Geological behavior of wet outflow deposition fly ash

The geological behaviors of wet outflow deposition fly ash were investigated, including the feature of in-situ single and even bridge cone penetration test (CPT) curves, the change of the penetration parameters and vane strength with the increase of depth and the difference of the penetration resistance on and down the water level. Drilling, CPT and vane shear test were carried out in silty clay, fine sand, and fly ash of the ash-dam. The CPT curves of the fly ash do not show a critical depth. The cone resistance (qc) of the fly ash is smaller than that of silty clay or sand; the friction resistance is smaller than that of filling silty clay, similar to that of deposition silty clay or more than that of fine sand; the friction ratio is smaller than that of filling silty clay, or more than that of deposition silty clay or much more than that of fine sand. The specific penetration resistance (ps) is similar to that of filling silty clay, or more than that of deposition silty clay. There is a clear interface effect between the deposition fly ash and the clay. Interface effect of ps-h curve at the groundwater table is clear, and ps of the fly ash reduces significantly under the table. The vane strength of the fly ash increases as the depth increases. The deposition fly ash with wet outflow is similar to silt in the geological behavior.

Behavior of Cu, Pb, and Zn in Ash during the Endothermic Burning of Mixed Industrial Wastes

The behaviors of Cu, Pb, and Zn during the endothermic burning of heterogeneous wastes were investigated using a variety of operational parameters, i.e., the mixed waste ratio, burning temperature, and burning time, to obtain fundamental knowledge to generate an optimal burning operation and recycling strategy for bottom ash. Changing these parameters had no impact on the Cu content of the ash, whereas the Pb content depended on the burning temperature and the mixed ratio, and the Zn content was affected by all three parameters. It was found in this study that the optimal burning conditions were a temperature of 1100?C, a time of 15 minutes, and either the current waste conditions or waste conditions with double the waste plastic and wood content.

Technological and Environmental Behavior of Coal Fly Ash in Lime-Based Materials

Coal fly ash is considered an industrial by-product derived from coal combustion in thermal power plant. It is one of the most complex anthropogenic materials. Its improper disposal has become an environmental concern and resulted in a waste of recoverable resources. The aim of this paper is to study the physico-chemical characteristics of binders based on coal fly ash and lime in order to develop an eco-cement. The various characterization tests carried out are X-ray fluorescence, X-ray diffraction, compressive strengths, thermophysical properties and setting time. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of fly ash, lime and binders. This allowed us to see that the chemical composition of fly ash is similar to that of cement. Compressive strengths of mortars containing 20%, 40%, 60% and 80% of fly ash have shown that fly ash has a long-term positive effect which might be related to a pozzolanic activity. The L3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others. The binder setting start time is greater than that of cement but shorter than that of lime. The study of the thermophysical properties of the L3 binder shows that it has a higher thermal resistance than cement mortar. Moreover, it heats up less quickly because of its low effusivity compared to that of the latter. This analysis highlighted the principal characteristics that must be taken into account to use coal fly correctly in lime-based materials.

Dissolution of Rare Earth Elements from Coal Fly Ash Particles in a Dilute H₂SO₄Solvent

Recently, the worldwide supply of rare earth element (REE) resources will be severely restricted. On the other hand, coal fly ash particles emitted from coal-fired electric power plants contain relatively high concentrations of REEs. The contents of REEs in coal fly ash are regularly several hundreds of ppmw. In order to extract and recover REEs from coal fly ash particles, as a first step, we have investigated their dissolution behavior in a dilute H2SO4 solvent. The REE content of coal fly ash specimens has been precisely determined, and their presence in the ash component of the original coal and their enrichment in coal fly ash particles during coal combustion have been suggested. REEs in coal fly ash dissolve gradually in H2SO4 over time, and this implies two types of occurrences of the REEs in coal fly ash particles. By applying the unreacted core model to the dissolution behavior of REEs in a H2SO4 solvent, we can explain both types of occurrences.

A Survey on Effect of Agro Waste Ash as Reinforcement on Aluminium Base Metal Matrix Composites

In the present day availability of agricultural waste products is very huge quantity. Most of the industries prefer Metal matrix composite (MMC) due to their density, high strength to weight ratio, hardness, corrosion resistance, fatigue and creep resistance. Hence they are widely used in structural applications along with aerospace and automobile industry, marine, sports, electronic and automation industries. In the present paper a study is focused on the mechanical, tribological and corrosion behavior of the metal matrix composite using different agro waste ash which is easily available. Agro waste ash like Rice Husk, groundnut shell, bamboo leaf, coconut shell can be used as reinforcement and applicable for various applications like automotive, structural components. From this current study, it’s clearly identified that addition of agro waste ash as reinforcement with Aluminium improves the properties of metal matrix composite. Aluminium metal with such reinforcement materials has shown a high specific strength, yield strength and ultimate tensile strength, also it will increase hardness, satisfactory levels of corrosion resistance.

Comparative Characteristics of Hydrated Lime with Fine Sewage Sludge Ash (FSSA) and Coal Fly Ash (CFA)

The disposal of waste has become an environmental issue due to the limited available landfilling space. This paper aims to compare the characteristics of hydrated lime with fine sewage sludge ash (FSSA) and coal fly ash (CFA). Multiple techniques, X-ray fluorescence (XRF), X-ray diffraction (XRD), the Fourier transform infrared (FTIR), compressive strengths, thermophysical properties, and setting time were used to assess the physicochemical characteristics of the lime-based materials. X-ray fluorescence and X-ray diffraction were used to determine the chemical composition and phases of ashes, lime and binders. The results showed that the chemical composition of ashes is similar to that of cement. Besides glass, the main minerals identified in CFA and FSSA are quartz (SiO2) and anhydrite (CaSO4). Moreover, calcium aluminium oxide (Ca3Al2O6) was detected for CFA and phosphorus calcium silicate (Ca2SiO4-Ca3(PO4)2) for FSSA and minor phases were detected for both. FTIR measurements were carried out to characterize the inorganics components of different samples. Compressive strengths of mortars with different formulations have shown that both have a long-term positive effect which might be related to a pozzolanic activity. For the CFA the L3 binder consisting of 60% of coal fly ash and 40% lime has a higher compressive strength than the others while for the FSSA the L4 binder consisting of 80% fine ash and 20% lime has a higher compressive strength than the others. Both binders setting start times are greater than that of cement but shorter than that of lime. The study of the thermophysical properties of binders shows that they have a higher thermal resistance than cement mortar. Moreover, binders heat up less quickly because of their low effusivity compared to cement. Lime-based materials system could be a promising option to both relieve the waste disposal pressure and provide a potential sustainable construction material.

温度回升对坝体运行后期工作性态的影响研究

温度回升一直是大坝施工运行期间研究的重点之一。为此,结合周宁碾压混凝土重力坝,通过仿真建模,线性计算,采用张国新等人提出的高掺粉煤灰混凝土水化热温升组合函数模型,分析预测坝体后期温度回升,探究其对坝体变形、应力的影响。仿真预测结果表明,温度回升会在建坝4~5 a后达到峰值,温度回升对坝体变形的影响较小,温度回升至稳定后变形逐渐消除;对应力的影响总体来说是有利的,局部区域会产生拉应力过大。温度回升是一个长期过程,需要在大坝运行期工作性态安全评估充分考虑温度回升的影响。该研究预测性地分析了温度回升可能发生后对坝体运行后期工作性态的影响,可为其他工程温度回升的研究提供参考。

煤灰熔融行为及其矿物质作用机制的量化研究

选取典型高灰熔点和低灰熔点煤种,利用X射线衍射仪(XRD)和扫描电镜能谱仪(SEMEDX)对高温气化条件下煤灰熔融行为及其矿物质演变规律进行了实验研究与量子化学计算.结果表明:高温下大量莫来石的生成是导致煤灰试样A具有高灰熔融温度的主要原因;煤灰试样B中由于存在较多的硬石膏、钠长石等低熔融矿物质,且CaO与莫来石反应生成钙长石与钙黄长石的化学反应在煤灰试样B熔融过程中起到了关键作用,从而使其具有低的熔融温度.经量子化学计算分析表明,由于莫来石易与电子接受体结合而难与电子给予体结合,在煤灰熔融过程中,莫来石易与煤灰中常见的碱性阳离子(Ca2+、Mg2+、Fe2+、Na+、K+)电子接受体反应生成其他物质,通过添加不同的阳离子可促使莫来石向不同矿物质转变,可以进一步控制煤灰的熔融变化过程及其熔融温度.

垃圾焚烧飞灰中重金属的浸出规律

测定了垃圾焚烧飞灰中Zn、Pb、Cu、Cr、Ni的浸出率与pH值的关系,并利用MINTEQA2模型进行了浸出规律模拟。结果表明:Pb、Cu、Zn、Cr、Ni的模拟浸出值与实测浸出值基本吻合,模拟浸出值可反映实际浸出情况;pH<2时,Zn、Cu、Pb的浸出率较大,8<pH<12时浸出率接近0;Zn、Pb的浸出率分别在pH<7、pH<2时达到最大值,最大值分别约为75%及72%,pH值>12时随pH值的增加,其浸出率逐渐增强;Cr在pH<4时浸出率较大,最大浸出率达43%,4<pH<12时浸出率接近零,pH>12时其浸出率再次增加;Ni的浸出率在pH<2时随pH值的增加而降低,2<pH<13时其浸出率接近零。

准东煤燃烧过程中Na/Ca/Fe对结渣行为影响的机理研究

在一维沉降炉实验系统中进行准东煤燃烧实验,采用非冷却的取样探针在不同烟气温度下收集灰样并进行分析,以获得烟气中不同无机成分在结渣前的形态及灰颗粒间的结合方式.结果表明:当烟气温度为1 000℃时,存在熔融态Na的硅酸盐、硅铝酸盐和CaSO_4,这些熔融态的灰颗粒会撞击、黏附在管壁上;当渣层逐渐增厚时,表面温度升高,可能在渣层表面形成熔融态的膜,以捕捉其他灰颗粒;Fe具有助熔作用,可与硅钙镁铝钠体系形成低温共熔物,当Fe_2O_3颗粒撞击到焦体熔融表面时,其助熔作用会降低焦体表面的熔点而形成新的焦体.

粉煤灰A-TIG熔池流动行为及焊缝性能分析

采用粉煤灰作为活性剂对Q235钢进行钨极氩弧焊,研究其对熔池流动及焊缝的组织和性能的影响.对Q235钢焊接后在基体上的铺展面积进行了测试;采用点扫描的方法确定了熔池内部不同位置钨粒子的含量;对焊缝的截面形貌、显微组织和性能进行了观察和测试.结果表明,焊缝的深宽比增大,显微组织出现细化;熔池的流动方向发生了改变,即熔池流动方向为从边缘向中心流动;焊缝的显微硬度较无活性剂时有所提高,耐磨性及耐蚀性也得到了一定的提高,冲击吸收功增加.

稻壳灰混凝土性能研究

研究了稻壳灰作为一种添加剂,0～30%的等量取代水泥后,对混凝土性能的影响。混凝土的配合比为1:2:4:0.6(水泥:砂:碎石:水胶比)。测试了稻壳灰混凝土试件性质、抗压强度、劈裂抗拉强度、抗折强度等。结果表明,随着稻壳灰用量的增加,混凝土凝结的时间延长,而抗压强度、劈裂抗拉强度、抗折强度相应的降低。

煤焦中矿物质行为与灰熔融温度的关系

在 1 0 0 0～ 1 60 0°C制焦温度下 ,借助于扫描电子显微镜研究了扎莱诺尔、后布连、东胜、西山、沈北、沈阳和阳泉 7种煤焦中的矿物质行为。研究结果表明 ,高温热处理后焦中的矿物质变化行为与相应煤的灰熔点密切相关。当制焦温度接近或超过相应煤灰的熔融温度时 ,焦中的矿物质出现了明显的迁移倾向 ,从初始的随机分散分布发展到团聚 ,温度越高 ,矿物质的分布改变也越大 。

单颗粒玉米秸成型燃料管式炉燃烧特性实验

为了设计和优化玉米秸成型颗粒燃烧机,在卧式管式炉中实验研究了燃烧条件(炉温、颗粒长度、空气流量)对单个玉米秸成型颗粒燃烧过程的影响。结果表明:炉温>700℃时,固体的熔融和烧结会阻碍燃烧过程;成型颗粒内部温度和炉温有一定的差别,各温度(500～900℃)下燃烧灰的水溶性较低,均<13%;成型颗粒长度(20～50 mm)、空气流量(150～550 L/h)对燃烧过程的影响很小;与木质颗粒相比,玉米秸成型颗粒热解强度低,燃烧时间更长。实验结果将为秸秆颗粒燃烧机的设计和优化提供参考。

一种评判煤灰结渣特性的新方法

针对煤灰结渣特性单一评判指标的预测精度普遍偏低的问题,基于偏最小二乘算法(PLS)和交叉验证理论建立了煤灰结渣特性预测模型,该模型有4个输入变量,即煤灰的软化温度、碱酸比、硅比和硅铝比,1个输出变量,即结渣程度.提出了指标的同向性和异向性的概念,依据所提出的概念对各单一指标对煤灰结渣特性的作用进行了定性分析与讨论,结合拟合方程,给出了煤灰结渣特性的评判依据.通过对测试样本进行检验,结果表明:所提出的PLS预测模型的预测精度远高于单一评判指标的预测精度,所建模型是合理可行的.

生物质颗粒燃料灰行为研究进展

本文综述生物质颗粒燃料产业现状及生物质颗粒燃料的灰行为研究现状,分析了生物质颗粒燃料灰行为的研究前景,指出随着生物质颗粒燃料的灰行为问题的解决,生物质颗粒燃料必将成为我国未来新型能源的重要组成部分。

准东粉煤不均匀熔融规律研究

针对准东煤燃烧过程中存在的结渣问题,采用浮沉法将准东原煤分成不同密度子样,测定了各密度级别灰样的化学组成、矿物组成、煤灰熔融温度和烧结温度,探索准东煤灰微观不均匀熔融规律,揭示准东燃烧结渣机理。结果表明,准东煤粉主要分布在1.40~1.50 g/cm3。煤粉密度从<1.50g/cm3升至>1.60 g/cm3时,煤灰中SiO_2含量从28.82%提高至60.27%,CaO含量从29.91%降至3.96%,Fe_2O_3含量则从5.85%提高至12.68%,MgO含量从9.09%降至1.92%;软化温度从1 297℃降至1 127℃,烧结温度则从551℃升高至>1 000℃。不同密度煤粉颗粒中化学组成和矿物组成的分化导致灰熔融性的不均匀分布,而其灰成分的特殊性导致了熔融温度和烧结温度变化趋势的差异。

氨—碳铵法浸出含锌烟灰

研究氨—碳铵体系中pH、总氨浓度、液固比(L/S)、反应温度、反应时间等因素对三种含锌烟灰中锌和主要杂质元素浸出行为的影响。结果表明,较佳的工艺条件是:浸出剂总氨浓度9mol/L、pH=10.00、L/S=5、反应温度50℃、反应时间60min。此时锌浸出率大于80%。

高铝粉煤灰在碱溶过程中的结构演变及行为

为了探究高铝粉煤灰在碱溶液中的反应规律,利用XRD和SEM等手段分析了山西某地高铝粉煤灰与氢氧化钠溶液反应前后的结构演变及行为。研究结果表明:高铝粉煤灰主要由莫来石、石英和玻璃态物质组成,其元素分布弥散。在120℃的氢氧化钠溶液中,玻璃态物质能被较快分解,而莫来石与石英溶解缓慢,并生成铝酸钠与硅酸钠,二者进一步生成钠硅渣。180℃下添加石灰时,氢氧化钠溶液浓度不低于30 g/L时才能有效分解莫来石与石英,形成铝雪硅钙石和铝酸钠。