新型离心式脱硫塔气液两相流数值模拟

利用FLUENT软件和SIMPLE算法对新型旋流脱硫塔的气液两相流场进行了数值模拟。计算中气相采用了RSM湍流模型,颗粒相采用了Lagrange坐标系下的随机轨道模型。分析结果表明,气相流场具有强旋流特性;喷射液滴的直径、喷淋量和烟气流速影响其在塔内的分布:喷射液滴粒径越大、喷射量越小、烟气流速越大,入口段降温越少;塔体上方截面平均浓度随液滴粒径的增加而降低,随液气比的增加而增加,随烟气流速的增加会先增加至最高值然后降低。喷淋液滴在其他运行参数不变时,平均粒径范围为0.5～1 mm,会对进口烟气起到较好的净化与降温的作用,并使塔体上方喷淋液滴在截面z=4.15 m处浓度分布均匀且覆盖率高;在保证液滴粒径较小时,通过降低烟气流速或增加喷淋量可提高液滴喷淋覆盖率,使得烟气与喷淋充分接触。计算得到的气相流场分布与实测值吻合较好,证明了数学模型的合理性,为进一步优化分离器结构提供了可靠依据。     

废水液滴在低温烟气中的蒸发特性数值研究

建立了液滴在低温低速烟气中运动和蒸发的数学模型,数值研究了液滴在不同的烟气速度和烟气温度环境中的蒸发特性,获得了液滴速度、温度和直径随时间的变化规律,以及烟气速度和温度对液滴蒸发特性的影响。计算结果表明：气相速度越大,液滴初速度对液滴运动速度的影响越小,液滴速度越容易达到烟气速度。对于初始直径和速度一定的液滴,气液初始相对速度越大,液滴达到临界蒸发温度所需的时间越短,完全蒸发时间也越短。在文中研究的烟气速度范围内,整体上气相速度的改变对液滴完全蒸发时间的影响很小。气相温度的改变对液滴达到临界蒸发温度的时间以及完全蒸发时间的影响很大。烟气从较高温度和较低温度分别下降相同幅度的温度时,液滴在烟气中的完全蒸发时间按不同的倍数在增加,烟气温度越低,液滴完全蒸发时间增加的越多。对于文中研究的液滴,无量纲完全蒸发时间随烟气温度变化呈指数递减规律。     

城市生活垃圾在机械炉排炉内焚烧过程研究及数值模拟

研究城市生活垃圾在机械炉排炉内焚烧过程,建立了垃圾在炉排炉移动床内燃烧过程中垃圾体积变化、水分蒸发、挥发分析出及燃烧、垃圾颗粒的移动、气-固两相热传递、焦炭燃烧等各个反应阶段的热化学模型,采用一维非稳态模型分别建立了床层内气固两相介质控制方程。通过对炉排上垃圾焚烧过程的数值模拟研究,获得料层中温度分布、料层高度、炉床机械负荷、气相中反应物组分和污染物浓度分布。利用建立的模型对某大型垃圾焚烧炉的燃烧过程进行数值仿真,对燃烧过程、烟气成分进行预测,为垃圾焚烧炉排炉的设计和燃烧控制提供理论依据。     

静电除尘器内细微尘涡流现象的数值模拟

基于计算流体力学,以ANSYS软件中的FLUENT模块为平台模拟了粉尘粒径、烟气流速、电晕极电压和烟气含尘浓度对静电除尘器内细微尘涡流现象的影响。研究表明：随着粉尘粒径和烟气流速的增大,颗粒在静电除尘器内的合速度增大,粒子突破空气阻力维持原方向运动的能力增强,涡流的强度降低;随着电晕极电压和在一定范围内烟气含尘浓度的增加,高速流体区域与低速流体区域的速度差增大,涡流的强度会随之增加;继续增大烟气含尘浓度,导致静电除尘器内出现电晕封闭现象,"电风"逐步减弱,电场力大幅减小,粒子跟随烟气流出静电除尘器,涡流被大幅削弱或消失。根据以上规律,以相对均方根值为指标设计L9（34）正交模拟,得出各因素对涡流影响程度由高到低分别为烟气流速、电晕极电压、含尘浓度、粉尘粒径。     

喷射量对预混合丁醇/柴油复合燃烧排放的影响

基于一台轻型高压共轨柴油机增加一套低压共轨系统实现气道定差压丁醇喷射,并控制进气温度不低于110 ℃以形成均质预混合气。研究了3 350 r·min-1不同负荷条件下小比例丁醇喷射量对柴油机的气体排放物和颗粒物排放数量浓度、质量浓度及颗粒数量浓度粒径分布特性的影响。结果表明,在中小负荷范围内的HC和CO排放随丁醇喷射量几乎呈线性增加;在大负荷HC排放增加,但是CO排放略微减小。在小负荷工况soot质量比排放和NOx排放随丁醇喷射量增大而降低,不存在折衷关系;在中大负荷工况soot质量比排放随丁醇喷射量增大而降低但NOx排放随丁醇喷射量增大而升高。丁醇可明显降低各个负荷的大粒径颗粒物的数量浓度,但是会增加小粒径颗粒的数量浓度。丁醇可降低各个负荷下颗粒物的总数浓度。     

硅钙渣用于烟气脱硫的可行性

根据硅钙渣的化学成分、物相组成和粒径分布分析了其用于烟气脱硫的可行性,并进行了模拟烟气脱硫实验,结果表明,硅钙渣中含有大量的碱性氧化物,且粒径分布满足脱硫要求;其浆液脱硫效率高,脱硫持续时间长,而且还能较好地适应烟气中SO_2浓度的变化。当浆液浓度从1%增加到7%,脱硫效率为100%的持续时间从275 min增加到1 900 min。在相同条件下,硅钙渣的脱硫性能优于石灰石,因此,硅钙渣用于烟气脱硫是可行的。     

基于分区气化模型的MSW燃烧过程模拟研究

针对一种新型两段式生活垃圾分区气化燃烧装置,提出了基于分区气化模型的垃圾热转化过程数值模拟方法。该方法耦合化学反应动力学和流体动力学软件预测移动床层垃圾的气化以及炉内气相空间的燃烧过程。通过对组分及热值差异较大的2种生活垃圾在炉内的反应过程进行模拟,得到了炉内的气相组分、温度及流场的分布。结果表明,该方法能够很好地适用于复杂组分的垃圾热转化过程模拟研究。高水分、低热值的生活垃圾气化后再燃炉膛出口温度处于973~1 073 K,不利于二恶英的生成控制。前拱二次风的增加不仅加强了炉内的湍流扰动,而且加强了炉内主反应区的温度。经过对流场和温度场进行优化,烟气的停留时间延长,炉膛出口烟气中的可燃气体组分大大降低,而且NO的浓度降低了近一个数量级。     

燃煤电站湿法烟气脱硫的颗粒物脱除效果

伴随着我国燃煤电站污染物严峻形势,湿法烟气脱硫协同捕集颗粒物越来越受到工程应用部门的重视。从基本理论出发,引入捕集体与颗粒碰撞、拦截与扩散的基本方程,推导并建立多液滴对多颗粒的捕集模型。研究结果表明：直径245 μm的液滴,沉降速度小于气流速度,会被携带出脱硫塔;液滴对PM0.1、PM1、PM2.5、PM5、PM10颗粒物的去除效率为U型曲线,910 μm液滴对颗粒物的去除效率比4 666 μm液滴高近百倍;同等质量浓度,不同粒度分布,脱硫塔除尘性能仍然差异较大。     

高活性脱硫剂增湿脱硫过程的数值模拟

对增湿脱硫实验装置进行了数值模拟研究,详细了解反应器内的三相流动、碰撞和蒸发过程,依据流体动力学原理,将气相和脱硫剂颗粒作为连续介质和拟流体,以在欧拉坐标系中描述,将水滴作为离散相,以在拉格朗日坐标系中描述,建立质量、动量、能量和湍动能耗散的输运方程及液滴蒸发、碰撞、运动方程,分别计算气体和液滴轴向速度、反应器内温度的径向分布,其液滴轴向质量浓度、脱硫剂捕集效率,计算数据与试验值吻合较好。     

二次风喷嘴角度对炉排式垃圾焚烧炉内燃烧及选择性非催化还原脱硝的影响

利用CFD技术,对某城市处理量为750 t·d-1的垃圾焚烧炉内燃烧与选择性非催化还原脱硝（SNCR）过程进行建模分析,重点研究了二次风喷嘴角度的改变对焚烧炉内燃烧温度场的影响及其对提高SNCR脱硝效率的作用。模拟结果表明,焚烧炉二次风喷嘴角度调整为相互交叉45°,可以改善炉内燃烧状况,促进炉膛内烟气与空气的混合,使炉膛内温度场分布均匀,有利于SNCR还原反应;二次风喷嘴角度改变后,在一定程度上保证了SNCR系统喷入的尿素液滴在炉膛内的停留时间。与平行二次风相比,使用交叉二次风送风方案,前墙喷嘴脱硝效率提高4.8%,后墙喷嘴脱硝效率提高了19.7%。     

Sorption and desorption of Cu and Cd by macroalgae and microalgae

The sorption and desorption of Cu and Cd by two species of brown macroalgae and five species of microalgae were studied. The two brown macroalgae, Laminaria japonica and Sargassum kjellmanianum, were found to have high capacities at pHs between 4.0 and 5.0 while for microalgae, optimum pH lay at 6.7. The presence of other cations in solution was found to reduce the sorption of the target cation, suggesting a competition for sorption sites on organisms. Sorption isotherms obeyed the Freundlich equation, suggesting involvement of a multiplicity of mechanisms and sorption sites. For the microalgae tested, Spirulina platensis had the highest capacity for Cd, followed by Nannochloropsis oculata, Phaeodactylum tricornutum, Platymonas cordifolia and Chaetoceros minutissimus. The reversibility of metal sorption by macroalgae was examined and the results show that both HCl and EDTA solutions were very effective in desorbing sorbed metal ions from macroalgae, with up to 99.5% of metals being recovered. The regenerated biomass showed undiminished sorption performance for the two metals studied, suggesting the potential of such material for use in water and wastewater treatment.     

Kinetic and structural relationships of transition monomeric and oligomeric carboxyl- and choline-esterases

The kinetic and structural relationships of eight electrophoretically pure mammalian serum and liver serine carboxylesterases (CE) and cholinesterases (ChE) have been studied. Eight CE's and ChE's, which were fully resolved but only partially purified, provided additional information. Five of the electrophoretically pure esterases were monomeric, and of these, four belonged to a new and widely distributed class. These four monomeric esterases hydrolyzed choline esters, but at widely differing rates. Thus two were termed monomeric butyrylcholinesterases, mBuChE I and II, and two were monomeric CE's (mCE). The rabbit liver mCE was not a subunit of the oligomeric CE (oCE), although the oCE also hydrolyzed choline esters at a very low rate. The complex kinetics of the mCE's, mBuChE's, oCE's, and of the oligomeric BuChE's of horse and human serum could be interpreted according to a single reaction scheme involving an allosteric site and the equation derived from it. Thus activation and inhibition at high substrate concentrations, together with sigmoidal activity versus substrate concentration plots, all of which characterize the reactions of these esterases, could be interpreted by a single scheme and equation. Structural and kinetic comparisons showed a progressive transition of properties from the oCE's through the mCE's to the oBuChE's. One of the purified mCE's was from horse serum, and it exhibited physical and kinetic properties unlike those of the liver mCE's or oCE's.     

Persistence and dissipation kinetics of trifloxystrobin and tebuconazole in onion and soil

The persistence and dissipation kinetics of trifloxystrobin and tebuconazole on onion were studied after application of their combination formulation at a standard and double dose of 75 + 150 and 150 + 300 g a.i. ha^?1. The fungicides were extracted with acetone, cleaned-up using activated charcoal (trifloxystrobin) and neutral alumina (tebuconazole). Analysis was carried out by gas chromatograph (GC) and confirmed by gas chromatograph mass spectrometry (GC-MS). The recovery was above 80% and limit of quantification (LOQ) 0.05 mg kg^?1 for both fungicides. Initial residue deposits of trifloxystrobin were 0.68 and 1.01 mg kg^?1 and tebuconazole 0.673 and 1.95 mg kg^?1 from standard and double dose treatments, respectively. Dissipation of the fungicides followed first-order kinetics and the half life of degradation was 6–6.6 days. Matured onion bulb (and field soil) harvested after 30 days was free from fungicide residues. These findings suggest recommended safe pre-harvest interval (PHI) of 14 and 25 days for spring onion consumption after treatment of Nativo 75 WG at the standard and double doses, respectively. Matured onion bulbs at harvest were free from fungicide residues.     

Sorption and Desorption Behavior of Chloroanilines and Chlorophenols on Montmorillonite and Kaolinite

The bioavailability of pollutants, pesticides and/or their degradation products in soil depends on the strength of their sorption by the different soil components, particularly by the clay minerals. This study reports the sorption-desorption behavior of the environmentally hazardous industrial pollutants and certain pesticides degradation products, 3-chloroaniline, 3,4-dichloroaniline, 2,4,6-trichloroaniline, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol on the reference clays kaolinite KGa-1 and Na-montmorillonite SWy-l. In batch studies, 2.0 g of clay were equilibrated with 100.0 mL solutions of each chemical at concentrations ranging from 10.0 to 200.0 mg/L. The uptake of the compounds was deduced from the results of HPLC-UV-Vis analysis. The lipophilic species were best retained by both clay materials. The most lipophilic chemical used in the study, 2,4,6-trichloroaniline, was also the most strongly retained, with sorption of up to 8 mg/g. In desorption experiments, which also relied on HPLC-UV-Vis technique, 2,4,6-trichloroaniline was the least desorbed from montmorillonite. However, on kaolinite all of the compounds under study were irreversibly retained. The experimental data have been modelled according to the Langmuir and Freundlich isotherms. A hypothesis is proposed concerning the sorption mechanism and potential applications of the findings in remediation strategies have been suggested.     

Sorption and desorption behavior of chloroanilines and chlorophenols on montmorillonite and kaolinite

The bioavailability of pollutants, pesticides and/or their degradation products in soil depends on the strength of their sorption by the different soil components, particularly by the clay minerals. This study reports the sorption-desorption behavior of the environmentally hazardous industrial pollutants and certain pesticides degradation products, 3-chloroaniline, 3,4-dichloroaniline, 2,4,6-trichloroaniline, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol on the reference clays kaolinite KGa-1 and Na-montmorillonite SWy-l. In batch studies, 2.0 g of clay were equilibrated with 100.0 mL solutions of each chemical at concentrations ranging from 10.0 to 200.0 mg/L. The uptake of the compounds was deduced from the results of HPLC-UV-Vis analysis. The lipophilic species were best retained by both clay materials. The most lipophilic chemical used in the study, 2,4,6-trichloroaniline, was also the most strongly retained, with sorption of up to 8 mg/g. In desorption experiments, which also relied on HPLC-UV-Vis technique, 2,4,6-trichloroaniline was the least desorbed from montmorillonite. However, on kaolinite all of the compounds under study were irreversibly retained. The experimental data have been modelled according to the Langmuir and Freundlich isotherms. A hypothesis is proposed concerning the sorption mechanism and potential applications of the findings in remediation strategies have been suggested.     

Bacterial and archaeal diversity in oil fields and reservoirs and their potential role in hydrocarbon recovery and bioprospecting

Environmental Science and Pollution Research - Hydrocarbon is a primary source of energy in the current urbanized society. Considering the increasing demand, worldwide oil productions are declining...     

畜禽养殖业污染与循环经济

解决畜禽养殖业的污染问题要以充分利用资源为根本出发点，通过对污染全过程控制及废物综合利用，达到畜禽粪便的减量化、无害化、资源化，走循环经济的发展道路。     

Degradation in soil and water and ecotoxicity of rimsulfuron and its metabolites.

The degradation and ecotoxicity of sulfonylurea herbicide rimsulfuron and its major metabolites were examined in batch samples of an alluvial sandy loam and in freshwater. An HPLC-DAD method was adapted to simultaneously identify and quantify rimsulfuron and its metabolites, which was successfully validated by GC-MS analysis. In aqueous solutions, pure rimsulfuron was rapidly hydrolyzed into metabolite 1 (N-(4,6-dimethoxypyrimidin-2-yl)-N-(3-(ethylsulfonyl)-2-pyridinylurea)), which itself was transformed into the more stable metabolite 2 (N-((3-(ethylsulfonyl)-2-pyridinyl)-4,6-dimethoxy-2-pyrimidineamine)), with half-life (t(1/2)) values of 2 and 2.5 days, respectively. Hydrolysis was instantaneous under alkaline conditions (pH = 10). In aqueous suspensions of the alluvial soil (pH = 8), formulated rimsulfuron had a half-life of 7 days, whereas that of metabolite 1 was similar to that in water (about 3.5 days). The degradation of the two major metabolites was also studied in soil suspensions with the pure compounds at concentrations ranging from 1 to 10 mg l(-1). The half-life of metabolite 1 ranged from 3.9 to 5 days, close to the previous values. Metabolite 2 was more persistent and its degradation is strongly dependent on the initial concentration (C0): half-life values ranged from 8.1 to 55 days at 2-10 mg l(-1), respectively. These values are higher than those determined from the kinetics of metabolite 1 transformation into metabolite 2 (t(1/2) = 8-19 days). The ecotoxicity of the three chemicals was evaluated through their effect on Daphnia magna and Vibrio fischeri (Microtox bioassay). No effect was observed on D. magna with 24 and 48 h acute toxicity tests. Similarly, no toxic effect was observed with the Microtox test for the three chemicals in the range of concentrations tested that included the field application dose. Thus, being of low persistence and lacking acute toxicity, these chemicals present a low environmental risk. However, chronic effects should be studied in order to confirm the safety of rimsulfuron and its major metabolites.     

Isocyanatocyclohexane and isothiocyanatocyclohexane levels in urban and industrial areas and possible emission-related activities

Isocyanatocyclohexane and isothiocyanatocyclohexane are becoming relevant compounds in urban and industrial air, as they are used in important amounts in automobile industry and building insulation, as well as in the manufacture of foams, rubber, paints and varnishes. Glass multi-sorbent tubes (Carbotrap, Carbopack, Carboxen) were connected to LCMA-UPC pump samplers for the retention of iso- and isothiocyanatocyclohexanes. The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detector (MSD). TD-GC/MS was chosen as analytical method due to its versatility and the possibility of analysis of a wide range of volatility and polarity VOC in air samples. The method was satisfactory sensitive, selective and reproducible for the studied compounds. The concentrations of iso- and isothioisocyanatocyclohexanes were evaluated in different urban, residential and industrial locations from extensive VOC air quality and odour episode studies in several cities in the Northeastern edge of Spain. Around 200–300 VOC were determined qualitatively in each sample. Higher values of iso- and isothiocyanatocyclohexane were found in industrial areas than in urban or residential locations. The concentrations ranged between n.d.−246 and n.d.−29 μg m⁻³ for isocyanatocyclohexane and isothiocyanatocyclohexane, respectively, for industrial areas. On the other hand, urban and residential locations showed concentrations ranging between n.d.−164 and n.d.−29 μg m⁻³ for isocyanatocyclohexane and isothiocyanatocyclohexane, respectively. The site location (urban or industrial), the kind and nearness of possible iso- and isothiocyanatocyclohexane emission activities (industrial or building construction) and the changes of wind regimes throughout the year have been found the most important factors influencing the concentrations of these compounds in the different places.