Predicting Cutoff Aerodynamic Diameter and Sharpness of Single Round-Nozzle Impactors with a Finite Impaction Plate Diameter

Abstract

This investigation numerically examined the cutoff aerodynamic diameter (da₅₀) and the sharpness (GSD) of the particle collection efficiency curve of impactors with a finite impaction plate diameter. Results revealed that the inertial impactors have a limited cutoff aerodynamic diameter at different air velocities. The extreme value of the cutoff aerodynamic diameter increases with the nozzle diameter (W)/the plate diameter (D_c). The computed da₅₀/D_c values of the impactors increase with W/D_c at various Reynolds numbers (Re) and with the nozzle-toplate distance (S)/D_c when Re is 100. The value of GSD slightly increases with W/D_c for Re of 10 and 100, although the effect of S/D_c on GSD is not evident at various Res. The particle collection efficiency curve of the impactor with a lower Re is less sharp than that with a high Re at various W/D_c and S/D_c values. Statistical equations closely fitted the obtained numerical results for Res of 10–3000. The equations are useful for directly calculating the cutoff aerodynamic diameter and the sharpness of the particle collection efficiency curve for single round-nozzle impactors with a finite impaction D_c.     

微污染水源水净化新技术

介绍了近年来出现的纳滤膜,预臭氧化及新型生物反应器（膜生物反应器和电生物反应器）处理微污染水源水的最新技术动态。对相关机理进行了归纳总结。     

Partitioning and removal of dioxin-like congeners in flue gases treated with activated carbon adsorption

Activated carbon adsorption is commonly used to control dioxin-like congener (PCDD/Fs and PCBs) emissions. Partitioning of PCDD/Fs and PCBs between vapor and solid phases and their removal efficiencies achieved with existing air pollution control devices (APCDs) at a large-scale municipal waste incinerator (MWI) and an industrial waste incinerator (IWI) are evaluated via intensive stack sampling and analysis. Those two facilities investigated are equipped with activated carbon injection (ACI) with bag filter (BF) and fixed activated carbon bed (FACB) as major PCDD/F control devices, respectively. Average PCDD/F and PCB concentrations of stack gas with ACI+BF as APCDs are 0.031 and 0.006ng-TEQ/Nm(3), and that achieved with FACB are 1.74 and 0.19ng-TEQ/Nm(3) in MWI and IWI, respectively. The results show that FACB could reduce vapor-phase PCDD/Fs and PCBs concentrations in flue gas, while the ACI+BF can effectively adsorb the vapor-phase dioxin-like congener and collect the solid-phase PCDD/Fs and PCBs in the meantime. Additionally, the results of the pilot-scale adsorption system (PAS) experimentation indicate that each gram activated carbon adsorbs 105-115ng-PCDD/Fs and each surface area (m(2)) of activated carbon adsorbs 10-25ng-PCDD/Fs. Based on the results of PAS experimentation, this study confirms that the surface area of mesopore+macropore (20-200A) of the activated carbon is a critical factor affecting PCDD/F adsorption capacity.     

Modeling solute transport in one-dimensional homogeneous and heterogeneous soil columns with continuous time random walk

In this paper, we used the continuous time random walk (CTRW) framework to characterize the transport process in 1250-cm long one-dimensional homogenous and heterogeneous soil columns at the experiments conducted by Huang et al. [Huang, K., Toride, N., van Genuchten, M.Th., 1995. Experimental investigation of solute transport in large, homogeneous and heterogeneous, saturated soil columns. Trans. Porous Media. 18, 283-302]. The transport process was also simulated by using the advection-dispersion equation (ADE) and the spatial fractional advection-dispersion equation (FADE) for comparison. In the homogeneous soil column, the non-Fickian behavior is found at the distances less than 1000cm with beta values larger than 1.60, but less than 2, and Fickian form transport is obtained at distances larger than 1000cm with beta values larger than 2. In the heterogeneous soil column, we found the most anomalous behavior at distances from 200cm to 700cm with beta values ranging from 0.894 to 0.958, and non-Fickian transport process is observed at distances larger than 800cm with beta values in the range between 1 and 1.3. More significant non-Fickian behavior is found for transport in the heterogeneous soil column than that in the homogeneous soil column. The CTRW fits to the breakthrough curves (BTCs) have lower values of root mean square error (RMSE) and higher values of determination coefficient (r(2)), with respect to the fits of ADE and FADE. The CTRW model also is better captures the full evolution of BTCs, and especially their tails.     

工业循环经济发展区域分异研究--以江苏省为例

依据工业循环经济发展的基本原则,构建了包括产业及社会发展、资源减量、循环利用、污染减排、资源与环境安全五类指标在内的区域工业循环经济发展评价指标体系.运用AHP(层次分析法)方法,测算了指标权重,并以江苏省13个地级市为例进行了研究.用2003年的数据,对13个地级市的工业循环经济发展状况进行了评价.研究结果表明,江苏省13个地级市的工业循环经济发展水平可以分为四个层次,第一层次(水平良好)的城市为无锡、苏州、常州;第二层次(水平中上)的城市为盐城、南通、泰州;第三层次(水平中等)的城市为扬州、镇江、徐州、南京、连云港;第四层次(水平较差)的城市为淮安、宿迁.从总体上看,南部好于北部,东部好于西部,沿江沿海地区要好于内陆地区,靠近工业产业带的地区好于远离工业产业带的地区.     

日本二噁英减排控制的历程、经验与启示

二噁英减排控制是《关于持久性有机污染物的斯德哥尔摩公约》的重要任务,是履行公约义务的难点.对日本二噁英减排控制20年来的实践历程进行了回顾和分析,总结出了其协调管理机制设立、法律法规标准建立、监测能力建设以及宣传教育等八个方面的成功经验,对中国二噁英减排控制工作有重要的借鉴意义.     

人工湿地处理系统中多环芳烃的行为

采用Oasis HLB柱固相萃取的前处理技术,以气相色谱质谱联用仪(GC/MS)的分析方法,对我国北方永定河上游黑土洼人工湿地中多环芳烃污染的特征以及分布规律进行了研究.结果表明,该湿地系统以低环数多环芳烃污染为主,其中浓度最高的是菲和蒽,未检出高环数(5环、6环)多环芳烃.通过比较进水和出水的浓度,湿地系统总体上不能有效去除进水中的多环芳烃.但是比较不同工艺单元进出水浓度,复氧、植物根系及微生物等均影响到多环芳烃的去除效果,去除率在28%～65%之间.     

曝气生物滤池处理焦化废水脱氮的研究

用曝气生物滤池处理焦化废水的研究表明,在曝气量(Q)=0.25L/min,温度(T)=20℃,pH=8,反冲洗周期为3个运行周期内,NH3-N的去除速率达44 mg/L·h.同时在滤池中出现了亚硝酸盐积累现象,且受反冲洗的影响较大.     

微波辅助空气氧化水溶液中的PCP

采用活性炭为催化剂,对微波辅助空气氧化水溶液中的五氯酚进行了处理研究.考察了活性炭投加量、微波功率、辐射时间和通气量对溶液中五氯酚的去除率的影响.结果表明,在通气量为0.2 L/min,微波功率800 W和微波辐射60 min时,五氯酚的去除率可达到90%以上;对微波辐射前后的滤液进行紫外扫描和pH分析,可证实五氯酚被降解.     

Effect of arsenic on chloroplast ultrastructure and calcium distribution in arsenic hyperaccumulator Pteris vittata L

This study investigated the impacts of arsenic (As) on the chloroplast ultrastructure and calcium (Ca) distribution in Chinese brake (Pteris vittata L.) mainly by histochemical methods, with an emphasis on the possible function of Ca in As detoxification and accumulation in P. vittata. P. vittata was grown in an artificially contaminated soil added with different concentrations of Na(2)HAsO(4) (0, 100, 300 and 800 mg kg(-1) As dry soil) for 24 weeks in a greenhouse. The addition of As did not affect the chloroplast ultrastructure of young pinna, meanwhile most of the membrane systems of chloroplasts in mature pinna were severely damaged under high As condition. Calcium concentration in the fronds of P. vittata was not significantly affected by the addition of As, but Ca concentration in the mature pinna significantly increased by As addition, consistent with the position appearing As toxicity. When no As was added, most of calcium precipitates distributed around the inner membrane of vacuole. But when the pinna appeared plasmolysis, more calcium precipitates resided outside the cell membrane and bigger particles evenly distributed in the cytoplasm. All the results indicated that Ca had a close relation with As toxicity in P. vittata.