固硫灰渣的微观结构与火山灰反应特性

用X射线衍射、红外光谱和扫描电镜研究流化床燃煤固硫灰渣(简称固硫灰渣)的微观结构.用化学反应动力学方法研究固硫灰渣的火山灰反应特性,并与粉煤灰进行对比.阐述了固硫灰渣的微观结构与其火山灰反应特性之间的关系.结果表明:固硫灰渣与粉煤灰矿物组成差异较大,主要体现在它不含莫来石.固硫灰渣中[SiO4]和[AlO6]聚合度均低于粉煤灰的.固硫灰渣颗粒表面比粉煤灰的疏松.固硫灰渣的火山灰反应速率常数明显高于粉煤灰的,而表观活化能相反.固硫灰渣火山灰反应活性明显高于粉煤灰的,反应阻力也较小,这是由其微观结构所决定的.     

流化床燃煤固硫灰渣自硬机理的研究

流化床燃煤固硫灰渣是一种比较特殊的燃煤灰渣,主要特征之一为其明显自硬性,这种特性对其资源化利用有比较大的影响.通过对来源不同的7种流化床灰渣自硬性进行研究,结果显示,经固硫的灰渣具有明显的自硬性,而未经固硫的灰渣则自硬性不明显.采用化学方法确定了固硫灰渣中存在有一定量的C2S和C3A.结果显示,除可溶解的硬石膏与活性Al2O3、游离CaO反应生成钙矾石外,固硫灰渣中的C2S和C3A是其具有自硬性的主要来源.     

固硫灰渣水泥的开发

对循环流化床燃煤固硫灰渣的化学、物理性能和矿物组成作了分析论述。通过技术处理可将固硫灰渣制成脱硫灰渣水泥。水泥胶砂试验证明 :循环流化床燃煤固硫灰渣具有潜在的活性 ,用它制得的水泥可达到 32 .5 #等级(GB134 4 -1999)。     

流化床燃煤固硫灰渣微观结构研究

分别用X射线衍射、红外光谱和扫描电镜研究固硫灰渣矿物组成、硅酸盐阴离子聚合度和颗粒形貌。并与煤粉炉粉煤灰进行对比。结果表明：与粉煤灰不同，固硫灰渣基本不舍莫来石；固硫灰渣[SiO4]和[AlO6]聚合度均低于粉煤灰；固硫灰渣的颗粒形貌极其不规则且疏松多孔。研究发现，固硫剂和生成温度对固硫灰渣微观结构影响很大。     

钢渣-固硫灰渣复合掺合料制备及其性能

钢渣安定性不良及可能含有过多的Cr组分使其作为建筑骨料和作为水泥生料配料使用存在较大的安全和质量风险，这严重限制了钢渣的资源化利用。适量钢渣作为混凝土矿物掺合料已成为钢渣利用的主要领域。本文针对钢渣粉磨能耗高、活性偏低的特点，提出引入高硫高钙的循环流化床固硫灰渣作为转炉钢渣或电炉钢渣稀释剂及改性剂，一方面减少钢渣用量、降低生产能耗；另一方面，以固硫灰渣硫钙组分激发钢渣活性。研究结果表明：钢渣-固硫灰渣复合掺合料能够充分利用钢渣粉需水量低以及固硫灰渣组分激发优势，从而克服了钢渣粉早期活性低和固硫灰渣需水量高、后期强度倒缩问题。所制备钢渣-固硫灰渣达到Ⅱ级复合矿物掺合料技术要求。该复合掺合料大掺量使用钢渣，具有较好的经济和环境效益。     

固硫灰渣的基本特性及其作水泥混合材的关键问题研究进展

固硫灰渣是循环流化床燃煤技术的主要副产物,如何高效、清洁地利用这一类固体废弃物是一个亟待解决的问题。本文根据近年来国内外对固硫灰渣的研究成果,从化学组成、矿物组成、微观结构、典型特性等方面综述了固硫灰渣的主要特征。相较于粉煤灰等其他燃煤副产物,固硫灰渣中存在游离氧化钙、硫酸钙和无定形铝硅酸盐物质,且颗粒疏松多孔,这导致其具有明显的火山灰活性、自硬性和水化膨胀性等特性。同时本文分析了固硫灰渣作为水泥混合材使用时需要注意的几个关键问题。结果表明,固硫灰渣特殊的组成、微结构和性质导致其作为水泥混合材使用时,必须考虑使用合适的激发剂提高灰渣活性,调整养护工艺、用水量等条件提高制品的安定性,并以添加减水剂等方式控制水泥制浆中的需水量,提高水泥石强度。这为有效实现固硫灰渣的建材资源化利用提供一定指导。     

流化床燃煤固硫灰渣的特性

流化床燃煤固硫灰渣(固硫灰渣)是一类特殊的燃煤灰渣.用11种来源不同的固硫灰渣,研究了需水性、自硬性和膨胀性.结果显示:同硫灰渣因为颗粒表面疏松多孔,具有非常强的吸水性,标准稠度需水量达到粉煤灰的2倍;固硫灰和固硫渣具有明显的自硬性,28d净浆抗压强度可达到10MPa;固硫灰渣具有明显膨胀特性,这种不良的安定性主要来自固硫组分.     

固硫灰渣的特性及其与现行标准的适应性

循环流化床燃煤固硫灰渣的量越来越大,其利用的迫切性增加,加强对固硫灰渣特性的研究和认知,建立或完善其特性表征评价体系、相关参数测试方法是重要的基础工作.在总结流化床燃煤灰渣的化学组成、矿物组成、物理特性以及其成因和影响因素的基础上,探讨了其特性表征评价体系和相关参数测试方法,并讨论了这些测试方法与现行标准的适应性与原因.依据固硫灰渣的特性,提出了更适合其火山灰活性测定的"改进水泥熟料28 d抗压强度比法",并改善了测试固硫灰渣f-CaO含量、需水量比和SO3含量的测试方法.     

固硫灰渣的活性评定与现行标准的适应性研究

循环流化床固硫灰渣在矿物组成、化学成分等方面与煤粉炉粉煤灰存在显著区别,两者活性来源也不相同。现行标准中的火山灰活性评定方法主要针对的是低硫火山灰,而固硫灰渣中硫含量较高(以SO3计可高达10%以上),现行标准是否适合用来评价固硫灰渣活性存在疑问。对固硫灰渣与现行标准中的两种火山灰活性评定方法的适应性进行了研究,结果显示:"水泥胶砂28 d抗压强度比试验"不适合用来评定硫含量较高的火山灰质材料的活性;准确测定固硫灰渣的活性需改进现行试验方法。     

燃煤灰渣活性差异及来源研究

粉煤灰、沸腾炉渣和固硫灰渣是三种具有代表性的燃煤灰渣,因生成方式与生成温度不同,火山灰活性存在较大差异。本文采用改进的28 d抗压强度比方法研究其活性差异,并在矿物组成及颗粒形貌等方面探讨活性差异来源。研究结果显示:沸腾炉渣和固硫灰渣活性相近,明显高于粉煤灰;不同种类燃煤灰渣的活性差异主要来源于其矿物组成及颗粒形貌差异。     

流化床燃煤固硫灰渣膨胀控制因素研究

分别用线性膨胀率和XRD研究固硫灰渣净浆试件的膨胀特性和固硫灰渣水化产物随龄期变化趋势,并在结合二者试验结果的基础上对膨胀控制因素进行探讨。结果显示:固硫灰渣净浆试件的线性膨胀率在14～28 d前增加迅速,而后趋于平缓。试验表明,固硫灰渣的膨胀特性可分为两个阶段:14～28 d前主要受钙矾石量所控制,而随后龄期则主要受二水石膏量所控制。     

X-ray powder diffraction-based method for the determination of the glass content and mineralogy of coal (co)-combustion fly ashes

The relevance of Al-Si glass in a number of fly ash applications, such as use as a pozzolanic material, zeolite synthesis, and geopolymer production, necessitated research towards investigation of methods for an easy and consistent determination of the glass content in this coal (co)-combustion by-products. A glass standard-addition X-ray powder diffraction (XRD)-based method is proposed in this study as an alternative to the non straightforward procedure of conventional methods for determining the amorphous components, mainly by difference of the total mass and the addition of quantified crystalline species. A >99% Al-Si glass slag sample was selected as a standard for glass. A number of glass standard/fly ash mixtures were performed on Fluidized Bed Combustion (FBC) and pulverized coal combustion (PCC) fly ashes and subsequently analyzed by XRD. The method provides results closer to quantitative proportions of the Al-Si amorphous material of this (co)-combustion by-product, with a range of values <3% when compared with those obtained by the conventional Reference Intensity Method (RIM) method, demonstrating suitability and consistence of the procedure. Furthermore, by the proposed method, the requirement of previous determination of the mineral phases of conventional techniques is avoided. Coupled with the easy calculations, this allowed a fast determination of the glass content of (co)-combustion fly ash. The mineralogy of FBC and PCC fly ash was also investigated using the RIM method. The occurrence and proportions of the crystalline components in fly ash are in line with the combustion technology and their inherent operational parameters, especially the (co)-combustion temperature. The FBC fly ash shows the highest content of relic phases from feed coal (quartz, illite, calcite, and feldspars) and lower contents of amorphous components. The PCC fly ash are characterized by the highest proportions of mullite and Al-Si glass and low contents of quartz an other relict phases. The occurrence and distribution of anhydrite and Fe-oxide species appears to be related to the content of Ca and Fe in the feed fuels, showing slightly higher contents in FBC than in PCC fly ash.     

流化床燃煤固硫灰渣体积稳定性及影响因素研究

采用检测固硫灰渣净浆试件线性膨胀率方法表征其体积稳定性,并对影响因素进行分析。结果显示:固硫灰渣净浆试件的线性膨胀率在14～28d龄期前迅速增加,而后增长幅度明显变缓;固硫灰的膨胀特性明显低于固硫渣;固硫灰渣体积稳定性主要决定于游离氧化钙(CaO)含量而非三氧化硫(SO3)含量。     

Speciation of mercury in fly ashes by temperature programmed decomposition

Mercury (Hg) is a toxic trace element which is emitted mostly in gas phase during coal combustion, although some Hg compounds may be retained in the fly ashes depending on the characteristics of the ashes and process conditions. To improve the retention of Hg in the fly ashes a good knowledge of the capture mechanism and Hg species present in the fly ashes is essential. The temperature programmed decomposition technique was chosen to identify the Hg species present in fly ashes obtained from two Pulverized Coal Combustion (PCC) plants and a Fluidized Bed Combustion (FBC) plant. The fly ashes were then used as Hg sorbents in a simulated flue gas of coal combustion and gasification. The Hg compounds found in the fly ash from the FBC plant after elemental mercury retention were mainly HgCl₂ and HgSO₄. The Hg species present in the two fly ashes from the two PCC plants were HgCl₂ and Hg⁰. The Hg species formed in the coal gasification atmosphere was HgS for all three fly ashes. The only Hg compound identified in the fly ashes after the retention of mercury chloride was HgCl₂.     

固硫灰渣中无水石膏分布规律研究

流化床燃煤固硫灰渣(简称固硫灰渣)中的硫元素多以无水石膏形式存在。本文采用筛分和密度分离的方法,测定固硫灰渣中不同粒径及不同密度组分中的无水石膏含量。研究结果显示:固硫灰渣中的无水石膏易富集在粒径小、密度大的颗粒中。     

燃油锅炉灰垢的烧结成因及其对策

介绍了燃油锅炉灰垢的成分及其烧结成因。发现灰垢中SO含量很大,且其酸性和Fe含量均随取样点温度的升高而降低。当灰垢中组分发生化学反应时,由于离子扩散遣率加大而位烧结程度加重。清灰刘应该具有助燃、防烧结和减轻位温及高温腐蚀的作用。研制清灰剂时要加意考察清灰剂中每个组分的作用,天好过免使用易生成低熔点化合物的成金属化合物。文中还介绍了新研制的清灰剂在实验室和工业装置上的清灰效果。     

The effect of particle shape on the pressure drop across the dust cake

In order to observe the effect of particle shape of poly-dispersed dusts on filter performance, the pressure drop across the dust cakes of fly ashes from a conventional power plant (PC), fluidized bed combustion (FBC), and paint incinerator (FI) was measured over a metal filter element in the accurate conditions. A fluidized bed column was used to prepare the dust feed stream of uniform particle distribution. The fine particles of FI ash have a tendency to be agglomerated at low transport velocity. The aggregates were broken at high velocity of more than 21 cm/sec. FBC ash composed of jagged type particles and containing high concentration of unburned-carbon showed higher pressure drop than that of PC ash composed mostly of spherical particles. FI ash composed of aggregates of very fine carbon particles presented the highest pressure drop among the fly ashes tested. The shape factors of PC, FBC, and FI ash were estimated as 0.91, 0.76, and 0.65, respectively, by the Ergun equation. The results implied that the irregular particle tends to form a higher pressure drop and to be more compressible than spherical one. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University.     

Biodesulphurization of a coal by packed-column leaching. Simultaneous thermogravimetric and mass spectrometric analyses

This study has two aims: to improve the biodesulphurization of a semi-anthracite by packed-column leaching by reducing the insoluble sulphate on the coal surface, and to determine whether after the combustion of treated and untreated coal, sulphate sulphur is transformed completely into sulphur dioxide or part remains in the ashes without reacting. Combustion tests were analysed by TG-MS. To reduce the precipitation of salts, two parameters are worked on: solution pH, which is reduced to 1.3, and the idle time between washes (ITBW), which is altered. After 125 days of treatment, comparison with the results of previous studies showed that the precipitated salt content was reduced pyritic desulphurization was increased up to 43%, and total desulphurization to 24%.