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Analysis of trace metal elements and chemical forms from waste combustion and its emissions control

垃圾燃烧中微量金属元素和化学形态分析及其排放控制

基本信息

批准号：
14380279
负责人：
NINOMIYA Yoshihiko
金额：
$ 9.47万
依托单位：
Chubu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14380279/
关键词：
Combustion of waste material Trace metal Cascade impactor CCSEM Fly ash Particulate matter Chemical forms analysis PM2.5 下水汚泥化学形態別分析凝縮性粒子下水汚泥燃焼

项目摘要

Sewage sludge, pulverized coal and the mixture of them were subjected to combustion in a laboratory-scale drop tube furnace to investigate the emission of suspended particulate matter smaller than 10μm (PM_<10>) and to study the correlation of PM_<10> emission with inorganic species of them. Combustion conditions of 1200 to 1450℃ and 0 to 50% atmospheric oxygen concentration were used and all the carbon was consumed under given conditions. The exiting gas, containing the solid products, was initially quenched with N_2 and collected by a water-cooling probe. Subsequently, coarse ash particles were collected by a cyclone. The suspension of ultrafine particles was further diluted with air, and immediately directed to a Low-Pressure-Impactor (LPI) for size-segregated collection. The LPI used here is composed of 13 stages having aerodynamic cut-off diameters ranging from 0.03 to 12.1 μm. Each stage is composed of a quartz or Teflon filter above a substrate and a substrate holder. All the fi … More lters were analyzed by XRF, XRD, Computer controlled scanning electron microscopy (CCSEM), ICP-AES, XPS and TEM to quantify the elemental composition and chemical forms. The properties of PM_<10> were studied including its concentration, particle size distribution, elemental composition and chemical forms.The results indicated that, both the ash content in the fuels and the oxygen content in gas atmosphere affected PM_<10> concentration significantly. With their increasing, PM_<10> concentration was enhanced exponentially. PM_<10> was formed having a lognormal non-gaussian size distribution. Vaporization of the inherent metals plays the paramount role on PM_<10> formation. The inherent alkali, heavy metals and a portion of Si, P, and Fe initially vaporize the resultant metallic vapors undergo oxidization to form their nuclei around 0.03μm, which subsequently undergo coagulation according to the polydisperse coagulation model. Simultaneously, the heterogeneous coagulation between the different species allowed the formation of new chemical species such as alkali/zinc phosphate and sulfates. In addition, a small amount of particles larger than 1.0μm were also found, which was dominated by the refractory metals resulted from the direct transferring of inherent minerals in the fuels. PM_<1+> was formed by the direct transformation of refractory elements in the fuels. Quartz and aluminosilicates within this portion were formed by transformation without phase change. Meanwhile, calcium/iron aluminosilicate in PM_<1+> was formed by the reaction of calcium or iron with aluminosilicate, which led to a sticky surface of the latter compound. Alkali aluminosilicate was formed as melt droplets in combustion and it condensed into large particulates in PM_<1+>. PM_1 is rich in both sulfates and phosphates of vaporized elements. The degree of vaporization of elements is determined by their content (organically bound and included minerals smaller than 10.0 μm) in the raw fuels. The elemental type also affects their vaporization greatly, which decreases in the order of Na > K > Fe > Mg > Ca > Si > Al. This is fairly consistent with the predictions of thermodynamic equilibrium calculations. The vaporized metals reacted with gaseous S0_2, P_2O_5 and SiO to form their compounds. Less

在实验室落管炉中进行了污泥、煤粉及其混合物的燃烧试验，研究了小于10μm的悬浮颗粒物(PM_&lt；10&gt；)的排放及其与无机形态的关系。采用1200~1450℃的燃烧条件和0~50%的大气氧浓度，在给定的条件下消耗所有的碳。含有固体产物的出气首先用氮气熄灭，然后用水冷探头收集。随后，粗灰颗粒被旋风分离器收集。超细颗粒悬浮液用空气进一步稀释，并立即直接送往低压冲击器(LPI)进行粒度分离收集。LPI由13级组成，气动截止线直径在0.03~12.1μm之间，每级由衬底上方的石英或特氟隆过滤器和衬底固定器组成。所有的FI…采用XRF、X射线衍射仪、计算机控制扫描电子显微镜、电感耦合等离子体发射光谱仪、X射线光电子能谱和透射电子显微镜对样品进行了分析，以确定其元素组成和化学形态。对PM&lt；10&gt；的浓度、粒度分布、元素组成和化学形态等性能进行了研究，结果表明，燃料中的灰分含量和气体中的氧含量对PM_(10)&gt；的浓度都有显著影响。随着浓度的增加，PM_(10)浓度呈指数增加。形成具有对数正态非高斯尺寸分布的PM_&lt；10&gt；。固有金属的蒸发在PM_(10)和PM_(10)的形成中起着至关重要的作用。固有的碱、重金属以及部分Si、P和Fe首先使生成的金属蒸气蒸发，然后在0.03μm左右氧化形成它们的核，然后根据多分散凝聚模型进行凝聚。同时，不同物种之间的异质凝聚允许形成新的化学物种，如碱/锌磷酸盐和硫酸盐。此外，还发现了少量大于1μm的颗粒，主要是燃料中固有矿物直接转移产生的难熔金属。PM_&lt；1+&gt；是由燃料中的难熔元素直接转化而成。这部分中的石英和铝硅酸盐是通过相变而形成的，没有相变。同时，钙或铁与铝硅酸盐反应生成钙/铁铝硅酸盐，导致后者表面粘稠。碱性铝硅酸盐在燃烧过程中形成熔滴，在PM_&lt；1+&gt；中凝聚成大颗粒。PM_1富含蒸发元素的硫酸盐和磷酸盐。元素的汽化程度取决于它们在原燃料中的含量(有机结合矿物和小于10.0μm的矿物)。元素类型对其挥发量的影响也较大，其大小顺序为：Na&GT；K&GT；Fe&GT；Mg&GT；Ca&GT；Si&GT；Al。这与热力学平衡计算的预测相当一致。蒸发金属与气态的S02、P2O5和SiO反应生成化合物。较少