An experimental-computational study of DPF soot capture and heat regeneration

ABSTRACT

A diesel particulate filter (DPF) can effectively reduce the exhaust emissions of particulate matter (PM) and meet emission regulations. We report herein an experimental-numerical study to investigate the soot capture and regeneration behavior in a commonly used DPF. Simulations are performed using the AVL FIRE software that considers a fairly detailed DPF model. The model is validated using measured pressure drop history during soot capture, and temperature history during regeneration from a parallel experimental study using a diesel engine equipped with a DPF. Then, a detailed numerical study is performed to examine the soot capture and heat regeneration processes, and characterize the effects of various parameters on these processes and on DPF performance. Results indicate that the pressure drop during soot loading can be reduced by increasing the CPSI (channels per square inch), minimizing the amount of residual soot in each regeneration cycle, and using moderate gas flow rates. The DPF regeneration performance is characterized in terms of the rates of temperature rise and soot oxidation. Results indicate that these rates are enhanced, as the oxygen content in the exhaust stream is increased to about 12%, the rate of thermal heating is moderately increased, and as the exhaust gas flow rate is increased. Thus, the regeneration efficiency can be significantly improving by optimizing these parameters.     

Tertiary treatment of municipal wastewater using isolated algal strains: treatment efficiency and value-added products recovery

ABSTRACT

Two microalgal strains (Chlorella sorokiniana, A&B,) grown optimally at pH 9 (A) and 7 (B) were isolated from a municipal wastewater treatment plant. These strains were used to check their efficacy for nutrients and organic carbon removal capacities from the tertiary wastewater. The strains were characterised using 18S rDNA sequencing method and both the strains closely related to Chlorella sorokiniana. Different inoculum doses (IDs) of both the strains were tried to check their efficacy on wastewater treatment. Due to the increase in the IDs, hydraulic retention time decreased from 6 d to 1?d. On an average, 12–100% of total kjeldahl nitrogen, 53–96% NO₃–N, and 59–92% PO₄–P, were removed. Despite the same growth environment, strain A with the highest ID (700?mg/L) showed the best performance in terms of overall organic carbon removal, nutrient removal, and value-added products recovery. Strain A showed an increase in carbohydrate and protein content by 42% and 13%, respectively. Both the strains showed luxury phosphorus uptake and found suitable for advanced wastewater treatment.     

Mercury exposure in the freshwater tilapia Oreochromis niloticus

Mercury (Hg) can be strongly accumulated and biomagnified along aquatic food chain, but the exposure pathway remains little studied. In this study, we quantified the uptake and elimination of both inorganic mercury [as Hg(II)] and methylmercury (as MeHg) in an important farmed freshwater fish, the tilapia Oreochromis niloticus, using ²⁰³Hg radiotracer technique. The dissolved uptake rates of both mercury species increased linearly with Hg concentration (tested at ng/L levels), and the uptake rate constant of MeHg was 4 times higher than that of Hg(II). Dissolved uptake of mercury was highly dependent on the water pH and dissolved organic carbon concentration. The dietborne assimilation efficiency of MeHg was 3.7-7.2 times higher than that of Hg(II), while the efflux rate constant of MeHg was 7.1 times lower. The biokinetic modeling results showed that MeHg was the greater contributor to the overall mercury bioaccumulation and dietary exposure was the predominant pathway.     

Fabrication, calibration and evaluation of a phosphate ion-selective microelectrode

To conduct the micro-environment study of flocs in an enhanced biological phosphorus removal (EBPR) process, a phosphate ion-selective microelectrode was developed. The cobalt-based microelectrodes have tip diameters of 5-20 μm and respond to all the three forms of phosphate ions, namely, H₂PO₄⁻, HPO₄²⁻, and PO₄³⁻. The calibration curve at pH 7.5 had a slope of 31.5 mV per decade change of concentration and a R² value of 0.99. Other characteristics of this microelectrode, such as response time, interferences from pH, ion strength, DO and other anions were also evaluated.     

企业绿色供应链管理实践的阶段性及其特征研究

本文在总结绿色供应链管理(GSCM)的现有研究成果与实践经验的基础上,提出可将企业在推进GSCM的实践划分为4个阶段:生存需求阶段、初步合作阶段、源头绿色化阶段、自我价值实现阶段。设计了调查问卷,对165家国内企业在推进GSCM的实践情况进行了调研。研究结果表明:这些企业在GSCM方面尚处于初级阶段,具体表现为由"消极应对"向"有所策划和初步实践"过渡;这一阶段的主要实施手段包括"回收利用生产过程中产生的废料"、"要求供应商提供清洁环保的产品"、"为消费者提供产品相关的环境信息"、"推进清洁生产审核"等。通过该实证研究以期为政府有关部门制定促进可持续发展的相关政策提供参考。     

The use of a lacertid lizard as a model for reptile ecotoxicology studies--part 1 field demographics and morphology

At the European level, lacertid lizards have been proposed as potential model species for reptile ecotoxicology. We studied demographic and morphological aspects of natural field subpopulations of Podarcis bocagei inhabiting similar agricultural habitats which were either regularly exposed to pesticides, or not. Parameters examined in this study included population size and density, sex ratio, adult body size, fluctuating asymmetry in femoral pores and parasite prevalence. In general, we detected few statistically significant differences between the exposed and reference subpopulations. Although field situations are ecologically complex and factors other than pesticides may be acting, the absence of observable effects on field subpopulations is probably indicative that lizards are coping or compensating for this level of exposure.     

±660kV交流滤波器高压电容塔调平

基于ABAQUS软件建立了标准升温条件下局部填充混凝土(Partially Encaed Concrete,简称PEC)柱抗火性能分析的有限元模型,计算了火灾下PEC柱的变形曲线及耐火极限,计算结果得到了已有试验数据的验证。利用上述模型分析了截面几何参数、材料物理参数、荷载比及偏心率等因素对耐火极限的影响。在参数分析的基础上,建立了标准升温条件下PEC耐火极限简化计算方法。结果表明:无耐火保护PEC柱的耐火极限一般达不到现有抗火标准的要求;荷栽比、长细比和截面周长是影响PEC柱耐火极限的主要因素;该耐火极限简化计算方法可供工程设计参考。     

区域科学发展不同评价体系比较研究

构建区域科学发展评价体系需要解决区域发展要素协同演化的综合测度问题,通过利益统筹引导区域资源和谐配置.现有不同评价体系在设计原理、指标构成、数据处理与权重分配方面具有差异性.但评价结果具有相似性.它们的共性之处在于:以五个统筹为基础,逻辑主线是调解人与人之间、人与自然之间的矛盾;大多采用层次分析法和模糊数学法,不能反映出指标之间的包含关系、相关关系以及逻辑关系,可能导致具有高度相关性的指标被重复使用;仅适台一般区域评价,不适合特定区域评价;评价方法较为单一、评价指标设置过多、以人为本的思想尚未充分体现.本文提出了进一步的研究内容:以实现包容性增长为目标构建区域发展要素资本体系;指标的内在逻辑关系围绕经济学模式、社会学模式、生态学模式展开;并将区域可比性、区域特殊性、区域层次性、发展潜力性、指标前瞻性等纳入评价体系的范畴.     

我国城镇污水处理厂水质监管问题及对策研究

介绍了目前我国城镇污水处理厂的发展现状以及将其作为污染源纳入监管的背景;从进水水质监管、出水水质监管和对污水处理厂内部运营管理监管的角度,结合对部分地区行政管理部门、污水处理厂的调研,分析了污水处理厂出水水质不达标的主要原因;针对我国的实际情况并借鉴国外经验,从政府部门的监管职能、政企的合作、监管技术和末端污染控制方面,给出了加强污水处理厂运行监管效果的对策。     

基于工作过程的高职“教学做一体化”课程探究

“教学做一体化”课程有利于理论教学与实践教学相结合,有利于高职学校长期健康的发展。“教学做一体化”教学模式是基于实际工作过程导向,以工作中典型项目任务引领,激发学生兴趣,以满足培养高等技能型人才的迫切需要。一体化课程的构建应通过项目设立、建立小组、实施、反馈等环节完成。