Mercury emissions from coal combustion

Mercury liberated during coal combustion can be either discharged as vapor in the flue as or retained in the furnace ash. About 90 percent (by weight) of the mercury released from a furnace fired with pulverized coal appears to be in the vapor phase, and 10 percent remains with the furnace residual ash. For a 700-megawatt unit, approximately 2.5 kilograms of mercury per day are released.     

增钙混合煤粉燃烧特性试验研究

以低硫兖州煤为试验煤种进行了增钙混合煤粉燃烧特性试验研究,并对试验获得的混合煤粉样品TG,DTG和DSC曲线进行分析.结果表明,增钙混合煤粉燃烧热失重速率曲线相对于原状煤而言明显变得平缓,且随着添加剂比例的增加,热失重速率曲线变得更加平缓;混合煤粉燃烧速率降低,燃烧明显分为2个阶段,燃烧后移趋势增大;随着添加剂比例的增加,着火温度都有所升高,着火延迟时间变长,稳定性降低.由于混合燃料的可燃组分变少,总折算灰分增大,混合煤粉放热量降低,燃尽时间延长.     

Shape identification and particles size distribution from basic shape parameters using ImageJ

Quick and accurate particle size distribution analysis is desirable in various technical fields that handle granular or particulate materials including size reduction. We developed an ImageJ plugin that extracts the dimensions from a digital image of disjoint particles after identifying their shapes and determines their particles size distribution. We established that the major and minor axes of ImageJ fitted ellipse along with the developed correction factors efficiently determined dimensions of particles. This paper describes the plugin development and its application to food grains and ground biomass. Using computer generated geometrical shapes as reference objects, a shape identification strategy that addresses common geometric shapes such as square, inclined square, rectangle, inclined rectangle, circle, ellipse, and inclined ellipse was developed. The strategy used only three newly defined shape parameters to identify objects, such as reciprocal aspect ratio, rectangularity, and feret major axis ratio from the standard outputs generated by ImageJ. Evaluation of effects of the particles shape, size, and orientation on the deviation from the reference particle's length and width indicated that the mean absolute deviations of all these factors were less than 1.3%. Developed plugin was applied successfully to analyze the dimensions and size distribution of food grains and ground Miscanthus particles images. The plugin produced quick and accurate size distribution of particles from digital images and can be applied to variety of particle analysis applications.     

Size distributions and mineralogy of ash particles in the stratosphere from eruptions of mount st. Helens

Samples from the stratosphere obtained by U-2 aircraft after the first three major eruptions of Mount St. Helens contained large globules of liquid acid and ash. Because of their large size, these globules had disappeared from the lower stratosphere by late June 1980, leaving behind only smaller acid droplets. Particle-size distributions and mineralogy of the stratospheric ash grains demonstrate in-homogeneity in the eruption clouds.     

宿州地区麦秆混煤燃烧动力学参数研究

为了高效利用宿州地区麦秆和煤,采集了朱仙庄镇的麦秆和任楼煤矿样品,并对煤样和麦秆进行了不同比例的混合。运用labsys evo同步热分析仪测试了不同比例的麦秆与煤混合样品。测试结果表明,不同的混合比例能够改变煤的热解失重温度和增加煤的热解效率。动力学参数计算结果表明,煤中混入秸秆可以降低煤反应过程的活化能。该方法可以作为煤和秸秆综合利用的一种参考途径。     

糯玉米胚乳淀粉粒的粒度分布特征

以7个糯玉米品种为材料,采用激光衍射粒度分析仪测定其胚乳淀粉粒粒径以及体积、表面积和数目的分布,明确糯玉米胚乳淀粉粒的粒度分布特征。结果表明:糯玉米胚乳淀粉粒的粒径为0.375—30.07μm,其上限为22.73—30.07μm,平均粒径为12.33-14.60μm。淀粉粒的体积和表面积分布呈现三峰曲线,数目分布呈现单峰曲线。以体积分布曲线凹处为界线将糯玉米淀粉粒分为小型(3.519μm)、中型(3.519—7.422μm)和大型(7.422μm)。7个糯玉米品种小型、中型和大型淀粉粒体积分别占总体积的11.25%—12.46%、1.79%—6.98%和80.77%—86.96%,表面积分别占总表面积的54.28%—57.13%、2.50%—8.26%和35.97%—40.38%,数目分别占总数目的98.71%—99.39%、0.20%—0.76%和0.39%—0.53%。可见,糯玉米胚乳淀粉主要由小型淀粉粒组成,其对表面积的贡献最大,而大型淀粉粒对体积的贡献最大。品种间比较,小型淀粉粒的粒度分布差异不显著,中型和大型淀粉粒的粒度分布存在显著差异。     

玉米须对大气细颗粒物的吸附及监测潜能分析

通过分析中国主要玉米产区山东省17个地区的玉米须和叶片滞留细颗粒物(PM_(2.5))的能力,并与当地常规大气PM_(2.5)浓度监测结果进行相关性分析,探寻利用当地农作物资源进行大气颗粒物生物监测的可能。结果显示:山东沿海地区大气PM_(2.5)浓度明显低于内陆地区,与之对应的是,玉米须上PM_(2.5)含量低的地区也位于沿海,而利用玉米叶的监测无此结果。相关性分析表明,玉米叶片上PM_(2.5)含量与大气中PM_(2.5)浓度无相关性,而玉米须上PM_(2.5)滞留量与大气中PM_(2.5)月平均浓度和雨后平均浓度均存在显著的正相关(P0.01),说明玉米须可有效地、较长时间地滞留细颗粒物。研究表明,玉米须上PM_(2.5)的量不但能反映大气PM_(2.5)的污染程度,还能反映大气PM_(2.5)的污染分布,利用玉米须来监测大气PM_(2.5)的污染状况具有很大的应用潜力。     

Size matters more than chemistry for cloud-nucleating ability of aerosol particles

Size-resolved cloud condensation nuclei (CCN) spectra measured for various aerosol types at a non-urban site in Germany showed that CCN concentrations are mainly determined by the aerosol number size distribution. Distinct variations of CCN activation with particle chemical composition were observed but played a secondary role. When the temporal variation of chemical effects on CCN activation is neglected, variation in the size distribution alone explains 84 to 96% of the variation in CCN concentrations. Understanding that particles' ability to act as CCN is largely controlled by aerosol size rather than composition greatly facilitates the treatment of aerosol effects on cloud physics in regional and global models.     

Infrared spectra from fine particulate surfaces

Characteristic spectral information can be obtained from a surface composed of fine particles either if the spectrum is observed at sufficiently high signal-to-noise ratio or if the particles are well compacted.     

板栗细根的空间分布格局及季节动态

为探明板栗Castanea mollissima细根的空间分布和季节变化,以河北省迁西县北京林业大学经济林（板栗）育种与栽培实践基地6年生板栗树为研究对象,生长季内（4-10月）,采用连续根钻法（内径为8 cm）,分别在距树干50 cm和100 cm设取样点,各个样点处垂直方向分3层（0~20,20~40和40~60 cm）钻取土芯。研究了板栗细根根长密度和根质量密度的月动态变化及空间分布特征。结果表明:在生长过程中板栗细根季节变化差异显著（P < 0.05）,板栗细根根长密度月平均为1 274.9 m·m-3,在6月和10月有2个生长高峰,相比前1个月分别增加了203.0 m·m-3和524.6 m·m-3。细根根质量密度月平均值为184.7 g·m-3,有2个生长阶段（4-6月和9-10月）,10月增长较多,与9月相比增长了39.5 g·m-3。在垂直方向上,20~40 cm土层中细根根长密度和根质量密度最大且季节变化最显著（P < 0.05）。水平方向上,距树干100 cm处根长密度和根质量密度大于距树干50 cm处。整体研究表明:板栗细根的空间分布和季节变化不仅受土壤垂直格局影响,还与树种生长规律密切相关。     

新型菊芋秸秆-烟煤混合固体燃料添加剂的选择与燃烧性能分析

在研制新型菊芋秸秆-烟煤混合固体燃料的基础上,筛选不同添加剂[MgCO3、CaCO_3、Al2O_3、Al_2Si_2O_5(OH)_5]优化燃料,以提高生物质混合固体燃料的燃烧性能。将四种添加剂以3%比例(质量比)与菊芋秸秆-烟煤混合固体燃料混合,比较了不同添加剂对混合固体燃料的灰分、结渣率、放热量、烟黑、灰熔点、烟气成分等的影响。结果表明:四种添加剂对酸性气体有明显的吸附作用,且能有效降低混合固体燃料的结渣率,其中CaCO_3添加剂使混合固体燃料的灰分含量、烟黑的林格曼指数下降最为明显。这表明,CaCO_3添加剂能有效缓解混合固体燃料中的灰分、烟黑、酸性气体的生成,提高其燃烧性能,是一种较为理想的新型菊芋秸秆-烟煤混合固体燃料添加剂。     

添加剂对稻秆燃烧过程中碱金属形态分布的影响

采用化学热平衡分析方法对稻秆燃烧过程中碱金属K的化学形态及其分布,以及添加Al,Si,S,P,Ca等元素对稻秆燃烧过程中碱金属的化学形态分布的影响进行了研究.结果表明,在稻秆中加添加Al或同时添加Al和Si,可以避免稻秆燃烧过程中发生结渣和沉积问题.温度低于900℃燃烧时添加S或温度低于1 100℃添加P.可有效的缓解稻秆中碱金属引起的结渣和聚团问题.系统中Ca的增加可有效的抑制碱金属引起的结渣和聚团问题,但有可能增加其引起的沉积和腐蚀问题.而Si的增加使K以液态形式存在的摩尔百分比增加,导致底灰聚团的现象加重.     

阻燃型竹丝成形材燃烧动力学和燃烧性能

使用锥形量热仪研究了不同温度下阻燃剂磷酸氢二铵[（NH4）2HPO4]处理与未处理竹丝,并分别用三聚氰胺苯酚甲醛（MPF）共缩聚树脂和酚醛（PF）树脂浸渍所得竹丝成形材的燃烧反应过程。采用化学动力学法建立了4种竹丝成形材在燃烧过程中质量损失率和时间的动力学模型,并分析比较了4种试件的质量损失率、热释放总量、释热速率、释烟总量、一氧化碳释放量和二氧化碳释放量等燃烧性能和燃烧反应表观活化能＆。结果显示,当4种试件在质量损失率大于60％以后,均出现燃烧拐点。阻燃剂磷酸氢二铵能有效提高竹丝成形材的阻燃性能,燃烧温度735℃时．4种试件的阻燃效果依次为：经磷酸氢二铵处理的MPF树脂竹丝成形材〉经磷酸氢二铵处理的PF树脂竹丝成形材〉未经磷酸氢二铵处理的MPF树脂竹丝成形材〉未经磷酸氢二铵处理的pF树脂竹丝成形材。     

2种海水鱼工厂化循环水养殖中微细颗粒物的赋存特征

为了明晰工厂化循环水处理系统对水中微细颗粒物的去除效果,对红鳍东方鲀（Takifugu rubripes）和半滑舌鳎（Cynoglossus semilaevis）工厂化循环水养殖过程中微细颗粒物的质量、组成和粒径分布的动态变化进行研究。结果表明,基于弧形筛、泡沫分离器和生物滤池的工厂化循环水处理工艺,红鳍东方鲀和半滑舌鳎养殖池水中微细颗粒物浓度均稳定在20 mg·L^-1左右,且投喂后水中微细颗粒物含量明显增高,微细颗粒物中有机物所占比例均达到90%以上,表明水中微细颗粒物增多是投喂所致。红鳍东方鲀养殖池水中微细颗粒物的粒径主要分布在60~170 nm,半滑舌鳎养殖池水中微细颗粒物的粒径为95~420 nm。养殖池出水经水处理系统处理后,水中留存的微细颗粒物的粒径主要介于95~110 nm之间,表明该循环水养殖系统中粒径在60~95 nm之间和粒径大于110 nm的微细颗粒物可以被有效去除。