分选与磨细粉煤灰对水泥胶砂性能的影响

研究了分选与磨细粉煤灰的颗粒分布与形貌的差异及对水泥胶砂性能的影响。研究结果表明:当勃氏比表面积相近,磨细粉煤灰的中位粒径大于分选细粉煤灰,其圆珠状颗粒较少,表面较为粗糙。在相同水胶比的条件下,掺分选粗粉煤灰的水泥胶砂流动度及强度均低;分选粗粉煤灰磨细后,不仅减少了颗粒的粘连,增加了比表面积,而且提高了粉煤灰的反应活性和水泥胶砂流动度及强度,虽其水泥胶砂流动度仍小于掺分选细粉煤灰的水泥,3d水泥胶砂强度也略低,但其28d水泥胶砂强度略高于掺分选细粉煤灰的水泥;在相同水泥胶砂流动度的条件下,掺磨细粉煤灰配制的水泥胶砂3d强度低于掺分选细粉煤灰的水泥,但随着水化龄期的增长,其差距逐步缩小,至60d时可超过后者。     

公路粉煤灰水泥的研制（一）

文中研究了熟料掺量、复合激发剂、石膏掺量、水泥颗粒粒度对公路粉煤灰水泥的影响.获得了公路粉煤灰水泥的最佳配料方案和工艺参数.与粉煤灰硅酸盐水泥性能相比,公路粉煤灰水泥早期强度略低于粉煤灰硅酸盐水泥,凝结时间较长,但其7d～28d水化龄期内的强度增长率较高,28d强度已赶上或超过粉煤灰硅酸盐水泥,胶砂流动度好.     

Synthesis of belite cement from lignite fly ash

Synthesis of belite cement from lignite fly ash is studied as it can be produced using low temperature between 750 and 1200 °C leading to energy saving and low carbon dioxide emission. Two synthesis methods viz., clinkerization and hydrothermal processes assisted by calcinations are studied. Lignite fly ash is used as a main starting material. For the clinkerization process, the firing temperatures, types of additives and calcium oxide/silicon dioxide ratios (Ca/Si) are studied. In this process, the reaction between fly ash and calcium carbonate produces gehlenite (2CaO·Al₂O₃·SiO₂) which is undesirable due to its poor hydraulic property. A slightly higher belite (2CaO·SiO₂) phase is obtained using sulfate ion as a dopant and using high Ca/Si ratio. The strength of gehlenite bearing belite cement is, however, rather poor. For the hydrothermal–calcination process, the alkaline concentrations and calcining temperatures are studied. The final products are belite phase and mayenite (12CaO·7Al₂O₃) which are desirable as they possess hydraulic properties. The reasonable 28-day compressive strength of the belite cement mortar of 9.5 MPa is obtained. The hydrothermal process assisted by calcination is, therefore, suitable for use in the synthesis of belite cement from lignite fly ash.     

煤粉炉粉煤灰与循环流化床粉煤灰矿物学性质比较

为了提高粉煤灰的利用率,通过化学成分分析、扫描电子显微镜(SEM)分析、X射线衍射光谱(XRD)分析和核磁共振分析,对煤粉炉和流化床2种粉煤灰的形貌、物相组成和活性进行了表征,研究了2种粉煤灰矿物学性质的差别。试验结果表明:2种粉煤灰在形貌和物相上存在较大的区别。形貌上,煤粉炉粉煤灰中存在大量的玻璃微珠,而流化床粉煤灰由于成灰温度低不存在玻璃微珠;物相上,煤粉炉粉煤灰中存在较大量的结晶类矿物,而流化床粉煤灰多为非晶玻璃态物质。通过核磁共振分析发现煤粉炉粉煤灰中硅氧结构和铝氧结构的聚合度较高,不利于活性组分溶出。     

Structure and properties of forming adsorbents prepared from different particle sizes of coal fly ash

In this paper, different particle sizes of coal fly ash FA-R (D50=15.75μm), FA-A (D50=3.61μm) and FA-B (D50=1.73μm) were treated with NaOH solution to prepare the forming adsorbents FFA-R, FFA-A and FF...     

原料粒度对粉煤灰成型吸附剂结构和性能的影响(英文)

In this paper, different particle sizes of coal fly ash FA-R (D50=15.75μm), FA-A (D50=3.61μm) and FA-B (D50=1.73μm) were treated with NaOH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B. The structure and adsorption properties of the forming adsorbents for methylene blue (MB) from aqueous solu-tion were examined. The results showed that the specific surface areas and adsorption capacities of the forming adsorbent for MB increased with decreasing particle size of raw coal fly ashes. The adsorption kinetic data of MB on FFA-R, FFA-A and FFA-B fitted the second-order kinetic model very wel with the rate constants (k2) of 3.15 × 10?2, 3.84 × 10?2 and 6.27 × 10?2 g·mg?1·min?1, respectively. The adsorption process was not only con-trol ed by intra-particle diffusion. The isotherms of MB on FFA-R, FFA-A and FFA-B can be described by the Lang-muir isotherm and the Freundlich isotherm, and the adsorption processes were spontaneous and exothermic. ? 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

Preparation and characterization of fully waste-based glass-ceramics from incineration fly ash,waste glass and coal fly ash

Municipal solid waste incineration (MSWI) fly ash (FA) is a typical hazardous waste due to its high contents of toxic heavy metals, and hence its disposal has attracted global concern. In this work, it was recycled into environmental-friendly CaO–Al₂O₃–SiO₂ system glass-ceramics via adding coal fly ash (CFA) and waste glass (WG). The effects of CaO/SiO₂ ratios and sintering temperatures on the crystalline phases, morphologies, mechanical and chemical properties, heavy metals leaching and potential ecological risks of glass-ceramics were investigated. The results showed that wollastonite (CaSiO₃), anorthite (CaAl₂Si₂O₈) and gehlenite (Ca₂Al₂SiO₇) were the dominant crystals in the glass-ceramics, which were not affected by CaO/SiO₂ ratio and sintering temperature. The compressive strength increased, while the Vickers hardness and microhardness decreased as increasing the sintering temperatures from 850 to 1050 °C, which reached their maximum values of 660.69 MPa, 6.14 GPa, and 7.43 GPa, respectively. However, the increase of CaO/SiO₂ ratio resulted into the reduction of the three mechanical parameters. As varying CaO/SiO₂ ratio from 0.48 to 0.86, the maximum compressive strength, Vickers hardness and microhardness were 611.80 MPa, 5.43 GPa, and 6.56 GPa, respectively. Besides, all the glass-ceramics exhibited high alkali resistance of >97%. The extremely low heavy metals leaching concentrations and low potential ecological risk of glass-ceramics further revealed its environmentally friendly property and potential application feasibility.     

Comparative assessment of Australian fly ash and conventional concrete bricks

A comparative study of the chemical composition, mineralogy, morphology and crushing strengths of fly ash bricks, conventional concrete bricks and fly ash samples has been undertaken. The main chemicals present in the products were silica and alumina while their main minerals were quartz, mullite, illite, vaterite, and calcite. Elemental analysis by XPS showed that the major elements in the samples were oxygen, silicon, carbon, calcium and aluminium; and scanning electron microscopy revealed that the fly ash samples consist of spherically‐shaped particles with surface attachment containing needle‐like particles. Compared with conventional concrete bricks, fly ash bricks generally have higher atomic silicon and crushing strengths but lower crystalline silica. The implication of the results on the suitability of fly ash bricks as replacements for conventional concrete bricks in the building industry is discussed from the point of view of human health and occupational safety. Copyright © 2004 Society of Chemical Industry     

粒径对粉煤灰基地聚物抗压强度的影响

为提高粉煤灰的综合利用,以工业废弃物粉煤灰为主要原料,通过碱激发制备粉煤灰基地聚物,研究了粉煤灰的粒径及粒径分布对粉煤灰基地聚物抗压强度的影响。试验结果表明:对于单峰分布不同粒径的粉煤灰来说,随着D_(50)粒径的减小,粉煤灰基地聚物的28 d抗压强度随之显著升高,早期抗压强度也随之大幅提高;对于相同D_(50)粒径下单峰和双峰分布的粉煤灰来说,单峰分布的粉煤灰基地聚物的抗压强度略低于双峰分布粉煤灰基地聚物的抗压强度;进而证明D_(50)粒径是影响粉煤灰基地聚物的因素之一,通过调节粒径分布可以改善抗压强度,为进一步控制粉煤灰基地聚物的抗压强度提供了理论基础。     

Effect of size fraction and glass structure of siliceous fly ashes on fly ash cement hydration

Paper presents effect of size fraction and glass structure of fly ashes on cement hydration. Fly ashes below 16 μm and 16–32 μm, both from the 1st and 3rd section of electro-filter, were applied. Hydration heat, content of Ca(OH)₂ and unreacted C₃S were studied and compressive strength and microstructure were analysed. Results show that finer ashes have higher depolymerization degree of SiO₄ units in glass what increases pozzolanic reactivity. Incorporation of fly ashes below 16 μm from the 3rd section gives cement class 52.5 N. At 180 day, Ca(OH)₂ content decreases by 67% and C₃S hydration degree increases by 50% relative to control sample.     

Effects of particle size on microstructure and mechanical strength of a fly ash based ceramic membrane

Recycling fly ash for ceramic membrane fabrication not only reduces solid waste discharge, but also decreases the membrane cost. Now, fly ash is becoming a promising substitute material for ceramic membrane preparation. A significant difference between fly ashes from different plants is the particle size, which makes performances of fly ash membranes unpredictable. The novelty of this work is to clarify the effects of the particle size of fly ash on ceramic membranes, thereby giving practical suggestions on fly ash selection for ceramic membrane preparation. Ceramic membranes were fabricated with different sizes of fly ashes. Effects of particle size on porosity, pore size, microstructure, mechanical strength and gas permeability of the membrane were investigated. Results indicate that a broader particle size distribution of fly ash leads to a denser structure of membrane with a lower porosity. Pore size and gas permeability of membrane increase while bending strength decreases with the particle size increasing. Bending strength of a fly ash membrane is largely determined by large particles in the fly ash because the large particles lead to cracks in the membrane. This work provides experimental bases for developing high performance ceramic membranes from fly ash.     

固硫灰渣和粉煤灰的特性对比分析

介绍了固硫灰渣的形成过程,并将固硫灰渣与粉煤灰的物化特性进行对比,分析表明:固硫灰渣与粉煤灰的化学成分类似,矿物组成差异较大;固硫灰渣与粉煤灰一样,具有较高的火山灰活性,用于建筑材料的生产完全可行.     

Effect of particle size and alkali activation on coal fly ash and their role in sintered ceramic tiles

We focus on fly ashes of different sizes and their alkali-activation on ceramic products. Backscattered electron imaging-energy dispersive X-ray spectroscopy was used to classify coal fly ash particles according to particle size and to study the pre-activation of particles with different sizes. Secondary electron imaging-energy dispersive X-ray spectroscopy was used to study the role of coal fly ash particles of different sizes in ceramic bodies before and after alkali-activation. Ash particles can be divided into three classes based on size: clay-, quartz- and feldspar-like particles, which act as clay, quartz and feldspar, respectively, in ceramic bodies. The pre-activation process contributes to the plasticity of ash particles, the crystal skeleton role of clay-like particles and the fluxing agent role of feldspar-like particles, so preprocessing can improve the performance of ash-based ceramic tiles significantly. This research provides a new pretreatment method for coal fly ash in ceramic fields.     

The effect of fly ash and limestone fillers on the viscosity and compressive strength of self-compacting repair mortars

Today, self-compacting mortars are preferred for repair purposes due to the application easiness and mechanical advantages. However, for self-compactability, the paste phase must meet some certain criteria at fresh state. The cement as well as the ingredients of the paste, powders with cementitious, pozzolanic or inert nature and plasticizing chemical admixtures should be carefully chosen in order to obtain a suitable paste composition to enrich the granular skeleton of the mix. The physical properties of powders (shape, surface morphology, fineness, particle size distribution, particle packing) and physico-chemical (time-dependent hydration reactions, zeta potentials) interactions between cement powder and plasticizer should be taken into consideration. All these parameters affect the performance of fresh paste in different manners. There is no universally accepted agreement on the effect of these factors due to the complexity of combined action; thus, it is hard to make a generalization.This study deals with the selection of amount and type of powders from the viewpoint of fresh state rheology and mechanical performance. The influence of powder materials on self-compactability, viscosity and strength were compared with a properly designed set of test methods (the mini-slump, V-funnel tests, viscosity measurements and compressive strength tests). It may be advised that, for each cement-powder-plasticizer mixture, a series of test methods can be used to determine the optimum content and type of materials for a specified workability.     

Fly ash effects: I. The morphological effect of fly ash

The morphological effect is an important part of fly ash effects. The paper analyzes emphatically this effect and points out that it is composed of the filling role, surface role and lubricating role. For different fly ash, these roles are different. They must be considered synthetically when the morphological effect is analyzed. Analyzing result shows that the filling role is relative to the particle size, the surface role is relative to the specific surface area and the water affinity and the lubricating role is relative to the shape of particle. The morphological effect of fly ash is the synthetical embodiment of these roles.     

粉煤灰在油田开发中的应用

本文在对某热电厂粉煤灰的粒度、化学成分、水化性等性能分析的基础上,介绍了一种以粉煤灰为主剂的水井用调剖剂。经室内实验分析和现场应用的效果分析,证明FP-2型粉煤灰类调剖剂的堵水调剖效果好,为粉煤灰的综合利用找出了一条新的应用途径。     

Mineralogical and elemental composition of fly ash from pilot scale fluidised bed combustion of lignite, bituminous coal, wood chips and their blends

The chemical and mineralogical composition of fly ash samples collected from different parts of a laboratory and a pilot scale CFB facility has been investigated. The fabric filter and the second cyclone of the two facilities were chosen as sampling points. The fuels used were Greek lignite (from the Florina basin), Polish coal and wood chips. Characterization of the fly ash samples was conducted by means of X-ray fluorescence (XRF), inductive coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), particle size distribution (PSD) and X-ray diffraction (XRD). According to the chemical analyses the produced fly ashes are rich in CaO. Moreover, SiO₂ is the dominant oxide in fly ash with Al₂O₃ and Fe₂O₃ found in considerable quantities. Results obtained by XRD showed that the major mineral phase of fly ash is quartz, while other mineral phases that are occurred are maghemite, hematite, periclase, rutile, gehlenite and anhydrite. The ICP-OES analysis showed rather low levels of trace elements, especially for As and Cr, in many of the ashes included in this study compared to coal ash from fluidised bed combustion in general.     

Effect of flotation on the dioxin distribution in size-fractioned fly ash of hospital solid waste incineration

After the flotation of hospital solid waste incinerator (HSWI) fly ash, two types of solid products, froths and tailings, are produced. This paper reports the effect of flotation on the dioxins distribution patterns in different particle size fractions (?25, ?38, +25, ?75, +38, ?106, +75 and +106 µm) of fly ash. The results showed that the froths had a higher small-size particle distribution than that of the raw fly ash. The dioxin content with particle size in the flotation products depended on the partition behavior of powder-activated carbon (PAC). The dioxin content in the fine particles of the froths was higher than that in the coarse particles, and the highest content was in the finest particles (?25 µm). The dominant dibenzo-p-dioxins and dibenzofurans (PCDD/F) congeners in the froths and tailings were similar to those in the raw fly ash. A positive correlation between carbon removal and PCDD/F removal with different size fractions was observed. The carbon removal efficiencies of the fractions of ?25 and ?38, +25 µm were evidently higher than those of the other particle size fractions. Similarly, the PCDD/F removal efficiencies in fractions of ?25 and ?38, +25 µm could reach 156.9% and 115.0%, respectively.     

分选与磨细加工对粉煤灰物化性质以及颗粒特性的影响

在半工业化分选与粉磨工艺系统中对粉煤灰进行了分选与磨细处理,并测定了不同粉煤灰样品的物化性质及颗粒特性。结果表明,分选与磨细处理对粉煤灰的化学成分影响不大,但能够明显改善粉煤灰的物理性质,如:需水量比下降、密度增加、活性指数增加。两种处理方式相比较,分选更有利于粉煤灰需水量比的降低而磨细更有利于粉煤灰活性指数的提高;分选灰的颗粒分布范围较窄而磨细灰的颗粒分布范围较宽。     

粉煤灰制备P型分子筛工艺研究

通过对粉煤灰成分的系统分析,论述了利用粉煤灰制备P型分子筛的可能性,并对其制备条件和产品性能进行了实验研究。结果表明,只要条件控制得当,就可以制得性能较好的P型分子筛,为粉煤灰的综合利用开辟了一条新的途径。