Effects of fly ash and bottom ash on the frictional behavior of composites

Immense quantities of coal combustion by-products are produced every year, and only a small fraction of them are currently utilized. Our recent work has focused on developing value-added products especially from fly ash, bottom ash, and flue gas desulfurization (FGD) scrubber sludge. We explored the potential utilization of fly ash, bottom ash, and sulfate-rich scrubber sludge as frictional modifiers and additives for automotive frictional composites. The surfaces of the frictional composites, fabricated from scrubber sludge and fly ash or bottom ash, were characterized with the help of scanning electron microscopy (SEM). The mechanical properties of by-products containing composites were evaluated using a dynamic mechanical analyzer (DMA). The frictional behavior of the composites was probed with the help of friction assessment and screening test (FAST). The frictional results suggested that fly ash or bottom ash had a profoundly different effect on the frictional coefficient (μ) and wear of the composite than those observed for scrubber sludge particles. It appeared that fly ash or bottom ash particles had abrasive characteristics and gave frictional composites a higher μ-value. The FAST test also revealed that the fluctuations in the μ-value were a minimum for composites that contained 20 vol% fly ash or bottom ash among the ash-derived composites. The composites that contained 30 vol% fly ash or bottom ash showed fade after approximately 60 min of continuous FAST test. We compared the frictional and wear performance of our composites with a commercial automotive brake, and it appeared that frictional composites could be formed which contained up to 20 vol% fly ash or bottom ash and 25 vol% scrubber sludge.     

粉煤灰在燃煤锅炉烟气脱硫中的应用

简述了大气中SO2污染物的排放现状,“十二五”期间的减排目标及粉煤灰的结构特性。介绍了国内外复合型粉煤灰脱硫剂的制备工艺、脱硫工艺及机理、工业应用状况等,论述了燃煤锅炉自身粉煤灰直接用于尾部烟气的干法或半干法脱硫工艺的研究现状。对粉煤灰脱硫剂在烟气脱硫技术方向的应用前景进行了展望。     

Verification of lime and water glass stabilized FGD gypsum as road sub-base

Flue gas desulfurization (FGD) gypsum is a by-product created when sulfur is removed from flue gases in power plants. The utilization of FGD gypsum as a road sub-base for construction purposes is unsatisfactory when compared with other by-products such as fly ash and steel slag. As a result, FGD gypsum has generally been treated as a waste product and landfill. A new type of semi-rigid road sub-base is proposed, which is a mixture of FGD gypsum, water glass and slaked lime. Laboratory studies of moulded samples of this new material were investigated using different curing methods and measuring unconfined compressive strength, soundness and water stability. The experimental results showed that the road sub-base material reflects excellent mechanical properties and soundness durability. This contributes not only to improved road performance, but also represents a new and improved beneficial use of FGD gypsum.     

320MW燃煤电厂痕量元素的分布、脱除及排放特性

燃煤电厂痕量元素的排放已经引起了世界的广泛关注。在一台配置选择性催化还原（SCR）+静电除尘器（ESP）+湿法脱硫装置（WFGD）的320MW燃煤电厂上进行了12种痕量元素（Cr、Mn、Co、Ni、Cu、Zn、As、Mo、Cd、Sb、Ba、Pb）排放特性的实验研究,使用了US EPA Method 29对4个测点烟气痕量元素进行同时取样,考察了痕量元素在电厂中的分布、协同脱除以及在烟囱中的排放。结果表明：锅炉、SCR、ESP、WFGD和整个系统的痕量元素质量平衡率均在可接受的范围内。这12种痕量元素主要分布在底渣和飞灰中,分别占据底渣、ESP灰、WFGD脱除及烟囱排放痕量元素总量的1.90%～27.6%和72.3%～98.0%,然而,它们在烟囱和被WFGD脱除的部分所占比例较少,两者之和仅占0.11%～0.66%。ESP和WFGD对烟气痕量元素的脱除率分别为99.39%～99.95%和40.39%～78.98%,SCR+ESP+WFGD对烟气痕量元素的总体脱除率为99.79%～99.99%。ESP对痕量元素较高的脱除效率是APCDs系统具有较高的协同脱除效率的主要原因。烟囱排放的痕量元素浓度及排放因子分别为0.01～12.88 μg·m^-3和（0.002～4.57）×10^-12 g·J^-1。应进行更多的燃煤电厂痕量元素排放的研究,以便为中国燃煤电厂痕量元素的排放预测模型的建立以及相关标准的制定提供参考。     

粉煤灰在环境污染治理中的应用

综述了粉煤灰在环境污染治理中的应用,包括烟气脱硫、废水处理以及污泥利用和土壤修复,并介绍了粉煤灰在环境应用中的作用原理。尽管粉煤灰在环境治理中的许多应用还处于试验阶段,但已取得了较好的效果,有着广阔的发展前景。     

混燃石油焦循环流化床锅炉硫污染物排放特性

在3台配备了炉内脱硫+静电除尘器（ESP）/布袋除尘器（FF）+湿法脱硫装置（WFGD）的410 t·h^-1循环流化床（CFB）锅炉进行了硫污染物排放特性研究。在3个测点采用US EPA Method 8对烟气中不同形态硫污染物进行了平行取样,并同时采集了相应工况下入炉燃料、石灰石、底渣、飞灰、石膏和废水等,考察了污染物控制装置对硫污染物的影响以及硫在电厂的迁移和分布特性。结果表明,锅炉出口烟气中硫主要以颗粒态硫和SO₂的形式存在,占比分别为48.94%～55.05%和44.14%～49.07%。ESP和FF能高效脱除颗粒态硫,脱除效率均达95%以上;WFGD对SO₃/硫酸雾、颗粒态硫的脱除效率分别达62.66%～67.82%和53.06%～60.89%。燃料中硫经过燃烧和污染物控制装置脱除之后绝大部分迁移至灰渣（底渣+飞灰）和湿法脱硫产物（石膏+废水）中,分别占硫总输出的56.79%～70.12%和29.25%～41.70%,只有0.63%～1.51%的硫排放到大气环境中。     

Mercury speciation and emission from the coal‐fired power plant filled with flue gas desulfurization equipment

Mercury speciation and emission from two Chinese coal‐fired power stations equipped with flue gas desulfurization device were investigated. Research results reveal that Hg⁰ is the main form in the flue gas in Plant 1; Hg²⁺ is the main form in the flue gas in Plant 2. Most of mercury was emitted to the atmosphere, which was about 77–98%, and the elemental mercury released to atmosphere ranged 73–94% approximately. A pot of mercury is adsorbed by bottom ash, electrostatic precipitator (ESP) ash, and gypsum in Plant 1. However, most mercury, the scale of which is 75–83.2%, is collected by ESP ash, and only 7.0–12.2% mercury is emitted to the atmosphere in Plant 2. The mercury removal by NID semi‐desulfurization system is higher than wet flue gas desulfurization (WFGD) desulfurization system.     

火电厂钙型烟气脱硫产物的建材利用

介绍了以石灰石/石灰作为火电厂烟气脱硫吸收剂时,不同脱硫工艺所得脱硫产物的差异,并就它们在建筑材料工业中的应用情况作了论述。     

Speciation of As, Cr, Se and Hg under coal fired power station conditions

Coal combustion from power stations is an important anthropogenic contributor of toxic trace elements to the environment. Some trace elements may be emitted in range of valencies, often with varying toxicity and bioavailability. Hence, determination of trace element speciation in coals and their combustion products is important for conducting comprehensive risk assessments of the emissions from coal-fired power stations. This study focuses on speciation of selected trace elements, As, Cr, and Se, in coal combustion products and Hg in flue gas, which were sampled at one Australian power station. Different analytical methods such as secondary ion mass spectrometry (SIMS), ion chromatography-inductively coupled plasma mass spectrometry (IC-ICPMS) and X-ray absorption near edge structure spectrometry (XANES) were used to determine trace element speciation in coal and ash samples. Results showed that As, Cr and Se are all present in a range of valency states in coal. Concentrations of As and Se in the bottom ash as well as the more toxic hexavalent chromium were less than the detection limits. The more toxic As³⁺ form in fly ash was at 10% of the total arsenic, while selenium was mainly found in Se⁴⁺ form. Hexavalent chromium (Cr⁶⁺) in fly ash was 2.7% of the total fly ash chromium. Mercury speciation in flue gas was determined using the Ontario Hydro sampling train and analysis technique. Approximately 58% of the total mercury in flue gas was released in the elemental form (Hg⁰), which, among all mercury species, has the highest residence time in the environment due to lower solubility. This work summarises the performance of the selected analytical techniques for speciation of trace elements.     

喷涂聚脲在烟囱内衬防腐中的应用

电厂烟囱排放的烟气必须进行脱硫处理,但目前国内各电力系统通常采用湿法脱硫,用此法脱硫后的烟气环境(低温、高湿)导致腐蚀状况进一步加剧。传统的防腐工艺由于材料自身性能的缺陷,不适应烟囱脱硫后的防腐要求,喷涂聚脲弹性体技术是一种新型无溶剂无污染的施工技术,可以很好地满足烟囱防腐的要求。     

钙基烟气脱硫剂的生产研究进展

由飞灰/Ca(OH)2水合反应而制备钙基脱硫剂是目前在干法/半干法锅炉烟气脱硫工艺听 一个主要研究内容，介绍了国内外在高效钙基脱硫剂生产研究方面的进展，并就脱硫机理进行了阐述，对进一步研究和开发高效脱硫剂提出了自己的看法。     

湿法脱硫净烟气中的细颗粒物对膜吸收CO2的影响

在使用膜吸收装置脱除燃煤电厂尾气中二氧化碳的实际应用中,膜吸收二氧化碳系统装配于湿法烟气脱硫系统(WFGD)出口是最适宜的选择。经过湿法脱硫的烟气中含有一定量的细颗粒物,这些颗粒物可能会影响膜的性能,因此有必要揭示细颗粒物对膜吸收二氧化碳的影响。本文采用模拟实验装置,选取飞灰、硫酸钙、硫酸铵3种颗粒物,考察了它们对聚丙烯(PP)中空纤维膜吸收二氧化碳的影响。结果表明:3种颗粒物通过膜组件时,均会在膜表面沉积,导致二氧化碳脱除效率下降;膜吸收二氧化碳的性能与颗粒物沉积程度呈负相关;3种颗粒物对膜吸收二氧化碳的影响程度从大到小依次为硫酸钙、硫酸铵、飞灰;颗粒物在膜表面沉积后很难被气体反吹,这会使膜基本失效。     

粉煤灰负载的钙基脱硫剂的制备

针对目前干法烟气脱硫工艺吸收剡利用率低、用量大等问题,开发以粉煤灰、Ca（OH）2、活化剂为主要原材料,通过固相反应／水热化合反应过程制备粉煤灰负载的高效钙基脱硫剂,其脱硫效果采用流动床气一固催化测试装置测定,脱硫率可达93％。     

The effect of fly ash on fluid dynamics of CO2 scrubber in coal-fired power plant

Uncaptured fly ash and/or suspended solids from wet flue gas desulfurization (WFGD) scrubbing solutions are one of several factors that will influence the performance and robustness of carbon dioxide capture systems in coal-fired power plants which will be installed prior to the exhaust stack. In this study, a 100 mm ID packed column scrubber was tested with different concentrations of ash in various chemical solutions to evaluate the influence of solids on the fluid dynamics of the packing material. Data reported here are collected from three solutions including water, 30 wt% MEA (monoethanolamine), and 20 wt% potassium carbonate. The packing selected for this study was a 16 mm polypropylene pall rings. Compressed air was used to simulate flue gas at near ambient temperature and pressure.     

Influence of flue gas conditioning on fly ash characteristics

In this technical note an effort has been made to investigate the influence of flue gas conditioning, FGC, on physical, chemical, mineralogical and morphological characteristics of the fly ash. FGC is a technique that involves addition of chemical additives to the flue gas, for increasing the ash collection efficiency of electrostatic precipitators, ESPs. The FGC also helps in reducing the amount of suspended particulate matter, SPM, which is released into the surrounding environment at thermal power stations. It is a well established fact that utilization of the fly ash, as a cementitious material, depends on its pozzolanic characteristics, which in turn pivots on its physico-chemico-mineralogical and morphological characteristics. However, how these characteristics get influenced due to FGC has not yet been reported in the literature. With this in view, ash samples from a coal-fired thermal power station in India, where flue gas conditioning is being employed, were collected and their physico-chemico-mineralogical and morphological properties were examined. Based on these studies efforts have been made to highlight the influence of FGC on ash characteristics.     

Trace element partitioning during the firing of washed and untreated power station coals

The effect of coal washing on trace element content and combustion behaviour of four world-traded coals has been studied at rig scale. The inputs and process outputs from a 1 MW combustion test facility, including coal, bottom ash, suspended fly ash, retained ash and flue gas, have been analysed for a standard suite of 17 trace elements. The results suggest that although coal cleaning significantly reduces the total ash content of the coal, the concentrations of individual trace elements are not reduced proportionately. Combustion of the washed coals resulted in increased concentrations of trace elements in the fly ash, although total fly ash loadings were reduced. Cleaning appeared to have little effect on concentrations of gaseous trace elements in the flue gas. The partitioning of the more volatile trace elements such as mercury and selenium between the vapour and solid phase was influenced by the amount of excess oxygen in the furnace, presumably affecting carbon-in-ash levels.The results suggest that the coal cleaning undertaken for these experiments did not significantly reduce the emissions to atmosphere of trace elements. The ultimate emissions will be determined by the efficiency of the dust capture systems.     

Composition and size distribution of particules emissions from a coal-fired power plant in India

Particulate matter in fly ash from ESP inlet and outlet of a coal fired power plant in India was measured for five units of 120 MW and 210 MW of the power plant. Samples of the pulverised coal and bottom and fly ashes were also collected. The size distribution and chemical composition of particulate matter were determined using a laser particle analyser, an ion chromatograph (IC) and an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The observed particle mass concentration at the ESP inlet was 5443–21483 mg Nm⁻³ whereas the outlet concentration was found as 12–315 mg Nm⁻³ thereby giving total removal efficiency of 95.7–99.8%. A fine particle mode appeared at the particle size of 0.4–0.9 μm and coarse particle mode appeared at the particle size greater than 1 μm. Magnesium and iron remained in bottom ash and showed high concentrations 99 and 2154 μg g⁻¹ (ppmw) respectively, while other elements such as lead, chromium and zinc were observed in higher concentration in ESP inlet flue gas. Relative enrichment of trace elements (except Fe) in fly ash was observed higher than that in bottom ash.     

脱硫烟气干燥粉煤灰的闪蒸干燥器结构确定

简介了关注燃煤热电厂湿排粉煤灰的意义。以脱硫烟气作为加热介质,选择旋转闪蒸干燥器干燥粉煤灰,对旋转闪蒸干燥器进行了工艺设计和结构设计。所设计的旋转闪蒸干燥器能满足干燥粉煤灰的要求。     

粉煤灰综合利用现状

随着煤炭资源利用量的增加,粉煤灰排放量呈现逐年增加趋势,根据灰色预测模型估计到2020年中国粉煤灰排放量将达到9亿t。如何利用好粉煤灰,减少环境污染,减少占地面积,增加工业产值等是普遍关注的问题。在对粉煤灰物理化学特性概述的基础上,对粉煤灰的综合利用进行了归类,并从农业（土壤改良、肥料）,建材（混凝土、砖块、水泥、砂浆、陶粒、泡沫玻璃、拒水粉等）,化学工业（提取铝元素、合成分子筛、橡塑复合材料、造纸）,环保（污水处理、烟气净化）等方面进行分类阐述,对粉煤灰的利用方向提出了建议。     

钢渣-粉煤灰复合胶凝材料的试验研究

以钢渣、粉煤灰等固体废物,掺加少量的普通硅酸盐水泥、脱硫石膏,辅以适量化学激发剂,研制开发新型复合胶凝材料。试验表明,少量水泥能够有效地激发出钢渣-粉煤灰体系潜在的活性,单掺水泥的钢渣-粉煤灰体系最优配比为:钢渣/粉煤灰=6:4,水泥掺量为15%;对于复掺水泥和脱硫石膏的钢渣-粉煤灰体系来说,最优配比为钢渣/粉煤灰=6:4,水泥掺量为15%,脱硫石膏掺量为10%。合适的化学激发剂可以较好地提高复合胶凝材料的性能,复合胶凝材料在自然养护的条件下比标准养护条件下强度增长更快。