A review of the interference of carbon containing fly ash with air entrainment in concrete

Industrial utilization of fly ash from pulverized coal combustion plays an important role in environmentally clean and cost effective power generation. Today, the primary market for fly ash utilization is as pozzolanic additive in the production of concrete. However, the residual carbon in fly ash may interfere with air entraining admixtures (AEAs) added to enhance air entrainment in concrete in order to increase its workability and resistance toward freezing and thawing conditions. The problem has increased with implementation of low-_NOx${\mathrm{NO}}_x$ combustion technologies.     

A comparative study on field scale demonstration of fly ash and pond ash for cultivation of maize-groundnut crops in sequence on a wasteland

In India, the major source of energy is thermal power plants that contribute about 70% of the total energy requirement and produce a huge amount of fly ash per year. The fly ash and pond ash collected from the Ramagundam Super Thermal Power Station, India, were mixed with soil at different doses, 50, 100, and 200 t ha^?1 separately to compare their impact on crop yield and soil characteristics. Ash application had a beneficial effect on the crop yield, apart from reduction in the required doses of chemical fertilizers by half of the recommended doses. Addition of ash resulted in a significant increase in the contents of N, P, K, S, Ca, Mg, and micro-nutrients in maize and groundnut crop produce. The uptake of toxic trace elements (Cu, Zn, Mn, Fe, Pb, and Ni) was below the threshold levels. The residual effect of ash on crop yield and the nutrient composition of the subsequent maize and groundnut crops was also significant. The overall beneficial effect of ash could be attributed to the improvement in the soil. The results indicated that both the ashes could be applied safely for reclamation of uncultivated wastelands and pond ash is found to be better than the fly ash.     

Effect of wood fly ash and compost on nitrification and denitrification in agricultural soil

Wood ash from biofuel combustion plants and compost from source-separated household waste are commonly spread on forest, agricultural and horticultural soils as a valuable source of plant nutrients. However, due to anthropogenic activities, wood ash may contain high concentrations of heavy metals. Heavy metals are toxic to microorganisms and therefore, soil microbial response to wood ash should be considered when soil is amended with ash. Compost is known to improve soil structure and may also act as a bioremediating agent, mitigating any toxic effects of wood ash on soil microorganisms. In the present study, the aim was to investigate whether wood ash has any toxic effect on soil microbial activity and, if this is the case, whether compost could mitigate these effects. The effect of wood fly ash on potential ammonium oxidation rate (PAO) and potential denitrification rate (PDA) in arable soil was investigated in one dose–response assay and in two pot experiments with or without plants, respectively. The treatments were amendment with wood fly ash, compost or a combination of wood fly ash and compost. PAO and PDA were assessed immediately or after 7 and 90 days in the different experiments. Wood fly ash decreased PDA to 16–56% compared to the control, while PAO varied between 82% and 205%. Sole compost addition stimulated both processes. This positive effect was also observed in the combined wood fly ash–compost treatment. In conclusion, wood ash had a toxic effect on PDA, both on an immediate, short-term and long-term basis. Amendment of compost clearly mitigated this toxic effect. The observed toxicity could be an effect of the metal content of ash.     

垃圾焚烧飞灰资源化关键问题的探讨

随着垃圾焚烧工艺的广泛采用,焚烧飞灰产量越来越大,飞灰出路问题日趋紧迫。探讨了垃圾焚烧飞灰作为水泥原料的可行性,分析了由此带来并需要解决的重金属挥发、二恶英类有机物、氯元素导致水泥窑结皮和钢筋中毒等三大问题,最后介绍了目前国内飞灰作为水泥原料的应用情况。     

Mercury capture by native fly ash carbons in coal-fired power plants

The control of mercury in the air emissions from coal-fired power plants is an ongoing challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals.     

秸秆灰特性的研究

按照D1102-84灰分标准测定方法,对小麦、水稻、玉米、黄豆、高粱、棉花等几种秸秆样本进行了工业分析;在ZRC2000智能灰熔点测定仪上对不同秸秆进行了灰熔点测试;在不同的温度和停留时间下,在马弗炉上对不同秸秆进行了热灼烧试验.结果表明:秸秆挥发分含量较高,灰熔点比较低,无机碱金属析出量随着温度的升高和停留时间的增加而增加.     

Effect of fly ash and H2S on a Ni-based catalyst for the upgrading of a biomass-generated gas

The main concern about the technology for the production of hydrogen and transport fuels by biomass gasification is the presence of contaminants (H₂S, tars, fly ash, alkali, and heavy metals, ammonia) that are poisonous for the catalysts used for upgrading the biomass-generated gas. The impact of the main contaminants on a Ni/MgAl(O) reforming catalyst was studied in a laboratory environment, by exposing the studied sample to H₂S, NH₃, K₂SO₄, KCl, ZnCl₂, and a solution derived from biomass fly ash. Lastly, the catalyst was also streamed with a gas produced by a bench-scale downdraft gasifier. The extent of deactivation was examined in the methane steam reforming reaction, under different operational conditions. The main effect of the treatments was a decrease in the bulk surface area and in the metal dispersion. Streaming H₂S quickly deactivated the catalyst; however, the activity was recovered by increasing the inlet temperature or by adding O₂ to the stream. In further laboratory tests, the performances of the catalyst seemed not to be greatly affected by either the above treatments or by the presence of ammonia in the fed water. The catalyst produced a syngas composition close to that predicted at equilibrium even after being streamed with the biomass-generated gas.     

A new graphene bottom ash geopolymeric composite for photocatalytic H2 production and degradation of dyeing wastewater

A novel Mn²⁺-doped and CuO loaded graphene bottom ash-based geopolymeric (Mn²⁺-CuO/GBAG) composite was firstly synthesized by a four-step experiment of alkaline activated geopolymerization, ion exchange, co-impregnation and calcinations. The composite was employed as the photocatalyst for production of hydrogen by solar photo-reduction and degradation of dye by photo-oxidation. XRD, XPS and N₂ adsorption-desorption equilibrium isotherms results revealed that Mn²⁺ ions implant into the lattice of CuO, and the CuO in the form of tenorite with average particle size of about 20 nm dispersed on the surface or inserted micro and mesoporous channels. The Mn²⁺-15CuO/GBAG composite exhibited the highest H₂ yield of 2853.7 μmol g^?1. It was found that the activity of photocatalytic reduction for hydrogen production was proportional to the contents of the Mn²⁺ doping and CuO loading, and inverse proportional to the intensity of photoluminescence due to the enhancement of separation efficiency of photogenerated electron–hole pairs. The Mn²⁺-15CuO/GBAG composite showed the highest photocatalytic degradation activity of 100% for direct sky blue 5B dye, and the degradation reaction fitted the first-order kinetics. A probable mechanism of photocatalytic reduction and oxidation was proposed in the paper.     

电热式熔融固化垃圾焚烧飞灰的实验研究

对高温管式炉熔融固化垃圾焚烧飞灰的处理效果进行了实验研究.进一步考察了浸出环境对飞灰固化效果的影响.结果表明,根据国家的浸出标准,飞灰熔融固化后就不再是具有浸出毒性的危险废物.酸性（pH≤4.5）和碱性（pH≥1.5）环境对固化效果的影响比较大;潮湿的环境（L/S≤100）对固化效果无明显影响.     

防渗材料对粉煤灰析出物吸附特性研究

采用标准测定方法 ,通过吸附动力学试验、静态吸附试验测定两种防渗材料 :黄土状亚粘土和石灰改性粘土对粉煤灰浸出液中主要污染组分的吸附特性 ,结果表明 :后者对污染物的吸附比前者好     

Flotation kinetics of the removal of unburned carbon from coal fly ash

Unburned carbon (UC) in coal fly ash indicates the waste of energy source and is an obstacle to the utilization of coal fly ash. The purpose of this study was to investigate the flotation kinetics of the removal of UC from coal fly ash. The collector and frother dosage are key factors for coal fly ash flotation. Six flotation kinetic models were applied to fit the flotation kinetic tests data. The fitted results showed that the classical first-order model had better consistency with the experimental data. The contact angle of flotation concentrates decreased as the flotation time was extended which revealed the decrease of flotation rate.     

350MW超临界机组锅炉飞灰含碳量高原因分析及治理

针对某厂350MW超临界机组存在飞灰含碳量高问题,通过对制粉系统、脱硝系统以及配风方式等进行了优化调整,使得飞灰含碳量有了明显降低,再热减温水得以控制,同时弄清楚机组存在的问题,为下一步进行技术改造提供依据。     

降低流化床水煤气炉飞灰含碳量的方法与实验研究

介绍了降低流化床水煤气飞灰含碳量的方法及实验研究结果。实验研究包括在现场进行的飞灰停留时间的冷态实验以及在实验室进行的飞灰反应性的实验。     

粉煤灰筑坝技术

结合秦岭电厂二灰场应急改造工程施工实践，介绍了在软弱沉积灰基上填筑粉煤灰坝的施工特点和施工方法以及工程质量控制措施，对同类工程施工有重要参考价值，为研究和发展粉煤灰筑坝技术提供参考资料。     

循环流化床锅炉脱硫飞灰的水活化实验研究

以310 t/h循环流化床锅炉脱硫飞灰为原料,在不同的水活化条件下进行活化机理的实验研究,探讨了水活化温度、活化时间、活化水量对灰中游离氧化钙水合反应转化率的影响规律,并研究了水活化对孔隙结构的影响。结果表明:水活化过程中,水合反应与消耗氢氧化钙的胶凝反应同时进行;水活化过程中氢氧化钙含量呈现快速上升、慢速上升、缓慢下降的规律;随活化温度提高,水合反应与胶凝反应速率均提高,中期持续时间缩短,活化时间一定时,活化温度存在最佳值;活化水量的增加,可以加快水合反应与胶凝反应速率,活化时间处于后期时,活化水量存在最佳值。     

Comparative studies on fly ash coated low heat rejection diesel engine on performance and emission characteristics fueled by rice bran and pongamia methyl ester and their blend with diesel

In this study, for the first time, fly ash was used as a thermal barrier coating material in a diesel engine. The study consists of three phases. In first phase, biodiesel was prepared in a laboratory scale setup by single step base catalyzed transesterification method. In the second phase, engine combustion chamber elements such as cylinder head, cylinder liner, valves and piston crown face were coated with fly ash, which is a thermal power plant waste, to a thickness of 200 μm by using plasma spray coating method. In third phase, experiments were carried out on fly ash coated single cylinder diesel engine fueled by methyl ester of rice bran, pongamia oil and its blend (20% by volume) with diesel. The test run was repeated on uncoated engine under the same running conditions and the results were compared. An increase in engine power and decrease in specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx) were observed for all test fuels used in the fly ash coated engine compared with that of the uncoated engine.     

危险废物焚烧飞灰熔融处理过程重金属行为的研究

对危险废物焚烧飞灰的成分进行了分析,测定了典型重金属成分的含量和浸出毒性。在自行设计的小型电热式熔融炉上进行飞灰的熔融实验,着重对熔融过程中重金属的固化机理及熔渣的浸出特性进行了分析。结果表明,添加CaO能普遍提高重金属的固定率,而添加SiO2后易挥发重金属的固定率提高明显。同时,惰性气氛能显著改善重金属的固化效果。经过1400℃高温处理后的熔渣不具有浸出毒性,具备安全填埋的条件。     

飞灰复燃对炉内颗粒沉积状况的影响分析

实际工程表明,采用飞灰复燃技术对锅炉进行改造,可以减少飞灰所带走的燃料损失,提高锅炉效率,但飞灰回收复燃给壁面颗粒沉积状况也带来了影响.采用FLUENT模拟了SZL15-1.25-AⅡ型双筒链条蒸汽锅炉炉内燃烧,对比分析了采用飞灰复燃技术前后炉内壁面颗粒沉积状况.模拟结果表明,飞灰复燃对锅炉顶墙、前墙及后墙的颗粒沉积速率影响较大,其中飞灰复燃提高了顶墙和前墙的颗粒沉积速率,降低了后墙颗粒沉积速率,而对锅炉前后拱的影响很小可以忽略.减小飞灰入射质量流量或调整飞灰入射角度为水平偏下,均可以降低颗粒在水冷壁的沉积速率,有利于炉膛与水冷壁间的传热.     

MMT对煤燃烧飞灰含碳量和NOx排放的影响

在一维沉降炉上对神混l号煤样添加MMT后燃烧的飞灰含碳量和NOx排放特性进行了试验研究,并对其燃尽率进行了分析.试验结果表明:所用沉降炉设计合理,添加MMT后,煤燃烧的飞灰含碳量和NOx排放同时降低.与原煤相比,最大降低量分别为18.39％和14.29％.原因是MMT的含锰燃烧产物能够促进C的氧化,同时还能作为催化剂促...     

Effects of calcium chloride and sodium chloride on the flotation removal of unburned carbon from coal fly ash

The effects of calcium chloride and sodium chloride on the coal fly ash flotation were investigated by studying the surface properties of coal fly ash. X-ray photoelectron spectroscopy and scanning electron microscopy showed the presence of many lime particles in the coal fly ash, which, together with Ca(OH)₂(s), could be adsorbed on the rough surface of unburned carbon particles. The flotation results indicated that calcium chloride reduced the performance of unburned carbon removal from the coal fly ash, whereas sodium chloride increased froth stability thereby improving the flotation performance.