垃圾焚烧飞灰颗粒的微观形态特征及能谱研究

利用SEM/EDX，观察了垃圾焚烧飞灰颗粒的微观形态特征，探讨了其主要组成元素及其质量分数。实验结果表明，飞灰颗粒形态多样化，其中以不规则形状聚合体居多，球形体、絮状集合体相对较少，少数颗粒为棒状集合体。球形飞灰颗粒很少有重金属分布，不规则形状聚合体或絮状集合体的表面易分布重金属。从飞灰颗粒表面、内部组成元素的质量分数来看，Si、Ca、Al为主要元素。飞灰颗粒表面、内部有重金属Pb、Cu等分布，局部测定点其质量分数可高达16.2%和14.5%。     

New ceramic microfiltration membranes from mineral coal fly ash

This work aims to develop a new mineral porous tubular membrane based on mineral coal fly ash. Finely ground mineral coal powder was calcinated at 700 °C for about 3 h. The elaboration of the mesoporous layer was performed by the slip casting method using a suspension made of the mixture of fly ash powder, water and PVA. The obtained membrane was submitted to a thermal treatment which consists in drying at room temperature for 24 h then a sintering at 800 °C. SEM photographs indicated that the membrane surface was homogeneous and did not present any macro defects (cracks, etc.). The average pore diameter of the active layer was 0.25 μm and the thickness was around 20 μm. The membrane permeability was 475 l/h m² bar.This membrane was applied to the treatment of the dying effluents generated by the washing baths in the textile industry. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 l/h m²). The quality of permeate was almost the same with the two membranes: the COD and color removal was 75% and 90%, respectively.     

Floating cultivation of marine cyanobacteria using coal fly ash

The aim of this study was to develop improved methodologies for bulk culturing of biotechnologically useful marine cyanobacteria in the open ocean. We have investigated the viability of using coal fly ash (CFA) blocks as the support medium in a novel floating culture system for marine microalgae. The marine cyanobacterium Synechococcus sp. NKBG 040607 was found to adhere to floating CFA blocks in liquid culture medium. Maximum density of attached cells of 2.0×10⁸ cells/cm² was achieved using sea water. The marine cyanobacterium Synechococcus sp. NKBG 042902 weaklyadhered to floating CFA blocks in BG-11 medium. Increasing the concentration of calcium ion in the culture medium enhanced adherence to CFA blocks.     

Fast physics-chemical characterization of fly ash

This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or siliceous and aluminous materials according to the ASTM C 618-94a. The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine fineness range, the reactive alumina (Al₂O₃^r−) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO₂^r−) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is due primarily to the chemical interaction between the gypsum and the C₃A in the Portland cement and the reactive alumina (Al₂O₃^r−) in the fly ash.     

Preparation and characterization of activated carbon from bagasse fly ash

Activated carbons from bagasse fly ash (BFA) were prepared by one step chemical activation using ZnCl₂ as activating agent, or combination method of chemical with CO₂ physical activation (physicochemical activation). The development of porosity was studied in correlation with the method of activation, activation temperature, and also the chemical weight ratio. A typical sample by the combination method at 600 °C and weight ratio of ZnCl₂:BFA = 2 exhibited micropore volume of 0.528 cc/g, mesopore volume of 0.106 cc/g and surface area of 1200 m²/g. For determining the adsorption capacity of the carbon samples in solutions, phenol and methylene blue equilibrium adsorption experiments were conducted. The properties and adsorption capacity of the synthesized activated carbons has been compared to commercial activated carbon (Norit^® SX Plus).     

粉煤灰合成Na-X沸石去除废水中镍离子的研究

粉煤灰通过碱熔融 水热法合成了Na-X型沸石,研究了Na-X型沸石的用量、吸附时间、溶液pH值、初始镍离子浓度和温度对废水中镍离子去除效果的影响。结果表明,Na-X型粉煤灰沸石对镍离子的去除性能与化学原料合成的13X相当,明显优于粉煤灰。在20℃,pH值为6,沸石用量10g/L,吸附15min时,对初始浓度为20mg/L~150mg/L的镍离子去除率均可达90%以上。镍离子的吸附过程符合Langmiur吸附等温方程式,其单层吸附量为11.2×10^-3。粉煤灰沸石重复使用5次,对废水中镍离子的去除率仍高达95%,再生性能良好。     

Determination of total mercury in coal fly ash by gold amalgamation cold vapour atomic absorption spectrometry

A method for the determination of total mercury in coal fly ash by gold amalgamation cold vapour atomic absorption spectrometry (CV-AAS) was optimized. Most of the experiments were performed on NBS SRM 1633a Coal Fly Ash with a certified value of 160 ± 10 ng Hg g^?1. The main attention was focused on the decomposition of the sample. The efficacy of pressure decompositions in closed silica and sealed Pyrex tubes using various combinations of acids (HNO₃, HCl, HClO₄) was compared with oxidative combustion of the coal fly ash. Notwithstanding the incomplete mineralization of the sample in sealed tubes, the results obtained showed good agreement with the certified value and results obtained by neutron activation analysis (NAA), which suggests that mercury is quantitatively released from the sample into solution. Lower results were obtained using decomposition in closed (but not hermetically sealed) silica tubes owing to losses of mercury by volatilization during decomposition. Interferences from some metal ions (nickel, lead, copper, silver, palladium, zinc and antimony) were also examined. The results showed a serious depression of the mercury signal only when gold, palladium and platinum were present at higher concentrations, which never or very seldom occur in fly ash matrices, and therefore do not represent a limitation of the method.     

褐煤SHELL气化飞灰黏附影响因素的研究

通过激光粒度仪、X射线荧光光谱仪、扫描电子显微镜等现代化分析测试技术对褐煤样、飞灰样以及换热废锅中的积灰样进行了粒度分布、化学组成、晶体矿物组成、微观形貌、微区化学组成等特征的分析,研究影响飞灰黏附特性的因素。并通过引入富集系数,描述各个元素在煤灰、正常飞灰、废锅积灰中的迁移富集情况。结果表明,在废锅积灰中有含铁矿物的生成,同时Na、K、Fe、S、P元素在废锅积灰中发生富集,在飞灰与积灰颗粒边缘处有大量的Fe、Na元素的富集。     

Studies of fly ash using thermal analysis techniques

Improved thermoanalytical methods have been developed that are capable of quantitative identification of various components of fly ash from a laboratory-scale fluidized bed combustion system. The thermogravimetric procedure developed can determine quantities of H₂O, Ca(OH)₂, CaCO₃, CaSO₄ and carbonaceous matter in fly ash with accuracy comparable to more time-consuming ASTM methods. This procedure is a modification of the Mikhail-Turcotte methods that can accurately analyze bed ash, with higher accuracy regarding the greater amount of carbonaceous matter in fly ash. In addition, in conjunction with FTIR and SEM/EDS analyses, the reduction mechanism of CaSO₄ as CaSO₄+4H₂ CaS + 4H₂O has been confirmed in this study. This mechanism is important in analyzing and evaluating sulfur capture in fluidized-bed combustion systems.     

Direct determination of Ge in hot spring waters and coal fly ash samples by hydride generation-ETAAS

A method for Ge determination in hot spring water and acid extracts from coal fly ash samples involving hydride generation, trapping and atomisation of the hydride generated from Ir-treated graphite tubes (GTs) has been developed. Hydride was generated from hydrochloric acid medium using sodium tetrahydroborate. Several factors affecting the hydride generation, transport, trapping and atomisation efficiency were studied by using a Plackett-Burman design. Results obtained from Plackett-Burman designs suggest that trapping and atomisation temperatures are the significant factors involved on the procedure. The accuracy was studied using NIST-1633a (coal fly ash) reference material. The detection limit of the proposed method was 2.4 μg l⁻¹ and the characteristic mass of 233 pg was achieved. The Ge concentrations in fly ash and hot spring samples were between 6.25-132 μg g⁻¹ and 12.84-36.2 μg l⁻¹.     

Specific features of adsorption of azo dyes on fly ash

A possibility to utilize fly ash (FA) formed at coal-fired power plants as a cheap adsorbent for the purification of wastewater containing azo dyes methylene blue (MB) and methyl red (MR) was considered. The effect of an FA additive on the adsorption capacity of active carbon was studied. The efficiency of FA as an adsorbent for the purification of aqueous solutions from MB and MR was shown. The adsorption is also fairly efficient when active carbon is partially replaced by FA. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 545–548, March, 2007.     

Influence of several experimental parameters on As and Se leaching from coal fly ash samples

Coal fly ash leaching process for As and Se is studied. Environmental parameters such as pH, temperature, solid-liquid ratio, particle size and leaching time are taken into account in order to simulate As and Se leaching process for disposal coal fly ash. Analysis of reference materials was carried out by using of hydride generation coupled to atomic fluorescence spectrometry. Plackett-Burman experimental design is used to know the significative parameters, and Box-Behnken experimental design is used to refine the results obtained for these significative parameters. pH and temperature shown a hardly influence in leaching process. Furthermore, leaching time was also significative. According our results, it may be assumed that percentage of As and Se leaching in experimental conditions tested is relatively low for acidic fly ashes.     

Speciation of chromium in Australian fly ash

The concentrations of chromium (III) and (VI) in fly ash from nine Australian coal fired power stations were determined. Cr(VI) was completely leached by extraction with 0.01 M NaOH solution and the concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). This was confirmed by determining Cr(III) and Cr(VI) in the extracts of fly ash that had been spiked with chromium salts. These analytical measurements were done using a combination of ion-exchange chromatography and ICP-AES. The elutant was 0.05 M HNO₃ containing 0.5%-CH₃OH. When the column was operated at a flow rate of 1.2 ml min⁻¹ and samples were injected by use of a sample loop with a volume of 100 μl, Cr(III) and Cr(VI) in sample solution was exclusively separated within approximately 10 min. The detection limits (3σ) were 5 ng for Cr(III) (0.050 mg l⁻¹) and 9 ng for Cr(VI) (0.090 mg l⁻¹), respectively. A relative standard deviation of 1.9% (n = 6) was obtained for the determination by IC-ICP-AES of 0.25 mg l⁻¹ Cr(III) and Cr(VI).     

晋城粉煤煤灰不均匀熔融规律研究

提出了煤灰不均匀熔融概念,有助于解决灰熔融性测定结果和锅炉实际情况不符的问题。采用山西晋城煤,将其粉磨到工业煤粉细度,通过浮沉分成不同密度级别子样,使用灰锥法测定其在弱还原气氛下的熔融温度,使用压降法测量其烧结温度,采用XRD、XRF、SEM-EDX等分析手段对灰样的不均匀熔融现象进行机理研究。结果表明,晋城煤灰软化温度为1501℃,而不同密度级别子样发生分化,软化温度从1292℃到高于1600℃变化;同样,晋煤煤灰烧结温度为885℃,子样的烧结温度从833到943℃变化。机理研究表明,不同密度级别子样Al₂O₃、Fe₂O₃和SO₃含量发生不均匀分布,是造成煤灰熔融特性和烧结特性差异的根本原因。     

Determination of trace elements in coal and coal fly ash by joint-use of ICP-AES and atomic absorption spectrometry

Microwave-acid digestion (MW-AD) followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES), graphite furnace atomic absorption spectrometry (GFAAS), and hydride generation atomic absorption spectrometry (HGAAS) were examined for the determination of various elements in coal and coal fly ash (CFA). Eight certified reference materials (four coal samples and four CFA samples) were tested. The 10 elements (As, Be, Cd, Co, Cr, Mn, Ni, Pb, Sb, and Se), which are described in the Clean Air Act Amendments (CAAA), were especially considered. For coal, the HF-free MW-AD followed by ICP-AES was successful in the determination of various elements except for As, Be, Cd, Sb, and Se. These elements (except for Sb) were well-determined by use of GFAAS (Be and Cd) and HGAAS (As and Se). For CFA, the addition of HF in the digestion acid mixture was needed for the determination of elements, except for As, Sb, and Se, for which the HF-free MW-AD was applicable. The use of GFAAS (Be and Cd) or HGAAS (Sb and Se) resulted in the successful determination of the elements for which ICP-AES did not work well. The protocol for the determination of the 10 elements in coal and CFA by MW-AD followed by the joint-use of ICP-AES, GFAAS, and HGAAS was established.     

燃煤飞灰中铁质微珠的显微结构及其组成研究

选用我国三个典型燃煤煤种的电厂飞灰中铁质微珠,进行显微结构与物相组成等方面的研究。揭示出铁质微珠中存在空心微珠、子母珠和实心微珠三种显微颗粒类型,在这些显微颗粒表面可识别出以微粒状和八面体自形晶两种方式存在的赤铁矿和磁铁矿析晶;元素分析表明,燃烧褐煤电厂铁质微珠主要由Fe、Ca、Al、和Si元素组成,燃烧烟煤和无烟煤的电厂铁质微珠主要由Fe、Al和Si元素组成;物相分析发现,Fe在铁质微珠中以四种存在形式：Fe3O4、α-Fe2O3、γ-Fe2O3和Fe3+-玻璃相。这些物相在三个电厂飞灰中呈现出不同的分布特征,反映出不同的燃煤煤种在锅炉中燃烧温度的差异。随着温度的升高,Fe3O4先氧化为γ-Fe2O3,或γ-Fe2O3与Fe3O4的固熔体,然后再转变为α-Fe2O3,当温度超过 1 400 ℃时,Fe2O3又转化为Fe3O4。     

灰中焦对煤灰熔融特性的影响

采用连有电脑－摄像头的煤灰熔融特性测定装置，在Ar气氛下研究了灰中焦对煤灰熔融特性的影响。结果表明，灰中焦对灰熔融特征温度和灰熔融动态特征具有显著影响，影响程度与煤种以及煤焦的质量分数有关。掺焦的灰熔融温度高于不掺焦的熔融温度；掺焦量增加，其灰熔融温度升高。当掺焦量提高至20%时，在接近或高于煤灰熔融温度时由于焦与焦之间通过熔融煤灰的黏结作用形成了不熔骨架，使灰锥高度不再随温度的提高而发生变化，这也是灰锥很难出现或者根本不出现软化温度和流动温度的原因。     

Flame retardancy of polycarbonate enhanced by adding fly ash

We have developed a flame‐retardant polycarbonate resin whose flame retardancy is greatly enhanced by adding fly ash (a by‐product from thermal power plants). Fly ash with comparatively small average particle sizes (<10 µm) raised the flame retardancy of polycarbonate because of the hydrogen bond that forms between the polycarbonate and the hydroxy group on the fly ash surface. This bond primarily improves the heat resistance of the polycarbonate and also isomerizes the polycarbonate to promote carbonization. The polycarbonate with 25 wt% of the fly ash showed good other main characteristics, such as mechanical properties and moldability, comparable to those of a flame retardant polycarbonate reinforced with glass fiber, used for electronic products such as desktop computers, etc. Applying the fly ash eliminates the need to use current retardants such as organic halogen compounds and thus promotes the perceived environmental safety of flame‐ retardant polycarbonate. In addition, being able to use less raw resin by adding the fly ash means that less energy is required to manufacture flame‐retardant polycarbonate. Copyright © 2007 John Wiley & Sons, Ltd.     

Determination of arsenic in fly ash by hydride generation in a slurry

We have studied the generation of arsenic hydride on a fly ash slurry from a thermal power plant burning lignite. The conditions for the formation of the slurry were optimized and the influence of the presence of various surfactants on the formation and stability of slurry (particle size-analytical signal ratio) were investigated.The As content in the ash was 78.7 g/g, with an rsd of 5.6% and a detection limit of 2.8 ng. The proposed method was successfully applied to the determination of arsenic in a certified ash sample (BCR-38). This method was applied to fly ash from a thermal power plant burning anthracite.     

配煤对高熔点煤灰熔融特性影响的研究

采用灰熔点较低的襄阳煤和灰熔点较高的晋城无烟煤组成的混合煤样,利用XRF、SEM、DSC、XRD、三元相图等分析方法,探究了襄阳煤对晋城无烟煤煤灰熔融温度的影响。结果表明,配煤能有效降低高熔点煤灰的熔融温度,当襄阳煤的加入量小于24%时,混合煤灰熔融温度显著降低;襄阳煤的加入量在24%-40%时,混合煤灰熔融温度变化平缓且流动温度低于1 400℃。混合煤灰中的成分在1 000-1 200℃发生一系列的化学反应,主要包括SiO_2与Al_2O_3结合产生高熔点物质莫来石以及Fe_2O_3、CaO与莫来石反应转化形成铁尖晶石、钙长石等新物质,由此造成了煤灰熔融温度的变化。基于BP神经网络对实验数据建立预测模型,其预测效果优于前人总结的经验公式,平均准确度高于99%。利用热力学软件HSC 5.0分析了CaO、Fe_2O_3对降低煤灰熔融温度的影响,分析表明,CaO对莫来石的转化作用优于Fe_2O_3。