煤中矿物质及其燃烧后的变化分析

以淮北煤田6煤层煤为样品，采用中子活化法、化学方法、X射线衍射及扫描电镜等方法对煤及其灰样品中的矿物质、微量元素进行了分析，在此基础上，研究了样品中主要矿物的种类及其形成时的影响因素，分析了它们在燃烧前后的主要变化。通过分析可知，样品中主要含有高岭石、石英、方解石和黄铁矿以及多种微量元素；在燃烧过程中，微量元素的含量以及矿物的种类发生了变化，并形成高温稳定的矿物种类。     

煤中微量元素在燃烧过程中的变化

在分析微量元素燃烧过程中迁移变化机理的基础上,对电厂用煤和煤灰进行了采样测试,分析了电厂燃煤过程中微量元素的析出变化及在各种灰中的分布富集规律,同时用五个不同的温度段分别对煤进行了燃烧实验,研究了在不同温度下,微量元素从煤中析出的浓度和析出率,通过实验分析,。多数有害微量元素在飞灰中的富集浓度高于其它灰中,燃烧时温度的高低是影响微量的高低是影响微量元素迁移析出的重要因素,温度越高,有害微量元素析出率相对越大。     

Studies on the pozzolanic and hydraulic properties of fly ashes in model systems

In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on cement pastes with mentioned ashes. The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR). Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca²⁺ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher reactivity compared to other ashes from pulverized combustion. Pozzolanic and hydraulic properties of this ash were also confirmed. Differences in the behaviour of ashes originating from pulverized combustion of various types of coal in the presence of water and Ca²⁺ rich environment were demonstrated.     

水煤浆燃烧炉内固体残留物的微观分析

以不同特性煤浆的炉内燃烧固体残留物为研究对象，对取自炉内不同部位及沉积于硅碳棒和灰污探针上的典型燃烧灰的化学成分、矿物组成、元素分布及微观结构等进行分析研究。结果表明，水煤浆灰样中含Al、Fe、Ca的化合物和矿物的质量分数高于黑液浆，Na、K、S、Cl的情况与此相反。Fe的富集是造成水煤浆沾污结渣的根本原因。Na和Fe是引起黑液浆沾污结渣的主要矿物元素，Na的作用比Fe更大。黑液浆灰样中含有大量的霞石和硫酸钠等低熔融温度富钠化合物，Na是引起沾污结渣的根源。微观分析结果与实际燃烧状况是一致的，黑液浆结渣特性强于水煤浆，并且二者的灰沉积机理是不同的。     

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。     

660MW燃煤机组锅炉飞灰颗粒物排放特征研究

应用自动烟尘测试仪在沙角C电厂1#炉静电除尘器前进行飞灰颗粒物采集,分析了煤种、负荷对飞灰细颗粒排放特性的影响,同时对飞灰颗粒粒径分布、化学成分、矿物含量和形貌特征等进行了研究。结果表明,机组负荷越高,飞灰颗粒越细,生成的PM1和PM2.5越多,但总的烟尘排放浓度随负荷升高而降低;随着伊泰煤的掺烧比例增大,飞灰颗粒粒径分布向细颗粒区域移动,PM1和PM2.5的含量增大。低负荷时易形成含有熔融小球体的煤胞结构,高负荷时易形成多孔煤胞。高低负荷和不同配煤的燃煤颗粒物矿物成分类似。     

不同灰化温度下生物质混煤灰的烧结特性研究

选取晋城无烟煤和麦秆作为研究对象,利用压差法烧结温度测定装置测量不同灰化温度下煤和麦秆混合灰的烧结温度,再利用SEM-EDS以及XRD对灰样进行烧结特性分析。结果表明,不论灰化温度高低,随着麦秆的添加,煤和麦秆混合灰的烧结温度都呈现降低趋势,其降低幅度略有差别。灰化温度较低时,煤和麦秆混合灰的烧结温度低于灰化温度较高情况下混合灰的烧结温度。SEM-EDS分析表明,低温灰化得到的样品中出现较多不规则的纤维结构;较高温度下获得的灰样中出现较多致密的球状颗粒,这表明矿物质发生熔融形成球状颗粒。XRD分析表明,低温灰化烧结后的煤和麦秆混合灰样中因含有较多的含钾等碱金属系助融矿物质,导致混合灰样的烧结温度降低。然而,像钙长石等含钙矿物质本身具有较高的熔点,因此,在1 100℃时混合灰样具有较高的烧结温度。     

燃烧福建无烟煤的循环流化床锅炉飞灰及其未燃炭分析

以三个燃烧福建无烟煤的商业CFB锅炉电厂飞灰为研究对象，分析飞灰的粒径和含碳量分布；观察并区分了飞灰中煤炭、烟怠、半焦和灰渣等颗粒的表面形貌；测定了飞灰炭的反应活性并与入炉煤作比较；并研究了飞灰炭的来源。结果表明，采用单级分离装置的CFB锅炉，粒径在0.0385mm～0.0500mm的飞灰质量最多，未燃炭份额也最高；而采用双级分离装置的CFB锅炉，飞灰质量分布和飞灰炭份额的峰值则出现在粒径为0.0500mm~0.0750mm处。飞灰主要由三种形貌的颗粒组成，颗粒状的未燃炭、絮团状的灰渣、和介于两者之间的半焦。与入炉煤相比，飞灰炭的反应活性较高，主要来源于入炉煤中的细粉和燃烧早期因破碎和磨蚀而产生的、来不及在炉膛中燃尽的细小含炭颗粒。入炉煤中易破碎、反应性较高的亮煤是构成电厂CFB锅炉飞灰炭的主要成分。     

Sewage sludge ash as an alternative low-cost oxygen carrier for chemical looping combustion

In this paper, novel low-cost oxygen carriers containing Fe₂O₃ are evaluated for use in chemical looping combustion. Sewage sludge ashes and reference samples were prepared and used in cyclic reduction and oxidation experiments in a thermogravimetric analyzer (TG). A gaseous (3 % H₂) fuel and a solid fuel (hard coal) were tested. Three-cycle CLC tests were carried out in the 600–800 °C temperature range and long-term testing was performed at 950 °C. A reactivity study showed that the natural sewage sludge ash sample was stable during the cycling TG tests when hydrogen was used as a fuel at all of the temperatures investigated. Strong temperature effects on the oxygen transport capacity were observed. An one-cycle test at 900 °C showed also that the sewage sludge ash successfully reacted with coal. The oxygen released was fully used for coal combustion, with appreciable reaction rate at temperature of ~750–800 °C, that is significantly lower than that obtained for pure Fe₂O₃-based oxygen carrier. The oxidation reaction was much faster than the reduction reaction. Moreover, the sewage sludge ash showed a low tendency toward agglomeration in the cyclic test, which was superior to the behavior of synthetic materials. The sewage sludge ash exhibited also high mechanical strength, an attrition index of 1 % and a high-temperature resistance of 1,170 °C in a reducing atmosphere. We conclude that sewage sludge ash can be effectively used as a low-cost, valuable oxygen carrier in practical application in chemical looping combustion technology for power generation.     

Investigations of the influence of different fly ashes on cement hydration

Investigations of physico-chemical properties of three kinds of fly ash and their influence on cement hydration were performed in this work. Thermal analysis, microcalorimetry, infrared absorption and others were used. It was confirmed that the kind of coal and combustion conditions essentially influence physico-chemical properties of fly ash and in consequence influence cement hydration. Investigated fly ashes show in cement system so-called pozzolanic activity. Fly ash from combustion of brown coal in fluidized furnace revealed better activity compared to other investigated ones. This work is an introduction to more extensive investigation of fly ash activation.     

Laser Induced Breakdown Spectroscopy application for ash characterisation for a coal fired power plant

The aim of this work was to apply the LIBS technique for the analysis of fly ash and bottom ash resulting from the coal combustion in a coal fired power plant. The steps of presented LIBS analysis were pelletizing of powdered samples, firing with laser and spectroscopic detection. The analysis “on tape” was presented as an alternative fast sampling approach. This procedure was compared with the usual steps of normalized chemical analysis methods for coal which are coal calcination, fluxing in high temperature plasma, dilution in strong acids and analyzing by means of ICP-OES and/or AAS.     

淮南煤灰中晶体矿物组成与煤灰流动温度关系的研究

选取10种不同灰熔融温度的淮南煤,利用典型煤灰化学组成预测煤灰熔融温度的经验公式,对其煤灰流动温度进行了研究,发现预测精度不高;借助X射线衍射K值法分析计算了淮南煤灰的晶体矿物组成,并对晶体矿物组成与淮南煤灰流动温度的关系进行了关联,提出了利用晶体矿物组成预测煤灰流动温度的回归公式,揭示了淮南煤灰中晶体矿物组成与煤灰流动温度的内在关系,利用该公式计算的煤灰流动温度与实测值之差的绝对值小于国标规定的误差值(再现性小于等于80℃)。     

A new luminol chemiluminescence reaction using a tetravalent nickel-periodate complex as the oxidant

A modified sequential extraction procedure was developed and applied to characterize the species of metals in fly ash. Two fly ash samples were collected from a coal-fired thermal power plant located in the north of China. A sample was collected from the conventional pulverized coal (PC) combustor and another from the circulating fluidized bed (CFB) combustor. After extraction by the proposed sequential extraction procedure, the elements in the fly ash samples were divided into a water-extractable fraction (F1), an acid-soluble fraction (F2), a reducible fraction (F3), an oxidizable fraction (F4) and a residual fraction (F5). Except for Cu, V, Cd in the PC sample and V, Zn in the CFB sample, most of the other metals were present in the residual fraction (F5), which was very difficult to release into the environment. The fraction distribution patterns in the two samples were also compared. The results indicated that the distribution of metals in different fractions in fly ash samples were probably impacted by different combustion processes.     

不同灰成分的低熔点煤灰熔融性调控机理研究

通过灰熔点较低且接近的两种煤与灰熔点较高的天池煤混配,结果表明,在含铁类矿物质较低的小屯煤与天池煤的混煤中,混煤灰熔点随天池煤混入比例的增加而提高,含铁类矿物质较高的宁鲁原煤与天池煤的混煤灰熔点随天池煤混入比例的增加没有明显变化。通过XRD分析配煤中矿物质的转变过程,结果表明,宁鲁原煤灰中含有的钙铁类矿物质(如赤铁矿、硬石膏)抑制了莫来石的生成,缺少作为骨架支撑作用的高熔点莫来石,煤灰的熔点得不到显著提高。最后将配煤在沉降炉中进行实验模拟电站锅炉的结渣过程,并使用SEM分析灰渣的微观形貌,发现与宁鲁原煤相比,小屯与天池煤的混煤更能显著改善结渣特性。     

A study of the chemical forms or species of manganese found in coal fly ash and soil

The chemical speciation of manganese of environmental and toxicological interest was undertaken in coal fly ash and soil. Hard coal used in combustion creates considerable quantities of waste ash. The greatest quantities of industrial ashes are stored in the form of waste-heaps, which create a serious problem as the source of inorganic pollution. It is necessary to identify physical and chemical properties of ash, especially when analyzing the pollution of soil by trace metals, which are potentially mobile in environment. In this work, a new analytical method has been developed and used successfully for identification and determination of chemical forms of manganese in coal fly ash and soil. The basic chemical forms of metals contained in the environmental samples (fly ash and soil) can be described by using sequential extraction method. To identify Mn ions, the UV-VIS spectrophotometric method was used by means of comparative analysis of spectrophotometric spectra of appropriate Mn ions in the standard solutions and solutions obtained after extraction. The concentration of manganese in all solutions was determined by the Flame Atomic Absorption method. The experimental approach and analytical method developed in this study appear adequate for this purpose and can therefore be used for similar research.     

Trace elements of coal,coal ashes and fly ashes by activation analysis with short-lived nuclides

On irradiation with neutrons, some of the interesting trace elements in coal, coal ash and fly ash produce short-lived nuclides which may be determined—together with some of the matrix elements—by activation analysis. This enables the characterization of samples. To find out the distribution of elements in the gaseous or aerosol exhaust of fossil-fired power plants, we simulated the combustion in a quartz apparatus containing a cold trap, using the combustion temperature (780 °C) employed for the standard ash determination. High Se values were found in the cold trap deposits from black coal from Poland. Halogens were also found in the deposits.     

Assessment of coal and ash environmental impact with the use of gamma- and X-ray spectrometry

Gamma-ray spectrometry (GS), energy dispersive X-ray fluorescence (EDXRF) analysis methods and wavelength dispersive X-ray fluorescence (WDXRF) were applied for the studies of some coal components, e.g., sulphur, light and heavy metal element concentrations and naturally occurring radioactive isotope contents. Hundred fifty coal samples originating mostly from eight different coal mines from Upper Silesian Coal Basin and 150 samples of ash obtained from these coal samples in laboratory by total combustion at final temperature of 820°C, were analyzed. Such comparitive analyses can be helpful in selection of most suitable kind of coal for burning in electrical power and heat plants to minimize the environmental pollution.     

Neutron activation analysis and natural radioactivity measurements of lignite and ashes from Megalopolis basin,Greece

Elemental concentrations and specific activity values of natural radionuclides were measured in lignite, bottom ash and fly ash samples collected from the Megalopolis power plant A in southern Greece, using nuclear analytical techniques. The results show that the elements As, Br, Mo, Sb, Se, and U were enriched in the lignite samples, the elements Mo, Se and U in bottom ash, while fly ash samples were enriched in As, Mo, Sb, Se and U. Specific activity measurements also show that ²³⁸U (²²⁶Ra) activity values in lignite and both ash samples were high relative to the corresponding data for coal and earth crust given in the literature. As a high quantity of fly ash is produced during the operation of the lignite power plant A, this power plant should be considered as a major source of air particulate pollution and radiation to the population living in the vicinity of lignite burning power plant.     

Distinguishing between natural and recarbonated calcite in oil shale ashes

Oil shale ashes from the PAMA demonstration power plant in the Negev region of Israel are produced by fluidized bed combustion (700–850°C) under short residence time. The FED is organic-rich calcareous raw material rich in carbonate rather than clays. Thus it is important to ascertain whether the calcite in the ashes is original natural calcite from the raw material or the product of recarbonation of lime. Three groups of ashes from the power plant, Ash Cooler (AC), Fly Ash (FAS) and Boiler Bank (BB) were examined using XRD, FT-IR, SEM and isotope analysis methods. The recarbonated calcite is distinguished from the natural original by smaller crystal size, lower degree of crystallinity and the presence of impurities. High negative δ¹³C values in oil shale ashes are explained by assuming recarbonation of lime with CO₂ originating from the combustion of the organic matter of the raw oil shale. Fly Ash, FAS, and BB, produced from organically-rich FED, contain more recarbonated calcite than bottom ash, AC. This observation can be explained by the larger grains of the AC, which do not reach the highest temperature area, and thus most of the original calcite does not decompose. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization and quantification of persistent organic pollutants in fly ash from coal fueled thermal power stations in India

The burning of pulverized coal to produce energy for generation of electricity in thermal power plants results in huge quantity of coal ash of varying properties. In India the coal based thermal power plants have been the major source of power generation in the past and would continue for decades to come. Because of the increase in electricity production, the amount of ash produced will increase proportionally. Very few studies on characterization of organic constituents in fly ash from Indian thermal power plants have been reported in the literature. In the present study, the fly ashes generated from five thermal power stations from different parts of India were investigated regarding the elaboration of distribution pattern of persistent organic pollutants (POPs) such as PAHs and PCBs in them. The PAHs in the fly ash samples were identified and quantified using high pressure liquid chromatography (HPLC-UV) whereas the estimation of PCB congeners was carried out using gas chromatography (GC-ECD). Lower molecular weight (MW) PAHs, were found to be predominant in fly ash samples. The concentration of Benzo(a)Pyrene which is the most potent carcinogenic PAH, varied between 0.82 ng/g and 18.14 ng/g with a mean concentration of 9.02 ng/g. Among the PCB congeners, CB-77 is having higher toxicity value, the concentrations of which in the fly ash samples were in the range of 4.58 ng/g to 104.98 ng/g with a mean value of 62.53 ng/g.