor (CSTR) in the model of biological reactions. The hydrodynamics is supposed that the filter bottom (the portion sludge settled) is a CSTR and the filter bed (the portion filled with filter media) consists of number of CSTR of equal size arranged in series. The model obtained in this study was verified and simulated using experimental results taken from a pilot-scale plant and predicted the experimental data well, applying to design and operate BANF.     

D型滤池在成都沙河污水处理厂深度处理中的应用

成都沙河污水处理厂二沉池出水进行深度处理的过滤单元采用德安公司研制开发的D型滤池.其核心技术是采用DA863彗星式纤维滤料作为内部填料,该填料具有过滤精度高、滤速快、自适应等特点,可进行直接过滤.对D型滤池内部结构、功能和运行工艺参数等作了较为详细的介绍.通过实际运行,D型滤池的出水SS小于10 mg/L,达到了设计要求.     

Minimization of the formation of disinfection by-products

The drinking water industry is required to minimize DBPs levels while ensuring adequate disinfection. In this study, efficient and appropriate treatment scheme for the reduction of disinfection by-product (DBPs) formation in drinking water containing natural organic matter has been established. This was carried out by the investigation of different treatment schemes consisting of enhanced coagulation, sedimentation, disinfection by using chlorine dioxide/ozone, filtration by sand filter, or granular activated carbon (GAC). Bench scale treatment schemes were applied on actual samples from different selected sites to identify the best conditions for the treatment of water. Samples were collected from effluent of each step in the treatment train in order to analyze pH, UV absorbance at 254 nm (UVA₂₅₄), specific UV absorbance at 254 nm (SUVA₂₅₄), dissolved organic carbon (DOC), haloacetic acids (HAAs) and trihalomethanes (THMs). The obtained results indicated that using pre-ozonation/enhanced coagulation/activated carbon filtration treatment train appears to be the most effective method for reducing DBPs precursors in drinking water treatment.     

Evaluation of methods to determine adsorption of polycyclic aromatic hydrocarbons to dispersed carbon nanotubes

A number of methods have been reported for determining hydrophobic organic compound adsorption to dispersed carbon nanotubes (CNTs), but their accuracy and reliability remain uncertain. We have evaluated three methods to investigate the adsorption of phenanthrene (a model polycyclic aromatic hydrocarbon, PAH) to CNTs with different physicochemical properties: dialysis tube (DT) protected negligible depletion solid phase microextraction (DT-nd-SPME), ultracentrifugation, and filtration using various types of filters. Dispersed CNTs adhered to the unprotected polydimethylsiloxane (PDMS)-coated fibers used in nd-SPME. Protection of the fibers from CNT adherence was investigated with hydrophilic DT, but high PAH sorption to the DT was observed. The efficiency of ultracentrifugation and filtration to separate CNTs from the water phase depended on CNT physicochemical properties. While non-functionalized CNTs were efficiently separated from the water phase using ultracentrifugation, incomplete separation of carboxyl functionalized CNTs was observed. Filtration efficiency varied with different filter types (composition and pore size), and non-functionalized CNTs were more easily separated from the water phase than functionalized CNTs. Sorption of phenanthrene was high (< 70%) for three of the filters tested, making them unsuitable for the assessment of phenanthrene adsorption to CNTs. Filtration using a hydrophilic polytetrafluoroethylene (PTFE) filter membrane (0.1 μm) was found to be a simple and precise technique for the determination of phenanthrene adsorption to a range of CNTs, efficiently separating all types of CNTs and exhibiting a good and highly reproducible recovery of phenanthrene (82%) over the concentration range tested (70–735 μg/L).

     

长纤维过滤器过滤过程的数值模拟

在长纤维束过滤器动力学模型和现场实验数据的基础上,利用Comsol Mulitiphysics仿真软件对长纤维束过滤器过滤过程进行数值模拟。将3类仿真曲线(滤出水颗粒浓度随时间的变化曲线、滤液浓度沿滤层的变化曲线、滤床各层比积泥量的变化曲线)与实验所得的真实曲线分别进行对比,两者比较接近。说明该过滤过程模型可用于影响长纤维束过滤器运行特性中单个或多个变化因素(初始滤速、纤维束装填密度、流入浓度和纤维丝直径等)实验结果的估算,可作为长纤维过滤器的实验研究、操作优化和结构设计的参考。     

Feasibility of granular bed filtration of an aerosol of ultrafine metallic particles including a pressure drop regeneration system

A process for filtering an aerosol of ultrafine metallic particles (UFP) has been designed and tested, based on the principle of a multistage granular bed. The filtration system comprised a succession of granular beds of varying thickness composed of glass beads of different diameters. This system allows the pressure drop to be regenerated during filtration (“on-line” mode) using a vibrating probe. Tests monitoring the pressure drop were conducted on a “10-L/min” low airflow rate device and on a “100-m³/hr” prototype. Granular bed unclogging is automated on the latter. The cyclic operation and filtration performances are similar to that of filter medium-based industrial dust collectors.

Implications:?Filtration of ultrafine metallic particles generated by different industrial processes such as arc welding, metal cutting, or spraying constitutes a difficult problem due to the high filter clogging properties of these particles and to the high temperatures generally encountered. Granular beds represent an advantageous means of filtering these aerosols with difficult properties.     

Performance of a Pulse-Jet Filter At High Filtration Velocity II. Filter Cake Redeposition

Pulse-jet filter cleaning is ineffective to the extent that collected dust redeposits rather than falls to the hopper. Dust tracer techniques were used to measure the amount of redeposition in a pilot scale pulse-jet filter. A mathematical model based on experimental results was developed to describe dust transfer from bag to bag, redeposition on the pulsed bag itself, and migration to the dust hopper. Dust redeposition upon the pulsed bag increased markedly with increasing filtration velocity, whereas migration and redeposition on bags adjacent to the pulsed bag decreased. For high velocity pulse-jet filters to operate at lowest possible pressure drop, filter cake redeposition must be minimized.     

Preparation of electrospun polyurethane filter media and their collection mechanisms for ultrafine particles

Electrospinning is a simple and versatile process to produce polymer nanofibers, which are useful for ultrafine particle filtration. In this study, a polyurethane filter with an average fiber diameter of 150–250 nm was prepared through the electrospinning process and its filtration characteristics were investigated. We found that the electrospun fiber diameter was highly dependent on the polyurethane concentration, electric field, and tip-to-collector distance. As the polyurethane concentration, electric field, and tip-to-collector distance under the same electric field increased, the fiber diameter increased. We also found that the produced filter media had a minimum collection efficiency at particles sizes from 80 to 100 nm, which implies an electrostatic attraction between the filter and the test particles. Furthermore, we observed that interception was a predominant collection mechanism at Peclet numbers higher than 10 in nanofiber filtration for ultrafine particles.

Implications:

A polyurethane nanofiber filter with excellent mechanical properties was prepared, and the effect of operating conditions on fiber morphology was examined. The filter fabricated by an electrospinning process is charged and has high filtration efficiency due to electrostatic force. Therefore, it can be a good alternative to control hazardous ultrafine particles.     

Effects of filtration and pH perturbation on freshwater organic matter fluorescence

Fluorescence of organic matter from six contrasting freshwaters was analysed after filtration (1.2 microm and 0.2 microm filter sizes) and pH perturbation (+/-2 pH units from ambient conditions). Two fluorophores were compared in detail: tryptophan-like fluorescence, whose filtration and pH characteristics are relatively poorly understood, and humic-like fluorescence, which is better characterised. Although there was some variability in both fluorophores, the tryptophan-like fluorescence showed the most significant decrease in fluorescence intensity between raw and 1.2 microm filter samples, and a much smaller decrease between 1.2 and 0.2 microm, demonstrating a significant source associated with particulate material as well as a significant <0.2 microm fraction. In contrast, humic-like fluorescence shows little change with filtration, suggesting that the majority of this fluorescence is associated with truly dissolved material. The pH perturbation experiments demonstrate that tryptophan-like fluorescence is less impacted by pH than with filter fraction. For humic-like fluorescence, pH effects are weak and are not as consistent as those reported in the literature for extracted humic substances. pH perturbation of the freshwaters shows a wide range of sample specific pH responses, significantly more variable than that observed in experiments using extracted humic substances and tryptophan standards, demonstrating the natural variability of freshwater dissolved organic matter.     

板框压滤机内酒精污泥过滤脱水特性

采用螺杆泵输送和板框过滤机压滤的方法对酒精污泥进行机械脱水,研究了絮凝剂(聚丙烯酰胺PAM)添加量、污泥的进口湿含量、螺杆泵转速、过滤介质和过滤时间对污泥过滤特性的影响,并对滤饼吹气压榨进一步脱水。实验表明,在PAM添加量wPAM=3 kg/(t干污泥),污泥的进口湿含量x0=95%,螺杆泵转速n=180 r/min,过滤时间t=2.5 h并进行吹气压榨可将污泥的湿含量降至69.91%。     

Modeling depth filtration of activated sludge effluent using a compressible medium filter.

A new filter, using a compressible-filter medium, has been evaluated for the filtration of secondary effluent. The ability to adjust the properties of the filter medium by altering the degree of the medium compression is a significant departure from conventional depth-filtration technology. Unlike conventional filters, it is possible to optimize the performance of the compressible-medium filter (CMF) by adjusting the medium properties (i.e., collector size, porosity, and depth) to respond to the variations in influent quality. Because existing filter models cannot be used to predict the performance of the CMF, a new predictive model has been developed to describe the filtration performance of the CMF and the effect of medium-compression ratio. The model accounts for the fact that the properties of the filter medium change with time and depth. The model, developed for heterodisperse suspensions and variable influent total suspended solids concentrations, can be used to predict all possible phases of filtration (i.e., ripening, constant removal, and breakthrough). A hyperbolic-type, second-order, nonlinear, partial-differential equation was derived to model the CMF. The equation was solved using the finite-difference numerical method. The accuracy of the numerical method was tested by a sensitivity analysis and a convergence test. The model is first-order accurate with respect to medium depth and time. Field data were obtained for the filtration of settled secondary effluent using a CMF with a capacity of 1200 m3/d. Model predictions were compared with observed performance from filter runs conducted at medium-compression ratios between 15 and 40% and filtration rates from 410 to 820 L/m2 min. The difference between the observed and the predicted values was found to be within 0 to 15%.     

Effects of aquatic humic substances on a hydrophobic ultrafiltration membrane

Natural humic surface water (pH 5.9), ion exchanged samples of the same water (pH 5.5), and aqueous solutions of isolated humic substances at pH 4.5, 5.5 and 6.5, respectively, were ultrafiltered (15°C, 0.5 bar) using hydrophobic polysulfone membranes (GR51) in a cross-flow flat sheet module. The used membrane did not completely retain natural organic matter from the surface water and the addition of complexing metals did not affect the retention any further. The changes which were induced in the membranes during each filtration run were studied by simultaneous streaming potential and flux measurements in 0.01 M KCl solutions. Zeta potentials were calculated based on the streaming potentials and the results showed changes towards more negative values for all the samples due to adsorption of organic matter onto the surface of the membrane pores. Humic acid affected the membrane charges more than fulvic acid. High ionic strength and low pH enhanced flux reduction and fouling. Filtration of natural waters caused more pore plugging and flux reduction than filtration of solutions of the isolated humic substances.     

滤袋数目对翼形上进风袋式除尘器内流场影响的数值模拟研究

针对实际运行过程中,袋式除尘器滤袋使用寿命短,压力损失过大的问题,本文以翼形上进风袋式除尘器为研究对象,采用CFD(computational fluid dynamics)技术模拟分析不同滤袋数(分别为92、88、84、80、76和72)时袋式除尘器内气流分布和压力损失规律。主要考察了流量分配系数、最大流量不均幅值、气流迹线、滤袋表面速度分布与压降等指标。结果表明,滤袋数为76个时,气流分布最为均匀,各滤袋负载均衡;相同过滤速度下,装置的压降随滤袋数目的增加而上升,即压降大小顺序为9288847672;与72个滤袋相比,76个滤袋的可用过滤面积更大。综合考虑,袋式除尘器的最优滤袋数目为76个。模拟结果为袋式除尘器的设计和优化提供了依据。     

活性炭柱中砂垫层在微污染水源水处理工艺中的应用

以嘉兴市某水厂沉后水为进水进行实验,研究炭砂滤池对污染物的去除性能,以及炭砂滤池取代活性炭＋砂滤池的可能性,探讨了短流程工艺的适用性。结果表明,炭砂滤池能有效去除水中的浊度、氨氮、CODMn和铁、锰等污染物,与活性炭柱相比,炭砂滤池在降低出水浊度和水中颗粒数方面具有一定优势,即砂垫层对控制出水浊度和保障微生物安全能够起到积极作用。在实验条件下,增加活性炭层厚度或者降低滤速,在一定程度上有利于提高对CODMn的去除率。在设计滤速为9～10 m/h,CODMn〈4.5 mg/L时,可直接以炭砂滤池取代活性炭池＋砂滤池,仍然能保证出水CODMn〈3 mg/L。     

The impact of recirculation,ventilation and filters on secondary organic aerosols generated by indoor chemistry

This study examined the impact of recirculation rates (7 and 14 h^?1), ventilation rates (1 and 2 h^?1), and filtration on secondary organic aerosols (SOAs) generated by ozone of outdoor origin reacting with limonene of indoor origin. Experiments were conducted within a recirculating air handling system that serviced an unoccupied, 236 m³ environmental chamber configured to simulate an office; either no filter, a new filter or a used filter was located downstream of where outdoor air mixed with return air. For otherwise comparable conditions, the SOA number and mass concentrations at a recirculation rate of 14 h^?1 were significantly smaller than at a recirculation rate of 7 h^?1. This was due primarily to lower ozone concentrations, resulting from increased surface removal, at the higher recirculation rate. Increased ventilation increased outdoor-to-indoor transport of ozone, but this was more than offset by the increased dilution of SOA derived from ozone-initiated chemistry. The presence of a particle filter (new or used) strikingly lowered SOA number and mass concentrations compared with conditions when no filter was present. Even though the particle filter in this study had only 35% single-pass removal efficiency for 100 nm particles, filtration efficiency was greatly amplified by recirculation. SOA particle levels were reduced to an even greater extent when an activated carbon filter was in the system, due to ozone removal by the carbon filter. These findings improve our understanding of the influence of commonly employed energy saving procedures on occupant exposures to ozone and ozone-derived SOA.     

The Petroleum Refining Industry—Air Pollution Problems and Control Methods

Polyurethane foam was incorporated as a prefilter on standard hi-volume samplers of the National Air Sampling Network (NASN) in an exploratory study. The foam selectively filtered particles of various sizes. The characteristics of the particles passing through the foam approached the respirable size fraction as defined by reports of the Atomic Energy Commission. The respirable fraction was then collected on a glass-fiber filter. Parameters such as pore size and thickness of the foam, air flow rates, and loadings were studied to determine their effects on the filtration of “respirable” dust. Ambient air was the particulate source, and sizing was accomplished by an Andersen sampler coupled with nephelometric analyses. Some sizing was also done microscopically. The foam was evaluated at several locations to account for possible variations in ambient air over areas of different industrial complexity.